Cracks in Aluminum Hull

[Backslider]

I leak tested my boat today and found two cracks in the aluminum hull. Can these be fixed with a with Gluvit or is there a way to fix them by welding, patching,...?

Thanks.

 

[Bob_VT]

Re: Cracks in Aluminum Hull

Welding is good but really only to stop the cracks from getting longer.

Have to prevent the cracks from growing and there are a few methods. Drilling a small hole at the end of each crack and installing a pop rivet to fill the hole and then sealing the entire area with a few coats of gluvit or even jb weld.

3m5200 will seal that too but once again..... stop the spreading.

A welder with a light touch and steady hand can do most of the crack but sealing will still be needed.

 

[Backslider]

Re: Cracks in Aluminum Hull

Do you think these can be fixed without welding? With just stop-drilling the cracks, pop riviting the ends, and sealing with Gluvit or 5200?

 

[Bob_VT]

Re: Cracks in Aluminum Hull

Yes, if you stop the spreading, apply a light coat of jb weld then seal it up with 5200 or gluvit. It should hold fine.

 

[Grandad]

Re: Cracks in Aluminum Hull

Hi Backslider,
The cracks are caused by metal fatigue from constant flexing. Most times, the cracks will appear relative to where support such as a rib ends. Any point where the structure changes in strength becomes a "stress riser" point where stresses become concentrated. The appearance of a crack tells you that there's currently not enough support to extend the life of your vessel any further. As Bob noted, drilling a round hole at the end of each crack will stop the crack from extending further, but only temporarily. If you don't fix the root cause of the cracking, your repairs can't last. If the original hull couldn't take the stress, your repair has to be stronger than the original hull. In my opinion, you'll need to remove some rivets and apply a sheet aluminum patch. Sandwich the repair with 3M 5200 to exclude the possibility of trapping water between the layers and re-rivet. - Grandad

 

[jigngrub]

Re: Cracks in Aluminum Hull

Hey Slider, is this the 17' back troller you've been restoring?

Is that the inside or outside of the boat in the pics?

I agree with the above post on patching, it'll reinforced that area.

Member efdog did a good job patching his boat in this thread.
http://forums.iboats.com/showthread.php?t=536250&highlight=efdog

 

[Backslider]

Re: Cracks in Aluminum Hull

Hey Grandad,
You're right about the location of the cracks. They're at the ends of two ribs. Three of the ribs are cracked and are being braced and welded today. I'll stop drill the cracks, remove the rivets from the rib ends, slide a 6" x 6" aluminum sheet between the rib end and the hull (w/3M 5200 sandwiched beween), and rivet the patch in place. Do you think the crack will need welding, too?

 

[Teamster]

Re: Cracks in Aluminum Hull

If I was already having things welded and braced I would also weld the cracks,...Along with stop drilling and patching etc,...

 

[jigngrub]

Re: Cracks in Aluminum Hull

I'm not grandad, but you should be good to go with just the patches and no welding.

 

[Backslider]

Re: Cracks in Aluminum Hull

Yes, this is the same boat. The photos of the cracks are from the outside of the hull. Thanks for the link. My problems don't seem quite so bad now

 

[Grandad]

Re: Cracks in Aluminum Hull

Hey Grandad,
Do you think the crack will need welding, too?

I agree with both jigngrub and Teamster. With the patch you propose, it probably wouldn't be necessary to weld the cracks, but if you've got confidence in the welder and he's already doing some welding, why not weld the cracks before you patch. You'll still need to patch though where the structure has been compromised. - Grandad