Categories
boats

Choosing the right folding/feathering prop

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A shot of the Kiwiprop feathered under sail. Taken with the GoPro Hero camera

If you have a sailing boat one of the best things you can do to make it go better is to fit a feathering or folding prop which causes much less drag when you are sailing. If you’ve ever stuck your hand in the water when moving along, you’ll know that a lot of drag is produced. Imagine now that three bladed fixed prop is like having three hands in the water dragging all the time. At high speeds the effect is reduced by brute force but at low speeds the drag of a prop can make the difference between sailing or having to fire up the ‘iron topsail’.

A simple way to reduce drag on yachts is to fit a two bladed prop. It’s a simple and cost effective solution but by reducing drag, you reduce area and this makes the boat much harder to stop and may mean that you are unable to power into a rough head sea when you need to. Two bladed props can also cause vibration as the blades pass the deadwood of the hull. If you have a fin keeled yacht with a prop sticking out all on its own a two bladed prop will work much better but it is still a compromise.

‘Doolittle’ my Dana 24 was fitted with a 15” two bladed prop from new and it worked fine it just couldn’t stop the boat very well. Even full revs failed to do the trick. It seems there is no substitute for blade area. It was clear that a more efficient prop was called for so I began looking into feathering and folding props.

A folding prop is one whose blades swing out when motoring but fold like a closing flower when sailing. A feathering prop is one whose blades do not fold but rotate around an axis from one direction to another. Each design has it’s good and bad points but you may find like I did that the extra length of a folding prop just isn’t an option if you have a propeller aperture or a rudder just behind the prop.

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Having a prop aperture limits choices and can cause problems

So this is the first question you need to ask when considering buying a new prop. There are an awful lot of folding and feathering props out there so being able to narrow the choice is actually very helpful.

Each design has compromises and will do certain things better than others. Some may work better motoring than others but they may have more drag under sail as a consequence so it’s important to decide what features matter to you. Here are a few examples of what might matter:

Prop walk I don’t know why, but many sailors deem this to be an undesirable feature in a propeller but personally I like prop walk. I find it helps when manoeuvring. What is prop walk? Imagine that the boat is stationary in still water (no current) and there is no wind blowing. There are no external forces acting on the boat so it will remain in place. When you go into astern and accelerate, your boat will move backwards but it will also move to port or to starboard depending on the direction of the prop (determined by the gearbox). Prop walk is caused by a number of things but blade shape, pitch and hull shape are the main reasons. Many prop makers claim reduced prop walk with their props but this can be misleading as the shape of your hull and the position of the prop may well mean that you will still have prop walk.

As I said, I like prop walk but if you don’t there are ways to reduce it. For example, accelerating gently with less revs and letting boat speed build slowly will reduce prop walk considerably. If you want more prop walk, gun the engine when the boat has no way on it and you will clearly see the effect as the whole boat steps sideways. The fact that a prop is claimed to reduce prop walk is of no interest to me. Remember that every ‘plus’ point is achieved at the loss of another.

Power astern

One of the reasons why fixed props do not perform well in astern is because the blade shape is only optimised in one direction. If you look at a fixed propeller blade you will see that the angle of the leading edge changes from being at quite an angle at the base of the prop to a very fine angle at the tips. This is because the blades spin faster at the tips than at the base. You can see this in most propeller blades , including wind generators and wind mills.

So fixed blades work well when going forwards as the leading edge angle is optimised so that it attacks the water all along it without stalling or cavitating but the opposite is true when the blade spins in the other direction. There’s a lot to be said for a fixed blade prop. They can work efficiently when motoring forwards and they are simple with no moving parts to go wrong. They need no greasing or maintenance just an anode change every year.

Folding and feathering props have blades which work equally well in forwards and astern. They do this by compromising on the shape and therefore efficiency of the blade. generally they have blades which are much flatter. A flatter blade will cause less drag when sailing too. They generally work better in astern than fixed props because the blade shape, although compromised, is still better than an optimised blade working badly backwards.

Many companies make two bladed feathering and folding props but for real stopping power you need three blades. I confess I don’t really see the point of these props. They must have less drag when sailing but not much more than a three blader since the blades all rotate to offer the least resistance anyway. These props must be for the most serious of sailors who care more about reducing drag when sailing than anything else.

Noise and vibration

What kind of prop and shaft installation do you have? If you have a propeller aperture then you are likely to have all sorts of problems from finding a prop that will physically fit in the space (and fold or feather even with the rudder hard over) to prop walk and noise and vibration generated by the shape of the hull.

The most likely noise you will hear is from cavitation which (very simply put) is bubbles created by the prop. Click here to read more about cavitation. It sounds like bubbling and hissing. Often feathering or folding props cavitate initially but as the boat speed increases the cavitation will drop off.

There’s not much you can do to stop this. You can try a finer pitch on the blades and you can ensure that the blade tips are as far away as possible from the hull but if that doesn’t work you might have to consider a different propeller. I had this issue with the Kiwiprop and in the end decided to change for something more substantial. You can read my review of the Variprop 4 blade feathering prop here

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This shot clearly shows a ring of unwanted cavitation around the prop. This cavitation creates a lot of unpleasant noise. Taken with a GoPro HD Hero camera

Vibration will probably come from the fact that the blades must pass behind the deadwood of the hull on every revolution. Props work best when they have clean water to turn in. If you have a propeller aperture then your prop will be working in turbulent water for much of the time. The more blades you have the better.

As folding and feathering props wear with age, there will be more play in the blades and so they are likely to make noise or cause vibration.

Performance under sail

No feathering or folding prop offers zero drag but they do reduce it considerably, some more than others. The folding props probably offer the least resistance as the blades fold like a closed flower and are thus more hydrodynamic than the other types. Also the folding mechanism is simpler and generally the hub is much smaller than feathering props.

One factor not often recognised when considering drag is the angle of the propshaft. Because most feathering props have their blades linked it means that not all the blades can fully feather at the same time. In the real world this is not much drag but it helps to understand all the same. Most engines are installed at a slight angle so it’s worth bearing this in mind.

The exception to this rule are saildrives which are generally mounted straight but they require a different prop mounting and not all the makers offer a prop for saildrives.

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A 3 blade Variprop German feathering prop mounted on a saildrive leg. Looks like a nice piece of engineering.

In any case if you are coming from a fixed three bladed prop, the reduction of drag under sail is massively improved regardless of the folding or feathering prop you choose.

With a feathering or folding prop you will find that you can sail in light airs whereas before you could not. Just not having that drag means that the boat carries its way better and can build up speed much easier. When I had the fixed two bladed prop I was unable to sail to windward in light airs against a choppy sea. The feathering prop made it possible to do this. The boat would still pitch but the way was not lost.

