Originally Posted by
serious power
Hi Matt,
Perhaps a preformed sandwich is worth considering.
Could be done flat or onto a form with mylar.
When I was molding fuz's in the late 80's I ended up using Rohacell 51 - was the lightest and hardest (good compressive resistance) that we could find at the time.
Anyway I decided to look it up again as I was looking at Herex the other day.
I found this;
http://www.rohacell.com/product/roha...les-range.aspx
Of particular interest is the IG-F.
At 31Kg/m\3 (that's 2lb/ft\3) it's 1/2 the weight of super light contest grade balsa.
I'm sure it's not cheap but it must be worth investigating.
A skin with 0.75oz to 1.5oz glass on the outside and 0.5/6oz on the inside (or maybe 0.3oz carbon veil) c/w 1mm 31IG-F would be good for a 2m pattern wing.
Just a thought !
Brian
Brian,
One company that has responded with small 10cm square samples was Clarasonic. Distribution from Thailand and California. Thailand,...99/1 Houyai, Ampher Muang, Phetchabun, Thailand-67000; Tel:668 1753-0298.................US: 28 Washburn St, Simi Valley, CA 93065, Tel: 805 526-7568
IGF is one sample they included. They also included several others, as well as cross grained balsa in 1mm thicknesses. I don't know if it would be strong enough as a wing skin or if it would shave any weight. Worth building a panel and testing it. For a bipe wing, the panel should be able to hold about 40 to 50 pounds at about the MAC. The panels may need a spar....I think a simple 1/8" x 3/8-1/4" balsa spar that covered about third to half the span would be plenty if needed. Or 010" carbon strips top and bottom instead of balsa
On preforming, I've been thinking about using the actual foam core, lined with mylar sandwiches top and bottom (mylar, glass, rohacell (or balsa), glass, mylar), and vacuum forming the skins directly on the foam first. Then skinning the foam cores in the usual way. I haven't actually done it but have wanted to for some time. Actually haven't done much lately due to health issues. I think the 1 ounce cloth (out) and 0.3oz carbon (in) combo should be enough, but I think it might be heavier than standard balsa and doped paper.
Rohacell cost (last I saw) was around 70$ (??) (I forget the area but it was large enough for the typical wing panel). That's about 4X the price of 4-6 pound balsa, but if it's strong/light enough, should be worth it.