I had a bunch of progress to report on the Nymph — I thought. The other day I got two packages in the mail: a nose cone (and some other stuff) from eRockets and some ⅛” by ⅛” spruce and 1/32″ balsa from Balsa Wood Shop. So I got to work, cutting and shaping and gluing the dihedrals on the wings, and cutting and shaping the stab and rudder, but something was looking wrong. The wing dihedral angles were too large. The plan I was working from — the one that used to be on the NAR site and is now archived — said the tips should be 2″ high, but when I built the wing that way, that put the tips at a much different angle than was shown in the 3/4 scale front view. And the wings looked way too small.
It was only then I finally noticed that in the “3/4 scale front view” (as I’d printed it) the 2″ height was slightly under 1″. Not 1½”.
Going to the plans in the MIT Competition Handbook (the original version, apparently) there’s a “1/2 scale front view” where the 2″ dimension is slightly under 1″ in my printed copy. A shade over ⅞” in fact. And the “full scale” wing, stab, and rudder are considerably larger than those on the NAR plan.
Which means I printed the NAR plans at entirely the wrong scale. In fact it looks like they’re supposed to be 11″ by 17″, not 8½” by 11″. Anyway the “Full Size” wing and stab and rudder obviously aren’t.
Great.
There are a few other interesting differences too. For instance on the NAR plan it says the fuselage is ⅛” by ⅛” spruce. The MIT plan just says ⅛” spruce, but in the accompanying article it says it’s ¼” by ⅛”, and in the plan it’s clearly rectangular in cross section. Same for the pylon, apparently. Also, in the NAR plan the stab and rudder both are glued under the fuselage; in the MIT plan the stab is on top of the fuselage, the rudder’s underneath.
Well, my pod is OK, and I can salvage my fuselage and pylon by doubling up the ⅛” by ⅛” spruce (I have no ¼” by ⅛”), but the balsa parts I get to do all over. My fault really; I should know better than to just assume a plan printed from a computer file really is full scale even if it says it is.
Besides, I can probably do a better job on the wing the second time. First was sloppy.
Rich's Rockets 