Titebond III testing

[PAR]

I'm not sure of your bending jig, but generally with all the aliphatic resin adhesives, you want lots of clamping pressure, not just "remove all dead space" within the contact areas.

Generally you'll get about 10% to 12% "spring back" while steam bending green stock. You'll get more spring back if bending kiln dried material and also if "dry bending" as much as 20% spring back.

Compensating for this takes a little experience, as each species will react differently, but generally you over bend the predicted amount of spring back, so it will "relax" into the radius desired.

If you have a 10' radius you want your stock to conform to, make your jig to a radius of 9' (10%), 8' 6" (15%), 8' (20%) as needed. The same applies to ellipses, "S" or other curves, which also can be "resized" to suit spring back.

On the "free form" curves, that seem to be the case in the above image, you have no idea what you'll get. Internal stresses and density differences will cause each to be quite different if stacked on top of each other with moderate pressure and permitting the wood to "find it's own way" in the curve.

[Boston]

hi Par

ya its been a long time since I bothered bending anything so if my terminology is a tad rusty oh well. I need to gain some experience in this area so I have started incorporating more curved forms into some of the finish work Ive been designing

Titebond recommends that clamping pressure not be excessive
basically dont squeeze all the glue out of the joint
I use a lot of this type of glue and I notice that even if the clamps seem tight when first applied 24 hours later they have gotten lighter as the glue sets up

not sure if this is a good or bad sign but it seems to be nearly always the case whether clamping bent or straight

the curve didnt have to be anything to specific so I used a batten
a true ogivoil section would not looked very good in this application
I considered the envelope method of drawing a parabola but it wasnt that critical and I needed to leave a short straight section at each end for joinery
these things get incorporated into a raised panel skirt
stock was kiln dried and bent cold ( dry ) so I used fairly thin pieces
1/4 thick and 2" wide
so far they are holding fairly steady after having sprung back 1/8 in the last 24 hours for a total of 3/4 in 48 hours from there original arch height of 17 3/8

the majority of the clamping pressure was applied via the four lower clamps with the upper three clamps assisting in keeping the steel perpendicular, although Im sure they did contribute in some significant way to overall clamp pressure. I tend to have a pretty firm grip and actually break clamps from time to time so although I should probably just use more clamps with less pressure each, I often forget and just use what I need
those little pins that hold the handle to the screw tend to sheer off when I get after em
I have a box of replacements handy

I new the pieces would spring somewhat but given all the variables and the non critical nature of the curve I did not make any effort to calculate it before hand

Im going to guess that leaf thickness and consistency is key in getting a consistent result from a similar material

will be interesting to see if my results correspond to your estimates
how much time are you considering when you calculate spring back

I just thought since I was making em anyway Ild measure out what they did and post it

[ancient kayaker]

Boston: Titebond III is reported to prefer about 5 psi (although the manufacturers specify ludicrously high pressures) which is doable for a flat joint, but difficult to achieve uniformly across an arch. However, I think your test is very representative of what one might do in practice for an arch, which is more to the point than establishing a theoretically attainable performance.

I calculated a springback of 0.41 in an arch of this width and height made from 6 identical lams, using a spreadsheet that (I think) applies to this case. If the calc is right, the extra 0.215 springback may be due to creep in the glue: I am not sure how long Titebond III needs to get to ful strength. The manufacturer says

"Our solvent free products may reach full strength in twenty four hours under warm and dry conditions, but will require several days longer in damp or cool conditions"

[Boston]

you have a spread sheet for this ?

heavy pressure eh
news to me
hmmmmmmm
Ild like to read that
on the bottle it say's moderate pressure
or at least I thought it did

I had 86x2x10 sqaure inches of surface area being glued or
1720 square inches actually only 860 square inches of glue
at 5 lbs each that should have been 4,300 lbs
hmmm
600 lbs on arverage each clamp
its looking like Par was right
I wonder how much each clamp is capable of applying
I sure cranked those things to get everything into contact
I had four cranked tight and three on pretty tight

each arch was given a full 24 hours in the jig
temp was an average of say 70 degrees
Im an outdoor sports kinda guy so night time was likely 55~60 deg day 75~80

ok so I just had to go look up clamps and there various abilities to apply pressure
http://www.google.com/url?sa=t&sourc...eOQvK0ur7FPoXA

just under the picture of all the pipe clamps there is a paragraph that estimated pipe clamp pressure max at 1403 lbs
its just to the right of the smaller heading "how much clamping pressure do you need"
personally
Im not buying it
its probably half that
good call
I should have used a few more clamps

[PAR]

TiteBond III is 80% full strength in 24 hours, but can take a week of more to reach full, thin film cure. The thicker the glue line the longer this takes. I've had pooled TiteBond III that was wet a few weeks later under the crusted exterior "skin". Unless you live in Arizona's desert, expect these types of glues to take a good week to completely cure in tight, well fitting joints.

