Temp closing off thru-deck chimney hole

[MC1]

Your thoughts on this solution please . . .

I'm installing a Newport Dickinson bulkhead propane heater. The chimney requires a 3" hole in the deck. The vendor offers a SS weather guard to cover the chimney deck cap when it's not being used to help protect against moderately bad weather. Nevertheless, in case of really rough going at sea, I'd like to be able to temporarily remove the deck cap altogether and seal the 3" hole in the deck. I'd like to prevent water intrusion, even in the extreme circumstance that the boat were capsized.

Therefore, my solution is . . .
1. Instead of mounting the deck cap directly to the boat as suggested by the vendor, I'll permanently mount a teak ring on the deck around the hole. Four bolts will stick up through this, evenly space around the ring.
2. I'll mount the deck cap to a second teak ring of the same diameter, and both the deck cap and the teak ring it is mounted to will have holes that accept the bolts coming up from the teak ring mounted permanently to the boat. After placing the deck cap and its mounting ring onto the boat's teak ring, I'll secure the deck cap with cap nuts over these bolts.
3. I'll have a 3rd teak cover plate made of the same diameter as the previous teak rings, but in this case with no 3" hole in the middle. This teak cover plate will also have holes that accept the bolts coming up from the teak ring mounted to the boat.

Now, in really rough conditions, I'll have the option to remove the deck cap, and replace it with the teak cover plate. Of course inside the boat, I will also have to temporarily remove the flue pipe between the stove and the deck cap.

The other option I could think of was to fabricate a heftier water-tight cover to place over the deck cap and allow it to be secured to the deck in some way. The down-side of this approach is that it may be a little large / tall, so it'd be more vulnerable to green-water over the deck.

Any thoughts on these solutions or other better ideas? I realize I'm being a little paranoid here, but the boat is a Bluewater design (PSC 34) and I'd like to keep it as water-tight as possible.

[tager]

Why not get a deck iron and a rubber plug?

[sailingdog]

That's not a bad way to do it... but how hot is the exhaust gas from the chimney. If it is too hot, the teak would be at risk...

[MC1]

If I understand the suggestion correctly . . . Instead of installing the deck cap permanently to the deck using screws as the manufacturer proposes, I could install bolts into the deck around the 3" hole, then place the deck cap over those bolts and secure it with cap nuts. To seal the hole, I could swap the heater's deck cap with a cover plate / rubber plug, and omit the use of teak altogether.

This is a simpler and cheaper approach, thank you. The teak might look a little nicer, but it's a maintenance item (since I'd keep it varnished). Teak varnish may also be affected by the heat from the chimney. I'd have to be careful each time I swapped the deck cap for the plate and back, to get a good seal. This is also true with the teak ring approach, but mitigated a little by having the first teak ring permanently installed, using 3M 101 or similar between it and the deck. The chimney's cap is then up off the deck a little, which helps prevent water running down the hole if I don't get the seal exactly right when using the cap.

[sailingdog]

Or, you could get a larger metal deck ring and deck plate, with a spare plate, and install the deck cap into one of the deck plates, and use the other as a cap for the opening in heavy weather.

[MC1]

Originally Posted by sailingdog

Or, you could get a larger metal deck ring and deck plate, with a spare plate, and install the deck cap into one of the deck plates, and use the other as a cap for the opening in heavy weather.

Yes, I've been thinking about this approach as well, but I couldn't see a way of doing it without requiring a hole larger than the 3" one already required.

Regarding the concern about the exhaust temp. and teak . . . yes, this could be a problem, I'll have to research this further. If so, I'm not thrilled about even subjecting the boat's gel coat to high temps. The deck cap is as in the attached pic, which draws air in from the lower part and exhausts it out from the upper part. The lower air inflow should provide some protective benefit from the exhaust temps exiting the upper part (which also gets deflected upward a little).

[JohnRPollard]

Not sure exactly where you plan to mount the heater -- presumably on the forward port bulkhead in the main salon -- but depending on where the chimney exits to the deck, you may have to address the issue of deck camber.

