Flight trim question

I'm wondering more about the flight characteristics. Does it jump up too? Does it need lots of roll out or does it lift of pretty quickly? Is it hard to land? Do you have to land fast? Is it easy to hover?(joke) With the wing cord of that plane I have no idea where to balance it. In my experience, tail heavy is twitchy on the up and down. mk

On Tue, 19 Jun 2007 17:28:15 -0500, "MJKolodziej" wrote in :

I'd guess tail heavy, too.

Some suggestions here for trimming planes:

When does it nose under? If you go to full throttle and it noses under, it may need the engine adjusted so the thrust line is higher. You would also know that this was the case if the nose comes up and the plane floats up a bit when you bring the engine to idle.

No..I think the plane is balanced correctly. It is the second one I have built...this one will just be chugging along nicely and then starts to dive...full up gets it back..but it just happens sometimes..usually, I think when it gets up some speed. Frank

(top posting fixed)

That doesn't sound like balance, or trim either. It sounds like something is loose in your airframe or control setup. I suspect that either your wing is not mounted solidly and can change its attitude with respect to the airframe when it's pushed hard enough, or the tail does, or something in your elevator linkage will flex when it's pushed hard enough. Any of these would cause a sudden excursion in one direction only.

Frank,

Since you provided the "speed" clue, take a hard look for horizonal stab flutter. The Bee type of planes have a large flat flimsy stab and at a certain speed they will flutter. I have a 40 size Bee copy called a Lazy Cub and it will do the flutter dance if it gets too fast.

If the model was suddenly looping, I would suspect not enough rubber bands. Tucking under is a problem with some forms of flying wings. I remember one in particular that had the engine amidship that was notorious for tucking under - can't remember the name, but I remember the model.

If the model is a low wing, with the wing being held on with rubber bands...

My first "multi" digital proportional rig was a Micro Avionics XL-IC four channel set. It was on 27.195 MHz. Every time I flew my Senior Falcon over the power lines at the old Seabrook field in NJ, the radio would give me full down elevator. It never crashed my model, but it came very, very close a few times. Yes, I'm sure it was the radio causing the problem. It only happened when I flew over the power lines in that particular spot. Weird.

Ed Cregger

If the incidence? of the horizontal stabilizer is wrong, and the stabilizer has a "flying" airfoil, it may be going in and out of the flying mode. (I think flutter is more likely, or some sort of problem with the elevator control servo or linkage. If you have plenty of travel, consider reducing it.

There was a real airplane, made by Cessna > > No..I think the plane is balanced correctly. It is the second one I

has it been crashed or subjected to any possible breakage of wing? sounds like wing flexing with air pressure. Or push rod flexing,etc

Bruce

"MJKolodziej" wrote

Hey, I have torque rolled my lazy bee, quite well, thank you.

What, you can't do that with yours? Humm, I'm a better pilot than I thought, I guess! ;-)

I use two standard rubber bands knotted together, and put three of these duo's on each side, so that is 12 rubber bands in all. If you use that many, OK, there is another problem. Any less would be risky.

Well, I'd take out(free flight style) and do some test glides, engine off, controls in your normal cruise mode trim position, and ideally somewhere with tall grass. Put it in flight trim and hand launch it nose-level, at flying speed into a glide. It should glide down to a gentle landing. If it doesn't dive but goes into a quick, short period stall, you've got the cg too far forward, and you're balancing that out with excessive nose up trim. If it begins to nose over, and assuming your CG is close to correct, you need more nose-up trim and/or move the CG back. To figure out which, throw it a bit nose-down, at a little above its trim flying speed, ideally it should bouyantly glide to a slight nose-up position, and to a gentle stall. If it dives even harder for the ground, you definitely need more incidence. If the model seems to do a little better, and you can see the trim at the higher speed is trying to hold the nose up, try moving your CG back a little. I'm betting it will dive. Those Bees seem like big sport free flight models, and I wouldn't be surprised if they even had cambered airfoiled tail surfaces. That's my basic glide test trim technique Uncle Pauly

"Paul Ryan" wrote

Nope. 1/8" flat stick construction.