I highly recommend this:
Estes Boost Glider Technical Report, written by Tom Beach (PDF file from Estes Educator website). An excellent article with many illustrations, that cover a wide range of areas involving Boost Gliders and Rocket Gliders, including trimming.
Link to PDF file:
http://www.esteseducator.com/Pdf_files/2266.pdf
G. Harry Stine knew a LOT of great stuff about rockets. Gliders, well, there some good stuff there, but not all 100% accurate.
A zero-zero incidence is something only the best Free-Flight glider fliers are able to pull off. It is way to finicky for the average rocketeer to try to perfect. Heck, I never do zero-zero, I always use a degree or so of incidence. See “Pitch Trim and Stability” on pages 6 thru 8 of the Technical Report by Tom Beach.
And for no airfoil, it can make someone feel good about not going to the trouble, but a glider really needs to at the least have the leading and trailing edges rounded and not left square. If a person wants the glider to perform better, and even have some better pitch stability, then give it something of an airfoil, flat on bottom, rounded near the leading edge, tapered in the back. I do not mean one has to try to achieve a fully curved half-teardrop type of airfoil shape, anything that goes beyond just rounding is better, and rounding is always better than nothing.
Now a few gliders can be left square and at least fly stably anyway (just not as well as they otherwise could fly). Like some of the Edmonds gliders, and the old Centuri Mini-Dactyls and Stine’s Delta-Katt. Note that they all pretty much use some significant incidence, and usually incidence with canards.
Take note that what Zaic was writing about was Free Flight Gliders WITH AIRFOILS, mostly flat bottom Airfoils, which was partly or perhaps totally invalidated by using wings that were symmetrical, and even worse squared. But even with an ideal flat bottom airfoil, zero-zero is too finicky for less -than-experts to mess around with.
Stine’s Flat Cat, and Renger’s “Falcon” for Estes, both had zero incidence and both were a PITA to trim. My Falcon never did glide down, it glided FINE in hand throws but always death-dived after boost (on the second flight, the death dive was into hard ground and it shattered, game over). The Falcon my first B/G kit, IIRC, and I did not know enough about gliders then to realize what the problem was. It was because it was zero-zero. And I ran into the same thing with the Flat Cat, but I had learned enough by then to warp the back of the stab up to get some incidence. And the first B/G I designed that flew successfully, it had incidence in the stab too. Maybe one of these days I will get around to cloning a Falcon and THIS time give it the positive incidence it needs (though just a bit so as not to make it loop on boost).
- George Gassaway