Installing a Bronze Mushroom Vent

[John Stone]

When I rebuilt the Far Reach I installed vents on the fantail to improve air flow in the lazarette. One of the vents was a simple Nicro 3" low profile cowl vent I mounted it to a teak pad on the deck. I never liked it. But, it was all the budget would suport at the time. My wife made a small canvas cover to put over the vent to keep out rain water. But, as is typical with plastic hardware it just did not last. It was cracking from the sun. I also begin to find small amounts of water in the bilge and traced it to the leaking vent. It needed to be replaced with a more quality vent.

I thought briefly about installing a nicro solar vent and looked at one at the local chandlery. It seemed to be even less well made than I expected. I heard from a fellow Cape Dorian they did not have a long life span. Over the years I had seen bronze mushroom vents. They can be open and closed with an internal crank and if well made will last longer the life of the boat. Davy and Company probably makes the best mushroom vent available so I contact R&W Rope, the US Distributor for Davy. They ordered me a high profile 3" model. It arrived a couple days ago. Beautiful. It is very well made. I took it down to the boat and it was a drop in fit. All I need now is to procure a few #10 bronze oval head fasteners, and install it with some teak colored polysulfied and we are done. I think it looks like it was made for a Cape Dory. I have one more plastic base Nicro vent to replace but it is sitting on top of a dorade box. It will require a cowl vent rather than a mushroom vent.

[Jim Walsh]

Great looking vent. A proper vent for a proper yacht.

[JD-MDR]

Hi John, I'm clearing out my Lazerette getting ready for autopilot. I rerouted the vent ducts for the blower and the other is the same cowl vent that you replaced with the mushroom type. I had those mushroom ones on a previous boat. I liked the way you can close them when in rough seas. but when I was below I sure felt a lot of air coming in thru my existing cowls .
do you think the mushroom are as good?

[John Stone]

Hi John, I'm clearing out my Lazerette getting ready for autopilot. I rerouted the vent ducts for the blower and the other is the same cowl vent that you replaced with the mushroom type. I had those mushroom ones on a previous boat. I liked the way you can close them when in rough seas. but when I was below I sure felt a lot of air coming in thru my existing cowls .
do you think the mushroom are as good?

Yes and no. Don’t you love an answer like that?! It depends on what you need and what is the situation. For example—a cowl vent works fine if it’s facing the wind. If it’s not facing the wind then not so much. I don’t know what the exhaust flow characteristics are when the cowl is facing away. Probably pretty low. If an engine or something requires a certain volumn of air to be effective then the only way to achieve that is which a fan. Since there is no fan on your cowl I don’t see how it provides any more air than a mushroom vent.

And a cowl without a dorade box is going to let water in the boat at some point. On the FR we have three cowls and all are integrated into dorades. The mushroom vent is a better solution for us than a cowl without a dorade—I did not want to sacrifice the deck space required for a fourth dorade box and I wanted to be able to quickly close the vent so the mushroom was a good solution.

I like cowls. I like being able to aim them into the wind. But when a dorade box is not feasible or desirable I can’t think of a better solution than the mushroom vent. Perhaps a small hatch can work but it comes with it’s own set of problems.

Anyway, in the end you just have to ask yourself what solutions best meet your needs for the cost it takes to purchase, install, use, and maintain them.

[hilbert]

FWIW, the stern cowls were glassed over on the FeNIX (a CD28) when it circumnavigated.
As such the boat was more seaworthy and it is doubtful that this modification accelerated the aging of mechanical components.

[John Stone]

FWIW, the stern cowls were glassed over on the FeNIX (a CD28) when it circumnavigated.
As such the boat was more seaworthy and it is doubtful that this modification accelerated the aging of mechanical components.

Hilbert, are you saying Fred glassed over the “cowls” on Finex or the holes they ventilated through? The engine needs access to clean air and a way to exhaust heat and whatever else might escape from the internal combustion that does not get expelled via the water exhaust.

[hilbert]

The cowls were discarded and the holes were filled in and glassed over.
I speculate that a small diesel can suck in sufficient air from the cabin (via the bilge and other holes in the bulkhead), which also acts to cool the compartment.
Whatever escapes the internal combustion and does not get expelled via the water exhaust, will either remain in the compartment (slight vacuum) or eventually get sucked back into the engine.

Here are pictures of the stern of the FeNIX:

[John Stone]

Hilbert,
Right. I don’t know what ABYC recommends. Would be interesting to know.

I’d like positive ventilation out of the compartment with an inboard as I think it’s safer. I don’t have an engine but I chose to further improve ventilation via the fantail as a tool to help promote the flow of air through the boat. It also helps prevent mildew especially in the lockers and lazarette.

My main cabin is not sealed from the lockers. I have large ventilation holes in the after bulkheads to carry air from the saloon into he lockers and out the fantail cowl and mushroom. Definitely keeps the boat better ventilated especially when it’s closed up due to foul weather.

In the end it’s a choice.

[JD-MDR]

.,Don't the mushroom vents close easily just by turning the head? It would be too much for me to go under to close them as I don't have a hatch I'm looking for cowl vents that unscrew and have a cap that can be screwed in to seal. I think they make those......Oh I found them at Defender. Looks the same as I have. Comes with a snap in deck plate. Any comments????

[John Stone]

JD, the mushroom vent I have has a knob on the inside but I spin them open and shut from the outside. The head closes against gasket...watertight. The knob is designed to allow you to opens it from the inside of the boat if it is installed in the cabin top.

A cowl without a dorade will let water in the boat when it rains. We made a cover for ours and it worked fine that way but had to be covered in the rain. The mushroom vent I have has a 2-3” spigot and a high dome so it can be left open in a pretty good rain...or I spin them down till there is a very small gap. Air can still flow though.

Replacing the cowl with a deck plate is a pain and you’re probably only going to do it when you are offshore. But that’s a nice time to get air flow. The best solution is a dorade, no doubt about it. The mushroom vent is something less but much better in my opinion than a cowl without a dorade box.

[Dave and Kathy]

John, All your projects turn out beautifully and the Davy vents look great! I bought the same vinyl vents for Grayce Avery, but they looked horrible after only one season. We found these bronze vents being manufactured by Port Townsend Foundry, here in the Northwest. They are drop in replacements for the vinyl vents. Like the Davy vents they have a handwheel underneath and an o-ring to seal when closed. I liked that they are flush when closed and can be ‘aimed’ when open. Personal choice...

[John Stone]

Dave and Kathy

Beautiful. Pete makes great hardware. I have never had a bad experience with PTF.

[Jim Walsh]

John, All your projects turn out beautifully and the Davy vents look great! I bought the same vinyl vents for Grayce Avery, but they looked horrible after only one season. We found these bronze vents being manufactured by Port Townsend Foundry, here in the Northwest. They are drop in replacements for the vinyl vents. Like the Davy vents they have a handwheel underneath and an o-ring to seal when closed. I liked that they are flush when closed and can be ‘aimed’ when open. Personal choice...

Those look great. Never knew an articulated style was available.

[Dave and Kathy]

They are called "3" articulating mushroom vents" on the Port Townsend Foundry web catalog.