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Old Jan 25, 2005, 01:51 PM
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maciek's Avatar
Worcester, Ma, USA
Joined Feb 2001
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design for flying in wind

I'm pretty happy with my ap platform, http://www.rcgroups.com/forums/showthread.php?t=321059, but I wish it were easier to fly it in the wind. I've been thinking that if I replaced dihedral with wing sweep, the plane would still be stable in roll, but less succeptable to wind. Am I right?
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Old Jan 25, 2005, 03:31 PM
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Vince inTX.'s Avatar
Santa Fe, Texas
Joined Oct 2002
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If you have power to spare, why not just ballast her up. Add about 8 oz under the cg and see how she handles the wind then. It is more about wing loading than anything else

Vince
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Old Jan 25, 2005, 04:05 PM
Team HeliProz
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Saint Clair, MI
Joined Jan 2004
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Add weight, Add power, Add a co-pilot!

Hands off AP!

Matt
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Old Jan 25, 2005, 05:27 PM
Enjoy Life B4U Die!
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United States, GA, Powder Springs
Joined Dec 1999
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Add a thinner wing - I have an assortment I use with my a/p planes - helps with wind.
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Old Jan 25, 2005, 05:37 PM
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São Paulo - Brazil
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To fly up wind all you need is a light aircraft model, and a thin airfoil, dihedral is not important.
A good choice for airfoil is the MH 32, but using turbulators on near LE, I personally use two strips of balsa inside airfoil ribs, and of course the main spar, at maximum 37% of wing chord.
My Super Onion, has the ability to fly in strong winds 15kts and be a good Platform for my AP’s, but a powerful engine is more than recommendable.

Cebola
Brazil
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Last edited by Cebola; Jan 25, 2005 at 05:44 PM.
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Old Jan 25, 2005, 07:56 PM
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wakumann's Avatar
Canada
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Quote:
It is more about wing loading than anything else
Hi Vince
guess you never fly slope models, otherwise you would realize it's not the just wing loading. There some things like airfoil, planform and dihydral which have much more influence.



Cheers
Thomas
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Old Jan 26, 2005, 03:18 PM
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popop's Avatar
Duckcity
Joined Feb 2002
319 Posts
This is my answer to windy days :
Oly Race



1.30m
1.5kg
50g/dm²
Near 200W/kg
11% semi-symetrical airfoil
No diedre
in line shooting
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Old Jan 26, 2005, 04:29 PM
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Santa Fe, Texas
Joined Oct 2002
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Wakuman,

When you are at the slope and the wind gets too high for your plane to fly in do you always pull another plane out of the car. If so I would bet that the plane you pull out has a higher wing loading than the one you just put away. If you only bring one plane to the slope and the wind gets to high do you pack up and go home or add ballast and keep flying and having fun.

You obviously didnt look at the link provided by Maciek. His plane is already build. Are you suggesting he build a new wing with a different dihedral and different airfoil? Where I fly the wind can go from 0 kts to enough kts to tie your plane into knots in the course of a single flying day. We dont bring wings with different airfoils or try to change dihedral so we can keep flying. We simply add ballast and launch again.

Once a plane is built the only things to do to change performance without rebuilding are:Add weight(increase wing loading), move weight around (move the cg around ), change decalage and change power sources.

I don't think he wants to rebuild his plane. I think he wants to improve its ability to handel the wind. That means that at this point WINGLOADING is the key.

Vince
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Old Jan 26, 2005, 06:33 PM
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São Paulo - Brazil
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Vince & all

I totally agree whit you Vince, but on a AP Platform, you have the engine power has a limiting factor, and those engines are not powerful enough to climb whit a model full of ballast .
Is a little bit different , in slope gliders if you have too much wind, you have to much lift, so you can change lift for speed, that’s the function of ballast.
But wen you need to climb vertically, lightness is a important factor.
That’s way I prefer tiny airfoils, and clean sleek lines.

Cebola
Brazil
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Old Jan 26, 2005, 11:33 PM
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Santa Fe, Texas
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Cebola,

Lightness is helpful in verticle climbout but only relative to Power to Weight ratio. A brick will climb verticaly with enough power. Ever watch the space shuttle take off? On average thin airfoils need to be flown faster in all regimes. For AP you want slow flight and high lift. Thick flat bottomed airfoils provide this in gobbs. Yes they are draggy but that is the trade off you have to live with. Watch Sea Gulls at the beach. On a calm day they are as graceful as any Hawk or Falcon. Now go and watch them on a day when the winds are blowing 20 kts. Even with their thin wing and low profile airfoil they get blown around quite a bit and more often than not will spend the better part of the day not flying because it is tiring to fight the wind. Why do they get blown around like that?.........WING LOADING. Also if you refer to my first post you will see that I said "If you have the power to spare".

