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Design => Stunt design => Topic started by: Bill Little on December 15, 2011, 03:13:06 PM
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OK, Guys, lay it on me.................
A Bronco for stunt using (2) OS .20FP or .25LA. Constant chord wing, twin boom (been plenty of those), could it be a plausible stunt design? Would want to keep close to scale as much as it can be done.
Thanks!
Big Bear
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The way the cowls are layed out it lends itself to upright engines too. The only thing that's scarry is the high tail - a pain for linkages, structural vulnerability and being out of line with thrustline. I would lessen effects by keeping near scale fuselage length. and makking the fins as low as Ci could while maintaining a reasonably accurate appearance
Of course that center pod could carry a LOT of lipos!
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Thought it might help to post a 3-view. There would be some serious problems with getting the leadouts through the inboard engine compartment, so I am thinkin' that electron power would make that much easier.
Tho the OV-10 was an effective airplane, I can't see that it would make a good stunter, or look right doing the pattern, for that matter. Would you consider the Aero Commander that Bob Hoover flew shows with? H^^ Steve
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Bill-
That's a very interesting thought. I can see a linkage that could circumvent the inboard engine, with the bellcrank inside it on the wing or in the nacel, with the leadout guides low below the wing for leadout exit to be even vertically with the c.g. location. The tail is reasonable at about 23%+ of the wing area. The tail arm is very long; 'looks like a TVC of about .61!, which is huge. You could cheat some and up the wing chord and maybe the tail's. Heck, it might even work at true scale. So that looks like a viable semi-scale stunter, with a chance at true scale appearance. Naturally, that's for you rather than me! Go for it!
SK
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- For IC power you might want to stretch the nacelles a bit -- and Serge's observation about linkage has merit.
- I thought constant-chord wings was a Bad Thing??
- LiPo in the fuse and 'lectric motors in the nacelles make the balancing task look easier
- There's a plane that would look clean and mean with anhedral -- and that would take care of your vertical CG problem.
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Bill,
I have a profile scale 1/2A Bronco I designed for the Tucson multi engine 1/2A event. The existing design has a 40" span and 300 square inches of wing area. y1
Pat
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Maybe a minature servo motor driven fly by wire (get it?) unit will solve the control system problems. Then we can have counter insurgency stunt. I will stay away from the political comment on that one. Lets see........hourglass, leaflet drop, loudspeaker broadcast to the judges.........big points!
The Embraer EMB Super Tucano is a bit more sexy or even an A-10 warthog. I think these all have sharks teeth for psychological reasons.
If you can make it work it will be quite an achievement!
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Heh-heh, I've actually got some full size drawings that I did about 7-8 years ago for a 48" span stunt Bronco. Another one on the "To Do" list. ;D
For all out stunting though I have to wonder about the horizontal stab and wing height relationship. It would probably do insides on a dime, but the outsides might be a different story. Would be a really cool sport/stunt model though. y1
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I dont know how much of a real concern the high stab would be,, actually if you look at the relationship to the wing its not a LOT different than a standard model, unless you were going to make it pure stock in layout. I think you could cheat the tail a bit lower and still obtain the look. My two cents worth,, Its kind of like the Avenger, it really looks like the tail is high on the fuse but its not much different than a normal stunt model..
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Thanks, guys!
It would have to be cheated a tiny bit, but it would still be recognizable as the Bronco. Stunt airfoil, slightly larger wing, moving things around just a tad, and it should be in the line of the average stunter. vertical C/G would be "my" problem in calculating. Would probably want it to be sized for (2) OS .20FPs.
Thanks, again!
BIG Bear
RNMM/AMM
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Thanks, guys!
It would have to be cheated a tiny bit, but it would still be recognizable as the Bronco. Stunt airfoil, slightly larger wing, moving things around just a tad, and it should be in the line of the average stunter. vertical C/G would be "my" problem in calculating. Would probably want it to be sized for (2) OS .20FPs.
Thanks, again!
BIG Bear
RNMM/AMM
Hey Big Guy - feeling better, I trust?
