Section 23-2 Longerons

NEED SOME HELP,

HAVING A VERY DIFFICULT TIME OPENING THE ANGLE ON THE ENDS OF THE LONGERONS 5.4 DEGREES. (SECTION 23-02, STEP 3.)

I HAVE USED, WHAT I THOUGHT WAS A HEAVY, SOFT FACED HAMMER, BUT WITH LITTLE IF ANY CHANGE.
I EVEN TRIED PUTTING THE END IN A VISE. THIS SEEMS TO WORK A LITTLE, BUT HARD TO GET AN EVEN TRANSITION.

ANY SUGGESTIONS?

GARY

I put another piece of scrap angle (that I had previously opened just a bit by banging on it), on top of the longeron. Hit the scrap angle relatively hard many times (working up and down the longeron where I wanted to open it) using a 3# metal faced mallet. Did it on the concrete floor in the garage.

Take it slow and look at it or measure with a square every so often.

Tried the vise approach and it did not work for me. A soft faced mallet just bounced.

I too had trouble at first. Hitting the angle with a hammer was at best crude, and the vise method not much better. If you have access to an arbor press or a bearing press it is a piece of cake. I bought a heavy duty arbor press from a guy at the airport for $25. It was easy to apply pressure just where I wanted it. I was able to not only open the angle the correct amount, but taper it smoothly as well. It also made bending the curve a breeze. I liked the control of the arbor press, but it probably would be easier to find someone with a hydraulic bearing press.

THANKS FOR THE INFO. WILL LOOK FOR A PRESS.

3/4" pipe coupling

I put a 3/4" pipe coupling inside of the angle and squeezed it with a vise. If the vise handle is too hard to turn, try putting just half of the coupling into the angle. It is easier to do a little at a time than all at once.
Joe

Longerons

Having built an RV-8 and an RV-3, I found that Van's tends to be conservative on how to do this task. I beat the **** out of the angle with a hammer and it worked fine; it's covered up by the skin so don't worry about how it looks.

Battle of the Longerons

Here is what I put in my log today:

"Today I battled the longerons. I was previously warned that this was one of the toughest fabrication tasks in the kit, and I certainly agree. Opening up the angles on the forward ends is a real bear. The plans say to open the angle with a heavy soft faced hammer. I beat on it for a while with my rubber hammer with absolutly no results. Then I tried the suggestion of some other builders who claim to have been able to squeeze the angle open using a puece of pipe or a socket in a vise. Either my vise is not strong enough, or I haven't been eating enough Wheaties, because the angle never moved. Next I tried Marty Santic's method of protecting the angle with a piece of "sacrificial" angle and beating on it with a bigger hammer. Not only didn't I make any progress, but the scrap piece flew off to a far corner of the shop every time I hit it. I finally decided to just beat on the piece with the big hammer directly. Of course this flattened out the pointed edge of the angle stock, but I figured I could file that flat again and smooth it with the deburring wheel, and that worked pretty well.

Then attempted putting the 2.7 degree twist in the end as instructed. What a joke. How is the average builder using common tools supposed to correctly guess what 2.7 degrees looks like? I think I put way too much twist in.

Had more success with bending the curve. Proceeded slowly and bent by hand pressure, rather than using the hammer again. Then drilled the holes, drilling one at a time and clecoing as I went. Took out the clecos and adjusted the bend several times as necessary. It came out pretty decent I think. Finished with the aft bend and the deburring.

I was going to jump to the plumbing section next, but now I feel I must go ahead and do the next few pages to the point where I find out if the longerons are going to be acceptable, in case I have to order new stock and start over. I am sure I will have to do more fine tuning on the bending and twisting in order to make these longerons work."

The fabrication of this part seems like a lot to ask of the average builder with access to common tools. I would gladly pay extra to have this come from the factory pre-bent using their precision equipment. Especially if the precision needs to be to the tenth of a degree! I suspect I will be ordering new stock for a second attempt, since I don't think I will be able to achieve the 5.4 and 2.7 degree angles this time around.

Longeron

Big John,
If a square is held against the longeron after the angle is spread apart, you should see about 1/16" gap at the vertex. Then twist the end so that the top of the whole longeron from end to end is flat and level.
Joe

I used a hydraulic press. 3/4" galvanized pipe on the bottom, angle on top, then pressed down on the point of the angle to open it up a bit. With slippage and spring-back I couldn't control the process well enough to get within 1.0 degree, so I just eyeballed the angle. The longitudinal bends I made in a vise using the "armstrong" method. The fabrication took 4-5 hours and turned out great. The only problem downstream was that when fitting the skin that goes over the instrument panel, the lowest screw, right side, was a little difficult to fit because the longeron had not been bent inboard sufficiently. The hole was off by about 3/32, easy to work around.

Noticed you are in Agoura, if you ever get up to Big Bear, come by the hangar, we are about 1/10th through the finish kit. e-mail me at [email protected]

If you have the 6" vice called for then you should be able to spread the end with no real problem. Using the crescent wrench makes short work of getting it straight again. The key to this whole task is to use a "Shrinker" to do the long bend, it gives you the control to get it spot on and if you run off a little then use the "Stretcher" to get back on track. The entire process took less than an hour. Most aircraft shops would have one and would probably be able to assist you with it for a small fee.

Best regards,
Vern

I really appreciate all the advice on the longerons. I thought I had ruined them, but now think I can salvage them. See the last couple of entries in my log for details. If worse comes to worse, and I have to order new stock, I'm sure I can do a better job next time.