开云体育

Jim,<br> Consider using a "Timing Belt" it will
offer the positive drive of a chain with the quite
operation of a belt. These are used in industry all the
time and offer long life with no maintence and they
don't slip. I have used hundreds of them to drive
printing presses. Look in your phone book under "power
transmission equiptment" or look for a "Browning" distributer
under bearing houses and they will help you out. They
are not as cheap as "V" belts but they will give you
the best of both worlds.

I'm sorry for the confusion. I had planned on a
12x10 two blade prop. Then I found a 3 blade 12x6,
(which I didn't notice had a 7/8" bore). I ended up
using a 12x8 two blade sail boat prop. I have a 2:1
reduction on my motor. I need to check my rpm this year. I
started out with a chain drive (2:1 reduction also). It
worked great, but it made to much noise. When I went to
belt drive I think the extra friction cut my speed
down a little. <br><br>I hope to find time this winter
to write a short story about how I went about my
conversion. I have a few more picture I want to post some
time soon also.<br><br>Thanks for all the various info
you guys are posting here at the club.<br><br>Jim
"Zinger"

What prop did you settle on. In your original message (#20) you mentioned that you were using a 12 x 10 prop. In you Photos you mention a 12 x 6 three bladed prop.

hope you people like what you see, and if you do check out links on my Yahoo messenger profile and you will get more info on me and my hobby.

I have an Autohelm ST30 knotlog installed. I
cruise at 4 knots and max at 5.5 knots. I only have 2
speeds right now. I run at 18 volts or 36 volts. Low
speed range is 8-9 hours. Hi speed is 4-4.5 hours. I
haven't run a constant 8 hours yet. I have done 5 or 6
one hour cruises with lots of power to spare, without
having to recharge. By the way, I am using an extra #27
gel-cell just for my electronics and motor control
circuits. That way I don't waste any of my main battery
power for radio, controlls, speedo, bilge pump, etc.

Does anyone have any first hand expierence with
using a Kort nozzle on electric boats. My research seem
to indicate that they may help especialy when
dealing with the low speed that electric boats tend to
run. One manufacturer of an electric outboard claims a
50% increase effecency in prop performance with speed
up to 10 to 12 knots. I know that they will increase
the thrust especialy at lower speeds and are used on
tug boats. How much increase in speed can we expect??
It might be an area where we can all benifit if it
will "lighten the load" on the motor. If the data that
I have seen about tug boats (which is where they
appear to be most widly used) can be can be carried over
to the electric propulsion of small boats it should
result in a BIG increase in effency especialy at low
propeler speed. If you can take a prop which is 40%
effecient at say 4 knots and even increase its effency by
30% it should result in a decrease in motor loads
which would greatly extend range.

Hey Rus,<br> Can you send me an email at
natherholt@... when you have a moment? I am interested in
getting some more detail on your motor system. it sounds
like it would work well for my current project of
converting my sailboat. Thanks and I'll look forward to
hearing from you. Bill

Hello Larry, I looked at the pictures "great
job"...<br>One direction you may take to improve the efficiency
(cruise speed and range) of you launch is to look into a
more efficient propeller once you determine the right
size and pitch relative to shaft speed. Most of the
large Prop/Wheel manufactures (Mich. and Nat.) design
props to be spun faster then electric installations
"normally" provide. 1400 rpm for a 14~16 prop is just
breaking into the 60% eff range, below this <1000 rpm
eff. can drop to 40%. (this means you only get 40% of
your power to the prop). The standard recommendation
in the e-boat circles (and diesels) is to turn a
larger prop slower to gain efficiency. For this to work
out though you need a prop designed to be turned
slower to start out with. Sailboat props, steam powered
props, small diesel work boat props are (some not all)
designed to be turned at lower rpm's, much closer to the
proportions needed for electric power. But, the first thing
you need to know is: Is the motor
over-loaded,un-loaded or right on for amp draw and rpm (motor
amps).<br>Holiday Greetings and Regards,<br>Joe