Performance under engine

For performance under engine you need blade area. Three blades are better than two. Even three compromised blades are better than two optimised blades so most folding and feathering props will offer superior performance over a two blade fixed prop simply because there is more blade area. If you are coming from a fixed three blader the difference may not be so great.

Most folding props cannot be adjusted easily for pitch. It is possible but it will probably have to be returned to the maker to be done. The advantage of most feathering props is that the pitch can be adjusted fairly easily. This means that you can adjust it to suit your boat.

When a propeller is supplied for your boat, the maker will do calculations based on the hp of the engine, the reduction ratio of your gear box, the length of the boat and the space available for the prop. They will aim to get your boat moving at hull speed at maximum revs.

This is a compromise situation. Often an engine warranty will insist that any prop fitted must allow the engine to reach maximum working revs. This is so that the engine is not overloaded. An overloaded engine is a very bad thing. Unburned fuel will be washing oil from the bores and the engine will wear very quickly.

Also the black soot that comes out of the exhaust will pollute the sea and cover the back of your boat in black grime which is very hard to remove. It will clog up your exhaust and further reduce engine efficiency and reliability.

However the question remains, do you want to run your engine at high revs when you are cruising? Personally I do not. I would much rather have lower revs for the same boat speed as it makes the voyage much more pleasant and you will use much less fuel and increase your range.

This is why it is good to have adjustable pitch. It means that you can obtain cruising speed at lower engine revs by increasing the pitch on the prop. The down side is that you will not be able to reach maximum revs and if you try you will be overloading the engine.

The Dana 24 has a hull speed of about 6.5 knots but it needs a lot of power to do this as it’s a heavy boat. It is much easier to push along at about 5 knots which is a perfectly respectable cruising speed allowing 120 miles a day. By adjusting the pitch I can get the boat to do 5 knots with only 2200 rpm. It no longer revs to 3600 rpm but will get to 3400 rpm so it’s not far off the original.

This allows quieter motoring as I am using less revs and much better fuel consumption. After every 24 hours of motoring I run the engine at full power for half an hour to blast out any soot that might have built up due to running the engine at lower revs.

There are some who adjust the pitch right down to get a good cruising speed at much lower revs. The beauty of an adjustable pitch prop is that you can experiment until you find a setting that you like.

Easy pitch adjustment

Most feathering props offer a way of adjusting the pitch but not many allow easy adjustment with the boat in the water. Since the adjustment of the pitch is so critical I consider this a very important feature in a prop. I want to be able to dive down with an Allen key and easily and quickly adjust the pitch.

The Kiwiprop has adjustable pitch but each blade is adjusted independently which so great care must be taken to do them all the same. If the blades come out of adjustment you will invite noise and vibration. It cannot be adjusted in astern and has a fixed pitch which is very course and has caused problems with lower powered engines.

The ideal prop has a simple ‘one screw’ indefinite adjustment for all the blades in both forwards and astern.

Rope catching

A feathered prop is less likely to pick up a lobster pot or a rope but with a stowed folding prop it’s almost impossible as the rope will simply slide along it. If you sail in an area of fishing buoys or lobster pots maybe this is a very strong argument for having a folding prop if you can fit one.

Ease of fitting

This isn’t a deal breaker for me if the prop has to be assembled in place as it’s only done once and then forgotten but luckily many props are designed to simply slide onto to the old tapered shaft. What you may find is that the shaft will need to be cut down as often feathering props’ hubs are longer.

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Variprop 4 blade prop in a very small aperture. Owner claims it works beautifully.

Rarely is fitting a new prop straightforward, especially if you have a prop aperture as space will be seriously limited. Check that the blades cannot touch the rudder when it is hard over.

Ease and cost of maintenance

Most feathering props need lubrication of some sort but many folding props do not. Again, this is not a deal breaker if the boat has to come out of the water to allow the prop to be maintained and greased because most people take their boats out of the water every year anyway.

Almost all props need an anode to protect them against electrolysis. Mostly they are custom made and therefore costly. The problem with most is that they corrode around the screw holes, the screws then come loose and the anode can start rattling about making noise or worse, it can fall off and then your expensive prop is no longer protected from corrosion.

The better prop makers solve this issue by fitting stainless sleeves to the anodes but of course this adds cost and it probably means you’ll have to buy the maker’s own brand which won’t be cheap.

Materials

Most props are made from bronze but the Kiwiprop is made of stainless steel and in theory does not need an anode but if you have a problem somewhere it may cause the prop to corrode. Often marinas have large anodes fitted to the pilings and they can cause havoc with metals under the water line. Sometimes a neighbouring boat can cause problems. Far better to fit an anode just in case. The Kiwiprop does not have an option to fit an anode.

The Kiwiprop has plastic blades which cannot corrode and have the added advantage of being able to be painted with antifouling. You can of course paint any blade but paint does not stick well to metals.

The Australian Autostream prop is made entirely of stainless steel which is stronger than bronze and allows thinner lighter blades. Most other props are made of bronze.

Guarantee

Most offer a year but the more serious props like the Variprop offer 5 years so if this is important to you it might make a difference to the prop you ultimately choose

As far as I know only Maxprop will allow you to try a prop and take it back if you don’t like it.

Making a choice

This is very hard. I chose the Kiwiprop because I liked the idea of adjustable pitch. The plastic blades can be antifouled and unlike metal blades the paint stays on so the prop doesn’t foul during the season. A fouled prop will destroy motoring and sailing performance while increasing dramatically fuel consumption so this was important. It was well priced too which was useful.

Sadly it was noisy and nothing I did made a difference. After the guarantee had run out I began having problems with it going into astern. The solution was to buy a new set of blades for $600.

I liked the idea of less weight too but in the end it was not reliable and couldn’t be trusted to go into astern when needed although it worked well under sail.

Since this disappointing experience I have taken a closer look at the enormous choice of props out there. The Dana has a prop aperture and a long keel so this rules out all the folding props.

I spoke to Bruntons about their Autoprop which is a very clever design with three self pitching blades. I cannot for the life of me see how it works but owners seem happy although I have heard a few stories about boats that cannot motor into a sea when it’s rough. The problem I have is that the pitch would change every time it passes the deadwood so the blades would be madly oscillating all the time. This would, according to Bruntons cause the prop to be noisy so that was ruled out.

The Maxprop was the obvious next choice. A well proven bronze prop made in Italy. Latest models have external pitch adjustment which is a great improvement. I have taken a look at lots of old Maxprops on boats in boatyards and many seem to have a lot of play when they get older. The worst is that many Dana owners have reported some cavitation noise at lower revs. Normally this wouldn’t be a problem but it’s not unknown for us to do the occasional canal trip and when there is a 3 knot speed limit you will need to use low revs. I know from the Kiwiprop how annoying this is when you are motoring all day.

