Therapy Project

Olibuilt said:

Why did I miss your post? I just ran to my hangar to take some pics of my 6'' certified 1.250'' gear. Looks kind of similar to what you've built.

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Very nice, Oli! I see you reinforced the tube under the gusset, too. I didn't do that, but it looks like a good idea.

The angle looks a little shallower than mine. I have 43 degrees. Did the 6" extension demand a little different angle?

Those gear were not built by me. They were on a Pa-18. I assume they are 6" extended Atlee Dodge.


Let me know if you want more pictures or any measure.

No real dramatic pictures to show, but steps after steps and incremental progress. I didn't document very well the straightening of the axle ears where they connect to the shock struts, but it was a simple matter of heating and pressing in a vise. I will clean them up and dress with the mill if necessary to get the gap at the specified 1 1/16" dimension.

Then I weighed the gear assemblies. 7 pounds 15 ounces for each on my fish scale.



Then I decided to weigh the fuselage without the gear attached. It is not a perfect weight because I had to weigh at two different spots, but it came out to 95 pounds at this point. It still needs tabs and the turtle-deck lattice, so it will weigh more.

Other things that needed tweaking were the lower rear longerons. When I welded the X brace, they warped inward. It bothered me enough that I removed the brace and clamped some angle iron to the longerons, straightened them out, and put the brace back in.





I've been convinced to add the 3/8 vertical tubing to add triangular stiffness in the aft sections, but that will be for another day (I have .028 walled tubing waiting).

Finally, I'm tossing in an idea for the shock system. The idea is to use bungees for tension, but have a telescoping tube with an internal piston. Add some automatic transmission fluid above the piston with a fixed disk with appropriate sized holes for dampening located above the piston travel.

And.... have an air chamber above that to adjust pressure. The air pressure works in opposition to the bungees, so you'd start with somewhat stiffer bungees and then soften the ride by increasing air pressure.

I'm attracted to bungees because they allow more travel than a compression spring. I was interested in an air suspension but the piston size seemed to have to be too large if air was providing all the support. And I wanted some sort of integrated hydrasorb. It is just in the concept stage, but I kind of like the oddball idea:


So that's the latest stage of my therapy. That and I've started working on my instrument rating because, well, I need more reasons to be flying.

smart on adding the verticals/boxes... you will HATE .028 welding.... bad idea... welding along then poof, gone! or at least form my experience using it for that purpose...

Don't forget vent holes on those 3/8 tubes. If you do you'll find out on the first one. Welding .028 and Piper channel to .035 is tedious, eventually you will find just the right spot with your torch setting.

Thanks for the warnings on .028. I've welded some of the 1/4" channel and if you are not careful it disappears, as Mike said. I'll start with my smallest torch and see what happens. Good reminder on vent holes Cub Junkie.

If all goes south, I have plenty of .035 on the shelf.

Time for an update. I left off contemplating 3/8 .028 brace tubes. They went in fine, although I learned I needed to brace the span they attach to with angle iron to keep them from sagging. I finished these up 2/2/2019, but I only took some photos mid-process.







Then, over the past several half-days, I spent a lot of time trying to fabricate wing attach hinges. The plans specify .090 4130, which I used. But between trying various bend techniques and messing things up, and finding that the drawings of the rear hinge don't give you something that matches the cluster, it took time. But steady as it goes, I made a bit of progress.





Getting the bend radius right took me some time to figure out. I left out detailed photos of duds that I produced, but I made a few.








After a lot of fiddling, grinding, trimming, leveling, etc., I got to the point of borrowing jimboflying's alignment technique.



I've got other photos I tried uploading, but my connection seems patchy right now. I've gotten the right side lightly tacked and am waiting for time to install the left side.

RVBottomly said:

Then, over the past several half-days, I spent a lot of time trying to fabricate wing attach hinges. The plans specify .090 4130, which I used. But between trying various bend techniques and messing things up, and finding that the drawings of the rear hinge don't give you something that matches the cluster, it took time. But steady as it goes, I made a bit of progress.

Getting the bend radius right took me some time to figure out.

Click to expand...

In situations such as this I find it helpful to make a test pattern from the cardboard of cereal boxes. It saves cutting several parts that don't fit from the 4130.

skywagon8a said:

In situations such as this I find it helpful to make a test pattern from the cardboard of cereal boxes. It saves cutting several parts that don't fit from the 4130.

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I miss the days when pizza boxes were thin cardboard, used to keep allot in stock
The frustrating part about the cardboard in this case is dealing with "bend allowance". I have yet to find a pattern material that truly allows a proper "paper doll" of the part you are trying to produce.
The closest I find now is using a variety of plastics such as HPDE in a similar thickness to the part. It still is not a sure bet to hitting it right.

Oh, and with many parts like these wing hinges, IF I can find a box tube that is proper size to the needed part I use it. This way the dimensions are true with little chance of cracking along the bend.
With the milling machine it is a simple task to whittle the tube to what is needed.

