Stringer Replacement Stress Risers In But-Splice

[jlclar09]

All,
I have a 1984 Sea Ray Seville Cuddy that I am replacing the stringers on. I have finally removed all of the rot over the last 3 years and I ma preparing to start re-glassing in new ones. I removed all of the stringers up to the cuddy cabin portion, where the wood was dry and solid. I am planning on splicing in new stringers from there back to the transom. The old stringers were made from 1/2" plywood. I have read that everyone uses 3/4" plywood for stringer replacement. Is it ok to use the same 1/2" size wood. I am worried that if I use 3/4" but-spliced to the existing 1/2" it might form a stress riser and cause it to fail due to the transition from 3/4 to 1/2" Can anyone weigh in on this with their opinion from experience? I am planning on using the marine grade plywood from Menards as they are the only place I know of who carry this material in stock.
Thanks,
John

 

[jigngrub]

Do you have any pics of your work so far?

Do you have the decking/floor removed in the cuddy so you can install a long enough splice/scab/splint?

Using 1/2" will be ok, it's just harder to work with, and 3/4" will be fine as well. just flush one side of the 3/4" with the existing stringer and install a good sized (length) scab on the flush side. I suggest an 8' long scab with 4' lap on each side of the splice joint.

 

[tpenfield]

From my experience, I have replaced 1/2" stringer material with 1/2" (not 3/4"). So, if that is what was there, then there should be no issues.

Additionally, there is often a bulkhead at the cuddy which the main stringers would join to. So, even if you did a different thickness of wood for the main stringers, I would think the bulkhead would be the place to change thickness.

 

[Woodonglass]

Ext grade Ply will work just fine. You can use the MG if you want but just saying it's NOT required. Once the Ext. Grade is properly encapsulated in resin and glass it will last for decades!!! I'd recommend using 3/4" and using Thickened resin, What we call "Peanut Butter", to make a smooth transition @ the Butt Joint. Again once it's glassed in it will be more than strong enuf. The fiberglass biaxial cloth is very strong. I've attached a drawing to show how I'd do it. Hope it helps. This is just how I'd do it and have seen others do it in the past with great results.

 

[jlclar09]

Thanks for the replys!!!! No I don't have any photos on me a the moment. Yes I do have the decking removed about 12 inches further than the where I stopped cutting out the rot. The old stringers were only glassed on one side and only about 3" up the side of the stringers. Is this normal? With the glass only going up about 3" up were the stringers really providing much strength or was it the hull that provided the strength and the stringers just support the floor? I was planning on encapsulating the stringers entirely. I have 1708 Biax tape I bought about 2 years ago that I will be using to glass the stringers in place.

 

[Woodonglass]

This link has a lot of good information on how to do your stringers. It's how I recommend doing it. Fabricating Decks, Stringers, and Transoms

 

[Rickmerrill]

I won't speculate on the purpose of that stringer "design" structurally but if you're going to all the effort I think it makes a lot of sense to fully encapsulate all wood for longevity and a little pride in workmanship.