It is important for me that a prop is quiet and smooth. I have gone to a lot of effort with flexible couplings and soundproofing to ensure that my engine installation is as smooth as possible but it is all for nothing if the prop causes noise and vibration. It is also important that it goes into reverse when I need it to.

I think I have found the prop I need. Unfortunately it is also the most expensive one on the market. Typical. It’s the 4 bladed Variprop. It has a lot going for it. Because it has 4 blades it is likely to be much smoother. Because it has so much blade area, overall diameter can be reduced ensuring that the tips of the blades are well away from the hull. This too should help reduce cavitation noise.

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One lucky owner with his new 4 blade Variprop. The bottom of the blades are nicely rounded off so this should help to keep cavitation down. The Maxprop has very sharp bottoms to the blades, I wonder if this makes any difference? Surely the smoother the better…

It’s made of bronze and comes with a 5 year guarantee. This is a serious prop. The only one approved by Yanmar for their saildrives. It is made in Germany so must be quality. Each blade is carefully balanced and adjusted for maximum smoothness.

There’s more. Pitch is adjustable in the finest degree in forwards and astern with just one screw. The blades are linked so they will always be perfectly aligned no matter what pitch you set. There’s even a built in shock absorber that takes up the shock of going from forwards to astern.

By having 4 blades, the load on each is reduced which means a longer life. The blades have a large area to rest on and the oversized gears are simply to hold the blades in alignment, there is no force on them. The Variprop also sports the smallest hub going so should be easy to fit. The prop fits straight onto to the existing taper on the shaft so should take minutes to fit.

Here is a prop that has been very well conceived and produced. The marine environment is a brutal place and I have learned that if you want trouble free use it must be up to it. The Variprop has been designed so that even when it is old and worn out it will still work as intended unlike the Kiwiprop which doesn’t.

Conclusion

If I had to choose three traits that I want from a feathering or folding prop they would be:

Build quality, guarantee and after sales service,

Easy and infinite adjustable pitch in forward and astern,

Four blades for minimum noise and vibration

Most props seem to offer massive improvements over fixed props so I have not listed performance or drag under sail as important working on the assumption that I have a cruising boat, not a racing boat and most of these props offer very similar performance under sail and motor.

Having learned the hard way I now want smooth and quiet with reliability and it looks like the Variprop is the only prop that is likely to supply what I need. Yes, it’s expensive but so is a Kiwiprop if I have to buy new blades for it every few years!

The old adage that you really do get what you pay for really does seem to apply to feathering and folding props.

Here is a really excellent article written by Yachting Monthly which tests most of the props on the market. It also explains a lot of stuff in detail. Well worth a read.

Categories
boats

Kiwiprop feathering propeller long term review

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What a fabulous idea. A feathering prop with plastic blades. Makes a lot of sense really. The most obvious advantages are less weight and no electrolysis but it also means that the blades can be painted with antifouling, something that can’t be done effectively with metal blades. You can paint them of course but the paint never stays on for long and once there’s growth on the blades, the prop becomes hideously ineffective but paint does stay on the Kiwiprop’s plastic blades so they stay clean all season.

Each blade is made of a special plastic and is mounted independently from the others. This is where the Kiwiprop differs from most other feathering or folding props. The advantage of this system is that each blade is free to follow the path of least resistance when in ‘sailing’ mode. Other feathering props like the Max prop for example, have blades that are linked to one another and because most marine engines are installed at a bit of an angle, there’s always at least one blade causing some drag.

Another advantage of the Kiwiprop is that the pitch can be adjusted easily, even with the boat in the water. Each blade has a small Allen key bolt. Simply turn each bolt half a turn to change the pitch by a degree and a half. Most other props require dismantling if you want to change the pitch. However the Kiwiprop has no adjustment for pitch in astern.

The Kiwiprop is made for boats with engines from 15 to 55 hp. It has a central hub made of stainless steel and because there are no dissimilar metals in it’s construction it means that no anode need is fitted.

Enough of the technical stuff. Fitting was straight forward with the prop using the existing taper on the shaft. The pitch was preset at the factory to match my engine and gearbox. My Dana 24 was originally fitted with a fixed two blade prop which worked fine in forwards but lacked bite in astern. This made manoeuvring in port on windy days a lottery. In theory the Kiwiprop would perform better when motoring and sailing.

Under power the Kiwiprop has bite. The boat accelerates well, especially considering that it weighs over 4 tons but what is most impressive is that way it stops. Slam it into astern and the boat stops from 5 knots in it’s own length. If you’re not holding on, the sudden deceleration will knock you down. A massive improvement on the old two blader.

The Kiwiprop has made also made a big difference to the boat’s sailing performance. In light airs with a bit of a chop the Dana now sails through it. Before with the drag of the prop it would be enough to stop the boat’s progress. The boat’s wake is cleaner too. The difference is quite noticeable. If you were coming from a 3 blade fixed prop you will really feel the difference

 

Where’s the catch?

Now for the not so good stuff. Right from the start the Kiwiprop made a lot of noise at lower revs. At 2000 rpm the prop was very noisy. If I upped the revs to about 2500 it went quiet but perhaps I just couldn’t hear it over the increased noise of the engine.

So I tried a finer and courser pitch. Sadly it didn’t make any difference to the cavitation noise. It is something I have to live with apparently. Strangely, a mate has a Kiwiprop on his steel boat and it is absolutely silent which tends to suggest that it’s more to do with the hull shape of my boat and prop aperture than the prop itself although it must be said that the original 2 blader didn’t make any noise!

On a recent canal trip this problem was really intrusive. As there is a 3 knot speed limit it means running the engine at well below 2000 rpm and at that speed the prop makes a right old noise. Obviously I have been in touch with Kiwiprop in New Zealand but apart from suggesting changing the pitch and higher revs for the prop they have not been much help.

Feathering props are said to reduce prop walk but the Kiwiprop still has a healthy kick to port but this may be more to do with the shape of the hull than the prop itself. In a recent test of folding and feathering props done by Yachting Monthly, the Kiwiprop came out about average for propwalk.

Then after just a year the prop started to become difficult to get into astern. The blades were not engaging properly and the extreme pitch was so much that the engine could not pick up. The only way to make it work was to go direct from forwards to astern which as you can imagine is a right pain.

Many emails have passed between me and Kiwiprop in an attempt to get to the bottom of this. Everything has been tried, from upping the tickover,  changing the gearbox oil to checking the exhaust is not blocked but all to no avail. Eventually I was told that the reason why it won’t work properly is most probably that the base of the blades are scored from where they run against the rollers. Every year I have checked the prop and every year the three rollers are all loose and it is this, I believe, which has scored the blades.

