polyester over plywood: advise needed

Discussion in 'Fiberglass and Composite Boat Building' started by pescaloco, Jun 10, 2009.

  1. pescaloco
    Joined: Feb 2006
    Posts: 301
    Likes: 10, Points: 18, Legacy Rep: 81
    Location: so. california

    pescaloco Senior Member

    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
     
  2. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 122, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    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.
     
  3. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 489, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    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.
     
  4. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 122, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    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.
     
  5. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 489, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    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.
     
  6. pescaloco
    Joined: Feb 2006
    Posts: 301
    Likes: 10, Points: 18, Legacy Rep: 81
    Location: so. california

    pescaloco Senior Member

    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.
     
  7. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 122, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    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.
     
  8. apex1

    apex1 Guest

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

    where do these labourers come from? Most European countries have at least twice the wages of the US. Some even higher.

    Regards
    Richard
     
  9. pescaloco
    Joined: Feb 2006
    Posts: 301
    Likes: 10, Points: 18, Legacy Rep: 81
    Location: so. california

    pescaloco Senior Member

    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
     
  10. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 489, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    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.
     
  11. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 122, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    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.
     
  12. apex1

    apex1 Guest

    No thereĀ“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
     
  13. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 489, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    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.
     
  14. pescaloco
    Joined: Feb 2006
    Posts: 301
    Likes: 10, Points: 18, Legacy Rep: 81
    Location: so. california

    pescaloco Senior Member

    Three coats it is

    Thank you
     

  15. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 122, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    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.
     
Loading...
Similar Threads
  1. jwt
    Replies:
    13
    Views:
    2,559
  2. Jeff in Boston
    Replies:
    14
    Views:
    573
  3. Boatface
    Replies:
    14
    Views:
    550
  4. Mark C. Schreiter
    Replies:
    18
    Views:
    1,448
  5. PNW_Dave
    Replies:
    8
    Views:
    1,565
  6. andysailor
    Replies:
    11
    Views:
    1,427
  7. trekker
    Replies:
    23
    Views:
    2,452
  8. Bullshipper
    Replies:
    9
    Views:
    1,774
  9. Greg Vasquez
    Replies:
    2
    Views:
    1,629
  10. burke
    Replies:
    8
    Views:
    9,594
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.