how to make this part on the horizonal stab ?

[fairchild1934]

I see on the horizonal stab---- on the inboard edge of the leading edge tube--- there is a bolt hole and a doubler that looks like its making a thicker bearing surface for the bolt. The leading edge is 7/8 ----- but the plans say the double is also 7/8-........

I had assumed that the doubler was just slid on using a larger tube that would telescope over the LE tube---- but that obviously wasnt what Bob intended.

so what --- DID--- he intend. Do I split the doubler in half like a clam shell and use the two open longitudinal seams to weld it to the LE tube ? ( and then also around the rest of the edges ? Thats the only way I see to get a 7/8 tube OVER another 7/8 tube------- as a doubler.

Tim

[alaskabearhawk]

Can you post a picture of the section of the plans? I’m having trouble visualizing what you are dealing with. I don’t remember anything like that on the 4-place.

[geraldmorrissey]

At the root of the stab leading edge there is a 3" × 7/8×.049 tube that is welded to the 7/8×.035 leading edge tube. Those tubes are cut on an angle and butt welded together. There is no sleeve covering the inboard end of the L.E. tube.
Cheers
Gerry
Patrol #30

[alaskabearhawk]

That makes sense.

[geraldmorrissey]

20250731_121007.jpg 20250731_121018.jpg Maybe this will help. My inboard L.E. tube is cut long so my jig have something to index to. The left side of the image is inboard.
Cheers
Gerry

[fairchild1934]

wow-- that makes NO sense to me----- you have a weld like that with no inner sleeve ? is the object to have a thicker wall at the bolt hole ?
why not slide another tune inside it and rosette weld through holes ??????

[fairchild1934]

and- I would have NEVER guessed that from the plans !!!!!

[jaredyates]

Try calling Bob, if you can catch him, I'm sure he would love to talk about it.

[fairchild1934]

I think I will try that tomorrow ----- 4313 calls for an inner sleeve for a tube splice like that. A butt weld may be OK depending on the expected loads
the joint will see. I would guess that a slip over bushing wasnt used so there is not an unsightly step showing under the fabric. But why not just slip a close fitting tube INSIDE the 7/8-.035 tube ? Have to look on spruce to see if there is a tube that could do that- maybe a thick wall 7/8 cut down in the lathe..... (???)

T
image.png

[gregc]

If you haven't already, I suggest buying Eric Newton's excellent build manuals. I built a kit and still found his scratch build manuals to be an invaluable reference and source of techniques. They are well worth the cost. I don´t think he would mind me copying the bit that addresses your question.

>>>>>
The leading edge tube is 7/8 x .035. However, the drawings show a stub of 7/8 x .049 tube about 3" long welded to the root end of this tube. This is to beef up where it bolts on the fuselage cross tube, to prevent the tube being crushed by the bolt/nut. There has been some discussion that you can simply use 7/8 x .049 for the full length of the leading edge and not worry about the weld there. This is approved by Bob, but adds weight way out at the end of the tail. With such a large leverage, that weight can add up to big problems with Weight & Balance calculations. It’s probably a good way to go if you plan to hang a heavy engine out front (like the O-540). The 7/8 x .049 stub is butt welded to the front tube using a scarf joint. This joint must be a 30-degree angled cut to meet aircraft standards. This gives a longer weld area than a simple 45-degree cut and spreads the loads out more.
>>>>>

[geraldmorrissey]

I struggled bending the 7/8"×.035 leading edge tube. Bending a 7/8"×.049 wall tube cold might have been too much for me using homemade wooden mandrels. I recommend you build per print. I also recommend Erics book.

[fairchild1934]

yes- I noticed that 7/8-.035 was PLENTY hard to bend ...... ( I made a 2 piece french curve out of 2 pieces of 3/4 ply glued back to back with a semi-circular groove for the tube to lay in.. and I slipped a 3/7 steel motorshaft inside the tube as a handle. Prob couldnt bend thicker like that. )

I have Eric's disks- but I completely forgot to look there. I will open that storehouse up and see if that part is shown....

The Pipers have a chromed cross tube that slides inside the ends of the stabs with a cross bolt.
I think I need to look and see which half is the inner tube and which is the outer tube. Wonder why I couldnt tack a tubular bushing inside the inner tube
parallel to the cross bolt. I could maybe cut it into a circle in the lathe--slip in in the end of the inner tube and then tack it from the open end. Then the cross bolt would put that into compression end ways. Might have to make a holding fixture to hold it in the lathe at 90 degrees....
The pipers also use that type of inner cross bushing where the spars attach to the two fuse. stubs.

I will try to see that In Eric's disk before I bother Bob.

[fairchild1934]

I just looked in Eric's disk---- but he does not show a welded on piece on the end. appears he used the thicker tube all the way across. The text there says this---

5. Again, make absolutely sure that the root end of
the forward stabilizer tube is perpendicular to the
fuselage centerline for at least its first 3”. This
is important because later on, the stabilizer will
mount to the fuselage by sliding this forward tube
over a 3/4” cross tube on the fuselage.

So it appears that the center joining tube is 3/4 and slips inside that short welded on section. I have several feet of that thicker tubing ( I think) so I better make sure some 3/4 tubing fits inside it nicely before I weld it onto the end----- :-)

so I guess if there was to be a anti-crush bushing added it would have to go inside the center tube and not on the stab tube. so I can deal with that bushing question later. so for now I need to go check to make sure the tubing I have for the stub is a good tight fit OVER 3/4.

i still wouldnt mind some kind of re-enforcement between the welded on stub and the LE tube. Maybe an on-edge piece that would be inside the fabric if
welding it on wouldnt distort the roundness of the outer tube. (which it might want to---) Have to think about that.......

Tim

[alaskabearhawk]

Apparently, I did the 7/8ths .049 for the entire LE. It seems like a lifetime ago!

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

[fairchild1934]

Looks like I will do it to Bob's plan. It would have been easier to weld that piece on before I bent the leading edge---- but thats OK.
i may try to tig weld that part on while using an inside argon purge. That my give a nicer quality weld since it sis a butt weld with no inner tube as back-up.
if I dont like the weld for some reason I have 2 more feet of tube on the tip end- I can chop it off and repeat.