Thanks for initiating the discussion on hull
speed and, conveniently, using my launch as the
example! Before building the boat I performed much the
same calculation and arrived at much the same result
as to theoretical maximum hull speed. The designer
specified the speed as "up to 6 knots". The hull speed is
actually just about 6 kts.<br><br>I have always
understood, however, that "hull speed" was not quite as
inflexible as you describe. My various displacement boats
over the years have always been able to exceed hull
speedeven the ones I rowed!<br><br>I think of it more like
riding a bike. While youre on the flats it takes more
power to go faster but the application of that power
generally results in a fairly rewarding addition of
speed.<br><br>When a boat hits its hull speed its like encountering
a hill on the bike. (Its actually very much like
this since the displacement hull is in effect trying
to climb the hill of its own bow wave as it tries to
increase speed, right?) So as you try to peddle the bike
faster AND uphill it takes quite a bit more effort for
even a little increase in speed. And for our
displacement hull its as if the hill gets steeper with each
little increment of speed you try to add. At some point
you are working VERY, VERY hard to go even just a
little bit faster. Just aint worth it.<br><br>This
particular thread started because of my stating that I had
installed a prop that was less than ideal (I think) and was
wondering what effect a change of prop or shaft rpm would
have on performance. But, like most of us electric
boaters, the goal is not so much faster as FARTHER. If a
change of prop/shaft speed could convert my most
efficient cruising speed from 4 kts. to 4.4 kts with the
same amp draw, then Ive added significant miles to my
range.<br><br>There are some photos of the boat at:
<a href= target=new></a> which were taken at the launch in Aug. I have
some later photos with the boat underway, under power,
but, unfortunately, I need to find a friend who can
scan them for me. <br><br>Larry

hi doug<br><br>you wrote on sept. 5, and i just
signed on and saw your note today, dec. 28, so it may be
too late. but here goes.<br>first, i wouldn't
consider buying a planing hull like the lund if you aren't
going to go fast. you are right about it not being
especially efficient. i would also worry about an aluminum
hull with electric motors and electric system, since
aluminum is notoriously prone to electrolysis problems,
aggravated by electricity. <br>the two minn kota rt70s
sounds okay though--but i'm vastly prejudiced--i'm using
2 rt70s to power my 22-foot catalina sailboat, so i
think (naturally!)that's a good choice.<br>next, i take
issue with the idea--and i see it everywhere and don't
begin to understand it--that electric motors are
"underpowered." electric motors have what they have. they can't
be underpowered--or overpowered or any other
powered. a 10 horsepower engine/motor is a 10 horsepower
engine/motor, period, whether it's gas, diesel, electric,
nuclear , napththa, or wood-burning steam-driven. a
horsepower is a horsepower, a watt is a watt, and
pounds/thrust is pounds/thrust. <br>electric motors aren't
(can't be) "underpowered"--but there's frequently a lot
of debate over how to rate them alongside combustion
engines using horsepower as their measurement. the rule
of thumb nowadays is that about 60 to 70 lbs. thrust
equals about one horsepower. so your rt70 minnkotas are
about 1 horse each. <br>whatever boat you pick, you'll
have to decide whether it can be powered by a pair of
one horsepower engines, whether they be electric or
gas or whatever. if the answer is yes, then
everything's cool. if the answer is no, then it's not the
"fault" of the electric motors--you couldn't push that
boat with a pair of 1hp outboards, either, then.<br>i
was going to suggest a pontoon-type boat until i saw
that you want to cruise around CT and RI in
naragansett and the sound presumably--areas where you get
some wind, some tide, and some pretty good chop. it
sounds like you need a reasonably good sea boat--which a
pontoon boat isn't, and which a small aluminum planing
hull isn't, either--like a sailboat hull or catboat
like the previous response suggested. having made THAT
decision, THEN you can think about powering her--and if you
are going out into the sound and the n-bay, you do
need a fair amount of reserve power and reserve
battery capacity for days when the wind and tide are
against you. you said you intended "coastal cruising" in
new england, and to me that can only mean a fairly
rugged, fairy seaworthy boat.

