ORIGINAL: doxilia
Hi MattK,
do you have some pictures and/or a brief description on how you go about the carbon matting above and below the wing sheeting?
Is the matting below the sheeting applied with laminating epoxy or epoxy based paint? What type of matting do you use and where do you obtain it from? Does it have a tendency to curl or does it lie flat like fiberglass? Does it tend to shred a bit like 3/4 oz glass cloth?
For the top layer, do you apply epoxy clear paint (mat or gloss - does it make a difference?) first and then lay the matting on top? What tool do you use to insure a tight junction on the sheeting without lifting up the matting?
The end result must look pretty cool. Is it much lighter than glassing? (I know it will be rock solid).
Hope you don't mind the 20 questions.
Thanks, David.
David, I started a thread on Composites Fabrication and Repair section which I called Finishing with Carbon Veil. I have photos there that should help.
Inside the skin is straight forward also: carbon is first layed down with nitrate and the paint is allowed to fully flash a couple days. This does at least two things: it builds practically no weight as it adheres the carbon veil and seals the wood making it ready for epoxy or other (PolyU). I use Pro Set epoxy, 125 resin 229 hardener (various sources; Look under Gougeon Bros) for a very thin viscosity of around 380 cps. It's as thin as canola oil. Working time is over 1 hour so there's plenty of time to get everything aligned. Nitrate is extremely thin onced diluted with solvent and adds no real weight...maybe a couple grams per sheet.
I get carbon veil from ACP, but FibreGlast, CST and AS&S carry it also. I use and recommend the 0.2oz variety; it's very thin and it takes almost no glue to lay it down. On the other hand there is also the 0.5 oz type but don't let the light weight fool you. This material is fluffy and tends to hold much more glue. It definitely has its uses particularly if you vacuum bagged an assembly where the laminate could be squeezed down
After the carbon layup has flashed, I roll the epoxy sparringly thru the carbon and onto the wood. I also "activate" the foam by running the wet roller onto the foam briefly. This removes any vestige of polystyrene particulates providing a better base for the epoxy to adhere to.
The assembled wood and foam is then placed in a bag and vacuum is applied; around 6" Hg is what it takes. I place the vacuum assembly onto a husk and leave it alone overnight with vacuum on the whole time. Strength is foam tearing which as good as you can get.
Learning vacuum technique is highly recommended; I use it for everything I laminate. I may show you guys soon (especially if there is interest) how to carve wood props and finish in vacuum laminated carbon cloth. You can get pretty much any shape prop you want to experiment with by taking existing products and reshaping them, producing a thinner more efficient shape with better area and pitch distribution. You would be amazed how inefficient available wood propellers really are especially for the larger gas engines.
Another lamination type that uses vacuum is fixed landing gear struts. Carbon layup over balsa wood is what I often do when I am in a pinch and don't have a mold ready. Must be vacuum laminated for best results for strength and lightness. My landing gear for a typical 140 sized pattern model at 11 lbs, weighs in at a scant 3.5 ozs which includes pants axles and wheels. Compare that weight with anything commercially available. The gear on my primary pattern model is entering its 6th season next year which speaks volumes for the mechanical strength of the gear set-up I use.
MattK