So I am glad that we have at last discovered the reason why the prop won’t go into astern but knowing why does not help much. It would seem that the problem can be cured by a nice set of new blades. With duty and shipping it comes to about $600. Even if I were to change the blades, I can see no reason why it won’t happen again.

Conclusion:

I am disappointed in the clattering cavitation noise the prop makes, clearly audible over the noise of the engine and I am annoyed that I have to buy new blades for it so soon.

The prop cost about 1200 Euro which as feathering props go is a very good price but if the blades need replacing every few years then perhaps it’s not such good value after all.

The bolts that hold the rollers on the latest versions of the Kiwiprop are apparently now held more firmly in place using a punch and a hammer to crush the threads slightly but this seems to me a crude way to solve an engineering problem.

Doing research online I discovered that I am not alone with these problems. There are many references to loose or even missing bolts, reversing problems and even the odd missing blade!

In my opinion the Kiwiprop just isn’t robust enough for the marine environment, it has far too many issues and simply can’t be trusted to work when needed. It was worth a try because the advantages seemed many but at the end of the day reliability is far more important to me.

Like most technology, fabulous when it works but hopeless when it doesn’t. Having a 4 ton boat that won’t stop is a worrying and potentially dangerous situation. It’s hard enough trying to manoeuvre in most marinas these days without wondering if the prop will engage before you smash into a big power boat.

It’s true that we probably do much more motoring than most being in the Med and often away for months at a time but I did not expect problems after just a year of use no matter how many hours I used it for. It will be interesting to see what happens to those 4000 props out there once they have as many hours on them as I have on mine.

Overall a disappointment.

UPDATE: June 2011

Kiwiprop finally sent me a set of slightly larger blades and a set of new rollers (free of charge) in an attempt to solve the noise and ensure that it engages astern every time.

The blades are just half an inch larger in diameter which is not very much and this takes their tips to within a quarter of an inch of the hull. The idea is that the larger blades will need a finer pitch to work. The finer the pitch, the less chance of cavitation noise.

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New 16.5” blades. It leaves the tips very close to the hull aperture but these bigger blades make this prop much quieter and smoother than before.

The rollers are now pentagon shaped. This will hopefully make them more inclined to rotate even if they are a little seized up by marine growth unlike the original round ones which seized up quickly. This didn’t stop the prop from working but it’s my belief that it contributed to the excess of wear on the bottom of the blades which then led to the prop not engaging astern correctly.

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New Pentagonal blade rollers. This should keep them turning all season and in theory do less damage to the base of the blades where they touch.

The prop is still a bit clattery at low revs but is massively improved after that. At 2000 rpm the prop still has a little cavitation noise but it is slight and certainly not half as annoying and intrusive as it was before. By 2200 the prop makes no noise at all. This is great news as 2200 is a good amount of revs for the engine. Just enough to get it working but not so much that it is too noisy or uses an excessive amount of fuel.

Now at 2200 rpm the boat can manage almost 5.5 knots which is truly excellent. Even at lower revs the prop works well but makes some noise. As far as I am concerned, so long as the prop is quiet at cruising revs I can live with some slight noise at lower revs. There has to be compromise somewhere after all.

With new blades and rollers, the engine now engages astern perfectly but then it used to when it was new too. So this post will need to be updated regularly to report on whether the new pentagonal rollers are working. Will they wear a similar groove in the base of the blades? If so will that groove affect the prop going into astern? In theory, with the pentagonal rollers always able to turn, it shouldn’t matter if the blades do get scoured. In any case I’ll keep you posted.

Many thanks to John at Kiwiprops who came through in the end.

Update Jan 2012

The new blades have certainly reduced cavitation noise but the old problem of not going properly into astern is back after just a few months. I wrote to Kiwiprop who told me that it is a question of spring tension. So now I have to take the unit apart again to sort it out. There have been a few comments on this post recently that point at poor reliability and frankly I am not impressed.

The conclusion that I have now come to is that the Kiwiprop is not for me. I want something that simply works. I can no longer trust the Kiwiprop to go into astern and once I have lost faith and confidence in a product it has to go.

Update Jun 2012

When I hauled the boat I discovered that all three rollers were loose again. Lucky they didn’t fall out.

This is just a final confirmation for me that the Kiwiprop is likely to fail at some point so I have now removed it and replaced it with a Variprop 4 blade bronze prop. You can read about it here. It’s expensive, almost twice the price of the Kiwiprop but it’s what I should have bought in the first place. I never seem to learn that you generally get what you pay for in life. It’s a shame as the Kiwiprop has a lot going for it and the company are constantly improving the design but from what I have experienced it just doesn’t offer the kind of reliability I look for in a propeller.

Update Feb 2021

I just received the following from John at Kiwi Prop. They are constantly updating and improving their design and he asked that I add the following to this post, so here it is!

It is now some years since an update was made to this website and in the intervening period Kiwiprops has continue to prosper and now has an installed base of some 8,000 units in virtually every country dating back to 1998.

We maintain a database with a build record of every installation and thus able to monitor ongoing performance and functionality issues.

Today we have over 65,000 propeller years of units in service and consequently over 200,000  blade / reverse screw  years of service upon which to analyze and generate feedback and modifications.

Rather than dramatic design changes to the unit we have operated a continuous improvement program with successive small changes that have been that have been rigorously tested to the extent that is possible.

We have also adopted a design constraint making all components backward compatible with all previous units.

Marine engines come with a whole host of power ranges, maximum engine rpm capability and in addition a wide range of reduction options which are not always the same in ahead and astern. In fact this variation is the norm and one needs to recognize that a Yanmar shaft installation for example with say 2.2:1 reduction in ahead, like all small Yanmar’s will have a reduction ratio of 3.0:1 in reverse.

Another variable on marine engines is the type of clutch they employ which leads to very differing engagement speeds with consequent differences in the force involved with the reverse rollers contacting the blade root surface. At one extreme we have the dog clutch of the Yanmar SD 20 Saildrive which is not actually a clutch at all as it is either fully in a fully out and leads to huge shock loads on the Propeller during Reverse’s engagement.

Many smaller gearboxes today will have what is termed a cone clutch, consisting of a bronze cone into a metal cup and energized by mounting on a spiral spline so that as torque increases, the force on the bronze cone into the cup also increases. These can present difficulties getting them back into neutral with high idle speed, or any glazing of the surfaces of the cone.

Virtually all manufacturers today are phasing out cone clutches and reverting to the normal multipack clutch which has a much smoother engagement and no difficulty engaging neutral. The loading forces on a blade root with these clutches are much lower and lead to significantly lower wear rates.

Today  – Saildrive’s comprise in excess of half the market under about 80 hp and more so in new build production vessels. Yet all Saildrive’s driven by the nature of their drivetrain will have exactly the same reduction ratio in ahead and a stern.

