Technique: Hull finish

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Hull finish

Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Technique
Forum Discription: 'How to' section for dinghy questions and answers
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=12091
Printed Date: 27 Jun 25 at 3:05am
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Topic: Hull finish

Posted By: Splash II
Subject: Hull finish
Date Posted: 22 Jul 15 at 3:36pm

Hi all,

What's peoples opinion on underwater hull finishes...??? I know all the arguments for and against polishing, high grade wet & dry, laminar flow over the surface etc. But in practice what do you feel is the best finish on a few years old GRP hull.

Has anyone ever tried experimenting with some of the expensive automotive nano technology finishes to get an extremely smooth finish. I've seen the results of this type of finish and the water just beads and runs off very easily.

Replies:

Posted By: JimC
Date Posted: 22 Jul 15 at 3:52pm

My feeling is that the behaviour of droplets of water on a dry hull is pretty much irrelevant. It is underwater and will be wetted.

So just get it as smooth and fair as you can with the effort available.

I suggest though you should be putting at least double the time into the foils as into the hull. This is especially true for pivoting board boats, where all too often that centreboard just stays in there accumulating gunge and gouges from one year to the next.

Posted By: Presuming Ed
Date Posted: 23 Jul 15 at 4:05pm

Sanding chart on an old thread on SA here:

http://forums.sailinganarchy.com/index.php?showtopic=84231#entry2068554

Posted By: Rupert
Date Posted: 23 Jul 15 at 5:48pm

I'm a fan of polish on a 1200 grit sanded hull. Mainly I like how easily it slides onto the trolley after sailing, and in my head it is fast, which is what matters.

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Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686

Posted By: davidyacht
Date Posted: 23 Jul 15 at 6:09pm

Bit of a fan of a good soapy wash to get off the crud ... Then polish with Hullcote.

Wet and dry finish on foils, something around 800 seems fine to me. IMO don't want them too polished as I think this encourages separation, besides which too shiny when you tip it in.

As Jim said, time spent on leading edges and trailing edges of foils is well spent. Also transom edges and slot gaskets warrant a bit of care.

Those who's formative reading was Elvstrom Speaks (should be on any bodies reading list) may remember Elvstrom talking about crud making a discernible difference to performance.

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Happily living in the past

Posted By: JimC
Date Posted: 23 Jul 15 at 7:29pm

Rudders mirror finish if you can manage it. That would be good for centreboards too if you didn't have to stand on them to right the boat.