Dorades?

[Bill O]

Originally Posted by MicHughV

I've had dorade boxes on previous boats.

While you can remove the cowl vent and replace with a cap, the dorade box typically has small drain holes situated somewhere.

I can tell you from personal experience, that even with the cowl vent removed and cap in place, a wave breaking over the boat will find that little drain hole, and you will get water inside the boat.

Were the boat to turn turtle, I could not say, how much water will enter the boat thru' the dorade box, probably some, but not likely to flood or sink the boat.

How tall was your stand pipe inside the box and your box had a baffle? Yes a properly designed box will have small weep holes, but would be very difficult to get water bellow w/a stand pipe that is several inches high and the cowl removed/capped.

[MicHughV]

I could not tell you exactly, but the boxes were about 6" high, and the stand pipe inside probably had about two inches clear to the bottom of the box lid. There were two small weep holes, one located either side of the box, about 1/2" or so in diameter, located adjacent to the vent. The dorade boxes were not baffled.

I built the dorade boxes on my first boat myself. There were four of them.

My second boat also had dorade vents, but the box was integral to the fiberglass deck and they also had weep holes.

I can dig up some photo's if you want.

[Bill O]

Originally Posted by MicHughV

I could not tell you exactly, but the boxes were about 6" high, and the stand pipe inside probably had about two inches clear to the bottom of the box lid. There were two small weep holes, one located either side of the box, about 1/2" or so in diameter, located adjacent to the vent. The dorade boxes were not baffled.

I built the dorade boxes on my first boat myself. There were four of them.

My second boat also had dorade vents, but the box was integral to the fiberglass deck and they also had weep holes.

I can dig up some photo's if you want.

No need for any photos, I've made a few myself.

We oversize the box (as described on page 56/57 of the manuscript linked previously (response #29)) to allow plenty of air flow below.

[MicHughV]

I don't recall where the design of my dorade boxes came from. At the time I was building my boat, I had a library of "how to" books, as obviously I had never built a boat before. Come to think of it, the book "From a bare hull" by Ferenc Mate may have been my source, but my memory is fuzzy here..the cowl vents were not very big...4-6" diam. maybe ??? They did work though.

During one or two rough passage, I did have waves come across the boat and thru' them, nuisance water really, not a sinking factor per se, but it did fly everywhere, cushions, books, etc.

Taken as a whole, that probably represented about 0.005% of my time on the water.

[TeddyDiver]

Originally Posted by goboatingnow

Correct. It reminds me of the following conversation on a well known vhf manufacturers exhibition stand.

“ I see your new radios are waterproof to 2metres”

“ yes that’s correct sir “

“ well what happens if I capsize and I’m 4 metres down “

“ I think sir, the vhf radio will be the last thing in your mind at that point “

At that moment of capsizing yes.. but afterwards, maybe loosed your rig and all electronics wet one could hope to have a working vhf thus keeping the water out of the boat on severe knockdown or capsizing is quite essential.

[MicHughV]

4 metres depth would suggest that the boat had sunk by this point...

[Cyrus Safdari]

Dorades can be sealed from below with a simple screw-in deck lid.

But this brings up a question about installing the classic teak box and cowl vent Dorade. The box is typically positioned fore-aft, with two internal sections divided by an interal baffle: one section has the cowl and scuppers for rainwater to drain out, and one section covers the standpipe that leads the air below.

So, which in which direction is the box positioned; which section is fore, which is aft & why?

[wingssail]

Originally Posted by Cyrus Safdari

Dorades can be sealed from below with a simple screw-in deck lid.

But this brings up a question about installing the classic teak box and cowl vent Dorade. The box is typically positioned fore-aft, with two internal sections divided by an interal baffle: one section has the cowl and scuppers for rainwater to drain out, and one section covers the standpipe that leads the air below.

So, which in which direction is the box positioned; which section is fore, which is aft & why?

"We originally designed the Dorade box with two holes for the ventilator to screw into - one offset and one directly over the downtake for use in fine weather. But the offset pipe worked so well we just eliminated the other hole altogether. So that’s how the classic Dorade vent evolved - and I honestly think that there still isn’t a better way to do it.

