Aluminum trailer I beam fracture

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paula_ke
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Aluminum trailer I beam fracture

Post by paula_ke » Fri May 11, 2018 1:35 pm

In the process of upgrading my dual axle fenders we discovered fractures in the aluminum I beam. One in in the I beam bend, the other, just aft of the rear axle. Fortunately, the shop doing the fender upgrade spotted the weak points and will weld them up. Check your I beams on aluminum trailers!

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Re: Aluminum trailer I beam fracture

Post by sailboatmike » Fri May 11, 2018 4:34 pm

That is the problem with Aluminium, unlike steel it does not take well to the constant flexing a trailer gets, even the best Aluminium suffers from this issue, just look at aircraft they are constantly being inspected for stress fractures.

I hope the trailer shop does the job correctly, I believe the correct procedure is to find the end of the crack and drill a hole in it before attempting a repair or the stress crack will just continue even if welded up. Information taken from watching many Air Crash Investigation Docos where repairs made incorrectly have caused the crack to continue even after repairs have been made.

Not 100% sure that this is the correct procedure but best to check rather than get a false sense of security.

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Re: Aluminum trailer I beam fracture

Post by Catigale » Fri May 11, 2018 8:16 pm

Paula ...How old and what is the history on the trailer please?

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Re: Aluminum trailer I beam fracture

Post by paula_ke » Fri May 11, 2018 11:34 pm

This is a 2011 trailer. PO used it very little. Basically a boat yard trailer. Plates had 2015 stickers. When I bought the boat in fall 2017 the trailer had the original tires with no wear (I immediately replaced them due to the date code). I did not see anything on original inspection and I looked pretty close.

I added the second axle in November 2017 and took the boat/trailer to Baja Mexico. Baja roads are hard on anything. 3800 mile round trip and I was ready for new/real fenders rather than the quick fender installation that I put on after installing the axle.

The fracture forward of the front axle sort of makes sense. The I beam is bent there and probably was under stress at manufacturing. The rear fracture is confusing. No where near the stresses compared to two bunks on the two axles forward of that fracture.

More later, after I get the trailer from under the boat. Currently building an aft cradle and will block the rest while moving the trailer.

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:macm:

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Re: Aluminum trailer I beam fracture

Post by paula_ke » Sat May 19, 2018 8:38 pm

Update: There were a total of 3 fractures. All were located where the web (vertical) meets the lower flange (horizontal). The reason they failed at the particular locations was due to the way I had cantilevered the aluminum fenders. I had bolted aluminum square tubing to the lower flange and bolted the fender to the square tubing. The result was a cantilevered support for the aluminum fender that was only attached to the lower flange. After 4,000 miles of bouncing around the webbing/lower flange connection began to fail right where i had mounted the square tubing.

All three locations have been professionally welded on both sides of the webbing. New fenders have been installed with full frame U bolts clamping the entire I beam. No holes. Stainless angle iron was used to support the fenders and the angle iron is located on top of the I beam allowing the fender to be supported much higher. This has eliminated the fender vibration/bouncing.

Anybody who has cantilevered mods to the trailer that are bolted to just the bottom or top flange of the I beam should be aware of potential web to flange fractures.

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Re: Aluminum trailer I beam fracture

Post by NiceAft » Sun May 20, 2018 8:45 am

Descriptive pictures would be nice.

Ray

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paula_ke
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Re: Aluminum trailer I beam fracture

Post by paula_ke » Sun May 20, 2018 7:07 pm

The pictures in the first post show the fracture on the I beam where the web meets the lower flange. Click for a larger picture. You can also see the square aluminum tubing that I used to support the old fenders.

Here are pictures of the repairs and the new fenders:
Image

Notice that the angle iron supporting the fender is now mounted on top of the I beam and U bolted around the I beam. This allows the fender to be supported at a higher location reducing the motion during vibration (hitting bumps)

And another
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Re: Aluminum trailer I beam fracture

Post by K9Kampers » Sun May 20, 2018 7:17 pm

What steps have you taken to insulate the dissimilar metals from producing galvanic corrosion?

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Re: Aluminum trailer I beam fracture

Post by paula_ke » Sun May 20, 2018 7:38 pm

No more than the steel axles and numerous stainless steel bolts used throughout the trailer. I'm not sure what you are getting at? I always wash my trailer with fresh water after a launch and recovery, including the all important brake disks. I also keep my trailer tongue low to the ground during storage so any accumulating water will roll out of the tongue. I also check to be sure my trailer jack is well greased.

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Re: Aluminum trailer I beam fracture

Post by Gazmn » Mon May 21, 2018 12:16 am

Good info!
Succint & informative
Thanks Cap’n :)

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Re: Aluminum trailer I beam fracture

Post by Gazmn » Mon May 21, 2018 12:30 am

I’m glad I have a new aluminum trailer. But I am not happy with my fender install
https://flic.kr/p/26gvajU

I don’t like my tire clearance & will look to address this after 2018 Season splash 8)

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Re: Aluminum trailer I beam fracture

Post by sailboatmike » Mon May 21, 2018 2:19 am

Gazmn wrote:I’m glad I have a new aluminum trailer. But I am not happy with my fender install
https://flic.kr/p/26gvajU

I don’t like my tire clearance & will look to address this after 2018 Season splash 8)
What tyre clearances?? Looks like the suspension has given way on the trailer

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Re: Aluminum trailer I beam fracture

Post by Neo » Fri Jun 14, 2019 8:13 pm

Sorry to bring back an old thread but when I look at those cracks/weld lines and I think two things.....
1. The repair wells are contaminated and not worth having. No stronger than the cracks!
2. Those cracks have been caused by over tightening the mudguard brackets... The axle mounting points are too far from the cracks. If it was road/axle stress it would have most likely cracked at the top of the web first.

That's my 2 cents worth :D

All the best.
Neo

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