Wiseacre Dave
Well-Known Member
Greetings,
I'll be building MiniMax wood wings and fuselage on a 15 foot wood build table. I don't believe there is a particular flatness specification in the plans, but I'd like to get the table as flat a reasonably possible.
I've constructed three 3' x 5' plywood torsion box table tops. Each is flat to about 1/16" or better over the 5 feet. The table tops are ganged together on top of saw horses that have adjustable feet levelers.
When attempting to level the entire 15 foot table top surface and simultaneously get it flat across the 15 feet, I can accomplish both of the following, but not at the same time:
1) Using a self-leveling laser, I can get the entire 15 foot table flat to the accuracy of the laser, which is +/- 1/16" over 15 feet. Because the laser is self leveling, the entire surface should now be flat and level.
But when I check flatness across the transitions between the table tops, I see a 1/8" deviation from flatness (a straight edge rocks on the transition). That was unexpected because each table top is flat and I don't detect significant non-straightness across the width of the table at the tabletop ends.
2) If I instead concentrate on leveling across transition areas between adjacent table tops, I can get flat transitions, but the entire 15 foot table is now out of flatness by about 1 inch over the 15 feet.
I'm not sure which, if either, situation is more acceptable. On the one hand, in case 1), a wing spar won't sit flat across the 15 foot length. On the other hand, in case 2), I'll be building a 1" flatness deviation into the wing and fuselage.
I don't think it's practical to do case 1) and sand the transition level, because I suspect I'd remove too much of the 1/2" ply table surface in those areas.
The photos show the setup.
Which situation is better than the other, or is neither acceptable? Can you think of a solution that would optimize flatness and level over the 15 foot span of three connected table tops? Perhaps I'm overthinking it, and the judicious use of shims where and when necessary would be a good solution.
Thanks for any help and advice!
I'll be building MiniMax wood wings and fuselage on a 15 foot wood build table. I don't believe there is a particular flatness specification in the plans, but I'd like to get the table as flat a reasonably possible.
I've constructed three 3' x 5' plywood torsion box table tops. Each is flat to about 1/16" or better over the 5 feet. The table tops are ganged together on top of saw horses that have adjustable feet levelers.
When attempting to level the entire 15 foot table top surface and simultaneously get it flat across the 15 feet, I can accomplish both of the following, but not at the same time:
1) Using a self-leveling laser, I can get the entire 15 foot table flat to the accuracy of the laser, which is +/- 1/16" over 15 feet. Because the laser is self leveling, the entire surface should now be flat and level.
But when I check flatness across the transitions between the table tops, I see a 1/8" deviation from flatness (a straight edge rocks on the transition). That was unexpected because each table top is flat and I don't detect significant non-straightness across the width of the table at the tabletop ends.
2) If I instead concentrate on leveling across transition areas between adjacent table tops, I can get flat transitions, but the entire 15 foot table is now out of flatness by about 1 inch over the 15 feet.
I'm not sure which, if either, situation is more acceptable. On the one hand, in case 1), a wing spar won't sit flat across the 15 foot length. On the other hand, in case 2), I'll be building a 1" flatness deviation into the wing and fuselage.
I don't think it's practical to do case 1) and sand the transition level, because I suspect I'd remove too much of the 1/2" ply table surface in those areas.
The photos show the setup.
Which situation is better than the other, or is neither acceptable? Can you think of a solution that would optimize flatness and level over the 15 foot span of three connected table tops? Perhaps I'm overthinking it, and the judicious use of shims where and when necessary would be a good solution.
Thanks for any help and advice!
