Re: [Paddlewise] Bosworth Series 500-S bilge pump installation

In a message dated 6/11/2002 8:57:43 AM Eastern Daylight Time, 
knelson_at_actionpoint.com writes:


> I'm sure the pump will be fine but how about the battery pack & wiring? Do 
> they need constant replacement?  Constant maintenance I can accept as a 
> given.
> 

>From some experimentation with these widgets, Kevin --- but not including a 
long term installation, to address that part of the question ---  electric 
pumps are impeller driven, using a fan-like device to spin off the bilge 
water into a manifold of tubes that eventually push the water overboard.  
That little impeller spins up pretty fast, and anything (1) cheap, (2) fast 
and (3) mechanical will wear out over time.  The battery will need 
recharging, obviously, and the area in which you keep the battery needs to be 
vented since these batteries will outgas a lot of pressure if discharged 
quickly.  The area of concern for me is the switch and wiring, and, like you, 
I'd like to simplify as much as possible (not always obvious from the look of 
my kayaks).  

One way to draw down complexity is to consider using one of the "automatic" 
electric pumps: the standard "automatic" feature (expensive) circuit (when 
turned on probably with or housed inside the battery container) spins up the 
impeller every two minutes or so, and, if it encounters back pressure from 
water in the bilge, stays on until most water is discharged and the back 
pressure drops off.  

There is also a PWC "automatic" pump (very expensive); the operating 
principles are the same, but the frequency of sampling is much higher --- 
every 20 seconds or so.  (Either automatic pump can be started manually by 
cycling the switch off and on at any time, but you need to be able to get to 
it, and that may not be a good option, especially if it's housed inside a 
sealed bulkheaded compartment.)  The question centers on the value of *not* 
having an externally mounted, "submersible" switch in the system (also 
expensive).  (For approximation, if a "500" series pump is $20, the automatic 
is maybe $45 and the PWC model might be $60, but this is from memory; the 
switch --- same caveat --- is about $45. These aren't "list" prices, but are 
discounted prices from more aggressive retailers.)  

My final decision -- or as "final" as any kayak outfitting decision ever is 
-- is to mount a "submersible" switch just inside the coaming where I can get 
to it without releasing the skirt, and go with the "500" series pump and a 
decent battery (alarm system size is good).  Submersible connections are the 
only way to go, in my opinion --- derived from more than one at-sea test 
deployment of emergency gear in the safety device business --- and are not an 
option; a copious amount of marine RTV on a "waterproof" switch is not the 
equivalent of a "submersible" switch, either.

One other thought --- in addition to venting the area where the battery is 
stored (blow-out plug, flapper, GoreTex sample epoxied over a hole in the 
bulkhead, ...), any pump that is mounted inside the cockpit --- whether foot 
or hand operated or electric --- will generate a partial vacuum, and the 
better the skirt and cockpit rim seal, the more the pump is going to have to 
fight the vacuum to push the water overboard.  There's precious little power 
in an impeller pump in the first place, so having some way to allow an 
equalization of pressure in the cockpit is an advantage in emptying the area 
quickly.  (I have a four inch deckplate/bag "glovebox" in the foredeck of my 
Pintail, and I back off the plate about a half turn while I'm pumping out 
because my skirts are all tight fits (everywhere, unfortunately) and pressure 
builds up quickly, especially with the old Henderson "chimp" foot pump 
mounted there now.)

Good luck --- please share your final ideas and installation.

Jack Martin

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