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First flight and a question

B

bajapilot

Active Member
Had the first flight of N218VC yesterday followed by a 1 hour flight today. What a great little airplane. Coming from flying rag & tube taildraggers for the last 10 years it took a little getting used to the light controls.

A few minor problems have been ironed out with idle speed, prop pitch and stall warning adjustments.

The one remaining problem I have is a very heavy left wing. I don't mean a slight drift, more like a slow roll. Ball is centered and flapperons are displace about 1/4 inch opposite when you let go of the stick.

So... I did a lot of research in the archives and Vans FAQ's to see what I should do and started by checking the all the rod ends are exactly 11/32 from the skins but that didn't help the condition. My next step will be to squeeze the trailing edge on the light wing.

Herein lies the question. Just how much effect can one expect from tweaking the trailing edges? I've heard a lot about it but no one has quantified it, does it help a little or a lot? The amount of roll that I'm getting now will take care of my turns in the pattern but that's not how I like to do them.

Thanks in advance for any help with this.

Bill
 
MY OPINION - - -

I had a heavy left as I recall. Started pinching right trailing edge of flap ( maybe 3 'panels' ), and tired it. Helped, but not enough. Did 3 more, and it was too much, and had to start pinching left side, one 'panel' at a time. I have no wedges on rudder, and ball is centered fairly well by myself. Changes with 2nd person, but stays good. It does work. Go slow and try it after each adjustment.
 
My heavy wing wasn't that bad, but I did not have much luck squeezing the trailing edge so I riveted on bendable trim tabs. Works great.
 
heavy wing

Mich48041 said:
Read this thread:
Flaperon Adjustment
In my case, adjusting the flapperon rod-end bearings was much more effective than squeezing the trailing edge (which could dent the skin).
Joe Gores
Click to expand...

Start with the adjustments at the heim joints first. I ended up mine were off on one side - 30 min later solved. Measure both sides, a half turn will make a difference. :)
 
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Heavy wing

Thanks for the hints on bringing up my heavy wing. The recheck on the rod end bearings didn't do the trick, maybe a little worst now. I'm going to try squeezing the trailing edge tomorrow morning and flight test but I'm not too optimistic because this is a very heavy wing.

I'm had other aircraft with a heavy wing which were easy to bring back with a little tweaking - washing in or out, but with the fixed geometry of the 12 I was surprised by it. I hope I can bring it back in with the "squeeze method" but I think I'm heading for a trim tab.

For those who did resort to a trim tab, did you mount it on top or bottom of the flapperon? And span wise center or closer to the tip?

Really want to get this resolved because it'll be hard to do the necessary flight testing in this condition. The airplane is a pleasure to fly in every other respect.

Bill
 
Avoid adding a trim tab

I had a heavy left wing and by making some adjustments to the rod end bearings (1/2 turn adjustments at a time) on both sides it turned out, I was able to get the wings very well balanced. I didn't find squeezing the ailerons helped very noticeably. Now at steady cruise I can take my hand off the stick and the plane doesn't move left or right all. Very stable without the need of another trim tab.

Be patient, make adjustments and avoid having to add a tab.
 
I like Dave's idea - -

wish that had been suggested when I was building. Think it would be easier and can always put it back where it was. Just write down what you change and where.
 
Heavy wing

Brent and John, I will take another look at adjusting the rod end bearings. Do you recall how much and in what direction you had to adjust them to lift the heavy wing? And on which wing?

Also, I still haven't been able to get a feel from anyone on quantifying the heavy wing. When stating they had a heavy wing does that mean that hands off the wing slowly dropped, very common on first flights. Or, like in my case, dangerously rolls if left unattended for more then a couple of seconds. I probably have a roll rate of 10 degrees/sec or better. It will immediately displace the stick several inches to the left.

