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**Pinejuice** · 03-30-2016, 10:59 AM

Looks great! Thanks for sharing these design changes you are making, explaining why, and showing your process.

**lsa140** · 03-30-2016, 10:40 PM

I switched from a gas lens setup to a standard #5 cup with a short back cap for the tight spaces. 1/16" sharp tungsten. I was expecting oxidized welds with such a small cup, and very limited electrode extension. Surprisingly, the welds were coming out silver, and I was able to get quite a bit of electrode protrusion for the tight corners.

Added the last piece of tubing to the tail spring attach area, and welded it. Time to build a rotisserie.

**Chris In Milwaukee** · 04-05-2016, 09:50 PM

I have a C-85 in my C140, and it's got some gumption! Also flew a local PA-11 with a C-90 in it. Amazing how nice they are.

**lsa140** · 04-09-2016, 11:45 PM

Finished up the tail side of the rotisserie. The multiple telescoping tubes provides a long range of adjustment. I picked up a couple 1/2" barrel nuts and built my own u-joints. I need some additional washers and bolts to final assemble the joint. For now I will be grabbing onto the tail post with some u-bolts covered in rubber tubing. Later in the process a 7/8" piece of tubing will slide into the tail spring socket and mount to the u-joint plate.

**N942VT** · 04-10-2016, 06:09 AM

Nice idea with the barrel nuts!

**lsa140** · 04-11-2016, 01:23 AM

The fuselage mounted on the finished rotisserie. The small scaffolding casters lock in roll and rotate. It rolls across small lips and gravel easily. A set bolt on either end locks the fuselage in rotation. Time for some welding.

**lsa140** · 04-16-2016, 12:37 AM

Welded the tail post, and continued working forward. I was reminded again how much more difficult 028 is to weld. Especially when welding to thicker wall tubing. In theory you keep more of your heat on the thicker tube, and let the puddle wick over into the thinner tube. Easy to do sitting at a table, a whole different challenge when attempting gymnastics to reach a weld cluster on a fuselage. The pulsing box I purchased for my Diversion TIG really helped tackle the 028 tubing. I don't feel like it is needed on 035, but it really helps with the thinner wall.

I'm dealing with residual oil inside some of the tubing. It is left over from the manufacturing process. It slowly worked its way down several of the vertical side tubes and covered the lower clusters. I finish weld the upper cluster at a station, then use a fine stainless wire brush dipped in acetone to clean up with tacks/oil. Also, grinding down the tacks help them assimilate into the weld.

Preheat with a trigger start propane torch, on a 12' hose, attached to a 20lb propane tank. It works well, and is easier to move around than a torch with a bottle attached.

I had to adjust my welding after getting used to 035. It works well to keep the weld beads a little narrower. Use plenty of filler, its easy to undercut 028, and that is the last thing you want on such a thin piece of tubing.

I was getting very frustrated after a couple hours of dealing with oil, thin tubing, and trying to get in a good positions to weld the tight tail area. Took some deep breaths, enjoyed some spring air outside, and came back to it with a little more patience. This is really challenging, but very enjoyable.

**Clint B** · 04-17-2016, 07:47 AM

I really enjoy reading your posts and looking at the pictures.
Have you weighed the fuselage? I'm curious how it compares to the cub types.
When I'm welding thin to thick, and the thin wants to try to burn away, I "build bridges" between the two pieces, i.e. Put a tack weld every 1/8" or so along the weld that your having trouble with. When you come back over its the final time, the tendency to burn away is greatly reduced. Seems to work for me, your mileage may vary.

**lsa140** · 04-17-2016, 11:27 AM

Thats Clint, I haven't weighed the fuselage yet. Do you have a weight from your C-90 cub build? Comparing the tubing, the LSA and cub use very similar sizes/wall thickness. The LSA uses 3/4x028 upper longerons. I almost switched over to 035, but my tubing kit already had the 028 bent and notched. The bearhawk line has more structure above the cabin. There is an upper truss structure that runs from the rear baggage to the tubes that run down in front of the door/firewall. The rear fuselage is also full height, unlike the cub fuselage which tapers down behind the rear spar carry through and relies on formers to continue the fuselage shape back to the tail. I'm guess the LSA would be very close in weight, but possibly slightly heavier due to the extra tubing.

Thanks for the welding tip! The bridges would act as little heat sinks as well. I took a TIG welding course at the community college during high school, and hadn't picked one up for 18 years. I definitely feel my limited experience when going from welding in convenient positions to inside an airframe. Being able to see where my electrode is at, and what it is doing to the metal is a real challenge in some of those tight corners. Worked on refining my welding lense/glasses setup yesterday, we will see how things go today.

