Author Topic: Daydreaming about a Saildrive  (Read 809 times)

SV Azimuth

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Daydreaming about a Saildrive
« on: July 15, 2020, 02:20:17 PM »
I know this is simultaneously impractical, expensive, and really just a daydream/thought experiment... but how realistic would it be to rebuild the engine mounts, flip the engine around, cut a hole, and add a saildrive to the 365? The prop location would remain about the same and we'd get to remove the v-drive and eliminate the nuance of having so much shaft exposed. Bonus if you installed a new-fangled rotating saildrive for extra marina maneuverability! It's fun to think about at least :D

S/V AMITY

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Re: Daydreaming about a Saildrive
« Reply #1 on: July 22, 2020, 04:16:15 PM »
  I'd put in a bow thruster long before a saildrive.  Interesting thought excercise though...

Jordan

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Re: Daydreaming about a Saildrive
« Reply #2 on: July 24, 2020, 10:00:24 AM »
Sailing Uma actually did that with their new electric engine. It's not a 365, but a '72 Pearson 36 (I think).

SVJourney

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Re: Daydreaming about a Saildrive
« Reply #3 on: July 24, 2020, 02:02:28 PM »
https://www.youtube.com/watch?v=WAhlrGck-bc&list=PLx_mGFQfb39F5l-KnNy3nkWOhJAHXzlPx&index=22&t=0s

I could see doing something like they did. Hang as much renewable source that I could on a 365.  With a small generator under the cockpit and a lithium battery pack under the cabin sole.  Then I could convert the engine compartment into usable galley storage.  Huge $$$ though.  Would only think about it as opposed to a repower.
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Jordan

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Re: Daydreaming about a Saildrive
« Reply #4 on: July 26, 2020, 11:14:56 AM »
Yeah. I put a price cap on this motor, and if it requires being removed, I was going to switch over to electric (sail drive)

Dale Tanski

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Re: Daydreaming about a Saildrive
« Reply #5 on: July 26, 2020, 01:27:45 PM »
Jordan,
You could drop in a new diesel for less than the cost of a typical diesel tear out and installation of an electric conversion.   If you think it's difficult to keep your house batteries charged to keep your ice box cold on the hook, do the numbers on that battery bank recharge.  You also loose your ability to recharge the house bank while motoring and then there is the added weight issue....

Dale
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Maruska Hull #40
"Maruska"
Pearson 365 Cutter Ketch
1976 Hull #40
Buffalo, N.Y.

Jordan

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Re: Daydreaming about a Saildrive
« Reply #6 on: July 26, 2020, 09:55:39 PM »
Jordan,
You could drop in a new diesel for less than the cost of a typical diesel tear out and installation of an electric conversion.   If you think it's difficult to keep your house batteries charged to keep your ice box cold on the hook, do the numbers on that battery bank recharge.  You also loose your ability to recharge the house bank while motoring and then there is the added weight issue....

Dale
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Maruska Hull #40

Yeah. I'm not even certain the alternator works. Remember, she hasn't started in weeks. This was mostly frustration, but it's a real decision. My guy said she was strong, and now I have a fully rebuilt injector pump and new injectors. Once I get this water pump fixed, I'm probably gonna stick with her for another 15 years. But if not, I could totally see myself just saying screw it, and moving forward with the conversion.

ZULU40

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Re: Daydreaming about a Saildrive
« Reply #7 on: August 11, 2020, 02:14:56 PM »
Yes Uma is a 36

I didnt see this version run but I thought the former didnt really cut it. They had a direct drive 10hp electric, which should behave like a 15-20hp ICE, which is a bit like running a W40 at idle to 1400 rpm.
They were travelling very slowly, like 2-3 knots so as not to burn up all their battery. Obviously something like this is going to be range and speed limited because of hp available on the one hand and the cost of the battery on the other. Second hand Tesla or Prius batteries would change things, desirable too is a get out of jail generator.

Ive seen chinese 10kw air cooled gen sets for less than A$1,500. Is that complicated? well Im not sure it would be all that easy to cool it.

Really I think it needs a 15-20hp electric drive, and like he points out it needs coolant or somethings gonna melt in sustained use
On the plus side you can scratch all the thru hulls, fuel tanks, and the transmission, and cheap second hand legs arent hard to find
« Last Edit: August 11, 2020, 02:19:32 PM by ZULU40 »
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SVJourney

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Re: Daydreaming about a Saildrive
« Reply #8 on: August 11, 2020, 10:33:16 PM »
Zulu brings up some really valid points.  I would want the ability to sustain 5 knots indefinitely.  (or for as long as the diesel lasts)  Hence generator.  And I would want a good marine rated generator.  Nice part is that if you had a 4kVW generator with DC voltage optimized to recharge your lithium banks, you wouldn't need to run continuous.  Just long enough to recharge while motoring. 

