I need to make some flat sheets of fiberglass.
i have a nice tabletop surface that is flat, but i dont know what material i can lay the fiberglass on, while being able to remove that material from the dried finished sheet.
I may also want to do some things that have 90 degree bends or other curves, so a technique for forming the fiberglass would be really useful.
If the surface is not smooth cut a piece of mason board big enough to cover the surface. Spray a couple of layers of PVA http://en.wikipedia.org/wiki/Polyvinyl_alcohol over the surface of the mason board and lay up your flat fiberglass panels. PVA washes off with water but is impervious to almost every other solvent that I ever tried to remove it with. PVA sould be available where you buy the fiberglass supplies.
Use two pieces of aluminum sheet hopefully with surface with a shine that will transfer to fiberglass finish.....wax 2 or 3 times with carnauba wax and layup, 2 or 3 times so don't miss a spot, layup, gel coat (mix teaspoon of color??) then matte and cloth as needed for strength, then put aluminum second piece on top to seal from air, waxed of course, put lamp near it so u can get 70 - 90 degree setup....have fun......for curves can layup on styrofoam with epoxy or urethane foam with regular resin and hotwire foam to finished shape to form layup, use cutting guides made from metal or wood scrap and cut your curve or form, use nails or screws into foam to locate cutting guides....put wire across bow or U box fixture or frame and tie power leads to end.....put mixture of resin/hardener and microspheres on foam first for layup mold finish and then wax for use as mold........hotwire is guitar wire or .03 wire from hardware store and dc power source.....consult experimental aircraft construction for hotwiring guidance.......aircraft spruce has variable unit although pricey and how to hotwire manuals.....can use battery but with some high wattage resistance of some sort or wire will immediatly melt....twaaaaanngg ......or curve sheet with heat gun and advice from other members on that, only done lexan with heat gun
Posto: can cut curve shapes from plywood and nail aluminum to it for molding form, don't necessarily need aluminum on top of that to cut off air....but try to make side against aluminum your finished side, apply inside or outside of aluminum curve
hotwire crapola + microspheres on botched wing attempt
Mike O- Summit,Glen,Rd Atlanta,Rd America,Brainerd, Bryar,LimeRock,New Jersey MP,Trenton,Phoenix,Charlotte, Vir,Mid Ohio,Riverside,Buttonwillow,Vegas,Nelson,Pocono,
West Palm,Mosport,Mt Tremblan,Bridgehampton,Heartland
Last edited by Modo; December 11th, 2011 at 10:18 AM.
I had a bad experience using the wax paper trick with polyester epoxy. The MEK catalist melted the wax and then bonded to the paper, or thats the best explanation besides I had some bad wax paper. Using West Systems epoxy and 2 part optical epoxy (optical at work, not on race car) I have used a few mil thick plastic sheet and .005" to .010" mylar sheet. Plastic usually releases well, some mylar has stuck to epoxy but adding heat from heat gun while pealing the mylar off helps, as does using mold release spray or wax.
lots of info and tips can be found if your Google Foo is strong.
::edit:: the wax paper did work with regular 2 part epoxy, just not the polyester
My father has made more than a few composite pieces for a track day car project of his. That includes wings modeled after the VD std. rear main plane.
That said, i've used two sheets of glass (old window pains), cheap dollar store hairspray, and some bricks to produce some rather nice sheets of composite. I simply sprayed the glass (the windows) with a light coating of hairspray, let it dry. Cut my fabric, mixed the resin, laid the fabric on the bottom sheet of glass, impregnated it using a putty knife, then put the second sheet of glass on top. Set the bricks on the top of and let cure. Excess resin was squeezed to the sides of the fabric. A little light prying with the screw driver was enough to release the sheets of glass. The resin, i've used both epoxy and polyester doesn't stick well to glass in the first place and the cheap hairspray (basically pva) is a great releasing agent to boot.
This same methodolgy applies well to wooden molds. Which may be a better solution in the case of your right angle requirements. Though, use of carnuba is helpful too.
As for the close but no cigar wing attempt, build an outside mold that is open at the trailing edge out of aluminum flashing and wood supports. Position it so that leading edge of the wing is in the bottom of a V-Shape mold. You build into the mold the upper and lower curvatures of the wing surface but you leave the leading edge radius slightly large, and the trailing edge of the mold open. I'd say give the trailing edge opening a 6 inch gap so that you can work within the mold handily. Impregnate the fabric outside of the mold, coat the mold the hairspray, then lay the fabric. Be careful not to over saturate the farbic as it will make bending the wing for trailing edge bonding impossible later (due to resin sag). Once the pieces have cured you trim the trailing edge appropriately and then bond it using resin. This is my father's method and he was been very successful at producing wings that required no filling.
Chris Livengood, enjoying underpriced ferrous whizzy bits that I hacked out in my tool shed since 1999.