PL and Epoxy on the same project?

Discussion in 'Boat Design' started by Russ Kaiser, Aug 7, 2011.

  1. Russ Kaiser
    Joined: Jul 2009
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    Location: Winston-Salem, NC

    Russ Kaiser Exuberant Amateur

    Steve W, I don't like working with polyester because of the fumes. I am working in my attached garage. Polyester would definitely be cheaper and cure more quickly though.


    Building with chines has some appeal; nice and strong. The tapered sides of this design make chines a little more complex, but I could just build two of the flat bottomed, vertical sided Gavin Atkins designs, or something like Bolger's punt and forget about fillets altogether; definitely something to consider.

    Well, this has been a great thread and it seems like if I want the new boats to be as good as the first two and use the same design, I need to build them the same way. It will take a little longer, and take a bit more resin, but there isn't really a sand-able glue that can be used to make the interior fillets.
     
  2. Steve W
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    Steve W Senior Member

    rwatson, you're right, gluing of the edges of the plywood in stitch and glue construction is pretty much a non issue, it's the fillet and glass taping that holds it all together. When i build in S&G i do use hot melt,not in place of wiring it together but to supplement it as i dont bevel the edges at all, so i wire it every 6" then use the hot melt to hold things in line anywhere it may need it, it gets buried in the fillet and glassed over. 30 years ago we developed a line of 13 S&G boat kits for a company called Country Ways in Minnetonka, they had bought the rights to the line from a British company,Bell woodworking i think, anyway they imported a kit of each model, they were mostly Jack Holt designs but not particularly good kits so we refined them into very accurate kits that we could mass produce, remember this was before CNC routers. So,the original kits that came from the UK came with monofilliment fishing line to lace the panels together and polyester resin for the glassing, we converted to copper tie wire and epoxy resin but i have no doubt the polyester would do just fine as a cheaper (though obviously not as good) option with the added advantage that you can buy both the filler and resin at auto parts stores and even K mart or Wallmart in anytown USA and im sure most other developed countries.
    Steve.
     
  3. FAST FRED
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    FAST FRED Senior Member

    Polyester would definitely be cheaper and cure more quickly though.

    Polyester resin is NOT a glue .

    As a laminating resin ,its just fine , but as a glue, no way.

    FF
     
  4. Steve W
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    Steve W Senior Member

    No Fred polyester resin is not a glue, but FOR THIS PURPOSE it is more than adequate and if you use a good body filler to fillet two pieces of 1/8" or 3/16" plywood together you will rip the veneers apart seperating them, even before you apply the glass tape,its a function of the bonded surface area. Some people on this forum tend to lose sight of the fact that not every application requires the bond strength of epoxy. As i pointed out before, there are many many many many many more stick built fiberglass boats around the globe with their plywood components tabbed in with polyester resin than epoxy resin and for the most part they are just fine.
    Steve.
     
  5. rowerwet
    Joined: Nov 2011
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    rowerwet Junior Member

    I have currently built four of Gavins mouse designs, three using chine logs and PL and one using epoxy and tape on the seams only, except I did glue the decks to the air boxes on with PL, the epoxy boat is much lighter and was built much faster, PL is heavy and the chine logs add even more weight. I didn't bevel anything on the micro-mouse, square-mouse, or romana, the PL fills the gap and saves that step. I did glass the outside corners on the bottoms of all four boats though to protect the edges of the superply. I will not be building with PL again unless the kids are doing the assembly on the boat.
    PL is still a little rubbery when cured so if sanded it clogs the paper rapidly, the working time is about a half hour, drying time is measured in hours, so you have to cut label and then double check that your clamps or screws are still holding things in alignment after an hour or so. I have never tried bedding glass into it but have read of some who have used drywall fiberglass tape as it impregnates the looser weave better, the more you work PL the worse it foams, I just laid in the fillet thick with the caulking gun and then rounded it off with a spatula. instead of tying the panels together I used gorilla tape, which may not work on more tortured shapes.
     
    Last edited: Dec 1, 2011
  6. Collin
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    Collin Senior Member

    If epoxy price is an issue, I'd change building methods. By the time you do all those fillets and glass, you spend more on glue than wood.

    You can build designs using chines and Titebond 3 much quicker than epoxy and glued sitches. The kids can even help you with that glue since it's water clean up and non toxic.

    The only downside is that chine construction means a more boxy look. But that doesn't change the fun you have with it. Box-boats are the most fun you can have.

    PS. Gorilla glue is one of the worst glues. The joints don't last. They begin strong and quickly degrade until they fall apart. The glue can only fill gaps cosmetically, it gives no strength.