**Clint B** · 04-17-2016, 12:46 PM

If I remember correctly, mine weighed 98 lbs and that was with some of the Alaska mods.
A friend of mine built a javron cub and powdercoated and stringers installed, it weighed 104 lbs.
I'm really surprised that people are still building Cubs with the stringer setup the way it is, as its really nothing more than an evolution of the Taylor E-2 which was practically a parasol. The top longeron like the bearhawk uses is much stronger and much easier to weld.

**Patrol28** · 04-17-2016, 06:08 PM

Being patient with the 028 wall is worth it. Hard to tell the difference when you pick up a long length of 028 over a piece of 035 the same size but when you weigh a finished part that's when you realize the wt savings. Good looking work and progress. Having built all the Patrol weldments from scratch I know how hard you've worked.

**lsa140** · 04-17-2016, 10:25 PM

Finally got everything dialed in for welding the difficult to reach thinner tubing located at station G-K. As I move forward in the fuselage there is a lot more room to work. A big thank you to dedgemon for sharing the Servore auto darkening goggles from Amazon in one of his threads. http://amzn.com/B00LKWLSS0 I removed the ear pieces from my glasses, cut two small slits in the face gasket rubber, and slipped them into place. They stay put, and are far enough forward to not contact my face. The goggles with face mask are much easier to get into tight spaces, but dont flip up like a helment. I found that a very bright LED headland allows me to keep the goggles on, easily get in position, and inspect the weld without removing them. I have a lightweight head sock that seams to keep the arc from burning my face. The goggles are highly recommended. Once in a while tubes will block both light sensors, and you will get a mild flash. Again, this wont be an issue further forward in the fuselage.

I swapped out the #8 pyrex cup for a #6 ceramic cup using the same gas lense. This allowed for plenty of electrode extention, better clearance in tight joints, and the funneled shape of the cup provided better coverage with less gas flow for this type of welding.

A small stainless wire brush, dipped into a container of acetone, continues to work well to remove oil and contaminates. After it quickly evaporates, I hit the joint with a quick propane torch preheat.

The cluster shown bellow was covered in oil, but it cleaned up well with the method above, and welded nicely. I dealt with a little contamination, but it was doable. Being able to see well, having the right torch setup, and keeping the weld beads smaller/heat lower worked well for the 028. Welds should improve as I get some more time welding, and move forward into roomier parts of the fuselage.

**lsa140** · 04-17-2016, 10:40 PM

I recieved my axles from Aircraft Spruce, and the 1-1/4 x 16TPI threading die/handle from ebay on friday. I wasn't sure what kind of quality could be had on 4130 with a threading die, but it turned out very nice. A 1-1/4" was drilled in a small 2x4 and slide over the axle. I placed a spring clamp under the block to provide a little resistance, but still allow the block to slide down the axle as threading progressed. The block kept the die completely square for the initial thread cut. After the threads were started, and die traveling properly, I pushed the block down the axle. This allowed the chips to fall clear of the operation. I went slow, cleared often, and used plenty of cutting oil. The threads are very smooth. I'll do a little cleanup where the threads stop, cut the retaining pin slot, and polish things a little. You can see from the photo bellow how much finer the 16tpi over the 12tpi. I plan on getting a lathe down the road, but am trying to keep focused on building.

**lsa140** · 04-19-2016, 12:54 AM

Here is the setup I'm using for preheat. I've been warming up the clusters, and out each tube a short distance outwards.

The welding is going well. Finished through station F-L.

**lsa140** · 04-19-2016, 08:39 PM

Here is what I came up with to grind a radius. Many parts on the Bearhawk have an outer radius centered on a hole. This modification to my folding grinder rest lets me quickly grind a very nice round edge. The rest surface can be adjusted with two slotted bolts to accomodate different radius. After the radius is ground, the rest is folded down, and the edge gets a quick dressing to get all of the grind marks running with the part, and a slight bevel put on the edge. The holes will be reamed to .190 for an AN3 bolt. This is a quick video demonstrating it in action: https://youtu.be/mTV_VlAlT0Q

I used some 3M Super 77 spray adhesive to lightly tack down a part template. It was cut out on the band saw, center punched, drilled, ground, and the template pealed off. A little acetone to remove the adhesive. It went quick, and worked well. I will be using this method for many of the flat parts.

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