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Flaperons on an Avistar

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Old 09-10-2004, 09:57 PM
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-pkh-
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Default Flaperons on an Avistar

I'm getting my Avistar ARF tomorrow, and I'm considering trying to install two servos for the ailerons (one each), so I can use the flaperon mixing on my radio to get flaps as well.

Anyone else try this with the Avistar, or other similar trainer plane?

I think I can mount two, side-by-side (with servo arms point out, away from each other), without notching out anymore wing ribs, but then I may have to much of an angle on the control rods. I will have to make a new servo mount for them and cut out a larger section of the wing's bottom sheet to fit them. If I move the servos out to have the arms point inward (towards each other) and get the control rods perfectly straight again, that will require cutting out separate holes for each in the bottom wing sheet, and possibly notching out another wing rib (besides the root rib that is already notched).

Any comments, suggestions?

I thought about just building it as spec'd and screwing around with adding another servo later, but then I figured it would be much easier to build it this way from the start, and not have to break off the epoxied single servo mount later...
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Old 09-10-2004, 10:18 PM
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gus
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Default RE: Flaperons on an Avistar

Ask yourself why you want flapperons... "Why do I want flapperons?".

If your answer is "for fun", "to experiment with 3D stuff", "because I can", then go ahead and install flapperons.

If your answer is " so that i can slow down for landing, get better take-offs, or maybe more stable, slow flight", then you do not want flapperons. The Avistar has fantastic slow speed flight. It floats, and if you use flaps then you probably will struggle to get the plane on the ground.

For typical usage (as intended by the designers), the Avistar is *really* good. It has one aileron servo because that is all it needs (you are not going to be doing 3D with the avistar....)

Frankly, the plane is not going to be any better (for it's inteded purpose) with the additional servo on the aileron. It is overkill.

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Old 09-10-2004, 10:41 PM
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Default RE: Flaperons on an Avistar

Gus,

The main reason I want flaperons is for more lift for slower flight and landing/takeoffs. The Avistar has a semi-symetrical airfoil, and I've read it has about a 35mph touchdown speed...
http://www.masportaviator.com/ah.asp?ID=48&Index=6

I believe that the flat-bottomed airfoil trainers have a much slower touch down speed. I just figured it would be nice to get flaps on the Avistar to get the slow speed performance of the flat-bottomed trainers, especially for take-off and landing. The main drawback I've heard about the Avistar for a beginner is the faster speeds required for take-off and landing... and flaperons would seem to help here...
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Old 09-10-2004, 11:09 PM
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Default RE: Flaperons on an Avistar

35MPH?! That doesn't seem right! My tiger 60 touches down WAY slower than that.. And it has a fully semetrical wing. Anyways I think flaperons would be fun on trainer types. You could have a sort of bush plane.. Flaps bigger tires and a bigger engine and voi la perfect bush plane. If you still want to do the flaperons then go to your LHS the owner is bound to have planty I dea's for servo trays or look at other planes servo trays for Idea's.
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Old 09-11-2004, 01:01 AM
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Default RE: Flaperons on an Avistar

I was told stall speed for the avistar is around 15-17mph
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Old 09-11-2004, 05:47 AM
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Default RE: Flaperons on an Avistar

Nothing wrong with trying the flaperons, but I too wonder about the effectiveness on a trainer, even an Avistar. It may land a bit faster than flat bottom wing trainers, but I doubt that it's substantially faster.

Remember too, that flaperons will likely cause a change in pitch when applied, which will mean having to "get on the elevator" when deploying them, or trying to mix some elevator with the flaps. What I'm saying here is that most beginners have their hands full just trying to learn the basics, without having to deal with bells and whistles.

However, adding the flaperon capability now does not mean you have to use them now. You could leave the function disabled until you've learned the basics, then kick it in later on.

Whatever you decide, have fun!

Oh, and I'd place the servos side by side. As ,ong as the angle isn't really severe, it shouldn't be an issue.
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Old 09-11-2004, 09:48 AM
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Default RE: Flaperons on an Avistar

A guy at my club has an Avistar, and it does seem to come in faster than the the flat bottomed trainers, like the Sig Kadet. I don't have any idea what the absolute speed numbers are, so I'm just quoting what the AMA online mag, Sport Aviator, said in their Avistar evaluation article.

