Waterproofing inside hull

[Tony Taylor 1Participant @tonytaylor1]

Any advice please on waterproofing inside of hull. I've looked at epoxy finishing resin as a solution but would this need thinning, in which case, what with. Cellulose dope has been suggested but worried about shrinking. (Going back to my model aircraft days)

[Tony Taylor 1Participant @tonytaylor1]

[Dave MilbournParticipant @davemilbourn48782]

I thin epoxy finishing resin about 10-15% with Isopropyl Alcohol which can be obtained on the Internet. Buy at least 99% pure – the stuff is hygroscopic and any significant water present will affect the resin.

DM

[Paul TParticipant @pault84577]

A can of spray varnish works very well and being an aerosol it gets into every space and corner.

[mark69Participant @mark69]

Hi Tony nothing wrong using polyester resin in the packs you can get from any moter factor, doesn't need to be epoxy to waterproof inside the hull and it will be fully waterproof once cured ….mark

[Tony Taylor 1Participant @tonytaylor1]

Thanks Guys for your help. This is only the second time I have used the forum. Must say it's invaluable , everyone so helpful for novices like me. Will now study your advice. Regards T.

[Martin Field 1Participant @martinfield1]

Sanding sealer, followed by varnish or just varnish if the insides are in good nick, but I use epoxy because I have it around and I never bother thinning it, just slap it on with those dirt cheap Chinese bristle brushes. I like to do it as I build the model, then once the ply skins are on you just need a dab around where they join the structure. Mark's right about using cheap old polyester, but it isn't known for its love of soaking into wood like epoxy is.

It all depends how well your model is built. If very well and there are no gaps, then a good enamel paint (HMG) or

spar varnish should be perfectly adequate. Don't use acrylic for anything except your windows (Perspex)

Martin

[mark69Participant @mark69]

How rude Martin I don't use cheap old resin ,mines always new and fresh you can warm it up by standing a pot of resin in some hot water It will soak into all wood without the need to thin and in any counts the brush cleaner for the resin is a suitable thinner anyways ….mark

[Dave MilbournParticipant @davemilbourn48782]

Oooooo!! Solvents at dawn, is it? I love a good fight!
DM

[Paul TParticipant @pault84577]

Take 10 paces turn and brush but be careful as solvents at dawn tend to be tacky and if you hold your tool wrong you might end up with sticky fingers

[mark69Participant @mark69]

You only need to thin for the first coat same as you would for varnish ,polyester with the right amount of catalyst will not be taken once cured wouldn't be of any use in the marine trade if I did the kits you can buy from any motor factor are ideal and a lot cheaper than epoxy and in my opinion it's not needed for inside a hull .outside it totally different ,a nice Finish what your after then I would use better products . But as always the choice is down to the individual but be careful when using epoxy as the resin to hardener ratio isn't forgiving if you get it wrong it will not cure ,some are 3-1 others are 5-1 ………mark boat builder for over 25 years and have a bit of knowledge of these resins !

[Martin Field 1Participant @martinfield1]

Mark,

I have found that polyester doesn't soak in and stay soaked in very well with most woods, but it is probably good enough for toy boats.

Also, my info is backed up by none other than Dick Clarke of Lake Tahoe, who uses epoxy to glass the bottoms of wooden boats, as lake Tahoe boats need that protection. He says polyester doesn't soak in enough and lets go easily and so uses epoxy, but only with a glass cloth that has been treated to suit epoxy, which "normal" GRP mats and cloths do not. He, of course, will have experimented with all sorts until he found a combination of materials that do the job he charges a lot of money for!

I have never used the model GRP systems as they are overpriced, being small amounts. I wouldn't know if the cloth is treated for epoxy or more suited to polyester as I never use it. My experience is only with WEST or SP epoxies which I am quite happy using at normal viscosity. In fact the WEST technical rep turned his nose up and warned me that they were not aware of the effects of thinning, but at that point (about 2006) they had not investigated the subject. I wasn't likely to upset him as at that point he produced a 25 litre drum of the stuff gratis as their sponsorship of our restoration of an historic wooden canal boat. Now, everyone talks about thinning it!

Martin

[Tony Taylor 1Participant @tonytaylor1]

Thanks to all once again and additional info from Paul and Martin.Trust everyone survived Solvents at Dawn

[Dave MilbournParticipant @davemilbourn48782]

Sorry. I didn't realise I was mixing in with the big boys. I use Z-Poxy Finishing Resin which I buy in very small quantities, like most boat modellers do. Its resin:hardener ratio is 1:1. I have no experience of West or SP resins but 25L would be a little too much for me to store (even if it were free).

All I can say is suit yourselves – and may the best man win.

DM

[ashley needhamParticipant @ashleyneedham69188]

Several well known contributors to MB magazine do not coat the insides of their boats with anything.

Resin of some sort will of course add extra stiffness to a hull as a bonus , but a drop of paint I would have thought is good enough to stop any loose moveable ballast from penetrating the wood.

Clear varnish is my preference so I can see if there are any other issues I should be aware of, but a dozen or more landing craft are still fit after no more waterproofing than several coats of household grey undercoat inside and out.

I have a feeling that you can take the theory too seriously sometimes. Paint is all it takes.

Ashley (usual disclaimer)

[Martin Field 1Participant @martinfield1]

Frankly, Ashley, I think you're right. If I didn't have the WEST epoxy on the shelf from when I did the boat restoration, I probably wouldn't buy any more. Fortunately it lasts for ages. I would probably use a treacly varnish from the pound shop! Failing that, waterproof any unknown or iffy joints (we all have them sometimes) with Pound shop rapid epoxy, then paint or varnish the rest of the structure. I would never leave it unfinished as ordinary storage damp can get into the wood, so some sort of waterproof paint is needed, hence my advice for enamel paints.

Dave, nothing free is too much to store! And it was a full 70 foot narrow boat we were restoring!

Cheers,

Martin

[mark69Participant @mark69]

Nice to see you have decided what you useing now Tony anything is better than nothing you didn't say what your building have you started yet ? …mark

[Martin Field 1Participant @martinfield1]

BTW, it helps if you do it as you're moving along with the build as I have here. Nice smooth skin of epoxy (or Mark's smelly old polyester (<GG&gt slapped in there with a cheapo Chinese brush (from the Poundshop!)

Cheers,

Martin

[Tony Taylor 1Participant @tonytaylor1]

Hi Mark. I'm building Aerokits Sea Commander. It's been over 40 years since the last project. How things have changed in that time. I've just completed the hull skins with a little difficulty but pleased with the overall result. Am inserting a few changes to the kit by having mahogany decking. Propshaft now in along with rudder. These I shall remove before waterproofing. Bit behind schedule, grandchildren very impatient, but at my own pace!! Regards Tony

[Ian GardnerParticipant @iangardner62867]

I also like Z-Poxy resin. It's very easy to use and sands well and can, as Dave says, be bought in relatively small quantities. I have used SP and West Systems epoxy for model and full sized boats and it goes in well if heat is applied, gently, in the form of a hot air gun. This makes the epoxy more runny. Don't overdo the heat or you will end up with melted bristles mixed in with the epoxy- don't ask how I know this.

I would alway finish the inside of a boat with epoxy as wood has a habit of moving about and I find it tends to stabilise it. I always finish the inside with a coat of paint as well just because it looks neater.

Epoxy will do the most thorough job of waterproofing in my opinion..

Regards,

Ian

[Martin Field 1Participant @martinfield1]

Here, here, Ian

Martin

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