alternate auxiliary propulsion

[curtisv]

"As an example of what could be, Torqeedo makes electric outboards that are thrust rated at 9.9 hp, propulsive power rated at 8 hp (gas outboard comparable) with 24 volt batteries that, interpolated from their data, at half throttle for a Compac 23, should provide about 20 nm on a charge."

Isn't that the Cruise 4 that is rated to that power level? That is a 48v system.

Where did you find that weight? They recommend 200 amp/hour batteries. A single 4d battery in that size is about 135 pounds and costs $500, and you need four of them for 48v.

Torqeedo rates the shaft power on the Cruise 4 as about 4.7 hp. If you are running at half power (2.35 hp) a single HP is 746 watts. So for 2.35hp that is 1753 watts of power, but Torqeedo also says their engine is roughly 50% efficient. So you are really looking at 3506 watts of power. 3506 divided by 48v is 73 amps. So basically for an hour of use you would use about 73 amp hours from your battery bank.

How are you going to recharge that loss?

Shawn

They recommend 180AH if you use lead acid simple because lead acid doesn't take well to being discharged fast.  The range specs are for 200 AH so to get 20 miles and the most possible power you would need 200AH at 48V.  Simply not practical from a weight standpoint.  But it is worth pointing out that this was pushing along at 5 knot, getting close to hull speed.

It would be a lot more practical to go with the 24V model.  That would be half the battery weight and half the cost.  At half throttle you go 2.7 knots (in a 40 ft boat weighing 2.3 tons) and go over 44 miles.  Not bad.  Still 270 pounds and $1,000 is a lot.  Still too much IMHO.

What they'd like to sell you is a 77AH 24V Lithium battery.  Range would be 1/3 of the 200AH so maybe 14 miles.  Not bad.  The good news is it is compact and only weighs only 42 pounds.  The bad news is it costs about $6,000.  That cost is really high and it might be better to shop around for lithium batteries intended for cars at some electric vehicle sites.

The more practical solution might be a model 401 with 24V 20AH integral lithium battery.  According to the web page range with "30ft, 3,750lbs" craft, sort of comparable to CP23 but longer waterline, would be 2.1 miles at 2.1 knots.  That's easily enough to get out of the marina and back in but certainly won't get you home if you are 5 miles out and wind dies but if you were willing to go at 1.3 knots it would get you home.

The 401 is the 12V and the 801 is the 24V version.  The 801 provides more power.  Either should give you about the same range at about the same speed.  The 401 will give you better range if you do twist the throttle to open and probably 3 knots.  Given that these things are over $1500, still not too practical from a cost standpoint.

The nice thing about lithium batteries is they don't mind being left discharged for long periods of time.  In fact they prefer being stored dead flat discharged.  So it is practical to use a solar panel and its OK for the battery if it takes two days to bring the charge back up.  Not OK if you want to sail the next day.  So add $500 for a 60-80 amp panel. --- even more cost.

For the sailor on a budget these things are totally impractical.  For the sailor with money to spare and a desire to play with electrics maybe its a nice toy.  My minkota cost about $500 and isn't so power hungry that it needs a huge battery bank.  Then again its not working at the moment so...

The base motors for the 401 or 801 (no integral battery) are about $1,000.  Take a 401 and add a pair of group 31 at a bit over 100AH and you'd probably have about 5 miles at 2 knots and 12 miles at 1 knot.  This is only going down to half charge since fully discharging a lead acid battery is bad for it.  And then you'd have the batteries immediately.  OK if you trailer and can go home and charge or have dockside charging.  Otherwise this doesn't work either.

btw- a 6 HP motor can push you at close to 5 knots, but it takes a small fraction of that energy to push you at 2 or 3 knots and next to nothing to push along at 1 knot.  Where to get the recharge energy is the big problem with lead acid.

So maybe the technology is almost there.  But not quite unless you have lots of money to burn on a small and light but really expensive lithium battery.

Which brings us back to the sculling oar.  :-)

Curtis

[Shawn]

"would be 2.1 miles at 2.1 knots.  That's easily enough to get out of the marina and back in but certainly won't get you home if you are 5 miles out and wind dies but if you were willing to go at 1.3 knots it would get you home."

If you fight a current it may or may not be enough though. If I were to go that route I'd have my Silver Century Plus longshaft stored somewhere on board... just in case.

"Given that these things are over $1500, still not too practical from a cost standpoint."

