Author Topic: Foil layups?  (Read 2446 times)

surfcowboy

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Foil layups?
« on: October 20, 2017, 08:50:07 PM »
Ok so I'm assembling a hot wire cutter and starting to ruin foam learning to cut wings. Who's got any idea about what carbon I should be using.

Fiberglass Supply always has various deals but they all seem heavy. They've got 9 oz and 11 oz on special but am I right that I should be somewhere more like 6oz with a few layers of carbon and glass laid up together?

I'm looking at a plywood mast and fuselage (ala sea breeze) and then likely a foam core wing. What's the jam here?

PonoBill

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Re: Foil layups?
« Reply #1 on: October 20, 2017, 09:41:23 PM »
Yes, six ounce is probably all you need. Multiple layers of carbon don't increase rigidity much over a single layer, and there's not much reason to use the heavier weights. At least one, maybe two layers of glass on top to sand. If you sand the carbon you cut fibers and kill the strength. If you think you need more rigidity it's a good idea to sandwich, meaning a layer of carbon, a layer of glass, then a layer of carbon, or better yet, a layer of carbon, a layer of PVC foam, and a layer of carbon. But practically speaking, one layer of carbon and two or three of glass is probably all you need.

I'm currently screwing around with forming Sintra foam into molds. Dirt cheap, and it gets very soft to the point that you can stuff it into compund shapes at about 200--250F. Cheap like ten sheets of 16" X 20" X 1mm is twenty bucks. I heat form the Sintra into the mold with a heat gun, then pull it out and do gelcoat, then carbon from a table wetup, then stuff the Sintra piece back in, then carbon (table), then bag it all together. Totally bomber and featherweight. Car parts only so far (an air box for my GMC RV), but obvious opportunities for featherweight hollow masts and wings. I think I could do male molds and drape Sintra over them. Trim them up, carbon on the inside, then carbon on the outside and lap it.

I also have about 50 pieces of 16" X 16" X 3/4" black PVC high-density foam (but still light!) that's used for signs and POP displays. This stuff could be CNC'd into wings and be super strong with one layer of carbon. Every time I look at the stack I see wings.
« Last Edit: October 20, 2017, 09:50:37 PM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

supuk

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Re: Foil layups?
« Reply #2 on: October 21, 2017, 03:43:12 AM »
on the foam core wing I did I used 5 layers of 6oz glass top and bottom and I think I may have had one layer of carbon in there as I had some scraps I lying about but I wouldn't hesitate just to use glass. The main thing is to have a nice solid mount point that ties both skins together

surfcowboy

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Re: Foil layups?
« Reply #3 on: October 21, 2017, 10:17:53 AM »
Ok, so 5 X 6oz will work.

If we add a layer of carbon, maybe that replaces 2 or 3 of glass?

1 X 6oz carbon and 3 of 6 oz glass? I might do a test panel with 2 glass and see where that gets me while I'm doing small scale tests.

supuk

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Re: Foil layups?
« Reply #4 on: October 21, 2017, 11:01:33 AM »
I would keep the 5 layer of glass minimum  I really don't think there is any need for carbon with such thick airfoils. the wing I did in glass came out way lighter than the original.

surfcowboy

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Re: Foil layups?
« Reply #5 on: October 21, 2017, 08:09:19 PM »
Cool, that's great, I'll save the carbon for the mast layup then.

peterwSUPr

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Re: Foil layups?
« Reply #6 on: November 07, 2017, 06:40:13 PM »
Two things that come to mind about the layup is it depends on the thickness of your foil, and also don't forget about the risk of an impact on something.  I don't remember off the top of my head, but i think I probably had about 30oz worth of carbon on each side.  I'm sure a bunch of that could be glass instead of carbon.  Also how strong is your foam core?  If you are using a hot wire I assume you have EPS?  Mine was a corecell core.  The weight you add with an extra layer or two of glass or carbon is not that much, don't try to make it too light.

Peter

surfcowboy

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Re: Foil layups?
« Reply #7 on: November 07, 2017, 08:15:36 PM »
Thanks man. I'm using EPS now, but the prototype was a urethane sculpt foam.

I think I'm going mostly glass on the wing, maybe a layer of carbon if I have some left from the mast. Impact is for sure a concern.

And yes, from what I gather, there's no need to even worry about weight really. No way I'm going to get to a weight that will matter.

I've never built anything this substantial out of glass before. Can't wait to see how it turns out. Really working on the mount idea now too.

 


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