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strength and feasability question on aluminum plate

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  • strength and feasability question on aluminum plate

    So I want to strengthen the transom on my boat...there are a few is welding or bolting a plate across the outside of the skin(.100") that is there now. I have a quote for 4 x 8 sheet of .250" thick 5052. that I could cut the transom out of... I don't need that large a piece but they only sell the whole sheet. I have a 49" square sheet of 5/16th" thick aluminum... I was wondering about cutting it and butt welding it to make a roughly 30" x 66" piece.

    then I would only have my labor and welding materials... I have a mig welder at home and a TIG welder at work.. I could use...

    feasible....??? ridiculous???....problematic???.... this plate will be tacked onto the outside of the skin now and will get the additional support of through bolts when I add a pad for the motor and a pad on the inside to help strengthen the transom even more...and to attach inside addition I have flotation pods that were welded to the transom, that I have cut off... I plan to recut them to give more clearance on the bottom to not drag when on plane..and to weld them to individual plates with a lip on each side that I can use to bolt to the whole transom assembly... this way if the pods need to be removed..i can just unbolt them.... so we are looking at roughly twelve 1/2"-13 ss through bolts.... 4 for the motor in the center, and four on each support will be spread out. the plate for each pod would also be 1/4" thick aluminum........I can afford the large 4 x8 sheet, but I still have a lot more items to replace on this boat rebuild....and need to try and use available stock and supplies when I can...

    is the butt weld a good idea or not....sandwiched between the boats transom and three separate 1/4" plates on the outside( one under the motor and two that are part of the pods)... then on the inside Ill have a continuous 1/4" thick plate that just covers the bolt pattern of the through bolts....


  • #2
    If you trust your welding skills then by all means weld the plate together. I would bevel the weld joint on both pcs. front & back so you will get 100% penetration. Sand it smooth where it needs to be & you should be good to go. Of course if you are not sure of your skills then that is a different story. I'm not saying the engineering is good as I don't know without seeing it but you seem to have it figured out.
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    • #3
      I enjoy butt welding, but hate the distortion. If the appearance is real important buy the sheet. It won't go to waste. If it were me, I'd be thinking of triangulating the bracing with something from the gunwales maybe a foot long if you can. I spend too much time thinking abought weight at the back of the boat. Getting to plane in a small outboard is a concern. From my house I can see 13 boats. At present I don't own a motor boat. My fiberglass Thundercraft died of a bad transom. I use other people's. If any boat owner objects to me using theirs, they can find other places to store them. I've given it thought.

      You haven't mentioned if your boat is made of aluminum, we don't know the construction, but to me, Your big plate sounds heavy.
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      • #4
        Need pics
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        • #5
          well, I found some aluminum plate on I wont be going the butt weld route...but Id think it would have held up fine strength wise....the question is if I could have had the patience to weld it a little at a time so it didn't warp....