Warped Elevator on Eagle 2

Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

Yep. It will cause somewhat of a roll.

Anybody have any ideas

If you have an iron or gun you can try heating the covering on the opposite side of the warp to shrink the covering (Be careful you don't burn through the covering - Monokote can take a good amount of heat). Depending on the amount of warp, this frequently will take it out.

If I do have to replace it, any ideas on how

Unless these were nylon PINNED hinges you will need to remove the elevator. The hinges NORMALLY provided are CA hinges. They need to be installed with THIN CA.

To get the elevator off cut the hinges. Make new hinge slots next to the original ones. DO NOT USE THE ORIGINAL SLOTS. The thin CA needs to penetrate the wood to provide the holding power.

The slots can easily be made by the CAREFUL use of a #11 blade. Put a T pin in the center of each hinge and insert the hinges in the horizontal stab, then in the elevator. (The pins make sure that 1/2 of the hinge is in each side) Then remove the pins and push the elevator against the horizontal stab. Flex the elevator to full deflection and put 3 or 4 DROPS of THIN CA on each hinge. Flex the elevator the other way and do the same thing on the other side. After the CA has completely dried (about 10 - 15 minutes) flex the elevator several times in each direction to make sure everything is working properly. Now you can reconnect your control horn and linkage.

Any CA spills on the covering can be cleaned with acetone and a rag.

You'll want to check to see if the elevator is actually warped or if you got the hinges in wrong.

If the hinges are in wrong then making the top surface of the right side of the elevator level should also level the top surface of the left side, and the elevator will not match up with the horizontal stabilizer right at the hinge line. If this is the case you have to cut it up and try again.

If the elevator is warped you should be able to see the twist in it, either by eye or by holding something flat, such as the edge of a piece of 2x4 against it. If it's warped then trying to fix it by re-shrinking is a good idea. If that doesn't work then you should make a new elevator, or see if you can get a replacement piece from Goldberg.

In either case if it's not too bad then you may be able to start flying the plane. You may see odd trim problems, but they may not be bad enough to render the plane unflyable. I suggest you check with your instructor to see what he thinks.

I doubt it will have much impact on the way the plane flies unless it is severely twisted. Granted, you should strive to get things as straight as possible, but in reality there are always little things not quite right. I would fly it first and see how it goes. No need tearing it apart if the end result does not change. You can always do it later if you feel it needs to be done.

John VB

You really need somebody with experience to look at the elevator and tell you if it is too twisted to fly right. A little bit is OK, a lot is too much.

If you don't live near other model builders maybe you could post a photo.

Hi Kev, If you are new to flying building don't start by forming bad habits. A little bit off is *not* OK. If you can see it you can bet that the bird will feel it and react accordingly. As you practice and improve your piloting skills you will discover that those seemingly small misalignments will come back to haunt you. Straight vertical and horizontal lines will be impossible, loops will fall off or require significant rudder corrections, etc.,etc. You will never know whether it's you or the aircraft. Your problem is not huge. Try to remove the warp. If that doesn't work build a new elevator. Check all alignments and correct those that are off. You will become a better pilot if you learn to take care of the details. Don't buy the "..that's close enough" philosophy. Strive for perfection. You may never quite achieve it but you will gain immeasurably from the attempt. That's my story and I'm stickin' to it! :-))

Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

Pleas note the last statement.

I used epoxy to glue the hinges on.

So far, EVERYONE has missed one VERY IMPORTANT thing.....

THE HINGES WERE INSTALLED WITH EPOXY !!!

The last I knew, CA hinges came with the Eagle trainers.

If the hinges are not replaced AND installed properly with thin CA, there is an excellent probability of one (or more ) of the hinges failing in flight.

All,

Thanks for the great advice! I was able to get the warp out by twisting the elevator and tightening the monokote. I knew that was possible with a built up structure from the truing the wing step, however, I didn't realize it would work with a solid piece of balsa. I'm sure there will be some other things not perfect, but I at least was able to take care of the one that I could see! BTW, it's an old Eagle 2 kit (from the mid 80's), so the instructions said to use epoxy on the hinges. I'm looking forward to getting with an instructor soon and getting it up in the air!

