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Old Oct 13, 2011, 02:25 PM
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Joined Aug 2011
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Forward-swept wing + V tail Design



Hi

this is my first design

I just draw Forward-swept wing + V tail

what are the charicteristics of Forward-swept wing and v tail respectivly?


then what would be it's airodynamic charicteristic?
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Old Oct 13, 2011, 02:50 PM
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build test glide. may need canard's. I would just do necell on top
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Old Oct 13, 2011, 04:03 PM
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Linköping, Sweden
Joined Nov 2003
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Very cool looking bird!

Hi
It looks fast and exotic!

A few tricks of the trade regarding your configuration:
- Forward swept wing is good for preventing tip stall
- Stalling a section of the wing far back gives a nose up pitching moment, agrevating the stall (not so good)
- Strakes are good for maintaining a high energi flow over the root of a "strait" wing at high angles of attack (high alfa)
- Strakes moves the center of pressure forward (nose up moment) since they do not stall when the main wing does, this agrevates the stall further
- Strakes sometimes gives a high energy flow over the fins (or V-tail in your case) increasing efficiency of said fins

Shaping of this type of configuration for full scale aircraft takes hundreds of hours of wind tunnel tests.
However, this is done since pilots won't climb into an untested aircraft...

Aaaand, modellers don't have to bother with that apprehension so we just build and test fly!!!

If I where you I'd do a small balsa/depron free flyer to establish a safe CoG and size of tail planes. Go for it!!!

Best reagrds
Patrik
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Old Oct 14, 2011, 02:32 AM
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St.Catharines, Ontario
Joined Jan 2009
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mix

very cool design. I might suggest that you check out a few threads on this forum. there are two FSW projects underway and I think it would be wise to jump on board those threads to give you ideas for yours. I'm sure Steve and others will jump on board yoru tread to help you out.

one way to prevent nose up on deep stall is to add negative incidence to the root foil. another way, is to do what the full size planes do and use an airfoil that looks a lot like a thinner version of that used on the A-10. it's got a very definite undercamber to the rear of the foil, which brings the lift further back, thereby giving a pitch down in high alpha, deep stall conditions.

Rich
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Old Oct 14, 2011, 02:42 AM
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Quote:
Originally Posted by LuvEvolution7 View Post
mix

very cool design. I might suggest that you check out a few threads on this forum. there are two FSW projects underway and I think it would be wise to jump on board those threads to give you ideas for yours. I'm sure Steve and others will jump on board yoru tread to help you out.

one way to prevent nose up on deep stall is to add negative incidence to the root foil. another way, is to do what the full size planes do and use an airfoil that looks a lot like a thinner version of that used on the A-10. it's got a very definite undercamber to the rear of the foil, which brings the lift further back, thereby giving a pitch down in high alpha, deep stall conditions.

Rich
Hi again~ luv

Yeah now a days I just fell in love with sketch up thing and making some blueprints.

Nice to inform me I'll check and get some basic knowledge on it thx again
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Old Oct 14, 2011, 04:23 AM
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Last edited by mixjsj; Oct 14, 2011 at 04:33 AM.
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Old Oct 14, 2011, 04:25 AM
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Joined Aug 2011
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Quote:
Originally Posted by century_series View Post
Hi
It looks fast and exotic!

A few tricks of the trade regarding your configuration:
- Forward swept wing is good for preventing tip stall
- Stalling a section of the wing far back gives a nose up pitching moment, agrevating the stall (not so good)
- Strakes are good for maintaining a high energi flow over the root of a "strait" wing at high angles of attack (high alfa)
- Strakes moves the center of pressure forward (nose up moment) since they do not stall when the main wing does, this agrevates the stall further
- Strakes sometimes gives a high energy flow over the fins (or V-tail in your case) increasing efficiency of said fins

Shaping of this type of configuration for full scale aircraft takes hundreds of hours of wind tunnel tests.
However, this is done since pilots won't climb into an untested aircraft...

Aaaand, modellers don't have to bother with that apprehension so we just build and test fly!!!

If I where you I'd do a small balsa/depron free flyer to establish a safe CoG and size of tail planes. Go for it!!!

