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Hatch Closure design etc.
By:Ken Katz
Date: 7/15/1999, 2:07 am
In Response To: Re: Outer Island Photos (mike allen)

I reduced the volume of Jay's latest version of the Outer Island by taking his drawings of the station forms and bow and stern forms and reducing them in a copy machine by 2%. The spacing between the forms remained the same (12"). The changes to the cockpit were made because I prefer a keyhole cockpit design over the smaller one that Jay uses. I like the easier entry and exit.The shape of the cockpit as well as the retractable skeg design is "borrowed" from a Pintail or Romany.

I will do my be my best to describe my hatch closure design. I will take some photos and post them when I get a chance. The basic idea is that a handle above deck is used to spin a crosspiece below deck. The crosspiece rides on 2 opposing wedges. As the handle turns the wedges pull the cross piece down which exerts a downward pressure on the hatch. It works great!! I started with standard flush hatch design with a under deck lip to support the hatch and used a closed cell foam gasket. The hatch and a few inches around it were beefed up with a extra layer of glass in and out and a piece of 1/4" X 3/4" strip epoxied along the centerline of the hatch (inside). This give extra stiffness as well as more bearing surface for the shaft of the handle that passes through the hatch. I made a wooden handle with a 1/4" stainless steel bolt mounted in it by taking 2 pieces of hardwood about 1/4" x 3/4" x 4" and drilling a 1/4" hole in one in the center and a larger hole part of the way through the inside of both pieces. The larger hole should be large and deep enough so that when the 2 pieces are glued together with the bolt passing through the one with the 1/4" hole, the 2 strips will meet and the head of the bolt will be captive inside. Thickened epoxy is used to fill the gap around the head of the bolt. This leaves you with a handle or knob that can be carved to any shape you want with a threaded shaft that should not spin independant of the wood. The next step is to make two tapered "ramps" or wedges about 4 inches long. They should start about 1/8" thick and wind up about 1/2" thick . They are epoxied on the underside of the hatch lip 180 degrees apart. Before final epoxying,I used hot glue to experiment with their location and dimensions. I made a cross piece out of fiberglass batten stock (from a sailboat sail) and glued a short doubler piece in the center to give enough thickness for a "T nut" to be glued. A piece of wood would also work as a cross piece but I like the strength and spring that is inherent in the fiberglass. Drill a hole in the center of hatch cover for the threaded shaft to pass through with a washer and nylock nut on the inside. You can set the "drag" on the handle to whatever amount of friction feels right by tightening the nylock nut. The cross piece is cut to a length which allows it to ride on the ramps when threaded on the shaft of the handle. A nut above and below the cross piece is tightened against it to prevent it from turning on the shaft once you adjust the pressure (distance from the inside of the hatch cover) you want to have holding the hatch down. Be careful, the wedge shape of the ramp will permit you to use more pressure than is necessary to keep the hatch leak free. I over stressed the fiberglass around my hatch by adjusting it to tight. A piece of inner tube will work as a gasket where the handle shaft passes through the hatch cover. I also made a bushing out of copper tubing where the shaft goes through the cover to prevent the threads from wearing the hole larger. When it is complete, you can easily open and close the hatch with a 1/4 turn when your hands are cold and stiff. I added a short piece of line leading from a hole near one end of the handle and tied it with a rolling hitch (adjustable) to a loop for my deck line as insurance against the handle turning is rough weather. With the drag on the handle set snug, the line is unnecessary but adds piece of mind as well as keeping the hatch from gettning lost. I also incorporated a stop at the end of the ramps to prevent turning the handle to far and having the cross piece spin past the ramp.

I hope this description makes sense. If anybody wants more info, let me know.

Ken

Messages In This Thread

Outer Island Photos
Ken Katz -- 7/13/1999, 1:08 am
Re: Outer Island Photos
mike allen -- 7/14/1999, 2:53 pm
Hatch Closure design etc.
Ken Katz -- 7/15/1999, 2:07 am
Re: Outer Island Photos
Shawn Baker -- 7/14/1999, 12:39 pm
fixed your links
Brian T. Cunningham -- 7/13/1999, 10:14 pm
Re: Outer Island Photos
Lennart Berlin -- 7/13/1999, 6:12 pm
Re: Outer Island Photos
Ken Katz -- 7/13/1999, 1:18 am
Re: Outer Island Photos
Frank -- 7/13/1999, 8:21 am