Unequal elevator halves
 

Hi,

while I was setting up the throws on my GP Reactor 46 today I found that, with the LE of the two elevator halves inline with the stab's LE, the TE of the two was not level. When looking from behind, one TE is definitely lower than the other. This is not an alignment problem because they halves are otherwise fine. Looks like the two halves are non symmetrical. I had noticed a similar problem with the elevator halves on my Reactor Bipe earlier. I summarize that GP has a elevator half line that is supposed to make one type of half that is to be used for both left & right sides. But they are making the halves nonsymmetrical about the chord line.So when the flip it over, the TE of the two halves don't end up level. Anyone else have the same observation and how to correct this?

Ameyamhttp://www.rcuniverse.com/forum/atta...mentid=1963607

Yup, your geometry is not identical for both halves.

You need to make sure that your horn positions are the same, and that your linkages have identical lengths.

This includes the arms you have installed on the elevators with the eyelets. Minor differences cause somewhat large changes.

You also need to check the position of both elevators at their extreme travels as well.

Hopefully you put an identical minimum gap in the hinge so the elevators are free to move to the same extreme position.
If so adjust your linkages so that the two elevators line up at full up and full down.

Be careful with warping. Any minor warping of the surface may cause you to misadjust the mid and end points.

Try to AVOID using radio trims and mixing to try to fix this, the results are always sub optimal.

Instead do everything mechanically.... but first start with the servo arms get exactly the same angles and lengths.

Hi Opjose,

all the point check out- everything thing is same except one- the linkage lengths are not identical because the model is mot wide enough for two servos back to back. In my case one servo is infront t of the other. However that doesn't matter here- I took the snap without the battery. The elevators are located with the LE inline with the stab.

To me it looks like a manufacturing issue but I don't have time to correct it coz the event I am readying the model for is next weekend.Is there some way to minimise the problem? My bipe flew beautifully inspite of it

Ameyam

That is exactly what it is and it's not uncommon for the elevator halves to display the issue you have on your model. The "counterweight" area on usually just one side does not line up level with the stab when the elvators are in neutral.

There are various ways to do the line up but I use a couple of carbon fiber rods taped to the top surface of the elevator and pointing aft so they meet about 12 inches or so behind the rudder. That way you can match the neutrals and end points and if your radio is capable, you can match the deflections through out the travel range.

I appears to me that because of the built up construction of the elevators and a lack of care while covering that the elevators may have a slight warp. This is easily taken out by holding an opposite twist and re-shrinking the covering.

I'm not sure what you are saying.

Do you mean that the two servos driving the elevators are NOT "side by side".

Normally servos are never placed one in front of the other when servicing two elevator halves.


Servos that sit just in front of the leading edge of the elevator are "side by side" for all intents and purposes and if you've set things up SHOULD have identical linkage lengths.

If not you did not reverse one of the servos via your TX, a reversed servo, or a servo reverse as you should have.

This is NOT a "manufacturing issue" it is a "user error".

Zeeb is refering to differences in the counterweights, etc... which in part can be due to warping, or placing one elevator higher than the other when hinging. That does not seem to be the case here.

In your case the trailing edge of the elevators ( assuming that the elevators are properly hinged and NOT warped ) must be identical at different stick postions. You have to fix the geometry to make this so.

If you do not, you may not notice the problem until you perform a tight loop or other manouver. The difference will cause the plane to favor one side over the other.

Normally I would agree but look closely at the photo.

The elevators are not warped from the LE to the TE.

Rather the 4-40 screw "horns" he is using are at different positions relative to each other.

The right one is slightly forward of the left. --- Geometry is wrong.

Jose, what he is saying is that the rear of the fuse is fairly narrow so there is not enough room to mount the servos in the same place on both sides of the fuse. One servo has been moved forward of the other. This was very common when we started putting servos back in the tail of our pattern airplanes and will not lead to an issue of UN-equal travel, the geometry is the same it's just that one servo is farther away from the hinge line then the other.

Check the elevators for warpage, i'm sure you will find it.

Those look like nylon control horns to me. Yes they do appear to be in different locations but that is because the elevator halves are not trimmed to match at the root. He has them matching at the tip where the counterbalance matches up with the stab LE. The elevators have a twist to them. He should match the halves at the root then twist the elevator by hand and re-shrink the covering and keep repeating that process until everything matches.

Yup you're right. Having one pushrod longer than the other is not problematic... as long as all other geometry is the same.

If you've followed Ameyam's other posts, issues and errors though, I'll bet this is a geometry problem.

In the photo one surface merely appears to be higher than the other and the angle of the 4-40 horns he is using does not appear to be equal.

