Redoing my fixed portlights (deadlights)

[sanibel sailor]

My Bristol 35.5 has a pair of fixed portlights on either side, more correctly referred to as deadlights. They all leak, and the Plexiglass is crazed. The lenses are set between two brass trim rings, the inner with countersunk holes and the outer tapped for 10-24 machine screws. The rings are 3/16" thick and the holes are blind, so only a few threads have bite. Looks nice from exterior without fasteners. The plastic is a good bit smaller than the opening, with only about 1/4" overlap for a sealing surface.
Deficiencies- narrow sealing surface allows leaks, poor fastener strength, mechanically may be stronger with wider amount of plexi between rings.

I am thinking of re-engineering it. Putting the countersunk ring outside, tapping holes all the way thru the new inner ring, with acorn nuts on the interior surface and a wider piece of plexiglass (with widely overdrilled fastener holes) in between. I will still leave a gap for thermal expansion all the way around.

I will post pics in a bit

Any thoughts or unforseen problems?

[sanibel sailor]

Interior pic

[Terra Nova]

Originally Posted by sanibel sailor

...I am thinking of re-engineering it...

** **

[sanibel sailor]

Proposed ring swap, current starboard inner becomes new port outer. BTW fore and aft ports are identical

[Orion Jim]

If you make the swap you'll have a dozen fasteners just dying to channel water to the interior. It's hard to visualize remotely but I'd reinstall after bedding as originally done and consider removal and rebedding a normal maintenance project every three, five, seven, years as necessary.

[Hudson Force]

I've had polycarbonate (Lexan) portlights for many years and I continue dealing with the hazing. I'm considering changing to acrylic (Plexiglass) at 12mm thickness. The Dow Corning 795 silicone buliding sealant has received some good reviews and I'll try this without any drilled fasteners. My present polycarbonate plates are set in gaskets, but I'll have my new pieces larger and pressed to the fiberglass at a perimeter larger than the opening that they are covering and supported along their bottom edge. I'm relying on their potential impact pressures from outside the vessel and not from within.

[robert sailor]

Originally Posted by Jim Walsh

If you make the swap you'll have a dozen fasteners just dying to channel water to the interior. It's hard to visualize remotely but I'd reinstall after bedding as originally done and consider removal and rebedding a normal maintenance project every three, five, seven, years as necessary.

I'm with Jim on this one, we are right in the middle of rebedding ours..not fun work

[Hudson Force]

I see many successful seals and beddings of portlights without fasteners. What about routing out a setting and bedding without the fasteners or the frame?

[redsky49]

I am also a Bristol owner and have similar, if not identical, fixed ports.

In my experience, the problem with these ports are that the outer frame is not adequately thick to allow a sufficiently deep tapped/threaded screw hole. As a result, the machine screws used to fasten the port from the interior are only able to achieve about one revolution before they bottom out. With such little purchase it is difficult to adequately torque the screws and properly tighten the fasteners to ensure no leaks.

After several frustrating years of various attempts to correct leaks, I have resorted to simply drilling out the tapped holes in the outer frames and using truss head fasteners and through-bolting the ports from the outside, with crown nuts used on the inside. The Dow silicone mentioned above has worked well for the fixed ports. For bedding material I have used butyl, 3M 4000, and a Life Caulk product - none of which appear to be a perfect product.

This also allows you the opportunity to buff the interior aluminum port frames to a nice shine

[kenamick]

I like the idea of exchanging ports from the opposite sides, but...

What if you bed the glass in 5200 of a similar product and cut threaded rod long enough to bottom-out in the threaded recesses of the outer trim and then install acorn nuts on the inside trim (which would allow more threads to really tighten it down)?

I am in the middle of replacing all 6 of my brass port holes after removing them, adding a 3.5" band of brass to the exterior trim ring and relocating each of them 1.5" down to allow for thicker cabin ceiling planks.

I'll also be installing brass acorn nuts on the interior for a better fit as well as a nice finish look.

Ken

[Steve Bean]

Will 5200 stick to remnants of silicone caulk, with or without cleaning with acetone?

[Terra Nova]

Nothing seems to stick to silicone--even silicone.

And 5200 is just about the worst choice of caulk for windows. You want something that will compress and expand easily without breaking the bond, like some of the specialized Sika products designed for bonding windows.

[ErikFinn]

Originally Posted by Terra Nova

Nothing seems to stick to silicone--even silicone.

And 5200 is just about the worst choice of caulk for windows. You want something that will compress and expand easily without breaking the bond, like some of the specialized Sika products designed for bonding windows.

+1 on that. Also I recall the correct way to go about it with Sika is that you absolutely must use the recommnded Sika primer (can't remember the name), as if you do not, the whole job will be a fail and the caulk will not bond.

I should also do this job but been hesitant as have heard of so many problems and fails, so look forward to the discussion.

(Edit: I just now tried to search online for the primer but no luck )

[UNCIVILIZED]

Before using any of the afore mentioned bedding compounds, adhesives, or solvents, make sure to check that they're safe to use with which ever material that you choose for your port lights. As some of them will soften, & or structurally weaken certain plastics.

As to concerns about impacts on the exteriors of the port lights. Realistically, it's wise to have a fair bit more than 1/4" of overlap of the port material on the hull, in order to spread out the loads from the impacts on both the ports, & the hull better.

[Terra Nova]

Originally Posted by UNCIVILIZED

...it's wise to have a fair bit more than 1/4" of overlap of the port material on the hull, in order to spread out the loads from the impacts on both the ports, & the hull better.

...and to provide adequate bonding area for the sealant.