ernest2

hi! i have a problem with my scratchbuild boat. i could not find plywood thin enough to bend to the curves of my boat. thats why i thought of making fiberglass sheet to serve as my sheeting for the hull.
is it possible to make such sheet? if so, is 6oz (200gms) enough as a sheet? i am planning of making a thin sheet that serve as flatform and then, when the boat is fully sheeted by the thin sheet, i will then add additional layer both inside and outside.
i am using 200gms fiber cloth with polyester resin.
thanks!
ernest

ps2727

Ernest,
It is fairly easy to make fiberglass sheet by waxing a piece of regular glass then brushing epoxy or polyester resin through cloth. I would suggest that you use two or three layers of lighter cloth rather than one layer of heavy cloth. Also be aware that it will bend in only one direction... if your hull has compound curves this won't work. In that case you'll need to think about planking the hull.
Paul

ernest2

thanks paul!
it not really a compound curve so i guess its ok. i just cant bend 1/8" ordinary plywood without breaking it or ruining the frame alignment. 6oz is the lighties available, no hobby grade.
ernest

Deadstik

My Feedback: (8)

ernest,

I am assuming that 1/8" is the thinnest plywood that you can get??? Even 1/8" can be "bent" if properly immersed in an ammonia solution. I would do a search on "forming" plywood and see what comes up. I had an old Warlock that had a plywood fuselage and I assembled the plane like a banana....it had 3/32" plywood sides and to fix it, I soaked it in the bathtub in all hot water for 20 minutes and then "bent" the fuselage back to straight and then let it dry.... worked great.....

If you do the fiberglass method, as said before, please remember that it will only want to bend one way.....and if it is heavy cloth it will not want to bend at all.... I think I'd go with trying to bend the plywood first.... as I'd really not want to try to bend any of my glasswork ....

Let us know how you are doing with the project.... somebody knows everything... and around here, they usually step up...


Dan

Carolina Custom Aircraft

ernest2

ok thanks! i guess i will try the plywood first. yup 1/8" is the thinnest, although its a bit undersize so its about 2.2mm thick only
do you really need to soak the ply in water? or can i just like wet it?

Deadstik

My Feedback: (8)

ernest,

You will need to soak (immerse) the plywood for it to be able to bend. I would do a search on "bending plywood" and possibly cruise the boat forums for information. Just wetting the wood topically will not give you the results you need. Defintely check for further information on your issue. I have used an ammonia solution 50/50 to bend wood and had very good success. Again, research on your part here is the key.... good luck with your project.


Dan

Carolina Custom Aircraft

hoofty

try making a foam blank of the hull and forming the fiberglass over that. that way you won't introduce any pre-load stresses on your frame or risk fracturing the resin matrix of the fiberglass skin. If you don't already have one, a hot wire foam bow can be made for less than $50 and you can use that 1/8" plywood to make the templates for cutting the core. there are a number of threads in this forum about it or you can feel free to ask as most of the people posting in this forum have some experiance cutting foam.

Hoofty


"Take off and flight are optional, Landing is manditory" <-- some smart guy's quote.

ByronRC

My Feedback: (2)

I'm a boat guy myself check this out
http://www.acp-composites.com/
I've been thinking of using this stuff for 1/8 scale unlimited hydros
http://www.acp-composites.com/acp-fs.htm

beenie

My Feedback: (9)

I tried something similar to make the cowling for my Supercub. The full scale cowling is made of sheet metal bent to conform to the firewall and nose bowl. So I figured that I could do the same thing. Wrong. I ended up doing the foam form thing and it came out great. I did use some of the sheet that I made for the air scoop at the bottom. There was a little print through where the I bent the sheet, but I think that could be avoided with the right materials. For your application I could see it working out a lot better than my cowling. It is really easy to make a foam plug and glass it, you don't even need a hotwire, just a knife a saw and some sandpaper.
Ben

ernest2

the foam idea is good. i was thinking about that also, but the problem was i use polyester resin, so it will melt the foam instantly. somebody suggested that i cover the foam with paper and glue, which i think is right.
now if i use the foam idea, do i have to leave the foam in there after fiberglassing?

hoofty

Cut the foam and glass it with epoxy and one or two layers of 3/4oz glass. once fully cured, polish, wax, and PVA the foam "plug". lay up your hull with any resin you choose and let cure. the foam plug will pop right out as long as you prep the surface well (and you have all positive angles). a vacuum bag will help get the glass to conform to the plug without any air bubbles. I can do a full tutorial for you if you like.

