Fore Hatch Lens replacement advice, please.

[StUrrock]

Hi , some tips from hatch experts would be useful and gratefully received.

We have an old fore hatch which has developed leaks down some of the screw holes which secure it to the frame.
To be honest some of the screw hole threads are pretty much stripped.

Please see picture below;



My logic is telling me that screw holes like this are not a good idea and would make leaks more likely.

So I have had a new lens made (not expensive!) without the screw holes.

The plan is plan to secure it down using just a hybrid Silicone/Polyurethane as per this you tube video with virtually the same hatch

(The gentleman in the video uses Boat Life-Life Seal)

I have 3 questions;

1. Would this method of fixing the lens be strong enough just using a product like this?
2. Should we fill the screw holes in the metal frame with something like JB weld before apply the Silicone/Polyurethane?
3. Boat Life-Life Seal seems quite hard to get hold of here in the uk so are there any Silicone/Polyurethane alternatives.

Many thanks and compliments of the season to you all.

 

[MoodySabre]

When I had mine done (Lewmar hatches so no screws) the glazing was bedded in with CT1. If you put this round the frame then it should also seal the holes.

 

[StUrrock]

When I had mine done (Lewmar hatches so no screws) the glazing was bedded in with CT1. If you put this round the frame then it should also seal the holes.

Many thanks that looks just the job!!

 

[Neeves]

Companies like Sika make sealants/adhesives specifically for the application you describe. Look at their portfolio of products and go from there. If in doubt telephone SIKA (I assume they have a UK office). When they advise you what to use - follow the instructions meticulously - for many of these products cleaning up is easy with turps - but turps in many cases will wick into the joint and reduce bond strength. I'd suggest the material used here - but its locally made and unlikely to be available in the UK - but as far as I am aware its similar to your CT1 (and others in the range). 3M made a product specifically for bonding glass in high rise buildings, curtain walls and the like - they provide another option. Our windows in our cat were a 3M product - the same as used in the Petronas Tower in KL.

Jonathan.

 

[Boathook]

When I renewed the clear plastic on my giot? aluminium hatches the cleaning was important. The aluminium and or the plastic was primed and put together with a 3M clear silicone. I took the hatch lids home one at a time and did the work in my garage. Not that it was warmer but dry and the curing took a few days.
All this was quite a few years back so events a bit hazy!

Edit bit. For plastic read a type of expensive perspex.

 

[Daydream believer]

I would still put 4 or 8 screws in so that when the adhesive fails you do not get a catasrophic failure at sea

 

[Graham376]

I used arbosil 1096 when replacing acrylic in deck hatch and framed windows, still fine after 12 years.

 

[neil_s]

I used silicone when I did mine many years ago. There were two screws just to locate the plastic while the mastic set.

 

[StUrrock]

Thank you all so much for taking the time to reply, all input was gratefully received.

What a great resource this forum is!

We have taken the advice re the screws, but I have decided to take a chance just using CT1, will let you know how we get on.

Photo attached showing the hatch weighed down shortly after bedding it in....

 

[mrangry]

I would still put 4 or 8 screws in so that when the adhesive fails you do not get a catasrophic failure at sea

The problem with this is as the acrylic expands and contracts thermally it can crack and stress the lens.

 

[Daydream believer]

The problem with this is as the acrylic expands and contracts thermally it can crack and stress the lens.

Not if you put 4mm bolts in 6mm holes & bed in a flexible non setting mastic

 

[Keith-i]

I had to rebed the lense in my Goiot hatch last year. I spoke to Dow Corning and they recommended a particular frame sealant designed for bonding structural glazing to aluminium frames. So far so good with no leaks or expansion problems. From memory it was a kind of neutral cure silicone.

 

[Boathook]

Not if you put 4mm bolts in 6mm holes & bed in a flexible non setting mastic

Shouldn't require screws. Any seas landing on the hatch force it down and the screw holes will eventually leak. My hatches have been fine for many years and don't have screws holding the perspex in place.

 

[KREW2]

I did the hatch on my Storm a few years ago. Sika 295 is the recommended product. You will also need Sika 210 primer. Unfortunately you only need a soup spoon of it, the smallest amount you can buy is 250ml, it has a short shelf life, and is costly.
There are some good videos and instructions on line on how to do it, masking is the key.
No screws necessary

 

[claymore]

I would still put 4 or 8 screws in so that when the adhesive fails you do not get a catasrophic failure at sea

Agree with that - Glue it and Screw it - just to be sure!

 

[Poignard]

Shouldn't require screws. Any seas landing on the hatch force it down and the screw holes will eventually leak. My hatches have been fine for many years and don't have screws holding the perspex in place.

I read somewhere that the hatch must also be able to withstand the upward air pressure resulting from being pooped by a following sea when a large volume of water suddenly enters the saloon.

Not something that the vast majority of us will ever be faced with

 

[claymore]

Au Contraire
My ageing pal Parahandy occupies the front cabin when he is sailing with me and there is a considerable amount of upward pressure exuding from his orifi most of the time

 

[mrangry]

I suppose if you feel you need screws then go for it but I am with the yacht manufactuers on this one, no screws needed as they introduce weakness in the lens.

 

[neil_s]

There were only a couple of self tappers in my frame to hold the acrylic in place while the mastic set. Not structural.

 

[KREW2]

You don't see many, if any boats new or old with the deck hatch lens's screwed in. You said the ingress was through the screw holes so that tells you they are the weak point.
Looking at the photo from the OP, I would be surprised if those screws were factory fitted. Use the right products, take your time, and it will be very strong, and as good as new. I had no problems with the two I did.

You need to use Sika 295 as it is UV resistant, and the primer, Sika 210 gives it a very strong bond to the frame.