I'm looking for a bit of general guidance on the design of 'V' tails.
Although I've used V tails over the years pretty successfully, more by luck than good judgment, I want to know more scientifically how to assess:-
1. The area (sq. ins.) say relative to the wing area.
2. What angle should they be set at for max efficiency
3. Should they be an airfoil symmetrical section (better for strength)
4. What moment relative to the C of G. or w.h.y.
5. How to measure the effective elevator component/rudder component.
and anything else which could be helpful.
The plane in mind is a 'my design' 5lb a.u.w model wing loading about 16 ozs/sq.ft. for aerial photography non-aerobatic. Motor- Mega on 12x2400 NiCads with MAT Belt drive reduction Prop. 13x7 or thereabouts.
Any help would be greatly appreciated
This site has almost all the answers to any questions anyone might have...
but generalizing, there's few absolutes in model aircraft design. Areas and moments and angles are variable to a large extent, depending on what you want from the plane, or just feel looks good.
The only "shoulds" I pay attention are the c.g. should be in the right place, there should be no warps in the surfaces, and the controls should have reasonable deflections.
My best photo plane is a collage of parts.. wing from a 2m, USPS mailing tube fuselage, arrow shaft booms, and a TLAR inverted v-tail.
A couple pages on my sites relative to this..
PJB's Seriously Aeronautical Stuff:
I checked out the Charles River site Sparky recommended and the Quick V-Tail Sizing site, specifically.
The equations provided there are aerodynamics based and easily derived vs more experience than physics based rules-of-thumb sometimes provided elsewhere.
From my perspective the key points are that you should approach the model design as you would a conventional tailed model in terms of C.G., tail volume, etc. The V-Tail areas and angles can then be calculated to give the equivalent horizontal and vertical stab moments. With that approach the total stab area, that is, the sum of the two V-tail surfaces or the sum of the horizontal and vertical conventional surfaces, should remain the same.
For instance, if you are designing a glider with a high aspect ratio wing where the horizontal and vertical stabs would each have an area of 75 sq. in. for a total of 150 sq. in., the equivalent V-Tail stab would have two 75 sq. in. surfaces at an angle of 45 degrees from the horizontal.
On the other hand, if you are designing a sport model with a lower aspect ratio wing where the horizontal would normally be 100 sq. in. and the vertical 50 sq. in., again for a total tail surface area of 150 sq. in., the equivalent V-tail area would be 150 sq. in. with two equal 75 sq. in. surfaces. This time the equavilent angle above the horizontal should be ~35 degrees.
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