Repairing a tear/ break in aluminum hull

Hello,

First off, I am not a boat repair guy per se but have been a welder for most of my life. Recently I put the word out that I will weld on aluminum boats after several friends brought me their projects.

I had a boat brought to me to repair and patch some cracked welds on the bottom of the hull. I did a little research on boat repairs and found that many suggested a patch / rivet approach to hull repairs and others, fiberglass.

My first inclination is to weld a patch over the cracked area and I have attached pictures of the job in question. I also attached the proposed patch design as I don’t want to weld at right angles to the direction of the hull metal and form stress points that will crack again. My drawing is not accurate. The actual crack runs totally at a 90 degree angle against the grain of the hull. My patch would have to be somewhat larger than the crack to allow for a gentle curve covering it.

In truck or equipment frame repair we always used patches with gentle angles and round ends to avoid sharp 90 degree stress points. I carry this philosophy to practically every cracked or broken metal joint I encounter be it a bike frame or truck frame.

However I am having second thoughts on whether or not welding is the best approach for this project because I am only equipped with a TIG and this calls for a lot of welding. I am afraid I may put too much heat into the hull and create warpage and more potential problems for myself, not to mention the client.

Anyone done large areas on a hull before? For a welded patch, what thickness metal would be desirable? The owner brought me some 3/16″ aluminum plate and while It provides nice strong material to patch with, it is not very flexible and I lean towards a 1/8″ plate instead.

I plan on grinding the old weld down so I can put a plate over it. Should I repair the cracks in the repaired weld? Or just by pass them and count on the patch to be sealed tight? I usually repair cracks and then plate them but thought I’d ask other people’s opinions on this.

Apparently the hull was cracked when the owner bought the boat and didn’t see that it had a large crack in it from hitting something hard. A boat repair yard did the welded repair and now it is being brought to me because that repair cracked. Besides not trusting them with the repair, they took three months to get it back to him and he wants it back quickly.

Anyone have any thoughts on this repair?

Thanks,

Tony

Hi As being a retired college welding teacher (33 yrs), I have several do’s and don’ts. 1. Is there any welding anywhere on that boat, if there is, then it should be ok to weld that hull.. 2. Being there is a crack next to that welded area, that indicates a NO WELD option. Alloys in the aluminum allow it to be heat treated, then tempered to increase the strength of the metal. Welding that heat treated aluminum destroys the alloys and heat treatment. In turn, that causes cracks a-long side the welds.. If there are any rivets anywhere on the boat, don’t weld, only patch with rivets.. Good luck

Those pictures show a pretty crappy weld job. Take the boat off the trailer, turn it upside down so you have easy access to the job. Grind the weld smooth then use a clean stainless steel bristle brush to clean the area. Very important to keep everything clean. Drill an 1/8″ hole 1/4″ past each end of the cracked weld. That will help keep the crack from traveling. Reweld using skip welds about one inch to one and a half in long. Let the naterial cool before each weld. Start at each end and work inward. Use your brush after each weld. Your tig, if big enough should work just fine for this.

If done right it won’t need a patch. But if you feel better by adding one, 1/8″ is still too thick unless it’s on a flat surface.

And I’ve welded on a lot of boats with rivets with no problems.

get a new boat?

Thanks for the replies. I am going to bow out of this job because I am not setup for maneuvering a boat in the manner you describe. I called the factory and they revealed the reason for the bad weld job. The boat has foam along the bottom. The stuff was melting right into the puddle and it was probably the job from hell.

The boat would have to have the stuff cleaned from around the welding area which involved major surgery removing all the stuff from inside, seats, trim, floor, etc.

This is not un-doable, just that I did not quote based on that amount of work.

Attached are a few more shots.

Thanks again,

Tony

The extra info and pics would have helped but I think you’re making the smart move. It would be very labor intensive and costly to weld it and be able to guarantee your work. Fiberglass patching would be my next move.

Big tube of silicone should cover it.

Hi again,

is such patching done from the inside or outside, or both? There is a welders forum that I use to communicate with other welders. One of them mentioned a material called 3M 5200. However after calling 3m and speaking with them, they say a marine epoxy is a better route as their product is not designed for large patches.

Thanks,

Tony

to repair an aluminum hull properly requires access to both sides to minimize the amount of filler required to acheive(sp?) a factory finish. I have been looking around at a couple shops to repair my boat and looked at a couple repairs in progress, pretty interesting all the work required for a good repair. There are probably easier ways to fix it if leaking is the only concern that are not as cosmetically appealing.

Well that is totally ugly. It really says something when the weld isn’t ground at all and yet it cracks down the middle even though it is much thicker than the hull.

I’ve never heard of fiberglass over aluminum.

remember the key here: It is full of foam in the hull. It was not cleared away. It inevitably got into the puddle and the welder probably had to go over it a dozen times to get it to burn away enough to close the weld. Hence and ugly weld. Compare to the two that have a nice bead, although cracked.

You are correct however if I read you right, that he should have cleaned it up and left it at least decent looking.

I already informed the owner that I cannot do this repair for the reasons I stated. However I would like to propose a non-welding solution. Do you have one in mind?

Thanks,

Tony