Stress cracks in aluminium hull (Tracker)

[the force]

Gents, does anyone have experience repairing small stress cracks in a aluminium hull? This is on a 2005 Tracker pro-guide WT, the hull is relatively thin aluminium. It appears the cracks are right where the stringers are welded on the interior. There are three spots, two on one stringer and one on the next one up. Boat takes on a bit of water but not really a significant amount, maybe a gallon all day. The bilge can handle it fine but I would like to fix it if possible. I have the decks ripped out right now to be re-done. Problem is access from the inside is poor and it would be quite difficult to weld in a plate due to the stringers. Any ideas with out putting me into bankruptcy? Thanks for any suggestions. I considered epoxy but would rather something more permanent. See pics...

 

[the force]

Second pic showing 2 of 3 cracks.

 

[fhhuber]

General stress cracks in aluminum:

Stop drill the ends of the cracks. Then you have to rivet on reinforcing plates or get it welded.

If you don't stop drill the crack ends they will continue to grow . They can start back up even if welded, if you don't drill the ends of the cracks.

 

[classiccat]

+1 on drilling crack-stops.

I'm also a fan of external aluminum patches (at least 0.060" thick), back-buttered with 3M-5200 and riveted in place. It can be a little tricky if the hull is not flat where these occur. If you're using 5052 aluminum patches, you can heat it with a propane torch (tip: apply soap to 1 side, heat the opposite side until it burns) to make it more malleable then, using a dead blow hammer, get the patch to conform to the hull; be careful though...you don't want the cracks to propagate more.

I will say that these bad boys are a bit different than us riveted-hull guys are accustomed to dealing with...these things really spider-out :

 

[the force]

Thanks guys, I wouldn't have thought to stop drill them. How water tight is a riveted patch with 5200? Totally or may always leak a bit? I can rivet, but don't weld. Could pay a welding shop if that would be better in the long term.

 

[Rick Stephens]

I would not be afraid to get a shop with a guy knows a tig welder and let him weld her up. Thickness is not nearly as big a deal with a tig and it can be made as good or better than new. I'd do it myself in a heartbeat. Not a big deal as long as you can get the areas to be welded clean and free of meltable stuff on the other side.

Rick

 

[the force]

Yeah going to take a look around town and see what I can find for welders. If anyone knows a guy in Kamloops BC area let me know. As for meltable stuff there is floatation foam in one area...does that all need to be cut out, and if so does it need to be replaced? Not likely a lot will need to be removed. Thanks again for the expertise.

 

[Scott Danforth]

your tracker was welded from the factory. just get the cracks welded up.

check with your local radiator shop. my guy welds aluminum boats all the time for $35 per hour

typical weld would be to j-groove the crack and weld. then hot-flow the weld

5052 is soft, no need to heat with a torch to bend.

 

[classiccat]

5052 is soft, no need to heat with a torch to bend.

sure you can bend it without heating... but to get it to conform in a controlled fashion without collateral damage you'll want to anneal it. 5052 will work harden.

 

[classiccat]

Thanks guys, I wouldn't have thought to stop drill them. How water tight is a riveted patch with 5200? Totally or may always leak a bit? I can rivet, but don't weld. Could pay a welding shop if that would be better in the long term.

Alot of that depends on execution there force. If you do decide to go the patch route, Once you get the patch in the shape that you want it, you'll want the 5200 to have something to grab. Sand the surfaces and clean them with acetone..and try to avoid touching them. You could take it a step further and do a chromate conversion (Alodine) and/or spray with Zinc chromate.

Another tip for forming your patches is to drill/tap some some 8/32 screws into the hull skin while you form the patch...helps keep it in place while you shape it...& drill the holes for your rivets. Once you get the rivet holes drilled, insert a few clecos, then drill-out the 8/32 holes as well.

I don't think of them as band-aids...more like battle scars

 

[sutor623]

Classic cat those patches look legit brother!

 

[the force]

Real nice looking classic cat! I think I'll go the welded route this time Though do have a little tinny that could use some riveting. Any specific recommendation for rivets or just closed end aluminium?
As for the welding, is it an absolute that foam must be removed from the inside contact area if welding from the outside of the hull to prevent weld contamination or fire? Or would it just melt a bit? The one spot is real tight. Thanks again.

