Conference unifix::sailing

    The Choy Lee 41 has a stuffing box.  We chartered one last year and
    were told that the Cap needs to be turned usually once a day when
    starting the engine.  The reason being not only does it reduce
    friction, but also help prevent water from leaking in at where the
    shaft goes out of the stern.  We also kept an eye on how much grease
    was in the cap to make sure there was grease to be squezed.

Why bother with a traditional stuffing box and grease when there is a 
much better product available? See Note 443.

    Less friction on a free-wheeling prop.

re .3:

Are you saying that a conventional stuffing box (with grease) has less 
friction than a Lasdrop or are you saying that a free-wheeling propeller 
has less drag than a locked propeller?

If the former, while I have no data, having used both I strongly suspect 
that a Lasdrop has considerably less friction than a (greased daily) 
conventional stuffing box. The Lasdrop is certainly much less 
maintenance and related bother.

If the latter, this is a matter of great controversy. When Practical 
Sailor discussed the issue, the conclusion was that locked is usually 
lower drag than free-wheeling (and is certainly quieter) and that the 
drag from a two-blade propeller is much less than the drag from a 
three-bladed one.

                            Some data on drag:
    
   When I chartered a 43' Beneteau that had a large  three-bladed propeller
I was asked by the charter rep. to lock the prop. ( put transmission in rev. )
when under sail. I asked, WHY ! He said..
   1: reduces noise
   2: reduces wear & tear on the stuffing box and transmission.
I said , " that will slow the boat down " , he said, " only a very little."
    
SO I put it to the test. Sailed with the propeller free-wheeling for short
time frame ( 2-3 min.), noted speed, locked prop. noted speed and noise level.
Did this several times and found that the boat WOULD reduce speed and REDUCE
NOISE level in the locked mode. BUT the speed loss wasn't all that bad 
( unless your a racer ), lost about .4 knot when running at 6.5 to 7 knots.
THE noise level was worth the .4 knot, ( to me ), as when it was free-wheeling
there was this RUMBLE-RUMBLE noise. 
This drag effect will be different for each boat , propeller size/type and
as Alan said in .4, some may even have less drag with the propeller locked. 
    
   This is just what I found to be true with this particular boat & prop.
I did leave it in the locked mode except to run the test because I liked the
quiet ( or should I say, "didn't like the RUMBLE_RUMBLE" ) and because of
the reduced wear on the transmission & stuffing box. I would have run in the
locked mode even if not asked to do so by the charter co. and by chance had 
found the reduced noise level in locked mode.
    
   I have chartered Hunter 34's and Cal 33's in the past and don't  recall
any RUMBLE from there propeller shaft , may-be they don't free-wheel when
the engine is not running, bay-be some kind of braking asmb. ?? May-be
some one could add to this note about the Hunter 34's or Cal 33's. May-be
the Beneteua is the odd-ball in that the prop free-wheels and makes all the
noise. ?????
    
    That's my .2 knots worth. ( or is that $0.02 )
    Hank
      

A word of warning: My engine installation uses a Walters V-drive that is 
sea water cooled, with the cooling water pumped through the V-drive by
the engine sea water pump. If the propeller is allowed to free wheel,
the V-drive gears are turning and creating heat but there is no cooling 
water flow. I was warned by Westerbeke that the heat generated is enough 
to possibly damage the V-drive. I've never experimented to see how hot 
the V-drive would get for the reason in -.1: I don't like the noise and 
wear from a free wheeling propeller.

    This note is in reference to Note 1503 (a PropCharger).  I had been
    talking to this person about my prop charger and he mentioned the
    grease cup.  The are only three transmissions (that I am aware of) that
    can free wheel with any damage; they are: Hurth, B/W and the Yanmar. 
    Because of the prop charger I would like to get as little friction as
    possible.
    
    Also, as mentioned in Note 1503, at lessd than six knots the output
    drops drastically.  One of the reasons for this is the drag in the
    alternator.  Any suggestions on a "pot" to reduce the field current?  I
    believe that this would give a lower output per revalution but would
    induce less drag on the prop shaft thus maybe (?) increasing the rpm.
    
    
    Jay

re .last:

I don't think that stuffing box friction is limiting the output of your 
PropCharger. 

The output current of an alternator (for constant speed) increases with 
increasing field current. As output current goes up, the horsepower
required to drive the alternator goes up. Remember that 746 watts = 1
hp. A 100A alternator @14.4V is supplying 1.93 horsepower and, with 
mechanical losses, might require 2.5 hp to drive. 40A would be about 
0.77 hp. 

Reducing the field current with a variable resistor would reduce both 
the output current and the power required to turn the alternator. Thus, 
if you do reduce the field current, you might well get some charging 
from the PropCharger at lower boat speeds. I don't know how the power 
required to turn a propeller varies with rpm. The power available from 
the free-wheeling propeller shaft may fall faster than linearly with 
decreasing rpm. Anyone know?

    I considered a Lasdrop for Second Wind this spring.  I noted in the
    literature some warnings regarding freezing and since I leave the boat
    in year round and we do get some hard freezes in the Chesapeake, I
    stayed with the stuffing box.
    
    Any mention of this in the Practical Sailor article?