A cheap and easy hatch

Once again we offer you a picture of a concept you should pick up on pretty quickly. We assume that you will work out how to assemble the components just by looking at the picture.
On a boat like a Navigator you need a lot of inspections hatches. Even the small ones don't come cheap and let's face it they don't look all that traditional.
This easy hatch concept is one that has been around on sea kayaks for decades. Properly done they leak very little even when subject to constant wave action and submergence in the waves.
An inboard location in a dinghy should give you 100% efficiency.

The hatch consists of two plywood rings. The bottom ring fastens to the deck, the second ring is the 'flange' and is larger by the amount of lip you want to have. The lid is the same size as the flange. The usefulness of the apparatus will be effected by the thickness of the ply you use and it is acceptable that you use a number of thinner plys to make up the layers.
It also figures that you if you are using multiple plys for each 'ring' you can make the rings in segments and thus be able to manufacture your hatch fitting from smaller pieces of scrap.

THERE HAS BEEN SOME CONFUSION OVER THE YEARS WITH THE DRAWING I CREATED.

START AT THE BOTTOM..... That's a ring as thick as the neopreen cover and bungee cord combined. The inside of the flange as it were.
On top to that a wider ring with sufficient overlap to create the top of the flange. Note that the inside of the bottom ring and this one is the same.
On top of that the reinforcement for the hatch. That is about the same as the flange ring, perhaps a mm or two smaller.
Over the lid and fitted into the flange is a neoprene cover. Actually you can use plastic sheet or tent fabric held in place with a bungee
loop. If you do that make sure the piece of plastic sheet is wide enough so that a reasonable amount of it comes out from under the bungee.
Over that you can if you wish put a plywood or fibreglass hatch secured down by web straps. I would only do that if I was going on a serious trip.
Some folks have a flange into which this hatch sits so as to prevent water being forced under the lid. But I mean you could always just stay home.

The concept lends itself to horizontal hatches too, particularly the hatch in the No2 bulkhead on a Navigator or Pathfinder.

For optimum efficiency work out what sizes you are going to need. The 'hole' from one size of port can make the reinforcing cover for another smaller one.
Having done that you use scrap ply to make the bottom spacer ring which glues over the hole and is about 7mm high. On top of that you glue your top ring which finishes off the flange. By creating the spacer and flange in segments with the joins staggered you can make these on a very low budget. Clean up all the edges and smooth and bevel around the hole. Do the same with the lid.
Next take a piece of wetsuit rubber and stretch it over the hole WRONG SIDE UP and use a piece of shock cord wrapped in 'Gladwrap' to hold it into the flange. Trim the excess off so you have enough to fold back over onto the hatch. Use a contact adhesive (shoo goo for fixing worn running shoe soles is good) and tack down the overlap. You can put a few dressmakers pins in too to hold it in place.Run a seam around the join on a sewing machine. Make sure the shock cord is not jammed up tight by the fold. Now turn your cover right side out and fit it over the flange. The lid goes on first boys and girls. You should be able to tighten or loosen your shock cord to suit. Tie it off. Incidentally the shock cord does not have to be too powerful to do the job properly. Fitted either horizontal or vertical the hatch will really work and will last for years. You may have to make a new rubber cover but I doubt it.
If you really want to beef up the protection make a lid for your hatch assembly and haul it down with a couple of webbing straps. If you are suffering a bit of paranoia put a rubber seal around the bottom of your lid.
You could do some really fancy woodwork on your hatch cover and even make a circular one with fancy brass fittings for a fraction of the cost of a screw in job.
Big oval hatches are a breeze with this system and you can make very big rectangular hatches too providing you get the right radius on the corners so that the rubber cover retains a good bearing surface.
Just one more tip. If this is just an inspection port to be left off to ventilate the boat when you are on the hard you can use a square of rubber backed rip stop (as in tents) with a shock cord loop. That arrangement is just as efficient and with a cover like a plastic picnic plate or very shallow round dish you could knock up a hundred or so a day? You know what I mean.

Dave