hi, r.c.<br>sorry for the long delay in
responding (if it's not already too late) but i just
recently came upon this club and saw your query.<br>one
reason there's little info to be found is that your
question poses too many variables. specifically, there's
no way to answer "how much speed would you get from
such-and-such a motor" even knowing you have a 16-foot canoe.
How much weight is in the canoe? what does it weigh?
<br>the other way to answer is that your canoe won't go
faster than about 4.5 to 5 knots no matter how big the
engine is, so to some extent the upper end doesn't
matter--the only question is, how much (minimum) power do i
need, and what kind of range will i get.<br>i could do
a bunch of calculations to give you an answer, but
it would be razzle-dazzle. the really short answer
is, any electric trolling motor of 35 lbs. or more
will do just fine. nobody can give you a range
estimate--the only way to tell will be to determine what load
the canoe will carry, then test it--by going until
the battery conks out. this is almost purely a
function of speed--if you run at top speed, the battery
will give you maybe 90 minutes to 2 hours or so--call
it 8 to 10 miles. but this is a foolish answer
because it would be foolish to run this (or any kind of)
motor at flank speed. you are much better off running
at a comfortable cruising speed (or else getting a
much stronger motor and running it at 3/4 speed). this
being so, your battery (if you are using only one)
might last 5-8 hours, who knows. (which battery would
you use? they are all as different as motors. it's
like asking when your car will run out of gas. well,
how big is your gas tank? 10 gallon? 20 gallon?).
once again, how much weight in the boat? what speed?
until you can supply all the parts to the equation,
nobody can tote up the answer. hence, "it all depends,"
frustrating as that might be.<br>the other way to do it would
be just to take it on faith. will an electric motor
do the job? hell, yes. what size? biggest you can
afford (on the theory that it's better to run a bigger
motor at 1/2 speed--and have some reserve) than to run
a small motor at 3/4 or 7/8 speed--and have very
little "extra" oomph going against wind or tide). <br>i
don't know how you're going to load the canoe, but all
else being equal, i'd prefer two batteries instead of
one, if loading allows it. get so-called "marine"
deepcycle batteries; never, ever use regular car starting
batteries for trolling motors.<br>if you are going anywhere
near salt or even brackish water, i'd seriously
consider one of the stainless steel/saltwater model
trolling motors. they are--naturally--more expensive, but
worth the extra in saltwater corrosion
resistance.<br>minn kota and motorguide are both good brand names and
are readily available at lots of places.<br>no matter
which brand or model you buy, make sure ity has an
"optimizer" pulse system in the controller--this is basically
a "chopper" that converts the d.c. current flow
into 20,000 to 30,000 pulses--and appreciably extends
the range and battery life--read the propaganda that
comes with the motor. minn kota's usually come with it;
some models and manufacturers sell the optimizer as an
extra; if so, get one.<br>you asked if there is a
smaller motor than a 30-pounder. there may well be, but i
think you're headed down the wrong road if you are
thinking minimum instead of maximum--and if you are trying
to save 10 bucks here and there, you're also heading
in the wrong direction. did you buy the least
expensive canoe? the least expensive, thinnest, k-mart
brand hiking boots? instead of a good quality tent, are
you packing a bedsheet? if you've already bought good
quality stuff, don't suddenly start scrimping on your
motor and batteries. buy up, not down.

