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White oak for frames?

Posted: Sun Nov 16, 2003 7:05 pm
by RCS&M
We are getting ready to buy the wood for our Cracker box. I thought I read somewhere that someone had trouble with the epoxy on the oak frames. Is that true? Mahogany is about 3X the price in my area.

Posted: Mon Nov 17, 2003 1:47 am
by Graham Knight
Can you get Douglas-fir? It's much cheaper and easier to work with than Oak, lighter too, and it has better rot resistance and bending characteristics than Mahogany.
I'm surprised that Glen-L don't recommend it over anything else.

Posted: Wed Nov 19, 2003 11:03 pm
by ken
I did post a lengthly reponse in the old webletter. It is surely in the archives. I would not choose Oak as top-of-the-list materiel for epoxy construction. Oak is so dense that epoxy will not penetrate very deep. I have tested my parts and the glue holds up as well as the plywood gussets, however the oak does swell a lots if wet. the oak swells while the glueline is stable to moisture, thus having the liability of stress at the glueline if the joint gets wet.
Oak is superb when construction uses mechanical fasteners like bolts, screws, or nails.
Other woods are superb for epoxy fastening methods. Since you are near the South, you could look into yellow pine. The West System does recognise yellow pine as a good structural wood for their epoxy. In my opinion the woods for a epoxy project are in order
1. Mahogany
2. Doug Fir
3. Ash
4. Yellow pine
5. White Oak

Posted: Thu Nov 20, 2003 6:28 am
by JimM
Wouldn't oak be ok if you used penetrating epoxy first?

Posted: Sat Nov 22, 2003 4:43 am
by fred
I'm still puzzled at the "new" concerns over glueing OAK?

Back in 70's & 80's Weldwood's RESORCINAL 100%
waterproof glue was in fashion. It set VERY VERY HARD,
was liquid, even thinner than epoxy - and it glued oak
quite well! Whatever happened for white oak to suddenly
be called poor? I build a ROUSABOUT with 100%
resourcinal, and white oak (air dried) longitudinals.
23 years later - not 1 failed joint?

And way back then they said "mahoganey" was best
primarily for cigar boxes - not structural members?

Fred

Posted: Sat Nov 22, 2003 5:01 am
by Graham Knight
I think you hit the nail on the head when you said it was "thinner than epoxy", this would enable it to penetrate the wood better than epoxy does. Epoxy being quite thick and fast curing works better on softer more absorbent timbers, it tends to just form a skin on hard woods like Oak.
I've done a few tests over the years that I've used epoxy, and found that the strongest glue joints are usually achieved with the softer timbers where the glue penetrates better. Note that I'm only referring to the glue joint not the wood, the harder woods will always be stronger but the joints may not, the trick is to strike a good balance between the two. FWIW this is true of all wood glues, not just epoxy.

Posted: Sat Nov 22, 2003 4:49 pm
by Guest
Graham -

I seem to remember some reference to "experimental
aircraft building", where they still use RESOURCINAL
glue. When I was building that Glen L ROUSTABOUT
17' I/O speedboat - "epoxy" 2-part structural
adhesive (which they called it then) was just coming
on the scene (1977).

It was funny, the stuff dried so HARD and STIFF,
its a wonder those joints didn't fracture with
no give.

At that time, I used a 2-part epoxy enamel, for
painting the glassed exterior. For the next 23 years,
that light blue paint - chalked and turned milky white
when wet in the sun? Eventually - it started to
vanish off some parts of the hull's glassed exterior?

Fred
(.....grandparents from UK)

Posted: Sun Nov 23, 2003 1:28 am
by Graham Knight
Luckily for us epoxy has come a long way since those early days and is a much better product now. I remember using it in the mid-70s and it being very hard and quite brittle as you say, but now I often use it at work to make resin castings which have to be really tough, and it's virtually indestructible.
I've been assured by my paint suppliers that the epoxy paint I'm using now will not degrade in sunlight, I hope they are right!

Posted: Fri Dec 05, 2003 8:34 pm
by Guest
Graham -

On the "epoxy paint problems from the 70's" - it was strange -
I painted the Glen L ROUSTABOUT a light-blue epoxy-based
paint. After about a year, the paint did several things: it gave
off a chaulky powder, frequently and actually for 20 years!
It also would darken and "spot" in the bright sunlight -
but then return to normal later? The paint always puzzled me.
After like 23 years - the light blue paint, started to wear
out and show thru to base fiberglass covered plywood
underlayment. Never could find out why?

The paint was sold by Defender Industries Inc., in the
later 70's. Almost like their own special brew I guess.

The "chaulky" white stuff - could be waxed off, and for a while (!)
it would be back to normal shiny looking.

Fred
eastern NC

Posted: Wed Dec 24, 2003 5:35 am
by Dave Grason
I'm from Tennessee. In our area, we have a virtually unlimited supply of white oak and it's very reasonably priced. Also, I've been involved in the installation and refinishing of hardwood floors for many, many years and I have to say that white oak is my absolute favorite wood. I was planning on using quarter sawn white oak for the motor stringers in my new Mist Miss. From there I was going to use a frame kit from Glen-L.

So my question for this thread is - can a rough sanding of the white oak, say with a 60 or 80 grit paper improve the white oak's compatibility with the epoxy?

Posted: Wed Dec 24, 2003 8:46 am
by kens
Your answer is yes. West System recommends that oak be coarse sanded at the joint to increase the ability of epoxy to bond.
Also, you can mildly heat the wood at the joint, the heat serves to thin out the wet epoxy and helpd it to absorb into the wood. Do not heat the epoxy itself though, this would only serve to cure the epoxy too fast.

Posted: Thu Dec 25, 2003 4:19 am
by Guest
Thanx Kens, for that reply. And this was a good question that the thread started with. Not having ANY boat building experience, I would have never given any thought to compatibility issues. I'm glad ya'll are here to think tank this stuff.

Yes, I think I'm really going to like this forum a lot!

Posted: Thu Dec 25, 2003 4:22 am
by Dave Grason
Ooops, I forgot to log in. That post directly above mine is also mine. I see that if you're a guest on this board, you can't go back and edit your posts. I'll need to be more mindful of that when I come back. :oops: :)