Bill
 
Try turning the rod end bearings out (down) one turn on the light wing, or in (up) on the heavy wing. Like John said, write down what you do so that you can put it back if needed.
Joe Gores
 
My very heavy wing

I just finished phase I on my RV 7a. Had a very heavy left wing, full right trim still rolled left. Incidence checked great. Re rigged all control surfaces which actually made the problem worse. Several small squeezes and flights and after 5 tries got it perfect. It how's flies hands off. The squeezes where so small that you can't even see where I did it.
 
bajapilot said:
Also, I still haven't been able to get a feel from anyone on quantifying the heavy wing. When stating they had a heavy wing does that mean that hands off the wing slowly dropped, very common on first flights. Or, like in my case, dangerously rolls if left unattended for more then a couple of seconds. I probably have a roll rate of 10 degrees/sec or better. It will immediately displace the stick several inches to the left.
Click to expand...

That being the case, I strongly recommend that before you do anything else, you look at section 5.7 of THIS document and evaluate the shape of your flaperons, and correct them (based on the instructions provided) before doing anything else.

There is probably a lot of RV-12's flying that don't actually have the handling qualities the RV-12 is intended to have, because the shape of one or both flaperons is not correct (besides the strong effect it can have on roll trim).
 
Heavy wing saga

So.... I went out to the hanger this morning determined to make some progress with my heavy left wing problem. I read all the ideas, tips and images posted by fellow builders. Read the document that Scott had kindly referred me to.

I have to say I wasn't optimistic because this was a very heavy wing and I was convinced that there had to be more to it than tweaking the flapperons. I examined the skins and at first noticed that some were not flat at the trailing edge but most were close - until I checked the bottom skins! I must have been lazy and not payed proper attention to them because there were many that had a significant gap especially on the heavy wing.

I went through each panel top and bottom and squeezed them with the tool shown in the Van's document. I could get most very close but sometimes getting one side perfect meant the other side open a little mid skin. Anyway, after doing both flapperons I did a quick test flight. BIG TIME DIFFERENCE! I still have a slightly heavy left wing but no auto slow roll. Where the stick would displaced 2 inches to the left, it's now almost not noticeable from vertical. Hands off it will still start a slow left turn but takes very little pressure to hold the wing up. From the cockpit where I could easily see the flapperons displaced they now look even.

So the bottom line here is once again when things don't seem right go back to the basics and read the book. I'm amazed at how much a small adjustment can effect the wing but now optimistic that if I keep at it I'll be able to get this balanced without the aid of a trim tab. I'll post on how this turns out for those interested.

Bill
 
Bill, one tiny tip - -

I have mine set so there is a very slight left turn BY MYSELF. With a 200# passenger, it slightly turns to the right. That is where I ended up, and like it. If I take my hands off, by myself, you have to look closely to see it slightly turn, so no big deal to me.
 
Just to provide a point of reference, I probably adjusted my trailing edges 6 or 7 times to get it just right. First, I would do what Scott suggested and read up in the manual about it. Second, make small adjustments and go fly. It will take multiple iterations. Sometimes, you may go too far. I even blunted the trailing edge with a board and hammer :eek: to get it back. You can get it the way you want it but it's going to take some trial and error.

I found the best technique for bending the trailing edge is to take two long (approx. 6') 1" X 4" boards and install some hinges along the joint line. You are less likely to introduce a kink this way and you will get a more consistent bend.
 
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I used a couple of pieces of alum angle from Lowes Aircraft supply. 1.5"x1.5"x6' duct taped together. It seemed to work great was light weight and cheap. Of course, I'm not flying yet! :D

IMG_0509.JPG


Bob
 
This is an old thread, but after a tree fell on my hangar and damaged the flaperons, the flaperons were repaired. I had a pronounced roll to the left. I took it back to the shop that repaired the damage and they re-rigged the flaperons according to the plans. However, I still have a left roll issue.

RVBuilder2002 posted this: "That being the case, I strongly recommend that before you do anything else, you look at section 5.7 of THIS document and evaluate the shape of your flaperons, and correct them (based on the instructions provided) before doing anything else."