This is an interesting idea. If I was going to do it, I would look at around 650-700 squares for 2 20FPs. I would put the bellcrank in the inboard nacelle and then have the leadout guide hang below the wingtip. I would run pushrods using aileron cranks to get them to the outboard boom, and then drive the flap and elevator from both ends. With ball links it's not unreasonable.
Weight would be an issue. I would think that up to 70 oz might work.
Brett
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I think Brett's on the right track but I'd say 650-700 squares and (up to) 70 ounces would be a lot to ask of two FP .20's, just my opinion. I'd either shrink it slightly from those specs or use more power. And yes, scale proportions can always be cheated to our desired stunt advantages. The Bronco is totally do-able though, and you sure won't see a line of them at the field. Lot's of cool paint schemes to pick from too. y1
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and some white phosphorous rockets for when the judges dont see your pattern the same as you right wayne?
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You'd get some dihedral effect from the fuselage. Negative dihedral would cancel it, but would look wrong if the full scale airplane didn't have it.
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You'd get some dihedral effect from the fuselage. Negative dihedral would cancel it, but would look wrong if the full scale airplane didn't have it.
The game is on! Find more "don'ts" for Howard's signature' No U-turn
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Hey Big Guy - feeling better, I trust?
This is an interesting idea. If I was going to do it, I would look at around 650-700 squares for 2 20FPs. I would put the bellcrank in the inboard nacelle and then have the leadout guide hang below the wingtip. I would run pushrods using aileron cranks to get them to the outboard boom, and then drive the flap and elevator from both ends. With ball links it's not unreasonable.
Weight would be an issue. I would think that up to 70 oz might work.
Brett
Thanks, Brett! Those are all ideas I had for the controls. One of the old Classic planes I was looking at had that set up and works well.
Size are 650 would be to my liking, and I still have a vertical CG problem, ??? Like what Howard said! Drawing it up will not be a great problem, I will "borrow" an existing modern airfoil for sure, maybe just a tad on the thin side, but still modern. Thinking Juno or Saturn airfoil.
As to the health, I am 1/2 way through the treatments, and hanging in. Some parts of the day are better than others. ;D
Thanks!
Bill
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Size are 650 would be to my liking, and I still have a vertical CG problem, ??? Like what Howard said!
Putting the controls below the wing, in the nacelle, with a hanging leadout guide, is a solution to that.
Drawing it up will not be a great problem, I will "borrow" an existing modern airfoil for sure, maybe just a tad on the thin side, but still modern. Thinking Juno or Saturn airfoil.
I would not use a thin airfoil - weight will be a killer on this one.
Brett
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Putting the controls below the wing, in the nacelle, with a hanging leadout guide, is a solution to that.
It would solve the vertical CG problem, but not the Clbeta problem from the fuselage.
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It would solve the vertical CG problem, but not the Clbeta problem from the fuselage.
1: Picky, picky.
2: I think Al Rabe had some thoughts on planes with dihedral (or the affect thereof)
3: I think that a Bronco with a tad bit of anhedral would look kewl.
4: Build it, lend it to me -- I'll fly it just as badly as a perfect airplane.
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It would solve the vertical CG problem, but not the Clbeta problem from the fuselage.
It's not the greatest candidate for a stunt plane. Besides, think of the great fun we could have discussing the effects of putting the bellcrank pivot a foot inboard. That sounds like a great way to start the new year.
Brett
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Besides, think of the great fun we could have discussing the effects of putting the bellcrank pivot a foot inboard. That sounds like a great way to start the new year.
Wouldn't it hinge terribly, because there's so much extra mass on the outboard of the bellcrank?
(keeping my face straight, and ducking, and covering)
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Yes, but you can counterbalance that by putting the tip weight into the exactly same spot in the outboard nacelle. L
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Vertical CG is not a problem at all, simply mount the bellcrank and especially the leadout exit at an appropriate height in the model. If desired you can also make a leadout guide that is adjustable vertically as well as horizontally. As far as the airfoil, don't go too thin, you will regret it. On the other hand, you don't want to go too thick and make it "draggy" either. As a nice "in between" compromise I used the Nobler airfoil on the PBY and it worked out very well.