The trouble is that all these elements of the ventilator have to be designed correctly for the idea to work right. The cowl area has to be four times that of the standpipe - that is, twice the diameter - or else it won’t collect enough air. The box has to be at least six inches tall or the downtake pipe can’t stick up far enough above the deck to prevent water sloshing down it into the cabin; and the box has to be big enough so that there is enough volume for the air and water to get separated inside it. There has to be one good-sized scupper - at least one inch square - on each side of the after face of the box, so the water can get out whichever way the boat is heeling, but so that a minimum amount will get in when a sea comes aboard." Rod Stephens

Stephens doesn't say it specifically but I think he puts the cowl on the aft end of the box, the scuppers near it on the aft face, and the down pipe forward. The idea being that water coming aft and into the cowl or along the deck has to run forward to get to the down pipe.

That is the way I've seen them also.

[Cyrus Safdari]

Originally Posted by wingssail

Stephens doesn't say it specifically but I think he puts the cowl on the aft end of the box, the scuppers near it on the aft face, and the down pipe forward. The idea being that water coming aft and into the cowl or along the deck has to run forward to get to the down pipe.

That is the way I've seen them also.

I've seen them both ways.

I read that exact paragraph and thought the same but he doesn't explain why

The scuppers of course have to be in the section with the cowl, regardless of whether it goes fore or aft

IMHO you'd want the standpipe portion aft, assuming the cowl is facing forward, which it probably is most of the time, so the air (while diverted) still is flowing roughly in the same direction aft-ward and doesn't need to do a 180 turn to enter the fore section?

I dunno.

[Bill O]

Our box orientation is with the cowl aft and stand pipe forward. Theoretically this allows the water to drop out and not directly blow into the stand pipe. Additionally, we bean cut our stand pipe so the taller side faces the cowl vent/airflow

As described in Rod's manuscript, I have seen boxes with 2 positions for the cowl vent. One was the normal way and the other was a direct down the stand pipe in good weather. Never did it that way since it seemed like too much work to change them and if you used the direct down, you could get caught w/an unexpected pop up when you were away from the boat.

[Cyrus Safdari]

Originally Posted by Bill O

Our box orientation is with the cowl aft and stand pipe forward. Theoretically this allows the water to drop out and not directly blow into the stand pipe. .

Nevermind changing the cowl vent position itself, indeed too much a PITA for slight benefit

So why wouldn't this happen if the teak box was the other way,? The cowl and standpipe would still be in separate parts of the teak box so nothing goes straight down

[goboatingnow]

I had a type of dorade on an old boat. But it also had a sealable fixture that allowed a circular disk to be pulled down inside the protection box to close the deck through pipe.

Seemed very sensible , even if by the time I owned the boat this fittings was broken.

[Bill O]

Originally Posted by Cyrus Safdari

Nevermind changing the cowl vent position itself, indeed too much a PITA for slight benefit

So why wouldn't this happen if the teak box was the other way,? The cowl and standpipe would still be in separate parts of the teak box so nothing goes straight down

Good question, just never seen a box oriented in that manner. Maybe give give it a try and see how it works out.

Our original boxes were teak, but now we have boxes made of HDU (high density urethane). Much lighter weight and can be painted to keep the box from heating up like the teak boxes did.

[KayZee]

[QUOTE=wingssail;3692617]The name of the boat is Dorade (Dor'-aid)


Dorade's revolutionary ventilators are called "Dorades"

Now if only we knew why the esteemed O. Stephens called the boat Dorade.



Based on my reading about the french name for bream and the history presented here for the race yacht, I feel good going with Door-aid.

[mako]

There's also the style of dorado which is stacked vertically, not a horizontal offset box. Bit more streamlined looking also.

It would be nice to find a way to fabricate the cowls in larger sizes. 6" are tough to find and very expensive. Forget about 8". Perhaps molding them in fiberglass is best, since forming metal would be too difficult.