Ah, practical matters! I have an electric bilge pump that has worked flawlessly for years; I usually test it before each paddle tour(not yet been used in anger). I have also tinkered with electric powered models for years - boats, cars and planes, powered by anything from '300' style can motors to my precious Aveoxes that then cost me about $1000 each, plus the ESC (electronic speed control). Nowadays the technology is well proven and the prices are very low - or about a tenth of what it was then. A small motor has generally an OK no-load resistance (thus fairly efficient at low loads), but at times when it is very highly loaded the brushes might even melt, and its efficency goes down the river, each time you load it over the recommended amps. A bigger has lower no-load resistance, but when loaded like the small one it is much less affected, thus more efficient! Bit like a car with a small engine, compared with a car with a big one all other things being similar (size, weight, et cetera) - The smaller will have better milage at low speed, but at high speed in might very well be the other way round, as the small egine is overstressed and overloaded! The laws of physics might say that a greater spout needs more energy but one should be aware of the fact that small electric motors, especially brushed ones, are far less efficient than bigger - a typical '400' can motor is in the 40% efficiency range under load (typical load 100W), while a non-brushed, slighter bigger, say 250W motor, is in the 80% range, some even in the lower 90's! Thus a small motor wastes more than half the power into the air/water as heat! So, if possible, replacing the motor the unit got with a brushless might be a good idea :-)! A bigger pump is also much more efficient, than a smaller (a matter of Re, foil choices available and surface quality) so the amount of fluid pumped per Ah is very probably much better with a bigger pump. Bigger through-put means you need to use it for a shorter time, thus, as long as the battery can deliver the Amps, bigger is better! My own bilge pump is a big, standard, salt-water-proof boat pump), dirt cheap and very powerful - it seems to use a brushed motor, but I can live with with less than 80% efficency (motors that size use to be in the 80% range, give or take a few percent - a brushless of that size at least 10% better). Tord PS Photos of my istallation can be found at www.foldingkayaks.com -- Be Yourself _at_ mail.com! Choose From 200+ Email Addresses Get a Free Account at www.mail.com *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Thu Apr 09 2009 - 15:57:00 PDT
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