Which glue/adhesive? Bent lamination. yes another glue thread. - Woodworking Talk

Kender · 10-13-2009, 12:02 AM

I am looking for the right glue to use on a new project. I have not started yet and it is still in the planning phase.

The project is a covered bench swing. The bench will be wide enough for 3 adults with a roof/covering for shade. I have not yet decided which style of bench I am going to make. Horizontal slats, vertical slats, thin, wide, flat bottom, curved bottom, sharp angle from backrest to seat, or flowing curve. All these options are playing in my mind but the part that I need help with is on the frame.

Most of the metal frame bench swings I have seen are an 'A' frame construction, some are straight legged and some are curved. Either type is more appealing (to me) than the 'H' frame style. I want to something fancy since this is supposed to me an x-mas gift. So I came up with the idea of making the legs of the 'A' frame as one (I'm looking at the bent laminations as one piece of wood) continuous piece. Basically make the top point of the 'A' more of a rounded curve. I also thought of putting curves at the feet of the 'A'. These feet would be the same piece of wood but curve away from the 'A' and make a horizontal squiggle like this ~ with an extra curve or two.

The cross bar of the 'A' would also be a squiggle of bent lamination and cut to taper into the legs.

I searched the forum for bent laminations and several people recommend the dap adhesive or unibond. I looked at those and the dap is indoor use and the unibond being water resistant. This is going to be an outdoor item in florida so I don't think "resistant" is good enough. I do plan on staining and varnishing this if that makes a difference in the resistance level. My other option which was the plan before looking at the dap or unibond is titebond III. I have heard some people mention some creep with pva glues and with this being a weight bearing structure the creep is a concern. If I use the TBIII I had planned on also using a hardwood dowel through all layers of laminate near the bends to help lock them in place. Part of the plan is to use wood veneer onlays in decorative shapes....like a lizards, leafs, vines, etc. to cover the dowels. This would hide some of the dowels if there are too many and would match the curvy almost vine/root like design of the 'A' frame. Any exposed dowels would be contrasting to accentuate and show off the wood.

I am not sure what type of wood I will use, although I know it will not be an oily wood like teak (eventhough I love the way it looks). I am thinking I will use quartersawn white oak for it's stability and natural resistance to the elements. I know it's not the best wood for outdoors but from what I have researched it is still on the short list of affordable woods recommended for outdoors.

Sorry for the long post but I didn't want to leave out something that might make a difference in which glue to use......plus I tend to get a little chatty when I am on a roll.

Thanks

trident98 · 10-13-2009, 12:07 AM

Tightbond III, Use redwood, cedar or teak. I wouldn't use oak. Tightbond 3 works well outdoors with redwood and cedar. not sure about using it for teak. teak is expensive but it is high end and will last forever.

Kender · 10-13-2009, 01:10 AM

The expense of teak is the main reason I won't be using it for this project. If it was more like red oak then I would consider it even with the extra steps need to glue up oily wood.

cabinetman · 10-13-2009, 09:49 AM

Red Oak doesn't fare as well as other species in the elements. White Oak would be a better choice. For a glue, I would use a phenol-formaldehyde glue, a resorcinol formaldehyde, or a slow set two part epoxy.

Julian the woodnut · 10-13-2009, 09:58 AM

White oak is actually a really good choice for outdoors use as it is quite rot resistant. You can use tb3 for bent laminations

frankp · 10-13-2009, 10:13 AM

for the bending I've had more troubles with oak than other hardwoods, but it should be okay for the radius you're suggesting. I'd probably go with that or possibly maple, but I think the oak will be more rot resistant.

I usually use epoxy, but Titebond III should also be sufficient for your needs, despite the "not for structural use" warning on the label.

cabinetman · 10-13-2009, 10:18 AM

Quote:

Originally Posted by Julian the woodnut

White oak is actually a really good choice for outdoors use as it is quite rot resistant. You can use tb3 for bent laminations

I agree, I should have included TB III on my short list.

Kender · 10-13-2009, 05:27 PM

thanks guys.

rrich · 10-13-2009, 09:02 PM

I was talking to the Franklin (Tite Bond x) guys at AWFS. I asked a similar question.

Their answer was to use any of the "extended" or "extensible" (I'm not really sure of the exact word.) products. These products are good for bent laminations while their normal products are not. The normal products tend to creep after curing or so I've been told.

The label on the products was more of a generic label with plain red and black printing rather than their typical label with graphics.

I asked where to buy the extended products and was told "Austin Hardwoods" in Santa Ana. (My area of Los Angeles) My suggestion would be to ask at your local hardwood lumber yard. If they don't stock, I'm sure that they will point you in the right direction.

Kender · 10-13-2009, 11:52 PM

would the creep issue be solved by using the dowels before and after the bend?

frankp · 10-14-2009, 07:45 AM

Kender, the creep issue is actual creep in the glue, ie it spreads further away from the joint and into the wood, from what I understand. I was just having a discussion about this on mimf in regards to using TBII for guitars and all the purists there say "it doesn't work". I tend to disagree but then I'm not trying to be a professional luthier either. The glue does creep (at least TBII and I think TBIII) but they make products that should be okay as rrich said.

cabinetman · 10-14-2009, 08:29 AM

Quote:

Originally Posted by frankp

Kender, the creep issue is actual creep in the glue, ie it spreads further away from the joint and into the wood, from what I understand. I was just having a discussion about this on mimf in regards to using TBII for guitars and all the purists there say "it doesn't work". I tend to disagree but then I'm not trying to be a professional luthier either. The glue does creep (at least TBII and I think TBIII) but they make products that should be okay as rrich said.

