polyester over plywood: advise needed

[pescaloco]

Hey guys

My new bare hull came from the builder with plywood bulk heads and laminated cut/screwed/bonded plywood stringer system. The builder is a well respected and skilled builder, but has the old school mentality that is how we do it and plywood / poly is fine

So as not to enter the debate over it should have been epoxy laminated.
It is what it is.

So here is my question is there any advantage for me as the end user and the person that will complete the building of the boat to use higher end materials in the rest of the boat ?

Can I do any thing like over coat the exisitng plywood and poly bulkheads and stringers with epoxy and another lite coat of mat ?? or is that just a waste of time.

Thanks so much this is an issue that has been bugging me for a while

[alan white]

There are a few builders who consider a polyester glass overlay adaquate and from a practical standpoint, they make some sense. Epoxy is very expensive when compared to polyester.
Harold Payson of Thomaston, Maine has for decades built Phil Bolger's small boat designs in poly/glass sheathing and he claims there is a real place for an "okay" method being used in an age of "very good" methods.
He should know, since he's an old-time lobsterman who uses the hell out of boats daily (or at least did).
I've see Mt Desert Isle Amphibicons (25 ft sloops) built in the fifties with ploy/glass sheathing and mat throughout the cockpit--- sole, seats, lazerette) at forty years plus with no obvious delamination problems (though it might have been occurring in places). Still, the skinhj still held and did it's job.
However (here comes the however), A pleasure boat of modern design has a far greater percentage of labor to material cost. The local boatbuilder will no longer ride a bicycle to work and bring his lunch. He's going to charge at least 5 times minimun wage to build a boat by the hour. Labor has gotten very expensive without all of those destitute Europeans migrating to the US and providing cheap labor. Material cost nowadays make up a much smaller part of the finished boat, so the difference between "okay" and "very good" materials appears smaller in the overall picture.
If youi are very practical, and you're building a boat for your own use for ten years, I doubt it will matter which resin you use. Particularly if you are really working your boat and not getting too concerned about minor cosmetics.
People's expectations are a bit strange these days. They would avoid a poly/ply-built boat on the ground of longevity. Then they would proceed to use the boat a total of 30 hours a year and feel that that was heavy use.
Yet, that is the nature of the market today, that you have a hard time selling a boat that is poly-sheathed instead of epoxy-sheathed because epoxy has a perceived "endless" lifespan. Does this make sense? Depends on whether you intend to one day enter that market and either buy or sell a boat.
For a well-used boat (daily work use year in and out), 10 yeas is practically forever.
Your other questions... No, you won't help the situation by epoxying over ployester. It will onl;y add weight and cost.
Regarding whether to switch resins, I think that depends on your finantial situation, and whether you care whether your boat would sell for less on the open market someday.
It won't matter that you are mixing mediums. If sealing the hull is what's left, I'd definitely consider epoxy because in terms of what it provides compared to polyester, the underwater surfaces are most critical to waterproof, and epoxy is many times more effective as a water-sealing membrane.

[PAR]

Alan's right on , though I disagree in one regard. If a fairly durable boat was desired, but resin cost is an issue. Do a final couple of coats with neat epoxy over everything, after you've built with poly. The weight and cost will be minimal and the additional water proofing will help tremendously.

[alan white]

It was epoxy and another layer of mat I was responding to, though I wasn't clear. You're correct, PAR, a coat of epoxy alone adds substantially to the water-proofness.
It's always hard to decide to limit the lifespan of a boat for the sake of a few dollars. Nowadays we tend to err on the side of longevity and zero maintainence. The result is boats are extremely expensive and give back less and less hourly use for every dollar spent. Personally, I'd like to see a few more cheap but worthy boats out there.

[PAR]

I've been working on several designs just like that Alan. These use very little if any epoxy, flat bottoms with constant flare on the topsides means the chine log has a common bevel, which can be gotten out on a table saw in one pass. No 'glass sheathing, no tape, but they're still water tight, without requiring seams to swell up. I'm working on a V bottom too. Think of these as half traditional, half glue and screw builds.

[pescaloco]

Guy's thank you both for the replies I really appreciate it

The extra $$ don't concern me much , I would like to improve or add water proofing where every possible. But don't want to waste money either.

If an epoxy over coating of the poly covered stringers/bulk heads will add re-sale value and longevity I am for it. I will just skip any additional matt

But Alan you absolutely right people these days seem to be of the opinion that if it is not epoxy over the wood it's not good, I know that there have been a lot of good/great boats built with polyester.

As for wanting to to last forever you are right again, most recreational guys will use the boat 5-10 times a year if not 1-2 times and then sell it after a couple years.

To me vinylester for the sole and interior would seem like a good compromise, I would really perfer not to laminate with epoxy.

[alan white]

A good seal with epoxy is usually not possible with one coat. Using a brush, maybe three medium coats will probably be fine. Only wait for the last coat to partially cure (you can still dig a fingernail into it) before adding the next coat to avoid having to sand. This ensures a superior bond.
I haven't used vinylester resin but I'm sure PAR has, so I won't comment.
Good luck with your project.

