A New Boneheaded Stunt, Literally

Marathon, FL
N 24 42.391 W 081 05.683, (See the map)

This must be the season to entertain my blog readers with dumb stunts. Yesterday, I strung out my hammock between the mast and the fore stay (as I've done many times before). This time, as I climbed in to the hammock it immediately let loose and dropped me. My head cracked on the hatch, and my back on the cabin bulkhead. To be honest, it didn't hurt very much.

In the pictures, you can see the broken fan housing, and the three cracks propagating outward. The cracks go all the way through, the structural integrity is destroyed.



When I turned around, I was shocked to see that my head had broken both the Nicro solar powered fan and the underlying transparent hatch cover. That hatch cover was made of 25x25x0.5 inch Plexiglas (arylic) or Lexan (polycarbonate). That stuff is super strong, probably even bullet proof at that thickness. How did my poor old bony head crack it? Two things: First, it must have been fatigued by UV exposure. Second, the cracks emanate from three small plastic feet on the bottom of the fan. Those feet concentrated all the force to point loads.

Now I need to replace the fan and the cover. It is a matter of safety. If that cracked cover were to fall apart when a big wave breaks over the bow at sea, it could fill the cabin with water and sink us. The Nicro fan also has a feature that allows us to close the opening to keep sea water out.

The first thing I found is that Nicro is out of business and that replacement fans in stock are rare and getting rarer. I found that defender.com claims to have 2 left in stock, but I had to pay $200 for the stainless steel model. (Ouch)

The hatch needs to be strong enough to support me, plus Libby both standing on it at the same time. Apparently, it also needs to be strong enough to withstand 200 pound men falling from the sky head first.

I did a little research on the Web. I can buy a Lexan replacement 25x25x0.5 inches for $188, or 25x25x0.25 for $120. Lexan is strongest. I can buy a Plexiglas replacement 25x25x0.5 for $80. I think 0.25 Lexan is about the same strength as 0.5 Plexiglas, but I'm not sure. Both claim UV stabilization, but I'm not sure which is better.

When I look at the engineering properties of polycarbonate versus acrylic I see a lot of numbers quotes for moduli and parameters, that I find hard to translate into useful information. I have lots of readers with engineering knowhow. Which material, which thickness should I order?