I have a stash of thin cardboard boxes in my hangar for “just in case” fabricating. I should probably organize it better, looks like a hobo camp under my workbench.

I tried card stock, manila folders, and a box from Costco. They all gave the general idea.

For the rear hinge fitting, the shape was just plain wrong. I was nervous because on one drawing it showed the fuselage tubes in a completely different arrangement. If I had done it that way, the hinge would have fit. But what I had built were shown on the fuselage construction sheets. The fitting would not be close to fitting.




I pondered things, looked at the Northland drawings, and then at my set of Wagabond plans. Five simple words on the Wagabond plan would have cleared things up on the 2+2 plans: "Trim this side to fit." The Northland plans have two alternatives. One is symmetrical like fitting in the photo above, the other shows right and left versions with a swept down side that fits the tube coming down.

That's why this is a Therapy Project. Learning procedural processes for an end result. Next time will be faster while making fewer parts. I can't imagine poring through law books making certain that I cross all the Ts and dot all the is.

As much as I complain about my caseload, I'm having the time of my life. Like Jerry Jeff Walker sang, "gettin' paid for something I'd be doing anyway." At 60 I have more fun and more energy doing what I do than most of my younger colleagues or clients. I can't explain it, but I'm grateful to simply be busy on multiple fronts.

Sky is right--it's therapy. Sometimes the little details get tedious, but after a little break it is fun to get back to trying to figure these things out.

I thought about buying the fittings from Univair or Alaska Airframes. It would have been cheaper objectively, considering time spent. But I'm not doing this to save time, but to fill my days and keep myself from unidimensional indolence (which is a real danger for me).

Vic

Piper of course had hard tooling for those fittings. They also used mild steel for them. Forming .090 4130 on ho'made tooling is a test of will.

Month later update

Where does the time go? I was slammed with new cases and ran out of steam for posting. But I still was plugging away a snatched hour here or there.

I worked on the wing hinges and they remain aligned after welding.





Then I worked on the forward spring attach bracket. The plans called for 3/4" square tube of unspecified thickness. The Northland plans showed a u-shaped bracket. I decided to make a square tube out of .090 and put a bushing inside.







Then I decided to form the rear tail bracket.



Tacked things in place.



Since I was in bending mode, I started forming the stabilizer support brackets.





Milled 3/4 semi-holes to fit the longeron.




I still need to trim them up and drill a 7/8 hole in each. No 7/8 holesaw was found in my inventory, so that waits for a trip to the tool store.

Besides these pictures, I have been finishing up the finish welds. Every time I turn the fuselage at a different angle, I find somewhere that needs welding. Takes time--but I don't feel like I'm wasting time.

Rib template

I finally picked up a 7/8 holesaw and finished the stabilizer fittings.





For some reason I didn't feel like welding, so I decided to see what I could do on a rib template. I marked some foam sheet insulation using finish nails poked through the drawing.



Then faired the lines with various battens just like lofting a boat.





Cut on the line with a jigsaw



After gluing the female mold to a piece of light plywood I felt like springing some wooden battens in to see how the dimensions turned out.

Ripped some 1/4 x 1/4 Douglas Fir from a nice vertical grain 2x4 I'd been saving, cut them to the appropriate sizes. I have a fair amount of leftover WEST epoxy from my last boat project, so I lined the mold with waxed paper and glued things together for a test fit.



It was fast cure epoxy, and the temperature in the sun was around 70F. I let it cure for about 4 hours and pried it out of the mold and peeled the waxed paper off.



There are a couple members missing and I didn't add gussets. Nonetheless, the dimensions matched the drawing. Pretty pleased with the result.

FWIW, as shown it weighs 3.8 ounces. Add gussets and the formed nose and I imagine it will double the weight. We will see. The plans call for spruce and thin plywood gussets. I'll have to wait for an order, looks like.

Vic

Vic, Before you go further with the rib, check the dimensions from the drawing to your part. One should not scale a part from a paper drawing as there is no stability to a piece of paper. Usually there are notes on the drawing to this effect.
http://www.supercubproject.com/drawings/pdfs/A3310184.pdf

skywagon8a said:

Vic, Before you go further with the rib, check the dimensions from the drawing to your part. One should not scale a part from a paper drawing as there is no stability to a piece of paper. Usually there are notes on the drawing to this effect.
http://www.supercubproject.com/drawings/pdfs/A3310184.pdf

Click to expand...

Right. I should have added that I measured the dimensions too.



Sent from my SM-J320V using SuperCub.Org mobile app

Turtledeck Arches

Still plodding along. I kept getting derailed in my work life and could barely fit in an hour here or there in some evenings. The worst thing made national news--our only judge got arrested. We've been derailed and I'm being pressed into part-time judicial service.

But my project keeps calling. I was able to work on turtle deck arches. I'm still in the process of fairing the lines. As shown in the drawing, I ended up with some subtle humps that bother my boatbuilder sense. I think I need to look at some pictures to get an idea of the proper fair curve for this part of the build.

Looking GREAT!!

Hope the judicial service isn't as a defendant.

