Canvas Boat Cover Vents?

[Songololo]

The boat that I recently adopted (5.1m clinker mahogany on oak row and sailing boat) has a canvas boat cover:

http://farm4.static.flickr.com/3048/2451886474_2babda959b.jpg

She will be on freshwater swinging mooring on Lake Zug during the sailing season and stored under cover during the winter months.

With a view to improving the air circulation beneath the cover so as to keep mould and rot at bay (see previous post Keeping Rot at bay on a freshwater mooring (http://www.woodenboat.com/forum/showthread.php?t=78267)), I was considering having hooded vents installed in the cover. The current plan is to have one approximately 0.5m in front of the mast (red bucket's position) and the other just below the aft end of the boom. This would then potentially give a nice 'through draft' as the bow would always be pointing into the wind.

Will this work? Do I need to consider vents port and starboard? Any other ideas?

[Ian McColgin]

Obviously the winter cover cannot be used on a mooring.

A simple boom tent will do the job. Make it wrap on the mast like a sail cover with a verticle front zipper to the partners, or perhaps a slightly sloped V shape pulled towards the deck cleat.

The front sides get pulled to the shrouds. Some people fit the tent to the combing, with little hooks low and outboard to recieve the cover ties. Alternativly you might pull the cover to the rails. Either way you want an easy way to loosen and secure the aft end of the cover for egress and exit from the dink or launch.

I find the normal hooks on a combing a real pain as they snag lines, even though the jib sheets should be way too large. Careful location matters.

With the back open, you'll have good air flow but you may want a vent on the foredeck, funnel pointed aft and deck plate for when sailing.

G'luck

[Songololo]

My understanding is that this boat cover is to be used on a mooring, kept in place by the boom whose aft end is supported by an A frame cradle (correct term?).

It has reinforced collared holes for the mast (the red bucket is covering it at the moment), mooring lines and stays, a cutout at the transom for the motor (motor not shown in above image) and an extension for the rudder/tiller. Access is via a zipped seam on the port side of the mast - not visible in the above image.

Is this correct?

[ChrisBen]

I'm sure you can find a local distributer for the vents but here are the type of vents you would use. Scroll down to vents.
Marine Hardware Boat Fittings (http://www.glfi.com/marinecatalog_hardwarepage.htm)
Fiberglass mesh can be sewn on the underside of the vent. One at bow and stern should be enough as the boat will swing into the wind while on the mooring.

[Ian McColgin]

It's hard to be sure from the picture, but the ridgepole looks about the right height for a boom. At that level, this cover will be trailing in the water and will get nasty fast. It's way too big for taking on and off a boat at a mooring and too clunky to be rolled up and stowed under the deck while you sail.

Make a nice little boom tent that convers just the cockpit and maybe part of the washdecks. That will be small enough that you can get aboard, stow it, and get sailing with a reasonably small effort.

This that you have is a lovely winter/on the trailor cover but is utterly unsuited to in-water use.

[Todd Bradshaw]

I've even gotten away from involving the boom in the process on the last few I've built for myself (less chafe and fewer moving parts involved). I use a single-point attachment using the main halyard to peak it up and tension the cover along with hooded mesh vents and a day/nite solar vent built for canvas work if I really think I need more airflow.

http://webpages.charter.net/tbradshaw/nordica%202%20copy.jpg

[Songololo]

She is an open boat and so requires a full length cover. Here the boat is shown rigged on the water (picture not taken by me) with what appears to be the sails, probably covering the wooden boom and gaff which are lying across the sternsheets, thwart and fore deck(?).

http://farm3.static.flickr.com/2370/2400961279_14805458bc.jpg


Todd, do day/night solar vents have an automatic mode or do they need to be manually turned on/off? Do you have a pic or link to a good example of a hooded vent? Where would you place them for this boat?

Ian, the sides of the cover do come very close to the waterline amidships; towards the bow they are way above the waterline. If they are too close to the water, I shall either have them trimmed back or somehow fold and secure the excess to an acceptable height above the water. This is what the bow looks like with the cover:

http://farm3.static.flickr.com/2167/2452171497_cfdc573b53.jpg

[Songololo]

Kaa, your post seems to have gone AWOL...

[Kaa]

Kaa, your post seems to have gone AWOL...

Yeah, it was a stupid post about cockpits and your boat is open, so I deleted it :-)

Kaa

[John B]

I don't quite understand why the stern would be into the wind? Is that right?

Something to remember about venting a boat is that( counter intuitively) the circulation is normally stern to fore in direction. Assuming its bow is to wind that is .
So I would be looking at opening(s) right on the back of the cover and hooded scoops facing to the stern ( venturis) port and stbd near the front. That way most rain doesn't get in and you get the circulation you need.

[Songololo]

JohnB, thanks for pointing that 'typo' out. My original post has been corrected.

I assume that the openings of stern hoods face down towards the water. Do you have an example picture of or link to this type of setup? Size of vents for a boat of 5m length and 1.75m beam?

[John B]

Sorry I don't. I just know that the trick to getting ventilation flow through a keel boat is to get openings aft sorted.
Examples. Iorangi found that opening a lazarette hatch aft gets circulation through the cabin on a hot night. Same with our boat Waione and adding a ventilator right back on the counter keeps that area sweet. On Riada we have have an inside door into a 'lost space' in the stern. Opening that is critical( again on a humid night ,no or little wind) to getting sleep.;)
So I think the same rules apply here, and of course part of the reason for the cover I assume is to keep rain out.

[Todd Bradshaw]

The Nico vents are expensive, not overly sturdy and rather plastic looking, but they work pretty well. They have a battery and a solar cell that recharges it, which keeps them running automatically most of the time if you get a reasonable amount of sunshine. They make one specifically to fit a flange that you attach over a hole cut into to a boat cover, but they are fairly difficult to find. It's the same vent as this one, only it snaps into the special canvas deck plate.

http://us.binnacle.com/product_info.php?cPath=199_224&products_id=1608

For vents, I usually cut a triangular hole in a vertical or steeply-sloped part of the cover, "screen" it with woven mesh to keep bugs out and make it hold it's shape, and then cover it with an oversized flap. Inside the bottom edge of the flap, I sew a small chunk of plastic flexible rod (1/8" diameter - looks like really heavy weed-eater line). This makes the flap stand proud like a hood over the hole. If it's a boom-tent-like cover, I usually stick them on the aft end and up high, though you could probably put them elsewhere if the hood flap is well designed to block oncoming rain.

The North Face used to mix light and dark colored fabrics in some of their tent bodies and rainflys, claiming that the fact that the two colors heated up differently in the sun promoted air movement and ventillation. I've always wondered whether there is enough truth to this to be worth trying it on a boat cover, but have never tried it to see if it would make any difference.

[Ian McColgin]

OK - No foredeck and a small boat. The cover makes sense except it's not at all clear as to what keeps the sides down when the boat's off the trailor and in the water - and what a pain it is to deploy and remove the cover.

I've lived with a lot of open boats and unless I were leaving the boat for weeks in a rainforest, I think I'd not bother much. I'd not have an outboard for this boat but if you must have one, take it in and out with you as that's much less work than any full boat cover. Other than the motor, nothing much to bother even in the incredibly unlikely event the boat swamps.

The more you sail, the less you'll really need the cover and the more you use the cover, with all that work, the less you'll sail. Get a good pump and enjoy the boat.

G'luck