 

[classiccat]

Real nice looking classic cat! I think I'll go the welded route this time Though do have a little tinny that could use some riveting. Any specific recommendation for rivets or just closed end aluminium?
As for the welding, is it an absolute that foam must be removed from the inside contact area if welding from the outside of the hull to prevent weld contamination or fire? Or would it just melt a bit? The one spot is real tight. Thanks again.

thank you force! On our old boats made with 5052, I've heard horror stories of guys chasing their tails using welds to fix cracks. Maybe a different grade of aluminum intended for welding (6061?..I'm sure someone here would know) was used on that Tracker of yours. If it does crack again, you know what to try next

I would definitely clear out everything behind that weld...fire hazard and it may contaminate the weld (sorry; re-read your post...this is exactly what you were concerned with).

On your other project, you should kick-off another thread! I'd try to use solid rivets if you have access to both sides of the hull. Closed-end blinds (aluminum with aluminum mandrel) simply can't complete with strength & long-term stability of a solid. A mandrel flares-out some thin aluminum to bind the pieces together and hold itself in place (temporary fix IMHO). The stem of a solid rivet completely fills the hole with solid aluminum and pulls the work pieces together with the head & bucktail; Permanent fix if done correctly...and they can be rebucked if they do work loose after a few decades.

 

[Grandad]

I'm thinking that the original material could not take the use it was given, either because of under-engineered construction or age fatigue or a combination of factors. Somehow, just welding, although that seems like an adequate fix, can't give you as good as the original construction that eventually failed. I'd suggest some additional support such as a strengthening patch, inside or out, welded or riveted, would be a good investment while you're doing it. - Grandad

 

[the force]

Hmmm, it is never that easy is it. I do agree that it was likely under engineered and have heard of other trackers with similar cracking. Here are a few more pictures as the location is not great. I still need to fill with water and see if there are any other leaks but it appears that 2 of the three cracks are on the left side of the plate welded across the bottom V (red circle), which of course is filled with foam and would be a big job to remove (hence leaning towards welding from the exterior).

As for riveting, I am assuming a patch inside and outside is best, but if a guy only has access to the exterior can you just rivet from the outside (assuming there is enough interior clearance of the rivet head)? I've never used closed end rivets, not sure if there is any difference for installation?

 

[sutor623]

Yea, unfortunately we call 'em Crackers around here.

 

[Watermann]

Hmmm, it is never that easy is it. I do agree that it was likely under engineered and have heard of other trackers with similar cracking. Here are a few more pictures as the location is not great. I still need to fill with water and see if there are any other leaks but it appears that 2 of the three cracks are on the left side of the plate welded across the bottom V (red circle), which of course is filled with foam and would be a big job to remove (hence leaning towards welding from the exterior).

As for riveting, I am assuming a patch inside and outside is best, but if a guy only has access to the exterior can you just rivet from the outside (assuming there is enough interior clearance of the rivet head)? I've never used closed end rivets, not sure if there is any difference for installation?

I would say the boat needs some more structure added to it, weld one spider crack and not long more will appear elsewhere. Have you found if anyone has tried to add structure to the boat to stop this? Otherwise spot welding and patching will just be a bandaid, some thought should be put into the boat and what it needs to stop this.

A 2005 boat should have decades of life before needing these sorts of repairs. I wonder if tracker has any suggestion on how to go about restructuring their boat?

 

[64osby]

^^^ I think Tracker would rather have you buy a new hull that has a lifetime structural warranty.

I say weld the cracks. Removal of the foam from the back side would be advised. Any contamination can / will cause an issue with the quality of the weld.

 

[Rick Stephens]

I say weld the cracks. Removal of the foam from the back side would be advised. Any contamination can / will cause an issue with the quality of the weld.

Have to agree. Aluminum gets hot over a wider area than steel when welding. And aluminum welds fair poorly with contaminants present. Hence some will choose to rivet when it is too difficult to get the foam out from behind. I'd bet poly foam burns nice.

Rick

 

[the force]

No Title

Good news, all the cracked areas were easy to expose. Bad news- upon further inspection and through some internet searching it does look like there are some structural issues. Cracks are at the front end of the longitudinal stringers, likely one of the areas that experiences the hardest impact from waves and also where the weight of the livewell and consoles bears down. The biggest cracks are on the port side, though there are some very small weepers on the starboard side as well. Looking at the tracker website it looks like they still use the same, or very similar structure.

Plan is to consult a couple welding shops Monday but if there is anyone on here that has experience with these trackers, or knows anything about adding structural support I would appreciate some opinions! On one hand I am thinking that riveting plates on the exterior side of these welds would help, though I would prefer to keep the cleaner look of welding and adding interior support (that said cost and value/durability are important as repair funds are limited).