Pouring foam in stringers

[loxboy1]

I have a 96 angler walkaround cuddy. Termites got ahold of it and ruined the floor transom and stringers. For family and paperwork reason i cant get rid of it, and cant afford the boat i want so repairing this one is what im going to do. Now ive been in the marine indusry for a while now, mostly warrenty tech for new yacht sales but ive done fiberglass work so i know about how to do the floor and transom. As for the stringers, when i cut open the floor i was thinking about cutting open the tops of the stringers gutting them out and pouring foam into them then reglassing the top closed then proseed to soing the floor.

What yall think

 

[DeepBlue2010]

IMHO, Stringers that were designed to be wood-cored needs the wood for strength and structural integrity. If you are looking into a poor in solution, consider NIDA core or similar product not foam. But those are significantly more expensive than plywood. If it for stringers only, your quantity needed could be small enough not to burn a big hole in your wallet.

 

[Scott Danforth]

if you already have the deck off, it is actually about 3X more work to try to carefully cut the tops of the stringers, level them off to the correct thickness for the exact thickness of glass you plan on using to cap with, clean out the termite riddled wood, then grind the sides of the stringers to get a proper tabbed cap layer to stick than it would be to simply cut the bad stringers to the hull, grind the hull and start over (proper gut & rebuild).

 

[fhhuber]

If you do as planned and just foam fill... cut the max HP by 3/4. Your hull will be weak.

 

[JASinIL2006]

My boat has foam-filled stringers and bulkheads. They look very different from most wood-filled sturctures; the engineered stringers are about 3-4 times as wide (mine are about 3 1/2" wide) and the fiberglass is really thick, much thicker than the usual you see recommended for wood stingers. That extra fiberglass no doubt is to make up for the lack of structural strength contributed by the foam (relative to wood).

I think Scott Danforth is right: you'd be facing less work to just replace the structure you have than to try to create foam-filled stringers.

 

[Woodonglass]

How wide are the existing stringers? How thick are the existing fiberglass channels walls?

 

[loxboy1]

The reason i thought foam was because a guy i worked with who used to build boats, made foam stringers when he built a centerconsole out of a 233 formula hull. My issue i think im going to have is getting access to the sringers under the cabin.

I havent given it a real hard look yet, i guess ill see when i cut the floor open this weekend

 

[Woodonglass]

Here's what you need to understand. If you want to use Foam as the core structure for your stringers then the side walls would need to be a minimum of 1/4" thick since the core would not be able to sustain any of the load the Glass would need to be substantially thicker than normal. That's why the Mfg's use wood It's a LOT cheaper than Glass and faster. I seriously doubt that the existing stringer walls are anywhere near this thick or of a quality that would be capable of being capable of being able to carry the loads needed for your boat. Post some pics of your boat and we'll be able to assist you with your project a lot better.

 

[DeepBlue2010]

100% fiberglass stringers formed over foam are totally different design all together than a wood-cored stringers. It is true that the walls are much thicker but there is much more to it than just that. The stringer turn into an I-Beam element after installing the deck on top of it. The strength of I-Beam is - in part - a function of the strength of the web (the stringer in this case) a good amount of modeling and calculations go into determining the width, thickness and the height of the web (the stringers in this case) for different stringers design and boat hulls. This will be done by a naval architect during the modeling phase of the design. So, please don't make an invalidated assumption that if you increase the thickness of the walls to a 1/4 you will have a strong enough stringer to support your boat; you will be rolling the dice. I would redo it the way you found it or pour in a structural pour-able core.

 

[Woodonglass]

I-Beam??? Not sure I follow. Foam Cored stringers have been made by various MFG's in a myriad of configurations over the years. I might have seen some I-Beams but can't recall. Regardless of the design of the stinger the glass is what will be carrying the load and not the foam. It's just the mold for the glass. As previously stated to make foam cored stringers is usually a cost prohibitive proposition and usually not something the DIY'r would want to undertake but...It's totally up to the individual to make that decision.

 

[DeepBlue2010]

The stringer turn into an I-Beam element after installing the deck on top of it.

Are you following OK now?

 

[Skypirate]

Its tough to make a strong suggestion for structural integrity without seeing what is at hand, using what was previously presently in earlier posts, is it possible to remove the complete " cap" on the stringers then fabricate a laminated beam to insert into the fiberglass then re cap after voids were filled with new glass? If its possible, you could " paint" the inside of the voids with epoxy prior to inserting new wood stringer then cap with glass,.. Just a thought

 

[DeepBlue2010]

Its tough to make a strong suggestion for structural integrity without seeing what is at hand, using what was previously presently in earlier posts, is it possible to remove the complete " cap" on the stringers then fabricate a laminated beam to insert into the fiberglass then re cap after voids were filled with new glass? If its possible, you could " paint" the inside of the voids with epoxy prior to inserting new wood stringer then cap with glass,.. Just a thought

Creative thinking! Unfortunately the end result would be weak because the fiberglass walls are mostly de laminated (de attached) from the wood. Maybe if he pre-coat the wood with epoxy and pours in a some epoxy resin along the length of the channel then insert the stringers letting all the epoxy on the bottom squeezes up on the sides then clamp the side down with C-Clamps. This will take care of any voids too. Just thinking out loud. I still think it is easier to reglass a new one or pour in structural core. But, it is not my call

 

[Scott Danforth]

Creative thinking! Unfortunately the end result would be weak because the fiberglass walls are mostly de laminated (de attached) from the wood. Maybe if he pre-coat the wood with epoxy and pours in a some epoxy resin along the length of the channel then insert the stringers letting all the epoxy on the bottom squeezes up on the sides then clamp the side down with C-Clamps. This will take care of any voids too. Just thinking out loud. I still think it is easier to reglass a new one or pour in structural core. But, it is not my call

See post #3

 

[DeepBlue2010]

if you already have the deck off, it is actually about 3X more work to try to carefully cut the tops of the stringers, level them off to the correct thickness for the exact thickness of glass you plan on using to cap with, clean out the termite riddled wood, then grind the sides of the stringers to get a proper tabbed cap layer to stick than it would be to simply cut the bad stringers to the hull, grind the hull and start over (proper gut & rebuild).

What exactly are you pointing me to Scott?

 

[Skypirate]

Seems post #3 has explained the process of replacing the Stringers, I missed it earlier

 

[DeepBlue2010]

I see

 

[Woodonglass]

Another option is to use the existing stringer channels with the addition of supplemental framing on the exterior sides to extend the height to where they need to be and pour SeaCast or one of the other similar composite pourable materials suitable for making stringers. It's a bit pricey but very strong. Some members in the past have done this with good results.

 

[DeepBlue2010]

What a great idea!!! Totally different than what I mentioned in almost every reply I posted in this thread. Now,

 

[Woodonglass]

It was wasn't it!!! I'm SOOOO Glad YOU Thought of it!!! This is just another GREAT example of why I continually tell everyone I'm just and Old Dumb Okie. It's quite obvious I can't retain what I read for more than a few minutes soooo I guess Old Timers is defintely setting in!!!:facepalm: