PB bedding for stringers, how thick is too thick?

[Daniel1947]

OK....Long story short. Transom is in, tabbed etc., and I have laid out the stringers, hull stiffeners and bulkheads. Everything was positioned, measured, etc., over and over. I allowed for approximately 1/4' space between the main stringers and the hull for bedding with PB. The height of the stringers was just slightly below the outer sides of the hull, which was going to allow for a slight angle towards the center for the deck, maybe an 1/8" slope from outside to center. The preliminary measurements and layup were done prior to the transom or anything being attached permanently.



Yesterday, after doing a final lay up to mark positions for applying the PB, I discovered that for some reason the stringers were now a lot lower than the original layup. I have absolutely no idea as to what happened. Possibly the hull shifted on the cradle, but I have rechecked it and it seems to be sitting where it was.

NO, absolutely nothing was cut or trimmed after the original layup. I did a little grinding/sanding on the hull, but didn't remove that much. It was more or less a clean up sanding with 60 grit.

My options are: 1. Purchase more ply and redo stringers. NO, not going to happen. :facepalm:
2. Lay an additional strip of ply on top of stringers to bring them up to required height.
and: 3. Increase the thickness of the PB bedding from to maybe 3/8" or 1/2"

Since the 1708 tabbing actually holds the stringers and supplies the strength, I am thinking of going with #3. Anyone else have any experience with using a thick layer of PB?

 

[kcassells]

You will be fine with 3/8" to 1/2" pb bed. Make it thick so you can "push" it under and still be able to shape it up. I've seen guys use spray foam to fill the voids and then pb to that. Either way will work. You're fine.!

 

[ahmincha]

I have areas under stringers that probably hit the 1" mark I just shaped it like the plywood the came back and coved it with a spoon as kc stated you'll be fine

 

[gm280]

Yes the PB can fill in most any differences without any issue. I have some close PBed areas and some larger PBed areas and they all came out great and on the lines I set out. Not a problem. For the larger areas you may need to mix a little thicker to keep it in there 'til it cures, but other then that, no problem... :thumb:

 

[ondarvr]

It makes little difference how thick it is, just fill as needed.

 

[Daniel1947]

WOW! I think we may have a first here on the "Forum." :cheer2: 4 Knowledgeable members all in agreement. :lol: Seriously, thanks everyone. I appreciate the input and I hope everyone out there had a great Father's Day.

 

[gm280]

WOW! I think we may have a first here on the "Forum." :cheer2: 4 Knowledgeable members all in agreement. :lol: Seriously, thanks everyone. I appreciate the input and I hope everyone out there had a great Father's Day.

Oh yes Daniel, stranger things have happened, but I can't remember when...ound:

With any comment website everybody has opinions, and some times those opinions back up each other... Post some pictures of your project. We love pictures... :thumb:

 

[Woodonglass]

Ok we CAN'T have any of this!!! There MUST be PRECISELY 483.235 mm of PB mixed to the consistency of Grey Poupon placed under each stringer and spread with a Betty Crocker Soup Spoon and it MUST be done on a Friday at precisely 3:33 pm. NO QUESTION ABOUT IT!!!!:eyebrows:

 

[89 resorter]

Hey Wood.... should the PB be made from Polly or Epoxy or does it have to be PB at all, wouldn't PL be just as good? I'll just sit back and enjoy the responses opcorn:

 

[52FordF2]

Thanks Daniel for putting in the question I was too afraid to ask. I think mine may have 1.25 inches gap :watermelon:

 

[kcassells]

As basic as it was that WAS a really GREAT question! And there are millions more. :yo: for posting it. I've pondered that myself until today's unusual responses.

 

[Woodonglass]

To tell you the truth, the next boat I do, I'll prolly be gluing blue foam strips to the stringers and using NO bedding material at all. I'll use the Stringer jig to hold em in place and keep em vertical while forming the PB fillets and move on.

 

[Yacht Dr.]

I kinda agree with woody. I think that the resin that you use in your PB would be better served wetting out another layer of scrap glass in your tabbing. No PB is needed. Now 1.25" is a bit much. I would cap the top of the stringers before I put that much PB down there.

 

[gm280]

The real issue here is that most every boat refurbishing project on these forums will last years if not decades because of how much detail the owners goes through. No factory built older hull has as much attention to building the boat then the average boater on these forums. So while there is different ideas of how to do certain things as there is to the secret recipe for PB, the finish projects will last amazingly longer then factory... JMHO!

 

[Daniel1947]

Interesting concept Wood....No bedding at all. If you are going to only use the PB for fillets, why bother even doing that? Hold the stringers in place with the jig, lay in a couple tabs of 1708 to hold the stringers, remove the jig and just tab the heck out of the stringers with additional layers of 1708? Since I have seen stringers made from some kind of foam composite, it would look to me like the wood isn't really necessary, that it is the 1708 that gives it the strength.

 

[Woodonglass]

Yeah, but... glass doesn't like making square corners. The fillets help make the curve with no air pockets as well as broadens the base. You could prolly do it if you took your time and "pre-Creased" the 1708 fabric to make it take the bend at the hull line and then did some baby sitting when it started to kick to ensure it didn't bubble on you. You're correct that the glass is where the strength comes from.

 

[Daniel1947]

Yeah, I understand the curved fillet Wood, I was thinking instead of curving it at the base, angle it from the top to the bottom, make a triangle out of the 1708 from the top edge of the stringer to the deck, like they do in construction. Everyone knows a triangle is strong that is why it is used in construction....bridges, trusses, etc. LOL, I hope you know I am kidding. :facepalm::lol:

But in reality, since I already have the stringers positioned and have PB'd a few areas between the stringer and hull, I can just forget about shoving more PB under the stringer. Just lay fillets and then 1708. That will definitely save me some resin.

 

[Woodonglass]

There ya go!!!!

 

[Yacht Dr.]

But in reality, since I already have the stringers positioned and have PB'd a few areas between the stringer and hull, I can just forget about shoving more PB under the stringer. Just lay fillets and then 1708. That will definitely save me some resin.

A 4-5 stack of 1708 and mat will darn near make that 90 degree bend...especially the inboard radius. Outboard is less than 90..so yea..maybe fillet in there.

I just wet out the stack and lay them out..bubble roll..and done. I dont use fillets unless its a Very angled area. Just sayin..after that much glass..its gonna be tank no matter what