gasket for Lewmar opening portlite, old standard

[HerbertFriedman]

I'm not sure what you have in mind, or in hand, for a"soft buna O ring". It is important to have the right balance between enough firmness to make a good seal but not so much as to overstress the portlight components. An old gasket I have is 5/16" thick when relaxed, and when squeezed firmly (but not painfully) between finger and thumb, compresses to about 1/8" thickness. If your "soft buna O ring" has similar compressibility, it may be suitable. If the gasket is too firm, I would be concerned about having a uniform seal all around.

Regarding the arrowhead and the slot: Silicone was used by the previous owner of my boat. I agree that cleaning that slot can be tedious, but I managed it for my 5 ports. And they will likely never see sealant again, because I see no need for it. The gasket and slot appear to be intended to secure the gasket in place without the use of adhesives, in spite of any instructions otherwise. I have found that when the arrowhead is inserted into the slot all way around, the gasket, when new, will stay generally in place except when it sticks to the lens, thus the need for lip balm.

With a correct gasket, the seal is formed at the edge of the lens, with the gasket forced into the corner of the frame. With a foam rubber cord, the best we can do is to secure the gasket as close to the corner as possible and the seal will mostly be between the flat exterior face of the lens, and the parallel surface of the aluminum, with the gasket pinched between them. The tape, if used, would be between the gasket and that same parallel surface, but I don't think the tape will either contribute to nor detract from the seal, but will only serve to keep the gasket in place when the lens is open. Maybe the tape won't work long term, but it seems like it might be useful while working out best choice of gasket material rather than a more permanent adhesive like contact cement.

the "soft buna O ring" that I was referring to was in McMaster-Carr online catalogue. They showed buna O ring stock with two hardness specs, one regular and the other "soft" but no values of modulus given. I just thought that all I am trying to seal is rainwater, little or no pressure, so that the soft version might be better since there is not much force exerted by the window. That is why the idea of a foam rope seemed possible too.

I agree that the arrowhead in the cavity is just to hold the O ring from falling out, especially if the window "sticks" a little to the O ring. So the lip balm makes sense, I actually put a thin layer of water proof grease on the O ring for that purpose, messy but seems to work, no sticking. And I agree that I dont know were the sealing surface really is between the O ring and the aluminum frame, that is why I was thinking of gluing the O ring into the aluminum frame on every surface where it touched the frame. maybe double sticky as a first try although I dont know how waterproof that is.

 

[peaman]

Looking at the buna O rings on this page of the McMaster catalog, I have concerns about the softness, among others. The softest selection listed has a durometer rating of 50A, which near as I can find is harder than a common pencil eraser, which is a good deal more firm than the correct gasket. For that reason, I think something which can be characterized as a "foam" rubber material will probably be more suitable.

I just thought that all I am trying to seal is rainwater, little or no pressure,

If you aren't real adventurous, that might be all your port lights will see. But in heavy storms, and especially when sailing in rough seas, you could very well see substantial pressure. Imagine a five gallon bucket of water dumped forcefully directly at the portlight. A gasket too soft or with inadequate pressure to hold it in place could well be dislodged.

 

[Christian Williams]

LEWMAR Standard Portlight Old & New Replacement Seal Sold length by the meter | eBay

May 2023; this seal is not from Lewmar, but does fit the Old standard portlights. February 2022 Lewmar have discontinued this seal as a spare. OS seal is 9 x 12 mm. FOR YOU TO CUT TO LENGTH USING THE OLD SEAL AS PATTERN AND GLUE THE ENDS TOGETHER WITH SUPERGLUE.

www.ebay.com

 

[HerbertFriedman]

LEWMAR Standard Portlight Old & New Replacement Seal Sold length by the meter | eBay

May 2023; this seal is not from Lewmar, but does fit the Old standard portlights. February 2022 Lewmar have discontinued this seal as a spare. OS seal is 9 x 12 mm. FOR YOU TO CUT TO LENGTH USING THE OLD SEAL AS PATTERN AND GLUE THE ENDS TOGETHER WITH SUPERGLUE.

www.ebay.com

thanks Christian, I see by the diagram that this seal is not just a solid O ring (with the arrowhead appendage) but rather a hollow core, so my idea of a standard O ring probably is the wrong approach. I hope this e-bay listing is still in effect.

 

[Prairie Schooner]

I wonder if one of these would work?

 

[HerbertFriedman]

I wonder if one of these would work?

View attachment 51705

View attachment 51706

I thought that a foam rope might work but Christian did find a link on e-bay which seems to have some stock for the old standard Lewmar port lites. I dialed onto the e-bay site to see it was still active and appears that it is.
https://www.ebay.com/itm/222070285881. It is in roll form so I will have to glue the ends but it looks right.