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Wayne, really,
you think you know something about this high wing twin warbird building of planes no one else would think about building,, pffttt,,
LL~ LL~
Now a real challange would be to build something like oh, a 109 stunter,, THAT would be hard,,,, * to finish anyway* HB~>
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To replies from Brett's #20 onward....
Location of the bellcrank is not very important, so we've been told for quite a while, eh?
Except for two things:
... the weight of the bellcrank spanwise may require counterbalancing.
... internal "misalignments" can (do!) increase wear on leadut guides.
The line trail angle at the leadouts is the angle pull force follows from the leadouts toward the CG, right? We can estimate that angle. It becomes pull's line of force aimed through the leadout guides. That line of force can be extended.
If the bellcrank pivot is on, or close to, that line of force spanwise, we don't have friction and wear from bending the leadout wires. As the line of force can be extended, we could pivot the bellcrank ON that line at the inboard wingtip, or the outboard tip or anywhere in between.
As to the OV 10, I saw a (probably Profile) Scale model of it - close to original shapes and proportions. It looked very weird ! Early prototype OV-10s had even shorter wingspans, changed quickly afterward to as in the 3-view. Fuselage, booms and particularly the fins, looked way out of proportion for a CL model. IMHO.
Nothing like a challenge, right?
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Wayne, really,
you think you know something about this high wing twin warbird building of planes no one else would think about building,, pffttt,,
LL~ LL~
Now a real challange would be to build something like oh, a 109 stunter,, THAT would be hard,,,, * to finish anyway* HB~>
Man Mark. you've gotten so gun shy on this subject, that you're making excuses before we say anything LL~ LL~ HB~> S?P H^^
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John, it hurts less when I say it first
sigh,,
worst part is I really want to finish the dagnabed thing,,
plus Wayne and I have uh,, well history on the subject LOL,, I keep hoping he will forget it,, but I guess not everyone has the same memory as I do
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Wayne, really,
you think you know something about this high wing twin warbird building of planes no one else would think about building,, pffttt,,
LL~ LL~
Now a real challange would be to build something like oh, a 109 stunter,, THAT would be hard,,,, * to finish anyway* HB~>
Thanks Mark. ;D
I'm just pointing out that for the most part this stuff isn't nearly as difficult as many always seem to want to think. The biggest problem I that always notice is people "overthinking" a lot of what the basics are in C/L, and then overcomplicating things as a result. When in doubt, always remember the K.I.S.S. rule. Heck, all I did with the front/rear leadout position on the PBY when I did the initial pre-flight bench trimming is hang the completed RTF model from the leadouts and then adjusted the model for a very slight nose out position. Other than for height (explained later here) I haven't ever moved them since.
The Bronco could easily be designed and built as a very capable Stunter. Sit and look at a side view of the plane and then imagine the airfoil centerline in relation to the center of mass of where everything like the engines, tank, control system etc. would be mounted in the completed model. While designing the model on paper, mounting points for all of those things can be adjusted slightly toward or away from the airfoil centerline as desired. But, even in true scale, on the Bronco the bulk of those items aren't that far off of what that desired (airfoil) centerline would be anyway. The Bronco just fakes you out into thinking all of these things are way off just because of it's overall appearance. Weightwise, things are hardly any different on the Bronco than on a "normal" airplane. The only thing that is really that much different on the Bronco is the stab/elevator height in relation to the wing. That, as some have pointed out, could easily be "cheated" while still maintaining a very good scale outline.
For thought and comparison, in the case of the PBY the engines, wing and stab/elevator are all on the same line. The only thing of significant weight away from the airfoil centerline is the heavy trike landing gear. All I really had to do then was end up with the leadout exit lined up happily with the vertical CG. I literally "eyeballed" and estimated this position when I did the original design and planning of the model. Knowing that I would never nail it exactly is why I made the vertically adjustable leadout guide. When all was said and done, I missed the ideal height position by about 3/8" of an inch and my original guide didn't have quite enough vertical adjustment in it. When this was discovered I made a new slider for the guide, finalized the adjustment, and haven't touched it since.
