Such a Thing As Making the Hull Too Rigid?

[76SeaRay]

I am going from the factory work of somewhat randomly squirting in bedding for stringers with what appears to be a power caulking gun (if they had them in 76) then missing the bedding material so that almost all of the stringers were floating in foam with no fiberglass except on exterior surfaces (floor). I am fully bedding stringers with peanut butter and then fiberglassing inside and out, I am wondering is there such a thing as making the hull too rigid??

 

[dingbat]

I want things in a structure to be stiff, not rigid. Even then you can very easily get yourself into trouble rather quickly.

In a structural world everything is dynamic.
Not only do things need to flex to accommodate from normal loading, you also you have to account for forces introduced from the expansion and contraction (heat, moisture) and of the various construction materials.

Glassing in the stringers might sound like a good idea until the stringer, with no place to go, breaks loose at the connection with the hull or pushes out, causing a bulge in the side of the hull.

 

[76SeaRay]

So, did I get it wrong by fully bedding all of the stringers with polyester peanut butter? Most of what I have seen on youtube etc has been to fully bed them.

 

[AShipShow]

So, did I get it wrong by fully bedding all of the stringers with polyester peanut butter? Most of what I have seen on youtube etc has been to fully bed them.

No, you're good... You can bed stringers with peanut butter, PL, just about anything... The goal is really to have the stringers sit slightly above the hull and not directly on the hull... The real strength of the stringers comes with the glass that goes over them.

 

[froggy1150]

And your tabbing works kinda like leaf springs. The widest layer will flex so much...
And then every smaller layer stiffens it up a bit more. This spreads the load gradually over a wider area so things bow like a spring and not like a hinge

 

[Lectro88]

I have also wondered this same thing.
And I will admit guilt for over-doing/overbuilding everything and making things incredibly over strong. this includes adding extra stringers, more fiberglass and transoms you could pull a dozer on top of.
Why would you do that or need that..?
Answer=Never did this kind of work before. was never a code minimum, do just enough to get by.
If you'r there do it right and don't worry about it later.

So when you start taking a boat apart.
Things start flopping, sagging.
You start adding things and things stiffen up and sometimes become solid and rigid.
Then you add the cap, things really stiffen up more at this point..
Then you pour foam and if it had any give before,,. IT DOESN'T now.
Now I can't say I want a boat that flexes and twists, I intend for it to float and be solid in the water.
If I plow a wave or dolphin/porpoise and slap down hard. I would hope the water would eventually give. not my boat and its structure.
Now I may be wrong in how I feel about this and will listen to good reason.
But I have always built everything I touch on the stronger more stable side.
Thats carpentry, trailers, Hyd. wood splitters, steel fab, Electrical, floors.
I don't buy 4 ply tires, 8-12plys. even putting gravel down, I over do that too.
I promise you, I'm not building anything that will flex or twist and give.(on purpose)
That was never my intent.
So boats may be my epic fail. time will tell.
I'm all ears and eyes at this point.
You hear don't add too much weight. Yes we cry that in aviation too.
I'm using wood and fiberglass. so I added 50-100 lbs. whoopie.
Nobody said anything about the 500-800 Lbs of wet foam I removed.
depending on buoyancy calcs. they will surprise you what displacement will carry. Leave the 5 yr old and the cooler on the dock is my ugly reply to adding too much weight.
JUST wait/weight til I add twin motors and 2 additional fuel tanks.
Commercial boats are steel.. (flex/weight?)
I know I really seemed to stir the pot. was not my intent. just sharing my point of view. and how I think things.
Another thing,.. while I'm stirring,.
back in the day... they over did things. I'm doing a 1969 rebuild.
Boats then were stronger then, than todays I would gamble.
1 more reason why I chose the boat I did to monster re-build.
AND Another 1 more thing.
So why did you start tearing your boat apart,.?
floor was flexing ?
the stringers were rotted?
the hull would flex,? when you pushed against it ?
The transom was mush and pushed in where the motor was pushing it through the back of the boat.?
Wait., is flex a good thing or a bad thing,. maybe I should have left my boat alone and just used it til it sank.
Respectfully.
I don't mean any of this in a bad way. I just wrote it Blunt and to the point.
and some twisted humor leaving the kids and cooler behind. for overbuilding.

 

[jbcurt00]

The stringer bedding is the 'foot' of the stringer and prevents point loading the hull w a hard edged stringer.... sort of a snowshoe to spread weight from above and dissipate impacts from below....

Also remember decks, stringers and transoms are systems that work together w the hull and the glass tying them all together..

Using a boat w any 1 area compromised can lead to failures in other parts of the system, which are mostly hidden from view, and should be avoided.

Likewise, applying steel plates to a soft transom transfers the transom load to other areas w unknown consequences, worse yet is beefing up the transom and knee braces to support/use an oversized motor. Has it been done, yep. Did they survive(boat and the boaters), yep. Will it last decades, maybe maybe not. But surely the hull wasnt designed to support that load and what ties the transom and knee together? The now extra stressed hull.

Ask lots of questions, read the advice given, and make the best decision possible for you, your boating family and the boat. Whatever you think & decide is what you and the boat have to 'live' with, the

Full Send It!

won't be around to help gather the pieces when it goes wrong and if and/or when it does, its always a surprise to the boater.

The I did it, you can too crowd is wose still. You dont know them, their boat, their boating and boat rehab level of experience/talent nor the conditions of the system mentioned earlier or the waterway they'll boat in vs where you boat.... How can anyone honestly say: I overpowered, you can too. Even state to state the rules are different.


Back to you regular scheduled programming.... apologies to @76SeaRay for the rant, it would seem you are being very diligent and thorough

 

[KJM]

So, did I get it wrong by fully bedding all of the stringers with polyester peanut butter? Most of what I have seen on youtube etc has been to fully bed them.

For what its worth, my old stringers looked to be bedded in PB and then encased in glass. It was in my opinion a very well built boat. I redid it the same way. Some people put small pieces of foam at spaced intervals under the stringers but I don't see the point if all the space between the foam is solid PB between the hull and the stringer?

 

[GSPLures]

For what its worth, my old stringers looked to be bedded in PB and then encased in glass. It was in my opinion a very well built boat. I redid it the same way. Some people put small pieces of foam at spaced intervals under the stringers but I don't see the point if all the space between the foam is solid PB between the hull and the stringer?

Probably used to hold the stringer off of the transom when piping pb under them. I did it similar but used tile spacers. once I had the PB locking the stringer down I knocked out the spacers and filled with PB

 

[76SeaRay]

Great info gang. Thanks for all the input. I was hoping to have all my stringers in and much of the deck on by now since it is nice weather for working here this summer. Unfortunately, right after I posted, everything came to a screeching halt due to Covid-19. I am still recovering.