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Bilge pump.

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boatshed View Drop Down
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Post Options Post Options   Quote boatshed Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 18 at 9:35am
I noticed that the 8 person rowing boats used in the Boat Race were running electric bilge pumps.

Now, I simply wouldn't bother with a non self-draining boat.  
Steve
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Sam.Spoons View Drop Down
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 18 at 10:15am
Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"
Supernova 395 "dolly the sheep" (now sold but considering a second (mk3) Blaze as her replacement)
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laser193713 View Drop Down
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Post Options Post Options   Quote laser193713 Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 18 at 11:23am
Originally posted by Presuming Ed

Ballpark: taking a cockpit of 3m x 1m x 0.3m deep gives 900kg of water. Whale's largest bilge pump can move 189 L/min, so that's nearly 5 minutes to empty the cockpit. Water is heavy stuff.

While it's doing that, it's drawing 18A at 12V. So that's 18AHrs. A large power tool battery is 3Ahr, so you would probably need at least 7, what with pulling all that current. And that means that your batteries are dead and can't pump any more. And that current is against zero head. Actually pumping the water up and out would pull more.

A lead acid battery of nominal 85AH capacity - so about 40ish available, unless you want to kill it - would give you 2 and a bit capsizes worth of pump time. But that battery weighs 25kg. And you're still pumping for 5 mins a time.

Electric bilge pumps are bad for large amounts of water. If you want to move the water fast, you want a petrol powered trash pump. Honda's smallest will pump 710 lt/min. Weighs 47kg dry, though...

Better to stick with a bailer/bucket, I think.

Wrong, you have suddenly gone from it taking 5 minutes to empty the boat to an hour. 18A divided by 12 would give you the battery usage per capsize. Still, not the right solution for a dinghy.

On the sportsboat I race on we have recently fitted two Lithium batteries that weigh about as much as a drill battery, they are 5Ah each, one runs the instruments for a day and the other is dedicated to bilge pumps. The bilge pump battery will probably have a pretty hard life but we have calculated that it will pump a total of 3000 litres of water before it flattens the battery!
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PeterG View Drop Down
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Post Options Post Options   Quote PeterG Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 18 at 11:48am
I have an automatic bilge pump on my Devon Yawl. It's a small one - rated at around 40l/min. Very useful for when it's choppy, keeping the water in the bilges under control. For serious knock downs there are 2 buckets and 2 sets of arms. The lithium golf cart battery also runs the depth sounder and weighing in at just under 1kg it's far too big - I only charge it once a year. 
Peter
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423zero View Drop Down
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Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 18 at 5:30pm
Well the good news is that GP14 class allow pumps.
Collapsible bucket from Wilco and pump.
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