Microballoons

[Subscuba <Subscuba@aol.com>]

Speaking about microballoons,

The buoyancy required by my wet sub is met by using "Techspheres" from
Floatation Technologies (1250 minimum buy for 156 pounds of buoyancy at about
$380). They have a website at http://www.flotech.com. These are essentially 2
inch plastic balls rated for 250 meters. I also use West Marine Epoxy filled
with West 410 microlight microballoons. This gives me a homemade syntactic
foam which is a pain to make but gives me what I need. I also looked at using
foam, such as polyurathane. This is a special foam made for this use, not the
stuff you buy at Ace Hardware. This foam comes in different densities and
cost. I talked to the vendor and he gave me some interesting information about
foam. It turns out that foam has two strengths. The first is a bubble which
intersects other bubbles. The intersections have  high strength to withstand
deformation. But where just the bubble wall exists, such as at the surface of
the form, the strength is much less. This means that the foam would have great
strength but would start breaking down the exposed bubble walls and taking on
water. The foam can be sealed to stop this, if you can really seal it.

I opted for the microballoon filled epoxy and Techspheres. They are very
durable, at least at this stage in construction, just messy and tedious to
install.

You can buy custom syntactic foam but it was much too expensive for my
application. The vendors were talking in terms of $10K and higher.

Simple buoyancy or ballast tanks are very appealing.

Ken Martindale