Feathering Propellers
Sailnet Tayana List
I have a T37 with a 4-108. According
to my survey, the shaft is 1 1/4" and the Prop is 17RH11, 3 blade. I take
it that means 17X11 right hand. Anyway, we pulled the prop just after purchase
and installed an Autoprop. Our Autoprop's blade diameter is 17.13", and is
"self-pitching".
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In this
regard, has anyone tried the Autoprop? Because of its unique design, there is
little or no prop walk with the water being directed straight behind it. I do
not sell or market these props but the
difference mine made on my Tayana 47
was unbelievable with an added attraction of about a 20 to 25% savings in fuel
and the ability to run my engine at a slower speed for the same hull speed thru
the water. The fact that the prop will stop the boat in its own length either
forward or reverse from 6 knots also is an added bonus, especially as there is
no swing of the stern to either port or starboard. IT IS EXPENSIVE but every
one is designed, built and tested to the requirements of your boat and engine.
Brian Strutt T-47 September 1999
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Having the correct pitch allows the engine cylinder
pressure to be a minimum relative value for the horsepower developed.
For instance (as extreme examples), if too low a
pitch: lower rpm developed; hence lower horsepower.... and extremely high
cylinder pressure ('lugging' ) , blown head gaskets, bent piston connecting
rods, hammered mainshaft bearings, excessive engine wear, etc.
If too high a pitch: cavitating/eroding prop ,
scored cylinder walls, 'hammered' injectors and valve seats, excessive engine
wear.
Most 'steady state' reciprocating engines 'like' to
be run (long term) at near 75% of max. developed horsepower and at the 75% peak
of their 'power curve'.
I like to select pitch so that I get 75% optimum
rpm/horsepower output at the rated hull speed of the boat. Ever since Drs. Otto
and Diesel invented their engines, the value for long life vs. maximum output
has been around 75% rpm/horsepower output.
Look at the power curve 'optimum' value in your
engine manual, match/record/correct that value near the hull speed of the boat
and you optimize the whole system for economy, reliability, long life,
and extra power 'bursts' when you need it. For me its like religion, politics,
taking risks, etc.;... I like to be in the 'middle'.
The Autoprop tends to automatically adjust for the
'optimum' all along the engine power curve. (I just think they are outrageously
expensive, as I can almost do a whole engine rebuild for the price
of an Autoprop.).
Rich Hampel T-37
March 2000
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My
experience from talking to others is that if you have a well-pitched prop, a
Max-Prop will not gain you any speed and may, in fact, lose you a bit of speed.
The shapes of the blades are rather abrupt at the corners. As a feathering prop under sail, it provides 15% less drag than an
Autoprop. The Autoprop will almost
always give you a half-knot better speed and 10 to 20% better fuel specs. Since
the prices are similar, I recommend the Autoprop.
Wayne V-42 C/C RESTLESS December 2000
(The Max-prop
web site lists forward efficiency of a Max-prop as 96% of a 3-blade fixed
propeller)
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In my
humble opinion, nothing can tame the "drunken elephant", only sober
it up a little.
We put an Autoprop on "Tundra
Spirit" a T37 almost 4 years ago. We have a Perkins 4-108 and fluid drive
transmission. We love the prop, however am not sure we would go through it
again if we had to. We knew up front that the shaft would have to be shortened.
We were replacing the shaft anyway and just had it made shorter. We also knew
that the cutlass would have to be cut in 1/2 and after checking with the yard
manager where the boat was on the hard and getting his opinion that it would be
o.k., we cut the cutlass in half. As a side note, we check the cutlass each
year when she goes on the hard and after 3 1/2 years it is still good. Now,
after all of the above being completed and the prop installed, I swung the
rudder hard over, both port and starboard and the blades hit, so I had to shave
some (about 3/4 inch) off the rudder. Needless to say, I was not a happy
camper.
