KenChoo

Hi Guys,

I've got a question about airframe handling in really gusty conditions: my plane flies beautifully in calm conditions, in strong but steady winds, and in light gusty conditions. But when there are moderate to heavy gusts, I have to be pretty focused and quick on the ailerons to keep the presentation looking decent.

I know this is normal, but I was just wondering (out of curiosity), are there any design features that people utilize to minimize the workload (on wings rocking) in heavy gusts?

Cheers,
Ken

Jetdesign

My Feedback: (8)

I'm gonna say it:

BALLAST!!!

Possibly the only benefit of a heavier airplane. Maybe there are better methods, but this is the most basic law of physics: F=ma

I am sure there will be answers about wing incidence, dihedral and anhedral, etc. But my personal experience is flying my airplane with 5000mah packs and 4000mah packs. It feels much lighter and more graceful on the smaller packs, but gets banged around a bunch in the wind. If I use the 5000mah packs I hardly notice it.

DRC1

My Feedback: (10)

What plane are you flying?

KenChoo

LD24,

Actually I'm happy with my plane as it is and I'm not looking for a fix. I was asking out of curiosity just to expand my knowledge. I don't want to bias the discussion based on my current airframe so I'll refrain from identifying it.

Cheers...

Ken

nonstoprc

My Feedback: (90)

A high and/or wing dihedral design can increase roll stability while an anhedral wing/stabilizer design improves maneuver-ability.

MTK

The main design feature that reduces wing rock in any gust conditions is wingtaper. The larger the root to tip ratio the lower the wing rock. There are no popular wings today that employ R/T ratios anywhere near large enough to maximize the effect.

But make no mistake even an infinite root to tip (triangular wing panels) will not eliminate wing rock. To eliminate wing rock, you'd have to cheat electronically with that new get up from Horizon that so many argued about a couple months back. Electronic fixes have nothing much to do with planedesign.....

bem

My Feedback: (1)

Maybemove the Center of Gravity slightly forward (battery slightly more to the front) on Your plane can help some in windy conditions.

/Bo

apereira

Kenchoo

Is that on the base line mostly ? Are you flying over a tree line?

Regards

KenChoo

Hi Apereira,

Yes, one of the two sites I fly at is more gusty and I do believe it is because of the tree line there. But back to my question about design qualities, thanks for the answers so far guys, very informative! Keep 'em coming. Cheers.

Ken

Alex Voicu

You can try adding some winglets at the wingtips for more stability. Some say they work pretty well:

[link]http://www.rcuniverse.com/forum/fb.asp?m=10899566[/link] post #274
[link]http://www.rcuniverse.com/forum/fb.asp?m=11194764[/link] post #876, comments lower in post #883

I use the bubble version as seen in the secon link. They do improve stability but i built them rather large so the added drag draws an extra 200-300 miliAmps from the batteries during a P13 flight.

najary

In my experience wing fences definitely improves the plane stability in stormy weather.

See posts 381 – 390

http://www.rcuniverse.com/forum/m_93...16/key_/tm.htm

Best regards,

Isaac Najary

KenChoo

Great stuff guys, thanks! And also to Alex and Isaac for including the links to the other threads! Really good reading.

Cheers,
Ken

serious power

Hi Joe,
You are correct to put this in this discussion. Have no fear of making this point as this is very appropriate to this topic.
I was going to do so in another recent thread relating to 'weight' and possible competitive advantage.
You should elaborate some more to help with understanding the relevance.
I will add some ;

This should be considered first ; P=mv. ( P being momentum)

A lot of us increase velocity (v) in wind - actually we are increasing momentum.
Your suggestion of adding weight (should this be at the wing tips ?? ) does the same thing.
Doing both will max,, the effect. Because one is multiplied by the other the increase in P is significant if either, and much more if both, are increased.

Getting to your F=ma ; Mass (m) here is dependant on or a consequence of m in P=mv.
Keeping this in lay-man's terms you are really talking about 'inertia' ; ' the measure of a body's resistance to changes in velocity or state of motion '.

However there are also aero solutions and if we were to take inspiration from the real gurus of aero , the F1 guys like Adrian Newey, we might really find a solution set that works well.
We don't really experiment all that much with this stuff and we should.
There is likely to be a 'magic' combination of physical (shape, volume and mass) and aero (devices, up-grades, band aids etc - be they fences ,sfg's, tiplets, winglets, turbulators etc) yet to be discovered.
Interesting topic well worth pursuing.

Brian

Jetdesign

My Feedback: (8)

The good thng to adding ballast is that it can be removed, and if you add weight in line with the CG it shouldn't change the way the airplane flies too drastically. Changing something like wing incidence or dihedral or something will affect the plane when it's windy and when it isn't. Nothing is free. I don't believe "lighter flies better" - it can't always be the case. A 2M plane that weighed only 1kg would fly like a kite. Everything is a compromise.

You can add weight wherever you want, depends on what you are trying to address. If you find the wings tip up and down a lot in the wind, tape a qarter to each in line with the CG. If you are fighting heading and elevation changes, weight at the CG (heavier battery).

Newton's Law (as most people are familiar): Force = Mass x Acceleration (techies understand this as force being directly proportional to a change in momentum).

*Acceleration: relative to the airplane, the wings tip gets blown upward. It accelerates from 0 (level) to some new position.
*Force: for this conversation, force is applied by the wind, can't change it w/o changing shape of airplane (really it's air pressure over area, which is related to Matt's suggestions about wing shape and changing the area)
*Mass: layman's terms, we'll call it weight.

Force = mass x acceleration, can be rewritten: Acceleration = Force/Mass

To reduce the wingtip accelerating up or down, you need to reduce force/mass. Can't change the force (w/o changing wing), but you can increase the mass by adding ballast.

To reduce the airplane 'jumping' in the wind, same thing. Airplane is accelerating upward relative to the airplane's motion. Can't change the force of the wind w/o changing the shape of the airplane, so to reduce that acceleration you can increase the mass.

The downfall to a adding weight: once the plane accelerates or the momentum changes, it requires greater force to stop the change. People like light wings because they stop more crisply after a snap. I don't have any snaps in my sequence, so that doesn't bother me; you need to pick your poison. I personally have liked my airplanes heavier in wind because the reactions from the wind are slower. I seem to notice the plane getting blown out before it's too far, and I find that if the wings rock it happens slower and less violently. I have heavy 5000mah packs and light 4000mah packs. There is a substantial difference in how they have handled in the wind with these different packs. My good flights in windy conditions are bigger and with heavier packs. My line is better and the plane feels like it tracks better which boosts confidence. On calm days, I can fly slower and closer with the lighter packs.