Silicone Sealant for new Portlight Seals??

[CJ13]

I’ve just bought new seals for Lewmar Opening Portlights ( at vast expense!)
The instructions say that the new seal should be fitted into the aluminium frame on a bed of ‘Silicone’. I’ve never used Silicone on the boat. Presumably a Hybid Polymer sealant like CT1/ OB1 would do the job?

 

[Plum]

I’ve just bought new seals for Lewmar Opening Portlights ( at vast expense!)
The instructions say that the new seal should be fitted into the aluminium frame on a bed of ‘Silicone’. I’ve never used Silicone on the boat. Presumably a Hybid Polymer sealant like CT1/ OB1 would do the job?

They are more adhesive than sealant. When I replaced my lewmar hatch seals the silicone acted as a good "lubricant" to aid getting the seal into the locating groove and was then easy to clean up. You may find this recent string of posts useful Best silicone adhesive

Www.solocoastalsailing.co.uk

 

[robmcg]

I agree with Plum. Using CT1/OB1, you'll never get them off intact again. I used standard cheap silicone sealant in a little toothpaste like tube. It doesn't see any UV and has worked fine now for the last two years.

 

[coopec]

Have you considered using Butyl Tape?

Replacing Lewmar Portlights

https://ericsonyachts.org/ie/threads/re-bedding-a-lewmar-hatch.17949/

 

[Praxinoscope]

Replacing our Houdini hatch, Houdini recommended using Butyl sealant and in fact supplied a cartridge of it with the hatch, my only problem is that like its silicone relative it seems to go everywhere except where you intend.

 

[coopec]

Replacing our Houdini hatch, Houdini recommended using Butyl sealant and in fact supplied a cartridge of it with the hatch, my only problem is that like its silicone relative it seems to go everywhere except where you intend.

Why not use Butyl Tape?
It is attached to wax type paper so it won't stick to itself.

 

[CJ13]

I’m not replacing the hatch, just the ‘rubber ‘ seal between the frame & acrylic glass, so sounds like Silicone it is.

 

[dankilb]

Go for a neutral cure silicone. The ‘structural glazing’ varieties have the highest bond strength. As I posted on the thread linked above - we’ve used options from Dow for similar projects recently, either 791 from Screwfix or 895 available online (and slightly pricier but ostensibly higher spec for tsunami and seismic -proof skyscraper windows, apparently).

 

[dankilb]

Presumably a Hybid Polymer sealant like CT1/ OB1 would do the job?

Be careful - sealants with polyurethane can be impacted by the high UV levels when bonding glazing and plus they can react adversely with some acrylic (edit - sounds like you’re bonding to the frame and not in direct UV - still not an ideal use for hybrids, especially if silicone is recommended).

That’s why Sika sell a special product system, making a project like yours upwards of £100 (inc primers, cleaners, etc.), to use with acrylic glazing.

 

[coopec]

I’m not replacing the hatch, just the ‘rubber ‘ seal between the frame & acrylic glass, so sounds like Silicone it is.

OK! I with you now. Glass (Acrylic?)/rubber seal/ aluminum frame.

I've had the same problem with mine so I used a one part "super glue" that I bought cheaply on eBay to glue the rummer to the aluminum frame. So far so good but I'm not holding my breathe

What is the best adhesive to stick rubber to Aluminium?
When gluing metal to rubber a cyanoacrylate based adhesive, like our Super Glue, would be ideal, as it provides a flexible, but incredibly strong bond. It also has the added benefit of drying very quickly.24 Oct 2019.

Guide to Glue on Metal - Our Tips | Gorilla Glue UK

 

[thinwater]

Not just any hardware store silicone. One rated for glazing. There is another thread on here somewhere that seemed to conclude that Dow 791 was a good product available in the UK.

 

[Plum]

OK! I with you now. Glass (Acrylic?)/rubber seal/ aluminum frame.

I've had the same problem with mine so I used a one part "super glue" that I bought cheaply on eBay to glue the rummer to the aluminum frame. So far so good but I'm not holding my breathe

What is the best adhesive to stick rubber to Aluminium?
When gluing metal to rubber a cyanoacrylate based adhesive, like our Super Glue, would be ideal, as it provides a flexible, but incredibly strong bond. It also has the added benefit of drying very quickly.24 Oct 2019.

Guide to Glue on Metal - Our Tips | Gorilla Glue UK

The Lewmar seal shown in your photograph does not need to be bonded as it it retained in place by the arrow-head moulding that is pushed into the slot in the aluminium frame using a little silicone sealant. Instructions are here Old Std Portlight Seal Fitting Instr..pdf

Www.solocoastalsailing.co.uk

 

[coopec]

The Lewmar seal shown in your photograph does not need to be bonded as it it retained in place by the arrow-head moulding that is pushed into the slot in the aluminium frame using a little silicone sealant. Instructions are here Old Std Portlight Seal Fitting Instr..pdf

Www.solocoastalsailing.co.uk

I know nothing about Lewmar seals so I won't argue with you.

