Oh boy...
I don't want to come in here and be perceived as a know-it-all bashing the efforts of others, but I just can't sit around and say nothing when erroneous information gets circulated about an aspect of the hobby that I dearly love. I have absolutely no reason to believe this misinformation is intentional, merely that it's a misperception based on some *very* longstanding ideas about free flight that are really a misinterpretation by the rocketry community. I've lived my entire life watching these errors wind their way through the rocketry community and it seems like we're constantly having to address them. Then again, there is another set of errors that winds its way through the free flight community that must constantly be put to death. Please understand therefore, that I fly both and have enjoyed much success in flying all sorts of model airplanes. I've flown free flight competitions of a variety of types for quite a while. I have not ever flown rockets competitively, but if you look up the Flite Test videos on my aircraft, you'll see that they fly just as well as any.
Also, this is NOT a plug for my or anyone else's products. I welcome competition. It brings out the best.
So then...
Here is some intro data and pics:
If building kit for free flight use (no radio control), it is best to fly with B4-2, as use of C6-3 will be hard to recover, especially in ANY wind. Trim to circle.
I just don't agree with this. I've flown C swing wing gliders (no, not the heavy draggy ones from the plans on the NAR website), off a piston, on a windy day, to altitudes that strain the eyes. It's all in how big of a field you have. A serious rocket/boost glider enthusiast would do well to look into how the free flight guys recover their airplanes. 10 minute flights off a 5 second engine run, or even a mere rubber band, are commonplace. We do our best to fly on big fields, sometimes tens of thousands of acres. Trimming to circle isn't nearly so much about recovery as it is staying in the thermal. Many of the FAI guys trim their models to take a full 5 minutes to completely a single circle in calm conditions. I've seen others that were trimmed to fly in a perfectly straight line until they encountered a thermal, at which point the increased airspeed would cause the circle to drastically tighten. Up, up and away! Until the fuse burns through. Then it comes back down, you go get it, and the process starts again. What, no fuse? Oopsies!
RC boost gliders have a reputation of being hard to fly. FAI S8 RGs can be, due to marginal boost stability. The only CG shift comes from propellant burn-off, with some up elevator at apogee providing the trim adjustment for glide. Boost can be a terror, because the elevator must be constantly jinked to provide vertical flight. Beginners often just loop them into the ground.
Yes, they can be difficult to fly, but only if either the design is deficient or the trim settings are incorrect. If your radio can't support multiple flight modes, you should buy a new radio. They just aren't that expensive anymore. You should have a launch mode that gives you neutral trim and a glide mode that gives you a stable, hands-off glide.
The RumbleBee will boost straight on its own. Having zero incidence (no up elevator), it will still transition and glide well (CG must be correct). Some say auto-elevators or slight incidence is required on BGs, but as long as the stabilizer is LOWER than the wing, turbulence off the wing will provide some push down on the stabilizer (ref. G. Harry Stine). I have never seen a death dive with this glider. Using rudder only control makes this bird easy to fly. Elevator control is not really necessary.
I have serious concerns about this trim strategy. No offense to Stine, he was a great flier, but that simply is not a correct or safe way to fly a glider and ignores a century of efforts in designing good gliders. I assume Stine got this information off someone back in the day who was either poor at explaining how things should be done or who wasn't a particularly good glider flier. Unfortunately entirely too many articles in free flight are written by the latter because the experts are busy flying and/or aren't the ones who know how to write a persuasive article. I digress... Bottom line, we just don't fly them that way in the free flight world, even with locked down models, and if it's not safe there, it sure as heck isn't safe on a rocket. I've been flying free flight catapult and hand launch gliders since I was a kid, and I very quickly learned through bitter experience that the people suggesting 0-0 launch incidence were not being honest about aerodynamics. The idea that a model can remain stable in glide using only the downwash of the wing hinges on the model never being perturbed out of the high angle of attack flight regimes. In the real world, this only happens indoors, and only under perfect conditions then.
You've got two options to get an actual safe flight profile that other people can repeat. Emphasis: yes, you might be able to tweak yours to do it, but you have to keep tweaking, and you can't ever get the model damp, and are you really sure your customer is going to be able to repeat it? Remember, wood expands and contracts in less than perfect storage, has internal stresses, etc. What goes into the kit package is not representative of what comes out of it 5 years later when someone finally gets around to building the model.
So what's the first option? Well, you've got a really cool kit there, and if you'd add an elevator, it would add, what, another 1.5g? On a C boost glider, that's nothing. I fly 18" locked down C rocket gliders with 3.5g servos and they get WAY up there even if you use really heavy wood for the fuselage. My Carbonette 19 goes to the edge of visibility on C's, and that's without even using a piston launcher. Yours probably lies somewhere in between. You've got nice cantilevered pushrods that make assembly much simpler than my airplanes, so why not go that little extra step and make it a super product? Yes, I know, it's more complex. I think customers can be understanding of that.
Something else that helps, and I noticed you're starting to do this, is to extend the nose so that you get a longer moment about the rocket motor. This is key to getting really straight launches on these aircraft.
The second option is to do what I did with the Carbonette series--pop pod on a long moment arm (and trust me, this is by far the lightest method--I have trouble with Carbonettes coming out too light and then I have to ballast them to get the best sink rate in less than dead calm conditions). With this long pod, you can load in your 3 degrees of stab incidence and the thing will still launch straight as an arrow. No elevator needed.
There is a major cost to single channel R/C. You're limited in wind conditions to whatever the glide speed of the glider is. Any more, and the plane gets blown backwards. Also, you can't deal with turbulence or make efficient turns. When you step up to elevator and rudder, the aircraft becomes capable of basic aerobatics, but more importantly, you can nose over and run upwind after you've chased that thermal way downwind. Or you can run upwind after a thermal that might be up there. Again, watch some of my videos and you'll see a few hints of what's going on there. It really opens up a whole new world in rocket powered gliding when you can make full use of the airplane once it's up there.
Again, I'm trying to help here. This is not in any way trying to take away from your product as there's room enough in this hobby for all of us. If your product is the best it can be, that actually helps me because people will buy it, fly it, enjoy it, and want to try other similar aircraft. On the other hand, once people have had as much fun as they can with my airplane, I'd like to be able to point them to yours as something else they can try. Keeps the excitement up and we all win.
It is a rudder only RC BG for B4-2 or C6-3 motors. There is an article on it in the May/June Sport Rocketry for 2017.
rum "brick" radio, but the Turnigy 5X, with the rcvr board out of the case, and put on a plate with an indoor flier tiny servo. Radio system is $25, servo $4.50, battery $2, charger $10. Kit price is $25, without radio eqpt. Contact