Thanks, Lowrider. LOL, not a defendant--they want me to be a judge for a while until we get things sorted out.

Vic

Good luck sorting! I judged a wet tee shirt contest once...pointers won.

Continuing with fitting stringers

I wish I had more time. I hinted at my work world troubles last post, but it's unwinding more like a local tsunami. Upheaval, long hours, confusion, etc. I think I need therapy more than ever, but have less time for it.


But some time, at least. I continued on the part of the project I understand the least. Stringers and birdcage. The drawings are vague, but looking at photos and other people's projects helps.


So, when in doubt, press on (having verified an escape route).

I cut 1/4 strips of 20 ga steel.



Bent them into 3/8 wide "U" shaped tabs. Here I used a 3/8 extension.





Also planed 8:1 scarfs on some straight grain douglas fir I had cut up to make pieces longer. Epoxy from my boatbuilding projects glued them together.





While epoxy was curing, I welded the little tabs where they should go. 20 gauge metal on thin 3/8 channel took a small torch. I didn't take pictures while doing it, but, other than being tedious, it went OK.

Then put the top stringers in place to eye ball them.





I'm doing all this to locate the attach points up front. Once all that is sorted out, the stringers will get set aside until the fuselage is completely welded up and painted.

Back in 2012, on Bill Rusk's Javron build thread, he asked about weights of wooden stringers.

http://www.supercub.org/forum/showt...g-a-Javron-Cub&p=529458&viewfull=1#post529458

I never could find an answer. Bill's weights for aluminum stringers were as follows:

Left top - 12.830 oz
Right top - 12.855 oz
Top center - 13.810 oz

Now, my scale is not so precise, and only goes to one decimal point, but I weighed the douglas fir stringers, after epoxy scarfs and coating of one side with epoxy, and got these weights:

Left top 12.1 oz. 107" long
Right top 12.3 oz. 107" long
Top Center 13.2 oz. 113" long


I think the Wag 2+2 stringers are longer than a super cub's because the fuselage is about a foot longer, but I haven't taken the time to verify that.

The old super cub plans call for spruce, which is lighter. I'm trying doug fir because I have it and like how stiff and resilient it is. Nice to know that they are in the ballpark of aluminum stringers, if not a little lighter.

Arches on top

Having no clue from the drawings, I spent a fair amount of time looking at photos, etc., trying to figure out the superstructure arches. Big thanks to Marty Feehan (Marty57) and his website for some good photos.

I tried different bending methods for the 3/8 channel. For some lazy reason I didn't want to use heat. I read about hammering on a template, which I tried.



That looked pretty good until I tried to pry it off of the plywood template:



So I ended up fluting the channel with needle nosed pliers.





Then I couldn't resist tacking in place to see what it looked like:





Not shown in photos was how I set up ribs on each side to check the curve of the arches before tacking.

It wasn't all shop time. I also had to try out a new fishing hat my Mom sent me for my birthday.

RVBottomly said:

Having no clue from the drawings, I spent a fair amount of time looking at photos, etc., trying to figure out the superstructure arches. Big thanks to Marty Feehan (Marty57) and his website for some good photos.

I tried different bending methods for the 3/8 channel. For some lazy reason I didn't want to use heat. I read about hammering on a template, which I tried.

View attachment 42872

That looked pretty good until I tried to pry it off of the plywood template:

View attachment 42873

So I ended up fluting the channel with needle nosed pliers.

View attachment 42874

View attachment 42875

Then I couldn't resist tacking in place to see what it looked like:

View attachment 42876

View attachment 42877

Not shown in photos was how I set up ribs on each side to check the curve of the arches before tacking.

It wasn't all shop time. I also had to try out a new fishing hat my Mom sent me for my birthday.

View attachment 42878

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damb, can't believe it was a decade ago when i made this video... in my wookie look alike days... and 60 LBs fatter than today...

mike mcs repair said:

damb, can't believe it was a decade ago when i made this video... in my wookie look alike days... and 60 LBs fatter than today...

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Well yeah!

Good thing I didn't see this beforehand. But now I want an air hammer.

Vic

RVBottomly said:

Well yeah!

Good thing I didn't see this beforehand. But now I want an air hammer.

Vic

Click to expand...

I made one out of some scrap 2x4s and plywood. Rivet gun on top and a piece of railroad track on the bottom. Works great.

Another option, machine up some a male and two female roller dies. The male gets mounted to your milling machine's spindle. The two female dies mount onto the bed of the mill over hold down studs.
The center distance of the studs gets adjusted as needed.
To adjust the radius of the work you move the Y access.
Hand turn the spindle, you do not want to turn that puppy on.

CharlieN said:

Another option, machine up some a male and two female roller dies. The male gets mounted to your milling machine's spindle. The two female dies mount onto the bed of the mill over hold down studs.
The center distance of the studs gets adjusted as needed.
To adjust the radius of the work you move the Y access.
Hand turn the spindle, you do not want to turn that puppy on.

Click to expand...

Sounds like a great idea. Pictures we need pictures.