I don't doubt there are pod drives available and virtually any of them could be installed in a rudder, but they're not very common and therefore expensive. The only ones I found on a quick search probably cost as much as the boat you want to install them on. Therefore my suggestion you look at trolling motors or the Torqueedo. You might be able to contact the various manufacturers and get them to provide just the drive unit and control, for less than the cost of a complete outboard.
However even a folding prop is going to create SOME drag and will run your costs up compared to a fixed prop. Perhaps you could make your own design out of nylon or Marelon for less than the price of a bronze prop.
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
--- In electricboats@yahoogroups.com, "marcdrachten" <mevanderkuur@...> wrote:
>
> Thanks for all the replies.
>
> As for re-inventing the wheel, the set-up I mention is a readily available set specifically designed as marine propulsion. However not yet mounted in rudders. I wonder if a pod with folding prop creates more drag than a trolling motor without. As for decent speed, 3 kts is decent, at 30-40% of max power. I want to be able to get some forward speed in the lesser weather conditions. As for range, we aim for a set-up to to be able to motor for at least 4 hrs at 60% hull speed. But we are limited in battery space, hence the max 24v wish.
>
> Marc
>
> --- In electricboats@yahoogroups.com, "stmbtwle" <stmbtwle@> wrote:
> >
> > A 36v trolling motor provides 100# of thrust and will move a 24' boat with no problem. I'd try one before I spent a lot of money on a "pod" that will only slow you down under sail.
> >
> > A few years ago just for a lark I put a 12v, 28# thrust Minn Kota on my dinghy and pushed my 35', 19,000# houseboat with it. I got ONE knot, average of both directions per GPS. A FOUR HP gas outboard only got two knots.
> >
> > Today I have a 40#, 12v trolling motor on an 18' canoe... it will push two adults to about 4 knots, with a range of some 20 mi on two 6v golf batteries. With that same rig I have TOWED a broken-down outboard motorboat some 16-18' in length (a lot more drag than a 24' sailboat).
> >
> > They work, and they're inexpensive. Try it before you knock it.
> >
> > Then there's the Torqueedo electric outboard that's claimed to put out 6 hp equivalent on 48 volts.
> >
> > I wouldn't try to re-invent the wheel.
> >
> > Willie
> >
> >
> > --- In electricboats@yahoogroups.com, "Eric" <ewdysar@> wrote:
> > >
> > > And trolling motors provide nowhere near the power of a 2.5kW drive that they spec'ed to begin with.
> > >
> > > Eric
> > >
> > > --- In electricboats@yahoogroups.com, "stmbtwle" <stmbtwle@> wrote:
> > > >
> > > > It wouldn't be that hard to glass the business end of a 24v or 36v trolling motor into the rudder; trolling motors (and parts) are readily available. However that setup is going to impair your sailing performance.
> > > >
> > > > I'd simply mount an off-the shelf trolling motor on a bracket. No modifications required.
> > > >
> > > > Willie
> > > >
> > > > --- In electricboats@yahoogroups.com, "marcdrachten" <mevanderkuur@> wrote:
> > > > >
> > > > > Hello,
> > > > >
> > > > > We are investigating to mount an electric pod in our rudder. Anyone with good thoughts? I want to aim for a +/- 2 - 2.5 kW on max 24V due to limited space available on my 24' daysailer. I can stow 2 12V, 270 Amp batteries.
> > > > >
> > > > > DC or AC? and then 24V or maybe 220V or other V with inverter (lower amps, thus smaller cables into rudder) This will however will cost some efficiency.
> > > > >
> > > > > We all ready test sailed with an inboard 24V, 2.5 kW PMG engine to our satisfaction. However fitting in to the rudder will create more flexibility while building and after sales.
> > > > >
> > > > > We are looking for "of the shelf" products to facilitate small series production later on.
> > > > >
> > > > > Any thoughts?
> > > > >
> > > > > Marc
> > > > >
> > > >
> > >
> >
>
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