Grp sheet

[pete]

This is just an idea at the moment but would it be practical to make a couple of GRP sheets about 3-4mm thick ?.

My son was talking about stripping and re-varnishing the deck of his old Solo sailing dinghy (glassfibre hull with a plywood deck), and as it has had a hard life and some of the brass nails are loosening I said it would be better to re ply the deck, but then thought it may be possible to buy sheets of GRP, trim it to shape and epoxy it down to the supports and stringers then refit or replace the rubbing strake. but I have been unable to find a supplier of made up sheet.

My local GRP supplier "Glass plies" does not sell it and could not tell me who does so maybe it is not readily available.

My thoughts were to lay up a few layers of CSM on a flat sheet of thickish ply covered in waxed polythene sheet to the required thickness, a slightly textured finish would be a good thing but may be a bit ambitious.
How many layers and off what weight CSM would be required for a lay up of this thickness..
Thanks Pete

 

[grumpy_o_g]

It's perfectly possible to make them but surprisingly difficult to get it right. To get the right amount of resin on to a largish flat area, roll it out properly and get consistency across the whole area is very difficult without a machine.

You can get sheets of fibreglass - they're used extensively for printed circuit board but can be bought in heavier/thicker grades too. Google G-10 unless it's changed it's name.

West Systems is a good starting point for anything fibreglassy. Contact Wessex Resins, the UK distributor.

 

[TQA]

suppliers

Try these guys http://www.fibreglassmouldings.co.uk/grpfibreglasssheet.asp

I have also bought it from a building supplier maybe Wickes??

 

[oldsaltoz]

You can make sheet fibreglass but the best finish is to use glass as the base, just wax it, apply gel coat and add fibreglass, about 4 layers or 300 gram bi directional cloth should be plenty.

However given the task you describe I would thin some epoxy with 30% Methylated Spirits and apply wet on tacky to soak into the timbers and joints, then apply unthinned resin and lay up with bidirectional cloth, let this cure, sand and clean then add closed Micro balloons and sand smooth after it cures; to finish off I would add a light coat of floe-coat and add a little grit, let this go tacky and apply a full coat.

 

[William_H]

Fibreglass sheet

Fibreglass is not as great as you might imagine. As a deck it will not be very stiff and if thick enough to be stiff will be heavier than plywood. A plywood boat is till lighter/ stronger than a fibreglass boat. However of course fibreglass lasts longer and can be molded into complex shapes. If you used carbon fibre with clever reinforcing you might get it as good as plywood.
OK you want to use fibreglass CSM. You need to try to mold a convex curve into the deck not flat. You need to add reinforcing sections. Foam battens with f/g over it is good. Use woven cloth layed at 45 degrees to the tight curve to get it to follow the contour of the foam. Each batten might be 1.5 cms high 1.5 cms wide with semi circular cross section. Sort of hill shaped in cross section so the glass cloth can climb it easily. Cloth does not like sharp bends. Cardboard can be used at a pinch to supporrt the f/g in place of foam.
For the basic board perhaps 4 layers of CSM then fit the battens with areas of no more than 25cms between them for stiffness. Use 3 layers of medium weight cloth over the battens. You may be able to leave the edges of the f/g of the board without resin so they can be folded down to attach with resin to the wooden hull. Epoxy is better here but epoxy is no good with CSM. good luck olewill

 

[nimbusgb]

lay up on glass dont try ply and polythene. The polyester resins interact with it and it does not remain flat.

A layup of 2 plies of 300g with a foam sandwich of 3 to 5mm ( airex core mat ) and another 2 of 300g would give you a light and very stiff skin.

THe core mat would have to be placed and segmented so at to provide clearance for stringers under the deck.

 

[BAtoo]

If son wants to re-varnish then i would let him. Be careful of stripper choice - if chemical such as ronstrip then its not good on fibreglass if its gets on that. You/he could re-pin the loose nails etc quite easily.
Next choice wld be to put on new ply -bit tricky to get the profile right with any curve on the deck - but do'able.

I would be very reluctant to GRP it - almost certainly be heavier ad difficult to get a good finish.

 

[pete]

Hi Thanks for all the advice It has given me a bit more to think about

I had thought of laying up on a sheet of glass but it would have to be about 8x4 foot but I understand what you mean about the polythene sheet maybe melamine sheet would do.

TQA I have already been in touch with these people and they sent me a sample of Vandalite, it is almost see through (even the coloured version which is 20% more expensive), the 3mm sample is so rigid it would not follow the contours. It is very good stuff though.

The dinghy deck seems to be well supported below with no large spans between supports I will have a proper measure up next weekend.

Thanks again
Pete

 

[Bobobolinsky]

You can buy glass 8 x 4sheets from the lorry body builders, they use them for translucent roof panels. A Aalco have a lorry body supply division.
http://www.aalco.co.uk/literature/literature.html

 

[penfold]

Saw these on ebay. Maybe of use?

 

[pete]

Thanks for the links, I contacted the seller on Ebay and he was very helpful but I don't think that the 2mm will be stiff enough. He also sells 3mm PVC but I suspect that is also to flexible.
I have looked on the Aalco web site and will probably give them a ring.
Thanks again Pete

 

[ff_nick]

Melamine faced chipboard works well as a mould. There are instructions for making (very large) flat panels on Richard Wood's website.

I think un-cored flat panels won't have the the stiffness to weight ratio you need. Nimbusgb has the right idea - use 80kg/m3 airex or divinycell as a core, 3-6mm thick. I've done very large flat panels this way, with a 12mm core. The lay-up suggested works out at about 2.8kg/m2, assuming 50% resin in the skins and 5mm core, which is about the same as 5mm ply. You could get away with something lighter (say 2x 225gsm/skin).
It is reasonably easy to do. Gel coat down 1st thing in the morning, wait till is gels (2-5h), then the skin, core on straight away, vacuum bag the whole lot. 2nd skin on afterwards.

Pre-planning (and pre-cutting the materials) helps a lot. For a solo you could for example, build reinforcement into the core for cam cleats on the side decks and so on. Either use ply, or bits of thicker, heavier foam (say 150kg/m3, 25mm thick, which will take self-tappers OK for low load cleats).

FWIW though, I'd be tempted to re-deck in ply. It is one of the easiest boat building jobs you can do; by the time you've stripped off the old varnish from the existing decks, you could have re-decked the whole thing (and of course you get the chance to check the deck beams and tank paint). I did my 1st re-deck on a fireball at the age of 17, with zero skills and that turned out OK, not brilliant but water tight and better than re-varnishing would ever have been.

Good luck with it.

 

[seasolutions]

I would also say re-deck in ply, coat the underside with epoxy, and cover the top with epoxy and light (<300g) rovings then paint and it will last forever,

If you want to go the grp route, I would suggest foam, as have other posters.

no need for a mould, lay glass + epoxy on one side of foam only, the resulting sheet will still be flexible. Cut and fit this material to the deck, glass side down, glue and screw into place. Once cured, take the screws out and lay glass + epoxy on top.

result: one piece GRP foam sandwich deck with very little locked in stress from bending, lighter than ply, made stronger where needed by adding more glass, replacing the foam with ply etc