Best reagrds
Patrik
I know. so I'm just thinking buying one autodesk program. I can have Wind tunnell simulator with it. thnx
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Old Oct 14, 2011, 04:32 AM
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Quote:
Originally Posted by LuvEvolution7 View Post
mix

very cool design. I might suggest that you check out a few threads on this forum. there are two FSW projects underway and I think it would be wise to jump on board those threads to give you ideas for yours. I'm sure Steve and others will jump on board yoru tread to help you out.

one way to prevent nose up on deep stall is to add negative incidence to the root foil. another way, is to do what the full size planes do and use an airfoil that looks a lot like a thinner version of that used on the A-10. it's got a very definite undercamber to the rear of the foil, which brings the lift further back, thereby giving a pitch down in high alpha, deep stall conditions.

Rich
The problems are

1. wash in or Out?
2. How can make lift more backward?

are them right?

I think wash in is more proper in FSW. caus you know that in high Angle of attack(Aa), the wing tip should stall first in wing of this shape. then think about every section of wing in High Aa. then in washin case wing tip has more big Aa then other place. so, stall first and proper.
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Old Oct 14, 2011, 06:11 AM
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build fly
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Old Oct 14, 2011, 07:07 AM
Aka: Tom Jenkins
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United States, FL, West Palm Beach
Joined Aug 2008
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Mix, got your text. My design doesn't use any forward canard wings, no fuse lex.
After experimenting with a sfw layout I finally found the angle it needed to fly as a wing, not a whole plane. I added the fuse to it all later. I use a full elevon control surface now, my first design had separate Ali and ele, my second design used the elevon mix in the radio. I happen to balance at the hinge line at the tips in my designs now because of the swept forward angle. Canards and Lex's will throw another wrench into your CG so beware. I recommend building a chuck glider(small test airframe) to test your design and finalize the CG location then proceed to the actual design and build.
http://www.twitt.org/Cornelius02.gif my inspiration years ago
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Old Oct 14, 2011, 09:42 AM
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This is front view it has also anhedral

I just got concept.

First, this one should be fast:
This is my theme of this plane. it has anhedral wing. Also, the V tail wing isn't troubled by small turbulence made by main wings and which is maximized in high velocity. (I delibratly saperated main wing and tail in front view.)

Second, wing should be very strong especially twisting:
in FSW wing twisting is an major problem in design. mabe I should use carbon matterials for wing rigidity.

Third I should make foam test for CG. as always does.
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Old Oct 14, 2011, 09:54 AM
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and just look at it this show quite obviously its washin
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Old Oct 14, 2011, 01:49 PM
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Denmark
Joined Sep 2005
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I like your design, look very cool. I did a FSW last year and I used a small amount of wash in, seems to work with symmetrical naca airfoils. See http://www.rcgroups.com/forums/showthread.php?t=1202354

By the way is there any chance you will share your sketch up file, I am trying to learn to use it, maybe it can will help me if I can se how you done it.
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Old Oct 14, 2011, 02:31 PM
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wow thst's cool man! did you cut foam with yourself?

well done!~

OK this is my sketch up file and It's just sketchup NO detail



save with another name!

http://blogfile.paran.com/BLOG_10164...;%20Soften.skp
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Old Oct 14, 2011, 07:05 PM
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St.Catharines, Ontario
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deffinitely use carbon spars to alleviate twisting of the wings.

deffinitely use wash in at the root.

deffinitely keep the tip at zero degrees as per the thrust line of the plane, or close to it.

the whole idea of an FSW is that the tip does not stall and that the root remains flying as long as possible. when the root does stall, the tip should still remain flying becuse of its forward position and the way that lift travels down the wing towards the root.

LEX's are a good addition, since they will energize the flow over the root. however, they can make the plane very pitch sensitive. you may need a close coupled canard if you go with LEX's. as suggested, make chuck gliders with and with out the LEX's and see what works best. if the LEX's work best but you find it very pitchy, add canards and see if they elliminate the pitchy behaviour. if you look at the SU above and others such as the X-29, etc, they all have canards to counteract the LEX's. I personally think you should use the LEX's, but figure out how to make them work with the airframe, instead of against you while maneuvering the plane.

Rich
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