Electric Bilge pumps

Places, technique, kayaks, safety, the sea...
Post Reply
Andywright
Posts: 22
Joined: Sun Sep 21, 2003 6:03 pm

Electric Bilge pumps

Post by Andywright » Sun Jan 25, 2004 8:21 pm

Does anyone have any experience of using an electric bilge pump in their sea kayak. Attwood pumos make one called the Waterbuster, it runs on 3 AA batteries and shift 3.33 gallons a minute (enough to sort the sea boat out in a couple of mins)Batteries last 5 hrs

Your thoughts a opions would be appreciated.

User avatar
MikeB
Posts: 7958
Joined: Tue Apr 29, 2003 9:44 pm
Location: Scotland

Lecy pumps

Post by MikeB » Sun Jan 25, 2004 10:45 pm

Douglas is your man - no doubt he'll be along soon - -

There are some interesting thoughts on them on some of the Aussie and Tassie sites as well

members.iinet.net.au/~lford1/index.htm
www.users.on.net/pcarter/pumps.html

Mike.

User avatar
sub5rider
Posts: 655
Joined: Mon Mar 10, 2003 4:38 pm

Re: Lecy pumps

Post by sub5rider » Mon Jan 26, 2004 1:19 pm

I use one. It's bungeed to the cockpit floor immediately in front of the seat*. It's not "plumbed in" as I want to be able to drop it into someone else's cockpit if need be. It's also not fit & forget. The pump comes out the boat after every trip rinsed in fresh water and left on top of the dehumidifier for a week. I used to open it up after every dunking too, but I no longer do that because I don't want to wear out the locking meachanism. I also got some silicone grease and gave the "O" ring a going over. I'll also replace the batteries before the next big trip.

I can attest to it's effectiveness, it emptied my Orion's cockpit** several times in one evening when I was practicing self rescues and was no less effective the 4th or 5th time as it was the first. It is even possible to put the outlet pipe over the coaming and then put the spraydeck on over it. It reduces the flow somewhat, and the deck has to be removed again to switch the pump off.

The pump has a rather heavy steel plate on the bottom which, I think, is intended to make the pump sink and it's also perforated to provide a coarse filter. The plate may be removed, but this leaves the impellor open to be jammed by any small stones that may be in the boat. I shall remove the steel plate from mine when I've fabricated an alternative filter.

* the vibes are rather pleasant! :eek

** I did have a drybag wedged between the footrests & forward bulkhead, as I usually do, to reduce the cockpit's volume somewhat.
Nigel, aka Sub5Rider, Onioneer

DaveM
Posts: 145
Joined: Tue Nov 11, 2003 11:51 am

Optimistic battery life

Post by DaveM » Mon Jan 26, 2004 2:19 pm

: Attwood pumps make one called the Waterbuster, it
: runs on 3 AA batteries and shift 3.33 gallons a
: minute (enough to sort the sea boat out in a couple
: of mins)Batteries last 5 hrs.

To avoid dissappointment I'd check that out very carefully before parting with any money, preferably by running one with the same vertical lift that you will use in your kayak.

3.3 gals/min is a fair work rate for the pump, and for 5 hours I'd expect to need a car battery at the very least. In 5 hours that's 990 gallons, or around 4.4 tonnes of water (if it's UK gallons).
3xAA cells? They've gotta be kidding.

Also check whether the spec is in U.S. gallons - they're smaller than ours.

Try putting 6 gallons in your cockpit and look at how shallow it is. Use a 2 gal bucket to half fill your cockpit, the best you can hope for with a capsize and re-entry. You may be in for a shock at how much it holds.

Dave

User avatar
sub5rider
Posts: 655
Joined: Mon Mar 10, 2003 4:38 pm

Re: Optimistic battery life

Post by sub5rider » Mon Jan 26, 2004 11:35 pm

I'm not saying that it's a perfect solution (is there one?) for emptying a boat, but it's viable and it will work for me and, importantly, other members of any group I happen to be with.

Pros: hands free, portable, no holes in boat, no deck clutter

Cons: batteries, needs looking after, weight, no strum box (on mine)
Nigel, aka Sub5Rider, Onioneer

DaveM
Posts: 145
Joined: Tue Nov 11, 2003 11:51 am

No holes?

Post by DaveM » Tue Jan 27, 2004 11:19 am

: Pros: hands free, portable, no holes in boat


Then you need to pull your spraydeck partly off for the outlet tube and to get to the switch.

That doesn't sound like hands free operation to me.

