Dinghy hull coatings

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.

Edited by Lukepiewalker - 13 Dec 13 at 9:35am

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).

Originally posted by Timmus If I remember correctly he did the experiment by towing Tasar hulls around. One that had been covered and another that had been taken to venue uncovered on the road. Funny I have just started re-reading HPS (hardback) and was wondering if it was available on Kindle or variants???? Its a heavy read indeed, but even heavier in hardback

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.

Originally posted by JimC Originally posted by sandgrounder Teflon is a polymer, 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.

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?

Edited by getafix - 13 Dec 13 at 12:17pm