what to bond stringers to hull with

[Ryan]

Just joined the site. Great site. Have a question on what to use to bond fir stringers to fiberglass hull. Alot of different opinions out their. Im redoing a fiberglass garvey and need to redo stringers. Thanks for any info.
Ryan

 

[Eastporter]

I used thickened epoxy (bed) with 1708 biaxial tabbed. Some guys go full fiberglass over wood and this is for strength and waterproofing. I used dry PT pine dimensional lumber and didn't need to worry about rot.

 

[capttom36]

I used thickened epoxy (bed) with 1708 biaxial tabbed. Some guys go full fiberglass over wood and this is for strength and waterproofing. I used dry PT pine dimensional lumber and didn't need to worry about rot.

you are better off staying away from the pine below decks it is not boatbuilding lumber an it will rott out. Try to stay with fur it is stable and will not rot.

 

[Eastporter]

PT = pressure treated with chemicals (copper arsenate)

 

[F/V First Team]

Fir 2x12's fitted to the curvature of the hull by scribe and routed on top to ease the corners, hot coated underside and set into hull and deck putty which is set with a catalyst just below normal mixing ratios and faired, then hot coat the entire surface and encase in fiberglass, going down onto the hull with at least two layers of structure, shingling the layers, first one 3" - second one 6" from stringer.

 

[MDI45]

Eastporter, you can use it for up rights and stuff like that but not for stringers.... the glass will not stick to pressure treated lumber... due to the chemicals

 

[F/V First Team]

Exactly what I thought, if holes were bored through and the epoxy was forced in those to act like staples maybe, I've never had much luck with pressure treated and fiberglass. (what can I say? I was 9 at the time, seemed like a good idea.)

On a related note: Epoxy hates me

 

[capttom36]

stringers

Fir 2x12's fitted to the curvature of the hull by scribe and routed on top to ease the corners, hot coated underside and set into hull and deck putty which is set with a catalyst just below normal mixing ratios and faired, then hot coat the entire surface and encase in fiberglass, going down onto the hull with at least two layers of structure, shingling the layers, first one 3" - second one 6" from stringer.

That is exactly how to install stringers in a down easter.

 

[F/V First Team]

And that's the way it is
​

 

[jawz]

Fir 2x12's fitted to the curvature of the hull by scribe and routed on top to ease the corners nd encase in fiberglass, going down onto the hull with at least two layers of structure, shingling the layers, first one 3" - second one 6" from stringer.

the fitting and scribing is the correct way - the glassing technique is excellent as well

personally,i do not use polyester products - polyester and wood isn't the best choice - polyester resins are pourous,and the bond isn't very strong when applied to wood.epoxy based resins are a much better choice.when drilling the drain holes,it's best to bore the hole larger than what's required,then filling that hole with epoxy mixed with an adhesive additive,fill the hole,allow the mix to kick,then drill the correct size hole - this allows the wood to remain seperated from any water intrusion...

a much better choice for stringers is to use a composite - this eliminates any chance of water intrusion causing a rotting...composites are your friend...

 

[Eastporter]

I did A LOT of research on pressure treated wood in boats and the this is what it said- it has everything to do with the water content in the wood. If it's dry it will stick using epoxy (polyester is not as strong a bond). I did it and it is solid. I built my boat stringers and sole using very dry pressure treated wood. Some professional boat builders use it in stringers, and the APA (American Plywood Association) did extensive research.

http://performancepanels.com/single.cfm?content=app_pp_boat

Boat Builder Central - Howtos

 

[F/V First Team]

The wood is just for a solid core between the laminates where the strength comes from, when a deck is supported from those stringers there could possibly be some compression to be encountered on the wood, but shouldn't be if properly installed. Don't make a leaky boat and you won't have to bore any drain holes

 

[Raider Ronnie]

Fir 2x12's fitted to the curvature of the hull by scribe and routed on top to ease the corners, hot coated underside and set into hull and deck putty which is set with a catalyst just below normal mixing ratios and faired, then hot coat the entire surface and encase in fiberglass, going down onto the hull with at least two layers of structure, shingling the layers, first one 3" - second one 6" from stringer.

Travis,
"hot coated"
Please explain....

 

[Eastporter]

You can make fiberglass stringers without ANY wood and then you don't need to worry about it. I agree with all of you. Money was a factor in my case- composites are the way to go.

 

[jawz]

I did A LOT of research on pressure treated wood in boats and the this is what it said- it has everything to do with the water content in the wood. If it's dry it will stick using epoxy (polyester is not as strong a bond). I did it and it is solid. I built my boat stringers and sole using very dry pressure treated wood. Some professional boat builders use it in stringers, and the APA (American Plywood Association) did extensive research.

Boat & Ship Manufacturing :: Performance Panels :: APA - The Engineered Wood Association

Boat Builder Central - Howtos

there's different treated wood - example: pressure treated wood from home depot...

 

[traditions]

Thats why they make gelcoat.Personally I wouldnt mix the two.If I had a solid glass boat I would keep things polyester.It would be a PITA to glass in stringers with epoxy.The stuff has its uses for sure.

 

[F/V First Team]

Hot Coat - Technical Term
When porous material is used in composite construction, usually a deceased plant medium with varying moisture content, one should first apply resin directly to the surface of that material so that the resin will soak into the material and saturate it so that when one does add a cloth material the porosity doesn't draw the resin away from the reinforcement (fiberglass, carbon fiber, kevlar, the workshirt you were wearing and didn't realize was laying against wet resin, etc). When using foam core it too should be hot coated, not only to fill the pores of the foam but also to go between the kerfs and displace any air so that any water that finds itself in the core cannot spread outside those particular cells - just like balsa core should be installed. Core should be hot coated even if it is going to be bedded into a compound like core-bond.

 

[F/V First Team]

You can make fiberglass stringers without ANY wood and then you don't need to worry about it. I agree with all of you. Money was a factor in my case- composites are the way to go.

I've only done one boat with full-height stringers laid up with solid glass, bit of a pain really to get the entire 20 foot length to be plumb. The stringers put in to take the hull out of the mold were still 2x12 fir though.

 

[jawz]

Hot Coat - Technical Term
When porous material is used in composite construction, usually a deceased plant medium with varying moisture content, one should first apply resin directly to the surface of that material so that the resin will soak into the material and saturate it so that when one does add a cloth material the porosity doesn't draw the resin away from the reinforcement (fiberglass, carbon fiber, kevlar, the workshirt you were wearing and didn't realize was laying against wet resin, etc). When using foam core it too should be hot coated, not only to fill the pores of the foam but also to go between the kerfs and displace any air so that any water that finds itself in the core cannot spread outside those particular cells - just like balsa core should be installed. Core should be hot coated even if it is going to be bedded into a compound like core-bond.

failure to do what you typed often results in a "dry lamination" - for the very reasons you suggested - this step is often over looked...that's the correct way to laminate

 

[F/V First Team]

There was one boat that the owner wanted me to add an antenna to, while drilling the pilot holes for the mount in the side of the house water shot out after going through the exterior skin. Not like a drop of moisture on the tip of the drill bit, but WATER!!! Like the top unit was taking a leak and I was in the way. Later on when the owner asked how to lighten the boat some I drilled a hole in the bottom on a hunch and water started to trickle out.

Luckily for the hull it was foam cored, the top... not so much.

Maybe they should have wondered why they got such a "good deal" on the top and hull from a private seller.