I do think we will start to see a lot more of this in the future as lithium becomes more mainstream.
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ZULU40

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Re: Daydreaming about a Saildrive
« Reply #9 on: August 12, 2020, 02:25:16 AM »
Last part first, I think we are more likely to see the Sodium battery making this proposition affordable, in the meantime which will still be years Lithium are the best choice.
In either sphere the battery size is going to be quite large, or you have resigned yourself to having becalmed days and keeping a reserve of power for emergency manoeuvring,
which is completely fine.

Working through the other parts, 5 knots, marine rated genset, 4kw,

4kw seems too low, I really think what ultimately becomes a proposition of battery is flat or unusable and now running on generator power, for which 4kw isnt going to be enough. The classic interpretation of an electric drive is that it has max torque at zero RPM and max hp at max RPM. It is generally becoming accepted that half the horsepower puts you in the zone for a hybrid power setup. The difference between say how a car works and this kind of application is that there are no downhill oceans or periods where you have to wait at a light.

Just to point out, that the above are the worked reasoning for why catamaran work out much better as a hybrid platform.
The motive power required is considerably less, the deck space offers a lot of area for solar support which is closing in on 40 watts a square foot.
Mono's are at a considerable disadvantage for area but better able to support the battery weight.

I think 5 knots seems like a workable ask but you wont get that on a standalone genset of 4kw, if the question is 'well what is' I think its closer to 10kw.
I think if its 'Uma like' and ends up with 4+ knots maximum (thats my memory of ver 1), or several hours at 2.5 knots which isnt enough to fight a tide its too marginal for me.
Marine rated typically means continuous power as well as inbuilt protections against corrosives etc. which are good, some would say necessary ambitions but which cost money.
cheers
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SVJourney

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Re: Daydreaming about a Saildrive
« Reply #10 on: August 12, 2020, 03:23:44 AM »
PeteW would be proud at my fledgling engineering skills, LOL, I just had to look this up.
If I assume that 5 knots requires 16Hp,(~1/3 throttle on the Beke?) then 20kVA required just to maintain. Plus I think there would be more inefficiencies due to power loss in the system described.  Plus more for charging and house loads.  Surprised me at how much juice would be required.

Determine the Power Factor of the device you are referring to. If you do not have the Power Factor in the device’s documentation, use 0.6 for a motor (60-percent rating)

Multiply the kVA rating by the Power Factor to determine the kilowatts. If the kVA rating was 20,  and the Power Factor was 60 percent, the equation would read 20 x 0.6 = 12 kW.

Change the kW answer to Watts by multiplying it by 1,000 (‘kilo’ is a prefix meaning ‘thousand,' so a kilowatt means a thousand Watts). In this case 12 kW x 1,000 = 12,000 Watts.

Convert the Watts to horsepower through dividing Watts by 746 (because 1 horsepower equals 746 Watts). In our example, 12,000 / 746 = 16.085, or about 16 horsepower. In summary, (kVA x PF x 1,000) / 746 = horsepower.
« Last Edit: August 12, 2020, 03:36:51 AM by SVJourney »
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ZULU40

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Re: Daydreaming about a Saildrive
« Reply #11 on: August 12, 2020, 08:07:18 AM »
hmmm, 16hp isnt a lot on a W40,
then again 5 knots isnt that big a push either
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SVJourney

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Re: Daydreaming about a Saildrive
« Reply #12 on: August 12, 2020, 01:11:22 PM »
Hmmm... Awesome chart.  Never seen that one before.  I downloaded it for future use.

I think the best thing to use would be average fuel consumption as that removes variables such as prop size.  We got 0.7 gals/hour on average on Journey, so If I am reading the chart right 20kVA should be more than adequate.
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ZULU40

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Re: Daydreaming about a Saildrive
« Reply #13 on: August 12, 2020, 03:32:45 PM »
you ought be able to run the throttle up to 5 knots, and read the RPM off the tach
then do the same for the same opposite relative bearing to take care of sea influences
the average RPM can be read off the table and give the HP

because its a middle order speed, once you have that, you can derive all kinds of data from it
because it follows that up to a point (max hull speed) you can use the cube root law for a factored speed
for example what the would the horsepower be to go to 0.8 x the speed which is 4 knots
the notation would look like 4 knots = 0.8 x 0.8 x 0.8 of power or 0.512 x hp derived for 5 knots

Ive always thought that a substantially smaller engine say 30hp would be successful and be running at a more efficient engine speed, and so use less fuel for the same boat speed
it is really only now that this kind of factoring becomes important

I get what you mean about variables such as prop dia and pitch, and of course that counts
but I think that in the lack of other data it is important to know
« Last Edit: August 12, 2020, 03:40:57 PM by ZULU40 »
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