I finished scratch building an Estes Falcon boost glider, and after several test tosses, tried the first flight on an Estes 1/2A6-2. Nice, straight boost, motor out at apogee, and it came down almost as straight as it went up. The dis-assembly was complete.
Why would the glider fly well when hand tossed and come in ballistic after a straight boost? Anyone have a similar experience with the Falcon?
You need some difference between the angles of attack between the stab and the wing to get this bird to glide.
I originally took to putting a small wedge under the trailing edge of the stab to force this angle into place. If this wasn't done JUST precisely right, the bird would glide great, but loop into the ground under power.
The secret to getting good Estes Falcon performance is to put the incidence in the WING. (I stole this idea shamelessly from Kevin Stumpe, husband of NAR HQ manager Marie Stumpe.) He suggested 2-3 degrees of incidence in the wing to me during one of my NAR HQ visits. Putting the incidence there means it's close to the boost CG, and will thus have less of a moment arm to work through during boost.
As soon as the engine spits, then the CG shifts, and the moment arm gets a lot longer, and more effective. Instant pull-out from a dive.
How to get that angle in there, you ask?
You could try eyeballing it, but I prefer to cut a couple of small balsa triangles to the 2 degree angle, glue them first to the fuselage, then glue the wings in place using the triangles as a guide.
When I used this trick on my Canon City NARAM Falcon, it worked perfectly for 6th place in teams. Not bad for a 30+ year old design whacked together in less than 2 days. . .
Of course, the Falcon is really poor structurally in this area. Gluing the wigns to opposite sides of the keel makes it both weak, and difficult to align!
I never had the guts to try 3 degrees, but a little bit sure helps. It will work at 0-0 just because of vertical CP-CG misalignment, but it takes a while if it get's nose-down. The neat thing about a 1/2A6-2 is that the ejection charge has more impulse than the propellant. That's where I got the idea for the "cannon dart" B Altitude model.
At my first organized launch in 20 years (~98 or so), I took to Falcons to the LUNAR launch. Worked like a charm, of course, but I was truly a celebrity for a while, because very few of the people there had ever seen any BG work correctly. I was truly hurt when the LSO called my first launch a "heads up"!
I was concerned about the wing butt-glued to the keel, but the joint did not break, the wings are in pieces. All that nice airfoiling, gone. I have started cutting new pieces for the second one. Thanks Mark and Brett. I give it some wing incidence and see what happens.
With some of the unconventional looking stuff I fly (scratch scale air-to-air, & air-to-ground misslies with varying amounts of forward fin area, odd-roc, & unseen Shrox prototype stuff), I often get a heads-up call, or "everyone on their feet" from the man on the mic. I used to be hurt when they'd do that, but I realized they're just playing it safe...alerting the crowd to something with the potential for an unpredictable flight path. Afterwards, it's fun to watch 'em scratch their heads & comment on their surprise about what a stable flight it was......usually. -- Richard "they put me on the B-rack for my scratch Bell X-1 on an E15 & it flew very well.....I don't what went wrong 2 months later...bad motor, too windy..?" Hickok
Of course, the Falcon was a ripoff of/inspired by/heavily influenced by the Sky Slash II. Pretty much the same thing, with the tip plates left off the wing, and a T-beam fuse. Even had the same structural oddity of gluing the wings directly to the fuse sides (and was even harder to align). But I wondered why it was the "Sky Slash II" vice "Sky Slash" or "Sky Slash I". I asked Larry Renger about it at a model airplane contest a few years back, and it turns out that Sky Slash I was pretty much the same design, but with a trigger to pop up an elevator, neatly solving the death dive problem. Problem was that on the very first flight it thermalled away! So he flew the other, non-pop-elevator model, the Sky Slash II - it didn't transition as well, but it also didn't thermal out on the first flight, so that's the one that got published.
Even with the less-than-ideal transition charactersitics, it was still on a different planet, performance-wise, from rear-engined models like the Space Plane and the like, so the rest, as they say, is history.
I remember talking with Larry about the same thing. The SSII was heavily edited by Estes from his original submission, because it didn't look enough like a rocket or even jet fighter. What he submitted looked much more like a conventional HLG of the 60s than the SSII. Don't remember getting into pop up elevators.
It took BG evolution several years to get back to where Larry started :-(
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
To get the alignment right, I center a 1/8" dowel in an expended engine casing, insert that into the body tube, and then align the tube on the pylon such that the thrust line is about 1" to the right of center at the trailing edge of the stab. If you more than 1", the model expends too much energy spinning and won't get any altitude.
Too touchy for my taste, Kooch. I tried that on some of the models, and couldn't get consistent results. Some worked great, while others did the loopy thing into the turf. And it's honestly not that hard to get nearly perfect alignment of the wings.
You just need a rectangle of 1/16" balsa as long as the root edge of the wing.
Now split the rectangle into two triangles, by measuring a 2-3 degree angle and cutting it on that diagonal.
Build the Falcon fuselague stock.
Now take the triangle, and glue the straight edge of one of your triangles such that the 2-3 deg. angle is located at the wing glue location.