Roll Axis Trim, flapped vs. unflapped

Assuming optimal trim, do the best flapped planes have an advantage over the best unflapped (Doctor, Medic) when it comes to keeping the bottom of the wing out of sight (to the pilot, I mean--to the spectators would be a real trick ) on inside maneuvers, especially square/triangular corners, and likewise top of wing on outsides?

How close is it possible to come to seeing only the inboard tip of the wing throughout the pattern with the very best possible flapless planes in decent weather?

How big a factor is chord taper on unflapped designs in terms of roll stability?

Thanks,
Kim Mortimore

whether flapped or unflapped, if you are seeing the plane make significant rolling moments in maneuvers it is not trimmed properly. The flaps give you an additional easy way to affect the roll trim, by tweaking the flaps, not having flaps shouldn't make the plane roll. If it does, go through the trim chart and adjust wing warp, the leadout position, tip weight etc. to get it to fly straight.

I think he is talking "wiggle" or "banging" in the corner. You go through a sharp corner and the outboard wing drops. Here if you have moveable flaps you can make the outboard flap larger (longer if not full length, wider, or add a "wart") and this will allow you to carry more tip weight for level flight while keeping the wing from dropping.

If you have equal size moveable flaps, then one may not be any better than the other. If your inboard flap is larger, ho boy, are you in for a ride! Then the non-flapped ship would be better (but if the inboard wing is larger, not much). Edit: "Significantly larger"

>whether flapped or unflapped, if you are seeing the plane
>make significant rolling moments in maneuvers it is not
>trimmed properly. The flaps give you an additional easy way
>to affect the roll trim, by tweaking the flaps, not having
>flaps shouldn't make the plane roll. If it does, go through
>the trim chart and adjust wing warp, the leadout position,
>tip weight etc. to get it to fly straight. Phil C

Do you find much difference in the way your big, relatively thin (%wise), tapered, blunt, way-forward high point Gotcha/Psycho/Streak wings respond to trim adjustments compared with untapered Flite Streak/Skyray type flapless wings?

>Pretty close, I would say. There's really only three
>adjustments, instead of about half a dozen, to play with -
>tip weight, rudder angle, and leadout position. Somewhere in
>the archives is a tale of how Jim Aron and I got his wife's
>"Medic" to go from no line tension in level flight and WILD
>hinging in the maneuvers, to flying like it was on rails, by
>adding a tiny rudder tab and adjusting the other two around
>it. Just play the yaw angle off against the tip weight.

I did a search all the way back using ARON AND MEDIC, which captured this current thread only, so maybe it's really old, or I am search-challenged. How wide was the range of adjustment on tipweight and leadouts from dog to flying on rails?

How about forward up leadout (with say about 3/4" separation to avoid connector interference]? Does it make much difference on a flapless plane?

Thanks,
Kim

Most people find it pretty easy to trim the Gotcha/Psycho/Streak planes to do nice tricks(as Howard says). Basically get the wing straight so the plane doesn't roll more when turning one direction vs. the other, and then play with the tip weight and leadout position. I haven't flown many straight wing planes, but it appears that they are a bit harder to trim for the reasons Brett says.

The main problem with this kind of plane for precision maneuvers is that the lines tend to jerk the plane around. A 30 ounce plane on .015 lines really needs to fly about 80 mph to keep the lines from whipping around and upsetting the maneuvers. At 55-60 mph speeds it takes a lot of care in balancing speed of control movement, correcting for the wind, following the plane with your hand, and just general finesse to keep the plane flying smoothly.

>Most people find it pretty easy to trim the
>Gotcha/Psycho/Streak planes to do nice tricks(as Howard
>says). Basically get the wing straight so the plane doesn't
>roll more when turning one direction vs. the other, and then
>play with the tip weight and leadout position. I haven't
>flown many straight wing planes, but it appears that they
>are a bit harder to trim for the reasons Brett says.
>

The Gotcha-type planes are really excellent stunt trainers. When you take away the glitz, there really isn't much consequential difference between an unflapped stunt plane and a slow combat plane. I think the trim would have to be different to some extent, because you never really have to fly the stunter upwind or crosswind. Most combat planes I see have the leadouts WAY further aft that necessary for a stunt plane. I presume it's right for combat, of course, since I really don't know enough about the requirements to say otherwise.

Combat planes tend to be light and have thick lines, hence the farther-aft leadout-guide position to fly tangent to the circle.

<< How wide was the range of >adjustment on tipweight and leadouts from dog to flying on rails?
>How about forward up leadout (with say about 3/4" separation
>to avoid connector interference]? Does it make much
>difference on a flapless plane?

I see I really didn't answer these questions.