As stated above, we love the
Autoprop, however it was a real hassle installing it on our T-37. Other T-37's
may not have had the same problems. The only other thing that I might mention
is that the Autoprop folks suggest a shaft brake as the prop has a tendency to
rotate when you are sailing along at 5 1/2 to 6 knots. We do not have the brake
and it does rotate slowly at those speeds. The only thing I can not tell you is
how "Tundra Spirit" was before the Autoprop as I was never behind the
wheel with the old fixed prop. We do stop very well and she backs up without
much pull to one side. But I don't care what kind of prop you have (again, my
humble opinion), if you have a cross wind and a cut-away forefoot boat like the
T-37, the bow will blow to leeward and there is not much you can do about it
except have some long lines and help from the dock, or back into the wind until
you can turn. I will tell you that every time we pull the boat, we get a crowd
around our prop attempting to figure out how the thing can possibly work. It
does work !!
Bryan and Linda Biesanz T-37 "Tundra Spirit" July 2001
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This theme
might equally be called "Can a Tayana 37 Be Steered in Reverse?"
Perhaps someone can define the
benefits and disadvantages of an adjustable auto-vaning prop. I have heard
claims that it provides control in reverse for a full-keel boat such as the
T-37. I have also heard that it improves performance in reverse. Other comments
are that they are outrageously expensive for what they provide, and others say
that it is well worth the cost for the control they provide.
As far as controlling a
full/semi-full keel boat, my impression from the comments is that the benefits
are detectable, but marginal. Is this true?
Would you be better off investing the
money in a bow thruster? Will additional practice help overcome the problems of
steering in reverse?
I am still in a bit of tizzy when I
have to control the boat in reverse any place but in a wide-open lagoon with no
boats around, and lots of depth. But I can also say that after three years of
sailing our T-37, backing up gets slightly easier with practice and experience
- but oh so slowly! Most of the time I wish we had an end-tie. I usually
consider it a miracle that we managed to pull into our slip without disaster.
Backing out of the slip elicits a combination of silent prayers and audible
curses. Would an Auto-prop/Maxi-Prop suddenly make me into a skilled pilot? But
after 40 years of sailing, I can only recall two boats that I have ever sailed
that could back up in a reliable manner - a
Then there are the boats that really
can do both very well, like the
I rather like the strategy of
screaming "No Insurance". But too much of the time, there's no one
around to hear me shout.
regards, Harvey Karten July 2001
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On the
discussion of Autoprop verses Max-Prop and other units that carry a high price
I looked into Bill Maloney's suggestion and inquired about the
"Kiwiprop".
This is their response:
Thanks for your interest in our unit.
Attached is a copy of the standard warranty that comes with every unit and a
customer specification sheet we would ask you to complete were you to proceed
further.
We are familiar with the Perkins unit and have fitted a number of props to the
4.108 & 4.107 in each case with 2:1 reductions.
Assume you have the 2:1 box then you would need a 17" unit. Price would be US $ 1250 delivered DHL 5 ~ 10
days after dispatch.
The prop is certainly owner maintainable, with just 3 grease points on the
blades and 2, one fore one aft on the boss. Blade replacement if ever needed
takes just a minute with no need to remove the prop, in fact it can be done
underwater with a bottle.
We do not have agents in the
We can include a spare blade with the order if that gives some comfort, but
being 40 % glass reinforced Du Pont Zytel, they are very tough and have not
proved a problem in the power range we are dealing with.
Remember 3 blades = 33 % of the work per blade, a significant stress reduction
on a 2 bladed prop.
Please let me know if there are any other issues I may be able to answer for
you.
We are confident our unit will perform very well on your vessel.
Cheers, John Blundell Phone: + 64 9
5757 975, see www.kiwiprops.co.nz August 2001
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After taking a look through the Kiwi-prop web site I am considering fitting one of these props to my T37. I guess my concern is the strength of the blades when they come into contact with foreign objects. (we have a lot of Coconut's floating in the water as well as a lot of other debris. From what I could get from the Kiwiprop literature the blades are a lot thinner that the bronze Autoprop or Max-prop blades and they are made from a 40 % glass reinforced Du Pont Zytel . I have no idea what Zytel is. Do you know anyone who is using one of these props?
