Tube bending

[geraldmorrissey]

I have a new appreciation for the toughness of4130 cond N tubing. I have just about dislocated both shoulders getting the first empennage tube bent. 1/2"×.049 almost did me in, but Success. Only 7 more to go.
Gerry
Patrol #30

[alaskabearhawk]

LE of the horizontal stab will certainly get your attention...tougher than Chinese arithmetic. But it certainly gave me confidence in the materials.

[rodsmith]

I have a new appreciation for the toughness of4130 cond N tubing. I have just about dislocated both shoulders getting the first empennage tube bent. 1/2"×.049 almost did me in, but Success. Only 7 more to go.
Gerry
Patrol #30

The key to easier tube bending is leaving extra length to provide more leverage. If the tube is cut to size, use a larger diameter tube that you slip over the end of the piece you are bending for increased leverage.

[Sir Newton]

I really like your setup for making bends on the tail feathers. I am going to copy you. two thumbs up! I really prefer to cold bend my tubing material even though it is not necessary. I purchased hydric benders to make certain bends on the upper & lower longerons.

[Utah-Jay]

All I have to say is you guys are both brave and 100% more talented than I… Bravo

[Chewie]

Nice Gerry! I see what i have to look forward to. The result looks excellent.

[geraldmorrissey]

Bending is getting easier but still taxing. Bending part #1 took 8 hours. Bending the opposite hand took 45 minutes. A lot of it was getting the bending mandrel to the right curvature. 4130 springs back more then I thought. The mandrel went through three modifications, each time reducing the radius until I got it right. By the time I got good at making the part, I was done. Learned a lot though and it was fun. Many more to go.
Gerry
Patrol #30

[Steve W]

I can’t remember where I picked this up but I bend all tubing on a flat table with wooden circles of different diameter screwed to the top. I plug one end with a fabricated tapered wooden dowel and fill the tube, aluminum or steel, with fine sand with the aid of a small funnel. I keep tapping the end on the ground until the sand stops settling, then plug the other end tight. It will never collapse unless the sand has settled further. It also stresses the metal evenly. I’ve seen metal bent by other methods and when welding the ribs to the bowed piece, it tends to flatten out. As previously mentioned, the 7/8” tubing for the horizontal stab was fun to say the least.
I do all my fuel lines this way ensuring a thorough clean out afterwards.

Steve P203. Glastar, Rebel, Christavia

[geraldmorrissey]

Finished parts, just needs final trim. On to the horizontal stab leading edge. Baby steps.

[fairchild1934]

Gerald----
I built a couple of rudders and did them on a doubled plywood form like yours. I took the router and cut a groove down the edge for the tube to ride in
to help keep it in one plane. Doing it on a flat table might be even easier----
Nothing says you cant anneal a little as you go --- right ?

[geraldmorrissey]

Bent a horizontal stab leading edge tube today. Came out really good but is not as flat as I would like. It's about 1/8" out. Got to figure out how to remove that error. I know what I did wrong so the next one will be better. The 7/8"×.035 tubing bent much easier then I though it would. With a 2 foot lever beyond net trim, I could apply some force. Shown are the bending mandrels for 7/8",1/2" and 3/8" diameter tubes. Still need to build a 5/8" for the top of the rudder. Also shown is the 7/8" mandrel mounted on a steel plate. The mandrel allows you to bend and when the part is rotated 180 degrees remove bend. The part is shown untrimmed. I dreaded this job but it was not bad at all. Fear of the unknown. Plus I got reacquainted with my router table. One more leading edge to bend and on to final assy.
Gerry
Patrol #30

[alaskabearhawk]

I know that it may be a bit too late, but I mounted my bend mandrel on my build table. That way I could keep the the bend flat…2D vs 3D.

[geraldmorrissey]

Don't have anything in the shop that's beefy and heavy enough to resist the torque I put on the tubes except the vice.

[alaskabearhawk]

How I did mine without a vise. Worked out fine, but it was a long table (18ft) and pretty heavy.

http://www.mykitlog.com/users/display_log.php?user=yeeeha&project=527&category=7248&log=144020&row=159

[fairchild1934]

gerald---
I had a tiny bit of out-of -plane wiggle--- so I had a steel table that I clamped it down to and let the bend area hang over and then gave it a little twist against the table- then slid the work down to the next wiggle- and gave it a twist there. When done it would lay flat on the table. It was 3/8 cro-mo.
so not too hard to tweak----

tim