Stringer help

[Reefdog]

Sorry for another stringer post but I’m at this point and see lots of different options on what to do. I am dealing with a single 12 ft stringer in a 16 ft boat. I can see the wood inside the stringer is rotten in some places but the glass around it is solid a rock. I am seeing many different options for correcting this.
I read about leaving the existing wood and just layering more glass over and farther out over the original glass. This makes sense since the glass is the actual strength. Is this a real option? If so, that’s what I will do. I will use 1708 and put a bunch of layers.

The other option would be attaching new wood next to the existing stringer and then glassing the whole thing in with 1708.

final option Is removing the whole thing and starting fresh.

any help is appreciated

 

[ondarvr]

For the most part it’s not going to make much of a difference in which method you use, it will be usable for many years as long you do something.

The main reason people frequently replace everything is because it was done so poorly when it was first built.

Often the poor workmanship requires everything to be removed so there’s a good foundation to work with

If you decide to glass over what's there, you don’t need to add a huge amount of glass if it’s covered by a decent amount of glass.

Sometimes there’s only one layer of CSM and one layer of roving over the wood, this will require more glass.

As for grinding dust, finding good dust masks now could be tough, the cheap ones don’t help much, it may be easier to find a paint type respirator.

 

[missinginaction]

Ondarvr knows his stuff. I'd add a couple of things. With regard to the 1708 biaxle mat. You'll find that 1708 soaks up huge quantities of resin due to the mat layer. You would be better off using heavy fiberglass roven woving and skipping the mat. The result will be just as strong and lighter. I'd also say that your decision on replacing or just reinforcing an existing weak stringer would depend on the stresses that stringer would be asked to bear. I chose to replace the engine stringers on my boat years ago because I didn't feel that any amount of reinforcement would give the old rotted stringers enough strength to carry the load of the engine and the propulsion forces. In another area of the boat I decided to simply reinforce the weakened stringer with extra layers of roving because I simply wanted to stiffen it up and was not concerned with load bearing ability.

 

[Reefdog]

Thank you Ondarvr and missinginaction,
I appreciate all of the help. The craftsmanship seems to be pretty good on the original stringer. The boat is old and the glass is still very strong along the stringer until the bow. The bow is where I see the rotten wood. I am having trouble deciding if the stringer went all the way to the bow and touched the bow, and the glass and wood just rotted away, or did it end about a foot away from the bow and not touch the bow? It’s good to know I can beef it up and keep going with the project. I was nervous to remove the stringer and lose the hull shape and I’m trying to cut down on my grinding. I use a 25 hp tiller engine on this boat and mostly stay in shallow calm water. I think judging my skill level I will try to add more layers of glass where it is still strong and then add new wood and glass in the bow where it’s rotten. Any thoughts about if I should have the wood all the way to the bow or end it a foot short, where it seems to end now?

 

[ondarvr]

Don't try to reinvent the design if it didn't fail other than the rotten wood.

 

[Reefdog]

I’m not sure where it stoped

 

[kapnD]

It looks like it stopped short of tying into the bow, allowing the nearly vertical surfaces of the hull to pick up the load.
Unfortunate that it wasn’t sealed off!

 

[Reefdog]

Thank you KapnD,
You answered my question of how the bow was supported before I thought to ask it. I agree, I can’t find any evidence that the glass went to the bow. I’m not sure why they didn’t seal the ends. Both ends are unsealed

 

[missinginaction]

Based on the photos we're looking at the bow of the boat? I'd say it isn't critical to glass them into the hull itself, just leave a little clearance. As the boat enters the waves it may flex a bit. You don't want the structure too rigid. If it is the hull could stress crack in that area. I remember when I was building my boat my floors (some people think of them as transverse bulkheads, port to starboard) were not fiberglassed to the inside of the boat's topsides. I wondered about this. It seemed to me that they should be attached. The boat would be stronger. What I learned was that the original manufacturer deliberately left them unattached because the boat tends to flex while underway. If I had glassed them in I would have limited the boats ability to flex. That's how I see it anyway.
Something else to keep in mind is that just because an original builder did or didn't do something, it doesn't mean that they did the job right. It would have been good practice to seal the ends of those stringers to prevent deterioration. It probably was skipped due to sloppy workmanship. The designer could specify something. That doesn't mean that the person doing the work got it right.