Alternative Propulsion Thread

[LtBrett]

David,

You had some specific questions about how to equilibrate electric and diesel engine ratings. Most of what Gideon wrote is spot on. I believe driveline losses are a bit less than the figures Gideon used, but the principle is correct. One other consideration: diesels are not run at full power. Cruising rpm is about 80% of full rpm, but cruising power is dependent on prop loading. Nigel Calder did a pretty good write up here:
Professional BoatBuilder - August/September 2007

Let me take a real world example to illustrate. A Lagoon 410 S2. It is powered by either 2 28hp sail drives or 2 12 hp electric motors. Cruise speed using the sail drives is about 80% of full throttle, or 22 hp. Assume a 10% driveline loss and you're down to 19hp at the propeller. Say propeller efficinecy is 40%, you're putting 7.6hp into forward motion. IIRC, that drives the 410 at 6.5 kts.

On to the electric. With proper wiring and cooling, 12 hp is available at the propeller at cruise (vs the 19 I theoretically calculated above). Remember almost 12 HP is also available to spin the propeller starting at 0 rpm's. This enables an electric motor to turn a much larger, slower, higher pitched propeller which is much more efficient. Say it is 60% efficient. You get 7.2hp pushing you forward, which is quite comparable to the diesel version. I've sailed on an electric 410 s2 and can tell you it's cruising speed was about 6kts, a little slower than the diesel sistership.

However, the 410 I was on couldn't make 12 hp per shaft. Breakers would trip if you went over 50A on either shaft (full power is attained at 64A), so I cruised at 43 or so amps or 8.3 hp per shaft.

So here's where the theory meets practical experience. A diesel 410S2 has 2x28hp sail drives and cruises at 6.5kts (reported to me by the Catamaran Co). The electric 410S2 I was on was generating a measured 8.3hp per shaft and was cruising at 6kts. There are ammeters at the helm, so I know exactly how much power was being used. In this case, it appears that 12hp electric motors are the rough equivalents of 28hp diesels at cruise, but were unable to drive the boat any faster due to limitations of wiring and cooling.

Brett

[anathema]

Also, since it appears that such smaller electric engines make the equivalents of larger diesel engines, this makes up or exceeds quite a bit of the conversion loss inherent in the diesel electric combo.

It seems some major advantages have possibly been overlooked as well.

One of the major ones it seems to me is the lack of a need to ever 'start' your engine in a pinch. You realize holy crap you are near a reef or a large breaking wave is coming towards you and you quickly need to turn the boat, you just push the throttles down and the electrics respond with 100 percent of torque instantly. Even times when you miss a tack or that other boat that has just drug anchor is almost upon you. The genset is only needed to recharge the propulsion bank on the longer trips (over 20-30nm as indicated by fastcat).

Also, while it hasn't been overlooked, I think having whatever solar you have room for, and a couple wind generators mounted all (nearly) constantly putting power back into your 'tank' seems like a great option, and depending on if shore power is metered or not, you may even get a flat-rate 'fill' from your marina. While there don't seem to be many boats using this in practice, I imagine a diesel electric set up similar to a locomotive etc would result in quite a bit less diesel being burnt, and overall better reliability since there would be far less hours on a diesel genset and the genset would be running at its proper load, rather than just starting a motor under almost no load to charge your batteries. This could also really help with reliability.

It seems like docking, anchoring, and other short-term general maneuvering would be entirely be absorbed by the batteries and your renewable sources and avoid the short run-time duration and startups that are such a major killer of diesel engines.

Once the tech is a bit more proven, and I am considering a repower of whatever boat I may own (not yet!) I would certainly take a system like this into account.

[LtBrett]

To add another shade to this thread, Anathema reminded me of how different it is to sail a hybrid. I question whether, according to the rules of the road, you are ever sailing. With engine power only a throttle bump away, the rules may consider you under power. On a regenerative system, you actually generate more if you bump the throttles forward. This creates an interesting dynamic. You get a push up waves and when turning, making tacking a snap. You can't turn the engines off either, as they generate power while sailing.

My wife likes her air conditioning and creature comforts, so I normally run a generator while underway. Because of the way I use my boat, a hybrid makes sense. In fact, once I figured out that the generator was going to be running anyway, I gave a little extra throttle to boost my sailing speed. The sailing purist in me resisted for a while, but the allure of getting to my destination sooner won out.

Brett

[anathema]

I speculate having an key in the 'off' position would clear you for colregs but if motorsailing I'm sure you would be considered a motor boat under the rules. Then again the darn things are so quiet, who is going to know

"No Mr admirality judge sir, I was just running my generator, the engines were off at all time, and I was clearly on starboard!"