I figured I might not use the flaperon mixing initially if it gets to be too much for me to deal with. Installing the dual servos with initial construction seems the cleanest way to do it, and gives me the option to use the mixing or not. I've flown a couple planes in RealFlight G2 with flaps and liked them. As far as "Real" flight goes, though, I've only flown a friends plane on a buddy box, once. He had flaperons, but we weren't using the flaps (at least I wasn't). It was only for a few minutes, but I got to do some loops and rolls and had quite a lot of fun! Can't wait to get mine assembled!
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Old 09-11-2004, 12:45 PM
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Default RE: Flaperons on an Avistar

The artical sounds like BS to me... atleast those speed numbers do.
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Old 09-11-2004, 08:12 PM
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Default RE: Flaperons on an Avistar

The Avistar lands quite slowly -- whoever told you 35 mph, doesn't know what they are talking about. I've also done the flapperon thing on trainers & it is largely a waste of effort -- trainers land slowly as it is, & the flapperons end up never being used. The real advantage with the dual aileron servo set up is the reduced liklihood of aileron flutter because the linkage is tighter than the torque-rod set-up for a single servo -- otherwise there is no advantage.
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Old 09-11-2004, 08:58 PM
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Default RE: Flaperons on an Avistar

i have a allpha trainer how would i go about taking the di herdral out of the wings
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Old 09-11-2004, 09:42 PM
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Default RE: Flaperons on an Avistar - DONT

Flaperons are a bad idea on most RC airplanes.

When you deploy flaperons, you are increasing the angle of attack on the outboard portion of the wing relative to the inboard portion. This means that the outer part of the wing will stall before the inner part of the wing.. The dreaded "tip stall." The plane will be less stable at slow speeds than without the flaperons deployed, and you're much more likely to spin it in if you get too slow. This is the exact opposite of what you want!

Look at full scale airplanes, you'll see that flaps are always inboard. Spoilers (if exist) are outboard. This is by design to improve handling and stall characteristics in slow flight.

If you want to get a plane to slow down for landing and be more stable, the right thing to do is mix spoilerons, which reflex each aileron slightly *up.* This will force you to fly at a higher angle of attack (read increased drag), and will help the inner portion of the wing to stall before the outside (where the ailerons are). This will help the nose to drop, while still maintaining some aileron control in a mild stall. Your plane will last longer.

I know this is backwards from what it sounds like it should be, but there are some really good reasons for not using flaperons on most models. Spoilerons can come in handy, especially in wind, I have them programmed on several models.

IMHO, dual aileron servos on an Avistar is not really necessary either, when you're ready to benefit from independent servos, you'll have outgrown your Avistar anyway!

Have fun with the new plane! Chuck
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Old 09-12-2004, 08:10 AM
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Default RE: Flaperons on an Avistar

CliffR,

Taking the dihedral out of a built wing will require major surgery (And I DO mean MAJOR!).

You'd be better off building a new wing, or better yet, stepping up to an intermediate plane.
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Old 09-12-2004, 10:07 AM
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Default RE: Flaperons on an Avistar - DONT

ORIGINAL: cczarnik

Flaperons are a bad idea on most RC airplanes.

When you deploy flaperons, you are increasing the angle of attack on the outboard portion of the wing relative to the inboard portion. This means that the outer part of the wing will stall before the inner part of the wing.. The dreaded "tip stall." The plane will be less stable at slow speeds than without the flaperons deployed, and you're much more likely to spin it in if you get too slow. This is the exact opposite of what you want! ...
Not sure what you mean by the outboard being different from the inboard here... the Avistar has full length ailerons that run from the fuse to the tip of the wing...
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Old 09-12-2004, 10:20 AM
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Default RE: Flaperons on an Avistar

Seems like alot of work for very little return. Why would you want to land any slower then the Avistar normally lands? All this will do is get you used to landing real slow then when fly a plane that needs more speed to land you will stall it and crash.
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Old 09-12-2004, 10:30 AM
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Default RE: Flaperons on an Avistar

cczarnik is referring to a conventional outboard aileron installation -- and he's correct in that regard. However, the Avistar & virtually all trainers have strip ailerons, so tip stalling with flapperons isn't a problem -- but the flapperons add little to a trainer (unless it is very nose heavy).


