SailNet Community banner
1 - 20 of 21 Posts

·
Registered
Herreshoff/Vaitses Meadowlark
Joined
·
242 Posts
Reaction score
63
Discussion Starter · #1 ·
I am refitting a rather odd boat, a Vaitses/Herreshoff Meadowlark. 37' long, 8' beam, 20" draft, two masts and leeboards.
Boat Water Naval architecture Vehicle Watercraft

As originally designed she had two 5hp gasoline engines pushing two props. Somewhere along the line these were replaced with a single 27hp Yanmar diesel pushing a single offset prop.
Plant Watercraft Tire Vehicle Plant community


The diesel hasn't been well maintained, and with only one prop she doesn't handle well at low speeds under power, so I've been thinking about adding a pair of electrics. Both Torqeedo and EPropulsion make pod drives that would serve - with the shaft and cutlass bearing strut removed, either of these pods could be placed to put the pod's props where the existing prop and it's missing twin are and would have been.

But I've been thinking that perhaps a pair of electric outboards might do. EPropulsion's Navy 3.0 or 6.0 Evo, or Torqeedo's 3.0 or 6.0 R.

The advantages I see:
  • easier to repair or replace
  • can be lifted out of the water when under sail (when I'm not using the regen to power the batteries)
  • can be lifted out of the water at anchor or at dock, to reduce marine growth
  • can be steered, making for even more directional control at low speeds than simply have two props
  • can be installed, and tried out, without having to remove the existing diesel

The only major shortcoming I can see is that it would making mounting a windvane off the stern very complicated, but given the boat's stern configuration that'd have been true even if I don't hang engines off the back.

Are there any other possible issues I should be aware of? Between pod drives and outboards, that is. High price and limited range are very much relevant to the choice between diesel and electric, and I may we'll stick with diesel, but assuming I decide on electric, why should I choose pods over outboards?
 

·
Registered
Herreshoff/Vaitses Meadowlark
Joined
·
242 Posts
Reaction score
63
Discussion Starter · #3 ·
IMHO, the aesthetic of outboards hanging off the transom would spoil the beauty of that amazing boat.
That is a legitimate complaint. Meadowlarks were designed as simple, unassuming boats, free of glitz and brightwork. But that doesn't mean they have to be ugly.
 

·
Registered
Joined
·
163 Posts
Reaction score
49
I think that the pods would be more in keeping with the design, depending on the financial costs. Outboards can be fairly ineffective in waves and wind and are vulnerable to damage if a collision aft occurs. (Like a dragging anchor?) Also keeping batteries charged becomes problematic. The simplicity of the design becomes more complicated. As they say "Oh my God!" What to do? I might try to find a good old Yanmar 2gm15 or keep the existing one going. The cost of new equipment can easily exceed the resale value of the boat if that is an issue.
 

·
Registered
Herreshoff/Vaitses Meadowlark
Joined
·
242 Posts
Reaction score
63
Discussion Starter · #5 ·
Electrics under any circumstances raise issues of limited range, source of charging, etc.

OTOH, internal combustion of any type are loud, messy, and require a great deal more maintenance.

But those have been argued to death. I'm asking about pods vs outboards, assuming the decision to go electric has already been made.

Disadvantages of outboards:
  • More likely to be damaged in a collision (but less likely in a grounding?)
  • Ugly

Others?
 

·
Freedom isn't free
Joined
·
3,303 Posts
Reaction score
1,244
Outboards are notoriously bad in a chop, even VERY long shaft outboards, still have the issue.
Inboards (of any kind) will generally have a prop that is further under the boat and more likely to remain in water in a chop.

Except for very large inboard electrics, the power is usually more limited in HP per lb.

I wholeheartly agree though that electrics are generally more simple to maintain assuming charging options have been sorted.

I nicely cared for disel though can be a very reliable option, but I know you have already decided on electric, its just a matter now of inboard/pod versus outboard.
 

