How to Bed Port Glass

Do you need to bed port glass in your boat?

If you have a boat, chances are you have needed to know how to bed port glass. In our first boat, we had aluminum framed fixed ports in the galley and at some point they leaked. In our next boat, we had 14 Beckson opening ports and we had a few of those that developed leaks in the sealant around them over time.

This is not an uncommon phenomenon. Consider the pressure these are under as the boat flexes coming off of waves and seas. Think of the sealant breaking down in the UV over time and it is no wonder that these are maintenance items on a boat. Ignoring a leaking port can lead to extensive damage, so it is always good to check and do proper maintenance on these.

Prepare to bed the port glass

Prepare the surface

The first thing to do is to properly prepare the surface that the glass or frame is going to be put into. I start by ensuring that there is NO left over sealant from the old port or port glass. Depending on the material there are several ways to do this. With SVDreamChaser, the bedding surface is wood, so I like to use a flat router bit to remove and clean any sealant off the wood. For other surfaces use the proper solution, this may be a scraper or sealant remover or sandpaper.

Remove the old sealant

In almost all cases you want to avoid silicone to seal ports. The only place I have ever had this recommended for use is on the Plastic Beckson brand ports. They are held onto the boat by being through bolted so the silicone they call for is 100% a sealant and NOT intended to be used to hold it in place. On many other boats, there is a need to use an adhesive to hold the port in place. That is the case on SVDreamChaser.

Once the surface is free of all old sealant, it should be rough sanded with 60 or so grit sandpaper being careful not to scuff the visible paint job around the perimeter of the port glass. This is to provide a surface to allow the adhesive to get a little “bite” and hold better.

Material to Bed Port Glass

The old debate

This may be more debated than the Monohull vs Catamaran question in the sailing community. What I have here is my researched opinion and It has served me well over the last 12-15 years or so while sailing and living aboard for half of that time.

Don’t use Silicone to bed port glass

Beckson ports aside, choose a good adhesive material that is removable. As I mentioned before rebedding glass should be viewed as a possible maintenance item and you want to avoid using something that prevents you from being able to perform that maintenance in 5-10 years.

Make it workable in the future

That means you should avoid things like 3M 5200. While it would likely do a great job of holding the glass in place, it will not come out without likely breaking the glass or bending the frame in the future. 3M 4200 is sort of the weaker cousin to 5200 and could be used but is still VERY hard to remove.

I am a fan of BoatLife LifeSeal as well as 3M 4000. 3M 4000 is a flexible UV resistant material that has about equal parts adhesion and sealant properties. On SVDreamChaser the ports are very large (3 ft X 2ft) and we have 6 of them on the coach house. This means that there is a lot of sunlight and a lot of glass surface area to be absorbing all that sealant.

I use almost a full tube bedding each port glass. I want something that remains flexible. One other note, these recommendations are for ports that are NOT going to be submerged. This is a completely waterproof seal but this should not be used on a port that sits below the toe rail and finds itself under water regularly at a healing angle. I can think of some of the early 2000 Hunters that had those long narrow ports near the aft stateroom that often were partially underwater when sailing.

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How to Bed Port Glass

I put painters tape 1/4-1/8 inch around the exterior surface of the window frame or glass. Doing this will allow you to smooth the material and peel the tape up for a nice smooth finish. With the surface clean, cut the correct angle size on the tube tip. Penetrate the hole seal inside of it and apply a thick bead all the way around the bedded surface that the glass or frame will sit into.

Making it look neat

With a bead, all the way around, lay the glass into the port and press to get to the position you desire, often flush with the exterior side wall or surrounding surfaces. I always wear nitrile gloves when I do this (if you have a boat, you should have them on hand). Quickly after you have put the glass in you want to smooth the sealant. I say quickly because this sealant will begin to “skin” over in about 20 minutes. Wet the ends of the fingers of the glove (I often just use a little bit of spit) but a cup or bowl of water would work great too.

With a wet finger, gently smooth the material to form the shape of the final bead that you want. I would recommend practicing this before you actually bed your glass on some scrap material to get the feel for how it works. As soon as you smooth it around the whole bedded glass, peel the tape off quickly. It is important you do this quickly because of the material has begun to “skin” it will stretch when you remove the tape like gum and leave a messy edge that will require clean up with a razor blade.

Finishing the bedded glass

Once dry it is time to trim any areas needed with a razor blade or exacto knife. I often will have to still apply a cleanup bead on the inside of the frame to give it a finished look which I do after all has set and the outer edge is sealed and smooth

Viola! You have bedded your port glass.


If you like this episode, by all means, please do share it with your friends that would benefit from it and don’t forget to subscribe for new episodes every Friday. We have done a couple of videos specifically on which materials to use for different glass materials as well. See it here.

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