The link no longer works and his post doesn't identify "THIS" document.
Does anyone have a link or identify the document?
 
bajapilot said:
I have is a very heavy left wing.
Click to expand...
Well, ya-know, the pilot sits on the left side. That in itself is going to make the plane roll to the left. I realize that the -12 doesn't have wing tanks, but in my Lancair, I always fly with 5 more gallons in the right wing to counteract my 250 lb. weight.
 
Ya, I know except that I had a problem with left brain/right brain. It actually rolls to the right not the left and does so with gusto, about a 2-3" right deflection of the stick. Prior to the damage, the plane was in perfect trim. A recheck of the left flaperon shows bulging between rivet lines in several panels.

Question, what is the best "tool" to squeeze between the panels? The trailing edges are straight with the bulging away from the trailing edge toward the wing about 2". I want to get them as straight as possible trailing edge toward the wing before changing the rod ends.
Thanks for posting.
 
Rv3flyer-

Before getting draconian with the aft edge of the flaperons first take a look at the cantilevered portion of the wing skins that extend aft of the wing's rear spar.

Use a straight edge and make sure the upper wing skin aft of the rear spar is on the same plane as the wing skin forward of the rear spar. Do this on both wings. I was shocked that evening out the skin in that area (seemingly small amounts) completely corrected my heavy left wing. Below is a link to my site with photos.
http://www.dogaviation.com/2016/11/what-to-do-about-heavy-wing.html

Happy flying,
John
 
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Thanks for the pictures -- worth a thousand words, as they say.

I checked the upper trailing edges of the wings and they seemed to be very close to even. I think trying to change anything there to make it better than it is would be problematic. I did take 1/2 turn out on the rod ends on the left wing and then took a short test flight -- the air was rough with thermals but it did take almost all of the heaviness out of the right wing. Just gentle corrective pressure on the stick was enough to level the wings. However, it's enough out that a full bubble left rudder skid is required to fly level w/o flaperon input. I'll try taking some of the bulge out of the left flaperon skin with seaming pliars like you did in your pics. To be continued.

Thanks!
 
rv3flier said:
I did take 1/2 turn out on the rod ends on the left wing and then took a short test flight -- the air was rough with thermals but it did take almost all of the heaviness out of the right wing. Just gentle corrective pressure on the stick was enough to level the wings. However, it's enough out that a full bubble left rudder skid is required to fly level w/o flaperon input. I'll try taking some of the bulge out of the left flaperon skin with seaming pliars like you did in your pics. To be continued.
Click to expand...

You can also make opposite adjustment to rod ends on right wing - maybe 1/2 turn. Do you have the sheetmetal trim tab on your rudder?
 
Yes to the trim tab. But it takes a lot of left rudder to overcome the roll. Based upon the amount of change a half turn on the left flaperon made, I think it might be overkill to adjust the right flaperon. However, it would be much easier to give that a try than to risk over doing a squeeze to the left.
 
Just looking for some insight here, but it seems to me adjusting any of the control system linkage only determines where the neutral position of the stick will be. And, if the push rods are adjusted, it could lead to other issues such as fuel pump interference and an over center condition on the flaperon control arms. Any wing heaviness (with a hands free stick) is best addressed by measuring then correcting skin flatness on the flaperon. True?

And just an observation, another post referenced here talked about having an absolutely vertical stick. My assessment is that the stick on a properly rigged aircraft will never be vertical with respect the the other stick. This is because of the stick to bell crank connection. I's ridged and moves in an arc. This point was demonstrated to me by Mike Seager. After a landing, with no wind, that he had conducted, I asked why he is was holding so much left aileron, the stick was pressing slightly on my left thigh. He said "I wasn't". Check this out he said, and as we sat there he pulled the stick all the way back and centered the flaperons as viewed from the cockpit. The stick was pressing on my left thigh and on his right one. It took a while studying the plans to see why this is so.
 
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