And honestly the question was not ;What should I rebuild to make my plane fly better in the wind? He asked what he could do to make the plane (as shown in the link) handle the wind better. Bottom line is Ballast. That could be done in the form of bigger batteries for better motors. Killing 1 bird with 2 stones. But you gotta add the stones.

Vince
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Old Jan 27, 2005, 08:29 AM
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São Paulo - Brazil
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Vince & All

Sorry, but is not a matter of create polemic , but discuss a different point a view.

I agree whit ballast, because I always fly Slope gliders, those full house types.
And I love than, many one whit more than 60oz, and small enough to fly at 100mph.

In case of AP, and tiny airfoils, I was reading many articles of Dr. Drella and get convinced, that tiny airfoils can fly slow or fast independent of ballast.
Logically in a very strong winds, I added some ballast, to avoid the effect Butterfly in a wind, and this extra wing load, increase the overall performance, of all control surfaces.

But I consider easy put ballast in a light model, and almost impossible make light a heavy model , or remove the natural ballast depending if the design or the conception of the model.

I strongly defend light models, and tiny airfoils, as I strongly defend ballast on the model , if the wind is strong enough.

Just because don’t fly because of strong wind is a very frustrating thing. And in Brazil, we have to much wind, to much rain or to much everything and fly in any weather is the only way to maintain your models in a operational mode.

In fact we have both the same point of view, and this discussion just put some light on a subject that normal builders and pilots avoid to talk about.

Cebola
Brazil
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Last edited by Cebola; Jan 27, 2005 at 08:38 AM.
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Old Jan 27, 2005, 02:37 PM
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AGREED!


Vince
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Old Jan 27, 2005, 02:46 PM
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United States, TX, Wimberley
Joined Mar 2004
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Maybe decrease the dihedral a bit... Making the wing sweep back will greatly affect your CG but will help in penetration... The ballast will help also but it will be more sluggish on the controlls... You could also throw together a little ZagnutZ flying wing and go that route...

Myron
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Old Jan 27, 2005, 07:08 PM
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Worcester, Ma, USA
Joined Feb 2001
277 Posts
I should clarify... I want to build a new plane, not modify the one I have. When I built this plane, I was just trying to make the most out of different parts that I already had. It works surprizingly well, as long as it's not too windy...
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Old Jan 27, 2005, 08:13 PM
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Canada
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Quote:
When you are at the slope and the wind gets too high for your plane to fly in do you always pull another plane out of the car. If so I would bet that the plane you pull out has a higher wing loading than the one you just put away. If you only bring one plane to the slope and the wind gets to high do you pack up and go home or add ballast and keep flying and having fun.
@ Vince in TX
Winds get never too high for me on the slope(at least not for the last 25 years), only Hurricane force winds and no Goggles would set the limit
Like the 60” sloper, the first one in the attached picture. It flys nearly perfect in 8-50 mph winds weighs only 22oz and has full house controls(6 servos), and there is not a great advantage to add Ballast(max 10 oz) to this Model (as tested)
Quote:
We dont bring wings with different airfoils or try to change dihedral so we can keep flying. We simply add ballast and launch again.
Guess you use different Models (maybe more like floaters) on the Slope.

back to topic:
For AP applications a ‘tiny’ airfoils as per Cebolas definition( I guess he means profile thickness under 9% like RG15, HN 354, HQ1.5-08 and hundreds more) is a start but the wings should have also ailerons (best full span) or even better separate Flaps.
In this way you can slow it down in light wind conditions just with deflection of ailerons /flaps.
Just using a better design with less draft will be a better solution as ballasting Models for AP. Flying slope for a long time helps to deal with high winds.
There is no perfect Model for all conditions on the market and never will be, but a good All-rounder is what’s required for AP (IMHO).
I use currently for AP a Magpie with the Aileron wings (at 25 oz) which is quite agile and can be flown in 20 mph. But there is room for improvement.




Cheers
Thomas
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Last edited by wakumann; Jan 27, 2005 at 09:32 PM.
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