new fiberglass cloth PL Premium polyurethane idea

Discussion in 'Wooden Boat Building and Restoration' started by sdowney717, Jun 17, 2012.

  1. sdowney717
    Joined: Nov 2010
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    sdowney717 Senior Member

    I use a lot of PL premium polyurethane construction adhesive.
    I had a formed plywood desk chair base that disintegrated, mostly due to poor design strength, IMO.

    So I took some FG tape, the kind you use for drywall.
    And I covered both sides of the chair bottom plywood with strips of FG tape and used a putty knife to spread PL into the tape.
    I reinforced the broken area with many layers of FG tape and PL.
    It turned out great. The PL set up fast, and had to go over a few times with plastic putty knife to press out the bubbles since it swells as it cures.

    Now I think you could do the same thing for boat, like covering up wood plywood, wherever you might be glassing. I have an older Egg 1970 and the glass on the hip bump out under the windows is failing. I will take some strips of genuine FG cloth and do the same thing I did to the chair.
    One big advantage of a polyurethane like PL over epoxy to me is ease of use, cheaper, and PL flexes. A lot of the original FG covering on this boat is no longer adhered to the underlaying wood, mostly it is just stuck along the edges.
     
  2. gonzo
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    gonzo Senior Member

    If the fiberglass is delaminated there are major structural problems. A cosmetic repair is not going to do it.
     
  3. sdowney717
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    sdowney717 Senior Member

    yes, I know, any existing covering will be stripped off down to the bare wood.

    On the boat it has simply come loose from the wood, so it is like a tight fitting cap of fiberglass-resin laying on the wood. The cabin roofs are still solid not rotten and dont leak. One of the noticeable failures is where this cap meets the cabin sides. Then you can tell it has come loose and been glued down over the years as a bandaid type repair. the lower edge of the cap was originally held securely by a long piece of teak wood. Years ago I pulled all the teak off as it was letting water into the screws and top edge where teak molding meets cabin sides and causing rot.

    Easy enough to repair on the side under the main salon windows. This is a small area to begin with before doing anything elsewhere.
    It simply flows over the bumpout edge and was originally secured with molding top edge and bottom edge. So the FG there is about 10 feet long and 6 inches in width.

    I am impressed with how easy and strong the chair worked out. PL is 100% waterproof adhesive glue. Mixed with glass cloth makes a good combination. It will flex with the wood so it wont crack.

    Posting a couple pictures of the repaired chair bottom The bolts broke thru the wood at the rear and the top layer of plywood delaminated from stress of being sat in.


    One reason for the failure is a lot of leverage is applied by the chair back where it meets the chair bottom.
     

    Attached Files:

  4. whitepointer23

    whitepointer23 Previous Member

    you are pretty much doing what we do in our water proofing business, we use cloth and polyurethane sealer and wet it out like glass.
     
  5. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    Not really new...I used it about 7 years ago with a quick and dirty canoe I built...taped the chines with it... Never really had a problem with it but it is not the easiest material to fair and leaves a puffed up foamy surface that isn't as waterproof as it is when used as a glue.
     
  6. sdowney717
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    sdowney717 Senior Member

    yes it will do that so take your putty knife and go back over it, drag the knife over the surface back and forth, pressing down hard to squeeze out the bubbles. So it is put it on, then wait a few minutes, repeat to press it down, wait a few minutes press it down, etc... Have to do that 3 or 4 times at most. You will hear little popping noises when doing this using the cloth.
    I found it set quickly when using it with the FG tape.
    On seams, take some cereal bag plastic and press it down onto the glue and squeeze it to the shape you want, it will swell up against the plastic and make a smooth surface. If you want it to cure in THICK layers you must mix a fiber, wood dust, etc, into the glue. The moisture in the fiber creates the cure. Doing that you can cure it inches thick. Super dry fibers might consider moistening with some water first. Mostly I have found wood dust has plenty enough moisture just from the air likely due to its porous nature. The fiberglass tape must also have air moisture wicked into the strands cause it set up fast.

