Stringer Repair Starts This Weekend - Help Needed

[rpdwyer]

Stringer Repair

I received a quote from my marina to repair the 4 stringers in my boat (1997 Larson Cabrio 310) which includes entirely removing and replacing the two inner mount mount stringers that run from the transom to a bulkhead around the gas tank and cutting out a section of outer motor mount stringers where the engine bolts down to them. The forward bulkhead which is two pieces of marine ply will also be removed and rebuilt since the bond between the two pieces of plywood have come apart. They wanted 4K+. That's out of my price range so I will likely try to do this myself using the WestSystem along with the WestSystem literature on how to repair boat stringers (as well as some YouTube videos).

This weekend I want to start the work and would like to get the collective wisdom of this board to confirm I'm doing this correctly. I intend to remove and replace one stringer at a time so as to mitigate any warping or deflection. The work for each stringer will be done in 3 phases: removal, prepping for new stringer and installing the new stringer. My questions below are for the first phase. Here goes:

1 - I will measure the existing inside stringers with the motor mount tabs for all dimensions so I have numbers to make my new ones from.

2 - I will measure the location of the stringer from all sides so it is clear where the new stringer will be positioned.

3 - I will use a sawzall with a long bi-metal blade to cut the inner motor mount tabbed stringer from the transom and from the bulk head.

4 - I will use a sawzall to cut along the bottom of the stringer for the entire length and remove the glass and wood stringer from the bilge are.

5 - I will use a die grinder and belt sander to grind down any raised remaining pieces of the old stringer to create a relatively flat and smooth surface for the new stringer.

Is the above logic correct for the removal of the tabbed motor mount stringers? Anything I forget or am overlooking? Can I get away with keeping the forward bulkhead as structurally the two pieces of plywood it is made from appear to be in very good condition… they just appear to have separated from each other where they were laminated together. Can I pour an epoxy between them and clamp them back together to rebond them together as opposed to actually remove the bulkhead?

Thanks,

--Rick

 

[Canracer]

Is the cockpit already removed? I'd say that would be the first step. Got a picture of the project?

Maybe you have access to the stringers and don't need to do that type of demo.

Is this the boat?

 

[rpdwyer]

Yes, cockpit and engines are out.
The mount mounts are cracked badly and drilling small holes in the stringers and knocking them shows them to be pretty wet.

Thats the same year, make and model of my boat.

Posted images a while back in a different thread... here's the link to that thread:


http://www.boatdesign.net/forums/boat-design/motor-mount-stringer-cracks-how-repair-49245.html

 

[Canracer]

You will need epoxy, glass, and new core material. Don't even think about using polyester. The only way to make these repairs is with epoxy. You can get a great price by ordering on line.

Maybe one of the other forum members can give you a good idea about how much you will need.

If you have 4 stringers to replace, I will just throw out a guess and say you'll want 4 gallons of epoxy.

 

[Canracer]

You probably already know about the epoxy thing.

 

[rpdwyer]

Thanks for the replies so far... but this weekend I will only be removing the one stringer (I want to avoid any hull deflection). Next weekend will be building and prepping the area and the weekend after, actually glassing them in. So is the method I described above for removing the best way to remove the stringers?

Can the bulkhead be reused and just epoxy the two pieces back together?

 

[Canracer]

I think it's a good idea to do one stringer at a time. If your transom and bulkheads are dry, I don't see why you would need to replace them.

Post a few pictures of the stringers, the bulkheads and the connection point at the transom. With pictures, it's easier to understand the project.

I can imagine that a SawsAll would be tough to work with in tight spaces. The die grinder or an angle grinder, with cutting wheels, would definitely be needed.

 

[rpdwyer]

Well, 2 of the 4 stringers are out (undetermined yet the condition of the other 2) and I have to say I was quite disappointed in what I found when I removed them. First, wet is an understatement...they were absolutely soaking wet and had and active channel of water below them. Why? Because as far as I could tell, Larson never sealed the base of the limber holes and water easily made it's way along the base of the stringer.

Also, I did not any see real evidence the wood portion of the stringers were epoxied to the hull except on the outside edges. It's almost like they placed it on the hull and then just ran a bead along side the outside edge. The stringers themselves were 5 sheets of marine ply STAPLED together...no epoxy or resin of any sort was used to adhere them together which is why the moisture had no problem moving up the wood.

I used a four inch angle grinder to cut along the bottom edges through the glass and at the point where it contacted the transom and forward bulk head. I would use a sawzall to cut the stringer into 1 foot sections and then hammer it on the side until it broke free from the epoxy at the edges. When i picked up the section that I just removed, it was extremely heavy from being saturated and water would drip from the wood freely.

I will say the glass was very thick and very strong. The stringers were not moving until the glass was off. I've done very little with glass but the strength of this stuff in a 18 year old boat really makes me realize how strong this stuff could be.

Yet with all this water I can't really say I came across much rot. The wood was a bit punky but I was expecting mush... which was certainly not the case.

So next I will fabricate some new stringers from marine ply. I will also remove the forward bulk head as it is clearly wet as well. The transom?...where the stringer was against it at the top, there's glass and the wood looks good. But at the point at the bottom where the stringer come from, I can see a 1 inch section that appears to be bare wood and it is wet. I will put a moisture meter on it soon to see how far the moisture has moved but when you tap it out, it sounds solid through out. Not sure how to proceed with the transom until I know more, but ripping it out is not an option.

Regarding the other two stringers... they are towards the outside edge of the bilge area and the only water that could have gotten into them would have been from the motor mount holes. I will use a moisture meter to see how wet they are. My hope is to replace just the sections where the mounts lag to....but won't know more until I get a better idea of their shape.

Meant to take pics but left my phone home the day I tore them out. Will get some next time down.

--Rick

 

[Skua]

I think stringers made from a solid piece of Doug Fir, would be preferable to ply