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Re: Strip: Building a "glass" bottom kayak
By:Bill Hamm
Date: 8/20/2012, 2:40 am
In Response To: Re: Strip: Building a "glass" bottom kayak (Paul G. Jacobson)

: Ignore the worry about scratches on the outside of the boat. Water
: fills them in and they are invisible when wet. Keep the inside
: free of scratches by covering it with a clean towel when not in
: use, and take care brushing out sand which gets tracked in.

: fiberglassing over the plastic window is a waste of time. It won't
: solve leak problems or scratching, and it won't be clear enough.
: It wil also cost you more time and oney for the wasted
: materials.

: Get lucite, plexiglas or other acrylic glazing materials from your
: local hardware store or supercenter. You can cut it yourself, or
: have them cut it to size. one or two pieces should do. A
: 20" by 20" piece can be cut in half to give you 2
: 10" x 20" windows--one for each side of the hull. That
: way you can keep your center strip or three strips, to keep the
: keel area of the boat strong and continuous. Put the window
: areas on either side of the keel.

: You will put the window plastic in place just like you install a
: deck hatch. Put a lip on the inside of the hull, After the boat
: has been glassed, add something for a gasket, place the plastic
: over the lip and screw it down, or glue it in with a marine
: bedding compound like 3M's 5200. Don't expect the plastic to
: bend. plan to put the windows on flat areas of the hull. by not
: bending the plastic over the keel you should be able to find
: relatively flat areas on either side. If you use closely spaced
: bronze or stainless steel bolts to hold the window tight against
: the gasket you'll be able to replace the plastic every few years
: when it gets too scratched. You'll probably want to pull it out
: when sanding the boat, too.

: If it leaks, redo the gasket. Or live with it. At a depth of less
: than 6 inches, the water pressure on the gasket is going to be
: less than 1/4 psi, which is pretty easy to deal with.
: A bead of household caulk would do well. so would a strip of closed
: cell foam insulation. Cut the ends at a long angle and overlap
: them.When you tighten down the window the pressure will pull the
: joint tight together and keep out leaks.

: Definitely give you way too much distortion. It looks clear on wood
: because it is sitting right on top of the wood.

: I think the first postings I did on this list back in the early to
: mid 1990s were on this topic. Might want to check the archives
: for some (really) older posts on this topic. it keeps coming up.

: Hope this helps

: PGJ

There are different coeficients of expansion with wood and any plastic. Wood expands much less with a temperature increase than any plastic. So you'll need a flexible gasket and room for the plastic to move when it expands in it's frame. It also means the screws used to attach the window can't be "screwed down tight", there has to be room for the plastic to move or when it does move it'll crack.

Bill H.

Messages In This Thread

Strip: Building a "glass" bottom kayak
IgnorantWanderer -- 8/15/2012, 6:34 pm
Re: Strip: Building a "glass" bottom kayak
Allan -- 8/15/2012, 7:07 pm
Re: Strip: Building a "glass" bottom kayak
scottbaxter -- 8/15/2012, 10:20 pm
Re: Strip: Building a "glass" bottom kayak
Paul Davies -- 8/16/2012, 6:13 pm
Re: Strip: Building a "glass" bottom kayak
Will Nettles -- 8/16/2012, 8:32 pm
Re: Strip: Building a "glass" bottom kayak
ancient kayaker -- 8/16/2012, 11:03 pm
Re: Strip: Building a "glass" bottom kayak
ancient kayaker -- 8/16/2012, 11:06 pm
Re: Strip: Building a "glass" bottom kayak
IgnorantWanderer -- 8/17/2012, 9:04 pm
Re: Strip: Building a "glass" bottom kayak
ancient kayaker -- 8/17/2012, 11:11 pm
Re: Strip: Building a "glass" bottom kayak
IgnorantWanderer -- 8/18/2012, 1:30 pm
Re: Strip: Building a "glass" bottom kayak
Etienne Muller -- 8/18/2012, 3:29 pm
Re: Strip: Building a "glass" bottom kayak
John Abercrombie -- 8/18/2012, 4:33 pm
Re: Strip: Building a "glass" bottom kayak
Paul G. Jacobson -- 8/19/2012, 5:03 pm
Re: Strip: Building a "glass" bottom kayak
Bill Hamm -- 8/20/2012, 2:40 am
Re: Strip: Building a "glass" bottom kayak
John Abercrombie -- 8/20/2012, 2:21 pm
Re: Strip: Building a "glass" bottom kayak
ancient kayaker -- 8/17/2012, 11:16 pm
Re: Strip: Building a "glass" bottom kayak *PIC*
Yostwerks -- 8/18/2012, 2:02 am