Roll in manouvers

Additional information:
The problem seems to be worse in outside loops/squares resulting in lineslack. The roll is clearly visible whit small control inputs like a shallow rollercoster.

I plan to offset the engine slightly, remove some tipweight and adjust the leadouts the next time I'm out trimming.

Regards
John

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johnosgrym
Rolling in manouvers Posted 9-17-2001 14:32

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Hi to all

I have a modified profile Cardinal. I've kept the wingspan but made the inboard wing 20 mm longer than the outboard wing. It's powered by a Stalker 46 SE and i use approx. 18 m lines.
Now the problem:
The outboard wing seems to react slower than the inner does and induce a roll. This is not fun during square manouvers. I've tried to enlarge the outboard flap with some success, I also moved the leadouts a thad backwards.
I'm still trying to trim it out but I'm soon out of ideas and my knowledge about the trim process could be improved on.
Anyone got some ideas?

Thanks

John Strandgård

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downunder
Roll Posted 9-18-2001 03:03

I once had a similar problem (although in the other direction) and the cure was to add a little tip weight. But yours sound to me as though there is too much tip weight. If by chance you aren't using any tip weight then add a little to the inboard wing.

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captcurt
Trimming Posted 9-19-2001 11:34

Well, I've been spending a great deal of trimming time lately. I'm no expert but I also think the first suspect might be tip weight.

You didnt tell us about the wings-level situation upright and inverted. With NO flap activity, get the wings level in level flight upright and inverted. If the outboard wing is low both upright and inverted, adjust it with weight. If it goes in opposite directions upright and inverted, then adjust that with flap tweaking or a trim tab.

In all the trim charts, this is the first step. There can also be some pretty difficult to diagnose roll coupling from rudder misalignment, and/or flying surface mis-alignment.

The above assumes parallel hinge lines between stab/ele and wing. This is a MUST! Even a couple of mm at the stab tip of misalignment will cause your rolling problem also.

Second will be to adjust leadout position so the plane is flying tangent to the circle. You may find it helpfull to add some contrasting tape marks to the plane to be able to see the yaw alignment from the center.

If there is another experienced flier available, have him observe the plane from outside the circle. Then have him or her fly the plane so you can observe--it will help you to correlate what you see from the center with what is going on at the plane end.

Hope this helps some..

There is more to do after these basics but I'll let the experts hammer on that (or me!) after you get started.

Curt

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JohnosGrym
Thanks guys Posted 9-21-2001 09:37

The last tweak on the plane was to remove about 5 grams from the tip. The wings still was horizontal in level flight. The improvement came in the overhead 8. The outer wing did not 'drop' as much as it used to do straight above my head. In the corners it looked and felt just as bad as before.

I'll remove som more the next time.

The leadouts are much scarier to fiddle with. To much forward and the end comes quickly. To the best of my eyesight the plane is flying all but in the tangent of the circle.

In Sweden the autumn is bringing wind and rain...
...and a lot of it.

John

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captcurt
Trimming Posted 9-21-2001 11:32

Hello Again!

I regularly watch the north polar weather synopsis and have noticed your weather---not real nice flying!

You want to be very careful with overheads and squares prior to getting the trim close. It can get scary very quickly. Also, tip weight and leadout position interact a fair amount so both need to be adjusted as you get closer to "ideal". Also, small changes (3mm or less) can make significant differences for leadout position.

Wishing you some better weather,

Curt
Near Detroit MI

PS: I worked on a couple of sailing projects many years ago with Peter Norlin--very famous yacht designer in Sweden.

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captcurt
Line length Posted 9-21-2001 11:51

Hi Again John:

I just converted your line length. If you are at 18M exactly, I wonder what your lap time/flight speed is. The cardinal is a medium large profile. We would probably fly one on 63-65' (19.2-19.8M) perhaps. It should have alot of line tension at 18M. But if you have slowed it down too much to get a reasonable lap time, it may be flying a bit slowly. 2 or 3 miles/hour can make alot of difference if you are at a critical area of the speed/lift curve.

Let us know how its going! Also, more basic info would be good.

Curt

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JohnosGrym
Speed Posted 9-21-2001 14:18

I try to keep the lap at around 5 sec. I've noticed that on faster runs the jerkiness in the corners gets 'better'. I tought it was because the increase of line tension, didn't think about the flying speed of the ship. A new factor enters the equation in my mind. Thanks captcurt.

