Stringer replacement

[hollowbase]

I removed the rotted section of stringer by cutting the top off the the fiberglass. I cut the sides down and left myself about a 4 inch channel to accept the new stringer section. My quiestion is should I use epoxy on the bottom of the channel to bond the stringer to the hull and then start laying up the fiberglass to cover the top?

 

[AShipShow]

I would hesitate to take the approach you're going for.. Leaving that channel won't let you grind down the fiberglass surface on the sides and bottom of the channel to get to fresh/clean fiberglass... You aren't going to get there with cleaners/chemicals, you need to abrade the glass down to clean stuff.

My recommendation would be to completely grind the channel down flush with the hull and clean the glass and give yourself lots of room on both sides for tabbing in the new stringers.

 

[Chris1956]

I agree, fresh fiberglass is essential for the stringer to adhere well. Also, you must fill any voids in the mating surface of the stringer. That means using thickened resin, putty or something like those. Slather that stuff on the fiberglass and push the wood into it. Clamps, screws and other fasteners are great if you can find a way to use them. After the resin sets, some fasteners can be removed if you want.

Also, epoxy resin is not necessary. Polyester resin is just fine for your purpose. When bonding new wood, mix the catalyst at about 75% of recommended, to slow the curing process and allow resin to absorb into the wood a bit longer.

BTW - Never mix epoxy resin + hardener at anything other than the recommended ratio. it may not harden...

 

[hollowbase]

Thanks for the responses, guys. That's good information and I will certainly follow your instructions. I'll actually start putting in the new stringer tomorrow, a little nervous about this process.

 

[Wildey]

Thanks for the responses, guys. That's good information and I will certainly follow your instructions. I'll actually start putting in the new stringer tomorrow, a little nervous about this process.

No need to be intimidated, all the help you need is here.
Don't skimp on the safety gear and proper practices.
Most importantly ... Safety first !

 

[Sabin1269]

I did what the previous poster recommended and it worked out great as far as grinding and cleaning up the old glass. I ended up using PL construction adhesive to bond my stringers to the hull and they are solid!! After that I went and tabbed in the stringers with some 6” fiberglass before I started laying the glass all around it. Friscoboater had done a full rebuild on one of his threads and that’s what I used for a lot of good tips and tricks.

 

[tpenfield]

4 inches of old tabbing is a bit much. Maybe 2 inches or less. The new tabbing needs to be laid over a ground surface as the others have indicated. So decide how much of the old tabbing wall you want to deal with.

 

[kcassells]

No pics mean NOTHING. Can't see it so cannot not properly suggest approach.

 

[hollowbase]

Great responses, so what I've gotten out of this is abrade and clean the old fiberglass where the stringer goes, retain a little of the old tabbing. How much, would be dictated by my ability to to properly prepare the channel for the new fiberglass. The proper prep is vital. One more question, I purchased 3/4 ounce CSM, is that suitable or should I use heavier?

 

[AShipShow]

Csm is good for waterproofing/ capping the stringers.. for the sides and tabbing you want 1708 for poly resin or 1700 for eeeeeepoxy

 

[Chris1956]

3/4 CSM is a bit light. I like the 1.5oz mat for structural stuff.

Use 2-4 layers of 3/4 CSM for strength on stringers.

3/4 CSM is good for waterproofing the decking.

 

[Scott Danforth]

the information you need is in the stickies.

How To's and Other Great Information

Disclaimer iBoats has no control over external links contained in stickies and to be aware that links are fluid and may or may not work. 1. Coast Guard Safety Standards for Backyard Boat Builders Verified 2. Fiberglass Information Verified 3. Pouring Foam in's and out's Verified 4A. Basic...

forums.iboats.com

specifically links 14 and 18.