After our excursion in 30+ winds, & breaking an attachment stud, I also found a crack in one of the suport tubes.
The wings are "Magnum", off an H18. They do not have the extra bracing strut.
I think I'm going to track down a welder with experience in welding small aircraft frames.
Can anyone tell me definitively what alloy was used in these?

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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after a little research i'm guessing they are 6061 but a machine/welding shop should be able to verify that

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Mike Conway
H16
Hilton, NY
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Almost certainly 6061 alloy. You would probably need to contact Matt Miller at Hobie for absolute confirmation. But Hobie tends to use 6061-T6 for all their extrusions and that tends to be the standard in the marine industry.

sm

It is almost certainly 6061-T# of some sort. The # refers to the temper applied to the metal and for 6061 has a great deal to do with how flexible it is. A higher temper results in a stiffer part, but it also makes it more crack prone. T4 is what you would expect to see in masts and marine fittings, but you could also get see T1 and up to T6 depending on the part.

It could also be 6063 but that is normally used more for high detail extrusions and not for fabrication.

Quote

Almost certainly 6061 alloy. You would probably need to contact Matt Miller at Hobie for absolute confirmation. But Hobie tends to use 6061-T6 for all their extrusions and that tends to be the standard in the marine industry.

Thanks. I was over in China, & could not set up an account on the Hobie forum. The Great Chinese Firewall blocks Google,(along with a zillion other sites), & it is surprising how many sites use some sort of Google bit, such as Google analytics etc.
Got the account setup & posted the query.
A friend who was visiting, (flight engineer, AME), on a Lockheed Hercules, said 5000 & 7000 series were common on large transport aircraft, but a bit of research seems to confirm the popularity of the 6061 for smaller applications.
Welding seems to differ between the alloys, so I'm trying to ascertain which one it is. I brought it to one welding shop that does aluminum, he suggested an internal sleeve,(looks better than external patch), for "something to burn into". He also said he would prefer to have the wing on the boat, in order to tack it exactly. Otherwise, 1/16" off could translate into an inch at the other end.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

Not sure how you would get a sleeve inside the main body tube to back up the weld since the body tubes are bent. I would just have him weld up the crack and then weld on an additional support tube that goes from near the bottom of the existing support tube back to the body tube. This would triangulate all the tubes and make it super strong, which is what Hobie ultimately ended up doing. And yes, you would definitely want to bring the boat because if the weld is off, there's very little in the way of adjustment you can make in positioning the wings before you would need to have him grind off the tubes and start over. At the very least, bring the "good" wing with you for reference.

If you're really worried about matching the existing alloy, you will need to contact mmiller or post over on the Hobie forum, which he checks regularly. Otherwise, I think 6061 is your safest bet.

sm

The tube that broke was the small straight tube, not the large one that holds the tramp.
I think I will get an extra tube installed at the time.



Edited by Edchris177 on Sep 09, 2016 - 08:54 PM.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--