Dinghy hull coatings
Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Dinghy development
Forum Discription: The latest moves in the dinghy market
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=11254
Printed Date: 14 Jul 25 at 2:34pm
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com
Topic: Dinghy hull coatings
Posted By: getafix
Subject: Dinghy hull coatings
Date Posted: 11 Dec 13 at 1:30pm
|
As our miss-guided brethren have their floating caravans once more lifted out of the marinas and stuck on chocks, Chandlers begin to rub their hands in glee at the annual anit-fouling bonanza. Reading some of the marketing stuff that comes with this anit-marine-life unpleasantness, it occurred to me that perhaps there is a market out there, Muck-off like, for super slippery, bound to make you faster round the cans dinghy racing products.
As someone who has occassionally ventured forth with a bit of t-cut and an old rag, I will admit to not having the most sophisticated boat prep routine... what are the winners doing? what about the rest of you? What's the most slippery hull (and or foil) prep routine going? Are there any UK dinghy classes where we can cross the line between harmless 'fairing' and down right banditry of the underwater shape I also wonder? Has anyone been caught, SJ Winter Series like, in the act in the past?
|
Replies:
Posted By: sandgrounder
Date Posted: 11 Dec 13 at 2:10pm
|
T-Cut on a polyester gelcoat surface - OUCH !
Best finish on gelcoat - Farecla G3 applied with plenty of water and a foam compunding head attached to a variable speed electric polisher at ~1200 RPM.
|
Posted By: Dougal
Date Posted: 11 Dec 13 at 4:53pm
|
Just stick £5 notes all over it.... It'll be cheaper and no less effective!
------------- What could possibly go wrong? |
Posted By: Presuming Ed
Date Posted: 11 Dec 13 at 5:55pm
 ??
|
Posted By: didlydon
Date Posted: 11 Dec 13 at 9:09pm
|
What's wrong with tcut? Isn't it just a fairly weak cutting compound? How does it compare with Farecla? I've used a bit of tcut on my bottom - oooer missus - till I got bored...... Seemed to do bugger all to the few scratches I tried it on ------------- Vareo 365 |
Posted By: getafix
Date Posted: 11 Dec 13 at 10:13pm
OK, so I've actually removed (or at least think I have) a few scratches with the redoutable t-cut, but now I'm wondering if its a case of more harm than good, what's this Farecla stuff? |
Posted By: Cameron Winton
Date Posted: 11 Dec 13 at 10:24pm
| T-cut is fairly abrasive and will blend a scratch. Never very sure about using it on gel coat but think it will give a 1600+ finish. I always thought a super polished surface was more draggy due surface tension effects? |
Posted By: Dougal
Date Posted: 11 Dec 13 at 10:28pm
|
I remember the Americas cup boats years back, possibly still in the days of 12m, using a grooved pattern on the hull to create some stickiness to encourage laminar flow. Apologise for the lack of technical explanation, if I can find anything tomorrow when sober I will post it. ------------- What could possibly go wrong? |
Posted By: Rupert
Date Posted: 11 Dec 13 at 10:29pm
|
I've T cut many boats, with mixed results (sometimes an old hull will never come up shiny), but never destroyed any gelcoat. The rubbing compounds from Farecla, which I've used on moulds, have a huge choice of grades. ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: Ian99
Date Posted: 11 Dec 13 at 11:04pm
|
Morrisons Value Cream Cleaner is a surprisingly good alternative to many of the abrasive boat cleaners, and at 79p for a large bottle certainly beats anything branded as "marine" for price! It's particularly good on the textured part of Laser decks. Other than that, I tend to stick with decent quality automotive products for the polishing department. Auto Glym Super Resin Polish seems to work well on gelcoat, and also is much better than many of the others in low temperatures. |
Posted By: iitick
Date Posted: 11 Dec 13 at 11:18pm
| The 'boy' cleans his ancient Lightning hull with brillo before every big race....dosent seem to do the old girl any harm........ |
Posted By: iGRF
Date Posted: 11 Dec 13 at 11:48pm
|