While it is not possible to optimize a particular propeller design for all these very varying constraints, it is important to recognize they exist and make appropriate trade-offs including economic to provide what one considers as an optimal solution.

An optimal solution for sailing vessel will generally attach equal weight to motor and capability and the reduce drag from the feathering function when sailing.

The improvements undertaken over the years can be summarized as follows:

In every instance these changes have been very well documented on our extensive website: www.kiwiprops.co.nz

A full database search function on the top right hand corner of our homepage will bring up the information on any keyword entered.

A switch to 50 % glass content blades.

Post mid 2009 we became aware of the existence of a new blade material:

DuPont™    Zytel® HTN53G50HSLR NC010

In simple chemistry terms this constituted a long chain molecule, rather than the previous 35 % glass product we were using which was an aromatic or ring molecule.

The great advantages of this new product were contained 50% glass fibre by weight, was impervious to both hydrocarbons and water meaning it was stable over a very long time frames when immersed. It also of course had much higher strength and stiffness but retaining the obvious zero corrosion potential of the previous product.

The trade-off was a much higher moulding temperature which influenced production and die cooling and of course came at a significantly higher price. It also required a switch to carbide tipped tooling due to the highly abrasive nature with the high glass content in the material.

The development of ogival foiled blades:

The increased strength of the new material allowed for thinner blades which has two benefits – they will generally be more efficient and can in principle be made quieter. This was a comment from above but caution is appropriate as in any aperture situation, particularly on this type of vessel with a very broad keel, it is always going to be a challenge when the propeller blades simply are not going to see continuous smooth streamlines entering the unit.

To retain design flexibility and minimize stockholdings as well as very expensive die costs,

we elected to maintain the existing symmetric foil shape which allows for both left and right hand rotation and then mill off either side of the blade in jig  so that in simple terms it more closely resembles a traditional Propeller with a flat face aft and an ogival foil on the forward face. This has been determined over many years as optimal for motoring functionality – but of course we were restricted as more removal would have a negative affect on feathering stability.

We conducted extensive testing on this new foil shape using a friends catamaran fitted with both and old and new foil on each side this negating any variation from hull condition, currently loading and sea state.

Results for this trial are on our website under Ogival Foils.

In addition – we had a very helpful engineer who had had a Kiwiprop and was motoring the inland waterway from New York to Florida and return. His considered feedback and analysis with a popular 3GM30 on 2.61:1 – which we do value – was that the new ogival foils delivered between 0.3 and 0.5 knots additional motoring speed over the course of that voyage at the same engine rpm.

This information has been replicated on many situations now and we are very confident that the foil shapes we are using are both optimal for motoring, yet retain adequate strength with a high margin of safety and the shape change has not affected feathering functionality.

There is a very extensive analysis of the testing and design undertaken using computational fluid design (CFD) beginning with the profile of the actual blade die shape and progressing to illustrating the effect of this particular shape and ogival modification on power and thrust. Actual vessel speed versus derived agreed to within 5%. This is all available on our website under Ogival Foils. CFD will deliver the results from a particular foil shape under analysis – it will not tell you what is optimal which has to be carried out using hydro dynamics and trial and error to an extent.

The development of V foils on the lower trailing blade edge:

To ensure feathering functionality, and recognizing that in the real world propellers are subject to fouling, we added two small the foils extension to the lower trailing edge of each blade. This then allowed us to easily grind off during assembly the appropriate side leaving a small extension that when Sailing had the effect of biasing the blade such that the tip favoured movement in the head direction that’s preventing any winding up of the internal torsion spring which could lead to reverse engagement.

We needed to deal with growth on the blades, such as barnacles, oysters and also the rarer situation of for example seaweed or some other flotsam, such as a plastic bag fouling the blade while sailing.

Having this for an extension only on the base of the blade had no effect on motoring performance as the speed of advance at this lower section of the blade was really only matching the forward speed of the vessel so generating no forward thrust.

The analysis of these small foil extensions was undertaken by Flettner – a very early and highly respected German helicopter design engineer – who added a very small piece of metal sheet to the trailing edge of the rudder of an ME109 World War II fighter that could be easily bent with a simple spanner so biasing the rudder to remove any imbalance on the control stick.

Reverse screw switched from UNC ¼” to M8:

From approximately mid 2008 we increased the thread size to M8 which was a heavier screw more appropriate to the higher powered engines and larger blades e.g. 19.50” that were coming into service.

All Reverse rollers, either conical or Tri-roller design will fit over either screw, as the bearing dimensions have not altered.

The hexagonally head remains unchanged on both designs. It is a simple task to bore the existing thread with a 7.3 mm drill and re-tap using an M8 x 1.25 or standard M8 taper tap and stainless lubricant for those wishing to upgrade.

Reverse screw attachment:

It is important to ensure that each of the three M8 threaded Reverse screws ex SS 316  that hold the Tri-Rollers are retained securely in the boss of the unit. The screws are machined with a landing above the thread consisting of the 9.0 Ø Tri-roller bearing and when tightened pull down flush onto this flat.

Any side force on the screw thus generates a tension in the M8 screw as it attempts to roll up about the axis of the flat on the Tri-roller and the flat on the boss.

Each screw thread(s) is coated with a red high strength grade MIL spec Loctite™ 277 and torqued down using a torque wrench.

We then had two options to provide a margin of safety with a second level of security to ensure these do not come loose.

One obvious option is a spot of weld from the inside to the boss, but this excludes any potential removal for any reason at a future date. In addition this would introduce a different grade of SS 316 with the inevitable possibility of generating an electro potential across the joint and consequent corrosion.

The approach we use is simply to pin punch the underside of the mushroom headed boss near where the screw exits. This provides a slight distortion and tightens the boss down onto the thread of the screw making any removal very difficult – as all the normal tolerances between the thread of the screw and the thread tapped on the boss have been removed.

This still allows for removal of the screw, normally requiring the addition of heat to soften the Loctite™, but does require a much increased torque to undo the M8 screws.

Our experience from the over 200,000 screw years of service is that unless we have an environment experiencing extreme and abnormal corrosion with electron flows from an external source to the sharp thread edges, this mounting method has proved to be 100% reliable and excludes any possibility of an electro potential being generated from an additional grade of SS 316.

Four bladed K4 unit for  larger 50 – 75 hp installations:

With the advent and increasing popularity of higher horsepower installations, particularly units such as the Volvo D2–75 and similar Yanmar units required for the ever larger vessels becoming more popular we undertook a development program utilizing as many of the standard components as we could to address this market.

Due to the larger shaft sizes required for these higher power levels a new larger boss was required to accommodate up to 40 mm ISO shaft mountings or 1.500” shaft in SAE mounting.