[apex1]

If it is meant to seal the laminate, Vinylester is not better than orthophtalic / isophtalic resin. Only Epoxy is the way to go.

Alan >>those destitute Europeans migrating to the US and providing cheap labor<<
where do these labourers come from? Most European countries have at least twice the wages of the US. Some even higher.

Regards
Richard

[pescaloco]

Alan,

Thanks for the info on the overcoating.

My original concern is that if the sheathing were to delaminate it would be from the polyester to wood interface. Since there is nothing that can be done to improve that bond, looks like the next best thing is what we have been discussing.

Thanks

[PAR]

Epoxy as a barrier coat will require a few coats as Alan suggested. The industry as a whole has gone away from polyester over wood, which is a good indication of how well it works on wood. Yes, some success stories have come from it's use, but nothing like the horror stories of the failures.

[alan white]

Paul, I think you're onto something and I imagine you'll sell plans right and left if you appeal to the K.I.S.S. and functional crowd. It doesn't make any sense to build your own boat if it's always cheaper to buy a used boat. But design a boat that has good seakeeping qualities and is also within the financial realm of possabilities for the average Joe, plus is buildable, and (like with Bolger/Payson) they will beat a path to your door.

[apex1]

Alan,

Thanks for the info on the overcoating.

My original concern is that if the sheathing were to delaminate it would be from the polyester to wood interface. Since there is nothing that can be done to improve that bond, looks like the next best thing is what we have been discussing.

Thanks

No there´s nothing to improve the bond.
Plenty to improve the ability of holding the water at the right side,(theoutside), and EP is the only way to achieve for a the average amateur builder.
You may love it, or leave it, go with a 3 cover EP layer over the existant layup, or expect to have issues in the future.
Regards
Richard

[PAR]

This is my hope Alan, but no one beat down Phil's or Dynamite's doors looking for plans. Don't get me wrong, they've sold quite few, but didn't get rich off the prospect. I also suspect very low plans pricing had as much to do with it.

[pescaloco]

Three coats it is

Thank you

[alan white]

This is my hope Alan, but no one beat down Phil's or Dynamite's doors looking for plans. Don't get me wrong, they've sold quite few, but didn't get rich off the prospect. I also suspect very low plans pricing had as much to do with it.

Plans cost almost nothing to duplicate. My recent purchase of the Gloucester light dory plans made someone $30.00. They were on blueprint stock.
You won't get rich. It won't cost anything in terms of investment either, as long as you already drew the plans and built the prototype. If a check arrives, run off a copy and slip it in the envelope just like you would a paid invoice.

[rwatson]

Alan,

Thanks for the info on the overcoating.

My original concern is that if the sheathing were to delaminate it would be from the polyester to wood interface. Since there is nothing that can be done to improve that bond, looks like the next best thing is what we have been discussing.

Thanks

A recent article in "professional boat builder" addresses this issue with tests and processes described.

Essentially, you get a far better result if you apply f/g to the ply, let it cure to touch dry, then apply the cloth.

Probably worth a read.

[tunnels]

polyester over wood !! dosent work ok !!! take my adivce use epoxy!!

[rwatson]

I took the liberty of printing a copy of the article in PB, and have attached it.

The article talks about making it easier to apply polyester to plywood, and you can see a guy laying polyester and cloth over what looks like a stringer in the bottom of a powerboat.

Whats more, it discusses this being the engine bay. I wouldnt like to have to inspect the plywood after a couple of years of water and oil sloshing around the bilges.

However, I suppose this type of boat is only ever taken out on weekends, and washed downs and drained lovingly on the trailer, and kept in a garage.

It will probably be ok till the next engine replacement.

PS - note the Ad for the moisture meter on the same page!

[PAR]

Polyester on wood can work, but by the time you apply enough material (fabrics and resin) you pretty much don't need the wood anymore, as it becomes self supporting. No production manufactures that I know, of are using enough are using enough materials to insure durability. The vast majority of these boats don't retain their resale value very well, so by the time their hour meter hits mid triple digits, the boat isn't worth enough to warrant repair, it's just dragged to the land fill.

[mark775]

People read a little or hear someone say something and for lack of a self-formulated opinion, they adopt another's. Next thing you know, it's repeated enough that the concept begins to grow exponentially - a wildfire.
Listen, epoxy adheres far better than poly and if there is a lot of movement and a little moisture where it's not supposed to be, the poly delams. There is poly on some web frames and bulkheads on my boat that has been there since 1979. I, last year, put a layer of the finest cloth I could find over it just to make it look nicer, more even, for painting. I could find no soft spots or delams in >< 64sq.ft. Water, gurry, ice, decades. I prefer to lay the cloth into a tacky second coat of resin - that way you can get the fabric exactly how you want it. If it were on a place of large concern, or l wasn't trying to save money, I'd use epoxy, too.

