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Kiwiprop feathering propeller long term review

kiwib

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.

P1030428bb

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

Modern teak decks – The truth hurts

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In the last 15 years I have worked on more teak decks than I care to remember. I think I’ve seen every problem that exists. What you have to know straight away is that, like anything, teak decks need looking after. If you take care of your decks they may last 20 years plus, if you don’t you’ll be appalled at how awful they look after half a decade. Because solid teak decks has been the norm for hundreds of years they have understandably earned a serious reputation for longevity. Today’s teak decks are not the same thing at all.

In most cases modern teak decks are little more than a quick way for the manufacturer to up the “class” of their product. They are poorly fitted, the wood is too thin, the caulking gap is usually too narrow. Because of the minimal amount of wood involved the best plug on the deck might only be 3 mm deep. Likewise the caulking, unless of adequate depth and width will not remain glued as the wood moves. However all these problems would amount to little is folk were advised on teak deck care. The most important advice is to wash the deck every week but few people can spare the time. It’s quite simple however, if you don’t wash your deck regularly it will soon go grey and dirty.

DO NOT SCRUB your deck. I’ve seen it done, the owner is standing there, his trouser legs rolled up, his knees red. True his deck looks great…. From the pontoon. If you look carefully you’ll see grooves in the planks where the softer areas of grain have simply vanished. This is how it starts, Consider that you began with a lovely smooth surface, like a CD if you like. After a scrubbing it looks more like an LP but worse, much worse. Imagine now how quickly the “peaks” will wear down as you walk on them. Of course it doesn’t end there, this is only the beginning.

If you must have a clean deck then there’s only one way and that’s a gentle wash with nothing more violent than a light detergent and a large sponge or very soft brush. If you do this regularly you will not wear down the teak but you will wash off the dirt before it gets ingrained. Dirt contributes to the wear on a teak deck. If this approach doesn’t work then you can try oxalic acid. Dissolve some crystals in warm water, do not breathe the vapours and wear gloves. It burns. DO NOT SCRUB. Rinse well. Oxalic acid should not harm anything on the boat except your skin. There are plenty of products that do the same thing but cost a lot more. If acid doesn’t bring back the colour then there’s only one thing left to do if you want a lovely looking teak deck and that is to sand it. But if you want my advise, continue to wash it carefully and often with soap and live with the deck not looking it’s best.

For some reason no one listens to me. I gladly advise people on how to look after their decks for free even if it means I don’t get any work. It’s better for everyone, except me, that you take my advice. Yet despite that I still see people scrubbing their teak. I shake my head in wonder. Did I not explain what would happen if they scrubbed? “But it looks so great!” they say. “So what’s the problem?” The problem is that the next time they see their decks they will look grey and dirty again and the only difference will be that there is less teak there now than there was before. If your feet don’t wear down the peaks then they’ll fill up with dirt making it look even worse and there’s only one way to get it out. More scrubbing. This time you’ll have to scrub harder to see a result. Can you see what’s happening? There will come a point soon when you decide the decks are looking pretty rough and need a good sanding.

Boatyards are very keen to do this work for you and why not, next time you see the boat it will look great and they KNOW you’ll be back because soon the caulking will start to roll out in long spaghetti like strips and the plugs will fall out exposing the screws and making water ingress all the more likely. Now you’ve really got a problem. The plugs are not too much trouble but there will be hundreds to do. The real problem is the caulking. Just because some comes out really easily does not mean that it will be all like that. No, some of it will be sticking just like the manufacturer intended. You can make a special scraper to remove it but inevitably you will slip and damage areas and worse you will enlarge the groove. If you’re really lucky you might be able to use a router for about 35% of the deck but routers are vicious and it’s all too easy to make a mistake. Even a small enlargement of the slot will look terrible. Not only that but you’ll need a curved guide to run the router along for each slot. This takes ages. Bad enough if you’re doing it yourself but unbelievable if you’re paying a yard. Specialist tools exist but they are hideously expensive and it’s only the specialist yards that are likely to have such a tool but they will be charging by the hour and there’s always a lot of work on any teak deck.

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Here’s a deck fitting on the 65 foot Swan Evrika. As you can see the deck has been sanded down quite a bit over the years!

So what are the options now your deck is worn out? You can’t just remove it because underneath it will be horrid. If it was laid properly in the first place they will have keyed in the surface, that means a grinder on a plastic boat. You’ll still have to cover the decks to cover the mess. You can use Treadmaster which is a very good surface and lasts as long as teak if it’s glued down properly. Trouble is it’s not the same is it? It might be cheaper but it’s not a teak deck. You can lay an artificial teak deck. There is a plastic like lino you can lay but it looks like lino and not teak. There is even a special decking you can buy that appears to be made of sand and crushed stone in a nice terracotta colour. You lay it like teak with caulking and all. It doesn’t look like teak either and I wouldn’t want to slip along it. If anyone knows a really good alternative to teak I’d be delighted to hear about it.

Personally I would chose epoxy and cloth coated decks covered in non slip deck paint for a wooden boat and the standard non slip pattern on a GRP boat. Both are easy to clean, practical and hard wearing and keep the boat cooler below in the heat of the summer. Also I believe that laid decks on small craft can make them look a bit fussy. Other than painted decks there appears to be no realistic substitute which is a real shame since teak is a tropical hard wood and that means it’s taken decades to grow and it’s probably not being replaced.

