cruising speed of a CD 330

[rodcapedory]

Does anyone know the approx. cruising speed for a CD 330. I was asked on a brokerage form and don't know.

thanks

Rod Croes
GEMS 330
1986

[Ralph H]

Under power with Universal 5424 @ ~80%, burning .34 gal/hour in light wind/waves about 5 knots. I generally use 4.5 knots for route planning to be conservative. I have a CDI 3 blade feathering prop. Prop and bottom condition have an impact ... I keep Liberty in the water year around and repaint the bottom every two years. I use a diver to clean in off years. I'm not sure how representative this is of other CD330s.
Hope this helps.

[Jim Evans]

The 33 and the 330 have the same hull, and I agree with Ralph's numbers. I use the same haul out and diver schedule on the Chesapeake as Ralph does. Cleanliness of the prop is a big factor on speed; my Yanmar 3GM30F will push me along at 5.5 knots with a clean prop at 2800 rpm, and about 4.5 knots (or even less) with a crusty prop that's been through a season without cleaning.

[rodcapedory]

Thanks Ralph and Jim. All the best.

Rod
GEMS
1986 CD 330

[Paul D.]

I concur with the responses. Maybe it is because Femme is in fresh water and has low or no fouling, but I generally make 5.5kts at 2000rpm with the Universal 5424 unless against moderate waves or more. When plotting a course I plan on 5kts if motoring in calm seas. I use 5kts planning for sailing too with any sort of wind but usually make better time.

When chartering back in the day, the Chartermaster called a Island Packet 32 we took out once a 5kt boat, which we found completely true. It just wouldn't go above that speed even with some wind. Perhaps it's my bias or maybe even blind love but I cannot say that about the CD33! She just does better so I say she's a 6 knot boat.

In fact, every sailor with any sort of experience has each commented that she went faster than expected. Being the captain of a 30 year old boat, with equally vintage sails and 4 of 5 electronics aboard now made redundant, I'll take the compliment for her.

[Frank Vernet]

Concur with 5kts with a Universal 5424 turning at 2000rpm.

I also concur that the condition of the blade makes a big difference. I was getting 3.5kts this summer and it felt like I was dragging a sea anchor. I dove on the prop and scrapped off a thick layer of barnacles. Back to 5kts.

[MFC]

Under power with Universal 5424 @ ~80%, burning .34 gal/hour in light wind/waves about 5 knots. I generally use 4.5 knots for route planning to be conservative. I have a CDI 3 blade feathering prop. Prop and bottom condition have an impact ... I keep Liberty in the water year around and repaint the bottom every two years. I use a diver to clean in off years. I'm not sure how representative this is of other CD330s.
Hope this helps.

Ralph -
Do I read this correctly? You are running at approximately 2200 RPM (80% of 2800) and getting about 3 hours to the gallon? Is that what you meant or are you using about 3/4 of a gallon per hour (which is about my experience at 2200RPM). Very curious.
Thanks.
Matt

[Oswego John]

Ralph H wrote:

"Under power with Universal 5424 @ ~80%, burning .34 gal/hour in light wind/waves about 5 knots."

The way that I read this was that Ralph was burning a tad over a third of a gallon per hour. After running three hours, he used a little over one gallon. .34 gal/hr x 3 hrs = 1.02 gal.

O J

[Duncan]

Ralph -
Do I read this correctly? You are running at approximately 2200 RPM (80% of 2800) and getting about 3 hours to the gallon? Is that what you meant or are you using about 3/4 of a gallon per hour (which is about my experience at 2200RPM). Very curious.
Thanks.
Matt

It certainly can't be three hours to the gallon, and it should be more like one hour to the gallon:

A rough figure for diesel engine fuel consumption is 1/3 of a pound per hour per horsepower produced.

The Universal 5424 is rated for 28 hp max, so 80% implies about 22 hp at "cruise".

This 22 hp produced, times 1/3 pound per hour per hp, comes out to a total consumption of around 7 pounds an hour. Since diesel weighs 7.1 pounds per gallon, this is about a gallon an hour.

Some manufacturers publish graphs for power and fuel consumption, so there may be more exact figures available for the engine model in question. The "1/3 pound per hour per hp" efficiency constant is going to be pretty close for most diesel engines, though.

[Ralph H]

From our latest cruise:
Engine hours at refill: 1259.6 - 11 gallons to fill
Engine hours at start: 1232.6 with full tank
Fuel consumption per engine hour = .407 gal/hr
Cruising engine speed: 2250

I fill the tank to the same mark (F) on the guage each time. This cruise was 0.07 above my average, not sure why, but not near .75 to 1 gal/hr.

If you see something I'm doing wrong, please let me know.

thanks,
Ralph

[MFC]

Thanks Ralph. I knew what I read, I just wanted to confirm that you meant what you said.

Unfortuantely, I am using closer to 3/4 of gallon an hour at 2200. So, it is not what you are doing wrong but what you are doing *right* and I am doing wrong . . ..

Not sure there is a short term fix to this issue but I will try backing off a bit further and see what results I get.

Thanks again.

Matt

[Tom Keevil]

We generally run at 2000 rpm, which pushes us a bit over 5 knots, and we use about 0.4 gal/hr. Fuel consumption rises steeply after that.

Of course, we have no idea if our tachometer is accurate. Are we possibly all comparing differently calibrated tachs?

[Duncan]

We generally run at 2000 rpm, which pushes us a bit over 5 knots, and we use about 0.4 gal/hr. Fuel consumption rises steeply after that.

Of course, we have no idea if our tachometer is accurate. Are we possibly all comparing differently calibrated tachs?

Based on your consistent readings of 0.4 gallons (i.e. 2.85 lbs) per hour, I suspect the rpm readings, as well.

Your fuel consumption figures imply that your engines are only making about 8.5 hp (2.85 lbs divided by 0.3333lbs/hp/hr). This is consistent with my little YSE8, which burns about 0.25 gal/hr to make an estimated 5 hp at "cruise" speed.

I don't recall the formulas, but I suspect that it may be true that this power is all it takes to drive your hull at 5 knots. On the other hand, a tach reading of 2200 would imply that you are making 20+ hp, and would therefore be burning more like a gallon an hour.

Hard to believe that the tach could be so far out, but something just doesn't add up otherwise.

( ps I did double-check the 1/3 pound/hour/hp, and it seems to add up. It will be close to this for most diesels. For instance, the Volkswagen/Audi car diesels are reported to run at exactly this figure. Another way of expressing this is to say "one gallon per hour for every 20 hp")

[Ralph H]

Tom,
Could be, I've never calibrated mine. It looks like we're getting nearly the same fuel consumption rate at ~5kt cruise though. If you have a low cost means of checking the tach calibration, please let me know and I'll check.
thanks,
Ralph

[Paul D.]

I too use .5 gallons/hr for planning and have figured that as an average rate. But unless we are motoring against more than moderate wind and seas I run at 2000 rpm's. I'll go up to 2200 in those conditions. I've never confirmed the accuracy of the tach but I am a better sailor than Motörhead so I generally focus on the fun of sailing- when everything's working!

I'd be curious the difference fresh water makes on efficiency density wise. We never have issues with barnacles on our props up here. And our bottoms generally look good with little effort, at least the ones on our boats.