Hull rebuild-Stringer material

[Z992210]

So I am new to the site and the forums have been a ton of help.

I had some leakage last year and started to find rotten stringers, so two days later I have gutted the entire hull and removed all of the water logged foam. I am starting to get the to dirty work of grinding everything down so I can rebuild.

But I am thinking about the next step and the best way to rebuild the stringers, and everything I have seen so far everyone rebuilds the stringers with plywood and applies fiberglass over them to seal them from water.

I am wondering why not use 3/4" thk. PVC sheeting instead of plywood and then having to seal it? PVC will never rot is this not a better alternative and one less step, not having to seal it like plywood? Are there structural issues with PVC vs Plywood?

Any thoughts on this would be great? By the way this is my first re-build so this maybe a dumb question, I could not find anything else related to the subject.

Thanks

jim

 

[tpenfield]

Re: Hull rebuild-Stringer material

I had similar thoughts about using PVC and decided against it. PVC boards get brittle around 40 degrees, and could possibly crack if the boat were used in cold conditions.

There are a couple of alternatives . . . "coosa board" and then you glass over them . . . or there are pre-made fiberglass over foam stringers that you can buy in segments. Either approach will be rot resistant.

Also, PVC boards have a very slick outer surface that would require roughing it up so that resin would adhere, etc.

 

[Woodonglass]

Re: Hull rebuild-Stringer material

We here on the iBoats forum seem to always be searching for that "Perfect" material to restore our boats. It is understandable to a point. However, unless your boat has extreme sentimental value and you anticipate keeping it for your lifetime and the lifetime of other members in your family, I really don't see the point in paying the extra expense for these "High Tech" materials to repair/restore a boat that will not be in your posession in the next 10 yrs. The next owner will benefit from your efforts and you will have the satisfaction of knowing that the boat will have longevity but is it worth the expense to you, to pass this on to someone else's benefit??? Properly prepped, installed and maintained wood in your restored boat, will last for decades. Probably longer than you will keep the boat unless, as previously stated, it's a "Family" thing. I'm not degrading anyone for using these "Non-Rot" materials, I just ponder the thought process. When I found my boat it was 50 yrs old and the transom, deck and stringers did not require replacement due to superior maintenance and upkeep. Other restoration here on the forum are on boats 30 years old or more and although the wood is in bad shape they are still in one piece and some still usable, albeit, not totally safe. I'm sure the glue and wood used in plywood today coupled with the extra care most people take in restoring their boats as compared to what the Factory did, will ensure that if the same care is given to the Wood in your newly restored boat, it will last for that many years or more. If money is no object then I guess use the High Priced No Rot products. But I think for most of us, we are not in that position.

Just my 2?!!!! Add another 98? and you can get a nice cup of Coffee!!!!

The first link in my signature below has drawings for recommendations on how to fabricate Decks, stringers and Transoms.​

 

[ondarvr]

Re: Hull rebuild-Stringer material

^^^ I agree completely.

One more thing. Most people here pick up their first low cost boat and rebuild it, if they like boating they will typically sell it in a year or two and get something better, or more in line with how they want to enjoy boating. Those that don't enjoy boating or because of other circumstances stop using it, end up leaving it under a tree in the side yard for the next ten years. So while building it to last forever seems like a good idea up front, it rarely pays off....oh by the way, when you sell it you won't get anymore money for it no matter how good of a job you do.

 

[idonthaveaname]

Re: Hull rebuild-Stringer material

My 2? agrees with ondavr and woodonglass. great advice. I started out my project thinking of plastics, composites, and all those expensive alternatives. I have ended up with plywood and fiberglass. To me, it's just a boat and an end to a means. I will go fish, have some fun and in a few years after all the work of restoring...it will be time for a new one...maybe. Ten years from now may change my mind. While all that composite stuff seems exotic, I will save my money for fuel, a couple of beers in the afternoon, and tackle. Coffee's free so come on over.

