bralex

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I'm building 42" floats and gear for a GP 90" cub. The floats are foam core with a length wise lite ply center bulkhead. The gear is constructed out of 1/2" aluminum tubing that I aero-shaped and tig welded to a aluminum mounting plate for postioning onto the fuse. The floats are shaped similiarly to the Sea Commander SCALE FLAT TOPPED EDO FLOATS. Question: Because of the deep nature of the v-bow design and the compound angles that result, how would you suggest that I balsa sheet the bottom? I plan on using lite glass cloth and resin. Should I forego the balsa and just use extra glass on the bottom? Thanks for the suggestions!

dicknadine

not being a Float man, however I would suggest a layer of 3/32 balsa to the bottom, of the foam and then a layer of fiber glass. the extra strengh shud help in the long run. dick

JimCasey

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dicknadine! You're BACK! I thought we lost you. Good to see you post again.

Bralex: Sheet the floats with cross-grain balsa in front of the step. It will curve around the curves, which are not compound unless you did a lot of whittling when you made the floats. A single layer of light glass cloth is still a good idea. also, aircraft ply on the bottom for 2 or 3 inches in front of the step instead of balsa sheeting.

When I break floats it seems always to be at the step. I have taken to putting a coupla strips of carbon fiber on the sides of the floats to bridge the high-stress area just above the step.

bralex

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Thanks for the great input. What type of glue would you recommend? In the past I've used 3M 77 and expoxy. Any suggestions?
I included a pic of the floats. Thanks!

bralex

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Here's a pic of the gear.

evan-RCU

That's going to be real hard to sheet. I would fiberglass them with some medium glass cloth, don't worry about the weight. As Jim said though you should put more reenforcing in it but not sure how, nice lines to them....

bear 57

Bralex:-
Not sure how dense your foam is, but in my case I use the pink and blue insulation foam. I would cover the top and sides first with 6 oz cloth and epoxy resin. I then would trim the sides right down to the edge of the float. The bottom would be done next with 6 oz cloth with a little overlap left on the edge. Keep adding your resin and lightly sand in between coats until the weave is filled. Oh, I usually thin the resin to the consistency of a little thicker than water. The keel forward of the step would get a second strip of cloth about 2 inches or so wide. This is a high wear area and needs a little more protection.

Hard to tell from your pictures, but there should be a plate at the step for a little additional support. Also one should be at the stern for water rudder support.

I don't use balsa sheeting and this method has worked on floats up to 60 inches, however if your foam is porous, or less dense you may very well have to sheet it with 3/32 " basla before glassing. If you did sheet you could get by with using lighter cloth .6oz or .75 oz
I am not saying this is the only way, but it is one that has worked for me.
Good luck

JimCasey

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I stand corrected. You DID a LOT of whittling to make the bottom.
Now I'm firmly in the "Glass 'em" camp. Bondo makes a nice filler and it is lighter than resin. Do not let bondo touch the foam. the polyester resin eats foam. Bond the glass to the foam with laminating epoxy or with water-based polyurethane varnish.

bralex

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Thanks for the continued input guys. It sounds like glass then for the bottom. Since I've had limited experience with fiberglass tech, here's another question. Would it be better for the bottom surface to use say one 5 oz cloth layer or two 2 oz cloth layers laminate?

For surfacing the sides and top I was considering either 1/16 or 3/32 balsa, or 1/64 lite ply. I'm thinking that the ply may add more longitudinal strength? I've used the 1/64 before on my first set of floats that are on a LT-40. Great stuff to work with using 3M #77 spray on contact cement. Over either material I'd use a layer of 6/10 oz. microglass.

Thanks Guys!