Blade area to displacement is a critical design ratio for any propeller and the higher displacement typical of these large vessels required a full bladed unit. These are typically smooth running and meant that stress levels per blade were at the 20 hp level typical of the existing K3 3 bladed unit where 60 horsepower over three blades produced the same stress levels per blade.

Developments undertaken on the Tri-roller concept and mounting of the reverse screw was able to be completely duplicated on these larger units as was the Titanium blade mounting pins. The same blades were trimmed to a larger radius at the base to fit the larger boss. Thus a large portion of the components were able to be used on this K4 unit providing positive commonality and economic benefits and reduced component stockholdings.

The first unit was installed for trial in 2011 – there are now some 200 units installed since 2012.

Threaded Titanium Blade Attachment Pins:

For the initial years our units were produced using simple quarter inch pins and nickel silver that were pressed/tapped into a hole in the blade that had been drilled 0.004” under size.

We were not able to use SS316, as it is prone to crevice corrosion which was likely to be experienced in this application.

We have seen many units over the years where these pins have been 100% successful with no design issues emerging.

However if for some reason, which we did not recommend, the pins had been removed -each time this tended to drag material from the hole and they would become progressively less tight in the blade.

To offer a solution where we could eliminate corrosion with confidence and also ensure that the blade mounting pin was secure under any circumstance we designed a new blade retention pin ex 8 mm Titanium rod stock whilst retaining the quarter inch undersize hole used previously.

These pins turned from titanium rod stock have a slotted head on one end and a female thread on the other which will except a small male threaded and slotted cap. Both the headed end and the capped end require a standard 45° countersink leaving 25 mm in the blade.

Mounted with a blue medium grade Loctite™ on the thread we have yet to see a scenario in many tens of thousands of operating years of a single failure of this mounting system.

This is extensively documented on our webpage under:  Blade Mounting

TRI Roller – Reversing roller modification(s):

Coupled with the advent of the stiffer and stronger blade material and where rates on the blade roots which contacted the reverse rollers, we undertook an extensive research program to offer an approved solution to the simple conical roller that we had progressed to.

In addition we had found that despite extensive instructions to the contrary, the fact that the antifouling was often carried out in a yard and not by the owner, we had to assume that the whole unit would be antifouled and this would invariably see the reverse rollers, whose function was to rotate upon contact with the blade root during a reverse function seized up with antifouling paint or Prop-Speed.

Using a sliding motion, rather than a rolling motion, would very dramatically reduce the point pressure on the blade root and consequently reduce the wear rate.

After extensive trial and error we found that what we term a Tri-Roller, which was basically a conical roller with three flats machined on it would generate a sliding motion with low contact pressure per unit area during a reverse function.

However to ensure it did not seize up from antifoul application, these three flats would allow the reverse roller to be rotated through 120° for each reverse function engagement using the mechanical force of engagement.

Any addition we designed a small press fit polypropylene cap that could be simply tapped into the upper surface of this or the previous version conical roller – as an additional insurance to keep antifouling and any growth deposits away from the bearing area of the roller and mounting screw.

We have been using these for many years now and have yet to see a Tri Roller that has frozen and regard this as the optimal approach to the design requirements involved.

In addition – to further reduce anywhere on the blade root we have machined a small tapered cylindrical surface between the conical surface and the flat. We also linish this transition to ensure that the leading edge of the sliding surface does not dig in or scrape the composite material during reverse engagement.

Given the multitude of clutch types that exist in the market we have also added what we term and “ Impact Screw “ to the blade root at the point of maximum pressure experienced during a reverse engagement function, which occurs approximately when the blade is in a 45° pitch position, on its way to the normal 24° maximum pitch of the Kiwiprop design.

This provides a metal on metal contact from the Tri-roller to the blade root and has virtually eliminated wear at this contact point.

This is well documented on our website under the heading: Impact Screws

Blade root  V Seals:

The very early units we produced did not have a seal in the blade root, but depended upon the low tolerances and shape of the blade extending over the spherical blade carrier which prevented high-pressure water forcing into the blade / blade carrier and removing grease over time.

To minimize the grease removal we then added an O-ring to the base of the blade which provided improved sealing. These readily available and low cost seals did provide an improved level of ceiling and a small amount of flexibility to accommodate the inevitable tolerances which can change over time between the blade route and its mounting.

To provide a further improved level of sealing, we designed a carbide cutter to machine a stepped recess in the blade root and then made a matching die to produce a softer V – Seal with the ability to accommodate the inevitable wider range of tolerances from assembly variations and wear over time between the blade root and blade carrier casting and leg.

We are confident that these seals do provide a higher level of grease retention, and by the very small quantities required when greasing the blades post haul out. Care must be taken at this stage, as carefully described in our video and manual, not to over pressure when greasing as the seals are so effective they can be distorted from the very high pressures that can be generated with a normal grease gun.

Material changes – Glass reinforced poly-propylene Nose Cones:

The first units we produced in both Shaft and Saildrive configuration used a white Acetyl Nose Cone for some years. We needed a material available in rod format for machining purposes.

Acetyl has many attributes for this role, it is widely available, is very tough and not prone to cracking so accepting of the four cap screws that hold the two halves of the Nose Cone(s) together. It does however expand over time when continually immersed as this component inevitably is in service. This could be accommodated by simply providing slightly greater tolerances when new – but being an un-necessary variable – in a perfect world it would not be present.

On the advice of our plastics engineer suppliers we switched to a much harder PETP which is stable underwater but more prone to cracking – particularly if overstressed. Low temperatures for example which shrink the length of the cap screws holding the two halves provides additional stress. Overtightening without a torque wrench also could lead to overstressing. A small percentage of these displayed cracking after some years of service, but continued to deliver the required functionality of transferring forward thrust to the boss and accepting the tail of the internal torsion spring to pre-tension required for the feathering function.

In 2008 we found that we could obtain in rod stock format – a glass reinforced polypropylene product from the US which was not available in New Zealand that met all our material design requirements, very tough, very strong and totally impervious to and dimensionally stable under water. We have used this product exclusively now for nearly 13 years and have yet to experience a failure.

Internal sleeve and aft washer switch to Vesconite:

The first units we produced were from nickel aluminium bronze castings which provide an excellent bearing surface between similar metals. Over time – to cater for increased volume production we switched initially the blade carrier casting, followed by the boss that fits to the shaft taper or spline in the case of the Saildrive to a lost wax investment casting in SS 316.

SS 316 has many admirable properties for continuous immersion in salt water but is prone to what is termed  “ galling “ whereby two moving soft surfaces  “ gall “ or catch and freeze when used in a moving bearing type situation as we had with the 100º of movement between the boss and blade carrier during a reverse engagement function.

To address this we needed the material that was impervious to both saltwater and hydrocarbons as we would be lubricating the bearing and retaining grease inside the unit.