I thought we discussed this once before and it was concluded that what are they hydrophilic or hydrophobic compounds were illegal. ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: Aching Knees
Date Posted: 12 Dec 13 at 6:47am
| Bring back graphspeed, the black graphite paint or international smooothie, the pink stuff |
Posted By: Presuming Ed
Date Posted: 12 Dec 13 at 7:30am
Riblets. 87 by Stars & Stripes. Also, IIRC, used by Oxford in the 87 boat race (the year of the mutiny). http://www.nasa.gov/centers/langley/news/factsheets/Riblets.html" rel="nofollow - http://www.nasa.gov/centers/langley/news/factsheets/Riblets.html |
Posted By: Dougal
Date Posted: 12 Dec 13 at 9:42am
Thank you - that's exactly what I was talking about. ------------- What could possibly go wrong? |
Posted By: JimC
Date Posted: 12 Dec 13 at 10:12am
| I understood the riblets had to be precisely aligned with the local waterflow, and were only really useful within a limited speed range. Its no good kidding yourself that leaving the hull rough will have the same effect... |
Posted By: Dougal
Date Posted: 12 Dec 13 at 10:24am
Yes - there was a large amount of precision involved. It may even have been in a Y&Y article, but I recall the riblets were applied by way of a laminate stuck onto the hull, with the grooves/ridges being in a wavy pattern and being lined up precisely with the contours of the hull. Anyone know if the technology is still being used in boats? If it worked it would seem a prime candidate for the foils on the AC72's. ------------- What could possibly go wrong? |
Posted By: sandgrounder
Date Posted: 12 Dec 13 at 10:25am
| I never cease to be amazed by the constant focus on hull finish, whilst ignoring foil finish, where the bigger gains are to be made. |
Posted By: Rupert
Date Posted: 12 Dec 13 at 12:36pm
|
Highly polished centreboards are always fun to watch after a capsize!
------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: Reuben T
Date Posted: 12 Dec 13 at 1:35pm
| I have heard that sanding to around 600 grit is the most efficient finish as it creates a boundary layer of water moving with the boat, so it effectively lubricates the hull with water. I was told this by a friend of Phil Morrison who said this was a theory that Phil believed in, therefore I am inclined to believe it. |
Posted By: Mike Holt
Date Posted: 12 Dec 13 at 3:20pm
|
Over the years I have tried every type of hull finish, sanding, T-cut and polish. Now I clean thoroughly, repair any damage and scratches and then polish with a teflon wax. My feeling is that this will keep grease and dirt off the best of any option and it is very hard to keep a boat clean, particularly in venues where there may be less than crystal clear water. That dirt on the boat will have at least as negative effect as anything else. Boat also looks better that way!
|
Posted By: sandgrounder
Date Posted: 12 Dec 13 at 5:47pm
I never could bring myself to apply a polymer (teflon) at an event, in case it brought me in to conflict with an over-zealous jury and the application of RRS 53.
|
Posted By: getafix
Date Posted: 12 Dec 13 at 5:55pm
I doubt even the jury at the Olympics has a chemistry lab to fall back on. I like idea of something which helps keep the hull clean too...we have some strimmer loony in the boat park occasionally and it does us all in scrubbing the stuff off, particularly in hot weather when it gets baked on
|
Posted By: Daniel Holman
Date Posted: 12 Dec 13 at 5:55pm
Neither could I - on the grounds of laziness, but assuming you weren't blatantly applying some go faster lube in the dinghy park, it'd be hard to police wouldn't it. Without checking that rule, how easy is it to work out which Polishes and products are illegal or not. |
Posted By: sandgrounder
Date Posted: 12 Dec 13 at 6:08pm
Why not? They must have a fairly comprehensive chemistry lab to fall back on to test for substances ingested.
|
Posted By: sandgrounder
Date Posted: 12 Dec 13 at 6:11pm
True. Maybe it's the final frontier for exploitation...
|
Posted By: JimC
Date Posted: 12 Dec 13 at 6:28pm
|
If my memory serves me right RRS 53 was designed to prohibit some stuff that you gunged on before the day's sailing, and which slowly dissolved/melted/something or another into the water over the day.
