Wing/Tail/Fin ratio (Full Version)

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DIPSY -> Wing/Tail/Fin ratio (3/18/2003 5:40:05 PM)

Hi guy's
I'm working on my first scratch built prop jet (Blackburn Buccaneer) and I wanted to ask, what is a good rule of thumb for the ratio between the wing area and tail area?

Dave



DICKEYBIRD -> Wing/Tail/Fin ratio (3/18/2003 6:11:23 PM)

Go to http://www.aalmps.com/freestuff.htm and click on "Tail Volume" Al shows a fairly simple "rule of thumb" formula for computing the TVC (Tail Volume Coefficient) I have used it in my last 3 designs with good results. After computing the TVC, that number can then be put into another of Al's formulas to calculate the CG location. This works well also.

Al's Lidberg's site is mostly about rubber powered models but the same numbers apply to R/C models in most cases. Works for me! :D

Good Luck!



Daniel Nelson -> Wing/Tail/Fin ratio (3/19/2003 4:04:49 AM)

You might consider making the tail surfaces a little bigger then recommended. It will give you more control and stability, and the jet engine should provide more then enough thrust to overcome the extra drag and weight.
-Dan

PS: Oops, I misread 'prop jet'.



SoarNeck -> Wing/Tail/Fin ratio (3/21/2003 3:05:09 AM)

If you want a spreadsheet to do the math for you, feel free to check out the following page: http://www.soarcalgary.com/Extras/Articles/Sailplane%20Design%20Spreadsheet/index_html

I'm not quite done with the user's manual yet, but it won't take long.



DIPSY -> Wing/Tail/Fin ratio (3/21/2003 3:43:12 AM)

Thanks
Calculas really makes my brain ache.
I may have partially solved the problem. The plan at the moment is roughly the same size as another propjet (Hawker Hunter)I built from a kit, 4 feet long(didn't survive an encounter with a goal post sadly). I'm thinking of using the same sections and vertical/horizontal stab sizes.
I've always liked models that are a little 'hot' on approach.

Dave



scalebldr -> ratios (3/21/2003 4:47:19 AM)

i posted this once today but here goes.stab area is 20 to 25 % of wing area,this includes elevator.elevater is 20 to 25 % of the stab.fin and rudder is 25 - 50 % of the stab area depending on how high the fuse is at fin,wide fuse side = smaller rudder,narro fuse side =larger fin including rudder.rudder is 30-50 % of the total area of fin/rudder.hope this helps.fairly simple.



DIPSY -> Wing/Tail/Fin ratio (3/22/2003 12:52:04 AM)

Thanks
That was the kind of answer I was looking for, now whats a rudder?!!!LOL Just kidding.



SoarNeck -> Wing/Tail/Fin ratio (3/22/2003 2:50:33 AM)

The only problem is that there's no allowance for tail length. Short tail = large surfaces



susquach -> Wing/Tail/Fin ratio (3/22/2003 9:43:10 AM)

dipsy,

scalebldrs numbers are good. Soreneck brings up a good point. For a pattern type plane, figure a fuse length of about 70% of span. About 21% of the fuse length to be from the leading edge of the wing to the back edge of the prop. About 55% of the fuse length to be from trailing edge of the wing to hinge line of the stab. Or more precisly, measure the nose moment from 25% MAC forward to the back of the prop, and tail moment from 25% MAC of the wing aft to 25% MAC of the entire horizontal stab. As scalebldr said, it's a simple approach, but will yield a nice flying plane.



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