Regards, Phillip Brassington August
2001
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Hi Phillip,
I believe
zytol props are used on some of the larger outboard motors (according to
Kiwiprop’s). I don't know of anyone who is using the Kiwiprop so I can't be of
much help in that regard.
The purpose of my email relates to a
conversation I had with John Blundell of Kiwiprop. I asked him about pricing
and he quoted me NZ$100 per inch, hence a 17" should cost NZ$1700. This
converts to about US$714 using an exchange rate of 0.42. Obviously this
excludes freight and any import taxes.
I felt anyone contemplating buying a
prop should know the price quoted to me, as a local over the phone. One might
like to say that one of our members who lives in
I will try and find someone who has
had first hand experience with a Kiwiprop to comment.
Regards, Bill Moloney Covenant III #34 August
2001
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Help!
Have any of the T-37 owners on the
list fitted their boat with a feathering prop? I had Bold Venture fitted with a
new prop shaft with standard taper with the intent of buying an Autoprop and
putting it on in the water. I sent them a tracing of the aperture and shaft to
insure that I wouldn't have any problems and that it would not hit the rudder
or dead wood. I just heard back from them that an Autoprop won't work without
making modifications to the rudder, which I am not inclined to do, because I
don't want to haul again just yet. If any T-37 owners have fitted feathering
props, I would very much like to hear what they have and how satisfied they are
with it. I have a borrowed prop on the boat now so I will have to make a
decision soon as to whether to buy another fixed prop or feathering prop. I would prefer feathering if I can find one
that will work and can be installed in the water.
Regards,
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This is
disappointing to hear (that an Autoprop
won‘t fit easily on a T-37). I knew there were problems with the Max-prop
but had been told the Autoprop would work.
I am going
to look at one called Hydralign, www.hydralignprop.com/. They make a version that is billed as an
"aperture" version. The local prop shop says it will work on the
T-37.
John Lewis January 2003
See the Autostream, Hydralign, Slipstream, and Kiwi Feather props
at www.westbynorth.com
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I have a
Luke feathering prop on my T37. No modifications to the rudder or aperture were
required. See: http://www.peluke.com/
for info.
I like it. I had a new shaft machined to
replace the Chinese original. The Luke prop has a 17" diameter. Backing is
somewhat improved, although I have never thought the T-37 to be that bad in
backing up with the 18" x 12" 3-blade prop. The boat sails better
w/out the drag of the fixed, 3-blade prop. A negative is that the Luke prop
needs to be lubricated (greased) every 3-4 months. This entails having a diver
attach a grease gun to a screw-in port on the prop and pumping in some grease.
The Luke people are true
James W. Smiley Isle
of Palms, SC January 2003
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I have
family in
www.santotoday.com/gowestsf/feathering_prop.htm
Bill McMullen December 2004
Autostream Feathering Prop
|
We bought a new feathering
prop in Now I am glad I waited because it turns
out the these props are a lot cheaper in It has pitch adjustment for
both forward and reverse without disassembly which was an option on the Max
Prop for another grand. It seems to be well made and it is the top selling
feathering prop in Our boat performs so much better I am
amazed and I had high expectations. You may notice the blue ink on the prop.
It is a permanent marker that contains printers ink. It was given to us by
Kim on Rival Chief. It has kept the growth off the prop for 6 weeks so far
and got us out of |
Jim
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Subject:
Autoprop Maintenance Costs
The
Autoprop doesn't need greasing. My version of the prop has bearings that are
not only exposed to the water but are lubricated by it as well. I have heard
that some newer versions have sealed bearings.