It could be that is an illusion, but I'll put my money on a "user error".

Yup you're right.

You can get the full screen image and you can clearly see that they are nylon horns.

Yup, I see it now too. The larger image makes it plain. There is indeed a LOT of warp to the elevator itself, and he did NOT attempt to match the trailing edges at the root first as he should have.

Pretty sure it is an illusion. I don't get where you see 4-40 horns? I see nylon horns with 4-40 push rods, clevis. Rudder is a ball link on a nylon horn ( Big No No ). I agree that he does not have the experience needed to set up this type of airplane perfectly and there may very well be some geometry discrepancies but I still think most of the issue here is a twist in an elevator.

Is it me or is the vertical stabilizer not square W/the horizontal?

It looks 90 degrees to me but if I were to show that picture to my wife I would never be allowed to have an airplane in the house again LOL

I have an ESM Bearcat with the right elevator warped. After unsuccessfully trying to remove the warp I decided to fly it anyway. It flies great.....doesn't seem to care.

No a War bird wouldn't really care but the airplane in question here is a 3D airplane that will be flying in high alpha where it will make a big difference.

I had one of the early GP ARF's, A G202 powered by a Webra 1.20 that was like this. After several attempts to straighten the elevators I finally gave up and let them be different. At neutral one slightly up and the other slightly down. For my type of general sport flying it didn't seem to make much difference (not a whole lot of 3Ding)...........RJ

Guys, just hold on.

Opjose, curt as it may seem, people learn over time. I wish you would pick that up

Those at plain & simple white nylon horns. I initially had ball links in with 2-56 threaded push rods but they felt a bit delicate & likely to snap. Plus my airplane needed tail weight. So I changed over to 4-40 pushrods with Dubro spring steel clevices bothsides. Everything else is setup exactly same
What I did do was adjusted the neutral to live up the LE of the stab & elevator. That's the counterbalance area you are referring. I did tryto balance the roots with the TX but that meant the counterbalances were out & I felt this will add a roll to the tail. I wanted to confirm through this thread that the same was acceptable
Basically the halves are warped. This as an ARF with airfoiled elevator, not just one with rounded tips. So not sure how much the warp will come out with tightening coveringg Will give it a try though
There is not much I can do with the servo position. That's how the model was designed. At the most I can try & match the deflections through TX, that's what I normally do
Ameyam

Shorten the left side linkage by turning the clevice one turn in, lengthen the right side by turning the clevice one turn out. It will be close enough....go fly the wings off of it.....


ok.. it might take two turns ...

So I shouldn't look for alignment of the counterbalances with the stab LE then?
Ameyam

Hey bud....
I have had the same issues with my planes (great planes) I think I had some of the same issues with my RIP reactor bip .60 when I was trying to line up my elevators...
The factory places the elevators on so I can't change how they were glued in....
I don't think it was that far out of whack but yeah....mine was like that as well....
It really f's up a guy, when you are as particular as ME..... irritating to say the least..

I don't think it was warped....sounds like it wa built wrong...

Well, if I were to pust more pics on the setup, you would see I am pretty particular with the way I put it together. I am mostly done with Reactors for a bit of time but this was put together for the demo and once that is done, it will be my sunday flying airplane. So I took particular care and used some of my best hardware. Still ending up with this problem is a real bummer.

Moving forward. I am getting my heatgun to try and take some warp out of the elevator. Asking one side to do all the de-warping is meaningless so I am going to do a bit on both sides. Will try and get the TEs atleast in line. Lets see how it comes out

Ameyam

Looking at the picture, could it be that the elevators are handed and they have been covered wrongly at the factory and you have two left hand or two right hand elevators although covered to look like a pair.
Just a thought.

That's what I said

Ameyam

You English seems to have all the brains. I was thinking the same thing but I did not want a debate to start. I'm building a H9 PA18 Super Cub and in the instructions they tell you that the left and right ailerons are not interchangeable.

WOW...:rolleyes:

Bob

Sorry, just re read your initial post, I have seen this before though , might be worth sending a picture to the dealer see if they can get you a proper pair .

That's the only way to say it & he fitted it all into one sentense!:p ... Shift+R improves the quality of this image. Shift+A improves the quality of all images on this page.

I know my head hurts. Wouldn't be so bad but I've been dealing with a pre preg layup here at work that would be easy if others would stop complicating it. Kind of like whats happening here. At least it's Friday.

Agreed. It does not appear that anything is wrong with the parts - just the installation! Turn the clevis down on one to align the trailing edges.