I find that with the Streak 2000 I use a range of about 1 in. for the leadout position, depending on the wind. I run the lines directly to the bellcrank and use three leadout guides half an inch apart. The front guide is about 3/4 of an inch behind the CG. I usually run the lines through the same guide or put the down line half an inch back.

Tip weight has a range of about a 1/4 oz. with a total tip weight of half an ounce.

Once you get those two things in line(The Streak 2000 doesn't have enough rudder to bother tweaking). How it flies depends on the pilot. Flying smooth is all up to the pilot. Even .015 lines are enough to whip the plane around in sharp corners, so the pilot has to keep things under control with lots of finesse on the controls and leading the plane around with hand movement. I've never been able to find the rails in the sky though.

>Assuming optimal trim, do the best flapped planes have an
>advantage over the best unflapped (Doctor, Medic) when it
>comes to keeping the bottom of the wing out of sight (to the
>pilot, I mean--to the spectators would be a real trick )
>on inside maneuvers, especially square/triangular corners,
>and likewise top of wing on outsides?

I think your underlying theory is probably incorrect - it's probably easier to trim a no-flap design than it is a flapped design. Wild Bill pointed this out a long time ago - the lateral motion of the CP tends to be much less predictable once you throw flaps into the mix.

>How close is it possible to come to seeing only the inboard
>tip of the wing throughout the pattern with the very best
>possible flapless planes in decent weather?

Pretty close, I would say. There's really only three adjustments, instead of about half a dozen, to play with - tip weight, rudder angle, and leadout position. Somewhere in the archives is a tale of how Jim Aron and I got his wife's "Medic" to go from no line tension in level flight and WILD hinging in the maneuvers, to flying like it was on rails, by adding a tiny rudder tab and adjusting the other two around it. Just play the yaw angle off against the tip weight.

>How big a factor is chord taper on unflapped designs in
>terms of roll stability?
>

Taper helps to some degree. Lots of lift at the tips seems couples the roll and yaw more (which I think is a big factor in the "tiny rudder tab" effects above. Ted and I have been talking about taking a Doctor wing and putting in some taper to allow it to handle turbulence better, but it would probably make it even easier to trim, too.

A couple of passing comments. I built a fast combat airplane to fly for fun when I need to break out into a sweat. I put in adjustible leadouts. Guess what--they are as far back as I can get them. I had thought you combat guys were nuts for putting them back that far.

I really think both leadouts need to come out the same hole and I do my 1/2A's that way. On a 15 size airplane 3/4 in separation will give a noticable (if you watch for it) wiggle when you go from one way to the other, as in the intersection of round figure 8's.

>I really think both leadouts need to come out the same hole
>and I do my 1/2A's that way. On a 15 size airplane 3/4 in
>separation will give a noticable (if you watch for it)
>wiggle when you go from one way to the other, as in the
>intersection of round figure 8's.
>
>Jim Thomerson

On one of my 35 size planes I used ~1/4" separation with the up leadout enough shorter than the down so the connectors/wraps couldn't touch each other, and my handle cable adjusted to match (sure would be excitin' to fly if your handle cable wasn't adjusted to match ), and it felt less weird to have a longer up handle cable than down. I never tried allowing the connectors/wraps to rub together on the off chance that maybe it wouldn't cause a problem (is there an emoticon for "chicken"?) How do you arrange the connectors on your 1/2A's, or does it not much matter on the little 'uns?

The speed guys connect the lines at the bellcrank and have both flying lines come out the same hole. At first I thought that would lead to excessive wear at the wing tip guide, but with their heavy solid lines and very limited control action, it isn't a problem.

I've been moving the leadouts forward and compensating with thrust line placement and tip weight. A lot of F2D planes are now trimmed similarly. When the motor quits the plane turns in about 5 degrees. You can see the whole leading edge. this style of trim seems to reduce the effects of the lines whipping around in quick switchbacks and similar maneuvers, if the plane is going fast enough and doesn't slow down too much in maneuvers.

Hi Kim

The main reason for rolling is that in the spanwise direction, the CG and centre of lift are misaligned. In level flight, line tension tends to keep the wing more or less flat. In a loop, lift and opposing inertia are much greater and when misaligned form a force moment couple that rolls the plane. If you see the bottom of the wing in a loop, your CG is too far outboard and you need to reduce tip weight. No amount of mucking with other trim options is going to fix the basic problem.

All this is assuming equal flap movement of course.

I realise this view is not shared by all but it works for me.
I can calculate the correct CG if you give me span and line length to the geometric centre of the wing. You might be surprised by the result so I suggest gradually adjusting tip weight toward this CG and just see what happens.

Regards,
Ken

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