Talk me into a kiwi prop.

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GHA

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Or out. Heavy long keel steel boat so needs all the help it can get, but....

Will mean chopping a bit of the rudder round the aperture to make a kiwi fit and as I need a new prop anyway will come out at what, 750 more maybe?

Would be nice though, it's a cruising boat so just moving in light airs is a good thing.

Should I bite the bullet and find the cash or have I missed something....


(shaft isn't attached to engine yet in the pic)





Picture_zpsf7eb1eef.jpeg
 
Agree with Featherstream. More expensive but properly engineered and operates in a positive mechanical way rather than relying on springs and water pressure.

However, either will require significant chunks out of your rudder at the lower end of the cutout to allow the blades to swivel. Probably more than you think to give clearance when rudder is hard over. Guess how I know! - but well worth it, particularly if planning long distance under sail where the reduction in drag will increase daily distance run.
 
Tranona said:
However, either will require significant chunks out of your rudder at the lower end of the cutout to allow the blades to swivel.
Click to expand...

I had aperture size problems. Feather stream proved to be the one that took up the least room. Kiwi wanted quite a lot.
 
Give full circle a PM, he was a fairly early adopter of the kiwi prop, having been on his boat it did seem to work very well.

Be polite cos he's a moderator, one false word and it's curtains.:)
 
GHA said:
Aha, now that's one which the cardboard cutout didn't check... Ta
Click to expand...

That is where I went wrong. It is the angle of the stock that stuffs you - OK if the stock is vertical. Made worse in my case because the rudder is nearly 2" thick on the leading edge so needed a lot of shaping. worth it though as the prop does what it claims.
 
My Volvo 2030 requires to be left out of gear when sailing. Upon reaching a boatspeed of 4kn> the prop would spin with a rumbling noise. I found this irritating and I assumed loss of speed through the drag of the prop.

I replaced my fixed 2 blade prop with a Kiwi not before I'd taken careful sailing and motoring performance 'data'.

Sadly, my comparison 'data' is meaningless. I cannot give you 'proof'. I put it down to there being too many variables.

The prop feathers ok, the prop drives the boat ok. It requires maintenance (grease and oil). It is unhappy after settling into squishy mud. It has survived striking driftwood (I trimmed a bruised blade with a knife) It has survived entanglement with a lobster pot rope.

I have no experience of other props.
 
I've had my kiwi prop for about 7 years now. Benne 38' perkins 4108 2:1 zf gearbox.

Great performance in fwd gear, 6.5 to 7 kts at 2100 engine rpm, good bite in astern but lots of propwalk but less than old 3 bladed 'bucket'. Over-propped in astern.

Noticable difference in accelerating out of a tack and probable a good .5 knot overall advantage in winds below f5.

Annual maintenance is a good greasing.

Considerable saving on folding/feathering bronze prop.

I fitted a spur cutter at the same time and have had one known incident of a 16 mm rope entanglement and cut with the only noticeable effect to the prop of a slight abrasion on one leading edge.

Very happy.
 
Check your gearbox ratios.
The Kiwi has a much higher pitch astern than forward. Most gearboxes have a lower ratio astern so you can get away with it.
A few gearboxes have a higher ratio astern than forward. In such cases the Kiwi is better avoided going by my experience.
It's vital to keep the Kiwi clean and well greased and the blades very free.
The Featherstream is a much nicer piece of engineering - at a higher price - and astern pitch can be set lower than forward if required.
 
GHA said:
Talk me into a kiwi prop.
Click to expand...
How many miles do you do per year. What is the speed increase, e.g 2,000 * 0.1 = 200 at 5kn = 40 hours or 20,000 * 0.1 at 5kn = 400 hours.

You will be able to work out when it becomes cost effective.
 
Plevier said:
Check your gearbox ratios.
The Kiwi has a much higher pitch astern than forward. Most gearboxes have a lower ratio astern so you can get away with it.
A few gearboxes have a higher ratio astern than forward. In such cases the Kiwi is better avoided going by my experience.
It's vital to keep the Kiwi clean and well greased and the blades very free.
The Featherstream is a much nicer piece of engineering - at a higher price - and astern pitch can be set lower than forward if required.
Click to expand...
Good point, ta
Gearbox is 2:1 both forwards and reverse on a beta 35 so should be OK?
Not that I ever go backwards, can't steer :)

So how much is a featherstream? Can't find a price on the web.
 
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