Expanding foam - Advice please

[DavidofMersea]

I recently bought a wooden Enterprise with inflatable buoyancy bags. It is difficult to varnish inside the bow, and I wondered about standing the Enterprise on its bow and filling the space under the foredeck with expanding builders foam. Not only would this save a difficult varnishing job, but provide extra buoyancy - Is this a good idea?

 

[DinghyMan]

Don't think foam would do it - unless you get the proper non-porous stuff but some wooden Ents have the bow blocked off with a ply panel with a couple of small hatches in it to let the water out after you've capsized it a few times.
I sprayed the inside of mine but that was also because I'd cut the deck section out around the mast foot for some repairs - as you say a pig to get in and brush paint varnish.

 

[Lakesailor]

Stop wingeing and get on with it. You can box off the bow area to create a buoyancy tank.

This was my Heron

Stripping and varnishing the inside of a dinghy is the worst job there is.
You need to put an access port in it to let it dry out.

 

[DavidofMersea]

So how long did that job take you? How much did it cost? and how do you get rid of the damp and varnish inside the bouyancy tank? and why is this better than my proposed idea?

 

[snowleopard]

I did a trial with builder's expanding foam immersed in water for 6 months and it didn't absorb water. It would however cost a lot to fill a hole that size and you must be sure never to leave it to set inside a sealed compartment as the pressure generated would be enough to force the ply apart.

 

[Lakesailor]

It was a rebuild and the tank was already built in. It was in fact, snuff-dry inside. I re-varnished it and re-decked the boat.
Didn't cost a lot. Just time.

 

[vyv_cox]

I can't see how filling it with foam will give more buoyancy than an air bag? The contents of an air bag are 100% air, whereas foam is 90% (?). Personally I would varnish or otherwise coat the bow volume and replace the air bag.

 

[mickshep]

Hi David, I wouldn't do it. If any water at all got into the tank (and it will at some stage)it would work it's way up between the ply and the foam and drying it out would not be possible, This would rapidly lead to rot starting, A pal of mine used this method to fill a difficult to get at void behind aboard his Ply built cruiser, (Lysander 17????) , within 5 yrs the area treated was rotten to the core leading to major re-building work, Regards, Mike.