Hi hanermo,
The boat being discussed has a total displacement of about 3500 lbs, so dedicating 1200 lbs (about 35% of the operating boat weight) to the "fuel tank" alone does seem rather high. I would hesitate to permenantly install 3 or 4 "guests" that never leave. Most 3500 lb boats don't have 1000 lbs of payload available.
I notice a distinct drop in sailing performance with a total of 4 people (including me) aboard my 2500 lb trimaran. The people alone get close to the 1000 lbs of total available payload. Even on my 10,200 lbs ketch, a crew of 5 slows her down quite a bit.
But everyone uses their boats differently, so if sailing or motoring performance isn't important, or if one don't really expect any guests onboard, then one can choose a much larger battery bank. The last thing that you want to do is to push the boat's weight past the design limit, doing that in rough conditions could be the last thing you get to do...
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "\"hanermo\" - CNC 6-axis Designs" <gcode.fi@...> wrote:
>
> Actually, 1200 lbs of 480 kgs is not a lot of load.
> Figure abou half of that for normal motor and batteries, so the real
> "extra" mass is maybe 240 kg.
> Thats two big adults.
>
> I see no issue with 2-3-4 extra people on board.
>
> As far as pods, why not make one or have one made in steel ?
> I cuold certainly make a steel pod in a few days, with a bolt-on washers
> (2 flanges, turned on a lathe, nitrile rubber seal in between, bolted
> with 6 mm shcs every 1.5" / 40 mm on a 14" diameter).
> Dead easy.
> 100$-200$ in material, 3-8 hours with a lathe. welded endcaps.
> Good to 3-10 bars, or up to 20-50 m depty immersion.
> Replace the nitrile rubber seal every 10-20 openings, when changing
> batteries.
>
> Any machine shop or jobshop in the us can make one in a few hours.
> Use mild steel to keep it cheap, and coat with a paint on liquid rubber
> coating (good for permamnent immersion). You can have neon colors if you
> want.
> Both connectors and cables are available in immersion proof varieties,
> or just seal with epoxy and have a 5 m pigtail come out (cheaper).
>
>
> > 4 hours at 60% hull speed is going to take a LOT of batteries. Voltage
> > makes a difference but as far as running time is concerned it's
> > WATT-HOURS that count. Let's say you need your 2.5kw to get your
> > required speed. 4 hours at that output is 10 kwh. A normal-sized
> > lead-acid battery holds about 1 kwh. So you'll need TEN of them,
> > MINIMUM. That's about 600# of batteries (probably more). If you want
> > them to last you don't discharge them much more than 50%, so that
> > makes TWENTY batteries, or 1200#. With that much extra weight on a 23
> > footer, propeller drag might be the least of your worries.
> >
> > Willie
> >
>
No comments:
Post a Comment