So I hope that you can see that I’m advocating care and prevention for your lovely teak deck. To just leave it uncared for is an outrageous waste of a precious resource. If that isn’t enough to make you care for your deck, then consider the cost of replacement. Teak costs approx £3000 a cubic metre. But you’ll need a lot more than you think because just cutting down a big plank to size wastes a hideous amount of wood. The cost of the teak is a large part of the final bill. Basically you can quadruple the price of the teak to take into account the cost of first measuring and photographing the original deck to insure everything fits properly, the cleaning up of the surface underneath and finally replacing the wood. To do the job properly you may have to remove the chain plates and that means dropping the mast and completely readjusting it afterwards. Not only that but all those deck fittings that haven’t been touched for years will need to be removed and in the process don’t be surprised if many of the bolts are hell to remove or break in the process. It’s possible that some of the bolts were made specially or have been glassed over. You’ll need somewhere to do all this, perhaps it’s possible to make a good cover but even this adds to the cost. The alternative is to put the boat in a shed somewhere. Anything is possible but it always costs. Replacing a teak deck is a massive job. I laid a teak deck on a 6 metre boat and it took about ten days of frantic activity and it was a very simple deck with no joggled planks and no joins. To replace the decks on a 30 footer is 6 weeks work. 3 months for a 50 footer. We are talking about many thousands of pounds and your boat out of action for a while.

There are other considerations before you decide on a teak deck. They weigh more, the sikaflex being surprisingly heavy, not to mention the wood and the thousands of screws. Perhaps what worries me most about laid decks on Fibreglass boats is that you have to make thousands of holes in an otherwise perfectly waterproof surface to hold the deck down. Many fibreglass boats’ decks are balsa cored, that is to say that the deck is made of two layers of fibreglass with a layer of balsa wood in between. Balsa wood will not last long if it gets wet yet this strikes me as very likely. The law of averages suggests that, the chances of making 2000 holes in a deck, and them all staying waterproof for years on end is pretty slim. What happens when the balsa is rotted away? I think not making thousands of holes in a deck like this is wise. It is possible to lay a deck without screws but it takes longer and therefore costs more.

So let’s sum up. Teak decks are nice to live with and they look good. On the down side they are expensive, add weight where you don’t want it, soon look dirty, are vulnerable to red wine and sun tan oil and can get so hot in the summer you cannot walk on them. So what can you do about it? For my money I’d choose the standard non slip fibreglass moulding that comes with the boat or an epoxy cloth coating on a wooden yacht. I might have teak in the cockpit but basically I do not consider a teak deck to be a sensible thing these days. In days gone by teak was the obvious choice but things have changed. We are aware that teak comes from tropical rain forests and we all know that deforestation is contributing to global warming which is harming our planet but still yachts are sold with teak decks. Just consider for a moment how many yachts there are in your marina. Probably 30% have teak decks. (It’s more like 50% in the med) That’s quite a few boats and there are a lot of marinas in the UK. Then there’s the rest of Europe to take into account, Australia, New Zealand, USA In fact there must be millions of teak decks out there. It’s true to say that if people chose not to have a teak deck there would be a lot more trees in this world.

Sadly the whole yachting world is convinced that teak decks last forever and need nothing more than a good scrub once in a while to keep ‘em looking good. It’s simply not true. Remember when CD’s came out nearly 20 years ago, how they boasted that you could scratch them and they could still play. What Nonsense. On the one hand I am thankful for owners and teak decks since they allow me the life I lead but on the other I am angry at the waste of it all. People could save themselves a lot of time, inconvenience and money if they just took care of their decks. For some reason no one wants to spend money on “posh” covers to protect their boat. “Oh no, covers are expensive”. I hear said. Covers are “initially” expensive but they will repay their cost several times over. Not only will you not be required to replace your decks but you’ll be able to sell your boat for more because it has obviously been well looked after. It’s not just teak decks that will benefit from protection, Perspex windows, instruments and gel coat will all last longer if kept out of the sun, wind and rain. The Grand Canyon was created by erosion from the elements. When you think like that surely you can understand why I recommend covering up. We all know that the sun can burn skin and give you cancer yet we leave our boats outside soaking up this energy for years at a time. It’s worse for a teak deck because it is laid horizontally and gets the full force of the sun.

So unless I’m wrong people equate teak decks with luxury. “There’s nothing unusual about that,” you say, and if they are prepared to “pay” for it, fine. I don’t believe that anyone wishes to waste money or valuable world resources. I’m sure that it is a simple case of ignorance, call it what you will. No one will tell the truth because it’s in no one’s interests. The manufacturer can make his boat look “Lux” with teak. Other manufacturers follow and the teak deck becomes “the norm”. Boatyards and shipwrights depend on unwitting victims for their income. If you ask them to sand down your decks, that’s exactly what they’ll do. It annoys me that they cannot be more honest. If a client asked me (as they have) if I can sand their decks I explain where that will lead and in most cases they have taken my advice not to touch it. I realise that for a boatyard to take my approach is a recipe for bankruptcy and for myself I am not a rich man but I am content. I care very much about what happens to our world. I personally am glad I will not be among the future generations who must follow in our shoes. I can only do my bit, I can’t change the world, I can’t change fashion but I hope I can slow down the damage by telling the truth. So now you know, what will you decide for the decks on your new boat?