Weld failed on toon? #almostsank

rlavalla

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Hey folks, wondering everyone’s thoughts on this. Already submitted the insurance claim but we hit an under water tree and it popped the end of the toon mostly off right along the weld. Looks like someone took a giant can opener to it lol. Is this a common thing for Benningtons or a failure specific to our boat? The guy at the dealership had never seen this very specific thing happen before. If the weld was good it should have either just dented or torn the metal around the weld, not the weld itself.

Very, very glad we decided to go back to our marina right after it happened. The only reason we did was the depth finder stopped working after that 2 minute drive the end was sinking as we pulled it in and raised it up on the lift. Wild. Also attached the pic of the inside of the toon in case anyone has ever wondered what it looks like…
 

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Vikingstaff

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Our neighbor has a Manitou tritoon. He hit a log a few years ago, and did the the same thing. More or less popped most of the backend cap of his starboard pontoon out like yours along the weld. Common? No. Other than my neighbor, I have not seen or heard of something similar before. Probably just a weird strike at just the wrong spot, and it then created some sort of pressure and pop along that weld.

I don’t think your issue is the weld. I think your issue is hitting a submerged tree. Don’t do that. ;) :oops:

That said, glad you made it back dockside okay. Rough ending to a boating day.
 
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DVW

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Thank you for sharing this significant event. Aluminum gets a good share of its strength from work hardening. Unfortunately this strength is lost when it is brought back to its molten state. Aluminum that melted during welding is the weakest aluminum. Often times this is the melted sheet aluminum but the melted filler material is also weak.
 

Potomacbassin’

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My guess is the weld on the end cap is not done in such a manner to withstand pressure inside the tube, but rather resist external pressure. I've read if you put more than low-single digit air pressure in the tube it could pop a weld.

Tree strike created a spike in internal pressure and thar she blows.

Glad you made it OK.

Edit - looking at the pictures again it looks like the cap just got ripped off. A tiny weld isn't going to resist that kind of force.
 
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Jack M

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You hit a submerged tree and believe its a bad weld ?
Hey folks, wondering everyone’s thoughts on this. Already submitted the insurance claim but we hit an under water tree and it popped the end of the toon mostly off right along the weld. Looks like someone took a giant can opener to it lol. Is this a common thing for Benningtons or a failure specific to our boat? The guy at the dealership had never seen this very specific thing happen before. If the weld was good it should have either just dented or torn the metal around the weld, not the weld itself.

Very, very glad we decided to go back to our marina right after it happened. The only reason we did was the depth finder stopped working after that 2 minute drive the end was sinking as we pulled it in and raised it up on the lift. Wild. Also attached the pic of the inside of the toon in case anyone has ever wondered what it looks like…
 

rlavalla

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My guess is the weld on the end cap is not done in such a manner to withstand pressure inside the tube, but rather resist external pressure. I've read if you put more than low-single digit air pressure in the tube it could pop a weld.

Tree strike created a spike in internal pressure and thar she blows.

Glad you made it OK.

Edit - looking at the pictures again it looks like the cap just got ripped off. A tiny weld isn't going to resist that kind of force.
That’s interesting with the internal pressure, good point!
 

rlavalla

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You hit a submerged tree and believe its a bad weld ?
Lol we were definitely at fault. Not arguing that. The water was lower than normal and we should have gone a lot slower even tho it was an area we’ve been through a million times. But yes, the metal should tear, not the weld. The weld is *always* supposed to be stronger than the surrounding metal. Interesting comment above though with the internal pressure, that could cause a weld to pop and makes sense. But the weld failing is the difference between a patch/immediate fix and an insurance claim/2-3 month wait for a new toon. ☹️ oh well. It happens!
 

DVW

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Lol we were definitely at fault… But yes, the metal should tear, not the weld. The weld is *always* supposed to be stronger than the surrounding metal. Interesting comment above though with the internal pressure, that could cause a weld to pop and makes sense…
As I stated in a reply above the weld or the base material right next to the weld is always weaker than the surrounding sheet aluminum. Good designers assume this to be true and take this in to consideration. With regard to internal pressure causing failure. The tubes are vented but if they where not they would fail with hoop stress before the end caps would blow off. This would occur well above one psi.
 

Vikingstaff

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An aluminum welder will still be able to weld it. Should not need a replacement pontoon. The neighbor I mentioned above with the Manitou that had a similar situation happen was able to have the local guy up here weld it back together and they were back on the water in no time.
 

LaurencetheAdventurer

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Thank you for sharing with the pictures. Obviously zero risk of sinking with the baffle - great to actually see inside!
 

BigKahuna

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Nope not specific to Bennington's! Regardless of what brand you were driving that day the same thing probably would have happened! You hit it just right! Looks like there is other damage/denting to the pontoon too. You might as well just replace the whole thing! Where do you boat?!?
 
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