wind junkie

My Feedback: (1)

Hi,

I'm starting a new build on a Banshee vintage pattern plane that has strip ailerons which are pretty long (see pic). I plan to install a Jett 60 LX which will turn a 10x6 at 18K RPM. The plans show driving the ailerons from the center with a single servo.

Is there any hope of NOT getting flutter if I don't go to dual aileron servos? What's the longest torque rod driven ailerons you guys ever used on a fast plane without any flutter. I'd like to be able to dive this baby through speed runs with abandon.

It's basically a scratch build, so I can really search for some good light C grain balsa for the ailerons (which I will do anyway), but is it worth risking flutter for the asesthetics of having a single servo with no exposed linkages? I think I'm answering my own question here.

Please help me decide,
Joe

Super Splatter

I be tempted to shorten the ailerons 2-3 inchs with a razor saw and remake whats outboard of that back into the wing.

Then if nessesary use flexable medical tape to cover the outboard gap

wind junkie

My Feedback: (1)

The plane hasn't been built yet. I can build anything I like so I'm mostly wondering the best way to set it up now (total freedom do do ANYTHING at this point).

proptop

My Feedback: (8)

Besides doing what S.S. said, I'd make the torque rods out of 1/8" or even 5/32" (if possable ) music wire and making the ailerons out of as stiff (tortionally ) a Balsa as you can find.

You can also make the torque "rods" out of a larger dia. tubing.

I had a glass fuse. Banshee...don't remember if it was Skyglass or Airborne Associates right off hand, but I converted it to strip ailerons. I used 1/8" music wire for the torque rods, and used 1.25" aileron stock and stopped the ailerons about 3" from the tip.
Mine had a pumped K&B .61 for power and fixed gear (I was 16 and couldn't afford retracts back then, in '76 ) so it wasn't exactly what you'd call fast.

Mike Connor

My Feedback: (5)

I like the clean look, low drag and light weight of a single servo.
As mentioned you could shorten the ailerons and have tight stiff linkage.
Stiff ailerons are good but too heavy of wood could be a flutter problem.
The leading edge of the aileron should be as thick or thicker then the trailing edge of the wing.
Do not over bevel and seal a tight gap.
Pin or tape the outer end of the aileron during speed runs if there are signs of flutter.
If done right you should be able to avoid flutter at the speeds you will be flying.

wind junkie

My Feedback: (1)

Thanks for the good advice guys. Surprised to see so far nobody likes the two servo option-- that's good and that's what I was hoping for.

I guess a 10x6 at 18K wonlt really be record breaking fast on this plane. It will mostly just SOUND fast and eat up some sky. I will be doing retracts too.

Proptop, where do you fly in Rome? Firebirds? Paradise? I shop at Brennans whenever possible which isn't too far from you.

Joe

proptop

My Feedback: (8)

Hi Joe,
I usually fly @ Paradise...used to fly at Griffiss, until Empire Aviation moved in and GLDC gave us the boot.

bob27s

My Feedback: (19)

No need to really complicate this too much.... you will get good performance from the engine/aircraft combo, but we are not talking QM40 velocity here.

1) do not modify Jim Martin's design ..... !!! (blasphome!) Leave the ailerons as they are on the plans.

2) use HD aileron torque rods - 1/8" will be pleanty big enough. Goldberg use to sell a nice set of these I personally liked, but you can make your own. Key is in their installation - you want a tight bearing setup... no slop in the bearing, and the rod will not mechanically have slop in it. (review the torque rod installation for some of the QM40 and Q-500 aircraft.... I think DaveN has a link somewhere to a few posts).

My old Curare, Compensator, EU-1A and a few others all had s torque rod driven - single servo aileron installations. The EU1-A had some BIG ailerons. These were far-from-slow aircraft. Not an issue, but you must follow #3.

Yes the banshee has barn-door ailerons, but the span is not unreasonable. I saw quite a few of these aircraft fly, and all were build exactly as Jim designed the plane. Follow the plans. If you are concerned, using 5/32 tubing for the torque rods works nicely too. I would stick with what is on the plans.

3) SEAL the aileron gaps. That prevents your primary cause for flutter (differential air pressure bleeding through the hinge gap). Even a tight gap is not good enough. Must be sealed.

Bob

combatpigg

My Feedback: (3)

For slop free bearings, oil the rod and make the bearing out of "poured in place" epoxy.
Make sure the rod is perfectly straight in the bearing area and over dig the balsa a little where the bearing is going to be placed. You can use modelers' putty to make dams and the end points of the cast bearing so epoxy doesn't ooze out. Make sure that the torque rod is situated correctly, I like having it installed on the control surface already. Pour in enough 5 minute epoxy to submerge the torque rod, level off any excess. I use spackle to fill any minor depressions after the epoxy is cured. If you did a decent job of oiling the torque rod, you will have a nicely working part, if not, then get out the jackhammer and start over.[]

Mike Connor

My Feedback: (5)

My first attempt using this method required a jackhammer and I have been afraid to try it again. It has been awhile but it seems I used Vaseline rather then oil.

