What alloy are Magnum wings made from?

After our excursion in 30+ winds, & breaking an attachment stud, I also found a crack/break in one of the small support tubes.
The wings are "Magnum", off an '84 H18. They do not have the extra bracing strut.
Can anyone tell me definitively what alloy was used in these?

I can't say for certain, but I believe it to be tempered 6061 aluminum - either T4 or T6.

T6

Thanks.
I'm sourcing some 6061 T6 from Aircraft Spruce. When I get the break welded, I'm going to have them add the extra crossmember between the large & small tube.
Does anyone have the measurement of how far up from bottom the horizontal bar goes?
I was thinking of eyeballing it from some online photos, but I'm sure the design engineer placed it a station X for a good reason.

Note that when welding T6 aluminum, you remove the temper from the heat-affected zone of the weld - which reduces the strength by about half (in that area).

So what is a T6 temper? T6 tempering involves two steps—solution heat treating and aging.

Solution heat treatment is done by raising the alloy temperature to about 980 degrees F and holding it there for about an hour. The purpose of this is to dissolve all the alloying elements in a solid solution in the aluminum. Then it's quenched in water. The purpose of quenching isn't really to strengthen the alloy, although it does somewhat; it is to cool it rapidly enough to prevent the alloying elements from precipitating on cooling. This is called the T4 temper.

If you take this material and heat treat it at a temperature between 325 and 400 degrees F, the alloying elements begin to form ordered arrays of atoms in the aluminum matrix. These arrays are called GP zones, and they strengthen the aluminum considerably. This heat treatment is called aging, which results in material with a T6 temper.

Three commonly used time/temperature cycles are used for aging—one hour at 400 degrees F; five hours at 350 degrees F; and eight hours at 325 degrees F. All are equally effective.

Interesting. I knew that tempering aluminum was largely based on heating the material in an annealing oven, but I guess I assumed it was much more complicated than that. Matt, do you know if Hobie did this with most aluminum parts, or just some of them? I know the crossbar extrusions are tempered, as are the magnum wings and the seat of the SX wings, and probably the masts too, but I'm wondering about the legs on the SX wings. I have a set with some cracked welds where the strut was welded to the leg.

Cracks in wing parts....
Other than trying to sail, the biggest problem I have is folks who want to help with the haul out at the end of a sailing session.
I keep telling them, 'the wings were designed for compression, NOT for pulling the boat out of the water'.

We all know that there is a built-in conflict between making the wings both strong and light.
Tube welding is an art unto itself, and the results (after some time) are that the small legs crack.

The answer to get a really good MIG/TIG welding person, someone who understands temper, who can effect repairs and retain the optimum strength.

_________________
2015 H16, with spin,
SOLD 1989 Hobie SX18 Sail # 1947 "In Theory..."
'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'

[quote="MBounds"So what is a T6 temper? T6 tempering involves two steps—solution heat treating and aging..[/quote]

Yes, I did a bunch of research, so I could at least discuss it intelligently with the fabricating shop.
Practically, I don't think there is an economical way to re-temper/age such a large piece.
However, the aircraft home builders do repairs. By sourcing some of the certified fixes, it seems they insert a tube inside the break,(cut at 30*), and use rosette welds, and along the seams to obtain the original strength. They can also weld patches over the tube, if a smooth finish is not important.

John, Sabres, with regards to the welds cracking, that is almost a given with 6061 IF YOU TRY TO WELD AUTOGENOUSLY. You must use a filler wire, most commonly 4043. That dilutes the weld puddle & gives satisfactory results.
The other major thing is degreasing, use acetone or toluene, not alcohol.
I believe this tubing is anodized, & that is the 3rd major consideration. The anodizing MUST BE PHYSICALLY REMOVED, by sanding or grinding.
Also make sure your welder uses AC. The alternating current blast away any left over anodizing.
This site has some very good Intel

http://www.thefabricator.com/article/al ... s-for-gmaw

Here is some good info on welding 6061.

http://www.thefabricator.com/article/al ... s-aluminum

http://www.thefabricator.com/article/al ... inum-welds

http://www.thefabricator.com/article/al ... minum-gmaw

The fix proved to be quite simple, & concerns about strength loss are overrated.
First,find a shop that welds a lot of aluminum,they have the proper filler wire, & experience to do it right. I took mine to a place that builds aluminum trailers, & work boats up to 40' in length. He said they weld T6 every day, & the fix would be quite a bit stronger than original, by inserting a sleeve of either solid rod, or 1/8" wall thickness. By using a 4xxx or 5xxx series filler rod,(mandatory to use), it dilutes the weld puddle into an alloy that won't crack. In fact you cannot even buy 6061 filler.
Second, prep. If you attempt to just "melt" the ends together, you are setting yourself up for failure.
I purchased a 4" piece of T6 tubing for a couple of bucks, it is readily available in a diameter that matches the inside diameter of the support leg. The fit may be VERY tight, don't try to hammer it in with brute force, you will split the leg tube. I ended up using a hacksaw to cut a lengthwise slit in the patch tube, allowing it to be compressed slightly, using a vice.
There may also be weld puddle inside the original tube that you may need to dremel out in order to get the sleeve inside.
Grind off ALL the anodizing around where you will weld, both the sleeve & support tube. Grind the ends of the original tube back 1/16", in order to leave a small gap for weld penetration. Clean with acetone to remove all grease, the second biggest culprit in cracking.
Either bring the entire boat to the shop, so the wing can be properly aligned, or dry fit, then punch mark the pieces so the tube is orientated properly. In my case things were a tight fit, I cleaned the parts, then tapped them into place with the wing on the boat, then removed it for welding. Welding itself was a couple minute job.
He then ground/polished the weld to match the outside tube, & said I could either paint it to match, or just let it weather.
The entire job was $30.
One other small detail. The large rectangular tube is a sealed unit & there are no drain holes. The large support tube is sealed via the end cap. The small support tubes have a foam plug about 2" long, just above where the mounting pin goes. If you damage this plug be sure to replace it, otherwise you could fill the entire wing with water. The small tube inserts into the frame tube, right to where it "bottoms out", but it will not mate up close enough to be watertight.

Congratulations on your wing repair, glad to hear that it can be done without too much fretting about strength loss! Your idea of a supporting insert in the area of the weld is a great idea, both for added strength, and as a "backing bar" to weld against. This could serve as a useful future reference, which I hope never to need!