Kiwi prop - Composite Variable pitch

[Wckoek]

https://www.kiwiprops.co.nz/cms/
Looks interesting and not expensive either.
Has anyone tried their propeller?
Any drawbacks to composite blades vs bronze?

[Jim Cate]

I won't steal his thunder, but you might query GILow (a prolific poster here) about his experience with one. A hint: it involves numerous broken blades.

Jim

[Wckoek]

I see, I might look into Flexofold or Gori then.

[Jim Cate]

Originally Posted by Wckoek

I see, I might look into Flexofold or Gori then.

Well, I'm a big FOF fan, but you should really talk to Matt. His experience, after all, is best explained by him rather than relayed by me...

FWIW, I prefer a good folding prop over a feathering version after years of experience. The FOF three blade is, IMO, the best of the lot.

Do have a look at the published impartial prop tests carried out by folks at MIT and several others as well. The results are pretty conclusive to me!

Jim

[Wckoek]

Originally Posted by Jim Cate

Well, I'm a big FOF fan, but you should really talk to Matt. His experience, after all, is best explained by him rather than relayed by me...

FWIW, I prefer a good folding prop over a feathering version after years of experience. The FOF three blade is, IMO, the best of the lot.

Do have a look at the published impartial prop tests carried out by folks at MIT and several others as well. The results are pretty conclusive to me!

Jim

I understand that while feathering have the least drag and more simple/reliable, it wasn't as efficient in powering and thrust as feathering.
So if it was more a sailing/racing boat with small tanks I might go folding, but cruisers should go feathering, is that right?


Where I can read the MIT prop test?

[Jim Cate]

Originally Posted by Wckoek

I understand that while feathering have the least drag and more simple/reliable, it wasn't as efficient in powering and thrust as feathering.
So if it was more a sailing/racing boat with small tanks I might go folding, but cruisers should go feathering, is that right?


Where I can read the MIT prop test?

There has been a lot of discussion on these subjects here on CF in the past, and lots of disagreement voiced. There have been quite a few impartial tests done by various organizations, and in general the following is true:

Folding props have less drag than feathering.
Feathering props, due to their flat blades, are less efficient than either fixed or folding props.
Feathering props produce the highest bollard pull in reverse, but not in forward.

And so on...

You should have a look at the tests and make up your own mind. The MIT test is available at

Comparison of Ten Sailboat Propellers - PDF Free Download

And if you google "sailboat propeller tests", a list of several other tests will pop up, and they include a wider variety of props, but are not done with the scientific rigor of the MIT effort.

It is an interesting subject for sure, one with some real effects in one's sailing and motoring performance. Few yotties have wide enough experience to make their anecdotal recommendations very valid. One notes that in the various CF threads on the subject there is a strong tendency for folks to be sure that the prop that they have is the best. IMO even the less scientific tests give a better representation of the realities of performance, so have a look at all of them. I think you will find them interesting and help with your decision.

FWIW, I have owned and cruised/raced with two and three blade fixed, two blade Martec and Gori folders, an Autostream three blade feathering and a Flex O Fold three blade folding. Of those, the latter is my favorite, both from a performance aspect and it's long term reliability.

Jim

[Wckoek]

Originally Posted by Jim Cate

There has been a lot of discussion on these subjects here on CF in the past, and lots of disagreement voiced. There have been quite a few impartial tests done by various organizations, and in general the following is true:

Folding props have less drag than feathering.
Feathering props, due to their flat blades, are less efficient than either fixed or folding props.
Feathering props produce the highest bollard pull in reverse, but not in forward.

And so on...

You should have a look at the tests and make up your own mind. The MIT test is available at

Comparison of Ten Sailboat Propellers - PDF Free Download

And if you google "sailboat propeller tests", a list of several other tests will pop up, and they include a wider variety of props, but are not done with the scientific rigor of the MIT effort.

It is an interesting subject for sure, one with some real effects in one's sailing and motoring performance. Few yotties have wide enough experience to make their anecdotal recommendations very valid. One notes that in the various CF threads on the subject there is a strong tendency for folks to be sure that the prop that they have is the best. IMO even the less scientific tests give a better representation of the realities of performance, so have a look at all of them. I think you will find them interesting and help with your decision.

FWIW, I have owned and cruised/raced with two and three blade fixed, two blade Martec and Gori folders, an Autostream three blade feathering and a Flex O Fold three blade folding. Of those, the latter is my favorite, both from a performance aspect and it's long term reliability.

Jim

I see, thanks for your insight.