combatpigg

My Feedback: (3)

numero uno, if the 1/8" music wire is bent in such a way that the "axle" is distorted, then no amount of oil or grease will work. After forming the torque rod, it should be rolled on a flat to make sure it is straight with no wobble. The torque rod should be formed with the axle in smooth vise jaws and hammer the legs over. I've been doing it this way for a couple of years now. I used to use axle grease, but a drop of oil works just as well.

jaka

Hi!
You could shorten the ailerons slightly 100mm at the tips ...but this is not necessary if you just are certain to make the aileron linkage sloop free.
What I react too though is your plan to use a 10x6 prop on that pattern airplane...it will not work too well, as it will produce a lot of noice and no peformance.
Better use a 12x6 or 11x8 APC or RAM prop. A 11x8 or 11x7.1/2 prop was size to use back in the "old days".

bob27s

My Feedback: (19)

I like to use candle wax. Coats the metal fairly well.... and it provides lubrication afterwards

MJD

My Feedback: (1)

NOT on this engine! It is designed and piped to turn 18k plus. The 10-6 may perform a lot better than you think it will at those rpm. If not, at the worst a lower pitch 11" prop that lets the engine unload could be used.

MJD

bob27s

My Feedback: (19)

That is accurate..... 10x6 is about the largest prop you want to run on the engine ---

some folks have played around with 11x5 props, but that is really pushing it... and its not recommended.

Keep in mind the Banshee would be considered a "46" size plane in todays design world. It is not that big.

The 60LX is essentially a .46 size engine with big numbers.

wind junkie

My Feedback: (1)

Wow! Thanks for this wisdom! I have seen the epoxy pour torque rod bushing method referenced in racing articles. I will try that.

I agree that the Banshee really isn't all that big a plane. It's really not that much bigger than a 40 size Ultrasport. It has a thinner wing than a 60 size ultrasport.

I ordered the Jett 60 LX today! I have a 46 sitting out of a plane right now and Dub said I can use that to go ahead and build as the dimensions are the same. Actually, the 46 would probably be enough to fly it. It sure made my super kaos Jr scoot.

MJD

My Feedback: (1)

If it's that small then the 10" prop is obviously a non-issue. Let 'er rip!

Bob, or anyone - on this subject is there a quick short list of available 40 size pattern planes worth looking at for overpowered antics? I think you might have posted thoghts on this many months ago but I didn't find it in a bit of poking around.

MJD

rmenke

My Feedback: (13)

119

MJD

My Feedback: (1)

Cool, I will poke around and see if I can find some info on this one. Appreciate the long but not long-winded reply!

MJD

Edit #2: here it is: http://www.junorc.com/kits.html

wind junkie

My Feedback: (1)

Really? Is that really worth anything? I'm not looking to get every last mph out of this bird. If I need to choose I'd rather have a good handling one. I thought it was better to blunt the TE's (ie, 3/32 to 1/8") for two reasons:

1) easier to trim
2) adds weight leading to flutter

comments?

I have several high perf gliders with really sharp (ie, be careful not to cut yourself) TE's, but I always thought that was a no-no for powered birds with vibrating fire breathers up front.

Mike Connor

My Feedback: (5)

It sounds like this NASA web page is saying blunt trailing edges cause drag and turbulent air that could promote flutter.
http://www.grc.nasa.gov/WWW/K-12/airplane/shaped.html
None of my planes have blunt trailing edges and trimming is not a problem.
Some Q-500 kits come with 1/64" (not 1/16") ply to put in a slot in the trailing and leading edge of the tail surfaces. This allows sturdy sharp edges without adding much if any weight. I usually just sand the balsa trailing edges to a semi sharp point and cover.

MJD

My Feedback: (1)

Drag drag drag drag...

Yeah, it is used on lower speed aerobatic birds all the time as a way to purportedly (is that really a word?) soften trim issues around neutral and reduce flutter tendency, but I still need to be convinced.

If you've done your homework on the linkages, hinging and gap sealing, go nuts on the TE, get out the knife sharpener. Well, not that sharp, but thin is good - IOW finish the job on the airfoil.

MJD

bob27s

My Feedback: (19)

That is true - the not-so-sharp trailing edge tends to soften the effectiveness of the control surface around its center trim position. Forces the air to re-attach aft of the flying surface, rather than smoothly at the TE. That "space" is turbulence and drag.

No need to go nuts on most models. The 1/64 inlay helps you get a crisp straight edge, and provides "ding" protection -- ie, durability along with a fairly crisp edge.

But the molding and near-zero-thickness capability is why composite construction is popular for high performance designs. You simply can not get wood/foam that thin, and expect it to have any structural capability/durability.

MJD

My Feedback: (1)

I'd call a 1/64" thick trailing edge "going nuts", in relative terms at least! First I saw of this was on a couple of Doddger kits I got years ago. Once I get sick of my MagnumR, I'll toss the West .50 on one of those, they're lying around in a state of half completion.

rmenke

My Feedback: (13)

In summary;

Nassa's finds sharp trailing edges reduce drag. If anyone out there feels above Nassa level of research, good for you. If needed, inlay with 1/64 ply and sand to size. Option 1/16 pyl, a little stiffer and easier to work with. 3D machines, leave blunt trailing endes per recomendations of top pilots, designers and manufacturers, seal gaps to improve authority, also speed birds to help avoid flutter. Wheee