My problem
is bearing race wear and it is not inexpensive to repair. When I got my prop, I motored over 7000 miles
in 3 years. The boat was never hauled. The prop worked fine. Now, that's a lot
of miles – probably much more than the prop was designed to go without
maintenance. When I overhauled the prop, the bearing tolerances were out of
spec (a sure sign that maintenance was needed) and most of the replaceable,
inner bearing races were in bad shape. The SS races had lost about half their
mass and started to get pretty thin. There were depressions in the races where
the bearings were located. The bearings no longer moved around the race but
seemed to rotate within each little depression. The outer races are machined
into the prop base itself and were still perfect. Overhaul was fairly easy. The
new races and bearings cost over $200. But still the prop worked fine. I am now
going to inspect every 2500 miles and plan on replacement at 5000 miles. I still like the prop a lot! And since my
fuel mileage is increased by about 20% that in itself probably pays for the
bearing and race overhaul kit.
Autoprop bearing races & assembly tool Ball-bearing
indentations in races
I
understand that using one on a T-37 poses clearance problems and requires a
slight reshaping of the rudder plus cutting the cutlass bearing housing. But there are at least two T-37’s out there
that use the Autoprop.
Wayne V-42 C/C RESTLESS December 2002
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When I
first got Southern Cross, she had a 17x12 prop, driven by a Yanmar 4JHE. This
was definitely too small, but probably the original. At 2600rpm, I got about
5.6kts. The engine would also easily exceed max RPM. I now have an Autoprop, 470-H5 (18.5 inches),
and at the same RPM I get about 6.5kts and it won't over rev anymore.
Paul s/v
Southern Cross V42-cc May 2005
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We have an
18" Max Prop on Magic Dragon. When we bought the boat, the previous owner
had decided it was under-propped and had adjusted the pitch up a notch, so we
were unable to make more than 3000 RPM with the Yanmar 4JHE. The stern would
squat severely and black smoke would boil out of the exhaust at that engine
speed.
I
repitched the prop back down last year and the engine seems much happier. I don't
remember exactly what the exact pitch measurements were/are. They're in my
logbook on the boat. I'll look this weekend and report back.
If you are
thinking of replacing the prop, I would definitely recommend ponying up the
extra $$ and going with the Max-Prop or Autoprop. More speed under sail, and
greatly improved backing ability.
Frank Timmons V42 Magic
Dragon May 2005
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From the folder on the FTP
site about Autoprop: ftp://tognews.com/AutoProp
RESTLESS: Tayana 42 Cutter
31,000#, 33 ft waterline
double ender
Perkins 4-108 (49 HP)
RPM Old (16X13 3-blade) AUTOPROP (18 1/4)
(29,500#-
displacement during test) (31,000#)
850
3.4 Kts
1300 ---- 5.0
1400 ---- 5.2
1500 4.8 5.4
1600 ---- 5.6
1700 5.5 estimated 5.9
1800 5.8 6.3
1900 6.1 6.4
2000 6.3 6.6
2100 6.5 6.8
2200 6.8 7.0
2300 6.9 7.2
2400 7.2 7.4
2600 7.6 7.8
Two Tayana 42’s: 5.8 Kts at 2300
RPM
(took another in tow - 92° day, 85° water temp)
Engine temp rose only 4° - towed for an hour.
Note: RESTLESS had original factory prop repitched 3 times from 18X10, to 17 1/2X11, to 17X12, & finally 16X13. Max speeds with 18X10 were 6.3 to 6.5 Kts. Cruise speed was 5.8 at around 2000 RPM.
CDR
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AutoProp
by
Since I have experimented with 4 or 5 variations of 3-blade props, a
discussion of my Autoprop is best preceded by a history of performance with other
propellers. I have a Tayana V-42 center
cockpit with a Perkins 4-108 and a
The
original factory prop was 18X10 and gave a max speed of 6.3 to 6.5 Kts. Cruise
speed was 5.8 at around 2000 RPM. I repitched it 3 times from 18X10 to 17
1/2X11 (no change in performance), 17X12 (picked up a few tenths of a knot and
lost a bit of "thrust" at low speed), & finally 16X13. The
smaller prop is a "speed" prop. That is, it is optimized for speed in
calm water. Speed went to 5.8 at 1800 RPM with about 6.3 Kts at 2000. Top speed
was 7.6 but the engine would immediately start to increase engine water temp.
