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Old 07-04-2007, 15:09   #16
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The Kiwi prop in reverse is fixed at 23 degrees...maximum pitch. Most transmissions have a lower ratio for reverse. Means you kill the engine, many times, when going into reverse or you overload it. Doesn't mean I'm trying to make 2400 RPM in reverse. It means the prop pitch is proper by the amount of rpm you can obtain under max throttle. You should know this as that is how a prop is sized. My maximum rpm in reverse is 1200 rpm. It means I have WAY overloaded the engine. It's a bad thing and leads to significant carbon buildup or killing the engine under docking manuevers. Kiwi props knows about this problem and everyone has it....some worse then other...all depending on the reverse transmission ratio. Idle engine RPM's is critical and specified in the manual for the props. Not running any engine accessories while reversing is also critical. Everything must be off while manuevering. If you have a higher reverse ratio then you'll be okay, but few boats have this. If not then you'll have problems...most people do, especially as time goes on and the blades approach the point of needing lubrication.

I have been in close contact with Kiwi props, have even been to their shop and had the props rebuilt with smaller blades. Excellent support from the owner John Blundell. Absolutely terrific support. Problem remains with the reverse however...it's a bad thing to kill the engine (repeatedly) when trying to pull into a marina and approaching the pier.

The material is a fiberglass/plastic composite. It is INCREDIBLY strong. I was given a sledge hammer to hit a blade held at the root in a vise. Impossible to break and far better then a bronze blade, especially for manufactoring and running into things. Wrapping a line around it while underway won't hurt it or distort it. Unfortunately it promotes growth. Bronze doesn't. The kiwi prop blade surface is very difficult to keep ANY anti-fouling on as it's very slick. You can paint bronze. I saw one boat which got re-hauled 4 hours after being splashed from the boat yard. The anti-fouling had worn away completely at the blade edges and another 10 hours of operation would have meant no antifouling at all. It was a hard anti-fouling (micron 66). I'm now using Propspeed and will see how that holds up. It can only be applied by the boat yard and cost $150 per prop to apply. The boat yard won't warrant the application on these blades due to the material but feel that it will be the best thing and should give good performance. This is an issue of importance but in itself would not keep me from buying these props again. I can always scrub the props and prefer this to having the bronze blades. The reverse issue is the main problem as it puts my boat into jeopardy and is ruining my engines.

Since I originally purchased my props a few improvements have been made. An o-ring at the base of the blades to keep the lubricant in, a small shaving on the blade edge, and most props now use stainless steel shaft nuts rather then the plastic ones which had to be burned off.

Pitch ratio (forward) is set by turning a set screw on each blade. No means of measuring it is possible and you rely on turning each set screw the same amount. Not a big deal at all. No reverse pitch adjustment is possible. This is a big deal.

Summary: Great props with big reverse issues but almost all props of this type have some kind of issue. Very low cost and good performance under sail and motoring. Great customer service. Easy and cheap to replace blades. I don't recommend this prop for any boat with low reverse ratio (many boats).
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Old 07-04-2007, 16:28   #17
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Seems like the Kiwi Prop still has some serious bugs to be worked out. Thanks for the info.
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Old 08-04-2007, 11:02   #18
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What prevents the makers from adjusting the 'stops' use in reverse to alter the pitch?
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Old 08-04-2007, 14:27   #19
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There are no stops for the kiwi prop in reverse. It's a function of 3 rollers pressing against the blades which fixes the position. That's why the prop is max'd out for pitch. The blades are free floating, have no gears, springs, etc., just free to rotate on the hub as water forces past them.
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Old 10-04-2007, 13:49   #20
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I've had experience with both Kiwi Prop and Flex-O-Fold.

Last yacht had a Bukh 48 with a fixed 3-blade that I replaced with a Kiwi Prop. Got me nearly an extra knot sailing in lighter conditions. Lost about 0.5 knot of top speed. Reverse is awesome if you are used to fixed props - stops you like you have brakes! Tried re-pitching the Kiwi to improve top end but couldn't get it any better. Anti-fouled it with ablative and it lasted about 3 months. Just dived and cleaned it between anti-fouls after that.
Overall a great unit.

