I've used Robert Beebe's calculations for a 73,144 lb DD462 to determine HP requirements and they are considerably higher than George Buehler states on his Diesel Duck website. I've compared the figures and charted them on an Excel chart (which I tried, but can't post here.) At a V/L of 1.00 (6.8 Knots) Bueler lists 13.3 HP while Beebe's calculations indicate 36 HP required. At 1.25 V/L (8.5 Knots) Buehler lists 43.6 HP while Beebe's calculations indicate 95 HP.

I've also taken these HP figures and charted fuel usage in GPM against them. I also charted Deere's figures. I then took the info that "Nomad" posted in his Jan. 2 reply to the topic "powering". His experience in light to moderate conditions falls right on the curve for Beebe's calculations, not Buehler's. I'd be happy to share these charts. Just email me at dklueck@mac.com.

I have an Excel spreadsheet template I bought that concurs with Beebe's calculations. I'd be happy to share my results with anyone who emails me at dklueck@mac.com.

George prefaces his charts with dead calm conditions

I know that George's charts are for calm conditions, but I think that would be kind of like designing an airplane to fly with no passengers. Or desining automobiles the same way and then advertising the great fuel economy.

Oh well, I guess that in engineering school I was taught to design for real world conditions and with a safety factor.

Wouldn't it be great if we alswys had calm conditions?

So how much does a DD 462 need in worst case conditions, and given that it is also driving 2 big alternators at perhaps 15 Hp loaded.

I recall Bill saying that the JD reps insisted that hull 1 was overpowered with the 150 Hp engine, and now he is using 135Hp.

As Hugh points out, lower Hp rating = longer duty cycle.

Robert

I think you'll find when cruising you go with conditions, and in that case, the figures are pretty close. He makes that clear if you read his writing.

Ben

I am a bit confused.
So if I fit for calm conditions at 13.3 or even a whopping 43.6 Hp and all hell breaks loose what to do?

What is the collective wisdom for the amount of power under worst case conditions, accounting for parasitic draw, plus reserve, while keeping the duty rating numerically lowest?

I would trust Bill and the Deere reps on this. For a comparison the 47 Nordhavn displaces 85k lbs. (loaded) and has a lugger L1066T rated at 173hp. Beign the company they are I would expect Nordhavn to be very conservative on hp. In other words they probably have a larger safety margin than you really need.

I have seen a watson that weighs close to 200k lbs with only a 250hp engine in it.

If the Deere engine in question (130hp that Bill is reccomending) is the M1 rated engine at 130hp, then it really is designed to use this full hp. Other manufactures will quote the max hp even though the engine may not be reccomended to use the engine at that rating for 24 hours a day.

I would think 130 to 150 is a pretty good number. Especially if the number is a good 24 hour duty number not just something you can use for a few hours.

To some degree I think this is a marketing issue as in a boat this big people expect to see a 6cylinder not a 4.

What I'm really thinking about is whether I want a normally aspirated 6 or a turbo 4. The NA version won't do as well on fuel consumption but will be more reliable. Either way I'm looking at the 130-150hp range. Still I know Bill is reviewing this and hasn't made his reccomendation on the engine for the sedan yet.


Hugh

The engine Hp rating is further complicated if one needs or wants a Tier II compliant engine. In my case, the keel was laid prior to Tier II and I suspect that it is not an issue in Thailand anyway. I do not care about the tiny bit of pollution from my boat, and am more concerned with fuel consumption and reliability.

It seems that Tier II, while not a common rail, is electronically controlled while the non-cert engine is a mechanical governor.

While one would expect the electronic engine to be more economical on fuel, I cannot find fuel consumption specs nor power curves and would be very interested if there is a lower fuel use with the electronic engine.
It appears that the Tier II requires higher RPM to achieve the same torque and Hp rating as the mechanical engine. Is the fuel use advangate offset by having to spin the engine faster?

I am sure that the KISS factor wil be raised in favour of the mechanical engine, and no doubt this might be seen as an issue, however cars have had ECU's for decades and is pretty reliable. Having said this, you are knackered if it goes TU, and I wonder if the electronic engine has a limp home mode?
Also how waterproof is the brain box when a hose starts spraying water all over, and where is it located?

