wind worthy factors

[Mike Stramba]

Hello all,

I'm a newbie to rc, yet to fly a *real* rc plane, (have played with some of the sims), just in the readin' & research phase right now ;)

Question: What determine how 'wind worthy' an rc plane is ?

I guess as a general rule, a heavier / faster plane can handle more wind ??

The question I have, is *how* much heavier / faster ?

Let's say we're measuring from a 'no wind' condition to 10-15 mph . or higher ?

For speed, I'd assume you want some margin of airspeed over wind speed. How much ?

As for weight, what would the range be for say from a 'no wind only' slow flyer , to one that could handle 10-15 mph of wind ?

What rule of thumb / calculations would you use to connect model weight / power / wing loading to "wind speed penetration" ability ?

I've played with motocalc a bit, so I've seen some of the numbers, just wondering how you would calculate / guesstimate them manually.

Mike

[Dave Robelen]

Hello Mike,
What a nice question! If we were simply talking about the ability to penetrate and move around in a wind, low drag and a healthy power loading would be ample. The real test is the turbulence that comes with the wind. most of our "real world" sites have trees, buildings, etc. somewhere upwind of our flying area.
There is a pretty distinct link between the ability to fly in turbulent conditions that include the basic wind, And that pretty much comes down to wing loading. The higher the wing loading, the steadier the flight path. Of course, as the wing loading climbs, so does the landing speed and the need for still more power to manuever. Meanwhile, the concept that "bigger is better" works wonders here. A large heavy model Has much larger values of inertia that resist being tossed around, so that is a basic reality.
Assign numbers? I would feel very comfortable flying a 2 meter sailplane in a 10-15 mph breeze if I was out on an open field where there was very limited turbulence. Put a stand of trees upwind, and I would want to move up to a fairly powerful model with a wing loading of say 16 oz./sq. ft. The problem with your question is that it is just as heavily influenced by the proficiency of the pilot as the weather conditions. Another issue nowadays is the artificial stability that can be had by installing rate gyros as dampers to unwanted motions. I am flying a ball bearing sp280 powered model that really bounced in the turbulence until I installed a gyro in the roll axis. This increased the ability to fly smoothly in rough conditions quite a bit.
Take care, Dave

[Dr Kiwi]

Originally posted by Dave Robelen
Another issue nowadays is the artificial stability that can be had by installing rate gyros as dampers to unwanted motions. I am flying a ball bearing sp280 powered model that really bounced in the turbulence until I installed a gyro in the roll axis. This increased the ability to fly smoothly in rough conditions quite a bit.


I apologize for leaping in at a tangent here, Dave, but your correspondence raises a question in my blissfully ignorant mind. What are the pros and cons of using [a] one or even two gyros, versus [b] say, the FMA Co-pilot system? Apart from allowing expert pilots like yourself to fly in less than ideal conditions, it would appear that it could be handy to utilize the gyro as a training aid. Then, by adjusting it's degree of over-riding control, a novice pilot could reduce their dependence on the gyro as their flying skills improved - does Co-pilot allow one to do the same (i.e. can it be adjusted to decrease its effect)? Cheers, Phil

[Dave Robelen]

Hi Dr. Kiwi,
I cannot say for certain, but there has been no indication that the co-pilot has a variable sensitivity. The recent review in the Backyard Flyer did not mention such a feature.
The gyro has a completely different effect. It does not try to restore the model to any particular attitude like the co-pilot. Rather, it reacts to a motion that is not commanded by the pilot. For example, if I am flying level in gusty weather and a gust causes a left roll motion, the gyro would immediately command a burst of right aileron to counter the displacement. This response is completely adjustable from a very mild effect to very rapid reactions.
The reason a gyro can be useful is that it senses the disturbance more rapidly than you would see it. For a model pilot to react to a disturbance, the model has to move enough to be visibly displaced, and then you can attempt a correction. Meanwhile, the gyro does not interfere with the signals coming through the receiver, so that the pilot can manuever the plane in a normal fashion. The general effect is to make the model "feel" much larger in gusty weather. This is the principal difference in a gyro and the co-pilot. With a gyro on say, ailerons, I can do a 4-point roll and leave the model in the knife edge attitude without the gyro attempting to right the plane. With the co-pilot, the model would pop back to level flight as soon as I released the stick.
A gyro is a useful tool to any level of pilot since it's only function in an airplane is to smooth out the flight in turbulence. I am a little surprised that tthey have not been promoted more.
Regards, Dave

[Mike Stramba]

Dave,

Assign numbers? I would feel very comfortable flying a 2 meter sailplane in a 10-15 mph breeze if I was out on an open field where there was very limited turbulence. Put a stand of trees upwind, and I would want to move up to a fairly powerful model with a wing loading of say 16 oz./sq. ft.


Ok thanks that gives me a bit of an idea. I guess it becomes a subjective decision at some point, as you said, depending on pilot proficiency / preference.

I assume your 16 oz/sq ft figure comes from a bit of past experience ;)

Another issue nowadays is the artificial stability that can be had by installing rate gyros as dampers to unwanted motions.

Hmm, interesting. With the rate gyros installed, would that change the wing loading you'd choose ?

Mike

[Dave Robelen]

Hi Mike,
The 16 oz/sq.ft. assumes a model in the .40-.60 range. If I were to move up to the Giant Scale models, that number could increase substantially. There are so many variables in "real world" wind decisions(including a lack of on site measurements) that the call "to fly or not" must be a judgement issue.
There are two factors involved. Obviously the model must be able to move around safely without being blown downwind. Additionaly, if it is an aerobatic type, the model must fly fast enough to be able to shape the manuevers in the wind.
Adding rate gyros would not help in the first case where penetration is the issue, but when the wind involves turbulence (as it usually does) having the added damping makes for a much smoother flight.
The fact that I would not reccomend a beginner attempt flying in the wind makes the issue of a gyro being helpful to a novice a bit acedemic.
Regards, Dave

[Mikerjf]

Had this posted on another site, figured I'd paste my 2 cents here too.


IMHO anything capable of about 30mph is OK and generally planes with a higher wingloading get knocked around less (there are a lot of exceptions to this) but personally I find the planes that have good low speed characteristics to be the best all around. Our local field allows for no mistakes down low, any mistake results in a miserable trek through thick underbrush/swamp or a boat ride that usually takes about an hour. My FMA Razor's collecting dust because of its low speed tip stalls but I fly my Elipstik (exception) there all the time (great low speed traits). In my case I think it's got a lot to do with visual reference. In a changing wind it's difficult to determine airspeed, if the Razor gets slow in a turn it's gone the Elipstik just dribbles a bit and keeps flying. Same holds true with my Sporty and Tumblewatt, both fly well in the wind but if it's gusty and turbulent I prefer the Tumblewatt as it's more forgiving.

Mike