Feathering vs Folding Prop

[philipl]

I have a fixed 2 bladed propellor on my F38. I am thinking of switching to either a folding or feathering prop in order to improve my sailing performance. I only race occasionally so I would only switch if i could get an extra half to one knot in performance. Would like to hear from others who might have done the same on an F38.

[daletournier]

Hi Phillip, just went through this exercise. If you look back a couple of posts youll see what I wrote about my new Kiwi Prop. I ended up choosing feathering over folding as generally feathering have stronger thrust in reverse ( not all of them ). As I cruise theres been a couple of occasions were I've needed to pull up fast so stopping power is important for me. Ive been very happy with my purchase. I seriously considered the Flexofold 3 blade folding prop, seemed reasonably priced, seems to have the highest top speed and good reverse. Also the Autostream feathering which i think is called the Martec in the US but it was $1500 more expensive than the Kiwi prop and there are qualities that the Kiwi had that i liked more. Im definitely getting better boat speed and are very happy with the forward thrust, better than the fixed 3 blade I had on it.
Cheers dale Tournier
Freeform F32
Cheers

[Hans]

I went through the same excersise with my F38. Replaced the 2 blade fixed one by 3 blade Kiwi prop when we bought the boat. Improved power forward and reverse immensely.
But there is also a drawback. Reason to switch back last year. The Kiwi is made from ferro and non-ferro material. This latter material ( nylon?) tends to swell in water after about 7-8 months. Giving so much friction in the reverse mechanism that good reversing is only possible when revving up higher then 1400. Not very good for the gearbox.
I had the prop brought back to the importer asking to find a solution. They tried three times without success. I keep the boat year round in the water.
The one winter I did'nt do so, there were no problems. Only after being immersed more the 7 months the problem starts ( every time). No difference in fresh or saltwater. When I would have known before I would have spent some more bucks on a Max prop. I did spent probably the money anyhow on repair trials on the Kiwi which lies as a spare aboard now.
When you sail only summer and keep the boat on dry land in the winter there should'nt be any problem.

Success,

[philipl]

Thank you for the information. Unfortunatley here in new England the boat is only in the water May through October. However you have pointed out one of the few advantages of that. I will look into the Kiwi Feathering prop.

[daletournier]

Hi Hans, I've never heard of this problem before. I've emailed John the owner of Kiwi prop to get his opinion on your observations as it concerns me, my boat is also in the water full time.

cheers dale Tournier
Freeform.

[Hans]

Hi Dale,

I would gladly know John's answer to you on my problem. It can be a 'one prop' problem only and I am the happy one to buy it ( in Canada btw). But unfortunately they have'nt been able to repair this in Holland.
Apart from this problem I was very satisfied with the Kiwi prop.

regards,

[daletournier]

Hi Hans, I did email John of Kiwi prop as obviously I don't want to have the problem you experienced, as my boat is in the water 100% of the time as well. I should say I have absolutely no reason for pushing Kiwi prop other than being satisfied to date with its performance, I'm sure there's many props that would perform equally as well. Please find Johns responding email below. Cheers Dale.
Freeform.

Dale,

Thanks for the update - I have no record of this issue as our Denmark sales are handled
as an agent of our Dutch agent - a situation we have argued against for this type of reason
in that these sorts of issues never get back to the manufacturer.

I think you will find that the issue is more about local dirty water conditions
from the shallow sandy environment and of course the unit will probably have been lubed
when out of the water - not when in.

People seem very quick to rationalize issues and then tell the world without a detailed analysis of the variables
and other possible interpretations.

The Nose cone for the last few years has been made of Glass filled Polypropylene ( Black colored ) and all the evidence
we have is that this material is 100 % water and hydrocarbon stable.
We have had no reported issues with over 1500 units using this material to date that I am aware of.

The very first units we produced had Acetal nose cones - which is not 100 % water stable and we made tolerance allowances for
that to cater for expansion.

We switched to a PETP nose ( White color ) ~ 2006 on the advise of our plastics engineer - which is 100 % water stable.

As we to my knowledge did not sell any units into the Netherlands other than with PETP and GF PP
both of which are water stable - I am very doubtful if the cause is expansion as described.

Far more likely lubrication and operating environment.

We have had issues with units in shallow sandy environments - particularly lock & river situations in Holland and surrounds
where the constant lock maneuvering and high sand content water create a situation where lubrication is critical.

As a result of this we have also added blue neoprene V seals at the blade root to accommodate blade movement in and out
and provide an improved seal to the earlier O rings which were not as tolerant of wear.

Difficulty engaging reverse can also be caused by excess spring tension - have a look at REVERSING ISSUES on http://www.kiwiprops.co.nz

With some 4000 units installed over 10 years - trust me we do not get this issue every 7 months of immersion - we wouldn't have a business.

I am pleased your unit is performing well.
Please keep us in the loop over time.

Cheers, John B

Phone: +64 9 5757 975 Factory: +64 9 5745 606
Fax: +64 9 5757 972 Mobile: +64 21 930 598

Web: http://www.kiwiprops.co.nz GMT + 12 hrs
e-mail: kiwiprops@xtra.co.nz

[Hans]

Thanks Dale,

For John's response, I'll mail him separately about the problem, unfortunately it's not as he supposes it is.
Will let you know how it ends,

[philipl]

Does anyone happen to know the specifications of the propellor on the 1990 F38 ( with the original yanmar 3GM30F). Shaft diam, gear reduction, etc. I assume it is right hand rotation ahead ? What size kiwi prop works best on the F38...diam and pitch.

[Hans]

Hi Philip,

Gearbox reduction is found on the gearbox and in the manual, prop rotation is normally to right going forward, shaft diameter on my F38 (1989 #120) is one inch,
Kiwiprop diam. 42 cm, pitch is set to 27 degrees.

Good Luck