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Author Topic: Five bladed prop V Kort Nozzle prop.  (Read 5447 times)

Bluechrisp

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Five bladed prop V Kort Nozzle prop.
« on: January 03, 2010, 05:06:44 PM »

Hello all,

Just a bit of light head scratching, on my 29" tug with a single steering nozzle, in the intrest of money saving/ penny pinching, using a 600 graupner 6v engine direct  and 6V batt, which would produce more thrust the 5 bladed 50mm or the Korts 50mm?

Any help or kind words would be greatly received.

Thank you
  CP
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DickyD

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #1 on: January 03, 2010, 05:26:25 PM »

4 bladed prop is more than adequate unless you want to go water skiing  O0
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Pirate

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #2 on: January 03, 2010, 06:02:46 PM »

Have thought much about using five blades in a Kort and asked the nice man at prop shop a couple of years ago. His answer was  ....   it will add about 10-15% more thrust   .... as my finances have yet to grow to purchasing a five blade Kort prop I just dream on. Although I have considered buying a Raeboshe (Spelling!) five blade a tad over size and grinding the tips off to fit a Kort. I must say that my experience with towing is  ... the largest motor, the biggest Kort and the greatest power allways wins for me (although when not towing the resultant disproportionate power does tend to lift the pointy end up a tad!!! but thats a humorous small price to pay.)
Just my experience and my thoughts
Pirate
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ray123

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #3 on: January 03, 2010, 06:26:02 PM »

i would go with the kort prop   4 blades is ok   as you have a kort nozzel you just as well get the most of it  (thrust!)  :-)) with it being over powered  then just hold ''back'' the throttle a bit  ;)  regards ray
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FullLeatherJacket

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #4 on: January 03, 2010, 06:29:18 PM »

I can't find a Speed 600 6v listed anywhere, but if you do have one then take care as the lower voltage Speed series tend to be the quicker motors.
FLJ
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DickyD

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #5 on: January 03, 2010, 06:52:49 PM »

Graupner don't do a 600 6V  Dave. They do 7.2 V, 8.4V, 9.6V and 12V.  :-))
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Bluechrisp

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #6 on: January 03, 2010, 07:05:29 PM »

Graupner don't do a 600 6V  Dave. They do 7.2 V, 8.4V, 9.6V and 12V.  :-))
It must be 7.2V 600 then... %) i expect from the cander and humour the 600 is to powerful, maybe a reduction gear or ?  {-) is the price of £20 around the correct target for the Korts 50mm prop.

cheers

CP
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DickyD

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #7 on: January 03, 2010, 07:17:21 PM »

I'm going to start something here but on my last two models from Model Slipway I went for the brass 4 bladed props. When I got them, they were normal props, and guess what, they worked just fine. You dont need a kort prop unless you want your model to be accurate in every detail. Power wise it doesn't make any difference on a model.

Wait for it.
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Richard Solent Radio Controlled Model Boat Club http://www.srcmbc.org.uk

Pirate

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #8 on: January 03, 2010, 09:47:29 PM »

Power is in the finger of the user.
 I disagree personally with your findings Dicky.
A tug with a Kort performs better with a Kort prop not a standard one as there is great inefficiency (wasted power at the blade tips) when using a round tipped prop.
If you are to use a Kort then use a Kort prop!

Just my opinion though!
Pirate
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TugChief

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #9 on: January 04, 2010, 06:08:24 AM »

Dear CP,

You should also think about "prop walk" when going astern.  With an open 5 blade prop going astern in a straight line will be a challenge unless you have a large near ‘fully balanced’ rudder.  Due to the large surface area of a 5 bladed prop and the inefficiencies whilst going astern it will act as a paddle wheel and draw the stern of the vessel in the direction of astern shaft rotation.  This problem is 90%-95% eliminated by fitting a nozzle of obvious hydrodynamic reasons.

A nozzle is the way to go always.  It does not matter if you then have a 4 or 5 bladed prop but you will need to keep the pitch quite fine if you are going direct drive to keep the shaft speed up to avoid motor overload at full towing power.  Keeping pitch low and shaft speed relatively high gives you far better slow speed maneuvering characteristics which I am sure when you get your boat on the water will find of great benefit.

Tug Chief.
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Bluechrisp

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #10 on: January 04, 2010, 01:54:18 PM »

A nozzle is the way to go always.  It does not matter if you then have a 4 or 5 bladed prop but you will need to keep the pitch quite fine if you are going direct drive to keep the shaft speed up to avoid motor overload at full towing power.  Keeping pitch low and shaft speed relatively high gives you far better slow speed maneuvering characteristics which I am sure when you get your boat on the water will find of great benefit.

Hello TugChief,

Thank you for the above, as this is my first build in the tug world... and much to learn! do all Korts props have the same pitch and if not, who would be a good person to speak to in making up a prop for towing and pushing?

I will shortly be putting in for stores as to say, is there a preferred ESC for the tug user, in my other boats I have the Mtroniks?

thank you

CP
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TugChief

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #11 on: January 05, 2010, 11:45:57 AM »

Hi CP,

Simon at Prop Shop is the place to go, he supplies a lovely 4 or 5 blade nozzle prop which has a nice pitch.  If you really want to look fancy he does a fantastic casting of a controllable pitch propeller which has a slightly finer pitch and would be ideal for you as you are going direct drive.

Have a look at; www.prop-shop.co.uk

The site is undergoing a 'revamp' but give them a call and I'm sure he will send you a catalogue.

Darren.
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andywright

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #12 on: January 08, 2010, 08:29:10 PM »

Kort is definately the way to go, I run a Mobile Marine models Nangee on one steerable kort, with a prop shop kort prop, it steers brilliantly, I do not miss having two props at all, just think if you went twin screw you would need two of everything, so if going single, make it the best you can. I agree with tug chief a five blade prop you will get severe prop walk going astern, it will be uncontrollable.
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Bluechrisp

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #13 on: January 11, 2010, 01:05:31 AM »

Hi all,

Thank you for the tops tips and advice, always good to read and natter over, making a slow start, Hope to test the engine and electrics soon.

cheers
CP  :-))
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Bluechrisp

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Re: Five bladed prop V Kort Nozzle prop.
« Reply #14 on: February 17, 2010, 08:54:24 PM »

Hello all,

Just an update, I tried the 600 motor looked good at full speed 3 MPH ish, a good bow wave, but just to fast, for a 29" tug, have now fitted a video recorder motor with 6 v SLA, not sure of the rpm, but looks good and goes astern in a straight line, could try a 12V which could help with the weight, needs to go down about an inch.  :-))

CP
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