Taking the dihedral out of a wing is much less work than building a new wing.

Cut the wing with a band saw (or whatever you have available)

make a new straight-across wing joiner

Cut rectangular openings in the inboard ribs adjacent to the main spar for the new joiner

epoxy the new joiner into place

make wedges to fill the gap at the inboard ribs & glue into place

reinforce the joint with fiberglas or 1/32 balsa sheet (grain crosswise)

re-cover the center section

go flying
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Old 09-12-2004, 11:08 AM
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Default RE: Flaperons on an Avistar - DONT

You're right, didn't realize that ailerons come all the way inboard on an avistar. Chuck
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Old 09-12-2004, 12:46 PM
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Default RE: Flaperons on an Avistar - DONT

Two things here. First of all with regards to the question about taking the diehedral out of an alpha trainer wing. I have done this to two of them. Just find the exact center point of the aluminum brace rod and bend exactly at that point so that when it is installed, the wing is flat. After being bent, the rod needs to be installed with a specific orientation and then CA'ed a little bit so that it won't turn. This worked great on both Alphas. The wing halves don't come exactly together anymore but it don't make a hoot. Just wrap some packing tape or ultracote around the wing in the middle.

I have found flaperons to be an absolutely blast on a 3D Magic funfly plane. I use mixing to program in some elevator when they are turned on, and also some more mixing with throttle to compensate for ballooning when the you punch it. I have found that you come be coming in very hot and high and flip on severe flaperons and it is almost like popping a drag chute. You can see it plow to a crawl. However, don't use them for landing in high wind. The plane is more touchy, no doubt about it. I use two settings. Mild flaperons, and sever flaperons. You can use the mild setting for landing and the radical setting for bleeding speed. With full flaps, you have reduced aileron control, but you would not believe the braking and lift. For taking off with full flaperons with a 61 fourstroke on a four pond plane, when you punch the throttle, you better be ready to fly and I mean right now. It basically just lifts from the ground, and the computer mixing between throttle and elevator helps take the baloon out of it.
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Old 09-12-2004, 01:26 PM
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Default RE: Flaperons on an Avistar

Well, I got my ARF, and had a look at the wing and aileron servo mount, and it looks like a no-brainer to put in two servos. Just have to cut out a little more of the bottom wing sheet and make up a new servo mount to fit two servos side-by-side. The existing mount is just a piece of 1/8" plywood (with the center cut out to fit oneservo) and a couple of balsa blocks that glue it to the wing.
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Old 09-15-2004, 02:01 AM
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Default RE: Flaperons on an Avistar

I'd say go for it pkh, if you have the dough, why not? The only reason not to do it is because most people don't think it's worth the money. But if you've got cash to burn and want to experiment, I say go for it. You can definitely go without flaps but then you'd just have a run of the mill trainer. With flaperons, you could take off sooner, land slower and haul more. You could also deploy spoilers upon touchdown like a real plane. I think that would be very cool.

Be cautious though. As someone mentioned earlier, make sure you apply flaps for the first time at 2 mistakes high. You'll have to mix some elevator in incrementally so just make sure you are at a safe altitude before you turn that dial (or flip that switch)!
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Old 09-15-2004, 02:19 AM
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Default RE: Flaperons on an Avistar

Double posting by accident
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Old 10-01-2004, 09:40 PM
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Default RE: Flaperons on an Avistar

Just a follow-up...

I finally got my ARF together, and have flaperons setup on my Avistar (see the pictures below). It was pretty easy to make up a dual servo tray for the wing. I flew it for the first time today, with the help of two very experienced club members! I was able to take off a few times on the second tank, and I landed by myself on the third tank! Nice calm day... very nice for a newb to fly!

I haven't messed with the flaps while flying yet, so can't say how they work... will post another update after I've soloed and had a chance to try them out (I'll let you know if it was worth the extra effort ).
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