gm2282

HI ivegot a sig 1/4scale cub bought it already built! no raido with a fox 78 engines???? droped my raido in it but dont know the cg range??can anyone tell me where to start from?how many inchs back from the LE .also not too sure about the fox engine!!! had a fox 25 years back . (it was a nightmare to tune) Thanks Greg !!

Lnewqban

For 1/4 scale:
http://www.sigmfg.com/BuildManuals/S...WingCubSP.html

Peter_OZ

My Feedback: (1)

I have had one for many years now. Manual states 4 3/8th" from LE of the wing.

Mine has an OS FT-160 twin fourstroke in it. 17lbs AUW.

Manual the 1/4 scale Cub can be flown with a .90 2 stroke or a .90 to 1.60 Fourstroke. I would suggest the Fox .78 to be a tad small. Small gasser of 26 cc would be a good choice too.

Good luck.

gm2282

tanks guys i balanced my cub @ 27.5 % it worked out too be 3.5 inchs the fox 78 engine did however fly it verrryyy scale like!!!! not much power would fly backwards in a 10 mile an hour wind!!not many flying days under ten where im from mid mich!! so i put a asp 180 in the front flys real fine now a bit much power now but thats what a throttel is for!!! again thanks guys greg!!!!

bikerbc

4 3/8 is the correct CG I too have had one for many yrs and that is dead centre . I have 3 1/4 scale Cubs rite now and thats where they all are .. 3.5 " is going to be tail heavy on a 1/4 scale .. Are you sure you are 1/4 scale ? A Fox 78 sounds a little small too.. What is your cord ? A 1/4 scale should be about 16 inches . Peter is bang on with everything he has said... One of my Cubs has a OS Max Gemini 160 Twin one has a OS FS120 and the other has a G26 Zenoah gasser ... By far I like the Gemini Twin best ,just for how it looks and sounds... The 120 is my daily flyer.. It is very reliable ...The G26 seems under powered but its cheap to run .

buzzard bait

Greg, for a 16 inch chord, 27.5% works out to 4 3/8 inch, not 3.5 inch. I think your plane was probably quite nose heavy, not tail heavy, at 3.5 inch. Your Fox .78 would have handled it a little better if the CG had been in the right place.

Many years ago people flew quarter scales Cubs on .60s. Not much choice back then, but they flew, very scale-like, I'm sure. In fact, Bill Northrup flew his quarter scale Gypsy Moth on a Fox .59 at the Nationals...yeah, that was WAY back.

bikerbc

Buzzard bait If your C of G is supposto be 4 3/8" and it is only 3 1/2" you would need too add weight to the nose of your aircraft to bring the balance point back ..That would make you tail heavy ... Or am I looking at this wrong ?

buzzard bait

I think you've got it backwards. If the plane balances at 3 1/2 inches and it is supposed to be 4 3/8 then the nose is too heavy. Look at it this way...if you had it balanced at 4 3/8 inch and wanted to balance it at 3 1/2 inch, what would you have to do? You'd have to add nose weight to move the CG forward.

Conversely, if it is at 3 1/2 inches and you want to move it back to 4 3/8ths, then you would have to add tail weight. Or reduce the weight in the nose. Does that make sense?

Jim

BMatthews

Jim, you're right.

bikerbc

Darn I think your right . No wonder my Vanessa Rig dosent work right and my planes crash alla time ..