Center point is off-center by 5/8 inch ... see next photo.
Note: image names use the words "high point" but this is not really the high point.
The rib curvature center is 18-5/8 inches from spar cap; thus,
double this for skin 4 feet by 37-1/4 inches.
After vacuum forming, 1-1/4 inch will have to be cut off.
Measuring rib with special flat tape ... 36 inches spar cap-to-cap.
Ends tape together with duct tape. 4' 1" pipe in place.
Marks on pipe indicate the center. Tape holds it there.
Pipe taped to sheet, tape on top merely an indicator of the bleed hole location.
Just past the tape is the bleed hole. Shop Vac hose will be inserted in pipe (where else?).
Charles Snyder recommends a 2 inch pipe.
(Yes, I know that seem small!)
My scrap pile had a 1-7/8 inch black plastic pipe. Test proved it would be OK.
Nose Skin is place between a folded 1-mil poly taco style.
All edges are folded and sealed with packing tape.
The edges are taped to the table.
A hole will be cut for insertion of the vacuum.
Nose skin ready to be wrapped around the nose ribs.
Skin wraps nicely. Left skin is flush with spar cap.
Right edge (bottom) extends beyond spar cap as 1-1/4 inch must be cut off.
Note simple system:
- spar caps are supported by wood blocks to provide clearance.
- Straps are placed over the nose skin.
- One end is hooked to the edge of table, the other end is tack down .
- Start cranking ... evenly.
Left 2x4 is clamped tight.
Note Center Point drawn on nose skin.
That point is slightly past the high point.
Right 2x4 has space to allow the strap to slide.
(Ignore the angle iron on the 2x4.)
I had expected to be shimming the table and/or the spar web blocks.
But after clamping down my D-Cell, I found every point on the spar web to be dead-center level ... without shimming the table or spar! I can't believe it ... but I will admit to finding a "sweet spot" on the table and using old door framing for the blocks under spar web.