|This is a story of a boy, his
rat, and glass bottom boats. I say "rat" because
my boat is a little wider than a mouseboat, so it must
be a rat. I'm pretty new to boatbuilding and the whole
boating world - or alien planet - and have been stymied
by the outrageous terminology I've encountered as if coined
by aliens themselves. After reading the "trow"
article and seeing the placard about "Gun Punts",
I wondered, "What planet were these people from when
they came up with these words like "trow", "copse"
and the mother of all wonders, a "whorrie" ?!?!?.
And what nautical nuts came up with "coaming",
"carling", and "gudgeons and pintles"?
So in keeping with this alien tradition, I have named
my new breed of durable, DIY glass bottoms for boats,
"Polyvuinits". Not weird enough, but it'll do.
all started when my wife and I were looking through
the boathouse at my family's vacation cabin in Michigan
and found an old fish viewing tube I used as a kid for
seeing fish underwater. Then I decided to make a large
version to sit in, and it grew in my mind to laminate
a wood cylinder with the polyvuinit at the bottom, inserting
into a large tractor inner tube, and putting a top deck
of plywood on top to sit on. Design criteria:
- a.. It had to use existing material
laying around in my shop like the bending Luaun (cool
stuff affectionately called wigglewood), a piece of
Lexan MR-10 Polycarbonate (scratchproof coating 2
sides), some ten year old West System, PL Premium
and I sprang for the top piece of 3/4 Superply, some
Marine Spar Varnish and the SS screws.
- b.. Had to be light enough to be
car - toppable
- c.. Had to be done within two weeks
of going to Michigan later that year, so it will have
to be human powered (imagine paddling something round
- makes your head spin as well as the boat).
was an absolute blast. The first night when the spar
varnish was still tacky, I paddled out with a Mag light
and saw a whole new world. I paddled back to get Tricia,
and besides this new aquatic bottomscape, we saw crayfish
and to cap it all off, a big red newt with the black
spots and those feathery things coming out of its gills.
I immediately began figuring out a way to power this
thing after rowing in circles, and during the following
winter (actually mid-summer construction) added a beavertail
to the back to mount the 30 lb thrust trolling motor,
and enclosed the bow to break the waves and house the
course it had to have front viewing windows, Bubinga
trim, a West System deck finish, outrigger snap-on floats
made of fenders for stability and redundant floatation,
and best of all, a canopy to eliminate the sky reflection
when viewing through the Polyvuinit. Going E-power still
kept it light enough to be car toppable, adding the
motor, battery (85 A/hr deep cycle marine), outriggers
and canopy after getting it into the water.
year I spent two weeks in Michigan with only one rainy
day, and boated most of them to the point that Tricia
was even sick of it. But we had so much fun seeing down
thirty feet to the bottom in Grand Traverse Bay, Torch
Lake, and seeing old dock pilings under us in Sleeping
Bear Bay as well a wreck site. The wildlife was mesmerizing
when we lowered our heads into the "hole"
to go through an old river seeing fish through the weeds.
SSSSooooo . . . getting back to the
fun part of the show. Based on the fun I had, the public
and online response to my ratboat by people who hadn't
even experienced the view, I suspect that others may
want tickets to this show. Especially when I saw those
cute little mice that Gavin has had a litter of, and
realized that those boats would be so much fun with
polyvuinits (assuming clear water).
reason you probably don't see too many glass bottom
boats, or people making them, lies in the name, hence
why I've changed the name. If you use basic glass, it
cracks, you sink. Not with Polycarbonate plastic sheet
(Lexan by GE, Cyrolon by Cyro, and Hyzod make trade
name versions of PC sheet). Used in Bulletproof laminated
glass and shatterproof applications, this is the right
stuff. Scratching a problem ? No problem with abrasion
resistant coatings when you specify AR sheets. The Lexan
AR sheet is called MR 10 and Cyro is Cyrolon AR, I think.
The only possible red flag is sealing a sheet that will
shrink in time, and has drastic expansion / contraction
rates. Just design for these limitations, that's all.
For those serious about using glass, I suspect that
double or triple pane laminated AND TEMPERED glass would
work fine as well, and would be much more scratch resistant,
just can't have holes in it - must use an encapsulating
considering cutting the hole in your boat (you'll get
over it), cut round or rounded corner shapes to ease
stress on hull opening. I am writing this article for
glass bottom electric and low power boats, as planing
hulls may put too much stress on the polyvuinit unless
scaling up the thickness and seal complexity, if you
are confidant. Also good not to put it in the middle
or anywhere that may interrupt the structural integrity
of the hull or be susceptible to scratching from the
bottom of the lake or sandy feet (foot rests are good
over the 'vuinit). My new boat will have the 'vuinit
in the center, lined up with the keel in a V-shape matching
the hull, and I will solvent weld a thick Lexan skeg
to it about 1/2" x 1" for rigidity and protection.
The 3/16" PC sheet will thermoform a good bend
at the intended ridge of the shallow vee if you mill
a V - groove down the center, 1/3 into its thickness,
heated with a PVC welder or a propane torch. Stay tuned,
as I may e-mail pics of this in progress.
diagram at right (click to enlarge) shows typical cross
sections of the seal required that give a guideline
to your glass bottom, and should be modified to your
application and requirements. The following are important
things to remember:
- a.. Make sure that all edges and
inside of screw holes have allowance for expansion
/ contraction. Allow for movement of 1/8" in
- b.. Seal edges of cutouts, pilot
holes and any milled areas with epoxy before sealing
- c.. Score mating surfaces with
coarse sandpaper, after scraping the hardcoat off
of the PC at the edges
- d.. Use plenty of silicone as a
buffer zone in the PC / hull / backing plate interface
if not using rubber gaskets. Tip: screw down PC into
wet silicone only a little to the point that there
is 1/32" or so of silicone left in the joint
- don't squeeze all the silicone out. You could possibly
tighten screws later.
- e.. If not using a backing plate
for the screws (in the case of small portholes), be
sure not to over-tighten screws in the countersunk
holes, as that is where cracks will begin (pan - heads
are good or use metal / rubber sealing washers).
So go on and do a little surgery on
your mouse, pram, dory, whorrie (in the vernacular of
teenage girls - "WHAT EVER!") and have fun
in your "research vessel", as the Michigan
DNR guys called my rat-thing.
Blazy studied furniture design at Rochester Institute
of Technology, has two patents in polymer science
and one in design, and invented one of the wildest
architectural glass products in the world.