Titebond III testing

[PAR]

Tar and roofing cements can only be considered bedding compounds, not adhesives. Buehler designs use very littl glue, bolts, screws and nails are he's fastening systems of choice. He does recommend sheathing his plywood planked designs, but other wise he's a PVA, plastic resin or resorcinol man.

Do your research carefully and select the glues you'll need for the specific application. Epoxy can cover a much wider range of tasks and doesn't require ti fits or clamping pressure to work well. This coupled with it's strength makes it hard to look somewhere else. No one glue gets it all done, but epoxy does darn near all of it, while the others can be left wanting in some situations.

[Boston]

glue lams are cheap and easy and come in any size you want
as eliptical arch beams they are kinda pricey as Res mentioned
but they may have some old molds that they made for someone elses project that approximate the arch you are after
you might get lucky you never know
the price goes from 6~12 bucks a foot to about 15 a foot for arched sections
oh and the arches will not be radii of more less than about 20 ft either as those guys have no idea of how to steam bend

the finger joints in those things are unbelievable strong and the glue is all you need specify to feel confident that thing would do the trick
they will make whatever you want if you just make it clear what you want
they probably already use an interior exterior glue but label them for indoor use only for liability purposes

best
B

oh I dont think we ever used pine tar as a glue but often as bedding just as Par said

[rasorinc]

I should add that if you want curves or angles in a beam for frames it is quite easy to build your own Lams using 3/4" thick by 3,4,5,6,7,8,9,wide. You can bend 3/4" stock and using epoxy and 1 piece length boards you will have a solid beam. I made 20
foot lams for beams in a Quansut HUT build I used 2x4s in a full 90* arch, bent one at a time untill shape was held. I was able to leave them 1.5" thick and bent them around pegs.

[Boston]

Bueler is a lumber yard builder if I remember
he probably has a hole section in his book on glue lams
back yard boat builder is the book I think

oh
my test pieces of pl glued are ready for boiling
might do a few tomorrow and see what shakes loose

I have
red ceder to red ceder
white oak to white oak
and
red ceder to white oak
glued up and cured for seven days

[rasorinc]

Bos, I'll bet the weakest bond will be the oak to oak. What adhesive did you use? A guy told me awhile back that when gluing W. oak with epoxy he rough sanded the area then took a truss plate and hammered in into both sides of the joint to make a series of penetrating holes before clamping it under soft pressure. Never had a failure he said.

[PAR]

All three should fail in the wood fibers, if the clamping pressure and environmentals were sufficient.

[Boston]

ah
no hints
I need to find what I find without any preconceptions of what the results should be
ok
this thread is now off limits till I finnish boiling things

[Boston]

ok so the girl is off to work and I got a few hours to use all her nicest pots and pans to start boiling stuff

unfortunately even if I use everything I made these test pieces a tad large and cant fit to many at a time on the stove

that means my results are going to be scewed as the soak time ( 24 hours ) before boiling will vary between test subject invalidating the results to some degree

oh well
I just hope all the lovely tanins coming out of this white oak doesn't stain the girls pots and pans or the next thing boiling will be my nuts

love
B

[rasorinc]

Go rent a large soup pot, and a single electris burner and do it outside. It's better than losing important body parts.

[Boston]

2 hour boil
LNP-901

first group of pieces out of the pot
2 of red ceder to red ceder
2 of red ceder to white oak
2 of white oak to white oak

each piece was glued and clamped with 5.5 lbs per sq in for 7 days and then placed under fresh water for 48 hrs then boiled for 2 hours

none survived
in all cases the glue turned back to its original consistency and any pretense of adhesion was lost

all 6 pieces failed the boil test

6 pieces were not boiled
they were tested soaking wet for strength of bond under direct load only

each piece failed with the application of 70 lbs per sq in or less
none survived more than 70 lbs per sq in
the average being ~50 lbs per sq in

manufacturers specs claim
Shear Strength: ( dry )
24 hours – 225 psi
48 hours – 300 psi
7 days – >425 psi

with the red ceder to red ceder bond being weakest and the white oak to white oak bond being the strongest
this may have been something to do with the permiability of the wood to H2O not of relevance to the performance of the glue

my conclusion would be that this glue is completely unsuitable for structural marine use

B

ps
the pots turned out ok
the girl need never know

[Jimbo1490]

Looks like back to epoxy. Choose an adhesive with a simple formula; BPA resin, cabo-o-sil and a polyamide curing agent. Polyamides give you 'rubbery' cured-state properties, with very high fracture toughness and elongation. Their high mix ratio (typically between 1:1 and 2:1) and high viscosity is ideal for a hand mix adhesive. They are also extremely forgiving of mixing errors, giving close to the same properties with errors of 25% on either side of a 'perfect' (stoichiometric) mix. They are considered low toxicity and low sensitizing. You won't need to add any reactive modifiers (these are all 'highly sensitizing') as you do not need either lower viscosity or more fracture toughness/elongation; you've got plenty of both.

The 1:1 Glue from Fasco is just such a product. Both components about like vaseline in consistency. Long work life, overnight cure. Very low odor.

Jimbo

[MichaelC]

Okay, so in the absence of any glues that will work for sure underwater except epoxy, which I can no longer use, I guess it is wholebunchabolts time. So I will use pine tar as a sealer, not a glue, and bolt the bejeezis out'n it. We all sure appreciate your testing system, Boston. Nice work. Glad to hear her pots and your nuts survived intact.

[ancient kayaker]

Just varnish the sucker until it glows, and dry it after use. The boat that is.

[rasorinc]

Bos, go with the best, proven, epoxy adhesive mix. Save on the cost of aplying the 3 protective coats if you are going to go that route. Don't save on the adhesive. Glen-L offers Poxy Grip at a fair price and have decades of experience with it and 1,000s of boats built using and it is middle priced. I'm using it but will go with RAKA for the coatings. It is a 1 to 1 mix with either fast or slow hardiners or a combination of both. Lots of info on it on their site. Used to build 8' to 60' boats and proven. That's all. Best, Stan P.S. It has been boiled to death and does not fail. click on epoxy. http://www.glen-l.com
click on boat building supplies for price. Just info for you. The only other adhesive (epoxy) I would consider is West. but $$$$

[ancient kayaker]

System Three have the Silvertip range of adhesives that also come in a self-mixing dispenser that fits a caulking gun. Use with a disposable mixing tip. Rather expensive, but no mixing, extremely convenient and quick, and much easier to prevent skin contact. The Gelmagic one is nice, non-sagging, stays where you put it. You should still use protective gloves of course.