Michael,

We have done tons of similar work. Never in any quanity of that sort. Maybe 10-20 ft jobs a mix of regular chair types as drawn. As well as a couple of jobs like your tapered/scribed chairs that go in a curve.

Those parts are time consuming, with test pieces. Typically the first mold needs a fair amount of work and rework to get the exact finished product. Its more like building fiberglass boat molds than traditional woodworking.

Personally, I would have spent a day making one myself using the vac bag technique, just to see if its an acceptable product. If its good then figure out a mass production model using a press or a big vac bag form 20 at a time ( 25 layups). You would need a skilled crew dedicated to this process.

The metaphor would be somebody walking in asking me to build (500) basic curved door jambs which is the simplest version of your design. I have built probably built that many jambs in my entire 30 year career.

Quoting a project like that without doing some extensive testing and maybe not enough experience especially with the qty is not wise.

The financial risk vs reward of that project is scary simple because of the quantity. You guess 4hrs per part except it takes 5hrs. 1hr x 500 units = 500 hrs x $100 shop rate = $50000

That's if it goes reasonable with a big buffer. The whole project could go sideways and then the math is scary.

Thanks Adam
Because of the scale of the job both the corten steel and stainless framing will be manufactured simultaneously in separate shops and come together at the end. We will both use prepared .dxf files so as on previous jobs the fit will be perfect. The cnc time to produce forms wouldn't be a problem.
I think ill stay away from Compwood for now as I'm certain we can get over the line with more traditional ways. Thx BH Davis.
As for the financial side of things the story is we priced this a year ago at the start of Covid. Then things went quiet in Ireland but is now full steam ahead playing catch up. It was all or nothing at the time. The full contract also includes 350 meters of our usual straight work in a mixture of Oak and Cumaru so rather than let the handy one go I took the lot. No matter what I'm covered.
Thx
Mick

Ideally you can flatten out the parts or Slice it in 3-5 axis software so you can CNC the shape of the "pie" slices that are bigger on one side than the other rather than all the hand fitting, you still may need to trim them in but if spring back and elongation are consistent you might be able to create the shape, we have done that with veneer, never with solid, then forms.

A-

michael,

Please post how this job turns out for you. I'll be interested in your fabrication methods. Good luck and I hope it goes well. Cheers

Good call Alan F on flattening the parts leaving minimal shaping afterwards. Any help on reducing distortion greatly appreciated.
Thx Adam I'll update this thread with progress pics

I agree with the posts. If it were me I would make up a hot press form and use plastic resin adhesive. I had at one time done 2 km of bent handrail and that's what we did. A bit of setup but a guy could weld up a frame for a press pretty quick and use a firehose for the pressing pressure. You would have to keep the metal plates hot perhaps even manually when the press is open but that would work. The problem with vac bag is the cycle time though that would be ideal way to go. Perhaps a big enough setup to do 10 at a time. Heat is critical to speed up cycle time. What a fantastic project!

You can use IR heaters and fants to cool and get a 40 minute cycle time in a Vacc press.

Bill
IR heaters sound good too. Can you expand more on your idea? Any links to specific heaters?
Thx
Mick

Heated platens and IR heaters are okay for veneering onto a core but here you will need to heat through 15mm so the cycle times will be long with only the surfaces being heated. This is where RF gluing shines. Ex Factory sold the perfect daylight RF press recently for $26k. A bit bitch to ship to Ireland though.

If I were doing this, I would be using veneers wide enough to get multiples cut after the cure. The veneer stack after the thickened epoxy was applied would go into the bag which is laid over the form, (not in the bag). A stiff platen clamped down on the top before the front and back is eased on down and clamped under platens, then ready to pull the vacuum.
When the form is not inside the bag, the form can be cheap and easily banged together. It only has to be strong enough to not collapse under the force to bend the slippery stack of veneers.
A tarp with a few insulation sheets can quickly turn any available space into a hot room to speed the epoxy cure with a space heater blowing into it.

Finally a jig to cut the front to back taper is merely a box with a door opening the same size as the diagonal front to back dimension. Then using a circular jamb saw like the flooring guys use, can then saw up one side, around the curve, across the top, then on around and down, indexing off the flat side of the jig/ fixture.
After the first cut on the end, the second cut becomes the first cut of the next piece just by pivoting the jig back and forth.
If your shop already has a CNC that uses a big vacuum pump, all you need to do is tap into the plumbing with a manifold for however many hoses and fixtures you want to gear up for.

We use IR to laminate through 9mm pretty easily. It might add some time to go deeper but it will still shorten the cure time.

Industrial Heaters