Your not looking at the whole picture here. He said that the LE of the counterbalances are lining up with the LE of the stab and that leaves him with a mis alignment at the elevator root. Simply moving the clevis to line up the elevators at the root is not going to fix anything. The elevator/s have a twist. Look at the construction used, it should be a fairly easy solution to twist the elevator/s the opposite direction and re-shrink the covering to straiten them out as the twist was most likely introduced during the covering process in the first place.

exactly... I had a tough time figuring out exactly what the original poster was asking... if I may try to clarify:
when the elevator trailing edges are properly aligned and at neutral,
the elevator COUNTERBALANCES (the elevator's leading edge is where the hinges are :) ) are NOT BOTH at neutral.

(obviously if you were to align the counterbalances, then the elevator trailing edges would no longer be at neutral {one would be higher / lower as seen in the first picture})

1) one elevator is warped.
2) both elevators are warped.
3) the airplane was designed to have a LH and a RH elevator and this kit was built with two LH or two RH elevators.

I'm more than a little picky about having the exact same geometry for both elevator halves, (it's critical for aerobatics, not so much for sport / scale flying)

if it were my airplane, I'd fly it as is for the event, but as soon as I had a day of down time I'd cut the elevators off the airframe, fix them and re-hinge.
at minimum I'd do as had been mentioned: use a heat gun and get them to match as closely as possible

hope that helps!

Some tend to overthink the small things causing them to miss the important ones and that tendancy does not disappear.
:eek:

Unless the elevators are asymetrical (e.g. warbird, etc. ), a left hand elevator, recovered as a right hand elevator is for all intents and purposes a right hand elevator, particularly on a 3D plane such as yours.

First remove the elevators and try to eliminate any warping.

If you succeed re-install and align their TRAILING EDGES at center and also at both extremes.

If you cannot remove all of the warping, adjust the trailing edges at centers and extremes, then slightly re-align them so that you get the "average" position of the elevator being the same, so the effect on the plane is about equal on both halves. At best this is only an approximation.

On a 3D plane you will very much notice the warping in flight during tight loops, high alpha, and stall turns.

Days past opjose..

Seems like case 3 in Jim's list. I had a go at trying to de-warp with the heatgun got a bit of level. Like someone said, the TE is now in line but the counterbalance leading edge is out. It will make the airplane fly a bit weird but with practice tomorrow, there is nothing more I can do. I did as much as was possible during the work week working a couple of hours a evening to put it together in a week after the UCD originally meant for the event had to be discarded as it would require a full recover. Now I can practice tomm & next Saturday & hope to put up a show in the event

Ameyam

Aligning the TE is more important than getting the counter balances in place because the larger surface areas are aligned.

You could take things a bit further and now de-align the warped half to sort of average things out to a SMALL degree.

Usually getting a much warping as you can out, then aligning the trailing edges will improve things greatly.

If you want to fully fix the problem you can try the following.

- Cut the elevators back out

- Remove the covering, wet the wood, set the elevator on a perfectly level surface with a larger level weight ( I use UPS batteries) , and let it sit for a couple of weeks to dry, recover.

- Or inject small amounts of water under the existing covering with a syringe then do the above but wait even longer for the wood to dry..

- Removing warping with a heat gun is a bit iffy. Different covering reacts in different ways (e.g. some expands then contracts, some contracts only, some loosens ), and you may end up introducing more warping, though initially it may seem that you are improving matters.

Hi. I'm Ken.
The fix is rather simple, and involves use of a couple of hand tools, CA and strip of matching covering. Ok?
At the intersection of the counterbalance and stab leading edge, slice the balsa sheeting on the bottom with a razor saw , in a straight line following the leading edge straight out. This cut will normally remove about a 1/64" material from the cut zone in itself. Then push the gap closed, tape it and check with the elevators in neutral. Generally you will find that this initial cut removed enough material to bring the counterbalance into correct relationship with the stab when at neutral.
If the first cut was sufficient, then wick some thin CA into the slice and I then add a 1/2" wide strip of lightweight glass cloth over joint CA'd in place for strength. Light sanding, then a strip of matching covering and your done. If more balsa has to be removed, take a straight edge, draw a straight line the required distance from the gap, and use an emery board drawn thru the slice once or twice. Usually finishes the task nicely and keeps things straight and lined up when done this way.
Try this, it will work for you if this is your problem.

Actually guys flew a couple of flights today. Didn't have a tuned engine as the muffler kept coming off. The little aerobatics I did in that time, the airplane flew well. There's no eccentricity in the loop & I am very used to how this flies. I may replace the 91 on it with the 110. The muffler threads on the 91 have stripped & I don't have a replacement right now. Didn't try any 3d though. Don't intend to do any 3d except hover at the event
Ameyam