Can you splice a stringer?

[rickryder]

Hello everyone! I have a question that i have looked for here on the fourm...I have 2 inner stringers that are rotted from the bilage area to the windshield area. My question can I install new stringers and butt to the existing stringer them add another layer over it and along the existing stringer and glass it all together? Will splicing it be OK? or do I need to pull the entire stringer out and replace? I would really hate to do that because I would have to remove the top cap and it's a 21' Four Winns 210 bowrider .....

 

[rickryder]

Re: Can you splice a stringer?

OK nevermind I did find my answer after more searching!

 

[lowvlot]

Re: Can you splice a stringer?

So whats the answer?

 

[rickryder]

Re: Can you splice a stringer?

Yes it can be done! Glue screw and glass

 

[lowvlot]

Re: Can you splice a stringer?

I want to butt splice a stringer as well and think that wooden dowels coated in resin would be better than screws. What are some other opinions?

 

[Woodonglass]

Re: Can you splice a stringer?

Lining up your dowels could be a problem and would NOT be as strong as this method.

I'm just saying...

 

[rickryder]

Re: Can you splice a stringer?

Being a carpenter by trade that method of sistering works well. I had to ask the question because I'm no boat rebuilder. PL adhesive between everything and screwed together would make a tight bond and when it's fiberglassed in it should be very strong. I have read a 24" overlap on either side of the splice is recomended but I will go 36" just for peace of mind. Its very refreshing that you can still find great people willing to spread their knowlage to strangers.....but then again that happens once then they are no longer strangers and begin a bond of friendship! Thanks for being cool people!

 

[Woodonglass]

Re: Can you splice a stringer?

RR,

24 is plenty but do what you feel comfortable with, Once you get the glass on it will be totally strong enough. Not sure what you are using to glass your stringers with but I highly recommend 1708 Biax. Two layers and you will be good to go. Easy to work with and goes on like a dream.

I'm just sayin...

 

[rickryder]

Re: Can you splice a stringer?

Hey Woodonglass! Yes i will use the biax for the stringers and 2 layers of CSM 1.5 oz for my deck plywood, poly resin to coat unless it's better to use something else?

 

[erikgreen]

Re: Can you splice a stringer?

For stringer butt joints with butt blocks (what sometimes are called sisters) I'd strongly recommend epoxy instead of poly resin. You need the gluing abilities of the epoxy to get a really strong joint.

Using epoxy, a butt joint with blocks on both sides is stronger than a glued/screwed joint, and you won't have corrosion issues without screws.

You also won't need to cover it in heavy glass with epoxy... the joint itself will be strong enough. Just ensure the stringers are tabbed to the hull and cover with at least one layer of 8 oz glass to waterproof and protect.

My own stringers, fore to aft, are 12 separate pieces of wood epoxied together. Mostly this is because I have a complicated under deck structure. I'm not worried about strength at all.

Erik

 

[lowvlot]

Re: Can you splice a stringer?

Woodonglass,
I am going to use your method of butt joining and using the blocks on both sides. I was just going to use wooden dowles through the blocks on both sides and the stringers. I thought that by using dowles as the fastner it would be stronger and not have to worry about water penetration into the screw holes. No? What size screws are you using? Do you really have to go 24 inches? Why? What is the minumum? I have a bulk head in the way of going the 24 inches. What to do? What to do?

 

[Woodonglass]

Re: Can you splice a stringer?

Actually 12" on each side of the joint should be plenty. If you use epoxy or PL Premium to glue it together it WILL be permanent and actually stronger than if it were one piece. Screw length should be approx. 1 1/4 " Deck screws. Predrill your holes and then coat the holes and the screws with PL or Epoxy that way they will NEVER corrode.

I'm just sayin...

 

[erikgreen]

Re: Can you splice a stringer?

Just use epoxy and you can completely skip the dowels or screws. They're not needed. Really.

PL Premium should not be used in place of epoxy. It's not stronger or even equally strong, it's not even close.

PL Premium bond strength after 8 days is about 300-400 psi depending on materials bonded.

Epoxy is approximately 4000-5000 psi fully cured, depending on formulation.

Erik

 

[Woodonglass]

Re: Can you splice a stringer?

ERIK is correct on ALL counts but...
Sistering with PL Premium and screws will give you adequate strength for your stringers. Epoxy WOULD be better. It just depends on what materials you want to use. I DO 100% agree with NOT using Poly resin.

I'm just sayin...

 

[lowvlot]

Re: Can you splice a stringer?

Okay so no poly resin for making the butt joint. I can however use it as the wrap correct.

 

[erikgreen]

Re: Can you splice a stringer?

It's up to whomever is doing the work what they use, but just to make my point even clearer:

PL gets used a lot because it's convenient and cheap. It's stronger than poly resin by about 3x with respect to adhesion. Whether this is good enough depends on what you're gluing and whether or not the PL fully cures. It requires the presence of moisture (water) to cure.

The screws aid in clamping the joint, but may or may not add strength depending on how much the joint can flex. PL gives slightly (flexes) and the screws don't, so if the joint can flex at all (like in a stringer) then the PL gives until the screws take the weight. If the screws wiggle or crack the wood, the PL may stop further flexing, at which point only the strength of the PL resists movement.

PL has a lot of uses, even in boat building. Structural adhesive work is not one of them. Poly is worse. Epoxy is great, as is using single piece (of wood) stringers.

If you must have a cheaper substitute for epoxy, use resorcinol glue.. it's been used for dozens of years in boats with scarf joints and works well.

Erik

 

[Yacht Dr.]

Re: Can you splice a stringer?

Screws are IMHO.. just like erik said..good for "clamping" your wood together.

You should use them (screws) for your stringer sisters or joints to help keep your stringers together straight and true ( assuming you allready have done a Complete Dry run before you mix any resin ) . Screws allow compression for your sister glue.. unless you want to epoxy and clamp..then reprep everything that has poxy goosh ..then layup..

I personally like the " make stringers ready to go..get everything ready to go/prepped.. dry fit everything ( including glass schedule ) ready to go.... fits everywhere ? got sharp scissors ? got resin and possibly a helper for a six pack after ? check.. OOOOk Lets roll. Then Install/lam Everything " at one time approach. Using poly...

Again..just my approach..

YD.

 

[Woodonglass]

Re: Can you splice a stringer?

For your stringers, I would HIGHLY recommend wrapping them in 1708 and using Epoxy. As Erik says the structural integrity of the hull is very important and epoxy will ensure you have the best you can provide. You CAN use the Poly but it does NOT work as well with the 1708 Cloth/Mat combo. Your boat is probably made primarily out of poly resin and mat. Just remember this. Epoxy will Stick to almost anything but poly only sticks well to poly and you need to sand and prep it in order for it to stick well. Make sure and get the UN Waxed kind of Poly resin but you will Need wax for the final finish layer or it will remain tacky.

I'm just sayin...

 

[rickryder]

Re: Can you splice a stringer?

Such good advice! I thank you. I am starting to understand better now with the explanations. Doing the splice and epoxy between the plywood and the butt blocks,tab in stringers and wrap in 8oz biax glass and epoxy resin. As for the deck will it be ok to use 1.5 or 2 oz chop strand and poly as long as I do the proper prep work(grinding with 36 grit and washing down with acetone) Of course I would do top and bottom of the plywood deck.

 

[Woodonglass]

Re: Can you splice a stringer?

For a better Looking top I would NOT use CSM but rather a 6oz Ecloth. It will give a much better looking deck. CSM is fine for the bottom of the deck. Poly resin is fine for the deck.

I'm just sayin...