Some pics of the Cardinals in Uppsala. The white one (being repared now) is mine. Now I'm flying with my second Cardinal (not in pics). Valle is the proud owner of the red one.
http:// hem.fyristorg.com/beachgarden/Cardinal/index.html

I'll return with some info on my plane.

John

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JohnosGrym
Ship data Posted 9-24-2001 21:45

After spending some time studying the plans and measuring the ship the following transpired:

Modell data:
Span: 1360 mm (inner wing +20 mm)
Length: 1030 mm
Wing Area: 37.4 dm2
Chord: 240 mm (without flap)
CG: 70 mm from LE
Weight: 1300 gram
Handle to trust-line: 19.2 m
Flap/Elev ratio: 4/5
Engine: Stalker 46 SE
Prop: 11x6 Master Airscrew Wood
Ground RPM: 8200
Lap time: 5.0 to 5.2 seconds
Fuel tank: 127 ml (7-8 minutes)
pics: http:// hem.fyristorg.com/beachgarden/Cardinal/index.html

Trim data:
Tip weight: 38 gram (ship up side down, wingtip on scale)
Inner flap area: 3.7 dm2
Outer flap area: 3.6 dm2 widened 8 mm to 4.0 dm2 (+11%)
Elevator area: 3.5 dm2
Leadouts: 32 mm and 48 mm behind CG
Rudder offset: None to slightly right
Engine offset: None

Any comments? Anything seem wierd?

Haven't had the time or weather to fly.

Regards
John

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captcurt
Roll Trim Posted 9-25-2001 11:35

After looking at your info, I only noticed a couple of things.

make sure the engine is indeed zero or slight "Measurement error bias" to the outside. Use a straight blade attached at the exact center, to the engine and measure to a reference mark about .3M aft on the fuse centerline. Be absolutely certain the thrust line is square or slightly "out".

Second, try to find out from someone else with a cardinal, regarding leadout position. It seem too far back, but I'm used to a little smaller plane. If something else was forcing the leadouts to be aft to compensate, then the outboard wing would drop on inside square corners if the plane is yawed out.

I would also pursue the line length/ flight speed issue as well.

I have some other info that might help--need your email address.

Curt
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I read your origanal post. I would satrt with the leadouts. hang it up in your garage or house by the guides.(both guides on one hook) Loosen the leadout slider. Let the leadouts go where they want. The trailing edge should be almost 90 degrees to the ground. This will be a good place to start. I usually do this with all my planes before I ever take them out to the field. I mess around with position and look for optimal results at the field. 99% of the time even after tip weight adjustments I always end up right where the original setting was from hanging it by the leadout guides.

This could be a tip weight problem but remeber if it a tip weight problem you will have the same effect on both turns. Yes planes do tend to roll in more on the outside turn but you have plenty of speed to counteract the forces at work here.

If the motor is on straight or even pointed outward just a tiny bit(I put a washer under each of the front lugs and that seems to be enough) Then you may have something out of alignment(flaps) or just bad leadout position.

It could be leadouts or level wing problem or both.

Make sure the wing is level in accordance with the lines.. It will never really fly good until it is correct. Have someone watch the plane as it flys by them inverted and upright. It is easy to tell when the plane passes the bystander and is flying away from them. The wing centerline should look like an extension of the lines. If it is out of level even a tiny bit make adjustments as needed. Tweaking the flaps or with a trim tab. Once this is set there should be no reason to need to do this again. Unless you have to tweak flaps. Sometimes they will return to thier original settings. You may have to tweak them several times. After a few times they will stay. I always build an adjustable trim tab for this very procedure.

Hope this helps. Let us know how it turns out.

Doug Moon

I first taped a smal piece of 1/32 plywood to the flap and the results were very apparent. Then I went home and glued a piece to the flap. Next time out, I trimmed it to final size.

Note that this is an assymetrical wing modification as well.

FWIW

First a big thanks for all your input.

This weekend I was out trimming. I have a 8mm plastic sheet widener on the outer flap. I remounted the engine with washers under the front screws for a small offset. During the first flight i felt a improvement, maybe only in my mind. For the second run I removed som tipweight. Both me and my friend saw that I have a slightly warped wing. The hinging problem was better anyway. For the last run I took of the flap widener and the roll was back but not as mean as it used to be.
I think the solution is to tweak the flaps for the warp, adjust the tipweight and reenlarge the outer flap.

My next project will be the builtup Cardinal in .40 size and I'll stick to the plans with symetrical wings.

John