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New member building a PA18-95

Vic,

No I didn't ask him for drawings. I don't know about the "figured it out from photos" either. This was just my rendering of something close to what Javron does on their wings that looks like it makes sense. There is no engineering behind what I have done, but I don't think it will weaken the wing.

I deemed it necessary because I have seen some pictures taken from a certain Javron Cub on amphibious floats. Alaska, Russia(nearly), the Bering Sea and the like. I don't want to be left out of that kind of action if I live long enough to finish my plane. Sounded like Javron did some testing and determined those wings needed a beef up at that kind of gross. Those wings have the same spars I do and I do like to fish.

From reading what others have posted here and from what my gut tells me, if my wing was going to crinkle, it would likely do it just outboard of the strut attachment points. A full wrap outboard of the front strut attachment point on the front spar and a boxing in of the false spar to the rear spar in the 3 bays surrounding the rear strut attachment point looks like a good idea for the weight needed to do it. I also like the fact that I didn't have to drill holes in my rear spar in places that one doesn't normally do to attach ribs.

It is spooky how floppy aluminum wings are until you get the leading edge on and amazing how dramatically different they are once on. I don't have any experience building wood wings, but I would imagine yours will be quite a bit stiffer. I'm not qualified to offer any suggestions there.

I post lots of pictures in hopes someone will speak up if they see something stupid that I have done. This is my first rodeo, I'm learning as I go.

Sorry I'm not more help.

Jim
 
6oz, 6 Day Mistakes

Made some more errors. 1st one I didn't realize until I had Port wing buttoned up and was ready to drill three holes in Starboard. Laid my aileron bracket up from the wrong hole. About 1-1/4" too far inboard. Looked like it would put the cable in one hell of a bind, had to change it. Made up a different spar stiffener so I could fill the two mistake holes and have it look somewhat planned. Luckily I had already made both top spar beef up pieces...they made nice patterns for all of the holes except for the aileron bracket (had to remake both, had to wait for replacement materials).

Second mistake was laying out the false spar on the Starboard wing. Measured it out, got all the holes where they should go, but somehow got it about a 1/4" too far inboard when drilling holes in ribs. Edge distance for rivets holding one side of my aileron/flap brackets was too close, looked like and was garbage. Had to make reinforcement plate thingys for the outside of the false spar to make myself happy. Made both wings match.

Had to take a SWAG on the lower aileron pulley bracket's angle that mounts on the front spar. Looked like if mounted perfectly horizontal with the pulley cage not pictured, it would again put the cable a bind going to the next bracket inboard that mounts on the compression member.

Making forward progress again. Boys have been helping buck the rivets I can't squeeze. Left handed one decided the dog needed to be wearing safety glasses...

Thanks,

Jim
 

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Just a heads up. In order for the control cable which runs from this pulley to the top aileron horn to be properly aligned, the horn needs to be twisted towards the pulley 3 degrees. This is on Piper's aileron horn drawing.
 
Just a heads up. In order for the control cable which runs from this pulley to the top aileron horn to be properly aligned, the horn needs to be twisted towards the pulley 3 degrees. This is on Piper's aileron horn drawing.

and also remember this when you do your fabric covering that the teardrop cover for this is mounted at a angle also, not straight front to back.
 
Regarding the wings, focus on the budget, I do not see the difference as critical. Regarding his opinion, he would choose aluminum.
 
Wings are flying, kind of...

Finally got starboard side leading edge done. Oldest son helped buck rivets. Good to spend time with him in the shop, but also kind of sad. He's a senior, he leaves for basic training in June. His little brothers are going to have to help in his absence. Plan was to have this project done by now, but things rarely go as planned. Maybe when the oldest is done with school, I'll have it done and he can show his old man how to fly it.

Flush riveted the leading edge. Wanted to try it, like it, but it was a lot of farting around. I was toying with trying to flush rivet the flaps and ailerons, but after doing the leading edge, I'm definitely not going to for many reasons.

Rigged up a pulley system to get the wings out of the way when necessary and have them at hand at home for trial fits to fuselage when that time comes. Very cool to stand underneath them for the first time.

Building tanks next, then flaps and ailerons. Going to try my hand at making my own carbon fiber tank lids and wing tips after that.