·
Registered
Herreshoff/Vaitses Meadowlark
Joined
·
242 Posts
Reaction score
63
Discussion Starter · #7 ·
A nicely cared for disel though can be a very reliable option, but I know you have already decided on electric, its just a matter now of inboard/pod versus outboard.
If I trusted the diesel had been maintained properly, over the years, I'd not be considering a change. But I know it hasn't been. After a couple of thousand in repairs, it's working now, but I'm less than confident in it.

I'm not sure whether I can live with the limitations of electric, either. That's part of what makes electric outboards attractive. I can put them in place without removing the diesel, and even after I do remove the diesel, swapping in gas outboards would be simple, compared to replacing pod drives.
 

·
Registered
Herreshoff/Vaitses Meadowlark
Joined
·
242 Posts
Reaction score
63
Discussion Starter · #9 ·
I suppose then the question is: How do you plan to use the boat? If you have specific goals the path is easier to see.
The goal is to use it as a retirement live-aboard, along the US East Coast, Gulf Coast, and excursions to the Bahamas, perhaps Dominican Republic, Puerto Rico, and the Virgins.
 

·
Registered
Joined
·
182 Posts
Reaction score
128
US East Coast, Gulf Coast, and excursions to the Bahamas, perhaps Dominican Republic, Puerto Rico, and the Virgins.
Going one way you will have the current and would probably get away with (lightweight, inexpensive ) electric systems.
Going the other way (against the current) you will need oomph. That means internal combustion diesel or gasoline.
A 27 hp Yanmar has oomph, so to me it seems that you already have the answer to your power problem.

When you say "with only one prop she doesn't handle well at low speeds under power, ",
what are we talking about?
And would an under powered electric system (even with two props) be better?

Questions worth pondering. No?

PS. Very nice boat

gary
 

·
Registered
Joined
·
163 Posts
Reaction score
49
I have no experience with electric motor drives in boats but my neighbor's catamaran next to me has pods, one in each hull and he loves them. Maybe folks with catamarans would be the ones to talk too. To be honest, I don't think that there is anything inexpensive on that boat, if that is an issue. I did get a look at the installation and it looks very good to me.
 

·
Registered
Herreshoff/Vaitses Meadowlark
Joined
·
242 Posts
Reaction score
63
Discussion Starter · #15 ·
If you’re refitting, is a single pod in the center of the boat a possibility?
On my boat? No.

She has a shallow but very long keel running along the centerline. This is part of why she steers so poorly at low speeds, given that she has only a single offset prop.
Tire Wheel Plant Hood Automotive tire
 

·
Registered
Joined
·
54 Posts
Reaction score
8
My electric (Oceanvolt) motor uses a sail drive lower end which works really well.
What type of boat?
Where do you sail?
How far can you be from the marina or home in a dead calm and be sure you can get home?

I looked at a Nimble Kodiak with an electric Motor. The owner kept it on a trailer in his back yard. He sailed it in Lake Tahoe. He said it was great, low maintenance.

I plan to sail/motor 1200 miles this summer along the southern US coast. As far as I know, I dont think my boat, a Nimble Artic, has enough space for solar to keep the battery charged enough for more than sporadic use of the motor.

Looking at this

I cant think where to put the battery on my boat.
 

·
Registered
Joined
·
20 Posts
Reaction score
14
It is all about the propeller. Which ever drive you choose, it needs a propeller with the right diameter, rpm and pitch to give the thrust needed for the yachts hull speed. Choose the propeller first and then select the drive that fits.
 

