Crazy idea? Marrying stringers

Getnrdy

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My newly aquired 25' marathon has stringer rot from transom to just into aft cabin. I would like to cut the section thats rotted, replace it and "marry" it to a section for strength. Is this crazy or a sound idea? It is a 84 model
 

DeepBlue2010

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I am not sure what you mean by "marrying" them. So, replacing cutting and replacing the rotted section is clear enough. Now what is the marriage part means?
 

JASinIL2006

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Are you talking about sistering a piece of wood where the old stringer and the new one meet in a butt joint? That should work.
 

Pusher

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Or sandwiching the old and new end of stringers where they butt up to each other?
 

Ned L

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Maybe you are referring more to a "scarf joint" where you transition from the old stringer seamlessly to the new stringer in a way that maintains the strength and integrity?
Sure it can be done, no problem.
 

JASinIL2006

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Just to help, below are pictures of a scarf joint and a scab joint (where a piece of wood is sistered over the butt joint). Both can be very strong. The butt joint would probably be easier but is less attractive.
 

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gm280

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There are tons of ways to join two pieces of wood together to make a good solid stringer. Most anything that can be joint together that won't allow twisting will do for such things. Lap joints, scarf joints, or even a bevel cut joints will work pretty well. I would not use a butt joint without sistered pieces on each side to keep it from moving and cracking at the simple joint. But that is just me.
 

JASinIL2006

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T I would not use a butt joint without sistered pieces on each side to keep it from moving and cracking at the simple joint. But that is just me.

Why not? Scabbed joints can be incredibly strong. You see them all over the place... steel bridge construction, house framing... if you use the right material and correct fasteners, the joint can be as strong or stronger than the original material. Granted, the joints are not as pretty or elegant as scarf or lap joints, but for belwo decks, I don't think that would be a concern. Moreover, if the structure is being joined to existing structure, making a scarf or lap joint could be pretty tricky, especially if one end of the stringer is glassed to the boat.

Now, if you're talking about slapping a 2x4 across the joint and nailing it to the butted stringer pieces, I'd have to agree with you... but that would be a poor repair.
 

gm280

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Why not? Scabbed joints can be incredibly strong. You see them all over the place... steel bridge construction, house framing... if you use the right material and correct fasteners, the joint can be as strong or stronger than the original material. Granted, the joints are not as pretty or elegant as scarf or lap joints, but for belwo decks, I don't think that would be a concern. Moreover, if the structure is being joined to existing structure, making a scarf or lap joint could be pretty tricky, especially if one end of the stringer is glassed to the boat.

Now, if you're talking about slapping a 2x4 across the joint and nailing it to the butted stringer pieces, I'd have to agree with you... but that would be a poor repair.

JASinIL2006. Did you read what I posted? I basically stated that I WON'T use a butt joint. That is unless there are sistered pieces along both sides to make it a solid joint. I'm not sure what you are question me about? :noidea:
 

gm280

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My bad... I misread your post... my apologies! :sorry:


Not a problem at all. I figured it was a misread. I do lots of woodworking and I use a lot of different joints depending on what I am building. Butt joints are the worst without any other means of support. :peace:
 

Getnrdy

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Yes, thats what i mean exactly.
A butt joint with sisters.
Thanks, i figured stranger things had been done!
 

tpenfield

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Not all that crazy, but I would 'sister' the joint on both sides. . .

Here is what that would look like (pictures from my thread here on iBoats) , as I did that sort of thing on my 24 foot Cuddy, where the main stringers had only about 1 foot of rot in them and were fine the rest of the way forward. The trick may be to get the seam and glassing on both sides of the stringer.

Bad portion of stringer removed and Inside 'sister' board installed
IMG_0424.jpg

Inside glassing prep
IMG_0435.jpg


New portion of stringer installed and glassed on inside.
IMG_0438.jpg

Outside sister board and glassing
IMG_0441.jpg

Closing up the access hole and filling chamber with expanding foam.
IMG_0466.jpg

Post some pictures of what you got as that will help with responses and guidance along the way.
 

Pusher

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Love it when people post with great advice and supports before asking for pics šŸ˜Ž nicely done Tpenfield!
 
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