Hatz Biplane Association

M Lightsey wrote:Great looking jig.
On NX1279, we took a different approach. We made up the ends with just under half required tubing length. As the wings were being assembled, the tubes were Bolted to the spars then joined in the middle with a simple fishmouthed outer sleeve.
Really simplified the alignment/length issues.
Mark

Gee, I wish I'd thoughta that!

Nick

Don't forget, you'll also have left & right hand threaded plugs.

Got it..thank you Doug.

You will also have threaded plugs of two different diameters. The ones that fit in the cabane & N struts are different than those in the compression tubes.

Here a pic of mine before they were finished...

The compression tubes that utilize the threaded plugs call for the plugs to have a shoulder that matches the O.D. of the tube and is then reduced to fit the I.D. of the tube. Welding is accomplished by both plug welds and an edge weld where the shoulder on the threaded plug is welded to the end of the tube.

The PEMs are carried by McMaster Carr as you found. I made my own, but either will work. The PEMs are tacked to the bracket.

Regarding the rosette (plug) welds, AC43.13 Section 4 discusses welding and covers this. It explains how to determine the size and spacing of the plug weld based on the diameter of the tube.
( http://www.faa.gov/regulations_policies ... ntid/99861 )

Welding (like electrical) has it's own set of symbols, some of which are on the plans. Here's one link that explains some symbols. Scroll down for some diagrams.
http://www.therangerstation.com/Magazin ... ymbols.htm

Just to verify I understand correctly; I'll find a machine shop to take a round bar 4130 (sized to fit in the tubes), cut it into 3/4" sections (14 pieces), trim a 3/8" section from one end of each to .060, drill/tap a hole in it's center and taper/chamfer... stick it in the tube and do a weld in the 1/4" holes I'll drill in the tubes about 1/4" from the ends...no need for PEM's. Then I weld the bracket to it. Is that basically it?

Sheet 5 calls for 8 of part 5 (PEM), but looks like I would need 10 (if I were using PEM's), so either I can't add or that's a typo. I'll be using part 6 instead of part 5 PEM's. BTW, found those PEM's at McMaster http://www.mcmaster.com/#pem-style-nuts/=lvq5xp the part number is S-0524-2 (zinc plated).

What does that symbol mean that has an arrow going to where the tube attaches to the bracket? And a couple have a note to tack to place, if I'm reading it correctly.

Thanks again,

John

Great looking jig.
On NX1279, we took a different approach. We made up the ends with just under half required tubing length. As the wings were being assembled, the tubes were Bolted to the spars then joined in the middle with a simple fishmouthed outer sleeve.
Really simplified the alignment/length issues.
Mark

Thank you for all the replies. Thank you Mark for those photos. I decided to go with gas welding...bought the equipment and took the EAA course in February. It'll be a long time before I get to the fuselage, so I'll be practicing a lot and I'll give the compression tubes a try. I had been thinking about making the fuel tank also, but after seeing other's try it, I decided I better just buy it.

Nice jig, Mark. I think I'll use that when I get around to welding my tubes.

Hello John,

I guess I'll back up what some of the other guys are saying about this. First, about the threaded plugs. I bought some 4130 round bar stock, and had a local machine shop make the plugs, using the drawings on the plans. I also had them make plugs for the cabane and interplane struts, the elevator idler and pushrods, the aileron pushrods, etc. (of course, noting the tube sizes for those other things). Instead of messing with PEM nuts, I just had additional plugs made, identical to the ones for the center section tubes. For the TB-1 and TB-3 tubes, I just rosette welded the threaded plugs in place, and then welded the assembly to the flat end fittings. A little heavier, but MUCH easier, and stronger too. All of the plugs together cost me less than $200. If you have a friend with a lathe or who works in a machine shop, so much the better.

As for John Hanson's comments... this is a good way to do this if you insist on welding with gas. I used TIG, which having tried both I find is infinitely easier and more precise, and ideal for welding pieces of dissimilar thicknesses (like joining these plugs and .090 fittings to .035 tubes.) If you are having any thoughts at all of welding your own fuselage, or just want to try welding to decide if you're up to doing the fuselage, these tubes, the spar fittings, and the aileron bellcranks are a great place to start. They are simple, and not too much material and time is lost when (not if) you screw one up and have to make it over again. By the time you are done with the compression tubes, you'll be making some welds that you'll feel pretty good about. I know I did. And of course, take examples of your work to your tech counselor for critique. A great way to learn!

Attached are pictures of my homemade jig for the compression tubes. It is sized for the longest tubes (TB-2), and I simply used nuts to adjust for a smaller size when welding the shorter tubes. It's made from a length of square tubing from the Home Depot, and a couple of flat scraps. It took a couple of hours to build, and worked great for all of my compression tubes.

Good luck,
Mark