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As per the instructions on page 161, I drilled 4 1/2" holes for the cabin vents. But, the only covers I can find are a maximum of 5" in diameter, with 4 5/8" between the mounting holes. That means I have only 1/16" of wood all around to drill my mounting holes into. That's not going to work.

So my plan is to fashion plywood flanges to go around the vent covers and use very short screws to attach the covers to the flanges from the inside. The flanges would match the ones around the port lights. The hitch there is that the best way to cut the flanges is with a router mounted to a circle jig, but the only ones I can find cut a minimum diameter of 10" (makes sense because of the diameter of most router bases). So what to do?

I have seen pictures where others have made similar flanges. I have a jig saw that might do the trick after rough-cutting the plywood to the approximate size. I'd have to rig some kind of centering pin. Any ideas?

Or, if someone knows where I can find a 5 1/2" or 6" vent cover, that would be an easier fix.

On the prototype it looks like the cabin vents are covered with 4 inch plastic deck plates. Those require a cutout diameter of 4.5 inches.

In my experience the 4 inch deck plates have a smaller inside diameter, not larger. The inside and outside diameter should be listed on the product packaging.

Dana: I uploaded some pictures of jigs I made for my build under the title "helpful homemade jigs" or something similar. In there, I have a circle jig that can cut from 3 inches diameter to infinity. I used it to but all the circles in my build, including the porthole flanges. To make a flange, obviously you cut a big circle, then cut a small circle out of that. A little sandpaper and it's like new.

The hole you need to cut for the 4 inch deck plate is 4.5 inches. I have them in hand. The inside diameter of the 4 inch deck plate is 4 inches, hence the name. The outside diameter (that of the flange) is 5.75 inches.

Oh I see what your saying. That makes sense.

I would really like to see your circle-cutting jigs. Also, I'm not sure if we are all on the same page. I am talking about the vent holes in bulkhead 2, inside the cabin. I don't want deck plates there, I want louvered vents. I bought two 5" butterfly vents, but the distance between mounting holes is only 1/16" more than the diameter of the holes. Trying to drill holes for mounting screws that close to the edge just does not work.

In reference to the vents on bulkhead 2, that's what I was talking about - on the prototype it looks like they used 4 inch deck plates - that's why they specified cutting 4.5 inch holes. If you want louvered vents that's another matter. Sounds like you have figured out a way to make that work. Your boat looks great, by the way.

Here's the link to the circle-cutting jig I made. viewtopic.php?f=3&t=608

I'm (unduly) proud of my design for homemade covers for the dorade vents. I installed a small flange made from 4mm plywood. Inside the hatch is a 4-inch 6mm piece of plywood, which snugs up perfectly inside the flange to close the hole. To hold this piece of plywood in place, I used a small rectangular piece of 4mm plywood with a hole drilled in the center. A line is stop-knotted to the back of the vent piece, through this rectangular piece, and then into an adjustable knot like two half hitches or something (I can't remember what I used). You can then tighten the knot, which pulls the vent and rectangular pieces tightly together and holds the vent closed. Loosen the slip knot to allow the vent assembly to drop down into the dorade box. Simple, works well, and is adaptable to any size opening.

You should be very proud, not unduly proud. That is not only ingenious it looks very pretty.

One advantage deck plates on bulkhead 2 allow is the ability to positively seal the cabin from the dorades if needed in dire conditions. The vent covers on the cabin top are only held by friction and even when closed, water can still come in through the drain holes. I'm talking about in the event of a knock down or some weird weather happening with high winds and horizontal rain, or a drain hole freezes shut with ice on the deck, etc. - life and death kind of things. Lake Superior has the occasional sudden June snow storm.

Less dire - similar things could happen with the boat on a mooring or tied in a slip or even on the trailer with the owner far away.

"Batten down the hatches" isn't just a "saying."