    I have a lot of experience using this also as a wood filler. Mix some with sawdust, preferably the same color wood your working, fill the gouge, take some cereal bag plastic and clamp or press down. Painters Tape also works. You will find that when you stain your wood, the appearance is very similar to the wood surface. Epoxy form a glassy blacker look which this wont have. PL is definitely a softer glue than epoxy.

    I also seal end grain wood and I seal large surface area of wood just with a skim coat of the glue. With that you basically smear it on and use a putty knife to drag the surface. You want it very thin. The putty knife will form the layer into the perfect thickness. It will soak into the wood slightly and give it a glossy rubber like shiny coat which is not UV proof. You have to also go back over it with the knife as it will puff up and you want it thin.

    You can clean up with 90% rubbung alcohol. Alcohol destroys the undried glue's ability to set.
     
  7. alan white
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    alan white Senior Member

    Given the huge superiority of what is probably a cheaper product (epoxy), why use the more expensive stuff and end up with a finish that is less than desirable?
    Actual strength is quite low. Little stiffness and not as waterproof as would be possible using other methods. Good for a spot repair mid-season because it won't be hard to remove later, but I think that's it.
     
  8. sdowney717
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    sdowney717 Senior Member

    epoxy is more expensive, I think.
    Prove me otherwise but then still easier to use the PL.
    I know waterproof for PL, but I have read epoxy does pass water.

    Now the big one for me and wood is flexibility. I have used epoxy and for what I used it for it always eventually cracked, or cracked and flaked off the wood.
    I am talking about waterproofing window channels where the sliding window tracks sit. My epoxied repairs failed. I did not use any cloth though. If I had used a large amount of cloth and epoxy maybe it would have worked.
    For those I ended up using Sanitred Permaflex and it has been easy fix.
    I bet I could have used PL with some of the wallpaper fiberglass tape.

    Mostly on this large old wooden egg harbor I am using these goos for sealing out water, the wood structure itself is strong.

    Also the area under the sliding salon windows the fiberglass coating cracked in a few spots and also on the front vberth windows. I had tried repairing with some new glass and epoxy but after a few years it separated from the wood due to the fiberglass covering has no movement but the underlying wood does move.

    I have not done any heavy large thick epoxy glass cloth layers which might work to entomb the wood but why do that and then price would be very high I think in materials cost of epoxy.

    I just bought several yards of light ounce woven glass cloth and going to do the PL with glass trick under the sliding windows sometime this year. I will rip out the existing fiberglass with resin layed on the wood 43 years ago which is slowly failing due to wood moves, then cracks open up and water gets in causing rot and wood warping and water stains on the interior wood work. The PL with glass cloth will flex, not crack, and be smooth enough to look ok with paint.
     
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Sdowney, epoxy is cheaper then PL and other polyurethane construction adhesives, but a considerable amount.

    If you are applying epoxy as a topical treatment, then you aren't using it properly and it's no wonder it has failed. It's not the epoxy's fault if application is flawed.

    Wood moves unless you encapsulate it. Epoxy is really the only material that can do this successfully. If you follow established procedures, you wouldn't have the failure rate you've experienced.

    I'm not going to get into a physical properties comparison of the two, as it's well covered in many places, but epoxy is superior in every way measured, including price. Good luck with your home brews.
     
  10. alan white
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    alan white Senior Member

    Epoxy doesn't normally crack. Whether it's cheaper depends on how you buy your polyurethane. I will agree that epoxy needs a dry substrate (which epoxy should seal well to begin with... however, wood that is allowed to absorb water migrating from behind the wood somwwhere isn't a good case for epoxy. Everything should be dry in there, period.
    So then I agree, making a case for very flexible but sticky goo. Even that will suffer a hard life compared to a totally sealed epoxy job. But recognize the poly fix is not going to last a long time. If you want to do a long lasting job (and you may not), do like they do when building new. Almost nobody (except some ameteurs) builds new with polyurethane adhesive (I think).
    Epoxy, again, will not crack unless the wood it's applied to is allowed to expand and contract under it. Little can withstand the expansion of hardwood. I believe granite used to be split that way. So that's the issue.
     