Will electronic control give lower fuel consumption if running at a steady speed. I can see how in a car it would be better, but do not know about a steady load and speed.

Presumably the Tier II is more expensive?
Does this complicate the electrical system, and/or does one need a isolated battery for the ECU?

Note that Tier II no longer offers the 150 Hp x M4 rating.
Tier II Specs
Rating Torque ft/lbs HP
M3 352 @ 1800 RPM 135 @ 2600 RPM
M2 330 @ 1700 RPM 121 @ 2500 RPM
M1 310 @ 1600 RPM 107 @ 2400 RPM

Non-Cert mechanical engine
M4 375 @ 1800 RPM 150 @ 2600 RPM
M3 339 @ 1500 RPM 135 @ 2500 RPM
M2 304 @ 1500 RPM 120 @ 2400 RPM
M1 274 @ 1500 RPM 105 @ 2300 RPM

So many questions and so little knowledge to make a decision. Any ideas on which engine, rating, and HP?

Robert

Well it looks like the results are in.

Bill is going with a 6068SFM engine for my sedan.

While I remain interested in the electronic version, as this is a single engine boat, reliability takes precendence over any other issue. It is a good choice.

Hugh

Hugh,
Are you getting the 6068SFM or the -TFM ? The SFM is, I believe, electronically controlled while the TFM is mechanically controlled. I'm sure you'll be fine with either. I think the 6 cylinder is a wise move.
Good luck,
John

John,

I don't know for sure as Bill has not clarified yet. For the non-certified engines the SFM is an electronically controled variable fuel pump and the TFM is a mechanical governor. For the Tier II engines both the SFM and TFM are electronic. According to the Deere website.

I'll find out and post.

Just checked my e-mail to/from Bill and it looks like it is the TFM.

Now I'm just curious to find out what prop is being used as the engine change, I think, would necesitate a prop change to take advantage of the change in torque.



Hugh

I hear this a lot. I don't figure them, a computer does. It does it on formulas based on Skene's Elements of Yacht Design, which was considered the standard. I don't know where Beebe got his from. The figures I quote are, as I always state, based on O adverse conditions. That means exactly that; if you're going into any breeze or tide they aren't accurate.
The DUCK concept which far to many people are forgetting by the way, is a fuel efficient offshore cruising power boat. It is meant to go WITH the conditions, not against them. Just like a cruising sailboat although in our case, when the wind fails, you can head up. IF you use the boat in the way the concept calls for, I think you'll fnd my stated figures are pretty close.
Yes, of corse you can push things. Tt's easy and it's tempting. Listening to a bit higher RPM and seeing a bit higher wave at the bow is nice. But if you look at your fuel flow meter you'll see that extra 1/2 knot or whatever (and it ain't much more) is costing you a noticably greater amount of fuel. But that's your choice and not the requirement,IF you plan on using her as she was designed to be used for. In fact, part of that concept is the "modified dhow" sailplan. But I'm trough arguing that one!
Please go look at the Troller Yacht Book if you disagree with me, because it spells out the concept in pretty good detail! You can still disagree of course. But at least you might then understand what the DUCK concept is capable of, which is far more esoteric than what many people seem able to see.

Hey George,

Glad to hear you weigh in on this. In terms of the "concept", couldn't agree with you more. I look at "Power Cruising" now and then (though not sure why) and it seems like everyone is striving to have their own mini-QEII. But, at the end of the day, I think the question that still lurks even for those of us that think we get the concept but still have not pulled the trigger on a power plant is ; that accepting your numbers as calm conditions, completely appropriate, if you make modest assumptions that you might be driving a substantial alternator, hydraulics (not QEII stuff, but the essentials), etc, is there enough reserve built in to claw your way off a lee shore or, if you have to, beat into a gale for safe harbor and know you have enough punch (even if you don't have the stomach) to do it? There are enough ducks now that have the track record to answer this. My sense from keeping my ear to the ground is that a boat like the D-48 might be efficient but a tad underpowered at 100 HP (continuous) and over powered at 150. Does that sound right?

