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[Builder1]

I have used glass tissue to cover a plank on frame balsa hull but I am now considering putting GRP matting over the tissue. My question is :-
Is this OK to do and if so can anyone offer any advice on how best to do it.

I am a real beginner so please try and keep it simple

Many Thanks

[tobyker]

It is qute feasible, but the resulting surface will be rougher that Yogi's trousers. If you need to strengthen the hull with mat, can you fit pieces inside?

[HS93 (RIP)]

no problem at all I am helping someone do a large boat now read this  http://www.rcgroups.com/forums/showthread.php?t=329811  it will show how it is done I have been doing it for some time using this method and it works well , you use cloth that is available from deluxe materials   http://www.deluxematerials.com/products_building.html   Lightweight Fibreglass Cloth,and   Aeropoxy you can just use ordinary epoxy but it must be the slow setting unless you are superman, cut the cloth a lot bigger as it shrinks..

Peter

[Builder1]

Many thanks to all for the response. Just one thing,if I do put the grp over the tissue surely I can sand it down to a smooth finish. To be honest I need to strengthen the outside of the hull and hopefully cover up some of the more glaring mistakes!!!

[Colin Bishop]

Do bear in mind that applying resin over already cured resin does not produce a chemical bond, you will be reliant on a mechanical bond with what is already there so you need to roughen up the existing surface. Otherwise you may simply find you've made a mould!

Colin

[John W E]

Hi builder 1

First of all what type of hull is itthat you have made? is it a fast plaining hull or is it a slow displacement hull such as a tug?

If it is a fast speed boat - the hull will have to be kept light -so adding extra weight by adding layers of choppedstrand mat or woven cloth will not help one way is to sand the out side of the hull with coarse sand paper by hand to give a good key then fill with car bodyfiller unevenness then when that is dry sand the hull smooth then reapply a topcote of tissue and resin allowing that to dry and then sand and polish if you have sanded the balsa to thin then put a layer of tissue on the in side of the hull to seal and strengthen .  When real hulls are made, say for racing yachts and lifeboats - at one time they used end grain balsa wood blocks sandwiched between two thin layers of glass fibre mat.  The strength is in the balsa being impregnated with the resin and not all in the glass fibre mat

Hope this will help

Aye john

 

 

[HS93 (RIP)]

If you just want to seal the hull the method I suggested will work it is also extremely light as the product is used for skinning model aircraft, I am helping someone do a 46" fire boat at the moment that we want to keep light, different people have different ways of doing things. this is what I use.

Peter

[red181]

I dont bother with all the bodyfiller route of doing it, too much work sanding it all down, and the mess, and extra weight, and you have to be quite good at it to get a good result. I use very light cloth as mentioned earlier from deluxe materials, I think its 5g weight, the lightest stuff, use a coat of resin, which is only wafer thin applied with a piece of plastic card, get the cloth on it before it goes off, and the another thin coat of resin. This seals the wood, and is a rock hard finish when cured so if you hit something (like the side of the lake ) it wont crack or fall off!)

Sand it flat with something like 80 grit paper using a block, relatively easy as you can visually see the high spots, then prime and usual paint process. This process also stops the wood delaminating over time. Personnally, I dont like sealing the inside and outside, so just use a clear satin varnish applied with cloth on the inside, I believe the wood has to breathe, so if its sealed on the outside, the inside does not need doing, in my opinion. Everyone has their own preference, thsi is mine

Funnily enough, been doing it tonight




First pic shows cloth prior to rubbing down, second its now rubbed down using block and 80 grit, nwext step another coat of resin, rub down, with 80 grit, then work with 100 for priming stage, then its the hard work, finishing with 1000 grit wet and dry to achieve a mirror flat finish Hard work, but the preparation makes the job

[Builder1]

To Red181

Thanks for the info. What type of resin do you use.?Is it the same resin as would be used for GRP??

Regards

[red181]

This is what I have done the hull with, finished rubbing it down to paint prep and primer stage tonight. I gave the wromng cloth weight, previously, its pictured below. I wanted a heavier resin than I normally use as the hull is 40 yr old renovation, so didnt want leaks, It will be something much lighter for the deck from deluxe materials, they supply the rc plane builders, so its very light and easy to use




The cloth




sanded with 80 grit for a nice key to prime





Did the rear of hull tonight, resin on the bare wood,




Cloth on the  resin, flattened out with a plastic card, then another coat of resin, then  left to set



Its quite an easy process, but a bit messy and time consuming as I now have to leave it to gio hard before rubbing down, but its worth the effort as this hull will now be water tight and solid, and the wood will not delaminate or get damp (hopefully!)

[HS93 (RIP)]

You need Aeropoxy, http://www.deluxematerials.com/products_building.html  it is what Paul used on the last boat it is a lot thinner and easy to use, must be  as aero modelers can use it 

Peter

[red181]

Cheers Peter, could not remember link! how is the workshop floor since our last glassing session last week

[HS93 (RIP)]

dont know not been out there

Peter

[martno1fan]

Whatever you use ALLWAYS seal the inside or you are asking for trouble,plywood doesnt need to breath  Seal it and seal it well inside and out.
Mart