New ply boat roof, poly or epoxy ?? Help ?

[Birchwood33]

Hi all,
Unfortunately I don’t know which to use but this is the criteria:
1) 2m x 2.5m
2) loads of internal 90 angles requiring fillets with ridge for windscreen and big rectangular sun screen, external angles will be rounded
2)Will be made in a garage and have to be moved an hour by trailer and manual put on boat
3) want it stromg as possible but I realise that the structure must support the weight
4) May flex a bit during transporting and mostly getting it on top of the boat ?
What would you do, epoxy and cloth or polyester resin and csm 2x 450g

 

[Birchwood33]

One shop says go for polyester resin 2 x 450g as it will bond fine to plywood and be less expensive.
Another says to go with epoxy and one layer of cloth. ?

 

[Birchwood33]

 

[john_morris_uk]

Epoxy every time. It sticks much better. Good layer of quadraxial cloth and well wetted out and rolled on. Note that the cloth won’t go round sharp corners.

Vacuuming the cloth on with peel ply and the appropriate blanket is the Rolls Royce solution.

 

[Poignard]

I resheathed my plywood coachroof, hatch garage and sliding hatch about 7 years ago using WEST epoxy and tapered edge cloth.

Sheathing with WEST SYSTEM epoxy

Other makes of epoxy are available but as I have always used WEST products with good results I can recommend them.

 

[Birchwood33]

Epoxy every time. It sticks much better. Good layer of quadraxial cloth and well wetted out and rolled on. Note that the cloth won’t go round sharp corners.

Vacuuming the cloth on with peel ply and the appropriate blanket is the Rolls Royce solution.

I have to paint the paint at some stage, changing colour to white from a baize colour. The rest of the boat is GRP and gel coat. What would I paint on the epoxy roof. I like the idea of vacuum and peel ply also.

 

[Poignard]

I have to paint the paint at some stage, changing colour to white from a baize colour. The rest of the boat is GRP and gel coat. What would I paint on the epoxy roof. I like the idea of vacuum and peel ply also.

I have painted mine with International Primer followed by International Interdeck

Interdeck Boat Deck Paint | International

 

[john_morris_uk]

I have painted mine with International Primer followed by International Interdeck

Interdeck Boat Deck Paint | International

Agreed. You might need to fill and fair first if you've vacuumed the glass cloth and epoxy on. The peel ply leaves a very slightly dimpled surface.

 

[Birchwood33]

Agreed. You might need to fill and fair first if you've vacuumed the glass cloth and epoxy on. The peel ply leaves a very slightly dimpled surface.

Hi, what does fill and fair mean

 

[john_morris_uk]

It means spread low density filler (eg micro balloons mixed into epoxy) all over the surface and then sand it smooth. If you really want a fair shape you use a 'long board', If you're happy with the shape, then use a random orbital sander.

Youtube will show you I expect. (If I get a minute I'll find some video examples.)

edit: Put long board sanding into YouTube https://www.youtube.com/results?search_query=long+board+sanding

lots of examples.

 

[TernVI]

How strong is this supposed to be?
Are you going to expect to stand on it?
A thin skin of GRP won't be very stiff, you're relying on the plywood.
Good ply will be heavy and expensive.
Maybe consider foam sandwich?
you should decide whether you are building a wooden deck and sheathing it in GRP or a GRP deck with some wooden formers.

10sqm could eat up quite a few £££ in epoxy.

A wooden deck with epoxy coating, with a layer of glass cloth to add impact resistance is a valid thing.
A grp deck is another concept and is best done as a core and sandwich IMHO.
Either needs some design thought to be strong enough to take weight in a fast boat.

If you do it in epoxy and heavy cloth, it will take some work and skill to get it looking good IMHO.

 

[PCUK]

I recently built a new wheel shelter using West epoxy and bi-axial cloth on the outside. I used stainless staples to keep the cloth tight and in place round the corners and hammered them in to stop them showing. Two 4mm layers of ply bonded together for the roof to allow smooth strong curve. 4mm ply stiffeners inside all totally encapsulated with polyester resin and chopped strand may for economy as this should not get wet!

 

[TernVI]

I recently built a new wheel shelter using West epoxy and bi-axial cloth on the outside. I used stainless staples to keep the cloth tight and in place round the corners and hammered them in to stop them showing. Two 4mm layers of ply bonded together for the roof to allow smooth strong curve. 4mm ply stiffeners inside all totally encapsulated with polyester resin and chopped strand may for economy as this should not get wet!

Looks good!
You are the forum expert now....

 

[PCUK]

Thanks. regarding your strength comment to the OP this roof takes my weight without any flex due to the egg-box like 4mm internal stiffeners.