W.S. to tail feathers ratio
01-13-2005, 07:22 PM
#1
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W.S. to tail feathers ratio
Good day.
I've done a search and can't find what I want. I've read many a thread in here and truly am not not worthy of posting. But, is there a ratio of wing span to tail feathers and distance between the 2?
Recently I put a Stick 40 wing (58") on a duraplane (calls for 44"). The last time I tried to shorten the tail feather distance it wasn't real great. (made great flat spins) It was really unstable.
From the rear of the main w.s. to the leading edge of the tail feathers is about 15".
THIS time the plane is rock solid. Now, this is the same main wing as before. I don't remember the distance of the last plane.
There are the delta wings which I can't believe can fly. But always experimenting with left over plane parts.
Any help on understanding this is appreciated.
Thanks
Spanky
I've done a search and can't find what I want. I've read many a thread in here and truly am not not worthy of posting. But, is there a ratio of wing span to tail feathers and distance between the 2?
Recently I put a Stick 40 wing (58") on a duraplane (calls for 44"). The last time I tried to shorten the tail feather distance it wasn't real great. (made great flat spins) It was really unstable.
From the rear of the main w.s. to the leading edge of the tail feathers is about 15".
THIS time the plane is rock solid. Now, this is the same main wing as before. I don't remember the distance of the last plane.
There are the delta wings which I can't believe can fly. But always experimenting with left over plane parts.
Any help on understanding this is appreciated.
Thanks
Spanky
01-13-2005, 08:49 PM
#2
RE: W.S. to tail feathers ratio
this can be very confusing -as there really is no "fixed" ratio.
There are formulas for this - someone is sure to post em --
here is some SWAG info
The lighter the model wing loading - the less critical this all becomes
The larger the tail surfaces - the shorter the distance can be .
On most full scale acrobats there is around one root chord distance between the trailing edge of the wing and the leading edge of the stabilizer. (what does that mean?)
BUT on a soaring glider - there are many wing chord intervals -
Look at the 3 Views of different types of aircraft - you will see a pattern develop as to relative sizes and distances - The answer you are looking for, depends on the job the aircraft does.
Lil trainer type models are kept relatively long -to increase POSSIBLE pitch stability and control.
There are formulas for this - someone is sure to post em --
here is some SWAG info
The lighter the model wing loading - the less critical this all becomes
The larger the tail surfaces - the shorter the distance can be .
On most full scale acrobats there is around one root chord distance between the trailing edge of the wing and the leading edge of the stabilizer. (what does that mean?)
BUT on a soaring glider - there are many wing chord intervals -
Look at the 3 Views of different types of aircraft - you will see a pattern develop as to relative sizes and distances - The answer you are looking for, depends on the job the aircraft does.
Lil trainer type models are kept relatively long -to increase POSSIBLE pitch stability and control.
01-14-2005, 12:53 PM
#3
My Feedback: (11)
RE: W.S. to tail feathers ratio
For stable R/C models, you can use some very basic "rules of thumb". Let's assume a constant-chord wing. You then make the fuselage about 5 or 6 wing chords long. The nose is one chord-length from wing leading edge to propeller. The leading edge of the stabilizer is 3-4 chord-lengths behind the trailing edge of the wing.
Ailerons would total 15%-30% of the total wing area (depends upon the type of aircraft).
Horizontal stabilzer/elevator area is 20%-25% of the wing area, and the elevator is 15%-60% of the total horizontal area (this depends upon the model's intended purpose).
The Vertical fin/rudder is 40%-60% of the total horizontal area, and the rudder is 15%-60% of the total vertical surface.
Balance the model at 25% of the wing's chord and go from there.
These parameters won't give you a model that's particularly good at anything, but you'll have one that WILL fly. Many R/C models from the late 60's to early 70's used parameters such as these. By varying the shape of the fuselage and airfoil, you got a wide variety of "original" designs.