[tunnels]

Poly over ply has a initial stick but will eventually part off the surface and or take a percentage of the first veneer with it , Wood exspands and contracts and poly also moves but at differant rates . so somethings gat'a give and its the bond or the weakest part .
In the bottom of a boat wooden boat over stringes you are playing with danger!! and its not worth the effort , time ,a exspence , just bite the bullet and epoxy it!!!!You are saving nothing and if it dosent work you have to tear grind and sand and redo it with epoxy !! so why waste your time . :P

I have been seeing these things for more than 30 years where some one comes along with a surposed magic wonderful idea of using poly on wood but it never stands the test of time and falls appart .
If you want to see what works and what dosent go and have a look at a yard that does just boat repairs and you will see first hand all the silly ideas that looked good at the time when first done but under pressure just dont work at all .

[barks]

Epoxy would have been the best solution. Poly will work OK until water (typically rainwater) gets into to wood and starts the rot. If you can keep the water out of the wood it will be fine for many years. If you have a poly covered plywood transom with bolt through fixtures then you will this will rot first. There are many boat repair businesses making a living from repairing 30 year old ply and poly transoms. Stringers should be fine.

[pescaloco]

I P.M.'ed Rwatson about the Pro boatbuilder article and he was nice enought to post a link ( Thank You Rwatson )

The origin of this post is that I own a newly constructed 27ft skiff (HULL) that I bought just hull fitted with poly/plywood stingers 2 bulk heads 3/4 ply sheathed with glass and polyester resin.

I think we all know that epoxy is superior to polyester, but was looking for opinions on the value of epoxy overcoting the existing integral wood parts.

Thanks all

[ondarvr]

I see a tremendous number of production, custom and semi custom built boats and I agree epoxy is a much better product to use over wood. But, I also see a huge difference in the skill of the worker.

Production polyester boats are typically built by workers with little training, are not boaters, have no real knowledge of the products, were trained by the guy that was fired last week for doing a bad job and are only looking forward to the weekend. They are also built to a price point. These boats are rarely maintained in the correct way (sitting in the side yard under a tree with no cover for may years at a time with the plug in). Many times the products (wood, resin and glass) used are chosen for the price (lowest), not how well they will do the job. Some of this has changed over the years, but the mass produced boats of the past were notorious for poor quality.

The typical custom builder has a much better crew that has many years of experience, they have boats of their own, are craftsmen and like what they do. Plus the boats are purpose built with a goal of holding up for many years, showing the quality of construction, are purchased by knowledgeable boaters and while cost is still an issue, doing it "right" is a major concern, so the higher cost is not as much of an issue. Products (resin, wood and glass) are chosen for the best performance in each application and then used with care.

This isn't always the case, but more often than not, it is.

If you were to use the same care and attention to detail with polyester that most wood boat builders use with epoxy, polyester would hold up much better. I'm not saying they're equal though.

[pescaloco]

Ondarvr that is a well though analysis it also happens to be how I feel.

The guy that built my hull has been doing so for 32 years and is a highly skilled craftsman.

I like the idea of additional protection from external epoxy sealing, but like it was said a lot of people take terrible care of their boats and that surly contributes greatly to their early demise. They fill with rain water and leaves, or all the hatches are closed up and no under deck ventilation takes place and a constant cycling of hot and cold builds moisture

[alan white]

You can also check out a WoodenBoat article (I don't have time to look it up)from years ago wherein one Ohio man/company who restored old woodie runabouts had sheathed the bottom of over a thousand (planked!) hulls without any failures except possibly after a good number of years. He describes the method, one he stuck to for decades.
Look guys, Epoxy is king. I liken the comparison of epoxy to polyester as similar to a brick house compared to a wooden-shingled one with boards for trim. We all see that in spite of the absolute superiority of brick, most all houses do not use brick. They use materials that are inferior to brick practically every time. We all know this.
If the old-timers came back to life today, most all (who used boats day in and day out) would use polyester resin to sheathe hulls, decks, roofs, and cockpits. Just like the way they used iron fasteners rather than bronze or copper. Why? It was more practical, just like not building with brick. Ultimate longevity and zero maintainence are paid for by a lot of work doing something else---- earning money to do the job.

[mark775]

Are you going to paint those areas anyway? How about an epoxy paint?

[PAR]

Most epoxy paint is actually polyester. Some two part paints are real epoxy, but so diluted with solvents, nothing compared to the laminating resin we're use to. Epoxy paint also tends to chalk up fairly quickly. You're better of with a single part polyurethane or LPU, for durability, gloss, etc. Epoxy paint isn't a substitute for epoxy coating.

[mark775]

Thanks. A product by Devoe maybe?

[pescaloco]

Plan 3 coats epoxy resin as overcoating, and paint (not sure what paint)
But like the 1 part LP idea, nice and easy

Mark that Devoe paint is pretty good I painted an aluminum tower and it held up very well.

Thanks Alan I will see if i can come across the artice you mentioned