pughman said:
yes , tell me how to make a cowl look gooood man...
well first off i dunno where u got the idea that im a "pimp". but hey, as much as i hate the concept of a "pimp" and prostitution, sure ill be a "pimp" tonight just for you.
secondly, i asked "how thick is that metal??" and your reply was "it is for me , and to make it look good" . So i have no idea how to respond because you didn't even come close to answering the question - i didn't see any numbers to indicate thickness in your reply. (thats why i asked if you were referring to me).
so anyways, lets get down to the cowl hood thing. i'd probably start off with a high density polyurethane foam just because that stuff is so much fun and easy to shape. if high density poly foam isnt available, i'd probably go with just normal insulating foam from home depot (aka "Pink" or "Blue" foam) - cowls arent usually very tall anyway so two layers of 1.5" thick home depot insulation foam should do it. if home depot foam isnt available, id probably go with sheets of plywood - tack em up, build a moderate subframe under it all to support the shape and then round off the edges. whatever you make this part out of, we'll call this product the "Positive".
if this was a "multi-run" mold, i would then coat the Positive with layers of fairly heavy fiberglass and let that cure overnight. then sand it up smooth and check for any pits. if any pits are found on the fiberglass, i would fill it up with something (maybe bondo but probably fiberglass over it). then sand it and paint it black. after the black paint dries, look for any imperfections on the surface and if any are found, then fix and resand and repaint and recheck. so anyways, after the Positive is all done, i'd apply (brush on works but spray is better) some poly-vynil alcohol (PVA) on the Positive and lay it on some "non stick" sheets of plastic (or wax paper taped together to form a larger sheet). after the PVA dries, its then time to carefully (as to not scratch the PVA film on the Positive's surface) lay a few layers of fiberglass (kevlar is prefered) over the Positive and then some epoxy. Then set up your vacuum system so that the top layer of fiberglass/kevlar is "pulled" onto the Positive as tightly as possible using another layer of plastic on top to sandwhich the Positive - let that cure overnight. the next day, pull the Positive from the top layer of the now cured fiberglass/kevlar and epoxy combo sitting on top - use water to saturate the PVA. That layer that was pulled from the top is now called the "Negative". then its time to check the Negative to see if there are any pits and other anomalies on the under side. If the Negative is good, then its time to start mass producing cowls.
if this is a "single run" mold, then i would probably just wrap the entire thing in "cling wrap" (the kitchen wrap). then lay it on some "non stick" sheets of plastic (or wax paper taped together to form a larger sheet) and then apply a few layers of fiberglass on top. then gently press the fiberglass onto the cling-wrapped Positive while applying epoxy - trying to make the top surface as smooth as possible (use of a "squigy" helps to remove excess epoxy and to smooth out the surface). then let that cure overnight and the next day, pop out the top layer from the Positive. then its time to sand/paint this top layer you removed to your liking.
of course this is more time consuming than sheet metal work but this is usually how its done. oh and of course carbon fiber can be substituted for anywhere fiberglass or kevlar is mentioned.
polyurethane foam (sometimes referred to as "yellow" foam):
insulation foam (this one is the pink version, the blue version is similar):
so now i guess its time to ask again:
how thick is that metal??
.