Stringers directly to hull ?

[Bronko]

Hey everyone, been reading the forums for a few weeks now and am just plain addicted. You guys got a really great community here.
So i am in the middle of a total rebuild (deck, stringers, transom) and everything is going smooth thanks to the forums here. id like to add in some stringers and cross members to strengthen the boat and deck as there is only 1 running from bow to stern in the middle.

1. the boat came stock with 1 stringer and the rest foam (structural?). is it a bad idea to add more for a more solid deck?

2. if so i notice that the 1 stringer has about 3/4 of an inch of foam between it and the hull should i copy this technique.

thanks in advance.

 

[MTribe08]

Re: Stringers directly to hull ?

Nope, not a bad idea..in my rebuild I added a few more ribs for hull/deck support. Came out really solid.

As far as the foam in between your stringer and hull...That is one way to do it. Bascially what you want to avoid is having wood directly on your hull after you've fiberglassed it in. This can cause "hard spots" and put direct stress on certain parts of the hull. You want to bed the stringers in something..Doesn't have to be foam. I used a mixture of Poly Resin, talc powder and sawdust. The end results was very strong and sturdy. I think one of the most common and probably cost effective methods is to bed them the using PL Construction Adhesive.

Good luck and you might want to start keeping an updated thread of your own...as you well know there are many amazing people on here willing to pass along a ton of advice and years of experience.

 

[Bronko]

Re: Stringers directly to hull ?

thanks for the quick reply, all solid informatiom

 

[ondarvr]

Re: Stringers directly to hull ?

Since the stringer didn't contact the floor, adding more using the same method will do nothing to make the floor more solid because the foam is the only thing supporting it.

You can add stringers as needed for support, but add as few as possible because each will cost money and add weight.

 

[Bronko]

Re: Stringers directly to hull ?

so if i go the pl way of setting my stringers should i apply a real thick bead or just use a normal lamination type amount

 

[oops!]

Re: Stringers directly to hull ?

wow....lol.......the two above statments contain a lot of info for few words....

ok...pl...just use enough to keep the strings off the glass. shim the stringers and add the pl under them if you have to. dont go more than a 1/4 to 1/3 inch.....you just want to avoid a hard joint.

second....the pl must cure fully before you glass over it.
the pl needs air to cure.

that carp about foam between the stings and glass make me ill.

make sure when you cut the top of the new stringers that there is a flat surface to attach the new deck to......the center stringer can be a little lower, so there is a drainage to the center and then the bilge, but not much

cheers
oops

 

[sbklf]

Re: Stringers directly to hull ?

id like to add in some stringers and cross members to strengthen the boat and deck as there is only 1 running from bow to stern in the middle.

1. the boat came stock with 1 stringer and the rest foam (structural?). is it a bad idea to add more for a more solid deck?

2. if so i notice that the 1 stringer has about 3/4 of an inch of foam between it and the hull should i copy this technique.

thanks in advance.

If it aint broke ...

If you don't tab the new stringers correctly to the hull, you wll be able to locate them easily from underneath in time by the cracking of the gel coat around them. The hull flexes. You would be better off with stronger sole material.

Foam between the stringer and the hull? The stringer should be solid to the hull, use thickened resin for filler. The reason there is filler between the stringer and the hull is because thats easier than cutting the stringer to the exact contour of the hull. They make it sound like you need to keep the stringer off the hull, why? If for deterioration purposes I have news for you, if water gets past the fibergalss wrap around the stringer, the stringer will rot weather it is bedded 1/2" off the hull or directly on it. Bed the stringers solid to the hull with thickened resin and seal them with glass.

PL? If pl is the liquid nails type stuff you get at Home Depot, don't use it, the resin won't bond to it and it does not cure hard. I see pl thrown around a lot on this board for this use and disagree. I doubt that you would find it used this way from the factory.

 

[toey77]

Re: Stringers directly to hull ?

i know nothing of this so was glad to see this come up as i had asked it but didn't get a reply, but just to clarify thing and add a query i was researching this and thought of "you tube" i came across a video of special made stringers that have a felt backing on them, and they said it was for the reason to take stress of the hull and allow the glass to flex when hitting waves hard.

watch it from about 4.00 min in and see what you think of you can just watch it all

http://www.youtube.com/watch?v=7gY1ZJwIJAI

 

[cedarjunki]

Re: Stringers directly to hull ?

If it aint broke ...

If you don't tab the new stringers correctly to the hull, you wll be able to locate them easily from underneath in time by the cracking of the gel coat around them. The hull flexes. You would be better off with stronger sole material.