  11. alan white
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    alan white Senior Member

    PAR has posted while I was writing, but you see he is saying mostly the same thing.
    The most important thing to do is for you to see that your personal experience with epoxy is biased due to some mixing mistake, or because you epoxied over wood that expanded and physically split the surface. No resin could remain sound under such conditions.
     
  12. sdowney717
    Joined: Nov 2010
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    sdowney717 Senior Member

    yes exactly and it is an old wooden boat with lots of structure internal wood and external exposed to heat humidity rain etc...
    No way on the window channels for total encapsulation except if you removed all the interior trim wood, stripped all the finishes inside and outside and did total encapsulation. But you then loose all your nice wood finish inside the boat. Perhaps new construction the wood 'trim' is purely a cosmetic item. On my boat it is part of the structural wood, stained varnished on the inside and painted on the outside of the boards. So I can realistically only entomb one side of the wood. So only the exterior surface could be encapsulated with epoxy. So far using the PL and the Sanitred Permaflex has been a very positive experience results wise. And still have nice interior finishes. I have in the past used some epoxy to varnish wood, but the sun ate the epoxy truned it hazy yellow and it all cracked and the wood turned various colors underneath.

    Colean is a clear polyurethane lasts decades which I considered as a varnish but very very expensive.

    What is especially bad with the epoxy cracking is water then gets in and the wood rots. I had major rot where I epoxied the front windows exterior wood. Water soaked in and I dug out couple inches of rot.
    The inside of the boards had not yet been affected.
    I repaired that mess by mixing PL with sawdust and slathering it into the cleaned out wooden wound. The PL expands and sealed it all where wood siding meets fiberglass deck. Put a piece of cereal bag plastic and a backer board to keep the PL flat staying in place as it sets.
    Then a thin skim coating of PL and paint on top.
    Been solid perfect for about 5 years now outside in the weather. And no peeling paint.
     
  13. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The definitions of the words encapsulation and entomb should be self apparent. You haven't done either, by your own admission. If you are unwilling or unable to encapsulate, then epoxy is only useful as an adhesive.
     

  14. sdowney717
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    sdowney717 Senior Member

    you get it!
    yes, not willing to entomb the entire boat in epoxy. So I am using sealers which can flex and expand and stay on the wood and keep out water.
    So using a polyurethane is cheaper for me on this.

    I did entomb the lower hull in sanitred permaflex which I used about 25 gallons of the stuff. that was a bear. Totally removed all underwater planks, re-framed many frames coated pieces separately with permaflex then as a whole which glued the whole bottom together. For seaming I used PL. I used new bronze square drive screws number 12 from McFeeleys. For screw plugs I used PL Premium Construction adhesive.

    I gave up trying to reuse some framing where the screw holes had rotted. I had been drilling and putting in face grain plugs. This worked but simply became too much work. So I started replacing suspect frames.
    a few pics showing the progress
    on right side frames with glued in plugs, all the holes were either plugged or new wood used.
    and frames with holes waiting for plugs. I found I could not trust the old holes to hold even new larger screws.
    [​IMG]
    an inside view
    [​IMG]
    shaft tube lined with liquidtight non metallic conduit, great stuff!
    this tube can flex without cracking. Black PL glued it perfectly.
    I dont recommend the white PL poly for anything. I foud it reacted oddly with the permaflex. hardened white PL softened when topcoated with permaflex into a white grease substance. Stange!
    Glued in with Black PL roof and flashing poly
    [​IMG]

    [​IMG]

    shaky pic but you get the idea. A bronze part sits on top here. I cut this tube flush using a dremel and a belt sander for smoothing flat.
    [​IMG]

    final shot showing accumulation of several layers of permaflex. One thing working upside down is it tends to form drips, they drip on you also when painting this on. As it sets thicker you can sort of smooth it out a little
    [​IMG]
     
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