A fibre reinforced composite product from South Africa used extensively in marine and heavy industry labelled Vesconite was selected.

We inserted a sleeve between these two components on the bearing service, and a washer with an L-shaped profile to assist in grease retention between the boss and blade carrier aft joint contact surfaces.

These have proved very resilient over long periods of time and have delivered the functionality required. The larger K4 four bladed unit also has a washer at the forward end as the Nose Cone for this unit is also from SS 316.

Web site development:

Over the years we have developed a very extensive website containing many hundreds of pages of what we believe to be relevant information that is useful to a Kiwiprops or potential Kiwiprops user.

The website has been maintained on a very regular basis to always be current and provide an authoritative source of information relating to the unit.

To assist visitors to the website, on the upper right hand side of the homepage there is a keyword search function that covers the entire database.

Simply entering a keyword will bring up every reference in our database containing that keyword – a very useful function.

Categories
boats

Sail faster and more often

genoa poled out gobb

All photos: Leica Digilux 2. Using a pole to hold out the jib when sailing downwind.

 

Part one: Setting up a more efficient rig for windward and downwind work.

No one wants to motor when they could be sailing. The wind is free if only we can harness it’s power. Here are some suggestions, tricks and secrets I have learned over the years that have allowed me to sail my boat when most people have given up and started their engine.

Most yachts today are a huge compromise between ease of use and cost of manufacture. The two sails of a sloop work for some of the time and when they don’t serve, the sailor can use his reliable diesel engine to get where he wants to go. Boats are expensive and it’s a very competitive market so yachts are rarely sold with the extras that make them more efficient.

Many sailors hate running downwind but I don’t know why. When a yacht is properly set up, there is no more pleasant way to eat up the miles. The problem is that the basic sloop rig is not set up to run down wind. The modern solution is to fly a spinnaker but it’s hardly a simple solution. Why not use the sails that are already on the boat? Simply polling the Genoa out on one side and putting the main on the other is an excellent way to sail down wind yet I am constantly amazed how rarely I see this technique employed.

One of the great things about this set up is that it can work from a broad reach to a dead run. Here’s how it works. Lets say that the wind is coming from aft but slightly more on the port side. Let the main sail out to starboard. Take a line from the end of the boom and tie this ‘Preventer’ line to a cleat up forward. Now the boom cannot move or the sail chafe against the rigging as the boat rolls. Also, if you were to steer a bit wild, the preventer will stop the sail from gybing.

Then pole out the genoa on the opposite side to the mainsail. The lazy sheet is tied down to the foredeck as this stops the pole from lifting. In an ideal world, the genoa should be held out so that it is flat, this way it will not flap about and make noise. Now you have a fabulous set up for running downwind that only cost you the price of the pole and mast fitting. If your boat already has a spinnaker pole and track you may already have all you need. You don’t even need a topping lift for the pole as the sheets will hold it in place.

Since the area of your main and genoa approximate the area of a spinnaker you do not sacrifice as much sail area as you think and this works surprisingly well and once set up does not need much looking after. If your boat is cutter rig, you can even hoist the staysail and sheet it ‘fore and aft’ to help reduce rolling.

classic tell tales gobb

Note the tell tales on the genoa flying straight and true. This is the sign of a well trimmed sail.

Most modern boats sail well to windward but there are still ways to improve on the situation and efficiency of the existing rig. Perhaps the most important item you can add are tell tails on the sails. There have been many articles written about tell tales so I am only going to cover them briefly. On the Genoa, these are fitted a small distance behind the luff. Small windows in the sail allow you to see the tell tales on both sides. When all the tell tales are flying straight, the sail is properly trimmed and working at maximum efficiency.

tell tale windows gobb

Windows in the jib allow the tell tales to be seen on both sides of the sail.

The mainsail needs tell tales fitted to the leech. Start by trimming the genoa. The tell tales can even tell you if the sheet lead is correct. Once the genoa is properly trimmed, trim the mainsail until all the tell tales are flying. Don’t worry if the main is back winding a bit, the most important thing is to get all the tell tales flying. Tell tales cost next to nothing too and help you to learn the best positions for the sails, leads and angles so that you can get the most out of your boat by ‘seeing’ the wind.

tell tales mainsail gobb

All tell tales flying from the leech of the main sail.

In light airs and choppy seas, do not ‘pinch’ instead come off the wind a little for more speed. If the seas are choppy try introducing a little ‘twist’ in the sails as this helps the sails keep power in them as the boat pitches.

 

Sail Faster and more often Part 2: Parasitic Drag

One aspect that is often overlooked when trying to improve sailing efficiency upwind is Parasitic Drag. Additions such as dodgers may make sailing more pleasant but they cause drag and will slow the boat down. Dinghies, lifelines, outboards , mast steps or almost anything attached to the boat will cause drag. The effect of Parasitic drag can be quite drastic so anything you can do to reduce it will enable you to sail higher and faster to windward. Many dodgers (sprayhoods) are huge and run the full width of the boat, does it need to be that high? Perhaps the dodger could be made smaller and just cover the companionway hatch. Can the outboard go in a locker?

dodger gobb

Another way to increase speed and efficiency is to consider what is going on under the waterline. Even a slightly grubby bottom can cause a lot of drag so it’s worth considering the type of antifouling you are using. Every year the paint builds up until the surface is quite rough, and this will slow you down even if there is no growth. Consider using an antifouling like Coppercoat which is not only efficient but is also smoother than conventional paints as it is only applied once every ten years or so.

Anything under the waterline that is not smooth or hydrodynamic will cause drag. Anodes and sea cocks are an example. If the anodes are not being corroded much, consider fitting smaller ones to reduce drag. There is a reason why racing boats have no skin fittings and often no antifouling at all. Dennis Conner’s boat Cotton Blossom didn’t have antifouling. Instead she was sprayed with a red epoxy paint that looked like antifouling and it was sanded down with fine wet and dry sandpaper to get the surface as smooth as could be and scrubbed by a diver when it started to get slimy. Obviously few sailors are going to get as anal as this in the quest for speed but Mr Conner won every race he entered with her.

cotton blossom gobb

Perhaps the biggest cause of drag under the water is the boat’s propeller. Even a fixed 2 blade prop will cause a large amount of drag and cause turbulence over the rudder, especially if it is fouled. In moderate winds the loss is probably not particularly noticeable but in light airs and choppy seas it could make the difference between being able to sail or having to start the engine. Even though it seems odd, it is a scientific fact that a stopped prop will actually cause less drag than a rotating prop so locking the prop can help. If you have a two blade prop it might be possible to lock it in a vertical position behind the keel to reduce drag. If you have a fixed three blade prop then you are really sacrificing sailing performance.

