Another message board had a discussion about using the larger trolling motors on sailboats up to 24' if the motor was going to be used primarily for docking. Now, I have no idea what 74 lbs of thrust translates into when talking horsepower. anyone had any experience?
aurora@capital.net
trolling motor for cd25
Moderator: Jim Walsh
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Dana
Re: trolling motor for cd25
Thrust is probably a better term to use when considering an engine than just horsepower. It relates the amount of force in lbs. that the engine has in pulling the boat forward....same as pushing on the back of the boat with the same force necessary to lift 74 lbs off the ground. For a displacement type of sailboat, i.e. Cape Dory, a higher thrust design for a given HP rating is desirable.
You see....Horsepower is related to a force (thrust) pushing something over a distance. IE, HP = Thrust X Distance
You know the old Work= Force x distance......
For a fixed motor HP like a 9.9, one can have a slow turning high thrust design (larger diameter prop with a shallow propeller pitch (9" pitch...meaning it would move a boat 9" forward with one revolution ideally) which does not move the boat at any great speed but has more force doing it. And it is the force which keeps you moving on a windy day.
IF the propeller was a 13" pitch (13" distance per revolution), it must have lower thrust or pulling force for the same horsepower rating.
Well the fact is most outboards are designed for planing power boats.
They are designed to operate at high speeds (2-stroke) with moderate high pitch designs and they do not necessarily need a lot of thrust to push the boat. All of these are opposite to the needs of a displacement sailboat.....they can not go fast, they normally can not plane, they need more thrust. So......one wants more thrust (larger diameter and shallow pitch props) and slow turning engines for the same horsepower rating. So looking at just HP is not generally enough, should consider the size and pitch of the prop and RPM of the engine for the HP rating you are looking for. This is really what separates sailboat outboards from power boat outboard needs.
darenius@aol.com
You see....Horsepower is related to a force (thrust) pushing something over a distance. IE, HP = Thrust X Distance
You know the old Work= Force x distance......
For a fixed motor HP like a 9.9, one can have a slow turning high thrust design (larger diameter prop with a shallow propeller pitch (9" pitch...meaning it would move a boat 9" forward with one revolution ideally) which does not move the boat at any great speed but has more force doing it. And it is the force which keeps you moving on a windy day.
IF the propeller was a 13" pitch (13" distance per revolution), it must have lower thrust or pulling force for the same horsepower rating.
Well the fact is most outboards are designed for planing power boats.
They are designed to operate at high speeds (2-stroke) with moderate high pitch designs and they do not necessarily need a lot of thrust to push the boat. All of these are opposite to the needs of a displacement sailboat.....they can not go fast, they normally can not plane, they need more thrust. So......one wants more thrust (larger diameter and shallow pitch props) and slow turning engines for the same horsepower rating. So looking at just HP is not generally enough, should consider the size and pitch of the prop and RPM of the engine for the HP rating you are looking for. This is really what separates sailboat outboards from power boat outboard needs.
darenius@aol.com
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Catherine Monaghan
Re: trolling motor for cd25
Keith,
Trolling motors are great if you're talking about small, lightweight boats. We use one (Minn Kota) to propel our inflatable dingy rather than carrying an outboard and gasoline.
Trolling motors are used primarily by fishermen on lakes and rivers though there are saltwater trolling motors available. The idea is to move slowly and quietly through the water so as not to scare away the fish. The boats are usually less than 25' in length and are of the johnboat type.
We can make quiet trips to the shore with our dog in the middle of the night without disturbing anyone else in an anchorage or mooring field.
Your little Cape Dory probably weighs 10x what a little fishing boat weighs. I don't think it would be a good choice for your CD.
If you're still interested, check out Minn Kota's website at:
<A href="http://www.jwa.com/motors/minnkota/minnkota.html">Minn Kota trolling motors</A>
or MotorGuide's website at:
<A href="http://www.motorguide.com/">MotorGuide's trolling motors</A>
to check out their line of Great White trolling motors.
You'll also see what kind of boats use these motors.
catherine_monaghan@merck.com
CD32 Realization
Raritan Bay
catherine_monaghan@merck.com
Trolling motors are great if you're talking about small, lightweight boats. We use one (Minn Kota) to propel our inflatable dingy rather than carrying an outboard and gasoline.
Trolling motors are used primarily by fishermen on lakes and rivers though there are saltwater trolling motors available. The idea is to move slowly and quietly through the water so as not to scare away the fish. The boats are usually less than 25' in length and are of the johnboat type.
We can make quiet trips to the shore with our dog in the middle of the night without disturbing anyone else in an anchorage or mooring field.
Your little Cape Dory probably weighs 10x what a little fishing boat weighs. I don't think it would be a good choice for your CD.
If you're still interested, check out Minn Kota's website at:
<A href="http://www.jwa.com/motors/minnkota/minnkota.html">Minn Kota trolling motors</A>
or MotorGuide's website at:
<A href="http://www.motorguide.com/">MotorGuide's trolling motors</A>
to check out their line of Great White trolling motors.
You'll also see what kind of boats use these motors.
catherine_monaghan@merck.com
CD32 Realization
Raritan Bay
keith wrote: Another message board had a discussion about using the larger trolling motors on sailboats up to 24' if the motor was going to be used primarily for docking. Now, I have no idea what 74 lbs of thrust translates into when talking horsepower. anyone had any experience?
catherine_monaghan@merck.com