Gorilla Glue vs 2 part epoxy

Discussion in 'Wooden Boat Building and Restoration' started by bjl_sailor, Sep 13, 2004.

  1. bjl_sailor
    Joined: May 2004
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    bjl_sailor Junior Member

    Hi:
    I am about to start laying up a 19' sport sailboat using 1/2" thick x 3/4" wide bead and cove red cedar strips. The boat is a broad hulled planing sport boat design with an integral luan keel and stem. It will be laminated with either e-glass or carbon fiber on both inside and out. My question is, has anyone used the so called 'gorrilla glue' for this purpose. It is a 'waterproof' one part polyurethane adhesive. I expect the wood and glue to be fully encapsulated in cloth and expoxy before it touches water. Previously, when building smaller strip canoes and kayacs I have merely used carpenter's glue and in this project would like to avoid the messy and expensive process of hand measuring, mixing and applying epoxy to laminate the bead and cove strips over the forms...
     
  2. Ilan Voyager
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    Ilan Voyager Senior Member

    You can use a monocomponent polyurethane glue, let it cure completely (1 week) and to seal in Epox.

    A remark; for a planing sailing boat of 19 feet the scantlings are enormous. A 3/8 thickness, or even 8 mm seems largely sufficient with a 6 oz glass cloth.
     
  3. bjl_sailor
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    bjl_sailor Junior Member

    K-19 strip built sport boat

    http://www.nwmarinedesign.com/k19.htm

    I'm going by the schedule on the designer's plans. The boat could be done with either cold molded plywood or cedar stripping -- which I have done before. It also has 6 1/2" okoume bulkheads to be tabbed in. You concern about weightiness is also one of my prime concerns -- but I also don't want a materials failure. I've found a site that offers a carbon fiber /kevlar composite fabric -- at $20.oo per yard not cheap but I'll glass the interior with it and than use e glass and the new west clear epoxy so I can finish brite... In terms of weight considerations -- the boat is supposed to wiegh in at 490 pounds -- we'lll see...
     
  4. duluthboats
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    duluthboats Senior Dreamer

    "I'm going by the schedule on the designer's plans."

    Good idea for the fabric also. Unless needed I would avoid the kevlar, it can be a nightmare to work with. If the boat will spend most of it's life in the water I would edge glue with epoxy. If it will live on a trailer than gorilla glue or even tite bond 2 will work.

    Gary
     
  5. Ilan Voyager
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    Ilan Voyager Senior Member

    If the boat will spend most of its time on the trailer, I understand now the scantlings (it's built like a tank...) which purpose is to stand up the stresses and deformation induced by the trailer, and putting in and taking out of the water. It's sure that the K19 will last: on your death bed you'll give it to your grand-grand sons (I'm joking).

    Don't touch kevlar; it's the worst thing to cut, it's difficult to wet and it's impossible to sand unless you cover it with glass... Carbon cloth is useless on a such small boat with so generous scantlings (a 40 feet race catamaran has the same scantlings...) and it's very difficult ro wet. Carbon breaks very easily at hitting and covering with this fiber a hull destined to be trailed doesn't seem to me as the best idea.

    Stay with glass, cheap, easy to wet, easy to repair which will withstand all the small miseries of a trailed boat far better than carbon.

    Even local carbon UD has not purpose when you have 1/2" bulkheads. The designer took this scantlings to get a strong boat with cheap materials.

    Unless you're planning a drastic weight reduction, exotic fibers are useless.

    I confirm you can use monocomponent polyurethane if you encapsulate well the hull skin after with epoxy. I understand perfectly that polyurethane flowing directly from the bottle is simpler that mixing epox.
    However think that your carpentry will have to be perfectly fitted as the polyu has not the same qualities of gap filling as epoxies.
     
  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Wow, this thing is built.

    Classic method using the wood as the structure and the 'glass work as an abrasion skin to protect and waterproof the materials used in construction.

    The 'glass work does little, as scheduled, to strengthen the structure. Increasing this is rather unnecessary, using fancy fabrics as well. As Ilan has pointed out, you'll need much better wood working skills using other then "wood butcher's friend" epoxy.
     
  7. tonyr
    Joined: Oct 2003
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    tonyr Junior Member

    Glue for strip planking.

    I have used PL Premium (a one part polyurethane) for this purpose. It is stronger than the cedar I built with, and reasonably gap filling. It apears to be completely waterproof from my testing. It is CHEAP! I particularly like its long open time - makes for a relaxed fitting and screwing/nailing of the strips to each other. I think it is entirely safe in this application provided that you cover the hull with enough epoxy and fibreglass, outside at least, and perhaps the bilges inside.