The answer is to fit a feathering or folding prop. Folding props are very good for reducing drag but they do not work so well when motoring so a feathering prop is the best overall solution. There are many different brands on the market but they can be very expensive. One problem with most feathering props is that there is always at least one blade that cannot align with the flow and so there is always some drag remaining. A clever solution to this problem is made by Kiwiprop. Here is a three bladed feathering prop that has plastic blades and a stainless hub. There is no need to fit an anode and the pitch can be adjusted without having to take the prop apart. The blades are all independent so they each follow the flow with the minimum of drag. The Kiwiprop is suitable for engines up to 55hp and is also the cheapest feathering prop on the market.

With a feathering prop fitted sailing performance, especially in light airs will be greatly improved and with no loss in motoring performance, in fact you may well find that that also improved, especially if you are changing from a fixed two blade. If you want to improve sailing performance a feathering prop is one of the most cost effective ways to do this.

Sail faster and more often Part 3: Adding weight

Another way to spoil sailing performance is to add weight to a boat. Of course much depends on the type of yacht you have, a heavy displacement yacht will be able to soak up more weight without detriment than a light weight yacht will. The distribution of weight also has a crucial effect on sailing performance, if not safety.

If you must add weight, the best place to put it is as low and as near the centre of the boat as possible. Obviously this isn’t always possible and there isn’t much you can do to change the basic design of a boat to improve it but it’s worth bearing in mind nevertheless.

It is always wise to keep weight out of the ends of the boat as this will reduce pitching. Yet I often come across boats that have 100m or more of heavy anchor chain stowed right in the bows and this can have a tremendous effect on a yacht’s sailing performance. Do you really need all that chain? How often do you need to anchor in 30m of water? Many modern anchors are designed to work with a small piece of chain and the rest of rope which is much lighter and easier to handle. If you no longer use chain, you might find you no longer need that heavy windlass either.

The same applies to other items, such as outboards, dinghies, gas bottles and liferafts etc. The further you can stow them from the ends the better. Careful placement of stores down below can also make a difference. By putting heavier items such as tins and fluids as low as possible, and placing the lighter items elsewhere great savings can be made. I know all this seems excessive but if you consider this weight issue all the time, you will find yourself sailing more often and the boat will be stiffer and roll and pitch less which is more comfortable too. Like many things, it’s not just one thing that makes the difference but an accumulation of many small actions that add up.

The rig of a boat has a massive influence too. The more stuff you add to the mast, in the form of antennas, radomes etc the more tender and pitchy the boat will become but even here savings in weight can be made. Ropes are heavy, so you might be able to reduce the diameter of the halyards and save quite a bit of weight here. Consider using wireless instruments since you can lose entire cables this way. The use of LED lighting may allow you to use lighter electrical cables too. I know it doesn’t sound much but every little helps.

Sail faster and more often Part 4: Light weather sails

mps 1 gobb

One of the best sails you can buy for light air sailing is an MPS. There are a lot of different names for this sail but it’s basically an asymmetric spinnaker. The big difference between this and a normal spinnaker is that it is flown like a jib with only a pair of sheets and is therefore much easier to use. The MPS can really make the difference between sailing or motoring. As I type this we’re sailing at over 5 knots with a really light beam wind and have already passed any number of yachts motoring. The MPS is capable of using apparent winds from about 70 degrees to 140 degrees so is a useful sail to have.

At first the MPS can seem an intimidating sail to hoist and retrieve but as many things there are techniques that will help. The best to way to launch the MPS is to hoist it behind the set jib, this way it cannot fill. As soon as the MPS is up, drop or roll the jib and the sail will fill. An MPS is a very powerful sail and needs to be treated with respect but so long as you get it hoisted before it fills it is quite docile.

Normally the MPS has two sheets so that it can be gybed but I find this too complicated and the long lazy sheet has a habit of getting drawn under the boat. Instead I use only one sheet and hoist the sail on whichever side I need at the time. Normally the sheet will need to be led to the back of the boat to get a good lead. A block can be affixed in the appropriate place without much difficulty and then lead to a genoa winch. Often the MPS works best without the luff being tight, so experiment by either letting the halyard go a bit or easing off the tack. I use a 6-1 tackle on the tack of the sail which makes adjustment very easy. The MPS also works best by not being over sheeted and often the best trim is when the luff is gently flopping over from time to time.

Getting the MPS down is a bit harder than getting it up but again, there is a technique. Re-hoist the jib and sheet it in. Then sheet the MPS in hard so that you can reach the foot of the sail from the deck. This job is much easier with two people, one on the halyard and one gathering. Let the halyard go in stages and gather as you go. Because the MPS is blanketed by the jib it will not have any wind in it and will be easier to get on board. I find sitting on the sail I have gathered keeps it from getting out of hand.

mps 2 gobb

 

Sail faster and more often Part 5: The real secret of sailing more often

When we first came to the Mediterranean we were lucky if we sailed for 25% of the time, now our average is nearer 60%. This massive increase in days sailed is due in part to the improvements mentioned previously but I have saved the best until last. It’s simple, if you want to sail more often, you’ll need to wait for a good wind. It sounds so obvious doesn’t it? Yet this simple fact is at the heart of the matter.

Nowadays, weather forecasting is pretty good and the sailor is able to get great information, usually free from a number of sources. If you have time it is well worth watching the weather and planning your trip around it instead of trying to set an impossible itinerary based on what you would like. We can’t change the weather but we can use it. Rather than setting off with a poor wind why not wait a few days until it changes. In the meantime you could explore the area where you are. Every time we have followed this simple advice we have had good sailing.

We all rush around these days and pay the price. A bit of patience can reap dividends. If you genuinely want to go sailing rather than motoring, all these nuggets of hard learned information will help you. I know, it all seems so obvious and you knew all this anyway but like I said earlier it’s a bit of everything. It’s like varnishing. Many people often ask me what is the secret to beautiful varnish but there is not one secret but many small ones that club together to make for a good result. Even if you miss out one or two of the secrets along the way, you will probably still end up with a good result anyway, but ignore all the secrets and you won’t be happy with the result at all.

Sailing costs very little, it is satisfying, good for the soul and offends no one but motoring on the other hand is noisy, smelly and expensive. Maybe you only consider the cost of the fuel and lets face it, yachts are not economical when motoring. We are lucky if we manage 20 miles to the gallon, and that is with a small boat, but there are other costs to factor in. Every hour you motor wears out the engine, the seals, impellers and bearings. Engines need servicing and that can be expensive so obviously the less often you can service an engine, the more money you will save. Beyond even the cost is the moral issue. What could be better for the environment than a sailing boat, quietly moving from A to B. It’s as close to Perpetual Motion as we mere mortals are ever likely to get.

The satisfaction that comes from a trip made under sail cannot be ignored so it’s well worth making the small amount of effort required to set your boat up and understand the finer points. Happy sailing!