What is this "creep" jazz you guys are talking about?

The Titebond Rich mentioned "Extend" is a formulation of Titebond II, and it offers a longer open time, but does not have the bond strength of TB III.

BHOFM · 10-14-2009, 09:10 AM

What few bent lamentations I done, I bent the pieces
first and used epoxy. Epoxy requires a loose fit and
the pressure points in the curves press out all the
epoxy. Pre-bending the parts relieves this problem.
I think it would help in any situation.

A steam box can be made from a piece of PVC pipe
and an electric tea pot. The pipe needs to be insulated.
Newspapers will do the trick, four or five loose wraps,
a bit of duct-tape.

frankp · 10-14-2009, 11:38 AM

Cabinetman, I had never heard about "creep" before either, but was reading a bit about it after a bunch of people said I shouldn't use Titebond II for my guitars. Mostly I ignored it all as I've used TBII for all of my woodworking (indoor and outdoor) projects that didn't get epoxy. I even use it on kayak paddles that are unfinished and have no protection. The glue gets mildly soft but never anything major, even after 8 hours of paddling.

BHOFM makes some good points about prebending. I've also made steam boxes out of a single sheet of the foam insulation cut into a box shape and duct-taped at the corners, with towels to "seal" the ends. Works great.

Kender · 10-14-2009, 07:58 PM

Quote:

Originally Posted by frankp

Kender, the creep issue is actual creep in the glue, ie it spreads further away from the joint and into the wood, from what I understand. I was just having a discussion about this on mimf in regards to using TBII for guitars and all the purists there say "it doesn't work". I tend to disagree but then I'm not trying to be a professional luthier either. The glue does creep (at least TBII and I think TBIII) but they make products that should be okay as rrich said.

I understood the creep issue to be one where the glue allows the 2 surfaces to slip, gradually, and thus allowing the bend to straighten out. If it really is about the glue soaking into the wood then I won't worry since I have seen what plain elmers wood glue can do. I took apart a table saw cabinet that my grandfather made back in the mid 80's and all he used was elmers wood glue. It was end grain to face grain on 3/4 ply. It took me several good whacks with a dead blow mallet to get the joint to seperate and it ends up that the plywood layer tore out before the joint gave out. If plain old elmers can survive 20+ years in Florida heat and humidity without failing then I am not going to worry about TBIII having issues.

rrich · 10-14-2009, 08:17 PM

Quote:

Originally Posted by Kender

t
If plain old elmers can survive 20+ years in Florida heat and humidity without failing then I am not going to worry about TBIII having issues.

What you're saying is absolutely correct, however the issue with bent laminations is different. With a bent lamination, the glue is under constant pressue. The bent wood wants ot straighten out and is constantly applying pressure to the glue. Over a period of time the glue tends to allow the wood to move and start to straighten out. I'm sure that there is a numeric factor to describe this creep effect, I just don't know what it is.

Kender · 10-14-2009, 08:29 PM

Quote:

Originally Posted by rrich

What you're saying is absolutely correct, however the issue with bent laminations is different. With a bent lamination, the glue is under constant pressue. The bent wood wants ot straighten out and is constantly applying pressure to the glue. Over a period of time the glue tends to allow the wood to move and start to straighten out. I'm sure that there is a numeric factor to describe this creep effect, I just don't know what it is.

This makes sense, and is why I was wondering if dowels set through all layers of the laminate would lock the layers in place. My main concern would be having to order the special epoxy and if I don't order enough then the project is on hold until I get more in. I preferred to be able to just run down the road to a hardware store to get another bottle of TBIII. Dap weldwood is available locally but it states it is for indoor use and I don't know if an outdoor varnish will seal out the weather enough to use the indoor dap on an outdoor project.

cabinetman · 10-14-2009, 08:44 PM

Quote:

Originally Posted by rrich

What you're saying is absolutely correct, however the issue with bent laminations is different. With a bent lamination, the glue is under constant pressue. The bent wood wants ot straighten out and is constantly applying pressure to the glue. Over a period of time the glue tends to allow the wood to move and start to straighten out. I'm sure that there is a numeric factor to describe this creep effect, I just don't know what it is.

I've never heard of "creeping". Maybe it's a word that's been propagated on the internet. I've done a lot of bent laminations and some were massive. I've never encountered any movement. IMO, if there is bond failure it's likely due to improper procedures.

rrich · 10-14-2009, 09:49 PM

Quote:

Originally Posted by cabinetman

I've never heard of "creeping". Maybe it's a word that's been propagated on the internet. I've done a lot of bent laminations and some were massive. I've never encountered any movement. IMO, if there is bond failure it's likely due to improper procedures.

That's very interesting Mike. I've never tried it myself but instructors at school and a cabinet maker have told me about the creep. The guys at Franklin say "Use this and not that." but they are selling...

When TB-III first came out, the web site said that TB-III was not intended for "Structural Purposes". I asked the basic question saying that ALL glue uses was structural except, perhaps wall paper. As I understand more about glues, I believe that TB-III should not be used in, say, an engineered beam application. Thinking about the structural limitation, the don't use for bent lamination restriction makes sense.

Maybe what is needed is a numeric quantification of the amount of creep. If we're worrying about 1/32" over 10 feet, it's non issue. So the numbers are all important to keep this discussion relevant to the real world.

Kender · 10-20-2009, 09:34 PM

sketch added