There is a place in Canada that sells the 401l for around $700 on ebay if someone wanted to go that route. I think they sold the 801 for around $800 or so. From a recharging standpoint if it were me I'd rather the 12v system as it would be easier to recharge with my existing 40w solar system.

"a 6 HP motor can push you at close to 5 knots,"

I have the Tohatsu SailPro 6hp on my 23 and it is more then enough to hit hull speed with power in reserve.

"Which brings us back to the sculling oar. "

Certainly cheaper! It would be interesting to see how well that would work on a 23, I would think current will be an issue.

Good luck!

Shawn

[curtisv]

"would be 2.1 miles at 2.1 knots.  That's easily enough to get out of the marina and back in but certainly won't get you home if you are 5 miles out and wind dies but if you were willing to go at 1.3 knots it would get you home."

If you fight a current it may or may not be enough though. If I were to go that route I'd have my Silver Century Plus longshaft stored somewhere on board... just in case.

Certainly is a valid point.  Not too practical.

"Given that these things are over $1500, still not too practical from a cost standpoint."

There is a place in Canada that sells the 401l for around $700 on ebay if someone wanted to go that route. I think they sold the 801 for around $800 or so. From a recharging standpoint if it were me I'd rather the 12v system as it would be easier to recharge with my existing 40w solar system.

The 401L, 401S, 801L, and 801S don't have integral batteries and so are $500 cheaper.  Still $700 is a real good price since they normally go for $999.

"Which brings us back to the sculling oar. "

Certainly cheaper! It would be interesting to see how well that would work on a 23, I would think current will be an issue.

Good luck!

Shawn

I think that if Lin Pardey can move their 30 foot 20,000 pound Talisan at near 3 knots, I can manage ... at least a knot or two.  :-)

Curtis

[Bob23]

   Certainly not to doubt the Pardeys, but that doesn't sound right. Before I had a motor on my old Seapearl 21 (600 lbs), I carried two 9 1/2' wooded oars. Douglas fir, me thinks. Great old oars...wish I'd kept 'em. Where was I...oh, yeah. Rowing that boat into a 2 to 3 knot current it was hard to make appreciable headway, and that's without wind! Sure, I was making some progress, but it took a long time and a lot of calories. Next season, me and Miss Nissan started a long and meaningful relationship which ended when I sold the 'Pearl.
   But this sculling oar idea has me intrigued so I'll probably build one this summer just to play with it. Long before that, I'm sure this thread may become history.
   Being a cyclist of sorts, pedal power is also a source. I wonder if one could hook up a drive system to and old outboard lower unit with a bigger prop designed to turn slow?
Bob23

[brackish]

"As an example of what could be, Torqeedo makes electric outboards that are thrust rated at 9.9 hp, propulsive power rated at 8 hp (gas outboard comparable) with 24 volt batteries that, interpolated from their data, at half throttle for a Compac 23, should provide about 20 nm on a charge."

Isn't that the Cruise 4 that is rated to that power level? That is a 48v system.

Where did you find that weight? They recommend 200 amp/hour batteries. A single 4d battery in that size is about 135 pounds and costs $500, and you need four of them for 48v.

Torqeedo rates the shaft power on the Cruise 4 as about 4.7 hp. If you are running at half power (2.35 hp) a single HP is 746 watts. So for 2.35hp that is 1753 watts of power, but Torqeedo also says their engine is roughly 50% efficient. So you are really looking at 3506 watts of power. 3506 divided by 48v is 73 amps. So basically for an hour of use you would use about 73 amp hours from your battery bank.

How are you going to recharge that loss?

Shawn

Weight came from their charts using their batteries, Two LM batteries at 42lbs. each and a motor at 40.

Capacity was an interpolation from their charts, and probably rough.  Their range charts assumed moving a load almost twice the displacement and waterline length as the Compac using half power to achieve 5 knots over twenty miles with 200 Ah lead acid batteries.  My interpolation admittedly rough is that you could almost do that using much less power with the two 77 AH LM batteries.  However, two additional batteries would only add another 84 lbs.  

My 9.9 hp gas does 5 knots at about 1/4 throttle.

Thing is, the setup is extraordinarily expensive at this time, and it is with an outboard.  I would like to see a reasonable range, reasonable weight, that can be set for optimum trim and silent running at reasonable cost.  Not there yet but some day.....