Happty flying,

Kev

If you are not capable of trimming a trainer with a twist in the elevator to fly straight and level you should stop flying as you are unsafe at the flight line.

I have flown three planes with only one aileron. The first blew off cleanly in a dive induced flutter. I had exactly zero problem pulling out of the dive flying a couple of circles to line up to land and land the plane with the usual no bounce. Frankly at lower speeds the plane handled just as well with only one aileron as it handled with two. I am sure if I had tried a roll the roll rate would have been much slower then I was used to. And it might not have snap rolled if I had tried. This was a very aerobatic plane.

The second was a trainer. I preflighted it and everything seemed ok after I spent an hour or so fixing problems. On the second flight one aileron blew off two hinges and was sticking up at a real ugly angle. It was attached by the inboard hinge and the torsion rod from the servo. Every time I did an aileron input the angle changed dramatically from sticking up to sticking down. I took control from the student got off the throttle, did a 360 turn to get lined up to land and landed. No handling problems at all. We reglued the control surface and took it back up in half an hour.

The third was a home brew. I was lazy and simply saw no reason at all to spend the time and effort of building an aileron on both wings for this particular plane. So I put a somewhat over sized aileron on one wing only. Saved installing two servos and a hours time. The plane was not intended to be aerobatic. I flew that plane hundreds of times. It made no difference at all if the turn was left or right. It turned just fine in both directions. It would loop inside or outside in a nice straight line. It would fly level hands off just fine. I would not hesitate to build another like it. It was not intended to roll as the one aileron was only about 24" long and inboard on a 10 foot wing span. Still it did a few rolls which were so slow you could eat lunch before they were over. Took full rudder during the roll and even then the nose would drop it was so slow.

Sure it is ideal to have control surfaces straight. It is also ideal to carefully balance everything not just set the CG. If you are going to fly pattern you better have it straight and balanced or you will have to use the rudder more then desireable. Although the pattern guys I know tell me they use the rudder as much or more then any other control. I know I could not fly very well without it. It is also important to make sure the angle of incidence for the wing is perfect for the particular plane, the off set in the engine is correct in both lateral and vertical directions. And on and on. And not one rc guy in ten even knows how to check a plane and figure out if he has too much or too little down thrust in his engine I suspect. Much less correct more subtle problems. So the vast majority of planes simply fly just fine with lots of stuff close but not perfect.

Not long ago there was a whole series on how to tune a plane in one of the mags. The AMA rag maybe? The "expert" gave so much bad advice it is a wonder anyone can fly anything if he is an example of understanding. The "expert" did not even know which way a neutral plane wants to turn on takeoff. Much less how to correct the problem. And that is only the start of his errors.

Kev has a Eagle trainer. If he puts the usual FP40 on it the thing will loop and roll. Both will be ugly even in the hands of a pattern flyer. It will even do a rolling circle. Really ugly even in the hands of a pattern flyer. Telling him things need to be perfect or the plane will not fly right is a misservice to this new fellow who is trying hard. His plane will fly at slow speeds and float nicely regardless of a minor twist in a control surface. He is hundreds of flights from being able to tell the difference and on that plane likely would never be able to tell the difference anyhow. On an eagle you could put the wing on backwards and probably still fly the thing. That is why it is called a trainer.

All you do with advice like this is once more show you do not know diddly about one more thing as usual.

In my opinion "bm" that was a cheap shot you took at Ed Forsythe. Apparently Ed looks at building a bit differently from the way you look at it. And he never said the OP wouldn't be able to fly the plane with the "mistakes" uncorrected. His message was simple; try to get it right and you will develop better building skills and be a better pilot. Mistakes aren't always fatal, but we really ought to try to learn from them.

Sounds like you don't value Ed's opinion on a lot of issues. Why not simply avoid the daggers and simply make your point. In this case, I guess its that you can fly a lot of mistakes if you are a good pilot. I would guess that would be right, but it doesn't mean you shouldn't try to build it to spec.

Harlan

Did you miss the post about Kev fixing the Elev.? I think this was a learning thread, stuff he (or I ) can take or leave and you gave good information. You shouldn't be threatened by opposing views. Ahhh, it's all part of USENET. :) mk