Bedding stringers

[KJM]

I'm in the process of installing new stringers in my boat that I converting to an outboard. I was watching a video on the subject and the gut was putting foam tabs every 6 or 8 inches under the stringer before using thickened resin to bed the stringer in.I think the point of the foam was so the stringer wouldn't create a hard spot on the outside of the boat. My questions are how would this do anything if the stringer is resting in hardened resin in between the foam tabs? Also is this really necessary? The old stringers i removed looked to be bedded straight onto fiberglass with no cushioning. I'm going with straight Thickened resin with glass mixed in as per original construction. Any thoughts?

 

[chevymaher]

I wondered the same thing.

 

[jbcurt00]

Think of 1 as a cast and 1 as a splint, offering different types of support....

A stringer spaced off the hull 1/4in and then tabbed/bedded in resin made fillets is a cast, spreading the load from the stringer across the entire width of the fillet against the hull. Done well, no chance of a strike against the exterior hull telegraphing directly into the plywood stringer nor someone jumping off the dock into the boat forcing the stringer to flex directly against the hull.... even done poorly, it offers some protection..

Rest the stringer directly on the hull and tabbing it w a fillet that is only along the side of a stringer, is more like a splint. A hard enough strike from above or from below forces the plywood stringer directly into the hull even if done well. Done poorly w hard square edges to a stringer against a hull and the risk of damage is greater

The foam is only a temp spacer,

Read WoodOnGlass' transom, deck and stringer info? It shows best practices.

 

[In way over my head... always]

So the thickened resin, once fully setup, is "softer" than the wooden stringer? Is the spreading of the forces because the thickened resin is bonded to the filets? Or am I looking at it too simply? I've been wondering the same question as the OP. I've read WoodOnGlass's thread, as well as quite a few others. Sometimes, it seems that the more I research,the more unsure I get.

 

[GSPLures]

So the thickened resin, once fully setup, is "softer" than the wooden stringer? Or am I looking at it too simply? I've been wondering the same question as the OP. I've read WoodOnGlass's thread, as well as quite a few others. Sometimes, it seems that the more I research,the more unsure I get.

I have looked into this alot also as I am almost ready for bedding my stringers. I believe the goal is to have consistent contact with the hull kind of like a rock hitting glass and it not breaking because it hit solid and spread out the contact. opposed to the tip of a rock hitting glass and it shatters because all the contact was hitting in a small localized spot.

From what I read if you can cut the stringers with 100% accuracy and contact you wouldn't need a bedding. But I may be wrong on that.

 

[todhunter]

I have looked into this alot also as I am almost ready for bedding my stringers. I believe the goal is to have consistent contact with the hull kind of like a rock hitting glass and it not breaking because it hit solid and spread out the contact. opposed to the tip of a rock hitting glass and it shatters because all the contact was hitting in a small localized spot.

From what I read if you can cut the stringers with 100% accuracy and contact you wouldn't need a bedding. But I may be wrong on that.

This makes sense to me. In reality we are likely not cutting our stringers to match the hull 100%, so there will be small contact points and small gaps all the way down the stringer. I guess the foam just ensures you don't mash the stringer all the way to the hull when bedding it, and allows the PB to fill the gap and make a 100% matching surface between the stringer and hull.

 

[GSPLures]

This makes sense to me. In reality we are likely not cutting our stringers to match the hull 100%, so there will be small contact points and small gaps all the way down the stringer. I guess the foam just ensures you don't mash the stringer all the way to the hull when bedding it, and allows the PB to fill the gap and make a 100% matching surface between the stringer and hull.

That is what I got from all the research I have done. I believe this is why some people use PB others PL or foam and I have even heard of an empty gap under the stringer(I dont know if I'd trust the last one though) with no adverse effects. There are a million ways to skin a cat and still end up with the same results. Most of the arguments I have seen about how to bed stringers are usually based on this is always how I have done it with no real explanation as to why.

 

[Baylinerchuck]

Also adding to what jbcurt00 stated which was a good analogy.

If you were to tab a stringer in, which was only placed against the hull, there may be a little wiggle room for the hull to flex against that wood since the wood is not bonded to the hull, the tabbing is. This could eventually cause the hull to flex damaging the gelcoat and structure.

Bedding a stringer ensures the wood of the stringer is 100% bonded to the hull, then the tabbing is bonded to the hull, to the bedding, and to the stringer. This is much more strong. Also, keeping the stinger off the hull may keep it from rotting as quick should water get in.

I always add in 1/4” chop strands to my peanut butter to strengthen it. PB without chop has no strength and can crack easier.

 

[JASinIL2006]

I think you either want the stringer off the hull, to avoid rubbing/hitting in just a few spots, or you want a good, complete bed of resin to distribute the contact between hull and stringer over a very large area.

 

[KJM]

I put PB in the channel left by the old stringers and sat the new ones into that, so I guess i'm good. I cut strips of CSM about 1 inch wide and about 4-5 inches long out of left over bits and add this to the PB. The resin melts the binding agent in the CSM and you have your loose fibers in the PB for strength, works really well. I also use one of those rubber spatula things with the rounded corner for smoothing out fillets, works great. Now I have to just get all the stingers the same height so the floor will be level, maybe run a string from one side to the other and cut all stringers to just touch the string?

 

[froggy1150]

Thought i took picks but guess i didnt.....
what i did to set my stringers is took 2x12's that spanned across boat that were cut to match the hull profile and then cut slots for the stringers. The slots were cut so the stringers were square and set the height also. Then plenty of pb, squished the stringers in, drop the 2x12 and clamp.

 

[kcassells]

Thought i took picks but guess i didnt.....
what i did to set my stringers is took 2x12's that spanned across boat that were cut to match the hull profile and then cut slots for the stringers. The slots were cut so the stringers were square and set the height also. Then plenty of pb, squished the stringers in, drop the 2x12 and clamp.

You did...they just didn't post lol!