Opinions on folding/feathering propeller

[nagy592 21]

So you can get substantially more power in reverse, esp with a feathering, but I think you are thinking folding now? which can have less power in reverse.

If you match the prop really well to your boat, or get one with adjustable pitch, you can actually end up with higher motoring speeds over your fixed prop. It all depends how well matched your fixed prop is. With the adjustable pitch, you just tweek it until it is optimised. With a unit where the pitch is fixed, you just have to hope the first guesstimate is close enough, same issue with a fixed prop.

Yes I'm drifting towards the two blade folding, and actually I hoping a bit more than a "guesstimate" from a manufacturer, whoever it will be. That is the reason why I would prefer to get a purpose made with respect all known factor. Am I expecting too much? 

[nagy592 21]

I have two Kiwiprops.

I get them to service them each year and it costs around $120.00, so $60 each and they are given a full birthday.

 

What I like about kiwiprop is the owner is a bit of a boffin, so went away and looked at how he could get me a little more speed. Actually spent quite a bit of his own time to see what pitch and variables I needed....he came to the conclusion, which he backed up with a shitton on a data, that my boat suffers from terminal slowness disease, and no matter what prop I use, Im going to be going really farken slowly...and he was right.

 

They appear to enjoy their work and want their product to succeed

Good to have local support, as I'm in Christchurch/Lyttelton I wouldn't expect to get that much support. Do you have them on a cat?

[Fish 0]

Am I expecting too much? 

That is a loaded question. It depends on what your expectations are and how fussy you are. And I should say I've never bought a 2 blade folder so I don't have any direct experience with suppliers sizing these to my expectations.

But if you think about what your expectations are, even list each element you want, that would help inform where you want to go.

One thing that is well known is that any folding or feathering prop will substantially improve your sailing, both speed and pointing. There is a marginal (slight) reduction in drag for a folding over a feathering. Unless your into the latest 3Di sails and tweeking etc, I wouldn't rate that as a big factor.

The next question is how important is your motoring performance? If you did 5 knts instead of 5.5 knts at cruise would you care? If you dropped down to 2.5 knts motoring into a nasty chop would this be a major issue? And how much close maneuvering / importance of reversing?

 

Obvious advantage of a 2 blade folding over say a 3 blade folding is they are cheaper (roughly half the price?). There is a perception that they don't give as good motoring performance as a 3 blade (any type of 3 blade). In essence props rely on surface area (Disk Area Ratio, or a bunch of similar measures). Because a 2 blader has less surface area it needs either larger blades (in area, not in diameter). It is a general rule to get the biggest prop that will fit on your boat (in diameter). Once you've got the biggest diameter that will fit, and a fixed blade area, then the next only option is to increase the pitch to get more 'bite' or power into the water. Increasing pitch can reduce efficiency and potentially make it harder to match well with the engine / gb. Short story is a 3 blade is always going to be more efficient than a 2 blade of the same diameter. Does that matter? 2 blades have been used for a long long time, plenty of people are perfectly happy with them. Could you get greater efficiency / better motoring speeds with a 3 blade, most likely, but the prop will cost a fair amount more for a marginal improvement in motoring performance.

 

So if you are happy to enjoy the sailing performance improvement and motor around at what ever, you'll meet your expectations. If you are fussy about getting that last 0.1 or 0.3 of a knt out of the boat while motoring, you might be disappointing.

[nagy592 21]

What a relief... I'd like to enjoy sailing and the only thing what I want from the propolution to give me a backup in case of emergency, plus short distance motoring like in and out from marina, anchorage like that. I don't think I ever enjoyed motoring anywhere in any distance with a two cylinder diesel so I will try to avoid in the future anyway. 

Obviously on a larger vessel have a bit more importance of the "motoring" capability and I understand it better to do on the most efficient way. So I guess I have one thing left, to pick the brand...

Tough one... Gori, Bri-Ski eventually same price, roughly same lead time... hmmm...

[Battleship 100]

Have used both Kiwi props and Two blade folders. For a racing yacht I would go for a geared folder.

For mostly cruising I would go with Kiwiprop.

I have always found the Kiwiprop guy very helpful.

We are now on our third keeler with a Kiwiprop. You have to be aware if they get dirty they can really load up in reverse I have found you need to get the revs up quickly soon after engaging reverse gear. For reversing and maneuvering the boat when there is a bit on they are very good.

A two blade folder will often struggle to reverse into a bit of wind and chop.

[John B 108]

Fish the other factor is blade area and shape- there are just too many variables to make a definitive decision from a magazine test, prop sizing is part calculation, part guessing and part experience which is why prop manufacturers and suppliers have extensive databases of end use. The best thing is to talk to lots of people, there is a font of knowledge out there  especially other owners of the same boat but even then its not 100% perfect. Different engines have different power curves, there are many gearbox ratios to choose from and is it shaft or saildrive? Then its whether the boat is loaded like a cruiser or is it stripped out and 800kg lighter, does the owner thrash it and even then there are misunderstandings about what that means!

 

I am not a big fan of the kiwi after I saw one on Tucana that had a serious infestation of electric sea mice, they changed it to a bronze folder.