With regard to rowing or sculling a CP23, I'm a runner, get plenty of exercise, not too interested in adding to that load, but would be interested to see how it comes out if someone tries it.

[Craig Weis]

If you go electric the skipper can always tow a dingy with a set of batteries on board, or a small gas generator in the dingy. You need long and fuse protected cables.

I think that's funny.

skip.

[bmiller]

   Being a cyclist of sorts, pedal power is also a source. I wonder if one could hook up a drive system to and old outboard lower unit with a bigger prop designed to turn slow?
Bob23

Check this out.

[Craig Weis]

The fellow who pedaled hard, fast enough, and long enough to make it across the English Channel in the Gossamer Challenger I believe had a sustainable hp of 1/6 hp...is that enough to move your Com-Pac with 'man' power? That may not be the accurate hp but it's close.

skip.

[Steve Ullrich]

Human powered boats: http://video.google.com/videoplay?docid=-766626016448012163# worth a look...

   Being a cyclist of sorts, pedal power is also a source. I wonder if one could hook up a drive system to and old outboard lower unit with a bigger prop designed to turn slow?
Bob23

Check this out.

[Bob23]

Cool stuff, guys. Human power is quite intriquing, eh? I was always amazed at the calories needed for the Gossamer crossing, cross-the- country cycling, and various cross the Atlantic rowing expeditions. And did you know that cycling is the most efficient form of human transportation? What tidbits of knowledge one can find here at the site.
   In reality, I'll stick to my Nissan 8 and play around with a sculling oar that I'll build this summer. It's really easy and cheap to build a long oar...just need the time. But I'll get my rowing fixes from my Alden Ocean Shell.
   Hey...didn't the Vikings row thier boats? It would be interesting to learn more about those gentle and loving people!
Bob23

[Craig Weis]

Wait one moment. " Vikings row their boats? It would be interesting to learn more about those gentle and loving people!" ...that would be the same clan that rowed down the coast and invaded England and the very same folks famous for the 'butter fly cut' where hands and arms are bond up over the head and with the face facing the post or tree, and once correctly positioned with ankles staked to the ground, a sideways 'H' knife cut from the nape of the neck to the tail bone, and from shoulder blade to shoulder blade top side and hip to hip bottom side was made. Then once the flesh was peeled the count was started and bets placed by the 'doers' on how many times the lungs would 'butter fly'. This 'H' cut was especially popular when done to females...those same "gentle and loving people"? [History Channel].

Yep I'll bet they rowed the long boat all over the chart that they didn't have.
Use to be a real Viking long boat on display at Lincoln Park Zoo in Chicago in a glass display house. Home of my first job. Picking up paper for Dan Rostenkowski before he went to prison for having JUST a little too much Federal property in his Chicago basement.

skip.

[Bob23]

Ahh, Skipper:
   It was a bit of my satirical sarcastic wit at play there. Still and all, pretty good navigators, eh?
Bob23

[Caboose]

Being an electrician working with motors and controls systems, I find interest in this subject. Most of the motors and controls are of three phase 240-480 volt systems. I work on across the line contactors, soft starts, and VFD (variable frequency drive). AC or DC, it's still flowing electrons that we aim to control. Rule #1 - Electricity and water don't mix. When I say water, I also mean dampness, as in the "sea air".  I'm not a lake sailor, but I suppose dampness is less but still a factor.

Before anything, remember it takes only 0.001 amps to kill.

I've also got a friend that due to his Atomic 4 failing on him too many times, he decided to go electric drive on his S-2 sailboat. His S-2 is thirty feet long and about ten thousand pounds total weight. His system is not a back yard/shade tree system, but a system built and made for marine use. It's a 48V DC system that uses 6V golf cart batteries. These batteries are very close in size to a standard car battery. According to his figures, his total added weight is around 100-200 pounds, due to the removed weight of the Atomic 4, transmission, and a full tank of fuel. The added weight is lower and more centered though.

Now for the cold hard facts. Throw out the idea about recharging while under sail. Why, I'll tell you. In order to recharge the system needs to be "on" and the prop to be turning at a good rate of speed. A very large solar charger would work a lot better and faster. A full day of sailing would not put back the energy used for a 1/2 mile trip under power. We've done the math. The one thing never talked about is how loud the motor is while recharging under sail. If be could do it all over again, he would make the motor removable somehow. He would also opt for two smaller motors for better control in tight conditions while going slow.

After seeing his system in action, I'll stay with a small outboard.