Sounds like you have a very nice dish mold.
One word of caution about thin cloth lay-ups. If too thin a layer is laid up,
additional layers and reinforcements can distort the original or first layer.
I never worked with Kevlar or Carbon Fiber, but these are very strong, rigid
materials that would be very strong at 0.030 inches thick, especially if a
lip is around the outer edge. I would add small reinforcements after a
finshed 0.030 inch lay-up is cured. Vacuum bagging is a lay-up technique used
to evacuate out excess resin that would otherwise add weight and reduce
strength.
Bruce
In a message dated 2/11/2002 12:10:45 AM Eastern Standard Time,
writes:
> Brian Boldt wrote:
> >
> > I've got a mold for a 34 inch dish I cut on a CNC router last summer on
> > which I'd like to do a layup. In looking at kevlar and carbon fiber, it
> > seems as though they are often intended as reinforcing rather than
> > structural elements. Does anyone have experience with glass/kevlar/carbon
> > layups, and if so, what is the necessary cloth thickness or number of
> layers
> > to make for a robust dish? Also, anyone with experience with
> kevlar/carbon
> > hybrid cloths? They look to have a promising combination of stiffness,
> > resiliency, and light weight.
>
> Keeping the weight down is primarily a function of minimizing the amount
> of resin binding it all together. You can increase the thickness a
> little without adding a lot of weight by the use of microballs in the
> resin.
>
> There are varying weights of cloth. I, for instance, have some in glass
> and in kevlar that's designed for model making and is very thin.
>
> To some extent how thin you can make it depends on the load points. It
> will help to have a reinforcing bead around the outer edge. Then it
> comes down to how the mic will mount, and how you will be supporting the
> dish. Under no load conditions it would not take much material to
> maintain shape. However, both wind load and the stresses involved in
> supporting it and it supporting the mic will shift that.
>
> I've actually thought that the lightest dish that would be stiff would
> be made by using something like airex foam molded to shape and skinned
> with a thin layer of cloth on both sides. Kevlar is the common one used
> in kayaks. My only experience with airex was building a 50' sailing
> vessel where the hull was built out of that kind of construction. The
> other advantage of airex would be it should be fairly sound deadening.
> And a dish built that way would be really strong for it's weight.
>
> The foam is available down to 3mm in thickness. The hard part would be
> where to get it in small amounts. A 50' boat took a good sized stack
> more than 25 years ago when we built it.
>
> Here's a link to the company:
> http://www.alusuisse-airex.com/products/e/100/110f10_e.htm
>
> Walt
>
>
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