T&T: SHAFT PACKING 1

[Milt Baker]

At the risk of beating a dead horse, let me take one more swing
at this poor critter with an eye towards providing what I hope may be
helpful info for those trying to sort this out.  (Rich, you can stop
reading here! ;-))

Operationally speaking, the principal difference between GFO packing and
plain old flax packing is that the GFO stuff is very slippery which means
friction is a small fraction of what's experienced with conventional flax 
packing. Even when flax packing gets old and loses much of its elasticity, 
tightening down on the packing gland is all it takes to stop or seriously
attenuate the inward flow of water.

Tightening down on the packing gland which has conventional flax packing, 
however, creates more friction, and more friction equals more heat.  That's 
not much of a problem where Marin uses his boat in the Pacific NW, but here 
in Florida, the Bahamas and Caribbean, not to mention the Mediterranean, we 
frequently see water temperatures in excess of 80 deg F--sometimes we see 90 
deg F waters.  When that happens, less friction and less heat is a good thing.

When I'm cruising in Maine in 55-degree water, I check the stuffing box once 
per underway day and that's it because even if there's a delta of 30 degrees 
from ambient water temp, the stuffing box is very happy at 85 degrees ("cool 
enough to hold your hand on"), but with the same delta of 30 degrees from 
ambient and 80 degree water, suddenly the stuffing box is borderline at
115 degrees.  That's a little too warm to comfortable hold one's hand on
for a long period.  Even warmer water or more friction can increase the 
temperature significantly.

What I'm saying Marin, is that what may work in Bellingham doesn't 
necessarily work equally well in substantially warmer waters.  Based on 
your experience, plain old flax packing seems great for where you are, but
something with less friction and a smaller delta from ambient temperature
makes a lot more sense for those of us who cruise closer to the equator.

Just one more opinion,

--Milt Baker, Nordhavn 47 Bluewater, Fort Lauderdale 




Marin wrote:

I'm not going to say that flax is as good or better than GFO.  Obviously
a lot of people seem to have better longevity and performance with GFO.
As I said, we were prepared to switch to that when we had the shaft work
done last year.  But based on our experience with our boat, as well as
the yard's recommendation which was based on their experience over many
years, and talking to other boaters we know in the marina, we could see
no reason to change over, particularly when the change would have cost
more.  So we'll see how the flax we had put in last year holds up.  So
far, the performance is identical to what we had from 1998 to 2008----
no drips when stationary, minimal drips when running, and the shaft logs
run cold.