Dorade box enlargement...

waughoo · February 06, 2021, 09:57:18 AM

Has anyone ever over drilled the hole in the deck for the dorade boxes? The new ones that I bought to replace my broken ones are notably larger in vented airspace and I'd like to take advantage of that as well as making the vent screw easier to manipulate. My concern is what is the deck built of at that location. If it is just plywood there, i should be just fine. If it is hollow and they installed a tube, I might elect to leave the hole well enough alone.

Stu Jackson · February 06, 2021, 10:21:47 AM

Tech Notes: https://c34.org/mainsheet/pdf/Aug_2005.pdf

The "box" is hollow. You can enlarge the top of the box hole. But down below, from the cabintop level above (the base of the box) and down into the headliner below, is a solid circle of fiberglass.

I wouldn't try to enlarge the hole all the way through.

And if your vent screws are giving you grief, read the tech note first before you replace anything.

KWKloeber · February 06, 2021, 10:49:32 AM

Alex

The deck and the liner are laid up separately (two different molds) then sandwiched together. So theoretically the deck is solid outside the tube (unless it's not and there's voids). See
https://c34.org/bbs/index.php/topic,10332.msg79893.html#msg79893

waughoo · February 06, 2021, 11:59:02 AM

Thanks both of you. I will likely enlarge the hole some but perhaps not all the way. The hole in my cabin top is between sizes such that the one below is too small to be screwed over the hole in my deck and the one above is notably larger.

The dorades i went with are the vetus TBox and Chinook rotateable cowls.

Noah · February 06, 2021, 12:31:55 PM

Lot to find in search. The glassed in thick fiberglass tube that goes through the deck dictates the size of the hole. Cant enlarge that. I changed mine vents to a brand called Air-Only and added a teak ring to fit outside flange for those. I originally had 3-inch OEM Nicro/Fico plastic dorades that were cracked and not replaceable, so I opted for these—which work well.

waughoo · February 06, 2021, 01:19:23 PM

So it sounds like the raised section at deck level is hollow like the traveler riser but then the cabin ceiling is the solid bit. Do i have that right Noah?

Noah · February 06, 2021, 01:25:47 PM

Yes, sort of...(?) The tube connecting the boat's cabin ceiling to the hollow dorade box is thick solid glass. So the I.D diameter of that tube/hole through deck cannot be altered, IMO.

waughoo · February 06, 2021, 02:22:52 PM

Noah,

So i looked a little closer at the photo you posted with the dorade and mushroom vent removed. It appears as though the tube comes up from the cabin liner mold and extends into the dorade riser box on the cabin top mold. Thus, if i wanted to enlarge that, the only way would be to cut out the tube and glass in a new one. Hence the suggestion to leave it well enough alone.

Noah · February 06, 2021, 02:31:23 PM

That thin white tube you see in my pics is plastic and part of the new vent that is screwed in via a molded-in integral flange attached to ceiling from below. It inserts inside the glassed-in boat structural tube—it is not the structural glassed-in tube. I do not have any pics of the hole in the boat just bare without any plastic vent tube installed into it.

waughoo · February 06, 2021, 02:47:31 PM

Gotcha. I will have to remove my exiating vents and see if that tells me anything more. Thanks for all the responses.

Stu Jackson · February 06, 2021, 03:49:29 PM

Or you could remove just one and take a looksee.

I think you got the idea though.

In my link, the third picture with my friend holding the beer up for me, shows nothing but dark behind his hand. I think the "tubes" don't go all the way up through the hollow, but next time I'm at the boat I'll look up from the bottom. You could measure from the inside and compare that to dimensions on the outside.

Good luck.

Ron Hill · February 06, 2021, 04:43:51 PM

Guys : FYI, the 1986 thru 1988 C34s have a 4" Vetus Dorade vent, while the 1989 and subsequent C34s have a 3" Nicro Dorade vent !!

A thought

Noah · February 06, 2021, 05:15:54 PM

But, I believe the size of hole cut through the cabin top and tube/structure joining the molded pedestal, is same size on all boats. I may be wrong.

waughoo · February 06, 2021, 05:20:57 PM

I'll check it out with a little removal of one of the existing dorade boxes. The ones i have appear to be the 3" nicro style.

Kyle Ewing · February 07, 2021, 03:48:38 AM

Regarding dorade vent hole and solar vent size, the hole on my 1990 (#1010) was 4" diameter at deck and 3 3/4" in the cabin. I used Marinco 3" vents which require a 3 3/4" inch hole. I bring this up because intuitively I thought "4 inch hole, must be 4 inch vent" but thankfully double checked specs before ordering.