Well put Dave K.
H.
Larry, the one most common thread between cruisers that I have noted is they are very independent thinkers. We look at ideas and ways that people do things, then either copy or adapt them to our own needs and desires. Yes, no one likes drag, everyone wants to go as fast as the wind and our experience will allow us to go. Doing the drag tests on 3 different boats gave me three different answers, as the boat weight and length went up the drag went down, it was still there but down. The lighter the boat and the difference between a full keel and skeg keel made a difference also. In the lightest boat, a 28 Pearson, the drag from the test pull was about .6 kts, in the heaviest boat it made about a .2 kts difference.. .. (all under power as the wind is to variable in most cases) This is still subjective, it depends on what you as an individual want to lose, or give up. For what it's worth, I wouldn't have a folding or feathering prop and not just because of initial cost, maintenance and the ability to reverse mean more to me than the drag. I know many would disagree with me, and I don't mind that a bit, to each his(or her) own.... Dave K
--- On Thu, 3/11/10, gramplarry <pfister.l@verizon. net> wrote:
From: gramplarry <pfister.l@verizon. net>
Subject: [Electric Boats] Re: propellers
To: electricboats@ yahoogroups. com
Date: Thursday, March 11, 2010, 11:35 AM
chris, dave, myles.
cris you mention 200 watts per hour and being nirvana and 100 wats per hour as being acceptable. There is no free lunch so what drag sacrifice would be acceptable to you. e.g.1/4 to 1/2 knot?
I have to agree with Myles. Originally i thought that only racers would be interested in feathering or folding propellers. The around the world cruisers i have talked with(The company has a booth at the Annapolis boat show every year)quickly sorted that out for me. Cruisers have even more interest in low drag. A 1 knot difference can add an extra day or two to a week long passage. It makes sense if they can average say 5 kt then a 1 kt drag will add 20% more time to the passage.
But is there a break even point for watts vs speed? and what about the comfort and convience factor. Many cruisers enforce very strict power conservation rules while making a passage. how much is it worth to relax those rules?
larry
|
|
No comments:
Post a Comment