Eoast me Father,foe I have sinned.

[johnny means]

In my hubris, I thought I had thought of everything and was really feeling myself. So I left this project in the vacuum bag over night for the last pressing in a multistep veneering process. My last thought out the door was, maybe I should hang out and keep an eye on this thing. It was the final step in a month long project, after all. Nah, it'll be alright. Well, something malfunctioned and the vacuum climbed a bit too high.

[Patrick McCarthy]

Oh Johnny, i'm feeling your pain. Sorry

[Jim Becker]

Ouch...and it looks like you already had a ton of work and time into that, too. Can you put another new layer of veneer over to fix or is it toast?

[John TenEyck]

I had seams look like that when I lost vacuum, and there was no way to rescue it. But mine was a straight forward end table; nothing like your project. That stinks.

John

[johnny means]

Ouch...and it looks like you already had a ton of work and time into that, too. Can you put another new layer of veneer over to fix or is it toast?
That's the plan. But it was all ⅛" veneer, so now I have to go with paper backed to minimize the edge grain showing. Luckily, the bottoms not super visible, so no one will probably ever notice the plywood like veneer.

[Brian Runau]

Lack of experience with veneer, can you explain to us uneducated what you mean by vacuum climbed comment? thanks brian

[johnny means]

Lack of experience with veneer, can you explain to us uneducated what you mean by vacuum climbed comment? thanks brian

At sea level a perfect vacuum applies 14.7 pounds per square inch. That's over 2000 pounds on every square foot. Obviously, this much weight will crush a hollow form. You avoid crushing your peice with the vacuum press by regulating the vacuum with a small leak. Kind of like the overflow hole on a vanity sink. Anyway, something went wrong while I was gone and the vacuum went to high.

[Kevin Jenness]

Johnny ,

Bummer, I hope you can salvage the piece. I had a disaster early on with an imploded bending form due to lack of interior support and the memory has stuck with me.

Can you give some more construction details? It appears that the veneer and substrate buckled inward between the form ribs. How thick is the substrate, what is the material, and what is the rib spacing at the rim?

My rule of thumb with curved torsion boxes or bending forms is ribs 3" on center for one layer of nominal 3/8" bending ply and 6" o.c. for two layers, with full vacuum (>22 mm hg). If I need to reduce the pressure (rare) I have an adjustable switch controlling the rotary pump and valve.