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Aileron Twist??

TASEsq

Well Known Member
Patron
I am up to page 22-08 where i have riveted the aileron nose ribs to the nose skin. Once the nose ribs are riveted in place, the skin really isnt very stable - is this normal?

The next step was to install the aileron spar - and learning from my flap experience, i thought i better check that there was no twist in the spar before install.

I placed it on a bench i know is perfectly flat and checked for any rocking, and twisted the spar to correct this. The winding sticks show that it is flat - no twist.

However, when i install it into the skins there is a lot of twist present. Presumably, this is caused by the skin itself - which i am not really sure how this is possible. The nose rib rivets all seemed to go in fine - some needed a little persuading, which i assumed was due to the tightness of the skin over the assembly.

All i can think if is to try and measure the twist, and correct, prior to installing the spar - but this is very difficult due to how warped the skins are without the spar in place. Or just twist the nose skin assembly an arbritraty amount and cleco the spar back on and see what happens.

Anyone have this experience or have any advice?

Overall i am finding the ailerons very challenging - lots of problems so far. It's like they are from another model or something - nowhere near as clear instructions as the rest of the kit. I'm honestly a bit frustrated.
 

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Here is the pic of the skins wihtout the spar - banana like.

Edit: I have no idea why the photos are upside down, sorry! Probably because i am in Australia.
 

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Trent,

I've not built a 14, but my 7 had a similar issue on one aileron, something discovered after assembly. Another buddy is building an 8 and saw a similar result, a slight twist in the assembly once fully riveted.

I does seem that the skin drives the twist, and since everything is pre drilled, there's not much adjusting to do.

That being said, you'll likely find that the twist changes again after assembly, IMO because the final riveting and seating of the dimples moves the alignment once again.

On the good front, the errors seem to all dilute once you get the wing assembled and concern yourself with aligning trailing edges across the wing span.

This probably isn't what you wanted to hear, but hopefully my musings will illicit more comments from those more experienced than I ...
 
I did mine earlier this summer and had the same issue. I clamped one end of the assembly onto my workbench with the spar flanges facing down and a spacer in the web so I didn’t damage the spar. High density foam piece over l.e. skin before clamping. I put on a pair of mechanics gloves and twisted the opposite end of assembly. Took a couple good goes but got it very close. The final aileron was twistless. BTW, whenever I use the same method to check for twist (winding sticks??) I put them on the flanges, not the web. Sometimes the web will have a slight bulge and show a slight twist when there may not be one.
 
Thank you - I religiously read all the threads for each chapter on your great wiki, but there were none in the aileron section that covered what I am seeing, as far as I can tell.
 
I have built my 14 flaps and ailerons without any issue although this is my second RV slow build so i have some experience.

Building as per the instructions is important it will steer you out of trouble but thinking about what you are trying to achieve is also important
To prevent twist i used the same method as i did with my RV-7 rudder 12 years ago

Buy a length of steel box section and with a similar length spirit level
make sure its straight .... they usually are
Use the aileron skin and back drill it to the box section Cleakoing as you go
( you could use the other side of it for the flap )

keeping the skin on the box section will keep the whole thing from twisting
When it came to riveting the trailing edge i used some polyurethane sealer with on each side of the wedge and cleakoed every hole to the box section When it cured i went ahead and back riveted the trailing edge.

Checking again with the level after riveting gave me zero twist and no wavey trailing edge :)
 
Buy a length of steel box section and with a similar length spirit level
make sure its straight .... they usually are
Use the aileron skin and back drill it to the box section Cleakoing as you go
( you could use the other side of it for the flap )

keeping the skin on the box section will keep the whole thing from twisting
When it came to riveting the trailing edge i used some polyurethane sealer with on each side of the wedge and cleakoed every hole to the box section When it cured i went ahead and back riveted the trailing edge.
Did you cleco the trailing edge to to the steel box or other area of the aileron/flap.
I have done similar method for the trailing edge of the rudder using angle instead of a box but it seems the concept is about the same.
 
Before you set blind rivets through spar in to nose ribs, remove the twist by shimming one of your cradles. Then set your blind rivets and check. Then check again as per step #7 page 22-08. That’s where I had to apply a fair amount of force to fine tune it.
First picture is for Step 4
2nd picture is Back to back angles to hold T.E. true while proseal set up.
 

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You may want to twist a little extra in the opposite direction so when it relaxes it will comes back to true.
 
Thanks for all the advice.

I did the big twist and it worked nicely. Clamped one end of the spar down to the bench, then twisted and checked etc. Took about 5 steps to get it true. Then riveted the nose ribs to the spar, and afterward it was still true.

Hopefully this will prevent a twisted aileron later on by getting it sorted now. I tend to think the "d" cell is basically set now. the nose ribs are basically holding the skins and spars together - i don't see how they can move much anymore.

The first 3 photos show the setup - the last 2 show the twist before and after riveting.

Thanks again for everyones help.
 

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The waviness of the skin, and twist that you showed in your first photos is totally normal for an assembly that has a skin that has been been rolled and press formed like the aileron nose skins have.
Twist related alignment in an assembly becomes locked in when the "box" is closed.
In the context of this assembly, that will be when the riveting on the spar gets done (that will be closing the box on the nose section of the aileron).
So to minimize the likelihood of twist in the aileron, you need to assure it is flat and twist free while the top and bottom flanges of the spar are riveted.
 
Thanks Scott,

Appreciate your input.

Keeping the assembly twist free while riveting the skins to the flanges is very difficult - I've found a digital level to be almost too precise to tell if it is ok. The winding sticks work much better but can't be used on the skins.

Any suggestions?
 
Not sure why you say you can’t use winding sticks on the skin. Tape them to the top or bottom skin. They’ll be pointing up toward the ceiling, if your aileron is in the cradles, but it’ll work. You can also check the aft, inboard and outboard corners of the top and bottom skins before you rivet the bottom skin. They should line up exactly. If they’re out then there may be a twist. Also, follow the rivet pattern in the plans for the bottom skin. Check frequently for twist.
 
Did you cleco the trailing edge to to the steel box or other area of the aileron/flap.
I have done similar method for the trailing edge of the rudder using angle instead of a box but it seems the concept is about the same.

Yes i used the box section in the same way for the flap and rudder
I also used a perfectly flat work bench to constantly check for zero twist
 
Thanks Scott,

Appreciate your input.

Keeping the assembly twist free while riveting the skins to the flanges is very difficult - I've found a digital level to be almost too precise to tell if it is ok. The winding sticks work much better but can't be used on the skins.

Any suggestions?

Our experience is that if Step 7 & 8 are followed, it produces a good result.

A bubble level can be used instead of a digital level. If the bubble visually appears to be in the same position at both ends of the spar, you should get a good result.
 
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