Sounds like bad news in the rough water you're likely to be in when you fall out, which is when you most need it.

Steve B
Posts: 5699
Joined: Wed Jan 16, 2002 2:36 pm
Location: Taunton, Somerset

Re: No holes?

Post by Steve B » Tue Jan 27, 2004 1:03 pm

This is not nearly as far-fetched as DaveM is suggesting, on several counts...

The pump uses 3 D cells, not AA. That's the big torch batteries, three of them weighs a pound. So a lot more juice, somewhere in the region of 5-8 amp hours.

The pump doesn't have to lift the water. Assuming the hose trails down to the waterline (and it would be silly not too) the siphon effect means the pump merely has to accelerate the water and overcome the quite small drag of the hose.

Consider this comparison. The energy needed to lift 3.8 tonnes (the weight of 5 hours x 200 US gallons/hour of water) by say 30 cm is considerable. But merely to push it horizontally is easy - try pushing a heavy vehicle on simple wheels, that's not too bad, then imagine how much easier it would be if it was almost frictionless.

Unfortunately my physics, once quite good, has deteriorated to the extent that I can't do an accurate calculation. But I'd say the figures look pretty reasonable.

Steve B.
Edited by: Steve B at: 1/27/04 2:16 pm

User avatar
MikeB
Posts: 7958
Joined: Tue Apr 29, 2003 9:44 pm
Location: Scotland

Holes!

Post by MikeB » Tue Jan 27, 2004 3:00 pm

"Then you need to pull your spraydeck partly off for the outlet tube and to get to the switch"

Well, that doyen of sea-paddling-pics, Douglas (who is obviously away on another jaunt :D , judging by his silence so far!) has just such a pump fitted into his Quest using bungee to hold it in place on the for'ard b/head. He then has it plumbed in using the readily available connectors sold for hoses in such a manner that he can remove it (for service and maintainance I guess) yet it pumps the water thro a thro-deck on the foredeck.

He did place a link to a pic in an earlier discussion here - pub97.ezboard.com/fukrive...=326.topic

Persoanlly I'm considering using the separate pump with a gel battery as described in one of the sites I linked to earlier in this debate. That would sit nicely behind the seat, with the battery either beside it or in the centre hatch with the wiring passing thro the b/head using a waterproof plug & socket available from chandlers.

The (waterproof) switch required is proving a little more difficult to source at the moment.

Having said all this, personally I have to say that I'd not want to be relying on anything electric in a sea boat so I'll be retaining my b/head mounted foot-pump! Any leccy devices would be nice to have, but not as stand-alone water removers.

Mike

User avatar
Douglas Wilcox
Posts: 3519
Joined: Sun May 11, 2003 1:31 pm
Location: Glasgow
Contact:

pumps

Post by Douglas Wilcox » Tue Jan 27, 2004 6:42 pm

I'm back! sadly not been on a trip, just been ill and trying to catch up at work.

I really like the Attwood pumps. They are a complete sealed unit and mine have given no problems over a years paddling (450km)and lots of rescue practice.

I tested the batteries by putting the Attwood in a garden pond, temp 5 degrees C, and raising the outlet pipe to the same height as my outlet is above deck. A new set of duracells were still running 6 hours later when I went to bed.

Electric pumps may be your first choice in emptying a boat but you need a mechanical backup.

Here is my setup:
www.gla.ac.uk/medicalgene...9quest.jpg

I took out the heavy base plate with holes, but because mine sits on a piece of ethafoam that fills the v in the bilge, the slots at the base keep the grot out of the pump.

I put an inline valve into mine to stop water getting in the deck outlet and running down through the pump impeller. This valve reduces the flow so I would recommend having the outlet within reach and keeing a bung in it. Pull the bung out out when you want to use the pump. I can switch it on by pressing the push switch with my foot, which is why I have it mounted forrard.

With a deck outlet to hand ,you could experiment by sticking a short piece of syphon tube into it with the other end in the water to increase efficiency.

I would not be without the electric pump, which allowed rapid emptying of the boat after practice capsizes and re-entry rolls in these conditions:
www.gla.ac.uk/medicalgene...adgers.jpg

You could also think about reducing the volume of your cockpit by securing shaped ethafoam blocks. Ausie/tassie/NZ cockpits are abot 50 litres smaller than UK cockpits. I believe many of our antipodean friends are used to tackling fairly serious conditions.....

Douglas :)

User avatar
Jim
Posts: 13497
Joined: Sun Apr 21, 2002 2:14 pm
Location: Dumbarton

Re: No holes?