Hi Larry, and merry xmas.<br><br>The hull speed
for your new launch is (theoretically) 1.34 times the
square root of the waterline length. But this is purely
a theoretical maximum (there's considerable debate
over whether it can ever be exceeded, and under what
conditions, but all of that discussion is irrelevant to your
boat). I assume the 23' measurement is overall length,
not waterline length, which is the number we really
need. Since she's a fantail, let's assume (for argument
and round numbers' sake) that her waterline length is
exatctly 20 feet. The square root of 20 is 4.47 near
enough. Multiplied by 1.34-that is 5.98 knots, or a
little better than 6 miles an hour. This means that with
a 10,000 horsepower nuclear powerplant on board,
your launch still can't go any faster than 6 knots. As
a practical matter, naval architects know that any
given hull shape will need to use a multiplier somewhat
below 1.34. In the case of a well-designed fantail, I
know for a fact that number would be around 1.2 due to
the efficiency of the hull. So your boat has a true
maximum hull speed of about 1.2 times 4.47, which is
about 5.36 knots. In the case of a round-bottom
displacement boat like a launch, this means there is no power
on earth that will move it through the water faster
than 5.36 knots.<br>What it also means is that you
need to perform all further hull/speed and horsepower
calculations using the 1.2 x 4.47 calculation as your base
number. Since not even a 900-horse jet engine will move
her faster than 5.36 knots, there is no sense in
using any value higher than 5.36 for hull speed. (To
some extent this whole discussion is faintly
ridiculous, since we're working in hundreths of a knot, which
is well beyond any measurable tolerance we'd be
working with in the real world, but out of habit we all
tend to work in two or three decimal places, as though
they meant something. Tenths would be more realistic.
But I always work to 2 decimal places out of
habit.)<br>You may need to know where and why the 1.2 is
important--it is the estimated coefficient of efficiency of
hulls shaped about like fantail launches, and is a
derivative number that comes from measurements and averages
of lots of boats. Yeah, you'll get a little argument
here and there; one naval architect will argue 1.18
and another will say 1.24 if she's really long and
flat...and yadda yadda yadda--this is where my footnote
about 2 decimal places comes in. The number 1.2 is
reasonable and close, and we're dealing with ballpark stuff
here anyway--nothing that can ever be measured and
calculated before. The only way to derive an actual number
is by actual testing--throw a 100-horse outboard on
her, go as fast as possible, measure the absolute
maximum flat-out speed, and work the calculation backward
(divide that speed by 4.47 to get your actual 1.2 (or
whatever) multiplier.<br>The "cruising speed" of your
launch is something else again. Everybody picks a
different multiplier for this, but it tends to go around 70
or 75 percent of maximum hull speed. This would be
the speed at which you and your boat can go
"comfortably" (whatever that is) before horsepower consumption
starts to rise on a graph. It is the speed you want to
cruise at without using maximum gas/electric/coal or
whatever. The number you pick is important, because it is
really the number you need to perform "ideal" or
"optimum" horsepower, shaft speed, power consumption, prop
diameter, etc., etc. calculations. In your case, I'd pick a
number around 4 knots as ideal cruising speed, and work
with that. I'd size the prop, figure shaft speed,
power usage, etc., all off of this base number--4
knots. Ya want 4.1? Fine. 3.9? Great. The presumption
is, this is the speed you'll be using the vast
majority of the time, so the engineering should conform to
it. There's no sense engineering your system to go
5.8 knots--you'll never see it happen, so why bother?
<br>Good luck. (Hey, post us all a picture.)

Thanks joe for the information on the low cost
Tachs. I have several good expensive one for my real
life business but its nice to know that I can tell
someone about the low cost alternative. I think everyone
should have one if they are doing this type of a
conversion.<br> I'll look forward to getting the data from you on
the various type of props, hull speeds and shaft
speed. It will be invaluable for testing my model. <br>
So far I am getting results between 63-80 %
effencies in the best of casses most of the problem seem to
be in teh motors being used. Most of the motors
being used for boat conversion are of a traction motor
design and are more suitable for forklift and electric
golf carts and not t all suitable for use as a boats
propulsion system I am getting information from some
industrial Servo motor munufacturers and expect that I can
get effencies up to the 90% catagory.<br><br>Thanks
again for you help i'll be looking for the data. You
can e-mail me at Donaldbaer@...

Hi Donaldbear and all,<br>You asked in an earlier
post if you could have a copy of some Motor/prop data
for your spreadsheet. I'm going to be doing some
motor, prop and gear testing in a month or so. If your
interested I'll send you a copy of the data I collect. The
data will have e-meter output, shaft rpm, and boat
speed. Along with the data I can give you the specs. for
the equipment used so you have a baseline. (I have a
friend with tons of props I can swap out until I find
the right one) BTW, a very accurate and cheap Tach
can be had at "Wal-Mart ($19.97). It's sold as a
"BELL" Bike Speed computer but it works great as a RPM
sensor. It uses a Hall effect sensor and magnet for
sensing and with two magnets is good to +/- 4 RPM (0~1660
rpm). After mounting(on prop shaft), to use, read the
speed of the display and convert it to RPM using (RPM =
speed read from Bell bike spedo*5280*12/62.9/60/2). The
"62.9" is for the 27" wheel setting of the Speedo and
the "two" is for two magnets. You can record your
boat speed and tach readings and convert it later.
Using a tach of some kind to get shaft revs will give
better data to work out the gearing with..<br>Enjoy the
Holidays<br>Joe Peek<br>ECB<br>P.S. in you speadsheet how high an
eff. are you seeing with the data collected so
far...like hp in, hp out or % eff?

I arrived home last night to find the latest
issue of the Electric Boat Journal in my mail. It is a
32 page double issue, jammed with information and
stories about electric boating. Many thanks to Ken
Matthews for devoting two of those pages to the Electric
Boat Club (p. 18-19). This should help get the word
out that this is a great place to exchange ideas and
information. From recent conversations I can see that our
group is both serious and knowledgeable. What a
fantastic resource!

Merry Christmass and may you have many more.