    [​IMG]
     
  7. pistnbroke
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    pistnbroke I try

    at the very end of the Hannu's boatyard site is an analysis of all the tube glues and boil test .....http://koti.kapsi.fi/hvartial/index.htm page down to "construction glue for boatbuilding"
     
  8. BPGougeon
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    BPGougeon Junior Member

  9. pistnbroke
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    yes and I bet its real cheap too .........
     
  10. CutOnce

    CutOnce Previous Member

    I've built two hard chine boats of the exact same design - one with PL Premium and the other with West System epoxy. The PL boat is heavier, quite a bit rougher in finish and certainly won't last as long.

    The epoxy boat costs probably half again as much, will last years longer and is yacht-club nice.

    PL doesn't like any contact after it comes out of the tube - any touch and it bubbles - even if all you are doing is smoothing a joint like a fillet. Basically, touching PL probably degrades the joint hugely - as the smooth surface become porous immediately. I'd have to test to completely confirm this, but by my eye it looks 100% right. PL isn't really sand-able to a usable finish.

    This is one of those choices everybody has to make - since my time is valuable and can be spent generating revenue in excess of the savings possible by using PL Premium, I personally choose epoxy over tube glue because the time spent waiting for PL to cure costs more than the difference.

    Your own math may vary.

    --
    CutOnce
     
  11. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    just found it $21.45 for 190 ml ...now thats real cheap ...I think not ....joke product
     
  12. CutOnce

    CutOnce Previous Member

    As I said, it depends on the value you place on your time. I can bill work hours at a rate of a few tubes of this stuff per, therefore the time saved working on the project is worthwhile. For me it isn't a joke - although I can see how for many people it is.

    I was next to a Chesapeake Light Craft team build at a Woodenboat Show a couple years ago, and I watched 8-10 zero experience teams build quality boats in two and half days - and the tube epoxy was a big part. No mixing, no waste, no problem laying a perfect sized bead for a fillet and no delays. For professionals or people with free time, I agree that the tube epoxy isn't worthwhile - but for many folks it is dirt cheap.

    It is important to remember that opinions are a matter of perspective, and although I hold strong opinions, I'm more than willing to accept that others may see things very differently than I. And that from their perspective, they may be also correct. I can't imagine PAR using a West System tube epoxy - but I do think that many people probably would be better off if they did.

    --
    CutOnce
     
  13. Dave Gentry
    Joined: May 2010
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    Dave Gentry Junior Member

    PL Premium construction adhesive, that comes in a tube and is used with a caulking gun, is an OK substitute as a glue, in some limited uses, for thickened epoxy. However, it is not suitable for what you seem to have in mind.

    1) Yes, you can form "fillets," but they will not be structurally sound. In fact, you could peel them away with your fingernails after they have cured.
    2)Answered.
    3) Yes, but barely. It's very rubbery.
    4) The epoxy would still stick to any wood around the PL residue.

    PL premium glue (that comes in a squeeze bottle), Gorilla Glue, etc is not suitable for boatbuilding. It requires near perfect mating surfaces and good clamping pressure and still has poor performance in a marine environment. Furthermore, any foam that you see is mostly AIR, of course, and while it may fill a gap, it certainly won't be providing any structural strength. You may as well just put some clear tape over that gap.

    Thickened epoxy can be had in extremely convenient tubes, yes, and I love (using, not paying for) it. It's a little thin for fillets, IMO. And, it's ridiculously expensive and you need to use it all at once, or invest in a number of mixing nozzles. Alternatively, you can mix it by hand, once the original nozzle has cured into a solid 6" sculpture.
    The 6/10 tube epoxy I have used hardens in a few hours, not minutes.

    If you are building a truly "disposable boat," then there's no real reason you can't use polyester resin and bondo. Check out Jim Michalak's latest newsletter for his experiences and results with taped seams and polyester resins: http://jimsboats.com/

    Good luck!
    Dave Gentry

    www.GentryCustomBoats.com
     
  14. Collin
    Joined: Nov 2011
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    Collin Senior Member


    For a skin on frame boat, that tube would last me the whole build with extra!

    Oh, wait, How many ml are in a gallon again? lol
     

  15. oldsailor7
    Joined: May 2008
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    Location: Sydney Australia

    oldsailor7 Senior Member

    Shucks Guys. :rolleyes:
    Just bite the bullet and use a good boat building epoxy.
    Bote-Cote is the best one in AUS and MAS is a good one in the USA.
     
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