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Stéphane,
The Vivak showed no tendency at all to stick to the ABS. I did read one guy said he wiped the plug with cooking oil before pulling because he felt the reduced friction made the thickness more consistent. It could be worth trying but was not needed to avoid adhering.
I think a vacuum would be more likely to crush a form than a manual pull depending on how much vacuum you generate. Even at a vacuum equivalent of 10psi this plug would have been exposed to nearly 1000lbs of pressure. I was pushing down with maybe 50 pounds of force.
That being said 2 layers of 6oz, 1 layer of 2.47oz and one of 1.6oz make a very tough shell. I don't think I came anywhere near the point of crushing it. If in doubt add a third layer of 6oz while you are there it would only take a few minutes and weight is not an issue.
I would certainly do the ABS over any plug. It is very easily sanded and has the effect of adding a .060" coat of primer in one go. If you do ever damage it you can pull it off and do another one. Pulling the ABS will also give you a little confidence before you try the Vivak. If I recall correctly ABS was about $40 for a 4' x 8' sheet compared to $60 for the Vivak. If you can find a place that doesn't have a minimum order surcharge it can be had for even less. The sheet would make blanks for 12 canopies of this size.
I found out you can get black for even less money and that might make seeing any remaining defects even easier. White hides imperfection in a surface, black shows everything.
Take care,
Brent
The Vivak showed no tendency at all to stick to the ABS. I did read one guy said he wiped the plug with cooking oil before pulling because he felt the reduced friction made the thickness more consistent. It could be worth trying but was not needed to avoid adhering.
I think a vacuum would be more likely to crush a form than a manual pull depending on how much vacuum you generate. Even at a vacuum equivalent of 10psi this plug would have been exposed to nearly 1000lbs of pressure. I was pushing down with maybe 50 pounds of force.
That being said 2 layers of 6oz, 1 layer of 2.47oz and one of 1.6oz make a very tough shell. I don't think I came anywhere near the point of crushing it. If in doubt add a third layer of 6oz while you are there it would only take a few minutes and weight is not an issue.
I would certainly do the ABS over any plug. It is very easily sanded and has the effect of adding a .060" coat of primer in one go. If you do ever damage it you can pull it off and do another one. Pulling the ABS will also give you a little confidence before you try the Vivak. If I recall correctly ABS was about $40 for a 4' x 8' sheet compared to $60 for the Vivak. If you can find a place that doesn't have a minimum order surcharge it can be had for even less. The sheet would make blanks for 12 canopies of this size.
I found out you can get black for even less money and that might make seeing any remaining defects even easier. White hides imperfection in a surface, black shows everything.
Take care,
Brent
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