Larry<br> Your absolutly correct about the speed
for you hull. I was only picking 8 knots as an
example. For your boat we should use a number around 5.8
knots or say 6 knots. The calculations are based on
Gerr's propeller handbook and you are also correct the
hull configuration is a major factor. That is where
some educated guess work is first used since the
"SLIP" of the prop is a factor of you hull shape and the
screws RPM for a given speed. But in your case it we can
determine the slip. We know that a 12 pitch prop will try
to move throught the water at a specific speed
depending on it speed of rotation the difference between
the threoretical speed and the actual speed is the
slip. If you could measure the shaft speed at a given
known speed say 6 knots we could then calculate the
SLIP. If you don't have a tachomoter then you can get a
good estimate by measuring the motor armature voltage.
we know from the manufacturer that at 36 volts the
motor should be turning at 2100 RPM's and the
relationship is linear at 24 volts the speed will be about
1400 RPM's This is not exact and it will vary with
load but it is within 5 %. If WE know the slip then we
can calculate the ideal gear ratio to get the motor
to max speed at your most effecient speed.

Hi Bill, I remember living aboard during
winter-time on the bay. I lived in Deal, Md. for a few years.
(Ice eaters outside and glycol in the bilge)<br><br>
You may not need to mess with belts(and lose eff
=miles)The lower unit is a gear reduction(you'll have to
check it out) and saildrives used higher reductions
then the standard outboard...could be 3 or 4:1 which
would be a good start for an electric
converision.<br><br>When you do the Speed/Drag you can enter the data into
a sperad sheet like excel and graph out the curve.
What happens is the drag curve increases along with
speed (more or less together)until you hit the hulls
displacement limited speed, then speed flattens and drag goes
up like a rocket. Use the calculation to find hp
needed at a given speed...It's fun to do really, but
maybe not in the cold....<br>Joe

Thanks for the Idea about a hull drag test. I may
try that as soon as it warms up here on the
Chesapeake. I'll post any data so that other can follow along
with the repower story. Should be fun.<br>FYI
currently the boat is powered by a 15hp Saildrive and has a
12x9 prop, loaded displacement is +/- 6000lbs. my
cruise speed is 7kts and max is 9.5kts. My intent is to
keep the saildrive leg and simply remove the block and
adapt the existing shaft to a belt and pulley system.

Seems like there must be something wrong here.
<br><br>First, how does the calculation relate to hull
type/configuration? Theoretical hull speed on a 23' displacement boat
is going to be a lot below 8 kts. In my case,
5.8kts. I have always understood (and experienced with my
other displacement hulls) that to get 38% above hull
speed is going to take incredible amounts of additional
HP, if it's possible at all in the real world. I
don't really think that 8kts is a realistic
target.<br><br>More to the point: <br><That means that a<br> 1.4:1
Ratio would be ideal. anything less means that you are
wasting<br> power..... If your motor is not geared at 1.4:1
then you should either<br> change the ratio or select
a smaller prop.<br><br>I'm turning through a 2.4:1
pulley reduction. I had been concerned that this ratio
was too low, rather than too high! One of the major
manufacturers of electric boats (who will remain nameless but
the field is limited, right?) wrote me a letter at
the beginning of my project saying that "the
efficiency of a slow-turning propeller is what is required
to improve the efficiency of the electrical system
to a point where it is competitive in performance".
They use a 20 X 30 prop (!) and, if I recall
correctly, turn it with 10:1 reduction.<br><br>Elco
materials (NOT, I might add the mfr. referred to above,
which limits the list of possibilities
further!)illustrate a 6kts speed target, with 2:1 reduction and an
800 rpm target yields a prop with 12.1" ideal pitch.
They say "if propeller speed is more than 1000rpm
consider a gear or belt reduction to increase propeller
efficiency."<br><br>So my thinking had actually been the opposite: I
might improve performance by increasing prop size and
decreasing shaft speed--not the opposite.<br><br>I will say
that the speeds and draws I seem to be experiencing
out on the water are very similar to the calculations
presented for the Elco. But I am not at all turning maximum
rpm's on the motor and, at least with this particular
prop, find that the increased rpm's generate greatly
increased amp draw without any proportionate (although
there is SOME) increase in speed.<br><br>So...do I
optimize by slower (rpm) and bigger (prop) or the
opposite? Put that way, it sounds pretty
fundamental.<br><br><br>Larry