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Author Topic: korts???  (Read 1928 times)

grace

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korts???
« on: March 01, 2014, 08:50:33 PM »

do you need steerable kort nozzles if your running twin motor with a pair of esc??   
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Stavros

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Re: korts???
« Reply #1 on: March 01, 2014, 08:57:51 PM »

No as you can buy a ACTion mixer to allow you to steer off the right hand stick on th e controller,what this will do is to reduce power on one motor and increase the other one thus allowing you to steer
 
Dave
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NFMike

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Re: korts???
« Reply #2 on: March 01, 2014, 11:47:57 PM »

You never need a steerable Kort, they just give a bit more steerability than most simple rudder solutions.


For twin props being able to control each shaft independently gives good manoeuverability - a mixer will sometimes be enough but completely separate control (aka 'tank' steering) is best - it's what full size boats use. The downside is it needs two r/c channels for power control, although with modern 2.4GHz systems that really isn't much of an issue.


(Does anyone actually use steerable Korts on twin prop boats (in the prototype)?)

grace

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Re: korts???
« Reply #3 on: March 02, 2014, 12:04:38 AM »




(Does anyone actually use steerable Korts on twin prop boats (in the prototype)?)


my pusher tug uses steerable twin korts when i got it. it was on one esc but iv converted it to two esc's..most of the time i use the throttles like tank tracks to maneuver, if im doing really slow work i use the korts to steer but mainly the throttles.....the next tug i get i want to make it very powerfull with twin screw,,,,,is there any benifit in using a tube over the props and then a normal rudder??the boat will have a bow thruster at the bows.........

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derekwarner

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Re: korts???
« Reply #4 on: March 02, 2014, 01:24:27 AM »

grace....I do not use any form of Kort nozzle, however remember reading many years ago..... %) during the development of the said system, tests on propeller performance were confirmed as having greater thrust [with the water being directed through a fixed tube], than open water for the same input power............

I am sure a search on WIKI will find some references back to these [1960's?] studies.................Derek
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Derek Warner

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Peter Fitness

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Re: korts???
« Reply #5 on: March 02, 2014, 03:25:25 AM »

I have a pusher tug which is used as a rescue vessel at our club lake. It has 2 motors and ESCs, and is steered by tank steering. It has no Korts, but a smaller version I built for my grandsons in Sydney has a single, non-steerable Kort. It has great pushing power for its size, and I think that's down to the fact that it has the Kort nozzle.


Peter.
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derekwarner

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Re: korts???
« Reply #6 on: March 02, 2014, 04:09:30 AM »

A little piece of semi useless information {-)

Between 1976 & 1979, Australia commissioned the building of four 100,000 DWT bulk carriers in Norway

Being named the 'Australian Pioneer, Purpose, Prospector & Progress'....naturally they were termed as our P boats.........suffice to say....on completion each could not secure a cargo & each spent many months at anchor in the fjords of Norway

I do remember flying 3800 km from Sydney to Perth to Dampier to inspect a fault with the Prospectors main engine Woodward governor hydraulic amplifier  >>:-(

Cut a long story short  :embarrassed: each of the P boats was fitted with a FIXED kort nozzle........... Derek
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Derek Warner

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NFMike

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Re: korts???
« Reply #7 on: March 02, 2014, 01:47:32 PM »



(Does anyone actually use steerable Korts on twin prop boats (in the prototype)?)


my pusher tug uses steerable twin korts when i got it. it was on one esc but iv converted it to two esc's..most of the time i use the throttles like tank tracks to maneuver, if im doing really slow work i use the korts to steer but mainly the throttles.....the next tug i get i want to make it very powerfull with twin screw,,,,,is there any benifit in using a tube over the props and then a normal rudder??the boat will have a bow thruster at the bows.........


In the prototype a Kort is not just a tube - it's a carefully shaped hydrodynamic article matched to shaped propellers which increases the efficiency/thrust. When they are made steerable there is almost certainly a trade off of some efficiency as the clearances/shapes will need to allow for rotation. So although not uncommon on single prop vessels I wonder if it would be done on twins in the prototype, which have better manoeuverability anyway.

Peter Fitness

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Re: korts???
« Reply #8 on: March 03, 2014, 04:37:38 AM »

I realise the full size Kort is hydrodynamically shaped, but I didn't bother with mine, just using a piece of 50mm PVC tube. I did, however, shape the tips of the prop in a lathe, to give less separation between prop and Kort tube. I placed the rudder directly behind the Kort tube, and this gives extremely responsive steering.


Peter.
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