Some of the most prolific designers have used such formulas. The result was a wide variety of different-looking models that flew well, but didn't have anything particularly-distinctive about them. When the bulk of models were kit-built or plans-built, a different-looking model was the main goal. That's just like the way some of the most prolific mystery writers (or writers in any other genre) work. They have a basic set of parameters for the story, and just combine different elements and Voila! an new story for the mystery buff.
(edited for typos)
Ailerons would total 15%-30% of the total wing area (depends upon the type of aircraft).
Horizontal stabilzer/elevator area is 20%-25% of the wing area, and the elevator is 15%-60% of the total horizontal area (this depends upon the model's intended purpose).
The Vertical fin/rudder is 40%-60% of the total horizontal area, and the rudder is 15%-60% of the total vertical surface.
Balance the model at 25% of the wing's chord and go from there.
These parameters won't give you a model that's particularly good at anything, but you'll have one that WILL fly. Many R/C models from the late 60's to early 70's used parameters such as these. By varying the shape of the fuselage and airfoil, you got a wide variety of "original" designs.
Some of the most prolific designers have used such formulas. The result was a wide variety of different-looking models that flew well, but didn't have anything particularly-distinctive about them. When the bulk of models were kit-built or plans-built, a different-looking model was the main goal. That's just like the way some of the most prolific mystery writers (or writers in any other genre) work. They have a basic set of parameters for the story, and just combine different elements and Voila! an new story for the mystery buff.
(edited for typos)
01-14-2005, 06:31 PM
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RE: W.S. to tail feathers ratio
Thank you.
Bax, you brought up a point about the elevator % being 60%. You read the extreme fun fly and all, and they have HUGE surfaces. Could you make NO horizontal stabilizer and ALL elevator? Put a pivot just forward of the centerline to give it a castor basically. Same with the vertical stabalizer. Eliminate? make the whole thing rudder?
Spanky
Bax, you brought up a point about the elevator % being 60%. You read the extreme fun fly and all, and they have HUGE surfaces. Could you make NO horizontal stabilizer and ALL elevator? Put a pivot just forward of the centerline to give it a castor basically. Same with the vertical stabalizer. Eliminate? make the whole thing rudder?
Spanky
01-17-2005, 03:28 PM
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RE: W.S. to tail feathers ratio
I've never done any experimenting with this but I believe to a point you can use any size stabilizer you want. The smaller it gets, the more critical the CG becomes to the point where using a half tank of fuel can take the plane from being stable to being uncontrollable. That's an extreme case though.
I agree with most of what Bax said, but there are a couple things I don't agree with. First, 20% is a very safe size and more than usually necessary. 25% seems like way too much to me. I would say 15% to 20% is safe and anything smaller than that starts making the CG more critical.
The other thing is that I've never flown a plane where the CG was ahead of 30% that wasn't really nose-heavy. On all my conventional designs I start with the CG at 33% for test flights and find that it's still a little nose-heavy. I usually end up around 35%.
I agree with most of what Bax said, but there are a couple things I don't agree with. First, 20% is a very safe size and more than usually necessary. 25% seems like way too much to me. I would say 15% to 20% is safe and anything smaller than that starts making the CG more critical.
The other thing is that I've never flown a plane where the CG was ahead of 30% that wasn't really nose-heavy. On all my conventional designs I start with the CG at 33% for test flights and find that it's still a little nose-heavy. I usually end up around 35%.
01-17-2005, 05:07 PM
#6
RE: W.S. to tail feathers ratio
Done some very low wing loading CAP 232 stuff that is best for IMAC at close to 25%
this simply has improved trim drag and the light loading allows you to really cram in huge elevator inputs -
very crip snap and recover, balanced at forward CG - No good for flip flop tho--
Some of my flippity flop stuff is at 40% MAC chord and simply flies horribly- except for vectored flight - that is just fine.
this simply has improved trim drag and the light loading allows you to really cram in huge elevator inputs -
very crip snap and recover, balanced at forward CG - No good for flip flop tho--
Some of my flippity flop stuff is at 40% MAC chord and simply flies horribly- except for vectored flight - that is just fine.
