Sealing a deck hatch

[annageek]

I am fitting composite teak to the cockpit's deck in my wee tub. At the moment, there is an after market Bomar plastic hatch (600 x 300mm ish, I think) fitted to the GRP deck, which has worked OK, but given that it's taking up a relatively large deck space, it will completely spoil the look of the new teak deck (it's only a tiny deck area - 1.5sqmm in total). The Bomar hatch stands about 11mm high off the deck when mounted, so although it would be possible to over lay the teak on the lid part of the hatch, but it'll look ridiculous (I think)! I have been unable to find a suitable after market hatch that will give me a nice, flush, over-teakable surface (although suggestions are welcome), so I am looking to potentially make my own hatch arrangement.

The GRP deck section into which the hatch will fit is about 8mm. I could therefore make a marine ply frame that is epoxied and screwed to the underside of the GRP, to allow me to create a rebated area into which I can locate a suitable aftermarket hatch, such that the top of the close hatch will then be flush with the deck. This is still a bit of a bodge, though, and will probably need me to seal the AM hatch in place, and over-teak sections, meaning when it comes to replacement, it'll be makor surgery, and replacement of the compo-teak deck. If I have learned one thing about boats, is that anything that you fit to one, WILL need replacing sooner or later, and so this option is therefore a headache waiting to happen.

I am therefore looking at making a ply hatch, and ply hatch frame. The frame will be mounted as I described above. I have come up with loads of ideas for an appropriate seal, but I don't know which is going to be the best (they might all be useless). The hatch will be walked on, and while the cockpit doesn't usually get deluged with water, I'm willing to accept that it may do some point in the future. If the Solent can sink a tug, it can sink my tub! That said, a tiny bit of leakage will be OK (as it is with the current, factory installed hatch), as the lazarette below drains into the bilge.

The seal ideas are:



Also, No1 is the only one that'll have rounded corners and sealing strips that follow the radius. The others will have square corners with mitred seals.

RE: Number 4 - Sorry. Couldn't help myself

Thoughts?

 

[rafiki_]

I think number 4 is the best idea

I think you may struggle to make the hatch sufficiently rigid to make a good and consistent seal. However, a craftsman like Vas will have a much better view on this.

 

[jimmy_the_builder]

Why not fit an aftermarket hatch to the rebate created by your new undermounted ply frame so that the surface of the hatch is flush with the unteaked surface of the deck. Then fix teak to the hatch lid, as well as the deck. When selecting the hatch you don't need to be constrained by the thickness of the deck - you can set the undermount rebate at any depth you like, within reason. Use 4200 to seal the hatch frame to your ply frame, and then your hatch seal is taken care of by the aftermarket hatch.

 

[rafiki_]

Yep, I would go with that Jimmy.

 

[Greg2]

Of the four drawings I think number 2 looks best, not least becasue it appears to allow a drain around the hatch, which will be necessary. I think I follow Jimmy but would still add the comment about drainage.

 

[aquapower]

Of the four drawings I think number 2 looks best, not least becasue it appears to allow a drain around the hatch, which will be necessary. I think I follow Jimmy but would still add the comment about drainage.

No 2 looks best to me although I would aim for bigger drain, 10 will block too easily.

 

[annageek]

I take the point on the whole lack of rigidity thing. Given that the GRP deck is already quite flexy, then lots of movement is probably quite possible.

I am not sure why I discounted the rebated after market hatch as a bad idea. On balance, it's far easier, probably far cheaper, and more likely to work.

 

[jfm]

How often do you need to open the hatch? Often, eg for storage? Or only rarely when some equipment under it needs attention? If latter, then you could have a piece of ply with matching compo teak face, that drops in and is sealed with black/white silicone to match your caulk, all flush to your deck. Then you re-do the silicone "caulk" each time you have to remove the hatch panel

If you want to be able to open/ close frequently the I vote #2 because it needs to have a gutter and drain. If there is no drain it will get all greeby and the 10mm of head when it rains will make water weep thru the seal

White or black caulk? White is the new black.

 

[annageek]

How often do you need to open the hatch? Often, eg for storage? Or only rarely when some equipment under it needs attention? If latter, then you could have a piece of ply with matching compo teak face, that drops in and is sealed with black/white silicone to match your caulk, all flush to your deck. Then you re-do the silicone "caulk" each time you have to remove the hatch panel

If you want to be able to open/ close frequently the I vote #2 because it needs to have a gutter and drain. If there is no drain it will get all greeby and the 10mm of head when it rains will make water weep thru the seal

White or black caulk? White is the new black.

We used to use it all the time for fender storage but now, it's got the back end of the new fuel tank I've just fitted taking up most of the space, so they'll be going elsewhere. The thing is, there's such little storage elsewhere on the boat, we have to make the most of whatever we can get. So now, despite the small size and irregularity in shape of the space, I can still see it being a useful place to stuff other, less bulky bits and pieces. Therefore, I still think it's got to be a proper storage hatch than a semi-permanent sealed arrangement.

Gone for black caulking. White may very well be the new black, but that just means in a few years, black will be the new white again. Until then, I can just call it 'retro'! In either case, it'll look far better than the 'white non-slip gelcoat with a hint of mucky footprint' we currently have.