Current yacht has a Flex-O-Fold. I use Prop Speed and this is great. Mine is WAY over-propped for my Perkins 4-108. I only get 2100 revs max and it all goes back to the previous owner who ordered it from the local agents. Every bit of data he gave the suppliers was wrong - wrong HP, wrong displacement, wrong max revs, wrong trans ratio. I have re-done all the prop calcs and the prop should be an inch less in diameter!

I'm hoping I can just order new blades and keep the central boss. Anyone done this?
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Old 11-04-2007, 05:28   #21
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can't you get a prop shop to trim the existing blades

Mike
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Old 11-04-2007, 11:37   #22
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Mike, if pitch does not need changing - only diameter reduced you might be able to have a local shop trim the blades.

However, both my pitch and diameter needs changing so I am ordering new blades from Flex-O-Fold keeping hubs.
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Old 11-04-2007, 13:14   #23
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The ICW is not a great place for sailing. I would not run without an engine on while navigating though it. As such, I think you lose much of the advantage of a folding or feathering prop. If that were all the "sailing" I were going to do, I'd save the funds. Having said that, I usually had my mainsail up while I was in the ICW. Oten you get a push of a knot or two. Well worth it! I flew my main as my headsail obstructs my view somewhat.

Cheer, fair winds

Keith
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Old 11-04-2007, 13:55   #24
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Thanks guys, but both diam and pitch need to be changed. Still, new blades is better than a whole new prop!
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Old 12-04-2007, 01:21   #25
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Diameter will do nothing to very little in regards to the "over proping". Pitch is the biggest factor in that regards. Diameter does have a major bearing on noise in regards to the tips proximity to the hull.
I stand for correction here, but I don't believe the blades can be repitched. Pitching of these feathering props is as much about blade shape as it is bite. I think the "wing" shape of the blade is unique and parcel to it's angle of attack.
As I understand it, the hubs are the same, the blades are changable.

Hey Mike, nice boat you have mate. So why didn't you come over this way at Easter?
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Old 21-05-2007, 22:29   #26
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Hi Wheels

Sorry for the delay replying.

See my rusty valve post for the reason I missed your reply! Fixed now, so I'm back looking at the prop. Talked with Henley's (local agant for Flex-O-Fold) and they say they can trim down the diameter for me for a few $$$. I will do this in 2 steps just in case - and inch at a time - even though my prop calcs say it needs to come down 2 inches. Interestingly the Perkins will still pull just 1500 rpm in the marine even after the new head is on. So the old girl was able to make roughly the same HP with one exhaust valve that looked like a saw around the edge! Makes you wonder...

I see you when I'm down in Picton next!
Mike
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Old 22-05-2007, 07:50   #27
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Alan;

I had my props repitched. There was some concern because they are aluminum. The company told me sometimes aluminum cracks. But, there were no issues that I know of when they did them. I had my repitched by 2 inches. Probably only needed 1 inch, but, live and learn.
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Old 26-11-2007, 18:38   #28
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My next door neighbour had his bronze 3 blade fixed prop re-pitched and all went well until the next anti-foul haul. He discovered that the re-pitch had stressed the bronze which then caused an electrolysis type corrosion on the tiny stress fractures. If you do get your prop re-pitched - have a really good look at it before you put it back on so this doesn't happen to you.

Tricky.
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Old 11-03-2009, 20:32   #29
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Okay, it has been a couple of years on the Kiwi Props. How are they holding out? My sailing performance leaves a little bit to desired and I am seriously considering getting a pair of feathering props. The price point for the Kiwi's, especially when I need two, is very enticing.

Any updates?
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Old 11-03-2009, 20:41   #30
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I've also had flex-o-folds on two boats...

...without any problems whatsoever. In each boat I've gained more than half a knot sailing in light air without sacrificing anything under power. The only possible downside has been that I have to purchase the zincs from the factory since they've not been carried by my divers or by local chandleries. A minor drawback.
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