T&T: dorade vents

[Rudy and Jill Sechez]

Hi-
   
  Just wanted to add a thought, if dorade boxes will be used.  
   
  Less ventilation occurs if the opening/space between the two ends of the dorade box (the end with the cowl and the end with the opening into the boat) does not equal the area of the cowl vent used.  
   
  In other words, a 4" cowl vent has an opening of 12 1/2 square inches (the 4" pipe, not the scoop opening).  The space above the block that separates the two ends of the dorade box should equal or exceed this amount.  
   
  Also, the opening into the boat should also equal or exceed this amount.  If using a 4" cowl, then the opening into the boat should also be at least 12 1/2 square inches (it does not have to be round) and space above it, facing the cowl, should equal or exceed 12 1/2 square inches.
   
  A most effective dorade box system includes a liner, in the hole that goes into the boat.  This helps tremendously in keeping water out of the boat.  This liner extends up from the deck, the amount is not critical (one or two inches seem to work well) and is sealed around its perimeter to stop leaks. 
   
  If you make your boxes, these measurements are used to design the size of the dorade box.  The other is the size of the flanges on the cowl.  Of course, the thickness of the material used need to be taken into account also.
   
  It seems elementary, but it is easy to make or buy dorade boxes without considering these measurements, and since the amount of fair low is greatly impacted by a smaller opening and making the air change directions from a straight path, it can make quite a difference, particularly in hotter climates.
   
  Rudy and Jill Sechez
  Briney Bug- A travelling repair shop, currently in Sanford, Fl.


       
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