Seven knots was sustainable at 2300 RPM. Low-end thrust suffered greatly with
the small prop. Acceleration was cut in half and the boat had a hard time
maintaining speed with any wave action on the bow. Moderate pitching (3 to 5
feet) resulted in 4 knots or less. But the boat cruised well in the ICW and
motor sailed well. The bottom line here is that a smaller prop with more pitch
equals better speed but less thrust. I tried another brand of 3-blade prop
(maybe a
Then I got an Autoprop. The Autoprop was easy to install on a V-42. It
is a 18 1/4 inch prop. I simply dove under the boat, placed it on the shaft and
tightened the nut (note: I had previously replaced my original Tayana shaft
with a standard taper
My
V-42 is a 1982. I have lived aboard for 17 years and cruised almost 42,000
miles. I have nearly 6000 hours on my Perkins so have lots of experience with
motoring and how the boat handles. I have cruised over 7500 NM's with the
Autoprop.
I
bought the Autoprop from Steve Armitage at RTL, Inc in
Performance is rather spectacular but with a few "quirks".
When first put on, I backed out of the slip and ran the throttle to 2000 RPM in
forward gear. Everybody aboard suspected that the prop had fallen off! The boat
was still backing and there was no "propwash" behind the boat. But
after I added a little more RPM, we noticed the boat responding slowly and away
we went. The boat accelerates slowly at first but then accelerates faster the
faster you go. This seems to be because the prop pitches infinitely based on
speed versus horsepower applied. It never, ever cavitates. It can't because
pitch varies widely and is always optimum. It also does not vibrate. When tied
in a slip, I have often applied cruise power (1800 RPM) and it takes 20 seconds
before the water behind the boat is disturbed at all. And then it is only
ripples, never bubbles, about 20 to 30 feet behind the boat. I mention this because one of my only
concerns with the prop are the wide-eyed dock attendants when I pull into a
transient marina. It takes almost 1 1/2
to 2 times the RPM you normally use to stop.
Plus there are no bubbles or prop wash.
The engine sounds very much like the captain has it in neutral. As a single-handed, I usually have to tell
the dock hands that I will stop the boat with the engine and then keep them
from reacting when they don't see the normal cues of burbling water from a boat
backing-down. Likewise when maneuvering
in marina fairways - lots of RPM and no prop wash. It gets people's attention... All a minor
inconvenience. Handling is improved.
"Propwalk" is almost gone completely.
The boat backs neither right nor left when the rudder is amidships. It will answer a port rudder in reverse but
never a starboard rudder due to the skeg-hung rudder. When a sharp turn is started for a
"back-and-fill" turn, the boats continues to swing nicely when
backing so I can turn the boat around much better than before. But a V-42 still will not back in a straight
line - ever! It will always back around
into the wind - even 2 or 3 knots of wind.
Once you realize this, you learn to take advantage of it.
Underway, the prop is amazing. In
general, it takes 200 to 300 less RPM to hold the same speed as before. But the engine is not loaded down. Quite the opposite, it is obvious from the
sound that it is very lightly loaded.
Hence the dramatic increase in fuel efficiency.
Tests have shown that you have at least 20% more thrust at full power if
you run aground. That may be because
full engine RPM is available if speed is zero (3600 RPM on my Perkins). My old
prop would only turn 2450 RPM if the boat was stopped.
Autoprop & lobster-trap guard on Tayana V-42 Autoprop on V-42
The
other anomaly is motorsailing at sea. When the seas are over 5 feet and from
the stern quadrant, the up-and-down motion of the boat can set up a very slight
vibration if RPM's are 1400 or below. This seems to be because the prop now has
to repitch to compensate for vertical velocities as well as horizontal. At 1500
RPM or above, the slight vibration is gone.
This is not unique to the Autoprop as I have experienced the same
phenomenon with a fixed prop. Also, the
prop spins slightly above 4 knots if in neutral. It doesn't spin when the boat
is shut down and left in gear. A shaft brake is not needed with a
Bottom line: a great prop! It’s like having an engine with 20% more
horsepower and an additional 20% more fuel when on a passage. I can now motor
all the way from