Glueing foam buoyancy into place?

[Kelpie]

I'm planning on using some closed-cell polyurethane foam (sold in sheets as loft insulation) as additional buoyancy in my Wayfarer. The plan is to install is underneath the decks where it will not affect storage space too much.
I'm not sure how to attach it to the (ply) deck. The foam is very light, with a foil face on either side. I'm not sure what will stick to the foil, and I don't want to use something that eats away at the foam!

On a related topic, is it possible to buy closed-cell expanding foam in a can?

 

[Tillernut]

Many years ago I had a Freeman MoBo and the core between the decks had broken down, it was like walking on a trampoline. As I work in the construction industry I used Builders foam. You can by an applicator gun, £10 -£30, depends where you get them. Be sure to ask for 'gun grade' foam plus a tin of gun cleaner. What I did was to drill holes in the underside of the decks and then inject. As this stuff is supposed to expand to approx 40 times you can see the possibilities. If you get fire grade foam (pink) this seems a little denser. Cover things over with protection, it can be a swine? Don't take the canister off until it is empty then put the gun cleaner can on and spray through. It'll be dry in a couple of hours easy. Don't forget, if you are using it between layers it does expand so make sure it doesn't dry lumpy.
I had this boat for seven years and it held up OK for all this time.
Good Luck
Terry

 

[fireball]

The problem is that it is likely it will soak up water as it is supposed to be insulation and not buoyancy - you need closed cell stuff for buoyancy.

 

[Kelpie]

I'm well aware of the closed vs. open cell issue. I've often found lumps of waterlogged polystyrene on the beach which are open-cell and utterly useless as buoyancy.
The foam I'm planning on using is polyurethane closed-cell. I've tested some in my bath and it doesn't appear to soak up any water at all.

The issue is how to stick sheets of it to the underside of a ply deck.

 

[wallacebob]

Had similar plans for my old ply Gull a few years ago; the "No more nails" waterproof type, or polyurethane wood glues seemed best at the time, but I was advised against it by old salt who had had experiences of foams in the past. Stops breathing of timber and can increase rot rate, not an issue for you with GRP I know, but removal in future may be difficult if you need to do repairs?.
I used old wine box bags to fill all the available spaces: free bouyancy bags from local pub!, and good fun getting rid of the wine too.

 

[Kelpie]

Thanks for that, I hadn't thought about moisture etc. My boat has a GRP hull but wooden topsides so this could be an issue.
Wayfarers are supposed to have some foam buoyancy in the tanks already- for some reason mine doesn't. The class rules specify the volume that should be installed and I'll use this as my guide.

Fitting the foam to the underside of the deck is certainly the most desirable solution from a stability and stowage point of view. Bags or other solutions would work but be less easy to live with. I wonder how big a problem it is to cover up one side of the ply deck?

 

[Cliveshep]

I'm planning on using some closed-cell polyurethane foam (sold in sheets as loft insulation) as additional buoyancy in my Wayfarer. The plan is to install is underneath the decks where it will not affect storage space too much.
I'm not sure how to attach it to the (ply) deck. The foam is very light, with a foil face on either side. I'm not sure what will stick to the foil, and I don't want to use something that eats away at the foam!

On a related topic, is it possible to buy closed-cell expanding foam in a can?

Why not take the best of the solutions offered here and do it by upturning the boat (I assume a Wayfarer is a lightweight dinghy?) and using spray foam s[ray all over the underside of the deck which with the boat upside down won't drip on you. Like the man said, use polyurethane foam from a gun, clean the gun off with gun cleanere after and then hire it out to the rest of the club. One can gives a huge amount of foam and you might well want to spray only a little at first, use an old pallet knife or similar to smear it wet all over the deck and then it will guarantee the bond when you then top up. It cuts easily when cured so if it's a bit like the mountains of the moon you can easily shave it down. Also, it is moisture cured so if it's damp out all to the good.

Alternatively, you can stop at the "smear it all over" bit, peel off one layer of foil and bed the sheet foam you have into the wet foam. It sticks very well to spray foam, and I successfully re-foamed a refrigerator that way that required a foil-back foam insulation.

 

[Quandary]

Fixing Insulation

Re. the concerns expressed above it occurs to me that you could choose to fix the foam sheets mechanically. (Though if it were mine I would simply just glue it with waterproof Gripfill or similar as it would seem to be no worse than sealing with paint)
The type of insulation is commonly used in inverted 'cold' flat roofs where it is exposed to wind uplift but can not be fixed through the waterproof membrane which is also acting as the vapour barrier, then it has to be stuck down, and wind uplift can be great.
In traditional flat roofs however, the membrane goes over the insulation and it is fixed to the deck with long nylon type screws with big heads or washers, the membrane is then usually glued to patches held down by the screws. Similar techniques are used when applying external insulation to solid walls.
So if you want to make it removable you could fit some light timber battens beneath the deck and then secure the rigid foam slabs to them. The resulting airspace may be a benefit? I presume that the problem of detachment arises if the boat is inverted when full of water when the forces would be considerable, but is a Wayfarer ever likely to fully invert?
This type of thing is commonplace in construction and an insulation supplier should be able to offer a choice of suitable non corroding fixings, but it is a while since I was involved with this so I no longer have any product literature. There were contractors retro-fitting insulation all over the country but perhaps the task is now completed?

 

[Kelpie]

Update

Thanks for the messages- the closed-cell in a can would seem like the best approach, butin the meantime I have just gone ahead and cut the foam sheets to size so that they are a nice snug fit between the beams that run under the deck. A bit fiddly but only took me a morning to do.

By the way, I'm being prompted into beefing up my buoyancy following an inversion on the mooring- the boat was flipped by a freak tornado in the night, I went round the next day and saw just a little bit of hull above the water! The aft locker had completely flooded and the boat was sitting on the mast. Ouch.
So next stop, after the foam, is better hatch gasket and catches...

 

[smonard]

I used to have a Flying Scot a large and wonderful American dinghy. These had expanded polystyrene blocks under the seats as buoyancy. It was kept in place a by glass fiber straps. When I bought the boat it had loads of that filthy foam under the seats, took me hours to get rid of it, I needed access to the underside of the side decks. If it were me I'd epoxy some wooden blocks under the deck then screw little hooks into these. I'd then use rope or webbing to keep the foam in place. If you squirt that insulation stuff under the deck you may regret it later should you need access later on. I looked into buying some urethane foam once for a delaminated deck. You can get different densities for different purposes, It would have been quite expensive so I gave the boat away instead. You would need loads of those cans used for insulating around windows.

 

[Tranona]

Thanks for the messages- the closed-cell in a can would seem like the best approach, butin the meantime I have just gone ahead and cut the foam sheets to size so that they are a nice snug fit between the beams that run under the deck. A bit fiddly but only took me a morning to do.

By the way, I'm being prompted into beefing up my buoyancy following an inversion on the mooring- the boat was flipped by a freak tornado in the night, I went round the next day and saw just a little bit of hull above the water! The aft locker had completely flooded and the boat was sitting on the mast. Ouch.
So next stop, after the foam, is better hatch gasket and catches...

Why not just use conventional inflatable buoyancy bags strapped to the deck beams? Cheap and easy to fit and remove.

Personally I would not glue anything to ply in a damp out of the way place like under a foredeck. Paint it and keep well ventilated.