Hoofty

ernest2

hoofty, the problem is, i can only get polyester resin over here. so if i do the foam method, i will melt the foam if directly applied. if i will cover it with paper, how will then the fiberglass adheres to the frames of the boat.
i was really leaning towards planking, maybe make 1" or 1-1/2" strips.
thanks for that offer, i hope i will be able to ask you few questions once i get back on working with it, been busy with work.
ernest

slopemeno

My Feedback: (2)

Cover the foam with packing tape. You know, like the 3M kind for packages? Once you have the tape on iron it gently to take any wrinkles out, then 'glass it. The tape will keep the foam safe from the polyester resin.

hoofty

The packing tape might work. Just be carefull not to heat the foam too much as it will melt and distort your plug. another meathod would be to fill the pores in the foam with a high solids paint and make a female plaster mold. Just build a dam around the plug with scrap wood or foam sheet, pour the plaster over the foam and let cure. if you mix chopped fibers into the plaster mixture it will hold better and be less likely to crack. just be sure to cure the mold in an oven to remove as much moisture as possible.

Hoofty

ernest2

well, i did the plywood sheeting only, and so far, it went ok. i was able to bend the ply just as well, i hope it will hold up. now, i know most of you are into planes, but i will ask this anyways, do i need to cover the outside with fiberglass? or polyester reisn only will be ok. i don't want to add unnecessary weight anymore.
thanks! i will do the fiberglass molding in the deck of the boat.

hoofty

I would highly suggest using the glass. Boats are subject to some pretty rough conditions while plowing through choppy water, and the resin will only seal the surface of the wood. The fiberglass will help keep a uniform seal around all the seams as well as give the hull a great deal of strength with only a little extra weight. I would suggest using some 3/4oz cloth. Use a fine mist of spray adhesive (3M 77 or simmilar) to tack the glass in place. mix your resin as per the manufacturer, and spread with an old credit card or playing card. use a disposable foam paint roller and roll it over the entire glassed surface over and over to even out the resin. blott up excess with paper towels or toilet paper. once cured, sand lightly with fine grit paper (320 or finer), fill the weave with bondo, sand and paint.

I know it sounds like a lot of work, but a great product usually is.

Hoofty

ernest2

hi hoofty, thanks for that info. it's not really, i have tried that in my airboat hull. now the problem is the lightest glass i can get is 200gm, that's about 6oz if im correct. there is a surfacing mat available thats about 60gm, thats about .50-.75oz i think, but its not strong compared to the cloth.
now i'm torn between these, cause 6oz will certainly add lots of weight.
ernest

Campy

My Feedback: (1)

I have never tried covering the plug with paper. When I have made cowls, I carve/sand the foam, then cover it wiith ECONOKOTE (low temp film - I use scrap pieces). Then I either wax the covering with 10 - 12 coats of paste wax (yes, 10 - 12 coats ) or use a PVA mold release (dissolves in water ).

If the PVA is not available and/or the waxing seems like too much work, after the glass has cured for a couple of days, just make an X through the Econokote on the open side and pour in a couple of ounces of gasoline, go have a cup of coffee and come back in about 20 minutes (Obviously, you do the gasoline thing outside ) and pull out the remainder of the film and "sludge". Wash the glass with soap and water to get rid of any gasoline and let it sit for several days to harden up. When you initially take the foam out the glass part is going to be soft and malleble so you will be able to do any "fine tuning".

ernest2

hi! my local resin distributor said that they have a glue that can be used as covering for the foam. so i think thats what i try.
now another question, can polyester resin be thinned?

charlieoneseven

Plywood is sole here in 1/64th, 1/32, 1/16 thichnesses stateside in most hobby outlets. Yes polyester resin can be thinned with acetone before adding the catalist is best. Test the foam and resin before melting your project we prefer epoxy over foam but you have to go with whats on hand I supose
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