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Old Apr 22, 2007, 05:20 AM
I'm off my medication...
Canberra, Australia
Joined Jan 2007
393 Posts
Oreo - wing loading is mass per unit area of wing - measured in either grams/cm^2 or ounces/inch^2.

You wing looks like it will produce plenty of lift and drag - both good things for a trainer.

If you move your ailerons too far inboard they wont work properly. Where they are is good.

I'm guesing your servos are around 15-18g. Micros are typically 7-9g, so using 4 rather than two, and using all big servos has probably added something like 45g to your model. Not great, but not the end of the world by any means. I would be more concerned about your CoG. If the rudder/elevator servo mount out behind the avionics compartment it will probably make her tail heavy, which will mean you are putting more weight on the nose to balance her. There are threes ways to do this:

1. Dead weight - lead or clay
2. Find a way to move your battery further forward/bigger battery
3. Get some micro servos (cheapies will only cost you a few bucks $10AUD here - perhaps 5 or 6 USD).

Get your orientation issues and all of your control associations (if you don't already have them) sorted out on the sim before your fly.

I'm taking it your new wing has no dihedrayl so she wont rudder steer like a trainer, nor self correct anymore - just be aware.

Cheers,
oz.
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Old Apr 22, 2007, 05:33 AM
Gliding like a rock!
Oreo's Avatar
Baltimore, MD
Joined Apr 2007
241 Posts
Hmm... OK, now I get wing loading. Thanks for explaining that. I will indeed need to calculate that out just to be safe. If I need more wing surface area, can I just glue on a few extra inches to the ends of the wings making them longer?

The COG should be easy enough to manipulate just by fooling with the battery. It's by far the heaviest thing in the plane. Everything but the motor is located right under the wing & has plenty of room to be shifted some front or back to get things right.

You're right about the wing not having any dihedrayl. I was hoping it would still have some friendly manners because it's a high-wing with a low COG. Am I asking for trouble here?
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Old Apr 22, 2007, 06:09 AM
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Christchurch, New Zealand
Joined Jun 2006
6,794 Posts
If you want to fly EDFs... try getting a fast slope soarer first, they have about the same speed range, and don't have the 8-odd minute flight times. Something like a Reaper, or some other fast 60" sloper. I tend to run out of *transmitter* batteries in a single flight with slopers...
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Old Apr 22, 2007, 07:00 AM
It's a Great Day to Fly
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Melbourne Beach, Florida
Joined Jan 2002
3,864 Posts
I usually calculate wing loading in ounces per square foot of wing area. For example if the wing is 30" x 6" = 180sqin. Divide by 12"x12" = 144sqin to get 180/144=1.25sqft. if the plane weighs 20 ounces you have 20/1.25= 16 ounces per sqft. I think this is heavy. I know 11 ounces per sqft is a floater in a 40" span and because of the way aerodynamics work as you get smaller (the air stays the same density) it needs to have a lighter wing loading the smaller it is. At 16 ounces the wing loading for our hypothetical plane becomes 12.8 which is certainly better but probably not a floater.

Len
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Old Apr 22, 2007, 09:05 AM
I'm off my medication...
Canberra, Australia
Joined Jan 2007
393 Posts
Quote:
Originally Posted by Oreo
The COG should be easy enough to manipulate just by fooling with the battery. It's by far the heaviest thing in the plane. Everything but the motor is located right under the wing & has plenty of room to be shifted some front or back to get things right.
Have a play and see if you can get her balanced with current battery/engine etc. Sometimes you can't move the battery forward far enough because it would obstruct the prop

Quote:
Originally Posted by Oreo
You're right about the wing not having any dihedrayl. I was hoping it would still have some friendly manners because it's a high-wing with a low COG. Am I asking for trouble here?
She should be reasonably stable. Certainly an overwing design will help. But she will be handful until you have her trimmed. With no dihedrayl she will go exactly where her control surfaces guide her which might make the maiden... exciting. If you put in the sim time I'm not sure you will need the self correction so much.

Did the previous wing have a reinforcing rod? Have you put one in your new wing?
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Old Apr 22, 2007, 07:18 PM
R.I.P. Dimebag
Call Me Jack's Avatar
Stillwater, Minnesota
Joined Apr 2007
70 Posts
are EDFs really all that much faster than a conventional prop? had a peice of crap EDF a while ago. I was more of a toy, but i took it about and still have the moter/fan. could i ghetto strap that to the plane i have now and it be worth while?

I reallize i would need to put a shrinking tube on the end of it for more thrust
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Old Apr 22, 2007, 07:34 PM
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Christchurch, New Zealand
Joined Jun 2006
6,794 Posts
There are EDFs and EDFs... something like a GWS A10 is pretty slow, just like the real thing. But it is possible to get EDFs up around the 150kph mark without spending a fortune, and given they're pretty small, that's plenty fast... something like 5 or 6 times as fast as what you're building now, which will do around 30kph.

But then, I have a prop plane that does 150kph, and a slope glider that will do well over 200... it's not that fast, especially if you go talk to the dynamic soaring folks. Their world records... for gliders remember... are up near 490kph, and low 300s are pretty routine these days!

The real challenge with EDFs is that, other than A10s and airliners, they're small and heavy, and that means they land very fast because of the wingloading.
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Old Apr 22, 2007, 08:36 PM
Gliding like a rock!
Oreo's Avatar
Baltimore, MD
Joined Apr 2007
241 Posts
The previous wing did have reinforcing rods going from about half way out the wing down to the fuselage. The old wing NEEDED it. The new wing, not as much. Although I'm thinking of putting it on just in case. Don't want to break a wing mid flight.

She's almost completely built. I just gotta put hinges on the flaperons & that's it. Then adjust COG & do a preflight check.
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