Post by Jim » Tue Jan 27, 2004 9:21 pm

YES!

As an engineer I can correct Steve B for once!

You will only get a siphon effect whilst the water level inside the boat is higher than the water level outside the boat. Depending on just how heavily laden the fore and aft tanks are it is not impossible that even a badly swamped boat would have less water inside than out. Even if you do start with a positive head, by the time the boat is nearly empty the outside waterline will be higher, only a fast planing craft can break this fundamental situation, unless you fit a false watertight floor!

Without a siphon you will have to raise the water to the highest point of the pipe, so probably about 30cms in the worst case if going over the rim.

Also 200 US gallons of sea water per hour over 5 hours is 3.88 tonnes, not 3.79 tonnes as you have clearly calculated ;)

As for whether a 4.5V low current pump can or can't handle that, I really can't calculate - I'm not a spark! The testimonies appear to be here to say they can, although of course Douglas' skin fitting will be less than 30cm above his worst case water depth, and you have to remember that the situation is always in the pumps favour the deeper the water is and gets worse as it goes down, whether or not it ever receives the benefit of a siphon.

Would I go electric? Possibly, my deck mounted pump takes up a lot of space in my day storage /large item storage area behind my seat, a compact electrical pump and battery located elsewhere would be a real boon. I always carry an easy bailer hand pump as a back up and to lend out anyway so failure would not be a complete disaster - although that does of course require the deck to be off.

JIM

Steve B
Posts: 5699
Joined: Wed Jan 16, 2002 2:36 pm
Location: Taunton, Somerset

Re: No holes?

Post by Steve B » Wed Jan 28, 2004 5:53 pm

JIM> "YES! As an engineer I can correct Steve B for once!"

Re the siphon - are you sure it's a bad as you say? I don't mean the siphon effect will reduce the head to zero*, only that it is reduced to the difference between inside and outside but you can disregard the height over the cockpit rim. So maybe two or three centimetres not 30.

(* Ok I did say "The pump doesn't have to lift the water" but that was sloppy language, I meant it doesn't have to lift it over the cockpit rim)

Re the weight of the water, it's a fair cop, I forgot to allow for the extra density of seawater. Of course if we capsized in the middle of Lake Windermere as I once did as a beginner, it would be different again because I was only about 12 and in those days a ton was 2240 lb. (And D cells were U2's)

Steve B.

User avatar
Jim
Posts: 13497
Joined: Sun Apr 21, 2002 2:14 pm
Location: Dumbarton

Siphon

Post by Jim » Wed Jan 28, 2004 8:12 pm

The siphon only works when you have the outlet water level lower than the inlet water level. In the normal case as described, switching off the pump will allow the water to back siphon into the boat if you leave the outlet in the water and don't have a non-return valve. This is easily demonstrated when homebrewing :)

I can see where your thinking comes from - if the water falls under gravity once over the cockpit rim it will form a suction (if the pipe is under water) of some kind to your benefit. My fluids goes fuzzy now! Certainly to prime the pump you need to be able to lift the water to the cockpit rim, I'm not totally certain what happens after that. I failed fluids the first time round. I'll try and remember to ask a marine engineer tomorrow!

JIM

Steve B
Posts: 5699
Joined: Wed Jan 16, 2002 2:36 pm
Location: Taunton, Somerset

Re: Siphon

Post by Steve B » Wed Jan 28, 2004 10:32 pm

Yes please Jim, it'll be interesting to know.

Steve B

User avatar
Jim
Posts: 13497
Joined: Sun Apr 21, 2002 2:14 pm
Location: Dumbarton

Re: Siphon

Post by Jim » Thu Jan 29, 2004 10:57 pm

The Engineer I spoke to isn't really a 'plumber' although he has been working on pipes recently. He also reckons you do need to lift the water all the way to the cockpit rim the whole time but then went off on a tangent about types of pumps which I'm sure isn't relevant!

The original question was if battery power could handle it. I suspect it could because it only moves a small amount of water each revolution (and of Douglas says it ran for 3 hours or so in his pond). Some of the pumps at work will shift over 100 tonnes per minute, but of course the craft in question do have considerable sized generating plant, and they are quite rare pumps! :)

JIM

ianm
Posts: 6
Joined: Sun Jan 11, 2004 11:36 am

bilge pumps.

Post by ianm » Mon Feb 09, 2004 5:01 pm

If you didnt want to pull your spray deck to pump out the water you could always buy a rocker switch that activate the pump as the water is rising.
The only draw back being that if you roll its going to pump untill you get upright again.

Post Reply