Buyers Guide Forums Information Buy/Sell Communities Build/Tech Racing Site
MARS projects - VFS - Mold measurements
What's New

About

Rides

Mailing List

Members

Photos

Projects

Library/Misc.

MARS Gear

Links

Click HERE to go back to the top Vacuum Foamshell page
Click HERE to go back to the main Projects page
Click HERE to go back to John Tetz's Projects
Click HERE to go back to the Foamshell Links Page


Mold Measurements and Preparation

This shows the inside of the Momentum mold. The first step was to make internal measurements to see if my LFWD could possibly fit inside. The nose of the OFS is in the foreground.

The mold was marked off in 6” vertical lines starting from the nose to the tail, then 3 horizontal lines. The first, at 11” from the bottom, extends from the tip of the nose to the tail, and represents the widest foil section. The second, at 6.5”, passes through the widest part of the seat/hips and close to the heels. The third, at 20”, represents the toes, handlebar, and shoulder line.

Many measurements were taken along these three lines from the flange surface of the mold into the shell surface, and then plotted on a 1/4 scale drawing. These show the foil shapes at the three horizontal lines. A side view drawing was made from the 6” vertical lines, and the LFWD was superimposed on top. Although it will be tight, it does look as though the LFWD will fit inside, so the project is a go.

This shows the plywood flanges added to the mold. The Zote foam will be attached to this surface. The wooden flanges at the mold surfaces are sealed against vacuum leaks with silicon caulking, as are the Zote-to-flange surfaces. As a funny side story, the first time I applied vacuum all I got was zero vacuum. I had to remove the sealed Zote and search for the mysterious leak. The key is plywood. Plywood has cover sheets with internal layers. Those internal layers are not continuous, but full of internal passages. Those passages (there were four of them about 0.125” square) went from the vacuum side of the Zote to the outside world. Needless to say, this was an embarrassing discovery.

This shows the breather blanket. I used eight 0.1” diameter vacuum holes scattered across the mold in an attempt to provide uniform vacuum on all surfaces. The Zote would seal off those holes without the breather. I first tried Spandex, but didn’t like the way it pushed the foam off the surface of mold after the vacuum process was finished.

This shows the Zote lying across the mold flanges. A system of short blocks were screwed through the foam into the wooden flange. Silicon caulk was used between the Zote, flanges, and blocks, as leaks can occur through the screw holes. Note: these blocks have to be clamped down quite hard to hold the Zote in place. Use the larger diameter sheetrock screws so they don't strip out in the flange wood. Pull the blocks down in stages as the foam slowly compresses. The cans of paint press the foam down into a concave shape to reduce the amount of final stretch, reducing the thickness loss. I found that the process of vacuum forming such a large sheet of Zote is pushing the limits of what the Zote people have experienced. Zote sheets are not long enough to cover the entire mold, so an additional piece had to be welded (not glued) to the main piece. As described in the Tail section, this weld line is a convenient place to separate the tail from the main shell. See Appendix on Welding Zote Foam.

This shows the mold face down, sitting on top of the oven with an array of vacuum lines. I guess the easiest method is to make a male mold and hand-wrap the Zote on it, heating it in sections like I did to form the present OFS. That does work, but it is almost impossible not to have a little waviness. I need to come up with a broader heat source for that technique.

To me, vacuum forming (or pressure forming) is the next natural stage to investigate. If it does work, then copies can be made. Speaking of copies, making the Varna clones is also a lot of work, much more than what I am going through. I feel very lucky to have these female molds. Even though they are not quite the right shape or size, I seriously doubt that I would have gone through all the work and expense of making female molds. I hope the LFWD will fit inside.

Next section: Vacuum process results