We used a "Large Canted Teak Winch Pad" which helped to compensate for the deck camber. Otherwise, the chimney cap and shield hardware would be mounting to the deck at an angle very askew from the vertically plumb chimney.

There really is little concern about exposing the teak to the heat from the chimney. While nominally 3", I seem to recall the chimney is actually about 2 5/8" or so in diameter. This leaves a nice gap all around when you cut a 3" hole in the deck and the winch pad.

Also, the chimney is double walled, with air from exterior coming down the outer flue. This insulates and cools the inner exhaust flue (especially up near the top, where both the exhaust and intake air are cooler), so it does not get nearly as hot as a single-walled chimney.

As for capping it off in bad weather. I think, with the standard spray guard, that you will be in good shape for all but the nastiest conditions. That said, I too would devise a fallback for off-shore.

I think your approaches above will work pretty well. Seeing as I'm congenitally lazy, I would favor an approach that would not require any disassembly. Instead, I would want a solution that merely allowed me to cover up the cap and guard without taking them off.

I think what I'd do, is tap a small threaded bolt hole into the flat metal bands at the tip top of the cap guard. I would then permanently secure (epoxy?) a large nut on the underside of that hole. Then I'd hunt around and find a stainless steel kitchen bowl that was sized such that it could be placed over the entire cap assembly like a dome. I'd drill a similar size hole in the center of the bottom of that bowl. Then I'd get a bolt and secure the bowl to the cap guard, through the pre-drilled holes.

I would probably gasket it a bit too. A small rubber gasket at the bowl bolt. Then, probably a donut shaped gasket that would fit over/around the cap and guard assembly, lay on deck (or better yet the winch pad --that camber issue), against which the stainless bowl would snug.

Anyway, all this in theory -- I haven't attempted it. Hopefully that made some sense and you could follow what I was getting at.

I still don't have a good photo of it, but you can see our cap, with shield, mounted to the winch pad in this photo:



You can see that the canted winch pad did not alleviate all the camber, but it made it do-able.

[christyleigh]

I'd second the dog about using metal instead of teak for sealing up the hole. A teak bolted on teak ring, another piece of teak bolted down to seal it...... Ooops.... it cracked at the grain. Gives me the willies just thinking about it. Unless the surface is perfectly flat I think even a cheap piece of plywood would outlast teak. I love teak and its strong stuff ...... but grained wood to seal a rounded surface..... not for me. I installed the your heater on my last boat by the way, and I wouldn't worry too much about the heat....... but there is another strike against wood..... warm - cold - wet - dry - over and over again...... crack

[MC1]

Thanks John, I was hoping you'd weigh in with your thoughts as well. I appreciate the reassurance regarding the exhaust temps, and your descriptions are clear. I will have some camber to deal with, so that's another advantage of using a teak base, similar to your winch pad approach. BTW, if I recall, you mentioned previously that you built a bulkhead to mount your heater on for your PSC 31, and if I recall the related pic you posted . . . a very nice bit of craftsmanship, that.

Regarding the approach of using an inverted SS bowl . . . since I still haven't mounted the deck cap yet, I have it here in hand and observe that the SS pipe isn't the strongest. Since I'm being paranoid here to begin with, a concern would be that green water over the boat might easily just tear the whole thing off the boat, as your bowl would be dependant on the (not overly strong) cap itself as a mount point.

Perhaps a hybrid approach of a couple of the above suggestions? . . .

1. Install a deck plate with a larger hole into a winchpad (but keep the thru-deck hole at 3")
2. Permanently mount the winchpad to the boat
3. Cut a 3" hole in the metal deck plate cover and install the heater's deck cap into that
4. Have secondary deck plate cover on hand to use when the going gets rough
5. Use inverted SS bowl as head-guard in case of boom mishap?

[bubb2]

If it were me, You are going to be cutting a plug out to the teak winch pad. If you make the cut with a bevel from the top down to 3 inches at the bottom which can be done by setting the angle on a saber saw. you can make a teak plug that will fit perfectly. A SS bolt and washer though the top and a piece of flat stock and wing nut on the bottom side and you can tighten it down and it won't leak or go anywhere.