Question about PL and stringers...

[SynPDX]

So I'm learning quite a bit from Friscoboater and his YouTube channel.... But I have a question about stringers and PL....

In one of his YouTube videos, he mentions that the stringers should not be in direct contact with the hull. Instead they should be floating 1/4'' and held in place by PL. After all is cured, the stringers get tabbed in. He even mentions that he has no idea why this is the case....

If the stringers are tabbed in, how is this any different than the stringers being in direct contact with the hull? The "flex" is gone at that point, so I'm a bit confused....

Thoughts?

Thanks!

-Pete

 

[Woodonglass]

First I don't like using PL to bed the stringers. It takes up to a minimum of 72 hours for it to stop outgassing and even then once it's fully cured poly resin has issues bonding with it. Most of the members on the forum use resin thickened with cabosil, we call it Peanut Butter, to bed the stringers in.

As far as WHY you don't want the wood stringers in direct contact with the glass hull, it's to avoid "Hard Spots" that will cause the fiberglass to crack and craze. The tabbing spreads the load over a broader base and therefore lessens the probability of this happening.

 

[SynPDX]

So I could float the stringers off the hull, and hold it all in place with peanut butter.... Exactly what I wanted to know, I think I'm going to skip this PL bit....

Thanks "again" for your help!

-Pete

 

[jbcurt00]

Former strong proponent of PL for stringers, but nope, resin based PB filler is a much better choice.

Good luck w your project

 

[tpenfield]

OK, my 2 cents on the subject . . .

PL is probably not the best thing to use, based on the curing time and some bad experiences that have played out on this forum. PB is a better approach, or an adhesive that is more compatible with the resin used for tabbing in the stringers.

As far as non direct contact, it is a matter of distributing the load exerted on the stringers by the hull over a wider area and providing some 'give' or flex. During wave impacts, the hull area exerts huge amounts of force on the stringers. If the the area of contact of hull to stringer is to narrow and inflexible, it will actually crack the outside of the hull. If you ever see a boat hull with gelcoat cracks along where the stringers are located, that is what's happening.

 

[Yacht Dr.]

Woody is correct on the 'hard spot' answer. Its more for larger boats where there are larger open areas ( pans ) between the stringers/bulkies.

Most important is to not have any individual places where the wood is in direct contact with the hull. Now if your stringers are Perfectly mated to the hull..then you would be better off. Your 'filler' Should be a light filler. Cabosil and resin is just as hard as the wood..giving you that perfect mate up. However this is not 'floating'. You could raise them with 1" x 1" stir stick shims..then glass them puppies in if you like. No need for the filler at all really.

So if you want to fill them use microballons or something thats softer than wood.

 

[kcassells]

Alot of guys also shim in 1/4" foam pcs @ 3/4" long under the stringers and glue them in. Once they are set up you have made the "no contact" spacer to then run in your pb. Space out @ 1 every 18" should do just fine. Also have seen the use of hot glue to do the same thing as above. Just a dab will doya!