My ports haven't got a "cavity" and they were leaking (slightly) but I fixed the problem by making "rain diverters", Problem solved!
But I'm surprised you say the seal does not need to be bonded.
https://www.catalinadirect.com/images/features/Lewmar New Standard Portlight Gasket Installation Updated.pdf?CFID=14415088&CFTOKEN=f939b2ad4289dff2-C810B7CE-9E04-F451-5FAB5770116AB636

 

[CJ13]

My seals are Lewmar and are well secured into the frame in a ’Z’ rebate, so the sealant is just that- belt and braces. I presume the original sealant is silicone as the instructions say remove it prior to fitting the new seals/ sealant, which would be difficult with an adhesive sealant.
Dow 791 sounds like the right option.
Thanks all for the input.

 

[coopec]

My seals are Lewmar and are well secured into the frame in a ’Z’ rebate, so the sealant is just that- belt and braces. I presume the original sealant is silicone as the instructions say remove it prior to fitting the new seals/ sealant, which would be difficult with an adhesive sealant.
Dow 791 sounds like the right option.
Thanks all for the input.

This guy may be worth contacting?
He claims "I have many years experience of selling Lewmar products and have extensive knowledge for providing spares for winches, windlasses, steering and deck hardware "

This is a regular stock item, if it shows no stock please contact me

I have 2 x 1 mtr length available of NS seal which I will discount with a partial refund if you buy them

You will also need

Super glue suitable for rubber for the end to end butt joint

A good quality marine silicone sealant to hold seal in place

I can supply you with a 3 gram tube of suitable super glue and a 78 gram of clear marine silicone

If your order is 8 meters or under just add another meter to your order and send me a note that you want glue & sealant

if your order is 9 meters or more I will send glue & sealant free of charge only if you request them​

LEWMAR Standard Portlight Old & New Replacement Seal Locations OS 2/5 & NS 2/6 | eBay

 

[doug748]

The instructions I have seen say use Silicone sealant and it tells you why. I would use anything leftover or the £1 a tube stuff, it's fine for this application

 

[Frankklose]

This is what butyl looks like after a hot summer....get´s worse every year. Smires very difficult to clean, wish that I would never ever heard about butyl.....If you want to get into this mess use it..every of my windows looks like it. the stuff get´s liquid with heat.....take it as a warning. in the first few years every thing was ok ...I sought that it was a very good material until we had the hot summers.

 

[coopec]

View attachment 146119

This is what butyl looks like after a hot summer....get´s worse every year. Smires very difficult to clean, wish that I would never ever heard about butyl.....If you want to get into this mess use it..every of my windows looks like it. the stuff get´s liquid with heat.....take it as a warning. in the first few years every thing was ok ...I sought that it was a very good material until we had the hot summers.

Well the advocates of Butyl tape wouldn't agree with your post!

"Do you need a reliable and durable tape that can withstand extreme temperatures? Butyl tape may be the answer. This heavy-duty adhesive is commonly used in construction and automotive applications where a watertight seal is required."

Butyl Tape: The Ultimate Guide | General Sealants, Inc.

 

[Frankklose]

The advocates have perhaps not used it for a longer period....I used used it for about 7-8 years ago on every window. My Moody34 has a number of windows....it means I have to take them out , one by one and do the job again.
As said, it was ok for a number of years, but got worse year by year.....
I think the photo shows what I mean...Butyl is rubbish...

 

[TSB240]

A lot of time can be wasted replacing the portlight seals on the older lewmar port lights with the rotating catches.

Do you have water collecting at the bottom in the cups of the port light catches?

If you do it is more likely the exterior seal between the top and bottom halves of the portlight aluminium extrusion have broken down.
These seals harden and shrink with age. They then channel water from outside into the hollow extrusion of the portlight frame which then flows out of the holes at the bottom on the inside of the catch cups.

It us all too easy to assume it is the portlight seal has failed.

You can remedy this by scraping and hooking out the joints outside and filling them with sealant. This is a temporary repair and will last a short time. A longer term fix is to remove the inner trim and clamping plate and fill the hollow extrusion back to the joint with silicone through the clamping plate screw holes. This can be done without either breaking the portlight to cabin exterior seal or removing the portlight entirely.

Common leaks through the portlight perspex on loose rotating catches can simply be stopped by replacing the o rings and adding a little silicone grease. The rubber o rings harden and disintegrate with strong UV.

I had to do this on 10 portlights to solve the leaks on our Lewmar leaking portlights.

I have not had to fit any replacement portlight sealing strip yet!