Air frame or metal shaping gurus - flat curves in aluminum

I have a question for those of you that do air frame construction (or something similar). When you guys are repairing/building/refurbishing/etc. the leading edge of an aluminum wing, how do you form the curve? Is it stamped ahead of time, rolled, drawn over or on a buck, something else??

Here's why I ask. I'm building an aluminum Model T style tank from scratch and will be using a buck I made as a guide. I had originally thought that maybe I would just get the shape in the aluminum using a slip roll and just try to match it to the buck, but since it's more oval instead of circular in shape, I was thinking maybe it would be better to just anneal the aluminum and just fit it to the buck.

Thoughts?

Here's the buck representing the shape I'm after...



Next... what thickness and grade of aluminum should be used for this? 12 Gage? 3003? It will be riveted construction with two end caps and two internal supports/baffles. Every seam and rivet will be sealed with Pro Seal or similar aircraft type fuel tank seem sealer and the the main seams will be TIG welded for any additional strength needed. It will also be supported by a mounting cradle underneith, so it doesn't really need to support it's own weight, but it would certainly be benefial if it could.

This is the proposed tank concept that was used to make the buck...



Any help would be appreciated guys!

Thanks!
Scooter

 

Use 3003-H14, 0.063 inch thick.

 

For the baffles and end plates, I would anneal the edges, and use a hammerform.

 

Hey I'm sending you something you might be able to use with this?

 

Okay! This is what I was thinking also, but a gage thicker. Is that over-kill? That much harder to roll/form to the curved shape?

EDIT: I just compared the thickness of the two. WOW! Didn't realize how much thicker .080 really is compared to the .063. Had to physically compare the two to really visualize it.

Exactly! I even have the pattern made to make the form for the baffles already. Looks like I'm in the right frame of mind.

OO! OO! What is it!!?? No wait! Surprise me! HAHA!

 

I work at a place that manufactures tanks for oilfield trucks, including aluminum versions (5052, typically). What we make is pretty similar to you have modeled only on a larger scale. Basically we pre-form the ends of the tank and the baffles (they're flanged and domed), set them up on a large table, and use a machine to wrap the shell around the baffles. So I'd say you're on the right track.

 

Okay!! Cool!! That's great info!!

If I go .063 thickness, will I even need to anneal the aluminum? I've honestly never worked with aluminum in this manner. I don't really know what to expect.

 

That would be a place where and english wheel with true radius lower wheels and a go cart slick upper could be used... just a possibility.

 

Hmmm... I'll keep that in mind. Since the tank will be fairly long (or wide, if you will) wouldn't that be sort of hard to keep it consistant from end to end, though?

 

I'd be tempted to flare the round holes in the baffles, for stiffness,
and make the rectangular cut out at the bottom smaller.

 

Yes, I also agree with that. It will definitely be stronger if the holes were flared as well as a smaller pass-thru notch. The smaller notch will be better for baffling as well.

 

Well, you'll be dealing with quite large bend radii so I wouldn't anticipate cracking to be an issue, especially in a light gauge. So annealing may not be necessary in that sense. However, the challenge will be forming the radii by hand and have the shell come out consistent, as you say. Annealing might make it easier to work with, but I can't say for sure. I'm sure some of the experienced fabricators here will have a better idea of what's required.

 

Yeah, I'm definitely concerned about the consistancy of the bend. I guess the baffles will naturally want to help pull it together once the clecos are in place and rivets are installed. In fact, maybe I don't even need the buck. Maybe I could just use the baffles, start at one end of the seam, attach it, roll it, drill and attach it in the next position, roll it some more... and just repeat the process until I'm all the way around... or not.

Maybe it really is just better to get the rough shape using the buck, clamp it, then install the end caps and baffles and go forth with drilling and pinning everything in place.

Just thinking aloud. This is my first go around at something like this.

 

x2. I would even suggest making the notches round and flare them. That way they'd be less prone to fatigue in case the tank is subjected to chassis flex or vibration.

 

First I would suggest you check with Vans aircraft on getting a sealer that is compatable with mogas. We used a roller to form any rounded surface. If you roll it or form it cross grain it will help keep cracking down to a dull roar. If you ever get out around Riverside stop by Flabob airport its EAA west there will be lots of helpful folks around there.

 

Try wrapping it ,by hand, around a post or tube.
The diameter can be much smaller, since the panel will spring back.

Form the small rads first.
A narrow strip of the same material is useful for testing, to determine bend locations.

Since it can be difficult forming a rad right up to the edge of a part,
you might have to cut the piece longer, do the bends, then trim to the final size.

 

I would anneal it. Ratchets straps can be wrapped around the aluminum and used used to pull it in to the buck. That will make it easier to hold in against the buck and see what else you need to do.

 

This is what I had planned on using to seal every rivet and seam.

http://www.aircraftspruce.com/catalog/cspages/prosealtypetanksealant.php

We've been experimenting with it here at work for other sealing applications and it's the most incredible sealer I have ever seen!! Relatively inexpensive as well.

 

Some more great input here! The response to the task is much better than I thought it would be! Thanks guys!!

 

Well you never use B-2 in a fuel cell, way to thick. A-2 is correct for fuel. Again go on Vans aircraft website to see what he uses on there homebuilts or at least make sure of compatability with mogas. FAA has several AD's out where MTBE has eaten up sealers hoses and other fuel system components which resulted in stopped engines.

 

Okay, I'll check with them. Thanks!

Excuse my terminology barrier for a second... when you say "mogas" are you referring to standard automotive fuel? Just haven't heard that before.

 

Sorry, thats what us propeller heads call autoMObile gas.

 

HAHA! I figured that's what you meant, but just wanted to make sure.

I just sent an email to Vans for some input and suggestions.

 

Given that you have the buck already, I think I would try this....take two steel tubes slightly longer than your part, put them parallel to each other about .090" to.125" apart and weld plates across the ends to keep them that way. Use spacers to keep them parallel when you tack them up. Put some legs on it so you have something like a double rail saw horse. Cut your sheet a few inches longer than your part. You Put the edge of the sheet just between the tubes and gently push it away from you a little bit. Slide the sheet in a little more into the tubes and push again repeat as necessary until it fits the buck. Centerline your part square to the long side and lay out for the baffles and end plates. Once your are happy with the shape and have the supports clecoed in mark the ends and trim the length. The length of your part may require another set or two of hands to push to keep it consistent. Take a piece of material and practice until you can make the curve match the buck.
I made an aluminum dash that was about 5 feet long this way. It took two tries to get it perfect and four guys pushing but it came out great. The longer the part the harder it is to do. BTW Gene Winfield taught this to me.

Craig

 

I thought of making one like this before, but out of steel. I was going to roll some beads on both sides of my straps towards each end to keep it centered. Does that make sense?

also, I just sent you the carbs and the kits... they're in two differnet packages, and your surprise is in there too, you'll know which one it is!

 

Now that's a different take on it. Essentially you're just breaking the material in an oval pattern until it matches the buck. Hadn't thought of doing it this way.

 

Awesome!! I'll tell my shipping guy that they're on the way. Should I be looking for USPS, UPS or FedEx? One of them isn't shaped like something obscene, is it??

 

usps.... is a summer sausage obscene??

 

Not if it will help me with my tank construction!

 

I'll leave that up to you????