[chrisr]

we have just fitted a kiwiprop to our stb side engine (after the previous fixed 3 bladed prop decided to continue the voyage by itself...)

two main sellers for kiwiprop for us were (1) price (2) service

to compensate for the lesser efficiency, manufacturers convinced us to fit a 18" to replace the previous 17"

prop went on easily and secures to shaft very safely. cannot imagine it ever falling off. so far (3 months) we're very happy with it. thrust seems fine...esp in reverse

maybe the composite blade material is not as strong as bronze, but it's certainly lighter and i've not heard of any ongoing problems (nb : there as some a few years ago which prompted a redesign)

my only disappointment is some vibration between 2100-2500 rpm...which is annoying as it's a common cruising rpm for us. keep meaning to contact John Blundell (the kiwiprop man) about it but not gotten to it yet

overall...we are happy

cheers,

[chrisr]

ps : another very good, detailed and fair review of a whole host of props (inc kiwi) is at

https://www.yachtingmonthly.com/gear...ler-test-29807

cheers,

[DiStefano]

Very fragile, complicated and costly to repair, require ongoing maintenance, but have minimal / no customer support (especially in NA) and an atrocious website. In the (likely) event of rope entanglement expect multiple component failures, lengthy wait for parts and $75 per shipment. May be ok for racers, but I would definitely NOT recommend this product for cruisers.

[Uncle Bob]

Originally Posted by DiStefano

Very fragile, complicated and costly to repair, require ongoing maintenance, but have minimal / no customer support (especially in NA) and an atrocious website. In the (likely) event of rope entanglement expect multiple component failures, lengthy wait for parts and $75 per shipment. May be ok for racers, but I would definitely NOT recommend this product for cruisers.

As one that is considering this prop may I ask if this summary is from your personal experience or something you have heard from someone that knows someone or perhaps your assumptions.

[DiStefano]

Personal, first-hand experience. I have "inherited" these props from the previous owner - and step by step I had to become an expert in their disassembly, diagnostics, and logistics of parts replacements. Bear in mind that I am in the USA. If you're in ANZ, then your access to parts will be cheaper/faster. But still, IMHO, they are fragile (despite assurances to the contrary) and require a lot of effort to get right/maintain/etc.

[GILow]

Originally Posted by DiStefano

Very fragile, complicated and costly to repair, require ongoing maintenance, but have minimal / no customer support (especially in NA) and an atrocious website. In the (likely) event of rope entanglement expect multiple component failures, lengthy wait for parts and $75 per shipment. May be ok for racers, but I would definitely NOT recommend this product for cruisers.

Well, everything you said there goes against my years of experience with my kiwi prop.

Customer support, for a start, is exceptionally good.

Maintenance is trivial. A shot of grease every two years when I slip the boat.

I did break my prop, through my own stupidity. I managed to slam it into the leading edge of the rudder. I kissed a blade and part of the hub goodbye but it was a simple and cheap fix requiring no special tools and no significant delays. Had that been a bronze prop I would have kissed the gearbox goodbye for sure, as well as the whole prop, not just a couple of parts. Oh, and I was still able to use the prop with remaining three blades to get the 20 miles up River to the marina. Simply wouldn't have been possible had the prop been bronze. The imbalance would have destroyed all sorts of stuff for a start.

Support out of New Zealand was so.good that they had the parts waiting at my destination before I arrived. ONE phone call was all it took.

I will be fitting one to the new boat as soon as I can.

[DiStefano]

Well, there are different stories. Hence the name of my boat (“Another Story”). But I have proofs - invoices, email threads, etc. of what I am writing about. In summary: when all works well, this product is likely ok. But when things break, they go really bad. They don’t maintain proper levels of spare parts, some of their dealers are unresponsive, instructions are contradictory in parts, website choke full of grammatical errors (see for yourself), they overload you with technical mambo -jumbo, etc. Again, individual experience will vary. Mine was horrific. The only “bright” spot was the WhatsApp support by John. But even with it, I had to completely disassemble both units and I am waiting for the 3rd shipment of required parts - with fingers both full of grease and crossed :-) that I will be able to fix them.

[GILow]

Originally Posted by DiStefano

Well, there are different stories. Hence the name of my boat (“Another Story”). But I have proofs - invoices, email threads, etc. of what I am writing about. In summary: when all works well, this product is likely ok. But when things break, they go really bad. They don’t maintain proper levels of spare parts, some of their dealers are unresponsive, instructions are contradictory in parts, website choke full of grammatical errors (see for yourself), they I reload you with technical jumbo-jumbo, etc. Again, individual experience will vary. Mine was horrific. The only “bright” spot was the WhatsApp support by John. But even with it, I had to completely disassemble both units and I am waiting for the 3rd shipment of required parts - with fingers both full of grease and crossed [emoji41] that I will be able to fix them.

Word of advice, stick to the NZ web site. The US one is weird. I’m not sure why it is there, except perhaps to deal with the fact that some people don’t realise there are other country codes in the DNS hierarchy.

And frankly, if you are having that much trouble working on such a simple mechanism you should hire a professional. A two year old can assemble these things.

While drunk.