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-   -   Elevator Trailing Edge Bend (https://vansairforce.net/community/showthread.php?t=137222)

tsw94r 04-28-2016 05:45 AM

Elevator Trailing Edge Bend
 
Hello All,

I'm ready to make the final bend on the elevators. The instructions tell you to follow the profile on the plans, but I can't find the profile to save my life.

I understand how to make the bend, just not what the trailing edge should look like when I'm done.

Tom

wjb 04-28-2016 07:35 AM

The closest thing I found was Dwg 4 zone G-10, which shows a end view of the elevator.

The skin needs to be bent down so both sides touch the spar. I followed the suggestions in the aileron section to make the surface up to the final bend as flat as I could .. use a straight edge from leading edge to trailing edge and check for a concave or convex profile and adjust to make surfaces a flat as you can.

Also, before bending, double check your stiffeners to be sure they won't interfere with each other or the opposite surface when the skin is in its final shape.

Go slow, too. IIMC, it took quite a few pressings to get it just right. Overall, its not a hard op.

tsw94r 04-28-2016 10:03 AM

Elevator Trailing Edge Bend
 
Thanks Bill,

I appreciate the tips. It sounds like there really isn't a profile to go by at least in the plans.

wirejock 04-28-2016 10:12 AM

Bend
 
Quote:

Originally Posted by tsw94r (Post 1074418)
Thanks Bill,

I appreciate the tips. It sounds like there really isn't a profile to go by at least in the plans.

There's some info in Chapter 5. Vans is pretty specific about getting a straight, flat surface up to the bend. I believe the radius is also called out. I used a dowell inside the bend then fine tuned the final bend without it.

tsw94r 04-28-2016 10:59 AM

Hi Larry,

I have read and reread the manual and plans, but can't find any reference regarding the radius of the bend. Section 5 does a good job of explaining how to make the bend, but the manual refers you to the plans for the bend profile.

I haven't started the bend yet, but I'm surprised that you would have the room for a dowel or did you just use it initially to keep the radius from getting too small?

bret 04-28-2016 01:11 PM

I used an 1/8" welding rod.

bret 04-28-2016 01:12 PM

or was it 1/16" have to go back and look at my log

wirejock 04-28-2016 02:53 PM

Doh!
 
Quote:

Originally Posted by tsw94r (Post 1074451)
Hi Larry,

I have read and reread the manual and plans, but can't find any reference regarding the radius of the bend. Section 5 does a good job of explaining how to make the bend, but the manual refers you to the plans for the bend profile.

I haven't started the bend yet, but I'm surprised that you would have the room for a dowel or did you just use it initially to keep the radius from getting too small?

I knew you would call me out!:eek:
Sorry, I can't find it. Maybe it was a VAF tip, but according to my log, I used a 3/16" dowel.
I used a strip of Gorilla tape to keep it from slipping out. After the initial squeeze, it was removed to allow the skins to bend past the final dimension. They reflex so you actually end up bending slightly more than the final angle. The biggest problem is the reflex on the bending jig. Even 2x6 will bend in the middle. I used at least 5 huge door hinges on mine.

hayabusa 04-28-2016 06:10 PM

Now is good time for some forward thinking. Check this thread and anything else you can find on the subject of elevator misalignment or twist.
http://www.vansairforce.com/communit...ad.php?t=96921
Any amount of twist in the elevators will not necessarily become apparent to you if you simply follow the plans. What you will end up with is the elevators in trail as per the balance horn positions relative to the stab, you`ll drill the steel control horns off to the control rod as per the manual, but the inboard trailing edges of the elevators will be off quite a bit and it won`t even be mentioned in the plans.
You need to devise a jigging method to ensure the left and right elevators are a matched pair.
The twist can start being built in from the bend in the trailing edge if it is slightly off.

wirejock 04-28-2016 06:22 PM

Jig
 
Quote:

Originally Posted by hayabusa (Post 1074573)
Now is good time for some forward thinking. Check this thread and anything else you can find on the subject of elevator misalignment or twist.
http://www.vansairforce.com/communit...ad.php?t=96921
Any amount of twist in the elevators will not necessarily become apparent to you if you simply follow the plans. What you will end up with is the elevators in trail as per the balance horn positions relative to the stab, you`ll drill the steel control horns off to the control rod as per the manual, but the inboard trailing edges of the elevators will be off quite a bit and it won`t even be mentioned in the plans.
You need to devise a jigging method to ensure the left and right elevators are a matched pair.
The twist can start being built in from the bend in the trailing edge if it is slightly off.

Good point. I made a jig.
Hopefully they're straight. Guess I'll find out eventually.
Two pieces of melamine.
2 each 12"x 24"
1 each 6" x 36"
4 each studs 1/2 wood thread, 1/2 sheet metal thread
4 each wing nuts matching the sheet metal thread
Trace the end rib on one end piece aligned with the center line and more than 6" away from one end.
Clamp the two together.
Cut the "V"
Drill two holes evenly spaced along the 6" line.
Disassemble.
Place the three pieces on the bench.
Match drill the 6" brace through the ends.
Screw the four studs in the holes in the 6" brace.
Slide the uprights over the studs and install a wing nut on each.
One jig done.
Assemble the elevator in the jig.
Hang two plumb bobs from each end.
Shim the bottom of the jig till the bobs are perfect and it's square and straight.


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