[PUP] Krogen 44 vs Nordhavn 43

Mike Schooley schooley at keyway.net
Thu May 12 00:06:05 EDT 2005


I developed a spreadsheet awhile back based on equations published by Dave
Gerr which I've used to check performance data provided by various Naval
Architects. My results were amazingly close to most NA (with one notable who
I won't name). For some unknown reason, my results, especially range
predictions, tend to be more conservative than most boat manufacturers.

I did a comparison of the predicted performance of the 65' version of
Portager (we are currently considering the 54' to 65' LOA range). First I
noted that the LOA * Beam product are about the same, indicating that the
internal area is comparable. Draft and Displacement comparable but Portager
has 37% less fuel than the Krogen 44 and 50% less than the Nordhavn 43 and
14.7% and 10% lower power. 

I calculated the fuel consumption rate versus speed at the fully loaded
weight and the light or dry weight and calculated the range based on these
fuel consumption rates, however these ranges are not realistic. The fully
loaded range is pessimistic because weight and fuel consumption decreases
with range and the light range is overly optimistic for the opposite reason.
Therefore I started at the fully loaded weight and determined the fuel
consumption rate and recomputed the weight on an hourly basis. I provided
the full, light and incremental ranges in comparison to the Krogen and
Nordhavn below. 

Feature		Krogen		Nordhavn		Portager
			44			43			65

LOA			49'			43'			65
LWL			40'11"		38'04"		63' 3.75"
Beam			15'6" (16'4")	14'10"		12' 0"
Draft			4'6"			4'11"			4'
6"
Height		23'3" (13'8")				10'
Disp (Full)		43,140		54,540
48,518(FL)/38,518(LT)
Cp.			.607			.59			.6
D/L			283			425
67.75
A/B			2.90			?			2.22
Water cap.		250			300			250
Water Heater	12			?
Fuel cap.		950			1200			600
Black Water		52			50			50

Main Engine		John Deer 6068	Lugger L668D	Steyr 144TI
			150hp @ 2300	142hp @		128 @ 3200
									+24
aux
Trans			Twin Disk 3.0:1	ZF w 220 3.79:1
Cooling		Heat Excgr		Keel Cooler		Hull plate
cooler
Exhaust		Wet			Dry			Dry
Propeller		4 blade		4 blade		CPP
			28x24.5		32x24
Fuel Day tank	none, pump		40 gal,		50 gal

Claimed Range					
								Full
Light	Incremental
5.2 knots					4,447		4472	5633
4650
6.0			4,950					3359	4231
3492
6.3						3557		3047	3838
3169
7.0			3,300					2480	3050
2562
7.1						2,667		2425	2975
2506
8.0			2,120					2041	2456
2160
9.0			1,390					1721	2084
1701
10.0								1411	1772
1470
11.0								1150	1465
1180
12.0								949	1217
996

Fuel used		855			1080			528
Reserve	Fuel	10%			10%			12%

Portager's incremental ranges are comparable to the "claimed" ranges for the
Nordhavn 43 and Krogen 44 with considerably less fuel. In addition, due to
her longer length at waterline (LWL), she can go faster than either Krogen
or Nordhavn with slightly less power.

I think this illustrated the advantages of a long and lean vessel over a
shorter wider boat.

I suggest that any boat you're considering, you double check the
manufacturers or designers math and then verify the performance with your
own sea trials before venturing offshore. I have seen a lot of overly
optimistic predictions with caveats like ranges are approximate, assuming no
wind or current, ... These caveats are designed to prevent you from
verifying or contradicting their calculations in the real world.

As someone else recommended, I would also insist of seeing the stability
curves and better yet confirming the design to complies with the IMO
offshore stability requirements.

Regards;
Mike Schooley
Designing "Portager" a transportable Passagemaker






More information about the Passagemaking-Under-Power mailing list