Gluing White Oak

I want to make a Helm seat out of White Oak, 3 1-1/2"x24"x1/8" strips per laminate 9 laminates across to make the seat and back. I have not had much luck with epoxy and White Oak. Does anyone have any real world experience with Resorcinal Glue. Please help...

Joe D

 

White oak glues fine with epoxy, assuming proper prep. You have to remove the tannins and clean the surface first. Mix 50/50 acetone and toluene and brush this onto the surface. Use a scrub brush and a fairly light touch, as to not remove material, just a light scrub. Wash off the slurry and clean with a straight acetone or isopropyl alcohol rinse and wipe down. Immediately apply unthickened epoxy to the surface, once the solvents flash off. From this point you can proceed, as with any other epoxy bond.

Resorcinol will work, but requires perfect joint faying surfaces and high clamping pressure to make it work. It can also be sensitive to environmental conditions during the cure. I still use resorcinol occasionally, but not nearly as much as a few decades ago.

 

Oak is a difficult timber to bond because of two factors.
1. It has a very large range of movement with changes in humidity and this coupled with its high density means that movement is powerful. Adjacent pieces bonded together will move differently placing large strains on the joint. Exposed oak rapidly develops checks and splits as the movement overcomes the woods own strength.
2. Oak is highly acidic which can disrupt the chemical cure of adhesives or slowly break down the adhesive over time.
I once phoned the WestSystem tech line to ask why Oak wasn't mentioned in their book and ask how I should use epoxy with oak. Their answer was one word. Don't! According to them the acid would intefere with the cure. I was interested to read Par's method and have not heard of this before.

I have made many windows, doors and stairs in oak and have experimented with different adhesives. My two favorite are PVA (!!) (Windows I made more than twenty years ago which are untreated outside are still showing no breakdown of the PVA joints. If correctly clamped and tight, PVA bonds will always break in the timber). My other favorite is polyurethane. Both PVA and polyurethane remain flexible after cure and I think this helps to maintain the bond.
I suggest that for a laminated seat, the waterproofing of the seat may be as important as the adhesive. Prevent the changes in humidity and you sidestep many of the issues.
Nick.

 

I'm not sure when you contacted West System, but they now understand the realities of epoxy bonds with oak and it's success rate. West will now tell you to use a similar tannin removal technique as I have.

Some oaks aren't as bad as others in regard to checking. As with all hardwoods, the laminate thickness should be decreased, because of the internal stresses Nick has mentioned. I recommend no more the 1/2" thick laminations with the white oak family, while West says 3/4" can work. I've never seen a failure in 3/4" laminations, but have in 1". It's better to error on the too small side the the too thick.

The basic problem with PVA's is creep under load. PVA's also don't like epoxy much, so encapsulation is out. I'm not a fan of polyurethanes, though many swear by them. PVA's do well in static load situations, but not so much in the dynamic loads seen on boats. Even though this is just a seat, it's your butt it's holding up.

Again, remove the tannins as described above and the oak will bond fine.

 

Yes it was quite a few years ago when I spoke to West, things have obviously moved on a bit since.
I don't think either PVA or Polyurethane have a place for important structural bonds on a boat, both require prety much perfectly faying surfaces and careful clamping or the joint will be weak, and yes PVA can creep under load, but for non structural stuff they are fine.
Nick.

 

Thanks for the replies, I did a google search for Resorinol glue, the best price I found was $43.00 for a pint. When I worked in the Cabinet shops back in the 70's we used urea resin formaldahyde in the powered form. I found a 1 lb tub for $7.00. A little closer to the mark as far as price. Thats what I'm going with...

Joe D

 

Good luck Joe.
Let us know how it turns out.
Nick.

 

Use G-flex from West System, it has a great track record with bonding White Oak.

 

G-Flex is just as dependent on surface prep as their 105 resin system.

 

It is important to emphasise the importance of researching the health implications of adhesives and the like, in making product choice, and provide plenty of ventilation. Obviously repeated exposure is more dangerous. Going the cheap way if it the more toxic is a dumb move.

 

Epoxy isn't especially toxic, assuming you don't eat it, bath with it, rub it into soft tissue, ingest abated particulates (particularly if freshly sanded after application), drive it into the blood stream with solvents, etc. Fumes are very slight and dissipate quickly with reasonable ventilation. You also have to assume folks will take reasonable protective precautions, with this and other chemicals as well as read the hazardous materials label.

 

I know 2 non-smokers who got emphysema from working around glues, one for a fairly limited period of time. Even in this age of greater awareness some people are still a little cavalier, and we all know reading labels is something many people neglect.

 

Was that nessacary? I mean jeez haha everyone is such a one up'er on these forums.

 

Article from the Fall 2010 issue of EPOXYWORKS (West Systems periodical) on using various West System epoxies to glue white oak. Includes strength test results. Surface prep was hand sanding with 80 grit and thoroughly wiping with an alchohol pads. http://www.epoxyworks.com/31/pdf/So Stands the Mighty Oak.pdf

Page on G/flex from 2007 which includes strength bonding white oak with several different surface preps: http://www.westsystem.com/ss/west-system-launches-g-flex-epoxy/

 

Was there any dust from the materials being glued in the air? If so the dust may have been responsible for the emphysema, not the glue.