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[npomeroy]

I'm working on my first scratch-built 60 cm scale tug boat. I need to be able to open the hull cavity to clear any water ingress, and for any mechanical adjustments. But considering that water on deck is highly likely, I need to provide a large water-tight hatch. The deck will be 1mm ply, with an internal framework of 3mm ply ribs. I am thinking of an opening with an overlapping frame (underneath) on which I lay a thin silicone gasket. I'd be inclined to grease the surface as well. The hatch would be be held down with a series of small screws. Alternatively I could try to mould a gasket with silicone sealant.


Any suggestions or links please?


Cheers
Nelson

[Akira]

Nelson, You are on the right track with your ideas. I have seen all that you suggest used successfully, some of them in submarine. creating a silicon gasket, while the hatch is held down with blind holed screws(machine screws) works really well.
Another few possibilities, o-rings, . route a track in the hatch edge and silicon an o-ring into place. It requires bulk o-ring material, cut to length and glue together.Silicon foam tape. ie weatherstripping tape.Hopefull more folks will come up with suggestions.

[Mark T]

Hi Nelson


Your idea will work - here's a couple of pictures of how I did exactly what you want to do.  A channel in the hold which is filled with a thin batten and finally bolted down.


I hope these help











Mark

[tonyH]

You can also use small neodymium magnets instead of the screws. Easily gettable on line, down to 3mm diameter or so, from the usual sources. I've normally set them into holes around the aperture so they're flush and small cuttings of thin tinplate stuck on the underside of the "lid" to suit.    

[roycv]

Hi for a non flush deck cover I make a coaming in the deck and the hatch is made over it.  I find that when the coaming is done cover the whole with some cling film and build hatch to fit.  The cling film stops glue adhering and also gives a firm fit for the hatch when removed.
Regards
Rpy

[RichM]

Neoprene Tape is also very good as well.

[npomeroy]

Thanks for all the comments. I like the idea of magnets: I use them on aircraft hatches and helicopter canopies. The combined force can be high so the hatch needs to be strong to not be broken when lifting. The attractive feature is that the deck can be flush and free of screw heads. I'd be inclined to place the magnets inside the hull so their thickness and attachment would not be limited by hatch thickness. It also may be an invisible way to attach the superstructure/cabin, which if removable allows more hull access. With motors, bow thruster and maybe pump, I'll probably want maximum access for troubleshooting.


Cheers
Nelson

[Geoff]

Another alternative is to coat the lip/edge with Vaseline and wipe away any surplus. This works well especially for a semi-fixed hatch.


Cheers


Geoff