I'm quite sure any kind of normal wax or teflon polish is just fine. |
Posted By: sandgrounder
Date Posted: 12 Dec 13 at 6:55pm
|
53 SKIN FRICTION A boat shall not eject or release a substance, such as a polymer, or have specially textured surfaces that could improve the character of the flow of water inside the boundary layer. |
Posted By: davidyacht
Date Posted: 12 Dec 13 at 7:00pm
| I like Smoothy and graphspeed |
Posted By: davidyacht
Date Posted: 12 Dec 13 at 7:01pm
| I like Smoothy and Graphspeed |
Posted By: iitick
Date Posted: 12 Dec 13 at 8:30pm
|
Posted By: Rupert
Date Posted: 12 Dec 13 at 9:07pm
|
I think it has to be specially textured for the job, rather than just be put on with a trowel in the absence of a paintbrush! Now, depending upon what you drink, weeing down the centreboard case could be seen as releasing a substance to improve laminer flow. ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: iitick
Date Posted: 12 Dec 13 at 10:10pm
| Still very difficult to prove what is a finish to improve performance or a finish to improve appearance. |
Posted By: sandgrounder
Date Posted: 12 Dec 13 at 10:34pm
Haha, certainly a difficult rule to enforce / police.
|
Posted By: sargesail
Date Posted: 12 Dec 13 at 11:34pm
More to the point it is spefically not aimed at Teflon type polishes.
|
Posted By: JimC
Date Posted: 13 Dec 13 at 12:38am
|
Knickers severely in a twist here over nothing people.
The rule prohibits two separate treatments. As I said before, if my memory serves me right RRS 53 was originally written to prohibit a polymer based material that you gunged on before the day's sailing, and which slowly dissolved/melted/something or another into the water over the day. I'm certain any kind of normal wax or teflon polish is just fine. The textured surface bit was added later to ban the riblets stuff Dougal mentioned on page 1. It would be easy enough to spot and distinguish from a 60 grit sandpaper finish because it has to be specially aligned with water flow etc. These are both expensive complicated and time consuming treatments, and in the case of the gunge polluting as well. Its a good thing that they are banned, but the rule has absolutely no relevance to ordinary club sailors like me, and probably most of you. |
Posted By: yellowwelly
Date Posted: 13 Dec 13 at 7:29am
| I know once I couldn't be arsed to put my undercover on to tow a boat to an event- big mistake, I went a lot slower as a result. Why is that? Just dirt from the road or is it the exhaust from the car? |
Posted By: Rupert
Date Posted: 13 Dec 13 at 8:38am
|
Or maybe just in your head? Not yours specifically, but I think most of us feel good about having a nicely finished, clean hull, and "feel fast". Not to be underestimated, that feeling.
------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: iitick
Date Posted: 13 Dec 13 at 8:46am
| I believe diesel is the main culprit, nasty sticky stuff. A friend of mine wraps polythene round his hull under the undercover because he thinks it gets through the fabric. Mind you he is a bit like that. Our undercovers are pretty filthy though. better on the cover than the boat. |
Posted By: yellowwelly
Date Posted: 13 Dec 13 at 9:11am
| It was a petrol car, but maybe I'd tailgated a truck or something.... but definitely a noticeable effect. |
Posted By: Lukepiewalker
Date Posted: 13 Dec 13 at 9:35am
|
Road film. Bethwaite has an experiment in the first HPS book where he tested the effect. Think of all the rubber, oil, diesel, tar and assorted other crap getting thrown up by the wheels of yours and passing vehicles. And consider the effort required to clean the same film off your car.
