Installing a deck hatch

[coopec43]

I have had a leaking deck hatch over the aft cabin.


I've taken it out and am about to re-install it. I've measured the hatch diagonally two ways and it is exactly square. The deck is also exactly flat.


I have Sikaflex as well as butyl tape. When I installed the hatch initially I used Sikaflex but this time I'll use butyl tape.


Should I tighten up the bolts fairly firmly straight away? I suppose I should squeeze sikaflex into the bolt holes to stop leaking down the threads?


Thanks in advance

[tkeithlu]

Put the hatch in place, then wait until the goo has set, then torque it. That way you get a compression gasket made of goo rather than simply a seal.

[Nord Sal]

There's no need to wait for the "goo to set" if you're using Butyl Tape.

[coopec43]

Originally Posted by tkeithlu

Put the hatch in place, then wait until the goo has set, then torque it. That way you get a compression gasket made of goo rather than simply a seal.

Thank you: that's what I'll do. (I always value your advice!)

[Cpt Mark]

you could also add a small silicone rubber spacer (1/8") to the inside of your bead. That way when you do tighten down you can't squeeze all the goo out.

I'm doing 2 deck hatches today and going with butyl tape. Faster, easier, way less messy, easy to remove in the future and does a great job. If you do go butyl tape get the good stuff from MaineSail. It is light years ahead of the junk you find in the big box stores or marine chandleries.
https://shop.marinehowto.com/products

[Locquatious]

We made fiberglass rings, slightly larger than the hatch flange both inside and out and about 3/4" thick. The rings were either epoxied to the deck or caulked with UV4000 to the deck. The hatch flanges were caulked to the upper ring surface. were We have not had leaks since.

In our case we were trying to get the hatch flange above a teak deck. Before, the water that invariably sits under the teak, usually found it's way under the hatch flange.

Even if you don't have teak on top of the fiberglass deck, the rings stiffen the region under the hatch flange reducing movement and caulk stress.

[SV__Grace]

I like to use a heat gun to soften it and help it set, screw down gently and follow up a few times in the next few days to screw down further and it will seal well and last a long, long time.

[Gmcgyvr]

I suggest you run a good bead of silicone and then partially clamp it down before it sets. This will allow the silicone to seal everywhere ( no voids). Once set you should then torque as needed.
Or use butyl tape - it’s a better solution. It will stay somewhat flexible, and will continue to squeeze out over time.

[sailortype]

never ever ever EVER use silicone on fiberglass surfaces

[coopec43]

Originally Posted by Gmcgyvr

I suggest you run a good bead of silicone and then partially clamp it down before it sets. This will allow the silicone to seal everywhere ( no voids). Once set you should then torque as needed.
Or use butyl tape - it’s a better solution. It will stay somewhat flexible, and will continue to squeeze out over time.

I think when I've used Sikaflex previously I probably have had voids and if water can find a way through it will.This time I will use butyl.

I wonder whether water wicks past the rubber seal? Previously I have used Vaseline on the rubber and it seams to help.

Thanks everyone for your advice.

[George DuBose]

I have used a vinyl foam tape that is double stick on my large forehatch and 12 years later, I have never had a leak from that hatch.

Very easy and neat to work with.

[Thumbs Up]

Sikaflex is a brand not a product. When you say Sikaflex it is like saying 3M, or Permatex, it tells us nothing.

[coopec43]

Originally Posted by Thumbs Up

Sikaflex is a brand not a product. When you say Sikaflex it is like saying 3M, or Permatex, it tells us nothing.

I use Sikaflex 11FC when I just want seal something and Sikaflex 291 when I want a strong adhesive for (say) a through hull fitting.



Sikaflex 11FC sealant can be used as an elastic adhesive for assembling metal-framed structures, acoustic ceiling tiles, floor mouldings and sills, cover plates, covings, window and door frames and lightweight building materials.


And I use Sikaflex 291




Sikaflex®-291 is a multipurpose product for use in marine constructions. It is suitable for making elastic, vibration-resistant joint seals, and can also be used for a variety of interior sealing applications.


They appear almost identical. But I'd use 291 where the joint was permanent.


Maybe I better make sure I am using the right product? Thanks

[Chotu]

Originally Posted by Locquatious

We made fiberglass rings, slightly larger than the hatch flange both inside and out and about 3/4" thick. The rings were either epoxied to the deck or caulked with UV4000 to the deck. The hatch flanges were caulked to the upper ring surface. were We have not had leaks since.

In our case we were trying to get the hatch flange above a teak deck. Before, the water that invariably sits under the teak, usually found it's way under the hatch flange.

Even if you don't have teak on top of the fiberglass deck, the rings stiffen the region under the hatch flange reducing movement and caulk stress.

This is the best advice. Make that raised lip to really reduce your reliance on the seal also.

I made flush hatches for looks and regret it. The drains get clogged up all the time and then they overflow.

[SV__Grace]

Originally Posted by Thumbs Up

Sikaflex is a brand not a product. When you say Sikaflex it is like saying 3M, or Permatex, it tells us nothing.

sikaflex 291 seems best for sealing hatches and windows and bedding deck stuff. It has enough adhesive to create a durable bond yet be easier to clean and re-bed items like hatches and windows that experience a lot of flex and salt spray that will need re-bedding every 5 years or so.

295 UV is a more aggressive sealant, color fast and resistant to UV degradation, better for more permanent installations such as bedding windows into frames.

To be clear, a window can leak when the sealant fails between the window and the frame, or the frame and the cabin/deck (typically fiberglass). I use 291 for the latter, 295 for the former (on vertical surfaces... I prefer Butyl for horizontal surfaces, such as bedding a hatch to the deck).

I'm not a pro, just a long time owner of multiple 80's era boats that always need love!

Confession- I use silicone to seal stubborn leaks in areas where I won't be able to re-bed anytime soon (such as the toerail) or a window that I intend to replace. It is really, really hard to remove all traces when going back to replace or re-bed, but I've done it enough times I'm comfortable doing so, it just takes a LOT of patience (and sharp razor blades).