|Oct 25, 2006, 11:48 AM|
3 Control Surface Wing
My last Predator Bat was flying/DSing so well, still is, I was motivated to try another Bat like build with a bit more versitility. I build a Super Freak, a Bat with a wedge of foam cut off the root cords to effectively make the TE perfectly straight and adding sweep to the wing at the same time.
I had a BUNCH of reasons that really motivated me to do a straight trailing edge, VS the forward sweep of the TE on the stock Bat. I planned to build this baby with regular balsa elevons, though I did make them reach out board a few more inches than the stock ones to get MAX roll authority, it was key to make them reach way out board since they will not be reaching inboard near as far as the stock ones. I installed a 3rd servo for an independant center elevator and, I anticipated that all the extra balsa on the TE would add extra ass weight. The only way to balance easily would be to buid it Super Freak style, the extra sweep making it EASY to balance with the extra weight tail weight of all the flaps!
From there I was perplexed on how to get a verticle fin, over/under fin for DSing, attached with the new elevator in the way . My first plan was to have the Elevator pass through a slit in a single vertical fin but, after thinking it over, I realized ANY tail fin damage would be A REAL PAIN to fix with a big fancy over/under fin like that. Further, I have also been having my big tail fins flutter when doing high speed DS, at around 120+MPH airspeed. I would pound the sear leaving the dark side/hitting the huge head wind and my big coro tails would flutter, especially if it was turbulent. I needed something that was light, would not flutter, and accomidate my elevator all at the same time. The stout twin fin design with a CF rod extending almost to the TE of the fin seemed like a GREAT solution. Fixed all my problems in one swoop.
Then Ian mentioned that all the Bluto guys complained about their tail fins rotating and locking out their conrtol surfaces. I did not like the sound of that plus, I have been DSing in HUGE turbulence where my 3M 77 glued in tails rotated while slamming some really nasty crud on the dark side! I figure that the smaller tails will resist twisting better, especially since I notch them both where they meet the body of the wing so, they not only slide onto a CF boom, tightly, they also lock right onto the body of the wing around the TE. Then I gooped them into place where they lock around the TE. I think this system will be BOMBER and I can even afford an accidental combat hit since the odds of lossing both tails is rather remote, but possible !
So far, I have set up the wing with a regular elevon program and I mixed in the center elevator at 100% so with elevator action alone all control surfaces move exactly together. With pure alieron inputs only the out board alireons respond. I'd love ANY and all advice on this set up to further enhance performance.
Last, I am thinking of doing a second programable mix where the elevator angles down and the alierons angle up, Crow flaperons what ever you call it. Ian also told me the horror stories about doing this with wings and watching them literally FLIP OUT . I am hoping with the flip of a switch I can turn on this mix and SLOWLY apply the mix at altitude and see what happens. If I can simply get a slowed wing that gently pulls up I'd be stoked. Then I know I can scream up the backside and apply my mix BEFORE I SLOW DOWN MUCH!
At our local site, slowing down on the dark side can be pretty nasty with ANY turbulence back there and there often is! Landing on the front side cliffs is NOT an option! So a good landing consists of coming up the back side, manuvering back there to slow down, then getting POUNDED as you come in on final TOO SLOW to handle ANY turbulence! I'm hoping I can GREATLY reduce my exposure to that with a ship that slows down FAST!!!! Suggestions, little help, ideas. . . .
Last, seems like the DS Bees are catching on fast. Locals are building them after seeing mine consume large amounts of turbulence/super nasties and come back for MORE. It is still in GREAT condition, I'm not sure if I'm just lucky or it flies so well it is easy to survive. One thing is for sure, I push it HARD regularly! Here is one I recently completed for sale to a Bro. The build on this one is at least 3 hrs more so, the build costs will go from $70, for a Predator Bee with all the fixens (glues tapes and coverings!), to $120 for the DS Bee since it has 5 spars vs 2 in the Predator Bee and literally 4X more tape; it is COMPLETELY covered in tape 3X and has 5 LAYERS of tape at the LE! Not to mention a THICK layer of Goop over that, then covering, then 2 more thick layers of GOOP over the LE and wing tips. Oh YES, she is a monster!!!! And still flyies in moderate lift but, it is in its element when the wind is RIPPING
|Oct 25, 2006, 12:04 PM|
Joined Jul 2001
I like the new things you are trying with the Bat! I can't wait to hear how it does for you. I've got a Bat half built but with some of my own mods but I got distracted to some other planes first.
Did you think about putting a simple mix in your radio for this 3 servo wing so that the ailerons still move up and down with your center elevator so that your whole trailing edge works as elevator but only the outboard surfaces work as ailerons? You might have even explained this idea already in your post but I just skimmed it...
Anyway, keep at it!
|Oct 25, 2006, 01:23 PM|
I would think it is really not necessary to mix ailerons and elevator since planks are already pretty sensitive to the elevator input, and the middle elevator alone should have plenty of authority. Also, by using only the elevator, you should be able to increase the elevator throw for more resolution instead of using just 10-15% common to these planks.
As for the crow, it should work, but will take time to setup because the surface area of the outboard ailerons and the elevator is different so depending on the throws, the plane may suddenly pitch up or pitch down. You'll definitely need more elevator throw than ailerons for the crow to work, but it does work. I have it setup on my booby and needed some trial and error to dial it in. Just setup the crow on the throttle stick, then slowly apply it to see if the plane pitches up or down and adjust the throws accordingly.
Hope this helps.
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