Curved Handrail Glue-Up Tips

A discussion of glue selection for a bent railing lamination glue-up, and other advice on the work. December 14, 2009

I've got a spiral handrail to do. I've done curved okay, but I don't think I'd have enough time to do the glue-up and clamp in enough time with ole yellow. Is there a slower setting (open time) glue that is as good as yellow glue? It's only me and my partner and time would be an issue. Thanks in advance - your knowledge is always helpful.

Forum Responses
(Architectural Woodworking Forum)
From contributor C:
This is where you show your stuff. A good dry fit, and marking all the pieces so they can be picked up and put into the glueup fast is helpful. Extend Titebond glue is also helpful, and running back and re-hitting anything that's drying too fast. Both guys should have glue rollers and plenty of tape and rags. It's a good time to hustle, and it takes a lot of clamps - the more, the better. Clamp it into place as fast as possible and then use damp rags and wipe off the excess as much as possible - it's very helpful for the sanding. Finely scrape to clean up excess dried glue, etc.

From contributor J:
Weldwood plastic resin glue is great for this, as is Unibond 800. Both have very rigid glue lines - very minimal spring back, and all the time you could possibly need.

From contributor H:
I have been using Titebond 2 for years now and Titebond 1 before that. It does not dry that fast if you prepare well beforehand and have your clamps ready and your form marked. I do it regularly and only with one helper. I have done it alone also, but you don't want to be in my way when I do.

TB Extend is good if you don't waste your time and get to it. Takes about 10 minutes to get it on the rack to the point where you can start clamping in between the first and last clamp. It also helps if you dry bend the entire thing a day or two before. The wood will take a partial set, making it easier to rebend.

I glue both sides of all laminations and when stacked hold them together with nylon zip ties. Just one at each end and one in the middle. Not too tight. The wood needs to slide as it is being bent. The hardest thing about bending spiral/helical/curved rail is the twist that needs to be applied to keep the bottom of the rail flat.

From contributor L:
I have to respectfully disagree with contributor H about the glue choice. I learned the hard way that yellow glue isn't suitable for bending handrail. I switched to plastic resin 25 years ago and haven't looked back. Just my opinion, mind you, but there's absolutely no way I would bend a handrail with Titebond.

From contributor A:
What are you referring to as your paradigm shifting experience with yellow glue? In my experience glue is glue. The differences are dry times and water resistance.

From contributor L:
Glues run the gamut on what I call the "hardness scale" with, let's say, adhesive caulk like 3M5200 on one end of the scale and something like plastic resin, resorcinol and some epoxies (not all) on the other. They're soft and hard respectively. PVA glues land somewhere in the middle.

There's a good reason why they don't use yellow glue for glue lam beams holding up a roof.

The following is a quote from the website:
"Polyvinyl Acetate (PVA) Glue: Any glue consisting primarily of polyvinyl acetate polymer. This category includes most traditional white glues and more advanced yellow aliphatic resin glues. Although PVA glues can vary in strength, flexibility, water-resistance and sandability, they offer good performance, cleanup with water and are non-toxic. Because PVA glues tend to “creep”, or slowly stretch under long-term loads, they are not recommended for structural applications."

Glue creep is not a myth. In the context of this discussion, I'll define it as the tendency for a tightly bent handrail to try to straighten out by stretching the fully cured glue. The operative word from the above quote is "slowly."

PVA glues, even when fully cured, remain relatively soft and flexible compared with plastic resin. That's what makes them tough. That's what makes them creep. Glues like plastic resin, when cured, are hard as glass.

From contributor B:
Plastic resin is the way to go, if not just for the sandability. Just did a mahogany rail and compared it to same rail glued up with Titebond II. After staining, the difference really showed. PR sands without clogging paper, longer working time, better color match on most species, harder when cured.

Zip strips! Should have thought of that.

From contributor J:
Have you ever cut a bent laminated rail in two that's been yellow glued and then let it lay around for a day or so? The next day you can run your fingers across the cut ends and actually feel the "creep".

Have you ever tried four inch shrink wrap, wrapped tightly around the whole bundle before bending? Someone once told me that that was a sweet secret.

Have you ever tried to bend a rail up the stair and around 180 degrees and made it work? Have you ever discovered finger joints in your bending-rail while trying to bend it? Is there such a thing as too many clamps?

From contributor L:
I use stranded packing tape to hold the oozing bundle together, but I'm going to try the wire ties next. Great idea, contributor H.

Yes, I've done at least a couple of 180 degree bends. They work fine.

Yes, about 20 years ago when some genius decided to finger joint bending rail, I ordered a bunch of 6010 16 footers without finger joints. Still have some of it if anyone's interested.

I bought enough clamps to bend two long rails at the same time. Now I have enough of them to actually bend one at a time.

From contributor A:
I am quite aware of glue creep. That makes sense for a handrail. In my shop we use Titebond 1 for all painted casework, because of the creep issue. The other Titebonds all have major creep issues.

We always use epoxy for projects like handrails, mostly because of extended dry times. Never used the plastic resin (Weldwood?) for anything. I don't consider a handrail in the same category as a structural beam, so I wouldn't hesitate to use regular wood glues if the dry time permits.

I'm thinking that you used white glue way back when you had your paradigm shift. That stuff creeps big time. The absolute hardness of the resin glues can give you a telegraph, as well, when painting.

From contributor D:
Speaking of glue creep, I would not have ever believed it if I had not seen it myself, but a 2 3/4" X 13/16" oak colonial half-round curved casing that I had a supplier make showed evidence of this creep you speak of. I personally cut the curve to fit into place (it was a display curve in our showroom). It was cut flat and it rested on 3" X 3" rosettes. The curved piece (done by bent lamination) was screwed from behind onto a 1/2" think MDF panel. It crept quite a bit. Amazing!

So, maybe the plastic resin would be a better adhesive to use.

From contributor P:
Contributor L, how do you have enough open time to glue up a set of stair stringers with plastic resin glue?

From contributor L:
Open time is moot if you quickly stack the layers on top of one another as you glue them. Nothing saves time like a dry clamp. I'm working on a second book on bending which will also have a DVD showing how to do all of this with time to spare.