Dinghy development: Expanding foam filler

Print Page | Close Window

Expanding foam filler

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=12875
Printed Date: 05 Jul 25 at 12:25am
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com

Topic: Expanding foam filler

Posted By: GarethT
Subject: Expanding foam filler
Date Posted: 08 Oct 17 at 9:44am

Does anyone have any experience of using weatherproof expanding foam on boats?

I'm thinking of using it for packing rather than anything structural. If I cut/sand it, will it absord water? Can I paint to seal it?

Thanks for any advice.

Replies:

Posted By: JimC
Date Posted: 08 Oct 17 at 11:05am

It will absorb water and its fairly heavy (well by foam standards. I suppose you could paint it. The biggest problem I'd have though, if you are using it to pack inside tanks, say, is that water will lie between it and the main structure. If the main structure is wood that means rot, and if the main structure is glass, that means osmosis.

Posted By: 423zero
Date Posted: 08 Oct 17 at 11:14am

plus, it can generate pressure and cause bulges.

Posted By: zippyRN
Date Posted: 08 Oct 17 at 4:34pm

i think Jim C and 423 zero have covered the main issues

Posted By: GarethT
Date Posted: 08 Oct 17 at 4:46pm

It’s for the bottom of a tasar daggerboard case, to give something that can be rubbed down/faired. The foam that’s in there is a bit ratty so I’m just looking for something quick and cheap to fill the bottom half inch. Any time spent working on it comes out of my sailing allowance so I don’t want to strip out all the existing packing and start from scratch.

Posted By: JimC
Date Posted: 08 Oct 17 at 5:01pm

I'd be inclined to blag some offcuts of proper boat building foam, shape them and glue them in with epoxy and filler. You need to be quite careful round daggerboard cases because its suprisingly easy to bend them in that fatal fraction of a millimetre that stops the board going up and down readily.

Posted By: 2547
Date Posted: 08 Oct 17 at 5:24pm

I think in Aus they are gluing in packers that actually match the profile of the board now rather than have a rectangular hole.

Posted By: Do Different
Date Posted: 08 Oct 17 at 6:41pm

You talking a smallish amount? Epoxy resin and micro balloons perhaps? Those cans of expanding foam are not cheap, pretty hard to control and I've not had much luck on revisiting them so end up a single use unless you're better than me at cleaning the nozzle.

Posted By: Sam.Spoons
Date Posted: 08 Oct 17 at 7:23pm

Builders expanding foam is unsuitable for this job (and, like DD I've never had much success reusing a can after the first use). Two pack PU foam is good for larger voids, I have used it in the past to repair sailboards but even that has a somewhat variable cell size and is relatively heavy but it is pretty much closed cell so does not readily absorb water. But it is also very soft and not what I would use either.

Depending on precisely what you are doing with it, epoxy and micro balloons would also be my suggestion, it is light and sands well but is properly impervious and hard wearing (which expanding foam is not).

However, the exposed foam in your DB case, is it there to fair the case or is it that the DB has worn away the skin layer through to the foam core? if the latter you are probably going to have to do a more sophisticated repair or you'll simply be storing up problems for the future.

-------------
Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"

Posted By: GarethT
Date Posted: 08 Oct 17 at 7:41pm

Is a big wide (fore and aft) case designed to allow the DB to pivot. Now everyone packs it out with foam to the db just goes up and down. I just want to tidy up the bottom end.

I'm not sure if anything other than 'foam' is allowed for packing. Can't find anything specific in the class rules.

Posted By: piglet
Date Posted: 08 Oct 17 at 9:00pm

PET foam is very resilient and can be stuck in with a bit of epoxy, or chewing gum. Doesn't take up water either.
https://www.ecfibreglasssupplies.co.uk/product/airex-t90-100-foam-10mm

Posted By: Riv
Date Posted: 08 Oct 17 at 11:09pm

Builders foam is really cheap (sometimes £3 a can ) and is easy to apply but weak. It crushes easily. If you don't mind redoing it several times a year it will be fine........I always reuse a can by taking the nozle assembly off and poking a screw down it. The foam solidities around the screw and when you want to reuse it pull the screw out. Always blow through the nozle assembly after use to remove the foam. The only problem I have with the can is that they go flat quickly after the first use but this seems random, depends on each can.Do it, cheap, quick and easy to remove.

Posted By: 2547
Date Posted: 09 Oct 17 at 12:31pm

Originally posted by GarethT

Is a big wide (fore and aft) case designed to allow the DB to pivot. Now everyone packs it out with foam to the db just goes up and down. I just want to tidy up the bottom end.

I'm not sure if anything other than 'foam' is allowed for packing. Can't find anything specific in the class rules.

I believe the class rule says it has to be compressible so that there is not too much damage when you run aground.

The Tasar case is a pigs ear ... I believe the Aussie's have now manufactured inserts that can be fixed into the slot now such that it turns the rectangular slot into a profiled hole that matches the daggerboard.

I can't find any details about this on the webs and as ever with the Tasar class the Aussies seem to control what happens and then not tell anyone ...

The Tasar is the best 2 person boat that never caught on in Europe ... shame ...