Installing Cowl/Dorades

[blahman]

Hi all,

I plan to install four dorade boxes with 4" (tube area) cowl vents. I'm curious what the best route is for boring 4" holes in my cabin top. It is a plywood cored fiberglass cabin with fir headliner lamintated to the cabintop.

I appreciate all input!

Fair leads,
Aaron N.

Some random thoughts for your project:

It is by far best to use a hole saw insead of a saber saw.

Start cutting from inside so you don't splinter the wood headliner. Once the pilot bit penetrates the deck, take the drill outside and use the pilot hole to finish the 4" hole from the outside. This will give you nice clean holes inside and out.

After you have the hole cut out, rout out the deck coring for 1/2 to 1 inch back from the edge of the hole. With a plywood cored deck I'd probably use a dremel tool to do this, but good sharp chisels would work if you are careful. Replace the plywood removed with highly thickened epoxy. This will keep water from contaminating your core and causing you no end of trouble.

I think those are the key points. Somebody else might have something to add...

[GordMay]

For larger holes, use a Hole Saw (I prefer Carbide-Tipped) or Adjustable Beam Circle Cutter.

[Pericles]

GordMay,

The correct method A seems counterintuitive, so thanks for posting that. Who is the manufacturer please?

Pericles

[GordMay]

The recommended method A seems counterintuitive, to me as well.
“A” Correct: Blades cut inside and outside
“B” Wrong: Blades cut only inside
“C” Wrong: Blades cut only outside
Goto:
Circle cutter 30 - 300 mm

Most beam & gouge circle/hole cutters only have a single tool.

[blahman]

Gord,

You're knowledge seems endless!

The circle cutter seems like it may not have enough depth to go through, though I imagine there are different types.

I had assumed a hole saw would be the way to go, but figured it's worth asking to be sure. I'd rather feel stupid than be stupid.

Thanks for your help!
Aaron N.

[Pericles]

GordMay,

Thanks for the Dieter Schmid details. They have some interesting jack planes in their ranges.

Pericles