[David M]

When the propeller is being used to propel a sailing vessel it is a power vessel under the COLREG's. Other than that, it is still a sail vessel.

Rule 3(c) The term "sailing vessel" means any vessel under sail provided that propelling machinery, if fitted, is not being used.


What the rule means by being "used" is that it is turning a propeller, and not recharging a battery etc. If an electric motor is turning a propeller then it is a power driven vessel.

The whole idea of the rule is that sailboats when not using their propeller are less maneuverable. Yes, there are exceptions where that is debatable but feel fortunate that in most situations, not all, you have rights over the "stink pots".

http://www.navcen.uscg.gov/mwv/navru...les/Rule03.htm

[Dedzaboy]

Apologies for going slightly off topic here, but after my post #81 on this thread the other day, Fastcat435 made a post where he said that if the electric drive system did not work out as planned, it had been previously agreed with his customers that he would retro-fit conventional diesel engines in place of the electric systems, at Fastcat's expense. To which I replied on post #83, "I wish them luck".
Fastcat's post however has now disappeared completely, making my reply #83 look slightly redundant! So where did Fastcat435's post go?

[fastcat435]

Hallo Anathema

I forgot to mention we use one masthead mounted Air Breeze 24 volts 200 watt wind generator together with the 4 solar panels to recharge the system when needed.
Gideon

[LtBrett]

David,

Let's not sidetrack into a debate on rules of the road. Suffice it to say that the courts have interpreted "in use" to mean an engine at idle, even if not in gear. This is certainly a grey area for hybrids.

Brett

[Dedzaboy]

I'm still puzzled by the post that disappeared as discussed in my post #96 above - can someone please confirm whether it was removed by Fastcat435 (is it possible for a "poster" to do this?) or by a moderator for some reason? Thanks.

[David M]

Originally Posted by LtBrett

David,

Let's not sidetrack into a debate on rules of the road. Suffice it to say that the courts have interpreted "in use" to mean an engine at idle, even if not in gear. This is certainly a grey area for hybrids.

Brett

I respectfully disagree.

What ruling? That's not what I learned. You are either turning the prop or you are not. "Machinery" can be a diesel engine or an electric motor.

Also, this far into a thread its usually okay to side track it a little.

[Hyprdrv]

When I took possession of EG she came with a black cone indicating sailing under power. I have yet to use it. How many of you use that indication when your motor sailing? How many use that cone if they don't lock there props in forward or reverse? Your props are still turning right?

Steve in Solomons

[s/v Jedi]

This rule is international and very simple: if you are underway using an engine/motor for propulsion, you are sailing under power, regardless of flying sails or not. If you are motorsailing, you must show the black cone during the day, and the "under-power" navlights at night (no tri-color allowed; steaming light, port, starboard and stern lights required).

So, if you are freewheeling your propeller, you are not under power. If your electric motor doesn't consume energy, you are not under power. If any court rules differently, they ruled wrong and an appeal is in order.

cheers,
Nick.

[LtBrett]

Ok, the sea lawyers are picking the nit vs. seeing the obvious. Current regenerative systems work best if you bump the throttle forward. Sounds "in use" to me.

The "in use" clause is inexact and findings of fault take into account how maneuverable a vessel is. Remember that is what is behind the rules. If a propulsion engine is idling, is not put into gear and a collision occurs, the "sailing vessel" captain will be very hard pressed to defend his (in)actions. Arguing precise definitions in the abstract leads you in circles.

Brett

[David M]

Now we are stepping outside of Rule 3(c) which is a different discussion. Yes, it is true that both parties can become the give way vessel but under different rules.

Its pretty cut and dried, you are either using your propeller to propel the boat through the water or you are not. A propeller being used as a device to charge a DC system is clearly not the meaning of Rule 3(c).

[cal40john]

From:
Rule 25: Sailing Vessels Underway and Vessels Under Oars


(e) A vessel proceeding under sail when also being propelled by machinery shall exhibit forward where it can best be seen a conical shape, apex downwards. A vessel of less than 12 meters in length is not required to exhibit this shape, but may do so.


Looks like the rules are pretty well nailed down to me, being propelled means engine pushing the boat to me. But the catch all phrase is everyone is supposed to do whatever is necessary to avoid a collision in the end. If your engine is running and you didn't attempt to avoid a collision by putting it in gear, you most certainly are going to share the blame.



I haven't seen anyone use the black cone except vessels similar to the Lady Washington. Most people have boats under 12 meters, so I wouldn't expect to see a lot of them anyway.


John