 

[ondarvr]

Re: Hull rebuild-Stringer material

I must admit though, I picked up a boat a little over ten years ago and rebuilt it, I still use it today and currently have no plans to upgrade any time soon. It could easily be another 10 years before I even think of replacing it, or it could be later today, plans and life can change rapidly an unexpectedly.

 

[Woodonglass]

Re: Hull rebuild-Stringer material

Yeah, but if you take care of her, do proper maintenance and upkeep, she'll still be usable 10 yrs from now!!!! I Betcha!!!!

 

[Z992210]

Re: Hull rebuild-Stringer material

Thanks for the input.

I see the little bit of the extra costs just saves the labor to fiberglass the wood so it is sealed. There is also the cost of the glass and resin to use on the treated plywood, I think it kind of balances out in my book,

So the question is: Are there any structural issue with PVC sheeting, is Sintra or Komatex?

 

[tpenfield]

Re: Hull rebuild-Stringer material

Thanks for the input.

I see the little bit of the extra costs just saves the labor to fiberglass the wood so it is sealed. There is also the cost of the glass and resin to use on the treated plywood, I think it kind of balances out in my book,

So the question is: Are there any structural issue with PVC sheeting, is Sintra or Komatex?

I agree, if you are going to do a complete restoration of a boat's structure, I would only want to do it once, so make it permanent. Wood is easy to work with and there is a vast knowledge base of working with wood. So, it is tough to beat in that regard.

The PVC sheeting may work out OK, assuming that you would cut them into boards of the desired dimensions. How they would structurally compare to plywood or dimensional lumber is an unknown. You might be the first to try it !!! I like to see & try new approaches to things, so this will be interesting to follow.

I would check the adhesion, strength and the temperature characteristics, if you can gather that from any material data sheets, etc. You may have to treat the PVC as a core material and wrap it entirely in fiberglass, then glass it to the hull.

 

[ondarvr]

Re: Hull rebuild-Stringer material

The PVC and other plastic lumber have no strength, so you need to increase the amount of glass and resin used to achieve the same strength and stiffness. The bond to it will also be poor, so they would up end just be used as a shape to glass over, what it comes down to is you are spending more money for a core that is nothing more than a shape. You could use cardboard and have the same result.

All of this has been looked at by engineers for a couple of decades "how do you make a better core?" wood keeps floating to the surface of the list. Is it the "best" product...maybe....maybe not...it just depends on the application. But it is probably the most versatile and cost effective product.

My personal preference is no wood, just a hollow stringer with holes drilled so water can flow freely from one end of the bilge to the other. This method is a little heavier, but works well. It is much lighter than the plastic wood route because most of those products are rather heavy, and since you aren’t adding any strength with them the amount of glass will be the same as if it were hollow.

If you aren’t relying on any added strength from the core, then just go back to wood as the shape and don’t count on it for its strength, just use it as a shape. This way if it rots away it makes little difference. This will be lighter and cheaper than using Plastic boards.

 

[Bob_VT]

Re: Hull rebuild-Stringer material

Thanks for the input.

I see the little bit of the extra costs just saves the labor to fiberglass the wood so it is sealed. There is also the cost of the glass and resin to use on the treated plywood, I think it kind of balances out in my book,

So the question is: Are there any structural issue with PVC sheeting, is Sintra or Komatex?

You bet there are. Do your internet homework and read up on the glue tests, cold weather and heat.

Bottom line - it is not meant for marine structural use.

Good luck.

 

[Z992210]

Re: Hull rebuild-Stringer material

Ok, I will take a look.

So if I went with plywood, it would not be worth spending the extra cash for the treated lumber then either, regular ply is ok then?

 

[ondarvr]

Re: Hull rebuild-Stringer material

You can buy treated KD plywood designed for this type of use, it's what most boat builders use.

 

[Scott Danforth]

Re: Hull rebuild-Stringer material

I would go with ACX. treated lumber requires drying it before you can use it.