    Tony.
     
  8. Ilan Voyager
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    Ilan Voyager Senior Member

    I agree with you that polyurethane glues are "confortable" to use, when working alone it's relaxing.

    But I'm not so sure that waterproofness will last for a long time. Some years ago, polyurethane glues and resins have been tried for coating and gluing, and it was a failure. As I know, most of polyurethane glues don't pass the RINA boil test.

    On a bigger boat gluing with epoxy is mandatory.

    Where I do not agree with you it's to no coat the boat inside, or just maybe the bilge.

    It's exactly the contrary on a boat which spents most of the time on a trailer. Exterior will dry and in theory a paint is just enough, but the inside is always humid and without aeration will begin to rot, apart the loss of strenght and checking; the boat's inside is the first part to coat, and 6 rolled coats of epoxy are not a luxury in the bilges, where you have always water, from the sea or from condensation.

    The lone rational technique is to coat the both sides, so the wood will remain dry and stable. Cost of epoxy is low compared to the boat's cost.

    There are a lot a good thin epoxies for boats, and on the basis of dry matter, they are cheap compared with paints; naval epoxies have no evaporating solvent, so when you put a pound on the hull, you'll have a pound of coat and all defects are filled.

    Painture may contain until 60 % of solvents...try to fill a pinhole with paint and you'll see. After drying the pinhole is always there. You buy a pound and only 1/2 pound remains on the hull.

    The US Forest Industry Laboratory made very interesting trials for protecting the wooden bridges, and it appears that epoxies are the best known moisture barrier just after the paraffin wax..
     
  9. pungolee
    Joined: Jun 2004
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    pungolee Senior Member

    The Company I work for formulated the original Polyurethane glue,it was known as U-Bond back in the day.Since then,many improvements have been made to the original formulation that has increased its user-friendliness.All of the current products are made by one or two manufacturers to the same specs,just packaged in differently labeled tubes and bottles.Here is the rub on Polyurethane glues.They cure by moisture.To get the best adhesion the joint must be free from any residue,preferably raw wood.Get the freshest product you can,look at the Use by date.Pick a bottle that looks clear,if it has a cloudy ring at the top of the fluid pass it by.Some woodworkers squeeze a sponge over the joint,this hastens cure time and expands the glue to fill gaps.DON"T DO THIS ON A BOAT.With these glues you want a long drying time,free from excessive humidity.In many ways a Poly is more difficult to use than an Epoxy,if you want a strong joint.Properly used I believe it makes an incredibly good joint.A sharpened,beveled putty knife makes fast cleanup of the run-out.Glass over the whole mess will be that much nicer,but Kevlar is rough to work with.Take care.
     
  10. jalexfolds
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    jalexfolds Junior Member

    I have never used gorrila glue in boat building but use it in furniture building all the time. My one comment is that it expands ALOT. It can eaisly push a joint apart.
     
  11. D'ARTOIS
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    D'ARTOIS Senior Member

    Gorilla Glue

    Make sure that you never use polyurethane glue on epoxy surfaces and vice versa. They 'bite' each other!
     
  12. JEM
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    JEM Senior Member

  13. tonyr
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    tonyr Junior Member

    D'Artois. What problems have you had getting epoxy to stick to a modern PU (such as PL Premium)? It has worked just fine with me.

    Tony.
     
  14. D'ARTOIS
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    D'ARTOIS Senior Member

    Glue

    As I say, we were producing a small dayracer back in the late '80 s when my collegue showed me something we had not expected. This was the first or at least one of the first all epoxy impregnated boats in Holland. For costs reasons some fittings and stringers were glued with PU on the epoxy surface.
    Then a chemical reaction between the epoxy impregnated fiberglass skin and the PU glue had begon. Personally I would never had used two different glue types in a construction, but anyhow, it was the case. So that's what has happened.
    You have a similar problem with 2nd bonds on fiberglass. Epoxy holds beautifully on polyester imregnated fiberglass, but not vice versa.
     

  15. tonyr
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    tonyr Junior Member

    D'Artois - it may be that like the polyester on epoxy behaviour you mention (with which I agree) some polyurethanes do not stick well to some epoxies, and possibly vice versa. I suspect that it may not be universal with all modern formulations, so some testing in each case would seem sensible.

    Tony.
     
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