Greg

quote:

Originally posted by Greg:
Hey George,

Glad to hear you weigh in on this. In terms of the "concept", couldn't agree with you more. I look at "Power Cruising" now and then (though not sure why) and it seems like everyone is striving to have their own mini-QEII. But, at the end of the day, I think the question that still lurks even for those of us that think we get the concept but still have not pulled the trigger on a power plant is ; that accepting your numbers as calm conditions, completely appropriate, if you make modest assumptions that you might be driving a substantial alternator, hydraulics (not QEII stuff, but the essentials), etc, is there enough reserve built in to claw your way off a lee shore or, if you have to, beat into a gale for safe harbor and know you have enough punch (even if you don't have the stomach) to do it? There are enough ducks now that have the track record to answer this. My sense from keeping my ear to the ground is that a boat like the D-48 might be efficient but a tad underpowered at 100 HP (continuous) and over powered at 150. Does that sound right?

Greg

I don’t want to get to involved with this chat group because it doesn’t seem appropriate. However, I enjoy reading it and I suppose I should answer this.
The only thing other than fire that is really any danger when cruising is the land. People who “push on” are the ones who get hurt. Entering a strange harbor at night is a classic case.
There is NO excuse to ever, especially in a powerboat like these, to be in a position where you need to “claw off a lee shore.” And no, while even a 48 with 100 HP will be able to at the least hold position in a gale, I personally would NEVER try to “beat into a gale for a safe harbor” because that’s how you get nailed. I’d heave to (another reason for the Modified Dhow sail plan) and wait. Once I spent 4 days hove to about 10 miles outside of San Diego. It was very rough and trying to sail in that stuff was no fun. It was much better to simply batten down and lay about inside reading. That’s what cruising is, or at least USED to be. It seems today all the emphasis is “man against the sea” bs
I spent two years in an enginelss sailboat leisurely (and slowly) going from SF to Puerto Vallarta to Hawaii. I was never in any trouble other than boredom because I anticipated and never pushed into spots where there was no way out. The few tight places I had to go I always hove to and waited for things to be in my favor, and even then always had the anchor ready to drop instantly.
Yes, using the HP to run a big generator or hydraulic system will likely cost some fuel. But the real issue with fuel used is speed. The old sailboat cruiser’s DREAM was to average 100 miles/day, or 4 knots. That’s considered slow today but, if you quiz people who say they do better, you’ll see all (the ones I’ve talked to anyway) motor sail if the speed “drops” to that, and rarely are they actually going in the direction they really want to. I’ve had days on end when the ocean looked like a lake and I “sailed” under 10 miles in 24 hrs. I’ve even drifted backwards more than once. That’s what cruising under sail is like and people who say there aren’t periods like that have never cruised under real sail.
So that’s the background to the “Troller Yacht” idea. A speed of say 5 knots over several days is a DREAM to a cruising sailor, especially in the right direction. Pushing it to 6 is too exciting to even hope for. 462 #1 on the trip to the Philippines apparently burnt 5 gals/hr but they were going over 8 knots. That extra 1.5 to 2 knots probably more than doubled the fuel.
Anyway, that’s what I think for what it’s worth!

George

There seems to be a lot of angsting over this issue of powering and how much is enough. If you read Beebe's books carefully you'll see that he adds 50% (I think it was 50 or nearabouts) for real world, less than ideal conditions. So if you compare Beebe's figures and George's you are not comparing apples and apples. Opinions vary as to how much you should add to the base line, calm weather figures with most experienced people I know ranging from 25% to 50% tops.It also depends a lot on whether the boat is a power only cruiser or a crusing yacht or motorsailer. I find the cruising/sailing boat owner is less worried about engine power because they have other options.

A good book on Diesel Engine Maintenance by Nigel Calder covers this subject in clear precise terms.
This really boils down to the preference and experience of the owner - if you are the kind of cruiser who has a heart attack about being slowed down by a knot or 2 by some bad weather then you'll probably power the hell out of your boat. Maybe the real question you should ask youself is whether this is the right kind of boat for me?
MP

Has anyone had any experience with multiple power sources hydraulically connected? As an example, does it make any sense to have two 75% hp engines on the same hydraulic circuit driving the same hydraulic motor connected to a single drive shaft/prop? Any comments? Pros/Cons?