Kenh,

you want use the .2 ounce carbon tissue. You can purchase at ACP or BrodK. A foam wing doesn't need the carbon. Silkspan alone has plenty of strength as does Esaki tissue. Buy them at Brodak too.....

A built up wing will have some distance between the ribs and the only reason I did mine with carbon and jap tissue was for the poke through strength. It just aggravating to grab a panel awkwardly and crack the balsa skin. If the spars are designed right, carbon is not needed for anything else. Still, as light as it is it's added insurance, enabling using ultra light wood on built up wings.

It's best to use the carbon inside the skin, as I described above. Problem I had was I thought I had the material and didn't. I waited almost 3weeks before it arrived and by then the first panel was done and I had the second started. So I compromised. The skins are tough just the same. I can lift the whole panel by the tip so this approach is fine for our purposes.

Your Choice.

Edit..... You don't want the heavier carbon. It's the same price and it's tempting but the heavier grade is much thicker. Thickness means weight and just because it sez 0.5 ounce doesn't mean that it's applied at that weight, it's not glass.