Lloyd Sumpter wrote:

On Sat, 25 Oct 2003 18:07:58 +0000, Jere Lull wrote:


Overall cost savings don't much enter into this sort of purchase.
Cheapest by far would be a fixed prop. It would take us a very long time
to consume $1500 worth of fuel, much less save that much on fuel. (In
1067 hours, we consumed 341 gallons.)

Agreed!
I can see some non-monetary reasons for going to a feathering or folding
prop, but can't see the advantage of the auto-prop.


The AutoProp's an unusual beast. After some discussions this past
season, I might consider an AutoProp for a trawler or other
mostly-powered boat: the blades keep a constant *relative* pitch, giving
better thrust and keeping the engine better loaded at reduced RPMs.

I'm now torn between the 3-blade fixed Campbell Sailor and the AutostreaM.
I like the AutostreaM's stainless-steel:

I like the *idea* of SS as well, but our SS shaft gets considerably more
growth than the bronze blade, even at the hub. And bronze seems more
suited to hard knocks. I've been thinking of switching back to a bronze
shaft....

I'd also like the feathering advantage, although I was jokingly adding up
all the "fasters" I could get: feathering gets me 1-2 knots faster, the
Sail Guy said a new headsail would get me at least a knot, clean bottom
would give me an extra 1/2 to 1 knot...and I was going 6 knots in an 8
knot breeze. So add that all up, and I'd be going about 9-10 knots!


They apply at different speeds. Once the wind's up and you're pressing
against hull speed, you're wasting power intentionally. I honestly have
noticed the speed bump up a half to full knot when I locked the blades
at 4-5 knots. The bottom makes the most difference at lower speeds, as
can the sail. Adding all of the effects together can make the difference
between 2-3 knots and not being able to move at all. THAT can surprise
neighboring boats.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/