I HAVE A WING RIB THAT HAS:: A ,NEGATIVE .135 C.L... IS THIS ALOT??

Got any more details? What plane? Just one rib, or is it a "hershey bar" wing? Is it a kit, arf, scratch built, other? What exactly do you mean when you say "C.L"?

HI .SORRY IT IS A WING ..ROOT 15" TIP 8"NEGATIVE .135 C/M..HOG A-10 WING..I THINK IT IS A FX 160-14

Still confused...

What's a negative .135 CL or CM? and what do you think is wrong with it, whatever it is. Perhaps explain a bit further.

OK THIS IS ALL I KNOW..IF A SYMETRICAL AIRFOIL HAS A, .0001C/M.WHAT IS A .135 C/M OF??..THIS IS MOMENT AT 1/4CHORD POINT.I THINK IT MEANS ,THE AIRFOIL WANTS TO GO DOWN/DIVE THIS PERCENT .I NEED TO KNOW WHAT .135 IS A PERCENT OF.?? HOW MUCH MOMENT IS TRIENG TO GO DOWN ,IN LEVEL FLIGHT.. I FEEL IT WILL TAKE NEGATIVE STAB. DECALAGE TO OFF SET THIS NEG. WING C/M.. WOW!!THESE ARE TOYS .RIGHT?? THANKS,, RD

Yes, they're toys.....That act like the real thing.

O.k. - I think I understand(sorta), Not sure off-hand on the exact math, but I beleive you're on the right track. The full-size A-10 has noticeable negative incidence in the horizontal stab(maybe due to the huge, heavy cannon in the front?) Is this a kit?

BTW - YOU DON'T HAVE TO YELL, I can see just fine, if not hear too well anymore....

OH! You mean the pitching moment of the wing. Yes, your model WILL require some negative incidence in the stab compared to the wing. There's no need to sweat bullets over it though. Make the tail angle about 3 degrees negative compared to the wing and then trim the elevator as needed to suit your final CG location.

There IS an explanation of how to use the pitching moment value to size the horizontal tail but I'm a bit rusty on that part. In any event you're working with a kit I gather so it's a moot point.

Your airfoil number isn't in Profili2's database. I think you may have the number mixed up...

And cwrr5 is trying to say that in internet newsgroup language typing in caps is like yelling and is considered impolite.

Good luck with your A10.

Exactly right Bmatthews, not trying to ruffle feathers or anything, it's all in good fun

Rapptor - Check out this thread, and the ones it leads you to. Not sure if this is the right direction, but it's pretty intresting...
http://www.rcuniverse.com/forum/Tail...2332174/tm.htm

Still searching for the exact theory(oh boy!), however my resources are kinda limited over here in the sandbox. Stay tuned...

Also check this site out - everything you need to know about specific airfoils. Didn't see an FX 160-14 tho....
http://www.aae.uiuc.edu/m-selig/ads/coord_database.html

One more for you:
http://web.usna.navy.mil/~dfr/wtlab3.pdf

Rapptor-I think what you were asking is contained on pg 4, I'm just an amatuer, but if I understand it correctly, that one variable doesn't correlate directly with the horizontal stab angle of attack or incidence, but has to do more with the lift generating properties of the airfoil section. When taken as a whole, the wing will have a tendency to pivot further back as opposed to a symmetrical airfoil when the angle of attack increases, and the wing on an a-10 is highly cambered, so would have more of a tendency to pitch downward due to the somewhat "droopy" trailing edge and negative(?) CM... Not sure if any of that made sense????

Somebody that knows the theory - Please help!!!!!!! [] LOL - I'm outa my league here!

ok..thanks for all the info.and help.. i did not mean to yell.i allways do caps,they look cool..i forgot and, did not think to add in the lift of the airfoil. im using 6 deg.neg incidence on stab. this design is flying in a wegde or a bind.. not to effective..tons of drag!!..i have been told that the a-10 is very pitch sensative..i can see how...the cg and C/L are a mile apart..