P3D Floating 3-D

[Bill Davis <bd3d@xxxxxxxxxxxxx>]

Hi Sam,

The mylar balloons they sell at DisneyWorld come with plastic "anchors"
attached to the end of the ribbon which just balance the lift of the
balloon so it doesn't fly away when released.  They float along, with the
anchor (shaped like Mickey's head, of course) skimming along the ground.

I had a couple of these around, so I grabbed a balance to see what's what.
The anchor weighs 14.5 grams.  The empty balloon weighs 16.5 grams.  The
balloon has a capacity of roughly four US gallons, or about 0.5 cu. ft.  (I
filled it with water then measured it back out)  Didn't do the math to see
if this agrees with others' posts about helium lift.

I bet you could get some large lawn bags (40-50 gal) and a Happy the Clown
helium kit from WalMart and go for it.  Weight of a Husky 33 gal bag: 35 gm.
The economy bags would offer the lightest weight but may also be the most
permeable.  Helium molecules can sneak through a latex balloon, but not
mylar.  Dunno about polyethylene garbage bags.  

A 40 gallon bag *should* provide enough lift to raise 300 gm (including the
bag itself).  Of course this would *just* lift it, providing little pull
against the tether(s) to compensate for air movement.  I think ideally you
would want some overkill to keep the lines tight and prevent the camaras
bobbing all around.  Don't forget to factor in the weight of the fishing
line.  

Are you committed to building your own camera for this?  The one-use
cameras are pretty light.  I weighed an older Kodak and it tips the scales
at just under 40 grams.

On another topic, I'm still looking for that r.p. screen material.  Lowell
Noble's QD Technology makes a black screen material that reportedly works
very well.  Unfortunately cost is prohibitive. A 4 ft. by 6 ft. screen runs
around $4k. (According to Brad Nelson of QD, plastic is not likely to work
due to internal stress marks and striations from the manufacturing process
that depolarize the light.  He said that one of the commercial screen
manufacturers was showing a non-depolarizing r.p. screen at SIGGRAPH in Las
Vegas.  He couldn't remember the name of the mfr., though.) 

Iwerks' website mentions a 3D Video setup that uses rear projection and
linear polarization.  I'm trying to get some more information on the screen
material.

I'll keep you informed.
Best regards,
Bill Davis
mailto:bd3d@xxxxxxxxxxxxx



------------------------------