fiberglass and waterproof wood glue

Discussion in 'Wooden Boat Building and Restoration' started by 300wm, May 4, 2016.

  1. 300wm
    Joined: Jul 2014
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    300wm Junior Member

    For small boats such as kayaks and such, I'm curious to know if anyone has used or tried using water proof wood glue with fiber glass for holding seams together. I've noticed while taking a kayak apart that had splices in the plywood using water proof wood glue that it tore the wood apart trying to separate it. Also, places where the glue ran, I had to chisel the glue off. Wood is 1/4'' exterior pine and glue is Elmer's Wood Glue Max.

    Sorry this is so trivial, but someone work with me, please.
     
  2. messabout
    Joined: Jan 2006
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    messabout Senior Member

    If the kayak was made from quarter inch pine ply, it was brutally heavy.

    Perfectly matched joints can be reliable with such stuff as Titebond or other glues of the type. Note the qualification, perfectly matched. That kind of glue is not an appropriate gap filler so that is why the powers that be gave us epoxy.

    The difference in cost, for a kayak, between Titebond or similar, or the alternative epoxy, is too small a difference to be considered worthwhile.
     
  3. PAR
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    PAR Yacht Designer/Builder

    Elmer's Wood Glue Max is a PVA and passes the type 1 WBP test, but like others of its type (TiteBond III for example) it just barely passes this test. It's also not considered a structural glue and not capable of prolonged emersion. This type of glue is used in strip planked hulls, were tightly fitted and clamped joints can be expected (as previously mentioned above). It has no gap filling properties, tends to creep under load, but the typical strip planked build will usually have a epoxy set fabric sheathing, which serves to protect the PVA glue (it's really an adhesive). In short, I use these PVA's quite a bit, but never on structural, heavily loaded or under the LWL areas. Yeah, once dry, a drip or run is a pain in the butt to remove, but a scraper does a good job, if used with care.
     
  4. 300wm
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    300wm Junior Member

    My third one, fully completed, is 79lbs (18' X 22.5"). I didn't go overkill in the stringers and bulkhead braces and used smaller screws. First was a learning project that weighs 102lbs fully rigged. None are fiber glassed. I just wanted to put everything together (on 4th boat) with wood glue and 3" wide fiber glass....no screws anywhere except attaching the deck. Drilling all the holes and then counter sinking...and then filling is a major hassle.
     
  5. PAR
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    PAR Yacht Designer/Builder

    Not for nothing, but that's a damn heavy canoe or kayak. I just sheathed one for a friend, who built one of my 16' designs and it weighs just less than 30 pounds. What are the strip dimensions on your 18'?
     
  6. 300wm
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    300wm Junior Member

    Please forgive, but I don't understand what you mean by 'strip'.
     
  7. PAR
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    PAR Yacht Designer/Builder

    I assumed this was a strip planked canoe/kayak, but maybe not. What is the construction method?

    To directly answer your questions about wood glues with 'glass fabrics, well no they don't work the same way as the usual resin systems we use with these fabrics. You can use a PVA as a deck sheathing (for example) with 'glass and other fabrics (cotton, polyester, etc.), but they're not nearly as durable as the "usual suspects".

    Can you post pictures of your concerns/issues?
     
  8. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    To give you some idea, when I built racing rowing shells in cold moulded veneer, the weight with everything (riggers, seat etc) was well under 30lb (13.5Kg). Now those are 27+ feet (8.25m) long, but of course narrow and not glass sheathed. Skin thickness was under 1/8th" (3mm), though of course you almost never touch it, as you are supported by the seat and foot board.

    The old Ottersports Eskimo Kayaks in 1/8"-5/32" ply, stitch and glue and at around 17 feet were similar weight or lighter, when finished. These were well up to sea work.

    Strip planking is a method of construction joining thin battens together on edge to form a hull shape. Usually done over a number of formers, some of which may be internal bulkheads. Can also be done on a faired polystyrene temporary internal mould, though a polythene sheet cover is advised. It maybe necessary to pin or staple strips at the ends, or to bulkheads, whilst the glue is curing but most or all are removed later. Depends on internal hog if used and stem and stern posts.

