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View Full Version : Got any mathematicians on the board?

STV_Keith
03-17-2009, 07:22 PM
If I have a "vessel" - say a tank, that has 2 x 3/8" holes and 1 x 1/4" holes in it which are open and "leaking", how many GPM do I have to put into it (assuming it's full at the start) to allow for those leaks and maintain 10psi of pressure in the tank?
monterey
03-17-2009, 08:08 PM
I'm not really good at this, but here goes. the answer is going to be 7 or blue. but I my be wrong? :dunno:
PUMP 'HER'
03-17-2009, 09:02 PM
:rollinglaugh:

I'd say a lot, but it may depend on the size of the tank.
digginfordollars
03-17-2009, 11:25 PM
I'd use about a five horse pump with a 2" outlet, put a regulator set at ten psi with a waste gate and you should be good to go. :thumb:
Honestly, I have no idea but I did want to tell you that my water heater went south today.:devil:
STV_Keith
03-18-2009, 08:18 AM
The answer is 85GPM, FYI. :)
just another payment
03-18-2009, 08:24 AM
I would have to say 85gpm, but just a guess
PUMP 'HER'
03-18-2009, 08:45 AM
the answer is going to be 7 or blue.

So close!
PUMP 'HER'
03-18-2009, 08:46 AM
The answer is 85GPM, FYI. :)

Is there some sort of trick to figure it out orrrr..... :dunno:
STV_Keith
03-18-2009, 12:44 PM
You are all wrong...it was 32GPM. :)
PUMP 'HER'
03-18-2009, 02:48 PM
The answer is 85GPM, FYI. :)

But this guy said it was 85.
just another payment
03-18-2009, 04:25 PM
Thats the last time I copy off of him on a test
STV_Keith
03-18-2009, 08:56 PM
But this guy said it was 85.

He lied. :)

Actually, the guy that wrote the formula missed a 0 after a decimal that changed it all this morning.
Akamatsu
03-19-2009, 02:38 PM
Formula to use would be GPM = 29.71 D^2 √P based on Freemans Formula. Doesn't read well but it's 29.71 * Diameter(squared) * (square root of)Pressure.

3/8" hole at 10PSI = 13.2119 GPM
1/4" hole at 10PSi = 5.871954 GPM

For all three holes you get 32.29575 GPM at 10PSI.

29.71 is often represented as 30 in the field.

Formula is what we used in FireScience to determine flow rate of smooth bore nozzle.

Dunno why I felt the need to do this as it was already answered, but I figured I would verify and see if I could.. hehe.

Adam.
STV_Keith
03-19-2009, 03:07 PM
Thanks Adam...at least it's another number in the same ballpark!
digginfordollars
03-19-2009, 11:42 PM
Thanks Adam...at least it's another number in the same ballpark!

Alright Keith I'll bite, what the hell is the purpose of this exercise? Are you going to drill holes in your transom for more motors and you are wondering how big of a bilge pump you will need if they fall off? Or is this some kind of new multi-person beer bong thing for spring break?:boobies::boobies::boobies::boobies::boobies ::boobies::boobies:


Whoa, sorry. Haven't used the boobies thing in a while, got a little carried away.:inlove_anim:
STV_Keith
03-20-2009, 08:57 AM
More boobies is better than less boobies!

The Mercury lower units on my OMC motors don't pump as much water below 1500rpm as the stock ones did, so the motors will get hot if I idle around a bit (like through the channel in Havi). So I want to put in an external electric pump that I can run at idle/low speeds to supplement the water going to the motors.

They are fine once on plane, but I'm tired of only being able to idle for a few minutes, then having to drop one motor into neutral, rev it up to 1500, let it cool off, then put it back in gear.