Thanks,

Jim
 

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Torch welded aluminum (don’t laugh)

Hadn’t played with this in a while, really need to be in the right frame of mind to do it, and watch it like a hawk. Look away for a second, garbage. One beer minimum and one only. This is .050 6061 T6 with 1/16” 4043 filler, size 0 Victor tip turned way down. Not perfect, but gaining on it. My tanks will be .050 5052 H32, same filler. Going to torch weld corners, one seam, cross tube, filler neck, and over rivets that fasten baffles. Will tig bungs. Was going to have Javron send me blanks, but his are .040, and this will be hard enough for me with .050. He is supplying the bungs, filler necks and cross tubes. Very helpful and friendly guy.
Why torch weld? Because it’s old school, challenging, and I want to say I did it. Not cheaper, may not be better or as pretty as tig, but I guarantee you will waste a lot of time, money and material getting somewhat proficient at it.

Thanks,

Jim
 

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Tig and torch welded aluminum comparison.

WARNING, IMAGES MAY BE DISTURBING TO REAL WELDERS.

Got my .050 5052 on Thursday. Did some more torch welding. Used a Smith Little Torch tonight with their size 5 tip which is slightly smaller than a Victor 0. Then did some tig, weighed, compared, destroyed. Both weigh the same, you’d think that gobby looking torch weld on the right would weigh more, but it didn’t. One of the reasons I’ve been farting around with torch welding aluminum was that I had read some claims to less prone to weld failure, better penetration and the like. When I cut what I had done tonight apart perpendicular to the weld and bent it backwards, it at first looked like I did have more weld that followed the flux on the back side. After a little prying with a beater screwdriver, I realized that was not the case, the aluminum was just annealed further back from the weld.

Conclusions: I think I could make either weld hold gas. Tig is considerably easier and prettier. I don’t have to clean up the corrosive flux with tig. Both welds will eventually break, it was slightly easier to break the tig weld. Going to try some flux formulated to work better with 5052 before I totally decide, but after tonight, I’m not really seeing the advantages I thought I might with torch
welding this particular alloy in this application.

Thanks,

Jim
 

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One of the reasons I’ve been farting around with torch welding aluminum was that I had read some claims to less prone to weld failure, better penetration and the like. When I cut what I had done tonight apart perpendicular to the weld and bent it backwards, it at first looked like I did have more weld that followed the flux on the back side. After a little prying with a beater screwdriver, I realized that was not the case, the aluminum was just annealed further back from the weld.
Interesting and good practice. Do you suppose that by being annealed further back from the weld there is more flexibility in the sheet near the weld? A shock absorber of sorts? When the sheet is not annealed some distance away from the weld but is stiff right up to the weld it would be more prone to cracking.

What 5052 are you using? 5052-0 or 5052-H32? Would one be more prone to crack than the other?
 
Pete,

Good point. I’m using H32. I would guess O would be less prone to cracking, but it would only be a guess. I would also guess that O would harden anywhere that it was heated, so it might be the same thing only in reverse. Just changing where hardened aluminum meets soft. Welding aluminum with a torch is different. My experience has been that you never really get a bright shining puddle like you do with tig. Doesn’t really drastically change colors when it’s ready to add filler. Once you see the skin wrinkle, it’s time. Add filler, move and get the heat away or you will quickly make a hole. The end result is a rougher looking weld that looks more like a brazed joint. You can sink the weld into the joint and smooth it somewhat by going back over the weld with the torch, but it is still ugly. I’m going to try the different flux formulated for 5052, if I don’t get different results, I’m just going to tig the tanks. Once the tanks are done, I’m going to try torch welding some 3003. I’ve heard it plays nicer with a torch and I’m curious. Not before these tanks are in the wings though!

Thanks,

Jim
 
You are to be congratulated for your gumption to do this yourself. I've welded aluminum both tig and gas, it's not easy. It takes practice and proficiency to do an acceptable job. Good for you, go for it. You will have something to be proud of.
 
Thanks Pete. Most people would call what I have something other than gumption. Thank you again for your kind words. I truly admire good welders, sheet metal guys and manual machinists. I may never be one, but it is truly satisfying to make the attempt.

Thanks,

Jim
 
Don’t mater the h number. Once you hit it with torch you remove the heat treatment, unless you dunk it in water at the proper time. The h is just about how they heated and then cooled it....


Sent from my iPhone using SuperCub.Org
 
For welding the H number isn't important but, the -32 does reduce the denting possibilities and increases the overall stiffness of the completed part.
 
