polystyrene foam

[michael howarth 1Participant @michaelhowarth1]

I am building a steam launch based on a Vospers Fire Boat hull which I picked up for next to nothing at a car boot sale. The bow section is sealed off so there is no way to get in there and fibreglass it inside or indeed to seal it with resin. Is there any virtue in filling that section with expanding foam. My thinking is that should a leak materialise it would form a barrier as well as providing a bit of strength in a collision. The downside may be that if it does get wet it might hold moisture which could cause rot. I intend to seal and fibreglass the rest of the hull inside and out. Any thoughts appreciated.

Mick

[michael howarth 1Participant @michaelhowarth1]

does it have role in filling cavities.

[Ray Wood 3Participant @raywood3]

Hi Micheal,

I wouldn't worry to much about water getting into that space, if the outside of the hull looks well finished and no cracks or holes visible. Expanding foam is so powerful it may blow the deck off !

If it's the old Aerokits Crash Tender they are pretty strongly built you don't need loads of fibre glass inside and out, its not going to live in the water so will dry out fine.

Regards Ray

[Malcolm FraryParticipant @malcolmfrary95515]

The notion of putting foam in implies an access hole, even if there isn't one there yet. Since foam can act as a sponge or come back to life and pop the deck off, better to use the hole to act as a vent/drain should any water get in there. Site the hole where it can be used as a drain, hide it under a deck fitting.

[michael howarth 1Participant @michaelhowarth1]

Thank you gents. A couple of very reassuring answers which will also save me time and effort.

Mick

[ashley needhamParticipant @ashleyneedham69188]

Sorry it is a bit late but two of my boats with sealed compartments have (oddly enough) recently suffered hull cracks/splits/tiny holes and if I had been less vigilant they may have gone unnoticed and left water in these spaces, possibly for a considerable period of time, leading to internal damp issues/flooding/sinking.

I have cut holes in the internal bulkheads to a) let out the water and b) to ensure they have some ventilation.

I have been round the fleet now and drilled holes in similarly sealed bulkheads, just in case.

Generally speaking I seal these areas before closure, but you cant check later on…..

Ashley

[Chris FellowsParticipant @chrisfellows72943]

Ashley

Are they pretty much airtight spaces? Just wondering if the recent hot weather has caused the air to expand and caused the cracking? If not that could just be due to expansion and contraction of the timber.

I've got a boat where the paint has cracked off a little underneath the rubbing strip. It was in a bedroom that got very warm a few weeks ago and  I reckon caused some expansion. I now move the boats out of that room on hot days.

Chris

 

Edited By Chris Fellows on 28/08/2019 18:53:39

[Colin BishopModerator @colinbishop34627]

It's usually changes in humidity that causes movement in timber. If it dries out then it shrinks and vice versa.

Not a great deal you can do about it really.

Colin

[Ray Wood 3Participant @raywood3]

I keep my boats up in the loft which is like a furnace during the summer, no noticeable effect on the paint mostly Humbrol and yacht varnish.

Regards Ray

[ashley needhamParticipant @ashleyneedham69188]

Cracks will occur, my boats in question were over 10 years old.

Ashley

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