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Uncle Grumpy
Joined: 15 Jan 2007 Posts: Location: San Clemente
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Posted: Mon Mar 08, 2010 11:14 am Post subject: All you need to know about glues for wood in a marine enviro |
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This is from well respected woodworker and boatbuilder Bob Smalser, a frequent poster on the Wooden Boat forum.
Resorcinol: The marine standard. If you can get 70° F or higher for an overnight cure and consistent and high clamping pressure with no gaps, you won't go wrong using it. Likes wood at 10-15% EMC, according to Navy tests. Long open time. Repairable with epoxy. Ugly red glue line.
Marine Epoxy: The repair and restoration standard. Bonds well to a wide variety of materials, and usable in almost all flexibility and temperature conditions. Needs no clamping pressure, only contact—fills gaps well. Likes wood below 12% EMC. Repairable with itself, joints can often be broken apart for repair using heat. Clear glue line and can be dyed to match the wood. Controllable open time with different hardeners. Slightly permeable to water vapor and there are reports of failures in fully saturated wood and with White Oak. Very sensitive to UV, requiring protection.
3M 5200: A rubbery, polyurethane sealant in various colors with adhesive properties sometimes used as a glue. Fails as a glue under water saturation without high clamping pressure, and without the proper strength testing I couldn't do here, it's not recommended as a stand-alone marine glue. Repairable with epoxy.
Liquid Polyurethane: Gorilla Glue, Elmer's Probond, Elmer's Ultimate, and others. Versatile in temperature and bonding wet wood with moderate open time, these glues aren't rated for below waterline use but initial use shows potential as a marine glue. Likes high clamping pressure and tight fits similar to resorcinol—it won't fill gaps. Will successfully glue green wood at 30% EMC. Repairable with epoxy. Noticeable, yellow-brown glue lines.
PL Premium Construction Adhesive: This polyurethane goo shows promise as a marine glue with further testing and use. Works like 3M 5200 but cures and behaves like liquid poly. Appears to bond well to everything epoxy does, and more where epoxy and liquid poly won't, perhaps because of a higher isocyanate content—it bonds to difficult surfaces only cyanoacrylate super glues will bond to. The only general-use glue I've found that will bond difficult aliphatic-contaminated surfaces. Appears flexible to temperature and moisture content with gap-filling ability, but as a construction adhesive, its open time is shorter than liquid poly. Appeared to like high clamping pressure, and unlike other glues, wouldn't bond at all without at least some. Repairable with itself and epoxy. Glue line as in liquid poly.
Urea Formaldehyde Plastic Resin Glue: Weldwood, DAP and others. The old interior furniture standard, and in older marine applications that required well-blended glue lines. Still preferred by many, as it is a no-creep glue easily repaired using epoxy. Long open time, it needs tight fits and 65° F or higher for an overnight cure—it doesn't fill gaps. Best glue line among them all and moderate water resistance still make it useful for interior marine brightwork applications. A relatively brittle glue and UV sensitive, it requires protection—but its brittleness is an aid to repairability, as joints can be broken apart for repair. An inexpensive powder with a short, one-year shelf life.
The Titebond Family of Aliphatics: Convenient. No mixing, just squeeze. Short open times, fast tack, and short clamping times. Fast, and an acceptable long-grain layup glue—in heated, commercial shops, I've had rough-cut Titebond panel layups in and out of the clamps and through the planer inside of an hour. Flexible in temperature and to a lesser extent in moisture content, but the bottled glue can freeze in unheated shops. A flexible glue, it has been reported to creep under load, sometimes several years after the joint was made. The latest Titebond III appears to be a stronger glue than its two predecessors. Difficult glues to repair, as they won't stick to themselves and no other glues will except cyanoacrylates, which are too brittle for general use. Epoxy and fabric aren't bonding to aliphatic glue lines in marine strip construction, compounding repair difficulties. While not definitive, the new PL Premium appears to bond well to Titebond III residue and is worth pursuing by those repairing old white and yellow aliphatic joints.
More info here:
http://www.woodcentral.com/cgi-bin/readarticle.pl?dir=smalser&file=articles_605.shtml
And here:
http://www.woodcentral.com/cgi-bin/readarticle.pl?dir=smalser&file=articles_737.shtml |
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puurri
Joined: 26 Oct 2009 Posts: Location: sydney, OZ
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Posted: Tue Mar 09, 2010 5:04 am Post subject: |
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At last, some real tech info! Look at the WBF forums for fact not opinion! |
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Poobah Dolphin Glider
Joined: 09 Jan 2004 Posts: 696 Location: California, San Diego
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Posted: Tue Mar 09, 2010 1:25 pm Post subject: |
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That's interesting about the epoxy and fabric not sticking to the Titebond glue lines. I'd never considered that. How about varnish sticking to Titebond glue lines? Mr. Mike, have you had any problems there?
Possibly some important variables in the equation....how long you cure your glue joints before you finish your paipo, and the quality of the epoxy or varnish. |
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Uncle Grumpy
Joined: 15 Jan 2007 Posts: Location: San Clemente
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Posted: Tue Mar 09, 2010 2:16 pm Post subject: |
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FWIW
A while back I did a little experiment with PL's PU Window, Door & Siding Sealant as an adhesive.
I'd read about people using it instead of epoxy for building lapstrake plywood boats. It comes in a couple colors and is paintable.
First, I glued two small pieces of ˝" marine ply about 2" x 5" together (cross grain at right angles) with enough of the PL to get a good squeeze out.
Then I let it set up over night.
Then I stuck it in the freezer over night.
Then I boiled it for 1 hour.
Then I stuck it in a bucket of water for a month.
Then I tossed it on the roof and left it there for 6 months.
Guess what?
After all that, it was still stuck tight and the squeeze out was still flexible.
Destructive testing eventually resulted in the wood fibres giving way before the goo.
Have not used it for this purposee yet but thought I'd relay the info.... |
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mrmike
Joined: 06 Sep 2007 Posts: Location: coronado, ca
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Posted: Tue Mar 09, 2010 6:27 pm Post subject: |
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I have no problem with varnish sticking to titebond never had a board brake on a glue line ( and I have broken lots of boards ) they always brake along the the week grain and sometimes I make them on the thin side _________________ PAIPO ON
blog http://mrmikespaipos.blogspot.com |
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OG-AZN
Joined: 27 Jul 2009 Posts: Location: Norcal
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Posted: Tue Mar 09, 2010 9:18 pm Post subject: |
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Thanks for all that info - good stuff. |
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