Foam between the stringer and the hull? The stringer should be solid to the hull, use thickened resin for filler. The reason there is filler between the stringer and the hull is because thats easier than cutting the stringer to the exact contour of the hull. They make it sound like you need to keep the stringer off the hull, why? If for deterioration purposes I have news for you, if water gets past the fibergalss wrap around the stringer, the stringer will rot weather it is bedded 1/2" off the hull or directly on it. Bed the stringers solid to the hull with thickened resin and seal them with glass.

this looks the same as my fathers aristocraft that i just cut part of the deck out of... a single ply stringer down the keel....if you want to consider it a stringer anyway...
but as i could tell they molded the inner hull, around plywood deck, flipped it over, and glassed the ply stringer in place to the deck....then attached inner hull to the outer hull and filled with foam through the upper part of the deck allowing foam to flow between stringer and hull... this ply stringer also ended about 4 inches from the transom.......the foam was the main structure for everything, with the stringer glasses to the deck just to help stiffin the deck....
atleast this is how it looks to me. i plan on using the same width stringer* but maybe double the ply or use 2x8 even since i cant glass it to the deck, but would be able to glue/epoxy and screw the deck to it.

take a piece of ply, snap it in half.. pretty easy.... now glue another piece under one on edge forming a T.... becomes structural....so my belief is that the stringer is structure for the deck but the foam is the structure for the hull...
does that sound right?

 

[ondarvr]

Re: Stringers directly to hull ?

The foam used under the stringer does the same thing as any type of putty or bedding compound, it just spaces the ply off of the hull, what you use isn't that important. A great deal gets mentioned about using something under stringers, but I would say that a large number of small boats are made new with nothing between the stringer and hull.

When I said using the same method, I meant that in the pic the stringer doesn't rise all the way up to the floor, so only the foam is supporting it. Doing more in this same fashion won't support the floor any better than it was before, so you'll need to make the stringers taller and have the floor rest on them to make any difference.

 

[drewpster]

Re: Stringers directly to hull ?

A great deal gets mentioned about using something under stringers, but I would say that large number of small boats are made new with nothing between the stringer and hull.

True. I found allot of dead space under the stringers of my tri-hull when I pulled them out. I think the manufacturers use whatever method is the fastest. The keel was the worst. I was really surprised how thin the glass was in that area. I completely filled the keel and used PL Premium the bed the center stringer on top of it. At least I know it will take about 100 years of beaching wear to rub through it again. As was mentioned above, use just enough glue to keep the stringer from coming in to contact with the fiberglass skin and let it completely cure before glassing over it.

 

[coastalcruiser]

Re: Stringers directly to hull ?

why do they put a stringer in the middle where water collects??
I would probably take the time to put 2 stringers in on each side if there is room so it doesnt sit directly in the water.

 

[jonesg]

Re: Stringers directly to hull ?

David Pascoe the marine surveyor puts it like this,

"Example of hard spot caused by improper stringer design and installation. Bottom hinges around hard edge of stringer wood core. At right(2nd pic), wood core is elevated by a soft material so that it does not touch the hull skin and the load is bourn by the more flexible tabbing. "
http://www.yachtsurvey.com/HullFailP2.htm

Smaller boats get away with it because the size of the glass panels between stringer and cross braces is small enough to stay rigid.

I used PL to space the stringers off the glass, it works very well for this.
It works as a semi flexible spacer and holds the stringer in place whilst you glass the tabbing in place.

But as OOps stated, make sure its cured or it will actually dissolve when resin hits it....and start running like milk.! ( or so I'be been told of course)

 

[Bronko]

Re: Stringers directly to hull ?

Thanks for all the info guys, I'm pretty sure now that i will remove the center stringer and replace it with 2 just off to the sides where the hull has an edge to it. gonna use pl premium being an ex- carpenter i know the bond will be solid. Do you think i can get away with removing the center stringer and not replacing it or will this really wreck my structure.

 

[Bob_VT]

Re: Stringers directly to hull ?

Oh adding a stringer is okay but not replacing one is a formula for trouble. Be sure to replace that center one because it is the supporting the keel.

Trust me I have been in a boat that split it's keel and it's no fun.

 

[jonesg]

Re: Stringers directly to hull ?

Oh adding a stringer is okay but not replacing one is a formula for trouble. Be sure to replace that center one because it is the supporting the keel.

Trust me I have been in a boat that split it's keel and it's no fun.

They definately put the center stringer there for a good reason.!

 

[coastalcruiser]

Re: Stringers directly to hull ?

Bob_VT Re: Stringers directly to hull ?

--------------------------------------------------------------------------------
Oh adding a stringer is okay but not replacing one is a formula for trouble. Be sure to replace that center one because it is the supporting the keel.

Trust me I have been in a boat that split it's keel and it's no fun.

Bob,
maybe if the boat you were in split because the hull was made incorrectly?

I would say that the stringer does add structural strength lengthwise but are put in to hold the floor up as well depends on the boat
the poster said

Bronko
2. if so i notice that the 1 stringer has about 3/4 of an inch of foam between it and the hull should i copy this technique.

imo if the stringer was held in by foam its not helping the hull much and is merely holding the floor up
grinding and glassing ribs and stringers onto the hull is what i did because I run out in the ocean

This photo shows a completely redone transom and stringers and was done bow to stern

 

[jonesg]

Re: Stringers directly to hull ?

The spacer made from foam is merely to space the stringer off the hull, the stringer is integrated to the hull by the glass from stringer to hull.
Some boats have stringers made from 100% foam, then glass is laid over them.
Not all stringers reach the deck, they are to make the hull firm.
The center stringer on my hull is a half pipe of pvc which is glassed over.
Different designs, but I would stick with original to avoid surprises.