Re: Hard coating for foam toroid

[Terry Fritz <twftesla-at-xxxxxxxxxx>]

Hi Gary,

	Be super sure to test any coating on a scrap piece first.  Many materials
will attack styrofoam very agressivily!

Cheers,

	Terry

At 02:17 PM 11/7/2000 -0500, you wrote:
>I recently placed an order for a custom 7" x 30" Styrofoam toroid from a
>place that makes custom plastic shapes, largely for theatrical props.  They
>have a completely computer-controlled milling operation and can make any
>complex shape.  They normally work with 2 lb Styrofoam, similar to what
>coffee cups are made of.  They could also order 3lb and 5lb foam.  The 5lb
>foam is similar to the stuff they make bicycle helmets out of - very tough
>stuff.  But the 3 and 5lb options added roughly $100-$200 to the total cost.
>I was concerned with the possibility of denting and wanted to make the
>toroid as dent-proof as possible, but at a reasonable cost.  
>
>Initially I was told that they would be able to apply a very thick (1/8")
>coating of polyurethane.  I felt that such a coating on top of the 2lb foam
>ought to make it pretty dent resistant, so I choose that option.  After the
>foam was cut I learned that they would not be able to apply it as the cost
>would actually be very high.  So now I'm left with a foam toroid with little
>protection against dents.
>
>What materials are there that I could coat it with to improve upon its
>dent-resistance?  I don't want to mess with fiberglass or anything that I
>would have to sand down.  I'm thinking self-leveling like epoxy.  Is this
>available at reasonable cost in bulk (quart)?  Is it thin enough that it
>could be poured on while the toroid is slowly rotated?  Is the cure time
>long enough that I can get the whole big thing coated before it starts
>curing?  Or are there other things?  Someone suggested the boating repair
>industry may have something I could use?
>
>I will post pictures and details of cost, contacts, etc, to my web site
>after I receive and evaluate the toroid in the next couple of days.
>
>Regards, Gary Lau
>Waltham, MA USA
>