Thread: Blackbutt structural glue, advice please?

As I understand it, a double helix twists as well as turns, so I guess you mean a helix. Selleys 308 would have been good, but they dont make it anymore. Looks like an epoxy job. Never had a problem glueing blackbutt. This is quite an undertaking. Have you ever done something like this before? You will need at least another set of hands. Are you planning on assembling on site or a lift-in? Its going to be heavy.

I have used Blackbutt quite a bit and have never had any trouble. I have used all the titebonds, a few others although at the moment I just use Selleys Exterior PVA on everything.

purbond polyurthane, but other polyurthanes will work,

you can buy 20lt drums of polyurthane for couple hundread bucks better than paying 25 for 500ml of sellys.

Thanks for responses all.

Rustynail, no I haven't, but am willing to give it a go. I've built house frames and a guitar, this is somewhere in between. If it doesn't work out, plan B is a kit. Wife is happy to help. We'll be building it in place, the workshop is in the basement.

Plan is: buy seasoned blackbutt, re-saw (bandsaw or table saw) and thickness to about 6mm laminations.
Vacuum clamp to helix form on a drum (see pic attached).
Do this for outer and inner stringers and handrails. Laminations for inner stringer will need to be finer (3 or 4mm?). Tighter curve.
Clamp completed stringers in stairwell, mark tread slots, pull stringers down and cut out with plunge router (see pic for jig).
Dowel the treads into the stringers (see jig)
Wife wants aluminium balisters, so drill holes in stringers and handrails for them (same jig)
House construction doesn't start until March, so I'm trying to get all the details sorted now, hence research re glue.
Re Selleys 308, they still talk about it on their site. Powder and hardener, sounds like an epoxy?
http://www.selleys.com.au/adhesives/household-adhesive/wood-adhesive/high-stress-wood-glue but I haven't looked in the shops.
Thanks Claw, I plan to do some testing on samples, I'll try them all. Big requirement is no creep.
And thanks Gaza, I'll need bulk whatever I use. I've heard polurethane is not too pretty at visible joints, is that true?

Originally Posted by crankshim

Thanks for responses all.

Rustynail, no I haven't, but am willing to give it a go. I've built house frames and a guitar, this is somewhere in between. If it doesn't work out, plan B is a kit. Wife is happy to help. We'll be building it in place, the workshop is in the basement.

Plan is: buy seasoned blackbutt, re-saw (bandsaw or table saw) and thickness to about 6mm laminations.
Vacuum clamp to helix form on a drum (see pic attached).
Do this for outer and inner stringers and handrails. Laminations for inner stringer will need to be finer (3 or 4mm?). Tighter curve.
Clamp completed stringers in stairwell, mark tread slots, pull stringers down and cut out with plunge router (see pic for jig).
Dowel the treads into the stringers (see jig)
Wife wants aluminium balisters, so drill holes in stringers and handrails for them (same jig)
House construction doesn't start until March, so I'm trying to get all the details sorted now, hence research re glue.
Re Selleys 308, they still talk about it on their site. Powder and hardener, sounds like an epoxy?
http://www.selleys.com.au/adhesives/household-adhesive/wood-adhesive/high-stress-wood-glue but I haven't looked in the shops.
Thanks Claw, I plan to do some testing on samples, I'll try them all. Big requirement is no creep.
And thanks Gaza, I'll need bulk whatever I use. I've heard polurethane is not too pretty at visible joints, is that true?

Well the theory looks OK but better you than me. If you are able to source 308 it would be ideal for your project as colour would suit blackbutt also it is water clean up, which is a great advantage on these sort of projects. It is heartening to know that your dear wife is prepared to assist. After all the contract did say for better or worse. May I suggest you make a scale model from matchsticks prior to the BIG event.

Epoxy is frequently used in laminations, because it exhibits no creep and because you can use slow hardeners to give you more time to get things into position.

You can also tint it to match the wood colour.

It's available in bulk from most marine supply places (about $100 for three litres) and it'll also bond well to aluminium. I suggest studying the guides at the West Epoxy site.

Selleys 308 is a urea-formaldehyde adhesive, so it's not an epoxy.

the issue you will have with this stair is the head height, and gettibg it right.

you will need to rebate the strigners to take treads and wedge them no need to dowel,

ill look up the details of our glue suppiler on monday we fax them over what we are doing and they spec up the glue for the project.

we have used polyurthane for curved handrails last year with no spring back or visable glue lines it also provides for longer working times,

for the strips you will need to use a wide belt sander to run them through as a thicknesser maybe not as acuate.

for the timber i would use structal F27 blackbutt for the inner core them use select grade blackbutt for exterior skins to save on material cost, you could also use structual for whole job but keep the best lengths for the visable areas.

there is a guy on another forum that builds these stairs everyday he provides classes and can even do detail drawings / instructions

Thanks Rustynail, I’ll look around for 308 to test, yes she is a dear wife, believes in me even if a rational person wouldn’t (Claire that is supposed to be a compliment)
Yes it will be a big event, I plan to run a dress rehearsal with no glue and leave it clamped up for a few days, hopefully the laminations will remember their shape a bit. I’ve made a model in sketchup and played around with the dimensions.
Thanks Master Splinter, the West Epoxy site is very useful. Roller application looks good, and extra slow hardener. They suggest acetone prep for oily wood, perhaps worth remembering if I have trouble……. Vacuum clamping video is good.
And thanks Gaza, head height from stairwell fascia to step below is 2007 on my model, and I can take up to 100 off the fascia if I need to (see pic). Yes I plan to rebate the stringers, thanks for the tip about wedges, I’ll investigate. Would much appreciate details of your glue supplier. And thanks for suggestion about using a sander instead of a thicknesser, I’ll run some tests. Yes, F27 for interior and select on exterior sound good.

If you can find a link to the guy who builds these and does classes / drawings I’d much appreciate it.

I’m looking for a supplier of seasoned blackbutt around northern NSW / Brisbane / Sunshine Coast if anyone knows one?