------------- Ex-Finn GBR533 "Pie Hard" Ex-National 12 3253 "Seawitch" Ex-National 12 2961 "Curved Air" Ex-Mirror 59096 "Voodoo Chile" |
Posted By: Lukepiewalker
Date Posted: 13 Dec 13 at 9:48am
|
Or if you are feeling really keen, look at a roundabout after a heavy rainstorm and see the pretty rainbow patterns from all the diesel mixing with the rainwater. Roundabouts are particularly prone to diesel spilling out of lorries as they go round the sharp turn. ------------- Ex-Finn GBR533 "Pie Hard" Ex-National 12 3253 "Seawitch" Ex-National 12 2961 "Curved Air" Ex-Mirror 59096 "Voodoo Chile" |
Posted By: Mark300
Date Posted: 13 Dec 13 at 10:17am
|
Bethwaite did indeed look at hull and foil finishes in HPS. He took two identical Laser rudders, finished them both to 1200 grit wet and dry, and then polished one of them to a mirror finish. His experiment using the foils showed the unpolished foil showed a 23% reduction "in cross flow lift force, i.e. the steering force at 11 knots". So he concludes that not only does a polished foil reduce drag, but it improves control. HPS2 had some measurements on different finishes on 49er hulls, after noting degraded performance in a boat covered in a film traffic grime. He basically concluded that the higher the polish, the less the resistance (can't find the page in the book, its a heavy read that one). |
Posted By: sandgrounder
Date Posted: 13 Dec 13 at 10:32am
Teflon is a polymer, hence the potential for conflict. I know a World Champion / Olympian who avoids teflon based polishes for this reason.
|
Posted By: Mark300
Date Posted: 13 Dec 13 at 11:02am
You are right - it is in HPS, two boats go to the same venue and back uncovered, one gets washed and cleaned, the other doesn't. 2% difference in hull drag according to Bethwaites experiment. His conclusions are (i) and polished clean hull is fastest, (ii) there is no evidence to support the "a rough surface holds a layer of water on the hull and is fast" claims, and (iii) the area of shark skin type finishes is not sufficiently understood to replicate into dinghies hull finishes. |
Posted By: JimC
Date Posted: 13 Dec 13 at 11:27am
Gel coat's a polymer too. So is epoxy resin and polyurethane paint. These papers includes some of the sorts of research that prompted the ban. http://conservancy.umn.edu/bitstream/114203/1/pr090.pdf http://deepblue.lib.umich.edu/bitstream/handle/2027.42/62411/belbing_1.pdf?sequence=1 The crucial part of the rule is that its a water soluble polymer that is *ejected or released* into the water, thus causing pollution. That is not what's going on when you apply a conventional polish - ie anything you can buy from a car shop, because they don't eject or release anything as part of the function of the polish. Either your man misunderstands the rule, or possibly you've misunderstood him. |
Posted By: sandgrounder
Date Posted: 13 Dec 13 at 11:45am
Gelcoat, epoxy resin and polyurethane paint don't dissolve in water.
Teflon based polymer polish applied to hull / foils does dissolve in water.
I only know what he told me - he's a lot closer to ISAF than I am.
There are many alternative methods of achieving a superior finish to hull and more importantly foils, one of which I've mentioned above. Why would you take the risk at that level of competition?
|
Posted By: MerlinMags
Date Posted: 13 Dec 13 at 11:48am
This was published in many dinghy racing books of the 80s, but has since been proven wrong. Smoother/polished is better, according to all the modern books. |
Posted By: getafix
Date Posted: 13 Dec 13 at 12:16pm
| So what's the best product, having done some investigation after earlier posts I now see Farecla is a rubbing/cuting compound, so basically another variation on t-cut (perhaps not as 'harsh'). Once my hull is smooth, what's the best 'polish', or 'teflon wax', to keep it clean and slippery? |
Posted By: yellowwelly
Date Posted: 13 Dec 13 at 2:05pm
| green vinyl wrap innit? |
Posted By: Paramedic
Date Posted: 13 Dec 13 at 9:09pm
|
Farecla do a wide range of polishes.
