Another question about vent installation, curved cabin top

[josrulz]

Hi all,
I know there's been discussion on this before, but so far I haven't found the search terms that are locating an answer.

As some of you may know, many earlier Sabre designs have some significant curvature to the cabin top. Our Sabre 34 Mk I is no exception.

I'm considering installing a 3" Nicro solar day/night vent in the cabintop in the head space of our S34-I, and though I haven't measured against a straight-edge yet, I'm guessing there's more curve on the deck than spec'd by Nicro as acceptable. They say you need no more than 1/2" curve over 12". The vent is about 9" across, I believe.

I'm looking for suggestions on how best to shim/frame/provide a flat surface for a vent like this. Should I use teak? Fiberglass? Starboard? Honestly, I'd like to keep this as simple as possible, but I do want to do it right and have it look good.

The position will be off center (to starboard), forward of the mast but aft of the forward hatch on the cabin top.

If there's an article I should read or another thread or something, please feel free to refer me to it.
Thanks!
-J

[JohnRPollard]

Josrulz,

If the diameter weren't so large (9" !), I might suggest something like a canted teak winch pad. But I don't see one quite that large at the link.

[josrulz]

Originally Posted by JohnRPollard

Josrulz,

If the diameter weren't so large (9" !), I might suggest something like a canted teak winch pad. But I don't see one quite that large at the link.

Yeah that would be good stuff. Although I could probably make one too, if a wood block is the best route. Not sure though.

[JohnRPollard]

Originally Posted by josrulz

Yeah that would be good stuff. Although I could probably make one too, if a wood block is the best route. Not sure though.

I've seen them in starboard, too.

Even still, this solution doesn't exactly deal with the significant camber in the deck. They are better for bringing a flat, canted surface back to level.

But I was thinking with teak you might be able to sand in some concavity on the bottom side, to match the camber.

[Faster]

These things usually 'snap into' a deck mounted ring that can be fitted with a plug if you're heading for 'green water on deck' territory. That ring won't be 9" across, probably 4 - 5"OD on the 3" cutout.

If you want it to look good you may need to build a fillet from filled epoxy or even fibre-filled resin but that's a big job once you fair it all in and finish/paint it. So in that regard JRP's suggestion of a shaped wood or Starboard piece may be best - esp if the Sabre already has wood handrails and other wood on deck that it would go with. You could laminate a teak spacer (hopefully using inexpensive scraps) then shape it accordingly.

[josrulz]

I don't have the vent yet, but I believe the reason for curvature limit on the deck is because a line could get caught under the edge of the deck and rip the whole thing off. That's why it needs to be on a close-to-flat surface all the way out to the edge of the vent. At least that's my impression.

While it would indeed be cool to have a finished frame that's fiberglass and painted or gelcoated to match the deck, I think my odds of getting it to look that good are low.

Teak would be the obvious answer and would match the boat, although I'm all for limiting the additional teak on the boat. I'm sure it would work though.

Not sure if Starboard would work since it involves the need to be mechanically fastened, plus I'm not sure if I could use a sealant with it.

Hmmm....

[svHyLyte]

Originally Posted by josrulz

Hi all,
I know there's been discussion on this before, but so far I haven't found the search terms that are locating an answer.

As some of you may know, many earlier Sabre designs have some significant curvature to the cabin top. Our Sabre 34 Mk I is no exception.

I'm considering installing a 3" Nicro solar day/night vent in the cabintop in the head space of our S34-I, and though I haven't measured against a straight-edge yet, I'm guessing there's more curve on the deck than spec'd by Nicro as acceptable. They say you need no more than 1/2" curve over 12". The vent is about 9" across, I believe.

I'm looking for suggestions on how best to shim/frame/provide a flat surface for a vent like this. Should I use teak? Fiberglass? Starboard? Honestly, I'd like to keep this as simple as possible, but I do want to do it right and have it look good.

The position will be off center (to starboard), forward of the mast but aft of the forward hatch on the cabin top.

If there's an article I should read or another thread or something, please feel free to refer me to it.
Thanks!
-J

The curveture issue has to do with the seal of the deck ring and the effectiveness of sealing that against water penetration. If the curveture is too great, build a small shallow Dorade type box out of white starboard--or pieces cut from a large white HDPE cutting board from the kitchenware department at your local hardware store--that fits the curvature of the deck that will allow you to mount the Vent on the flat top. Use a hole saw to cut an oversized hole through the deck that you can line with a piece of white PVC pipe and finish that off with a nice teak trim ring on the overhead below. With that, align your Dorade box with the opening of the PVC Pipe on deck and mount it with a a good bead of Lifecaulk. Done.

[chef2sail]

SV Lyte took the words out of my mounth...a miniture height dorade where you could sand the bow (curvature) of the deck into the upright pieces so you could glass it down well. It can be of a realtively low height so as not to catch the lines.

Check this place out as it is close to you. They sell teack in all thicknessess and have scraps also. Its just a really neat place to go and check out for a few hours. All sorts of exotic woods.

Dave

Welcome to Exotic Lumber Inc

[dhays]

Why not just cut a circular ring of Starboard or just a thick plastic cutting board? With a bit of time and a rasp and sand paper you can approximate the curvature of the deck on the underside and have a nice flat surface to afix the vent.

[josrulz]

I was just at Exotic Lumber early in the week--I love that place!

I was at the boat yesterday to check the camber for sure. Here's how it turned out...

Fore and aft, there is no camber to the cabintop. That helps.

Athwartships, there is camber that is fairly consistent over the cabintop, whether on centerline or further to starboard over the head. Just to recap, Nicro states:

When installing the Day/Night PLUS Vent on a cambered, or curved, surface, it is critical to check to make sure there is no more than 1/2" (12mm) of camber over a 12" (300mm) length of deck surface. Too much camber will distort the unit’s base plate, causing the cover to be raised off the deck.

I'm not exactly sure which way to measure. Is it option A or B (note that in my sample images the curve of the cabintop is very exaggerated--boat is much less)?

Option A:


Option B:


With option A, the middle of the 12" ruler is at the center point of where the vent will be, and the space at each end is about 5/16" or so.

With option B, the right end of the 12" ruler is flush, and the space at the left end is about 5/8". The middle of the ruler is still over the center point of where the vent will be.

I'm guessing that Nicro intended option B to be the correct way to measure, but not sure. If anyone has any input on this, let me know.

In the meantime, I'm assuming it's option B that's correct, and therefore I'll need to correct for the camber. Right now, I'm leaning towards a teak block that's square at first, so it's easier to draw the camber lines on the block. Then I can cut/shape the bottom of that block for the camber, and then cut it into a circle and finish it.

That's where I am right now, but I haven't started any of this yet...
-J