[C320-list] Polycarbonate Companion Way Hatch Material Cost

[Troy Dunn]

Jeffrey et. al.

The reason we use Polycarbonate in aerospace applications is because the
added safety outweighs both the initial upfront cost as well as the need to
replace the canopies at very short intervals due to the UV as well as other
material degradation issues.    Polycarbonate is chosen in aircraft and
high speed trains for its impact resistance…usually birds, yup. For
hatches…its more about flexure modulus and acceptable deflection under span
load (typically you want less than 3% for cast acrylic)    You can’t use
lexan in these applications without significantly more load support than
acrylic would require because it starts to bend quickly and then cracks and
crazes.   Pompanette (aka Bomar) still sells lexan hatches.   Note their
design however will have at least two cross bar supports on a typically
sized hatch.

https://pompanette.com/?s=Lexan&post_type=product&dgwt_wcas=1


There's plenty of info out there on the interwebs you can google related to
why cast acrylic is the preferred option for production sailboats.   It’s
always a trade off on the cost side.   I wonder too if the production boat
folks recognize that cruisers aren’t likely to buy a boat that has hatches
that should be replaced during the typical 5-7 years most new owners seem
to keep a sailboat.  Or if they just think the larger unsupported surface
area looks prettier.

The F-35 uses an acrylic canopy design.   The original companionway hatch
cover is also cast acrylic.

T

On Tue, Oct 29, 2024 at 5:18 PM Jack Brennan via C320-list <
c320-list at lists.catalina320.com> wrote:

> Hi Jeffrey:
>
> The only problem with that quote is you need at least 27.5 inches on
> depth. Less than that allows rain into the cabin.
>
> So now the next step up appears to be 48 x 96, unless you can find someone
> to cut you a partial sheet. That's times four plus bulk shipping.
>
> I still think acrylic was a design mistake because it let's in too much
> light and heat in warm weather.
>
> Probably, it was an overreaction to the older, cave-like sailboats.
>
> Jack Brennan
> Sonas 1998 Catalina 320
> Tierra Verde, Fl.
>
> Sent via the Samsung Galaxy A32 5G, an AT&T 5G smartphone
>
>
> -------- Original message --------
> From: Jeffrey Kapec via C320-list <c320-list at lists.catalina320.com>
> Date: 10/29/24 5:08 PM (GMT-05:00)
> To: c320-list at lists.catalina320.com
> Cc: Jeffrey Kapec <jkapec at tkdg.com>
> Subject: [C320-list] Polycarbonate Companion Way Hatch Material Cost
>
> There is a sound engineering reason why Catalina Marine engineers choose
> the materials they specify for their finely produced yachts.  That is the
> reason Catalina vessels last so long and perform so long.  Polycarbonate
> also has adequate UV protection.  My companionway Hatch cover is over 20
> years old, no crazing
>
> As I noted previously I work as an Industrial Designer designing products
> so I have engaged using many materials.  Purchasing plastic sheets can be
> done through McMaster Carr, which I use all the time when I want something
> really quick, anything at all.  But I know that McMaster does sell
> everything *at a premium* because they carry so much inventory. of just
> about everything
>
> That being said I went to Boedeker Plastics which we use when we buy sheet
> acrylic , polycarbonate, ABS, etc.. etc stock for prototype building.
>
> here is the quote I got for the same material:
> POLYCARBONATE LT GRAY 7130 SHEET .500
> External
> Inbox
> Search for all messages with label Inbox
> Remove label Inbox from this conversation
> Nick Periman <nickp at boedeker.com>
> 4:43 PM (0 minutes ago)
> to me
>
> POLYCARBONATE LT GRAY 7130 SHEET .500 X 24 X 48” - $140.90
>
>
>
> In stock
>
>
> --As far as aircraft canopies here is a reality reference from a  group
> chat of aircraft engineers:  The canopies on the McDonnell Douglas (now
> Boeing) F-15A, B, C, and D fighters are made of Lexan, a type of
> polycarbonate (i.e., thermoplastic resin). I would imagine that the F-15E
> Strike Eagle uses Lexan, too.
>
> General Aviation (GA) light aircraft (C-172, C-150, Beechcraft Bonaza G36,
> etc.) use optical quality acrylic windshields. Acrylic is prized for its
> light weight.
>
> There is an FAA bird strike test requirement on acrylic GA windshields. I
> don't know what the parameters of the test are other than to say it
> involves launching 8 lb. bird carcasses at the windshield.
>
> Regards,
> RTFM
> *Support the U.S. Space Program. "No bucks, no Buck Rogers."*
> <http://www.nasa.gov/>
>
>
> https://www.watchuseek.com/threads/ot-question-what-are-aircraft-windows-made-of.407492/
>
> *Cheers*
> *Jeff Kapec*
> *Petite Suite  718*
>
> Jeffrey Kapec
>
> *Tanaka Kapec Design Group*
>
> 11 Brookfield St.   Norwalk, CT 06851
>
> 203.846.3666
>
>
> www.tkdg.com<http://www.tkdg.com>
>