The G series are really aimed at paintwork, but are effective on GRP too. G6 is the polish to use, G3 is a bit too fine. G10 is great for finishing dark colours. the profile range is designed for use on gelcoat. 100 is seriously coarse, 200 less so etc etc. Profile 100 is supposed to polish 600 grit wet/dry but needs to be followed up with a finer polish for the same result as 1200/G6 + elbow grease. It's probably better on dark colours. Both systems have their merits. I think that the profile range will get you a result quicker, but you use more different materials. ------------- |
Posted By: deadrock
Date Posted: 14 Dec 13 at 6:44pm
| A chap at Draycote in the 1970s, I think his name was was Mike Sharp(e): his Laser was a little too scratched for his liking, so he got a drill-based circular sander and a sheepskin mitt, daubed it with T-cut, and started to polish out the scratches. He stopped when his hull started to change colour. |
Posted By: getafix
Date Posted: 17 Jan 14 at 7:25pm
| Just watching the One Show, now I know what I need, a coating that makes my beloved 100 super-hydrophobic, looks flipping quick! |
Posted By: iitick
Date Posted: 17 Jan 14 at 7:32pm
| Hydrophobic? You been bitten by a mad dog? |
Posted By: Dougal
Date Posted: 17 Jan 14 at 10:14pm
|
The One Show? You been bitten by a mad dog? ------------- What could possibly go wrong? |
Posted By: getafix
Date Posted: 18 Jan 14 at 10:49am
| No madness, I think this would make your hull extremely slippery through the water but still enable you to get on the board, hold the boat securely... http://www.youtube.com/watch?v=IPM8OR6W6WE |
Posted By: Rupert
Date Posted: 18 Jan 14 at 2:36pm
|
I can see that tell tales will never need to stick again. Would it be race legal on a hull?
------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: getafix
Date Posted: 20 Jan 14 at 9:22am
Quite sure the luddites will try to ban this type of coating, but it could have an incredibly significant impact on hull design and by association, rig design, for many a year. If hulls today are designed to be pushed through the water (or push water out of the way in certain aspects) then imagine if water simply runs over the surface with practically no, or very little friction generated ... we could see a return to really wide platforms, able to carry much larger rigs (by dint of having better righting moment) and greater stability with more pronounced 'spray rails' to deal with the faster flow over surfaces we would see? Greater velocity through the air would also mean a flatter sail profile and make wing rigs even more practical, just as we have seen with foiling. Foil design will also have to change.....
|
Posted By: JimC
Date Posted: 20 Jan 14 at 11:23am
| Water is still going to need to be pushed out of the way no matter what, because the boat will by necessity have to be sitting in a hole in the water. All it can possibly affect is skin friction, which is a fairly small part of design. |
Posted By: Rupert
Date Posted: 20 Jan 14 at 11:45am
|
This stuff doesn't actually change the laws of physics... I have visions in my head of the boat hating water so much when you spray this stuff on that it refuses to be pushed into the water at all! Six strong men trying to launch a Topper, and it not budging an inch. ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: iGRF
Date Posted: 20 Jan 14 at 11:50am
|
Luddites? In the sailing world? Surely not.
Not sure about the coating affecting performance through the water, it's been a subject of discussion for as long as I can remember and there have been many sorts of coatings some hydrophyllic, (act like fish skin) some hydrophobic which act like the system you identify, obviously old fashioned polish worked like that and the general feeling was hydrophyllic worked better a bit like regelation in ice skating. ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: NHRC
Date Posted: 23 Jan 14 at 8:48pm
| It would be interesting to see this hydrophobic coating on sails as well as hulls. |