[PCW] fuel economy

[Robert Deering]

John,

If 7-8 knots is a satisfactory speed for you, I doubt that a cat is your
animal of choice.  While it's not easy to directly compare a Manta 44 with
your trawler, the fact is that cats have more wetted surface for a given
length than do monohulls.  More wetted surface equals more 'friction', which
equals more fuel consumption.

But as speed increases, wetted surface resistance becomes a smaller and
smaller fraction of a displacement hull's resistance, while wave-making
resistance becomes the dominant component.  That's where cats quickly take
over.

What's your trawler's fuel economy at 10 kts?  At 12 kts?  14?  No point
asking any further, is there?  The Manta will be able to travel at those
speeds, and still at a reasonable fuel consumption rate.

So if 7 kts works for you, the added cost of a cat might not be worth it,
though the stability, improved ride, and unsinkable aspects may have value
in themselves.

Bob Deering
Juneau, Alaska