While designing, just focus on alignments of flying surfaces and CG points and draw them in where they need to be. Then final key is really just down to getting the leadout position right. The model doesn't have eyes, it doesn't know what shape it is. ;D
Now Mark, what about this 109?! Better just get it finished and flying, it is gaining weight as we speak through wood petrification!!!
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Thanks Mark. ;D
Now Mark, what about this 109?! Better just get it finished and flying, it is gaining weight as we speak through wood petrification!!!
It is NOT getting heavier, its actually an ounce lighter this year than it was last year,, so,, I figure if I let it hang another couple years it will just wow the crap out of everyone,,
LL~ LL~ LL~
Wayne, YOu know how much I love the PBY,, even if you did build it too fast,,
I agree on the OV-10, while I don't think it will replace an Impact, Legacy or Thundergazer, it could be a very entertaining and reasonable stunt machine.
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I agree on the OV-10, while I don't think it will replace an Impact, Legacy or Thundergazer, it could be a very entertaining and reasonable stunt machine.
That's exactly it Mark, and designed properly I'm confident many would be suprised.
So Bill, ready to get going on this one?
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That's exactly it Mark, and designed properly I'm confident many would be suprised.
for
So Bill, ready to get going on this one?
Hi Wayne,
This something I have thought about for a while now. I have three stunters to finish first, but they are all over 75% done. Side effects are really busting my butt and slowing me down. But only 5 more treatments and things are supposed to improve (so they say! LOL!! ) My outlook has definitely changed since all this started so I will not be dragging near as much when it's all over.
Bill
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Bill, just start it, Wayne will help remind you to finish it, muah ha ha,,
seriously, glad to see you with a positive outlook my friend,, keep the chin up,,
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Good to hear Bill, let me know when you're ready and I'd be glad to help "pencil it out". y1
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Bill,
Bob Hunt and I have talked about a similar project. The stab height can be fudged. Looking at Mackey's Carousel, and the Sheeks Sea Vixen, both have the Stab 3 inches above the wing centerline. I expected a big difference with insides and outsides but the Carousel did not show this.
Due only to having too many projects for customers, the Sea Vixen still needs final plumbing before flight, so I can't say anything its flight characteristics. But being heavy, I am not expecting the Vixen to be the best. Funny, but I usually build lite, but the Vixen went through too many problems during the build.
Brett's suggestion on the bellcrank in the nacelle might be an answer.
Charles Mackey had twin boomers with the bellcrank in the inboard and outboard wings. He felt that the outboard bellcrank behaved better. this is a surprise since we all know that the leadout location should be the driving factor...??
Jack Sheeks used the slave pushrods to actuate the elevator from both booms. This is easier to do with today's ball ends, but also adds weight. I still think that the Bronco project is worth it. Size it at 620 to 650 sq it will work.
Much to consider. Wayne is still the best bet for help with this configuration.
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Bill, just start it, Wayne will help remind you to finish it, muah ha ha,,
seriously, glad to see you with a positive outlook my friend,, keep the chin up,,
HI Brother Mark,
Thanks for the kind words! As to Wayne reminding me, I don't want it to become another ME 109 like someone I know.........
LOL!!
BIG Bear
RNMM/AMM
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Bill,,
really?
you too,,
sigh,,
I guess you cant pick your friends can you,, dang it
LOL
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Charles Mackey had twin boomers with the bellcrank in the inboard and outboard wings. He felt that the outboard bellcrank behaved better. this is a surprise since we all know that the leadout location should be the driving factor...??
It probably doesn't make sense on a chalkboard to a physicist, but I can totally believe that idea. I will never claim to be an engineer, but it makes sense to me that in a twin-boom type of C/L model putting the bellcrank further toward the outside boom would be better for overall stability. That is what I would do if I were to build one. With that setup I would imagine there being less potential of a pendulum effect between the bellcrank and the leadout exit point. Can I prove that this is even an issue? No.
I also feel if the pushrod itself and the elevator/stab assembly were built stiff enough, that a guy could possibly get away with just one elevator pushrod along that outside boom. I would still probably do some head-scratching on a dual pushrod system before I would commit either way. Always remember though, less complexity usually equals less weight.