To be fair Tucana ran that prop for a number of years and it was fine. But the trust had a new policy to run the boats without anodes and the shaft anode was removed, So something else got et instead, the body or boss of the propeller. I think that happened in a season or 1 1/2 seasons, my son was running the boat and I can remember pestering him to get it hauled.

 Anyone like to see it? I have it in the shed at home.

 Kiwiprops are inexpensive feathering propellers . They run smooth and you can adjust the pitch. Fine tuning the pitch to suit the powerplant and boat is invaluable I think. You just have to be on top of the maintenance as referred to earlier, and be careful with that reverse pitch thing they can do . 

 I actually removed a 2 bladed feathering seahawk ( which is now autostream?)and replaced it with a kiwiprop because it never balanced properly. The seahawk was powerful and did everything it should . The kiwi prop did not perform any less than the seahawk.  Ie no change in power/ performance , but smoother. 

 I noticed that sometime after I owned my seahawk they developed a stainless 3 bladed prop  and I suspect that is able to be balanced properly. dammit.

 Now I have a maxprop  and that thing is a really nice unit provided again , it is maintained by  greasing it every haul. I suspect it is 20 years old, its nice.

[Fish 0]

To be fair Tucana ran that prop for a number of years and it was fine. But the trust had a new policy to run the boats without anodes and the shaft anode was removed, So something else got et instead, the body or boss of the propeller. I think that happened in a season or 1 1/2 seasons, my son was running the boat and I can remember pestering him to get it hauled.

 

What sort of hill billy banjo playing 6 fingered er, people would have a policy to run boats without anodes? I'd be impressed if Auckland Council could even come up with such a nonsensical policy. Yes there is over protected, which can cause issues on wooden boats, and there is under protected, as in none, which will destroy key mechanical equipment rather quickly, case in point.

 

I am not a big fan of the kiwi after I saw one on Tucana that had a serious infestation of electric sea mice, they changed it to a bronze folder.

I'm sorry native, but that is a tad irresponsible saying a certain prop has an electrolysis issue, when you neglect to mention the backward facing 'no anodes' policy. Doesn't help your credibility much. Its like completely ignoring all the maintenance instructions, or doing the opposite to what is required, and then bitching that it broke...

[harrytom 679]

Never had an electrolysis problem with kiwi prop,zinc on shaft,ali hub properly etched primed with ali antifoul,had to do 3 times in 12 months but no sign of corrosion,never bothered antifouling blades as found anti foul never really stuck,coated 3 times  year in lonlolin and prop speed not a fan as to many factors enter the equation as applicator stated not a guarantee it will depending on who has what moored near you.

[nagy592 21]

Hm... one more question, just to be sure, if I go for two blade propeller from three blade, should I consider to make any extra shaft support, or different type of bearing? I can imagine with less blades, less balanced run, increased wear on bearings. I'm confident I'll  go for two blade folding if I have enough space.

[vic008 17]

2 blade on trademe today

[nagy592 21]

Thanks, I saw it. I'd rather go for a new.

[Battleship 100]

You shouldn't have to reinforce anything for a 2 blade, while generally not quite as smooth as a 3 blade prop unless they have had a shocker with the balancing it will be acceptable.

[nagy592 21]

You shouldn't have to reinforce anything for a 2 blade, while generally not quite as smooth as a 3 blade prop unless they have had a shocker with the balancing it will be acceptable.

Thanks I wasn't sure.

[Jon 395]

New Brunton Varifold 4 blade 20/14 going on Wednesday hopefully and going splash Friday if anyone wants to have a look. Pier 21

[windmill 1]

Hi everyone,

We're seeking a 16x11 LH folding prop to fit to a Volvo 120S saildrive and 18HP engine, on a Farr 1020.

Thank you

[alibaba 80]

Kiwiprop every time for me, I've had two on different boats, and the latest boat [ Lotus 9.2] had a two blade folding when I bought it, and the prop walk was horrendous. Kiwiprop has solved 90% of it,  now manoeuvring is easy. The other reason I like them on a saildrive particularly, is that the clutch on the Yanmar 20 is a "crash" clutch and so the load goes on almost instantly. The old two blade folder has a massive centre boss, must weigh Kgs, and the sudden change in momentum from stationery to moving must be a huge strain on the gears. The kiwiprop, plastic blades and light central hub would reduce the load greatly.

2300 rpm gives me a comfortable 6knots. plus - local manufacturer, instant spare part service, pick it up yourself, and John is always very helpful

 

[Fogg 427]

I can never get my head around a mission-critical component like a prop being made of plastic when plenty of good metal options exist.

[Island Time 1,284]

Lets see, plastic - no electrolytic corrosion (saves anodes as well, less immersed metal), light, cheap, easy to replace blades....

[Fogg 427]

All of which is great until you run over a piece of debris that a metal prop would take in its stride...

[alibaba 80]

and then, with a metal prop - off it comes, to repair the dings and rebalance. Kiwiprop - buy a new blade for around 150 or less, fitting takes 15 minutes, and can be done underwater by a diver. Tap out a stud, slide new blade on.