Cracked ribs in large boat questions

Xaero · Post by **Xaero** » 30 Dec 2021, 02:28

I am acquiring an aluminum 1999 SeaArk 2472MV. It started its life as a rear center console then remade into a forward console striper boat at some point in its life. It's had very large bait tanks in it for years and used on almost a daily basis. The entire insides are now ripped out leaving only the original front deck and all the ribs exposed. Most of the ribs are cracked right at the side bend.

How would someone repair the ribs? Clean the cracks as good as possible and directly weld them? Weld braces over the cracks? Maybe I should just scrap this boat as it is too old?

The hull seems solid enough so it may be worth building on. I don't plan on going to crazy with the build. Add flooring, a small console, and some seating on the sides. Maybe extend the front deck again. The deck extension was not built right and has been removed. The transom looks solid although it had an outboard over its limit on it for at least two years (150hp Mercury). I was on it while it was running and didn't see any bending, etc. I dont know if there is wood inside it.

lckstckn2smknbrls · Post by **lckstckn2smknbrls** » 30 Dec 2021, 06:53

I'd have a welder take a look at it.

turbotodd · Post by **turbotodd** » 30 Dec 2021, 08:54

without seeing them in person, be hard to say whether or not they can be welded.

Aluminum is funny. If it's not perfectly squeaky clean, it's very very hard to get it welded properly. And when it comes to boats, getting the material clean enough is where the challenge lies. This is especially true with TIG welding, which I would suggest. MIG can be used too and successfully, but even seasoned welders tend to skimp on the cleaning process, which directly affects the weld strength.

Weldorthemagnificent · Post by **Weldorthemagnificent** » 30 Dec 2021, 14:32

Pics would help, but here's what I know as a welder.. any material once stressed and broken and welded, is never as strong as it was. The parent material gets diluted with the filler alloys and also the heat stresses introduced into the heat affected zone, weaken what was once strong. Sounds like this boat was likely pounded over rough water on a regular basis.
This doesn't mean you should abandon the project, just examine your usage, how much you plan on putting into it and what your expectations are before proceeding. Gussets can likely be added to strengthen the broken ribs. Tying the sides together with decks will help with the flexing. Anything you can do to increase rigidity and decrease load will greatly help longevity. Don't cheap out on the structural stuff. Have a good welder look it over and give you an opinion

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Xaero · Post by **Xaero** » 30 Dec 2021, 20:10

Weldorthemagnificent wrote: ↑30 Dec 2021, 14:32 Pics would help, but here's what I know as a welder.. any material once stressed and broken and welded, is never as strong as it was. The parent material gets diluted with the filler alloys and also the heat stresses introduced into the heat affected zone, weaken what was once strong. Sounds like this boat was likely pounded over rough water on a regular basis.
This doesn't mean you should abandon the project, just examine your usage, how much you plan on putting into it and what your expectations are before proceeding. Gussets can likely be added to strengthen the broken ribs. Tying the sides together with decks will help with the flexing. Anything you can do to increase rigidity and decrease load will greatly help longevity. Don't cheap out on the structural stuff. Have a good welder look it over and give you an opinion

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Thanks for the info! I do need to get some pictures and talk to a welder I know. I know it was not pounded by waves and the previous owner did drive like a grandma most of the time. The bait tank and up to 6 passengers daily was the stress on it. I was told by a friend SeaArks crack like this a lot when a big bait tank is involved. I have not verified that statement with anyone else yet.

Xaero · Post by **Xaero** » 31 Dec 2021, 17:02

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Looks like they already started welding in some braces over the cracks. It’s holding water really good too haha!

Weldorthemagnificent · Post by **Weldorthemagnificent** » 31 Dec 2021, 19:56

Looks like a good start to cover the cracks but won't lend much strength to the corner. Suggest using side gussets like crudely doodled in my pic. On the upside, its wide open and easy to access. Cleaning all the areas with a grinder with a wire wheel/cup brush will save you a bit of time on the prep work. Maybe make a template for the gussets. A shop with a CNC plasma or better yet a water jet can cut them out. Gusset doesn't need 100% weld just where it's easy to reach. 5000 series aluminum if it's available, or 3000 series. Don't use 6061.

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Xaero · Post by **Xaero** » 01 Jan 2022, 18:19

Weldorthemagnificent wrote: ↑31 Dec 2021, 19:56 Looks like a good start to cover the cracks but won't lend much strength to the corner. Suggest using side gussets like crudely doodled in my pic. On the upside, its wide open and easy to access. Cleaning all the areas with a grinder with a wire wheel/cup brush will save you a bit of time on the prep work. Maybe make a template for the gussets. A shop with a CNC plasma or better yet a water jet can cut them out. Gusset doesn't need 100% weld just where it's easy to reach. 5000 series aluminum if it's available, or 3000 series. Don't use 6061.

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Thanks! I will look into the gussets. It's weird how memory works. I thought the boat would be a lot more loose than what it really is. It's a rock solid thick hull. I cant make the sides move at all or the transom.

Weldorthemagnificent · Post by **Weldorthemagnificent** » 01 Jan 2022, 18:24

That's a big boat, what a great blank canvas!

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Xaero · Post by **Xaero** » 19 Feb 2022, 12:43

Weldorthemagnificent wrote: ↑31 Dec 2021, 19:56 Looks like a good start to cover the cracks but won't lend much strength to the corner. Suggest using side gussets like crudely doodled in my pic. On the upside, its wide open and easy to access. Cleaning all the areas with a grinder with a wire wheel/cup brush will save you a bit of time on the prep work. Maybe make a template for the gussets. A shop with a CNC plasma or better yet a water jet can cut them out. Gusset doesn't need 100% weld just where it's easy to reach. 5000 series aluminum if it's available, or 3000 series. Don't use 6061.

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How about using rectangle pieces? We had no way to do an angle cut and the area isn’t flat. We had to bend the part and use a clamp to flatten it.

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Weldorthemagnificent · Post by **Weldorthemagnificent** » 19 Feb 2022, 17:38

Anything is better than nothing. The more material you can get alongside the better. The top strap will give lots of strength when the side wants to flex out, but not as much when it wants to flex inward.

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