·
Registered
Herreshoff/Vaitses Meadowlark
Joined
·
242 Posts
Reaction score
63
Discussion Starter · #18 · (Edited)
It is all about the propeller. Which ever drive you choose, it needs a propeller with the right diameter, rpm and pitch to give the thrust needed for the yachts hull speed. Choose the propeller first and then select the drive that fits.
Some numbers:
  • ePropulsion Navy 3.0 Evo outboard - 3kW, 2300 max RPM, 10.2" 2-blade prop
  • ePropulsion Navy 6.0 Evo outboard - 6kW, 1500 max RPM, 12.6" 3-blade prop
  • ePropulsion Pod Drive 3.0 Evo - 3kW, 2300 max RPM, 10.2" 2-blade prop
  • ePropulsion Pod Drive 6.0 Evo - 6kW, 1500 max RPM, 12.6" 3-blade prop
  • Torqeedo Cruise 3.0 outboard - 3kW, 1100 max RPM, 11.8" 3-blade prop
  • Torqeedo Cruise 6.0 outboard - 6kW, 1130 max RPM, 12.6" 3-blade prop
  • Torqeedo Cruise 3.0 FP Pod Drive - 3kW, 1100 max RPM, 11.8" 3-blade prop
  • Torqeedo Cruise 6.0 FP Pod Drive - 6kW, 1130 max RPM, 12.2" 5-blade prop
The props on the Torqeedos are interchangeable. The 12.2" 5-blade prop from the 6.0 pod drive is optimized for low-speed displacement boats, and will fit on the 6.0 outboard.
 

·
Registered
Joined
·
20 Posts
Reaction score
14
Some numbers:
  • EPropulsion Navy 3.0 Evo outboard - 3kW, 2300 max RPM, 10.2" 2-blade prop
  • ePropulsion Navy 6.0 Evo outboard - 6kW, 1500 max RPM, 12.6" 3-blade prop
  • ePropulsion Pod Drive 3.0 Evo - 3kW, 2300 max RPM, 10.2" 2-blade prop
  • ePropulsion Pod Drive 6.0 Evo - 6kW, 1500 max RPM, 12.6" 3-blade prop
  • Torqeedo Cruise 3.0 outboard - 3kW, 1100 max RPM, 11.8" 3-blade prop
  • Torqeedo Cruise 6.0 outboard - 6kW, 1130 max RPM, 12.6" 3-blade prop
  • Torqeedo Cruise 3.0 FP Pod Drive - 3kW, 1100 max RPM, 11.8" 3-blade prop
  • Torqeedo Cruise 6.0 FP Pod Drive - 6kW, 1130 max RPM, 12.2" 5-blade prop
The props on the Torqeedos are in interchangeable. the 12.2" 5-blade prop from the 6.0 pod drive is optimized for low-speed displacement boats, and will fit on the 6.0 outboard.
I am an engineer who has carried out electric conversion tests for yacht owners. When we tank tested electric motors we found that approx 30% of the diesel HP was required by an electric motor to drive the diesel's propeller at the same rpm. We were using 220V motors. When I have looked at other conversion options I have noticed that suppliers usually plan to put in 50% of the diesel HP in their electric conversion. That maybe because of caution or because lower voltage motors were being used.

The low speed propeller you have identified needs a bit more detail. Is its operating speed near your hull speed. Ideally about 80% of your hull speed.

There are several replies in this thread which warn against using outboards because they do not perform well into a choppy sea. My experience is that sail drives and shaft drives have the same problem. I have always thought this was because the thrust line of the propeller is no longer horizontal. I cannot remember whether or not outboards were worse.

If I were planning your project I would use an outboard for the same reasons you have mentioned. A 6 Kw outboard using the 12 inch 5 blade prop in flat water and little wind should get you to about 75% of the speed your Yanmar achieves. Take the yacht to the max speed the outboard can achieve and set that as the best operating speed. Using more of the outboard power will most likely just cavitate the propeller.

Electric works best if you choose a single operating speed and set up for that. The speed should be using at least 95% of the electric power available. Current measurement is the best way to check that. The speed has to be less than hull speed.

My experience is that the only way to work out this problem is to try things. Theories and formulas only get you half way there. Would love to hear your results.
 

·
Registered
Herreshoff/Vaitses Meadowlark
Joined
·
242 Posts
Reaction score
63
Discussion Starter · #20 ·
Power requirements are so non-linear, and battery life and range increases so much at lower speeds, I don't see hull speed as being my normal cruising speed.

I'd want enough power to achieve hull speed against chop or a head wind, in case of emergency, but I can't see myself carrying enough battery to do it very long.

The math predicts a smooth curve - lower power means lower speed and longer range. But it's almost certain that there will be certain power levels that are more efficient.

I don't, though, think that anyone could predict where they will be. I'll need to experiment.
 
1 - 20 of 21 Posts
Top