Re: Water flow rate through drain holes (corrected)

From: SolarFry@aol.com
Date: Thu Feb 03 2000 - 18:23:17 PST


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{:^)

So..

You need to know how many gallons of water are needed to flood cockpit in
order to find out how much time till the lady drowns.. She really doesn't
know how to swim. Did you know that? :^)

If the 1 inch drain fitting has an inner diameter of 1/2" we would expect an
exhaust rate of roughly 2.5 gallons per minute? That is assuming no back
pressure from water on other side.. How many gallons can you stick inside
cockpit? Say for sake of discussion you would get 125 gallons inside cockpit.
It would then take 50 min to exhaust that much water? So you would have to
sit in water for 50 minutes? If you went to a 1 1/2" drain that has an inner
diameter of 3/4" you would cut that time in half? 25 minutes sitting in water?

Did I get this right?

SF

In a message dated 2/3/00 2:15:49 PM Pacific Standard Time,
panache426@hotmail.com writes:

<< Subj: Water flow rate through drain holes (corrected)
 Date: 2/3/00 2:15:49 PM Pacific Standard Time
 From: panache426@hotmail.com (Jim Nolan)
 To: wwpotter@tscnet.com

 Recently there's been discussion of drain hole sizes for flooded boats.
 Here's some data that may help you decide about drain holes.
 
 This is the water flow rate through various drain hole diameters. The flow
 is in gallons per minute, drain diameter in inches. This is for 6 inches of
 water head. In other words if your boat had 6 inches of water above the
 drain hole, this is the rate it would flow out into the air. This also works
 for water flowing into the boat (sinking). From the chart you can see that
 the water flowed into the P-15 in the brochure at 45.4 gpm (two 1.5" holes
 at bottom of hull). Question - after how many minutes would the lady be
 swimming?
 
 0.25 inches .63 gpm
 0.5 inches 2.52gpm
 0.75 inches 5.67 gpm
 1 inch 10.08 gpm
 1.5 inch 22.7 gpm
 2 inch 40.34 gpm
 2.5 inch 63 gpm
 3 inch 91 gpm
 3.5 inch 123 gpm
 4 inch 161 gpm
 
 The formula used is:
 
   Flow rate (cubic inches/second) = 0.74 x Area x square root (2 x g x h)
 
 g = 386 in/sec/sec
 h = head in inches at any instant
 gallon conversion: 235.2 cubic inches to the gallon
 
 Multiply flow rate by 60 and divide by 235 to get gpm.
 
 Simplifying:
 
 Flow rate (gpm) = .1889 x Area x square root (772 x h)
 
 This formula DOES NOT take into account length of drain pipe. More viscous
 fluids, such as oil, would drain much slower. Someone please check the
 calculations and formula. Thanks,
 
 Jim Nolan P-19 #426 Panache
>>



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