Never be afraid to say “I don’t know.”
On the subject of learning something new (see yesterday’s post), I have never been afraid to say “I don’t know.” Dozens of times during martial arts seminars with my coaches, when a question was posed to the group that I knew no one had the answer to, I would be the one to put up my hand and say “I don’t know.” IMO, admitting that you don’t know an answer does not mean that you are stupid. Continuing to go on without learning the answer when the information is available does!
So, on that note, here is a boat thing that I only recently learned about: dorade boxes. While I’ve, of course, seen them on countless boats, I’ve never sailed on a vessel that had them installed. I recently read an article that said something to the effect that all real bluewater boats had dorade boxes, which is why I even bothered to look them up.
Note: I saw a Facebook status message that said something to the effect that, when you ask me a question about who someone is, or how something works, I’m going to assume that Google is broken. Funny, but true. The answers are only an internet search away. Don’t be lazy!
Anyway, fresh air in a boat is good, and if dorade boxes / cowl vents allow fresh air to get inside while keeping the water out, that seems like a great thing. Unfortunately, to my knowledge, no Amels were built with such a feature.
Two thoughts:
1. I really windy conditions you are likely to get some fine mist. But still a good idea.
2. When you design the boxes, if you do, remember that the cross section area in the rising section must result in lower vertical velocity than the settling rate of the finest mist you wish to eliminate. Put another way, if the apparent wind is 40 knots and the mist would be suspended by a 10 knot upwards breeze, the cross section in the riser must be at least 40x(area inlet)/10, but probably double that. Other wise you get entrainment. In other words, the boxes need to be more like the photo (big) and less like the line drawing (tiny).
This is a common problem in distillation design.
And needless to say, they need to be closable when green water is an issue.
I would also look into how they work if turned aft. They probably still suck some air out, which may be enough sometimes, when it is cool and stormy.
I’ll give you a call if we decide to pursue this. 😉
We have 6 dorade boxes, and they are identical in size. When we set out for a passage, we always turn the forward 4 cowl vents in reverse. This is so that we don’t get a big wave inside the cowl which overwhelms the box. However, having said that – occasionally when we get boarding waves over the bow, a wave will “hydraulically overwhelm” the 4 small drain vents on the box. Yes, the water squirts in through the drain boxes and rises up over the interior lip. Therefore, we also completely block (from the inside) the two forward boxes on passage. There is still plenty of air circulation inside the boat, even though the forward 4 cowls are backwards. I suppose I’d like to see the interior lip a little higher, but to tell you the truth, with seas of 3-5 metres, the hydraulic pressure on those drain holes (and every other little orifice on the deck) will make that water squirt lots of places.
Nice report.
Hi Mike,
First time long time. I have been working my way through your blog from the beginning for almost a year. (I took a few months off for books). I first thought of a doaral box idea when you posted about rain coming in the vents during a particularly nasty storm while at anchor. (Never had heard of them). Dang someone beat me to a great invention I still think someone with your creativity and enginuity could figure a workable do it yourself by building some sort of housing over the vent. I’ll touch base again with you when I get to the end of the blog and am up to date. PS. I use the amazon link for all purchases as a thank you for your great information and time spent.
Hey Brian
Thanks for checking in, and for taking the time to work through our blog. As of today there are 2427 posts, so it might take a while. 🙂
Thanks as well for using the Amazon link. I really appreciate that. If all of our readers did that we’d be rocking!