[Boston]

dam
your good
ok
I did not surface the joints
I got a thing for sharp blades and high blade speeds
so when I resaw'd these "lams"? I didnt shine em up any before I glued em
there were no blade ridges and Ive always thought that titebond kinda likes a rough sanded surface anyway
which is pretty much what I had

a week eh
interesting

Ill be messuring these things over the next four or five days or so anyway
so Ill watch for any continued movement

[hoytedow]

You can never own too many clamps.

[Boston]

oh I have a stack of em
I just didnt have a problem getting all the lams/ leaves ? to compress with what I used
I think par was just suggesting I use more pressure in the future
the steel keeps things nice and straight and combined with the drywall distributes the pressure evenly over the work
as long as the drywall holds up and doesnt try to lift away
thing seems to work fine

[ancient kayaker]

Originally Posted by hoytedow

You can never own too many clamps.

-I know, I know!
http://www.boatdesign.net/forums/att...-7outwales.jpg

Originally Posted by Boston

you have a spread sheet for this ?

-It’s a bit too scrappy to make public, but it predicts the curve adopted by a piece of uniform wood bent around either one or two points. I use it for computing optimum mold location(s) for canoe design, to get the plan shape I want. To adapt it to predict spring-back one needs to know how it works.

Originally Posted by Boston

heavy pressure eh
news to me
hmmmmmmm
Ild like to read that
on the bottle it say's moderate pressure
or at least I thought it did

This is the Titebond III information page, see Application Guidelines under Clamping Pressure
http://www.titebond.com/ProductLineT...e=94&prodcat=1

-I quote “Enough to bring joints tightly together (generally, 100-150 psi for softwoods, 125-175 psi for medium woods and 175-250 psi for hardwoods)”

Heavy enough for you? I find these figures a bit over the top! I suspect at those pressures there would be very litle glue left inside the joint. According to this, for my wee sailboat with it’s 12' x 1" outwales I needed 6.5 tonnes per ‘wale. My patent plastic pipe clamps (see first link) deliver about 5 psi when spaced at 4" and that works fine for me. But as noted before, I rarely use hardwoods: it’s mostly used at wear points and decoration, for woods like cedar, pine and okoume the full strength of virtually any glue is largely wasted.

[PAR]

I don't think you'd starve joints with these pressures. These adhesives don't really soak in or have the capillary action of epoxy. When hand clamping I crank the crap out of clamps until I threaten the wood I'm clamping. I don't know how close I am to TiteBond's recommendations, but I'll bet it's darn heavy pressure. I'll also go back and check clamp tightness after an hour or two to insure it's still tight.

Urea formaldehyde and plastic resin adhesives are the same way and want lots of pressure or they will fail.

[wardd]

you'd be surprised at the amount of pressure that is exerted by a thread at even moderate torque

[Boston]

well just for fun I bent those two Ive got done a little
didnt budge
and they have a great thunk to em when I sound em
I think they are pretty dam solid
I might start working em tomorrow
Ill slice a rabbit in em for the raised panels and hold off on cutting em for length till the last minute
I also need to trace em for the curved sections of the panels
will post a few picts when Im done
B

So when can we comment on the REAL building??

From Sailors to steamers, (I held back for more than one reason), from steamers to motoryachts.........
now? any boat in sight?

[ancient kayaker]

Boston: is the springback in the arches the same for all 3 samples? If it's creep that would be likely to vary.

there are several things that could result in inadequate glue setting, such as lack of clamping pressure, insufficient clamping time before application of stress, excess moisture due to exterior location at night and temperature variation.

On the other hand if they are all exactly the same it's pure springback and my calculations are off.

[Boston]

they all sprung the exact same amount
but Ill measure again tomorrow the last one that came off the molds today

its been dry here for the last three days since I started the glue ups
and the drips of glue off the pieces are mostly dry
although exactly as par suggested the puddles are not dry yet
some of those were pretty deep as I just slathered on the glue

Apex
I should have some picts by say Wednesday for you if your interested
Ive got to unwrap the raised panel columns I already have installed in order to join the skirts
its the hand rail bends that you will probably want to see though
I make my own hand rails and these are of an unusual section
sorta squarish with some beveling and some fluting
I had to buy a special sander to keep the edges square and still sand down the band saw work
one of those funny looking ones you see every once in a while and wonder what it could possibly be good for

customer wanted me to throw in a kinda Salvador Dali melting clock look to the end caps
but Im not so sure about that
oh I can do it but I dont think it goes with what the rest of the piece looks like
I might mutiny on that plan
depends on what it pays
am doing a custom front door as well
then I suppose its on to the front hall
and then they have an addition in the back as well
oh
they want furniture for there cabin out of all tree slabs
which will be a fun task ( check this out, $6000 for ten pieces of wood )

Im kinda bouncing off the walls to finally have some work to do so as far as Im concerned they can paint it all checkers and polka-dots for all I care
Im just glad to be working