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Old 10-24-2007 | 08:06 PM
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bobmac010
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From: Poughkeepsie, NY
Default RE: Attitude on the Ground?

Da Rock,
IF the wing is carried along on the takeoff at an AOA that does not produce positive lift, you COULD be in trouble. Maybe so, maybe not. Try it and see.
This has to be a pretty steep angle for the elevator/horozontal stabalizor not to rotate the plane to at least a neutral attitude.
Either that, or a flying wing configuration, but that's not what we are talking about here.

You also mentioned that the elevator will probably pitch the wing at some point down the runway...
This is absolutely true, onless you made a gross error and have the nose pitched downward 15 degrees or more while sitting in the pits.

I want to side track a little, hope you don't mind... It is relevant.
When I first started to run through this forum, I was slightly anoyed by Mr. Hanson stating that CG does not matter in another forum. He has a great mind, although, not to disrespect Dick, he thinks a little bit out of the box.
He was speaking as the model gets smaller, the rules of aerodynamics gets more lax. You do not have to be so precise in your formulas, and you can be a little more "free" in your design.
I have gained a new respect for Mr. Hanson.

Now, getting back to the ground attitude.
Yes, Meadan, it has a lot to do with "Your" attitude on the ground.
What do you prefer? Are you a novice that like "easy"? Are you an individual that strives for perfection and realism, or just someone that wants to have fun and get into the air?

When you get to the .40 size model, there is a lot that can be changed to make it handle where you are comfortable with it.
If you expect a plane that is on the ground to STAY onthe ground, give it a negative attitude, no more than 7 or 8 degrees.
If you want to have a plane that handles much like a scale plane, then give it a positive attitude on the ground, again, no more than 8 or 9 degrees, (speaking from experience).

Aerodynamics is not proportionate to scale, and transition from ground attitude and flight attitude is a direct result of aerodynamics.
What does this mean?
You can "play around" and deviate from the norm up to a certain extent. And as Da Rock alluded to, nobody dies if the plane augers in. It is, however, an out of pocket expense... Glue, balsa, or even a new kit...

I mentioned in earlier that all I have in my hangar are tail draggers.

There are 4 reasons why this is so...

1. They are easier to setup. You do not have to sinc the nose gear and the rudder.
2. They are lighter than a trike configuration.
3. I don't have to worry about the AOA at ground attitude.
4. I think that they are really cool.

Yes, thay are more difficult to handle on the ground during take off, but so is a bicycle if you have never ridden one before.

Grits,
If your plane sits with a little negative attitude, try it. If you don't like it, change it. If you still don't like it, make it a tail dragger.
(just kidding).
I think it will do just fine.

Go out and have fun.
Let us know how it turns out.

Bob