Tank Baffle Question

Its been a while. Back into it. Pictured are my tank sides and internal baffles so far. .050 5052, made rib pattern OSB cutout between spars, burned out blanks around patterns with plasma cutter, bent flanges over by putting blank between OSB cutouts, clamping in vise with two additional C-clamps, tinning hammer.

Last picture shows one tank side and one internal baffle. The baffle has a large hole in it to accommodate the brace .tube that runs through the tank at an angle. The hole is about 3/8" larger than the tube running diagonally to keep from rubbing a hole in it. I have cut 1" tall triangles out of the leading and trailing edge of the baffle. I have seen a picture where another guy made additional holes towards the top of the tank baffle and a couple towards the middle. In sharpie marker I have marked where I'm thinking about some more holes, about 7/8" diameter. Top holes would be just below top flange, bottom holes would remove the bottom flange where marked. My question is, do I need these additional holes? If I do, is there a better location for them?

Thanks,

Jim
 

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The top holes are to let the air out when you add fuel to the tank so you can fill it to the top.
The bottom holes allow you to use all the fuel in the tank.
The size of the holes should be large enough to allow full power fuel flow rate when the tank is low on fuel.
The baffles are to reduce the fuel sloshing about in the tank and to help support the top and bottom from excessive flexing.
Any lightening holes ought to be flanged for stiffness to reduce flexing.

From memory the FAA requires baffles in tanks larger than 13 gallons. The number may be incorrect, but it is somewhere in that size range.
 
Thanks Pete! I just stumbled across a picture of some baffles somebody with a heck of a lot more experience building Supercubs than what I have does. It looks like I could take out considerably more material on the baffles. Will flange holes, that makes good sense.

Thanks,

Jim
 
Tank Progress

Decided what I was doing for baffles. Here they are with progress so far. Looks like everything should work. Planning a one piece skin with one flanged joint to the inside in the upper front of tank where I am pointing. Should have a complete mock up tomorrow.

Thanks,

Jim
 

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Decided what I was doing for baffles. Here they are with progress so far. Looks like everything should work. Planning a one piece skin with one flanged joint to the inside in the upper front of tank where I am pointing. Should have a complete mock up tomorrow.
attachment.php

Thanks,

Jim
The ends are usually flanged out. Then the seam is edge welded.
 
Tiny Tank

Before I bent up the real tank skin, I made a small tank with my baffles and tank ends to make sure my measurements were correct and to keep from making big pieces of scrap. Saw this somewhere, seemed like and was a good idea. Took two tries. Also showing how I mated up the inside flange with the outside caps.
 

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Bending Real Tank Skin

Boys helped with this.
 

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Mock up with sheet metal screws and hot glue.

I have used zip in sheet metal screws as poor man clecos where 1/8" rivets go. They are considerably cheaper and lots less clumsy especially when you need a bunch of them. Drilled a #30 hole, hand set a screw.

Another thing that I wanted to try that worked really slick as well was to use a hot glue gun to temporarily hold things together for a trial fit. Bungs, end caps, through tube all hot glued on. It's hillbilly but I like it. Just strong enough to hold stuff together, picks right off easily, no mess. Tons faster than tacking. Everything has to come apart again anyway to clean and get ready to weld. The seam will be tighter in the front when I'm done.

Going to weigh 14.5lbs per side.
 

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Starboard tank in the wing.

I was able to get it in the wing by myself, next time I will find the boys for help. The diagonal closest to the tube on the far side of the bay damn near got wrecked, you have to angle the tube up and slide the tank onto the tube and drop everything in place. Carefully. It looks like nearly everything landed where I hoped it would and I think it will work, but just barely. My goal was to fill the bay to the top of the ribs and down to the top chord on the bottom of the rib with a light tank cover on top. Right now it sits about 1/8" too high. It hits the lower chord of the center half rib in the bay, I think because there are no intercostals to hold it down like the rest of them, and possibly because I did not shrink it enough when forming it.

I believe the only reason it is there is to attach fabric to keep the fabric from flapping in the prop wash. I can't see it doing much of anything from a structural standpoint. The simple solution to my tank dilemma seems to me would be to take some of the vertical L material away to gain that 1/8".

I have some other thoughts rattling around if whittling down that crippled rib isn't ok. If anyone sees anything else that for sure won't work, please let me know.

Thanks,

Jim



I
 

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Looks good.
Consider using larger diameter rivets to hold the baffles to the outside skin with the heads inside the tank. The larger diameter spreads the loads over a larger area. Then weld the upset end on the outside of the tank to ensure there can be no leaks.
 
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