    There are several fully waterpoof glues which are well up to joining good tight scarf joints and tight strip plank construction.PVA is not one of them IMHO, I only use it for jigs or things I want to take apart later with heat and steam.

    There should be almost no need for screws, except maybe in special areas with high loads in the construction of a kayak (Eskimo style) or Canadian style canoe. The latter will need a thicker skin if it is also the floor you stand on. Some notching and 'spreading' of glue area should be incorporated in the design. Scarfs at 1:7 + will not fail generally unless the glue itself is very very old say 35-40 years +, depending on type. I don't quite understand the 'taking splices apart'? I assume scarf joints?, they are not meant to come apart and the glue should be stronger than the wood. Only stuff put togeter with 'pearl' or 'hide' glue is meant to come apart - think violins and antique furniture...;) You don't need fibreglass in a wood to wood clean joint, unless you need a gap filling capability - poor joint or say a wood to rough fibreglass bond. In fact the joint, if clean, is better without any 'filler' on wood to wood, and best if both faces are clean planed or scraped.

    If you are having trouble with spring back of the timber, your sections are probably too thick for this type of craft. Maybe also poor design detailing, or with respect, poor execution of the joint.

    I'm with PAR on this one. But also check the weight (density) of the timber being used. WR Cedar is approx 0.37/8 and your pine is somewhere about 0.45/6?- more if not fully dry. The Cedar would require sheathing but has proven durable in many, many craft of this ilk.
     
  9. 300wm
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    300wm Junior Member

    This is the first boat I did at over 90lbs. I've cut it up so that I can redo it using the existing tub, but the scarf joints, as you say, had to come apart in a couple places. It did tear the wood up, some.
     
  10. 300wm
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    300wm Junior Member

    PM sent.
     
  11. 300wm
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    300wm Junior Member

    Finally got a day off where I could work on the thing. Yes, all joints are matched and everything is 90 degree angles. It basically looks like a long shoe box pointed at each end. The deck, hull, and sides are each one piece when everything is spliced. I just set the hull on the leveling pads and tack together with finish nails. The 90 degree angles are what I wanted to use the fiberglass and wood glue for...to attach like you would with resin. I am now looking at cotton canvas to use for this instead of fiberglass. Admittingly, just doing one side is not strong 'cause the water glue flexes too much when cured, but when everything is together, it is one solid unit, at least with the screwed in strips. That's what I'm trying to get rid of doing.
     
  12. 300wm
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    300wm Junior Member

    Here is what I want to do with the canvas and wood glue, but only on the interior. All the exterior edges are slightly rounded off and any small gaps are Bondoed.

    http://www.jimsboats.com/webarchives/2001/joint6.gif

    Keep in mind all angles are 90 degrees and there are no large gaps to fill. Glazing putty actually has worked the best and is easiest on last two builds.
     
  13. PAR
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    PAR Yacht Designer/Builder

    Yeah, this has been tried and it doesn't work for several reasons. PVA's aren't gap filling, haven't the modulus of elasticity necessary, tend to creep under load and tend to soften when immersed. Cotton is dramatically weaker (in every regard) to 'glass fabrics and though it more closely matches the modulus of the PVA, still isn't something to consider.

    Do some tests, fillet and tape a small piece of 1/4" plywood at 90 degrees to another, with both epoxy/'glass and PVA/canvas and see how they rate. Make several samples, so you can toss a few in a bucket of water for a several hours (like an afternoon on the water), then pull them out for testing.
     
  14. 300wm
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    300wm Junior Member

    I built a shoe box (without a lid) 3 days ago using the 'Max' glue and 2" wide strips of denim. I thinned the glue a little to get it to soak in the denim, better, then put it over raw glue. It really set in, nicely, and was easy to get pushed in the corners. Pulling on it, now, it has no give and I can hear the wood trying to crack under pressure, but the joints aren't moving. I'm going to knock one end off with a hammer to see what it takes to get it apart.
     

  15. 300wm
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    300wm Junior Member

    Took some force to get one end off with a common construction hammer. I tried to get the denim to tear in one corner, but all it did was pull free from the wood taking a lot of the surface wood with it.
     
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