New port lights - advice please

[SeaHusky]

I am replacing the old plexi(?) port lights with new ones and I have chosen hard coated polycarbonate. As you see they are the simple "bolt onto the GRP cabin" type with a one inch overlap all round. You also see that the old ones were fitted with a bolt every two inches.
I wonder if I should simply copy the old ones or drill the new ones perhaps using only every other bolt hole or so? The holes in the cabin are already there but I will drill as many as I need in the new polycarbonate. I am thinking that forces will be pressing against the outside but the holes may weaken the design. On the other hand perhaps less holes/bolts put more stress on each bolt hole and therefore more is better?

[CharlieJ]

If it were me, I'd drill all the holes, slightly oversized (say a 64th), no countersink, and use pan head screws (or bolts)

[Jim_ME]

Agree with Charlie to reuse all existing fastener holes. One of the purposes of the close spacing is to keep the materials as flat and the pressure on the sealant as even as possible.

[SeaHusky]

Thanks! I will use all bolt holes as suggested.
Any tips on working with butyl in this case to make it look good and avoid a mess?
I also want to use some "shading film". Should I apply it to the outside or inside?

[ralay]

Out of curiosity, CJ, why no countersink?  Just to have the full thickness?

[CharlieJ]

Nope- countersinks in plexi or lexan act as wedges The screws expand and contract in both heat and cold, at a much different rate than the plastic. Countersinking would tend tom break out right at the edges. Also the reason I said drill slightly oversized holes NOT a snug fit.

[CharlieJ]

I also want to use some "shading film". Should I apply it to the outside or inside?

On board Tehani I use a self cling vinyl I get from sign shops. You dampen the window, and sqeegee the vinyl on  When you want it gone, just peel it off- no residue. Then goes right back on with a damp sponge. When I don't want the ports covered, I store the vinyl under a bunk cushion

You can see what it looks like on the port in this pic

[doug]

While not inexpensive we have been happy with these blinds:

http://www.zarcor.com/products/clozures/#gal-image-0

They used to be called peek-a-boo blinds. Had them 5 years now without any trouble.