Picking Plywood for opening windshield.

[Mark42]

Last summer I made two window frames from PT 1x4, ripped and biscuit joined to make the trapezoid shaped window frames. But after the glue was set, I wasn't happy with the results. The 1x is actually 3/4" thick, and I didn't like the way it looked, and it wasn't as rigid as I would have liked.

So today I went to the lumber yard and ended up buying a sheet of 5/8" Fir CDX called PTS for Plugged, Touched and Sanded. So it is exposure 1 (hot pressed exterior glue), interior voids filled, and sanded on one side. Kind of a poor mans marine ply.

This time the window frame will be cut out as one piece from the plywood, so no corner joints to mess with. They will look like these from last year with additional bracing.

The additional bracing will be pieces of ply ripped to 1-1/2" that are glued to the inside opening at 90* to the frame. When the window closes, these braces will fit into the opening in the hard top. Should make for a rigid window frame. The outside will be rounded over with a router, then covered in poly and glass, and painted to match the top.

I hope this time the frames come out rigid and flat enough to work with the top. Thats one of the reasons I chose the PTS ply rather than regular CDX or PT. I'll keep you posted on the progress.

 

[matt9923]

Re: Picking Plywood for opening windshield.

I am looking forward to seeing the finished product.
Matt

 

[Chris1956]

Re: Picking Plywood for opening windshield.

Mark, I am concerned that the plywood will seperate due to the moisture. I presume you will be using marine spar urethane for the finish?

Please post back with the results, and good luck with that stuff.

FWIW, I would have stuck with the PT solid lumber. Maybe used some 5/4 or 2 by for the frames.

 

[Utahboatnut]

Re: Picking Plywood for opening windshield.

That will probably work pretty well the pieces glued to it on the 90 deg angle will be key for it not to want to bow or twist ply is funny when you take that much away it gets real weak as I'm sure you know. The glue will have to be done well as ply doesn't take fastners in the edge well as i'm sure you also know. Could you use the ply on the frames and solid wood on the brace parts then you could glue and screw with great success. Go slow with the router ply doesn't like to be routed too much it will work but go slow. I think theoriginal units were fine although a half lap would have made for a much more solid corner you have about 5 times the surface for the glue to work with and it can be screwed as well. Good luck I would love to see them when they are finished. Are you going to use glass or plexiglass for the windows?

 

[Mark42]

Re: Picking Plywood for opening windshield.

Mark, I am concerned that the plywood will seperate due to the moisture. I presume you will be using marine spar urethane for the finish?

Please post back with the results, and good luck with that stuff.

FWIW, I would have stuck with the PT solid lumber. Maybe used some 5/4 or 2 by for the frames.

The frames will be glassed over with some 6 oz glass and poly resin. They won't be in direct extended contact with water like the transom is, so I'm thinking that should suffice. I was going to use PT ply, but was afraid after cutting it all it would warp. A little warp is OK for a deck where it is screwed down, but not for these window frame. I went with the 5/8 because I want it to be as flush with the top as possible and look factory rather than a fabricated add on.

That will probably work pretty well the pieces glued to it on the 90 deg angle will be key for it not to want to bow or twist ply is funny when you take that much away it gets real weak as I'm sure you know. The glue will have to be done well as ply doesn't take fastners in the edge well as i'm sure you also know. Could you use the ply on the frames and solid wood on the brace parts then you could glue and screw with great success. Go slow with the router ply doesn't like to be routed too much it will work but go slow. I think theoriginal units were fine although a half lap would have made for a much more solid corner you have about 5 times the surface for the glue to work with and it can be screwed as well. Good luck I would love to see them when they are finished. Are you going to use glass or plexiglass for the windows?

Yeah, fastening is an issue. Especially screws in the edge. Not sure if regular water proof carpenters glue should be used or something like PL or just epoxy. Open to suggestions here.

Hopefully the fiberglass/resin will add some strength. After glassing, a piece of PVC millwork will be glued/screwed to the inside opening for the glass to rest on. So far the plan is to use laminated safety glass because of the windshield wipers. Wipers will make a real mess out of plastic windows, especially with dried salt spray on them.

If this set of frames do not work out, the windows just won't open.

 

[Mark42]

Re: Picking Plywood for opening windshield.

Updated the main hard top thread to show the window frames being made:

http://forums.iboats.com/showthread.php?t=222154&page=8