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Old 19-09-2018, 02:39   #1
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Small Kiwiprop 3-blade

I need a Kiwiprop to modify and experiment on, since I want to optimize it for recharging through my electric propulsion system. Preferably it should have a diameter of 15 or 16 inches and fit a 1 inch axle (25 mm), but I see there are adaptors available on the internet, so every moderate axle diameter is interesting to me.


Also other feathering or variable pitch propellers of similar size may be of interest.
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Old 19-09-2018, 02:55   #2
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Re: Small Kiwiprop 3-blade

Welcome to CF,

I have been looking for 2 years for such a sized Kiwi prop but when they do come up they are north of £600, but good luck.
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Old 19-09-2018, 04:42   #3
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Re: Small Kiwiprop 3-blade

Quote:
Originally Posted by jaffe View Post
I need a Kiwiprop to modify and experiment on, since I want to optimize it for recharging through my electric propulsion system. Preferably it should have a diameter of 15 or 16 inches and fit a 1 inch axle (25 mm), but I see there are adaptors available on the internet, so every moderate axle diameter is interesting to me.


Also other feathering or variable pitch propellers of similar size may be of interest.
Here's a couple to look at:
https://sbo.sailboatowners.com/gear/...showad&id=4618
https://sbo.sailboatowners.com/gear/...showad&id=5921
Good Luck!
Doug
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Old 20-09-2018, 20:37   #4
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Re: Small Kiwiprop 3-blade

Jaffe:
You don't want a Kiwi prop. It's feathering prop which won't work for what you want to do, regenerative electrical generation. Under power it automatically assumes the set pitch for forward propulsion. In reverse it resets the the pitch for reverse thrust. When there is no power applied to the drive shaft it featthers. You would need to completely reengineer the prop in order to get it to assume any pitch other than feathered when the shaft is unpowered. By reengineer I mean design a hollow drive shaft and new bearing system and design a new prop hub. The only thing you are going to be able to use from the Kiwi prop are the blades.

You want to play with regenerative power, buy an old Albin Vega with the original inboard and variable pitch prop. Replace the motor and play with that for a bit. Then look at something bigger.
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Old 20-09-2018, 20:57   #5
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Re: Small Kiwiprop 3-blade

https://www.boatdesign.net/threads/c...p.50217/page-7
Matching power to the prop - Ocean Navigator - January/February 2003
https://www.practical-sailor.com/rev...iew/ALBINV.php
Controllable Pitch Propellers
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Old 09-10-2018, 13:26   #6
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Re: Small Kiwiprop 3-blade

This one just hit the market:
https://www.ebay.com/itm/Kiwi-Feathe...t/142967845089
Good Luck!
Doug
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Old 10-10-2018, 11:39   #7
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Re: Small Kiwiprop 3-blade

To Adelie:


How you do to make a Kiwiprop run the electric motor in order to recharge the batteries:
1) While sailing, run the motor in reverse for a second, and thereby make the blades flip into the right position
2) Turn off the motor. Because of the load put on the blades by the current from underneath your forward moving boat, the blades stay in the reverse position and turn the motor, which now works as a dynamo

3) If you want to quit recharging and sail a little faster, make the motor run forward for a moment, then turn the motor off, and the blades will flip into the resting position pointing backwards


The reason why I need a Kiwiprop, is because they have a fairly high pitch in reverse, which provides more torque with the blades in this position with the boat is moving forward, compared to blades with less pitch, which are more flat like a metal sheet and will slow down the boat


My intention is to increase the pitch by changing the knobs (increasing their diameter) that stand out of the hub to support the blades when the motor is running in reverse. The torque of the electric motor is significantly stronger than that of a diesel engine of similar horsepower, so I see no problem using higher pitch running astern.


I prefer an old propeller while doing this experiment, since I may have to adjust the spring and maybe destroy the propeller hub


To CatBoatDoug:


Thank you for helping me along in finding a suitable propeller. One of your suggested ones lack the central nut, it seems, but I have contacted the seller to see if he has it.
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Old 10-10-2018, 12:37   #8
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Re: Small Kiwiprop 3-blade

There’s not enough friction in the system to maintain the blades in the desired position while pulling power from the blades.

When the prop is being powered the blades rotate around their axis’ until the hit a stop which holds them at the desired pitch. This stop is adjustable on most feathering props.

This works the same way in reverse, though the stops are are not adjustable on Kiwi, they are set for 23* pitch.

When the motor is not pushing the blades will feather to the streamlined position. Sometimes friction will hold the blades in a pitched position against water flow, especially when boat speed is relatively low. In that case you bump the motor forward or reverse to get the blades to free up. Any significant water flow, which is what you want when pulling power from a prop, will cause the blades to feather and no power will be extracted.

If you want to know for sure ask the folks at Kiwiprop: mailto:feedback@kiwiprop.us

In both the forward or reverse the power flow if from the motor to the prop. What you want to to have power flow from the prop back to the motor. Feathering props aren’t designed for this. Won’t work with out extensive modification.
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Old 11-10-2018, 11:12   #9
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Re: Small Kiwiprop 3-blade

Adelie:

"There’s not enough friction in the system to maintain the blades in the desired position while pulling power from the blades"


Me:
Oh yes, there is. Turning the electric 9,6 kW motor takes some torque, which is the reason why I can't use my former fixed propeller with a 12' pitch in both directions. The pitch is too low to turn the motor and this flat, unbfolding propeller slows down the boat.


Adelie:

"When the prop is being powered the blades rotate around their axis’ until the hit a stop which holds them at the desired pitch"... "the stops are are not adjustable on Kiwi, they are set for 23* pitch"...

"When the motor is not pushing the blades will feather to the streamlined position."


Me:
Whether you drag a boat forward with a stopped propeller or whether you reverse the electric propulsion motor (or diesel engine in most cases) on a stopped boat, the forces on the propeller blades are similar. You have to use your imagination and think of an opposite situation, the boat is being pulled by the sails with the propeller blades unable to switch back to the feathering position because of the water current forcing them to stay put.


If you want to know for sure ask the folks at Kiwiprop: mailto:feedback@kiwiprop.us


Why not ask the producers instead? A while ago I sent an email to Kiwiprop in New Zealand. Here is an extract from the answer:


(from John Blundell)
Thank you for your interest in our propellers.
We have received a number of similar enquiries to yours over the years and now have some 19 Kiwiprops installed on electric drive trains for the very reasons you are asking namely:
  • If you are sailing and wish to engage autorotation to regenerate - then simply engaging reverse on the motor will push the blades to the reverse position where they will stay engaged as the generated propeller torque is greater than the spring torque as long as sailing speeds are maintained. This speed will be dependent upon blade size / shaft angle / sailing speed but typically the unit would stay in autorotation above about 1 knot.
  • To remove the autorotation - simply engage Ahead - then idle - then neutral and the blades will return to the feathered position.
  • In all cases the blades will adopt the maximum allowable pitchº setting ( Typically ~ 24º ) irrespective of the Ahead pitch set on the unit.
.....Cheers, John Blundell


Fantastic?
Electric propulsion requires new mindsets, not always compatible with traditional ways of thinking
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