Dago Bob

I flew for a few years and got out. I am now back in starting with a trainer and something happened that I can't explain.

I started on a fast low pass (for a trainer) and tried to make a sharp left turn and the model whipped up and back. It also when in S&L flight got squirrely on the elevator alone.

I thought that I might have begun to lose my elevator so I got it down quick and check it out. Everything was fine, good stiff action from the servo with no flutter or anything and the control surface was fine. I tried 2 more times and it happened always in the same maneuver.

I know it wasn't me and the equipment physically looks fine. It felt like the CG moved for a moment. I also checked internally for moving parts and everything is tight and in it's place.


Any Ideas???

visioneer_one

My Feedback: (506)

Your flat-bottomed trainer wing is generating too much lift at high speed and is pulling itself off of the fuselage. Use more rubber bands to hold it down.

Or fly slower

scalebldr

My Feedback: (7)

if you had plenty of rubber bands or it was a bolt on wing.sound like a high speed stall.check the aerodynamics forum for more info.seems like with faster speeds and increased control throws this problem is appearing quite frequently.when it first happenned to me 20 plus years ago i thought it was radio failure till i figured out what it was and was able to duplicate the reaction at will.decreased my elevator travel to eliminate the problem.

Dago Bob

Thanks for responding.

I actually have 8 rubberbands on there and it is just an OS 40LA. It shouldn't too fast for anything...haha.

It was more than just the manuver as right after, even in a medium climb, the elevator got squirrely but then a few moments later, it was fine.

???????

scalebldr

My Feedback: (7)

only 8 on my falcon 56 that weighed 5 pounds i used 5 on each side of wing parrell with fuse and 3 on each side criss crossed.i would use more rubberbands and see if problem goes away .it is not just lift pulling at the wing when you did the quick turn but some extra g forces also that probably did cause the wing to pull up off the fuse.lucky it stayed on.i have seen them seperate.remember that a 4 pound plane pulling 3 g weighs 12 pounds plus the lifting force of the wing.when i used to fly controline combat in contest there was always the 25g pull test before you could fly.your control handle,lines and airplane were connected and the after weighing the plane say 2 pounds they applied a pull scale till it read 50 pounds if the belcrank or any part failed you were done.this is with 35 powered aircraft on 60 foot lines so no telling how many g's you were pulling in that turn

Dago Bob

OK, I will try more bands. I thought it might be a radio issue. I guess I'll find out tonight.

Thanks

greenboot

My Feedback: (1)

Scalbldr,

Never say "no telling how many g's" to an engineer.

At 60 mph those planes are pulling 4 g's, at 80 mph it is 7 g's. At 100mph it's 11.

Tom

Dago Bob

Well,

I added more bands (10 total) and everything went fine. I think if I am putting that much stress on the plane that I am going to go back and epoxy some things.

BTW, anyone ever turn a rubberband wing into pin and bolt wing?

scalebldr

My Feedback: (7)

as to changing to bolt on wing yes it can be done.now as to the engineering question of g force.as well as speed don't you need to know the radius of the turn being made?if you do not have that imformation you can only generalize.i thought g's increased in relation to the radi of the turn?that is why i stated no telling how many due to the lack of all imformation.

greenboot

My Feedback: (1)

Scalebldr, You told me the lines were 60' long. That's the radius!

Tom

iflircaircraft

Dago Bob:
You probably can use at least 6 rubber bands on each side and at least two criss-crossing.....always criss-cross after installing the ones on the sides.
Another consideration is the type of rubber bands.....look for the darker ones as the lighter ones stretch more than the darker. With the weather being much hotter in Texas you'd want a tighter band anyway. We (my wife and I) found this out when her plane would go vertical after any kid of dive.
She is flying an Avistar with a 46LA.

Tom

scalebldr

My Feedback: (7)

the g question.okay you were refering to the controline model in a circle but during combat there are loops inside and outside and wingovers and what happens as the planes climb to the point where the circle is about 20 feetat the end of the 69 foot lines.the g forces are always changing but in the original post i was refering to the plane that pulled the quick turn as not being able to tell how many g's he was pulling in the turn.just a misunderstanding.you were correct with the info given obviously as we all knew back then the 25 g pull test was for safety reasons in case some one had a problem it would fail on the ground insted of in the air.thanks.