# Questions on using pvc as mold to make fiberglass stringers



## firecat1981 (Nov 27, 2007)

If you go this route, build a jig of sorts to keep everything perfectly straight and true while it's all setting up. I'm sure you know how flexible PVC can be. I wouldn't use a solid piece of PVC cause you will need to fill the huge gap to bond it to the floor, but you can rip a piece of 2" in half which will make it as strong and less of a gap for a smoother transition.

I'm not sure how you will work out the structural bond and strength and still run your lines and somehow drain them so they don't retain water though. Maybe some weep holes near the transom?


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## DuckNut (Apr 3, 2009)

I would skip the stringer. I would use penske/coosa board attached directly to the floor and glassed over.

PVC has proven to be a poor choice with adhesives.


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## mudd_minnow (Oct 13, 2010)

Here is what I was thinking about. The purple is the fiberglass around the pipe. After the fiberglass dries, the pipe is a good chase tube for my wires, fuel line, and water drainage. Between the pvc tubes will be floatation foam. Now, I'm going to put a false floor to cover the  pipes and foam. I want to keep it thin so I'm looking twards fiberglassed luan or mabe just a sheet of fiberglass over top.


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## firecat1981 (Nov 27, 2007)

Problem I see now is multiple fold. First it looks like you will have a lot of trouble draining water from the tubes if they are tied all the way back. Then the PVC has little structural strength so you will need to add a ton of glass to get it strong and it will add more weight then you'd think. 

The way you have it pictured you will need to add a ton of filler to the sides to lay the glass smooth which will make it weaker. Splitting the PVC will lessen the filler and make the total radius larger and stronger.



Really though, and I'm just trying to help, trying to use the PVC as stringer forms will not be as strong as a typical system. Why not cut 1.5" strips of plywood then run a few chase tubes under the floor?


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## mudd_minnow (Oct 13, 2010)

I think what we will be doing is running a chop gun glassing it all in tucking it in rolling it under the pipe, on the sides and on top. Then putting on enouph glass to fill any curves to add strength. Then adding a glass floor.

I thought of doing it like you have pictured but I wanted all the electrical lines, fuel line, and drain line to be seperated, enclosed and easy to run or add new lines through. If you ever had to run an electrical line in pvc you know how difficult it can be with curves. Now try it with half cut pvc lines.


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## firecat1981 (Nov 27, 2007)

The 2" PVC cut in half will have more room to run lines through then the 1" whole, same height but much wider. I ran all my lines through chase tubes in my last few boats, it's very easy to do or add lines after the fact if done right. The 3/8" A1 fuel line might not even fit in 1" so check on it before you start, I had to go up in size.

You can use the chopper gun, but it's really just gonna make a mess of things. It would still be easier and more structurally sound to go with real stringers and chase tubes, plus probably weigh less. If you do go with PVC you will need to add a lot of glass to the tops of the tubes and flatten them out so the floor has support, if you try to just glue it down to the rounded surface it will be prone to cracking. What about just running the chases under the gunnel?

I wouldn't go with luan for the floor, I just did it in my kayak. Even though I glassed it on both sides and the supports are set less then 14" apart it still has some flex. Not a big deal in a yak, but on a boat it would worry me.


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## cutrunner (Jun 8, 2010)

Why dont you rip the pvc in half like firecat stated, wax them and lay they out on a straight sheet of plywood with wax paper. Pop a mold off of them thats about 3-4 layers thick using 1708 . Whallah, you golass those in and you got your stringers


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## DuckNut (Apr 3, 2009)

Agree with the above and in your drawing you have bulkheads that appear to be on the floor as well. That will trap water in each little compartment.

I stand by my earlier post and you can use Cut's method and put them in the bottom corners of the two sides.


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## cwalden (Jun 24, 2011)

Or you could rip the pvc in half, wax and glass the inside. Use the PVC as a negative mold instead of a positive one... Pop them out and then glass to your floor.


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## CurtisWright (May 9, 2012)

I think that is a bad Idea for all the reasons mentioned above. I am with Ducknut. If you want a sollid floor, core it. I would use divynal though, a little lighter and cheaper than coosa. If you wanted to go real cheap, use plywood.


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