Folding and Feathering props

[uncledom]

I know I'm gonna get flak from at least three directions for this but I have a Brunton's AutoProp and love it.
It has free spinning blades that rotate on the hub. They require SPECIFIC MAINTENANCE. And anyone who has seen loose blades and heard a story of one blade going through a hull need to understand that they need to be serviced. The blades auto pitch depending upon rotational speed (centrifugal force) and water pressure on the blades. It has almost NO prop walk because it is at the correct pitch at all speeds and the blades orient themselves to direction. This means that in reverse they have the same variable auto pitch as they do in forward and no similar boat to mine with a different prop can stop faster or back up faster. Yep the boat does 7.5k forward and backward. Here is the coolest part, on those light wind days, for me that's less than 14 knots of wind, you can add a small amount of motor and reach hull speed without using much diesel. On days when the wind is say 8 knots I can hit hull speed with only 1200 rpm of power, way below cruising rpm. It really helps you tick off the miles and stay on target for time on trips when you need to. It was stupid expensive at 4k but I would buy it again in a minute. As a side note it is imported from England and the last group of gentlemen on this side of the pond that represented it were not the sort I like to deal with. A new dealer has emerged in VA. and seems to be much more customer focused and I would not hesitate to deal with him for anything. King Propulsion has helped me out already and was not the company that made the original sale.

 

[seadaddler]

I will repeat that having my3 blade Flex O Fold since 2008 and just love it and very little maintance other than cleaning barnicles off needed and every 3 years when I
do a bottom job I do take just the blades off and give everything a good cleaning with wire brush on portable drill.
I have never had any kind of problems,a few years ago this 1 time I left my boat here in Florida's very warm water for
3 months and when I came back the prop was loaded with barnacles and did not work properly but after diving under and cleaning everything was back to normal and I paid about$1600.00 and now see in sail Mag for $1900.00
Nick

 

[Jerry Clark H356 SV Persi]

I have a MaxProp and have 1292 hours on it mostly in fresh water, but about 4 months in Florida since March 2003. At 1275 hours I sent the prop back to MaxProp and had it refurbished at a cost of approximately $750. I am experimenting with a different setting and probably will go back to the original this summer. I have been very pleased with the MaxProp and the service and expertise at PYI is outstanding. I had wear that caused some vibration as well as I hit something that slightly bent one of my blades. After the refurbishment, I have no issues and it is again smooth as silk. I also changed my cutlass bearing at the same time. I back into my floating dock and enter thru our stern. The MaxProp is very responsive and I use the prop walk in backing in and reverse the prop to stop. You do need to grease it annually and that can be done in the water.

 

[barnstormer]

The cost of the Kiwi is certainly appealing and I haul out every fall so maintenance is simple . However, it didn't perform very well in the test that @Davidasailor posted http://www.yachtingmonthly.com/gear/folding-and-feathering-propeller-test-29807 Seems like a J-Prop might be the way to go...per the usual its in the top price bracket. The Flex Fold 3 blade seemed to preform best at top motoring speed and was middle of the pack with regard to stopping and astern performance...a nice mix really.

In case you didn't see the add in the gear add section, someone has an autoprop that is one year old that is made for your engine at half the cost of new that might work for you.

 

[freeheelbillie]

In case you didn't see the add in the gear add section, someone has an autoprop that is one year old that is made for your engine at half the cost of new that might work for you.

I think I looked at that one...this is the response I got directly form Kiwi Prop after filling out their quote form;

Billie,
Your engine/transmission setup will take our 15.5" x 20 degrees 3 bladed
Kiwiprop.
You mentioned you would prefer a 4 bladed Kiwiprop though the smallest 4
bladed we have is a 16.5' and your engine HP and transmission reduction
at 2:1 would not have the power to handle the 4 bladed Kiwiprop.

For your engine rated 23 hp @ 3200 RPM
with reduction ratio 2 :1
that will deliver 1600 shaft rpm.
We will recommend 15.5" x 20 deg Kiwiprop
Kiwiprop diameter at tips ~ 1/2" greater than nominal.
Required clearance to hull 1/2" (12 mm).

 

[freeheelbillie]

In case you didn't see the add in the gear add section, someone has an autoprop that is one year old that is made for your engine at half the cost of new that might work for you.

I looked, can you post the link please?
Thanks

 

[barnstormer]

I looked, can you post the link please?
Thanks

https://catalina.sailboatowners.com/gear/gear.php?task=showad&id=6158

 

[freeheelbillie]

https://catalina.sailboatowners.com/gear/gear.php?task=showad&id=6158

Thanks!
What say the crew? Is this a good prop and decent deal? I can get a brand new Kiwi Prop delivered for 1,500.00

 

[uncledom]

You need a special grease adapter tool to lubricate the blade bearings. I might think about sending it out, which equates to back to England, to assure it is in good shape. The price is excellent and as I said I would repurchase mine in an instant.

 

[seadaddler]

I think some one had one of the Kiwi blades damaged and just wondering how much to replace these some kind
of composite blades and needs to be greased often.
How long do they last from use wear and tear and just asking from some one who has one,just saying my FOF is over 10 years old and I have been retired and been using my boat heavy duty and my FOF is still like new and never need to grease it and doing bottom job as we speak and will take photo.
Nick

 

[JohnShannon]

I think it is on the order of $100 for a Kiwi prop blade I had mine 6 years till I sold the boat probably motored for 500 miles no problems YMMV. I think you can change the blade underwater the construction is super simple blades that flop around no gears or anything forward pitch adjustable by set screw reverse pitch is fixed and fairly coarse. Hub is SS and blades are some sort of plastic (I mean engineered composite)

 

[chuckwayne]

Ditto on the autoprop! We've had ours for 14 years and it's as good as uncledom says.
I've always found AB marine to be helpful and responsive. Also , note that the prop is made in England and the price depends in part on the dollar - strong now.
Maintenance consists of annual greasing and checking that the bearings are set properly - a nut and lock washer under the round caps. the grease nipple and spanner for the cap are inexpensive; I bought a spare bearing and seal set to have on board and this year I'm disassembling the prop for a full cleaning and maybe bearing and seal replacement.

 

[SG]

I'm not if there was a question in your original post, Dom?
We have had a two-bladed Max-Prop for 19 years on our J/Boat. As many know, it's "self-feathering" and when you "pop one" in reverse (on almost all transmissions) it will feather.

We have the boat dived every several weeks during the season in Annapolis. When we're in New England on summer cruises we sometimes have the boat bottom wiped-off every three of four weeks. The Max Prop is checked-over every two years when we have the boat's bottom redone.

We'd by a Max Prop again and recommend it highly. I've heard a lot of good things about the Flexifold Gold folding props.

As for your comment on "no prop walk"....I'm not sure about the physics of that :^)))) Can you explain how that could be so?

 

[uncledom]

As for your comment on "no prop walk"....I'm not sure about the physics of that :^)))) Can you explain how that could be so?

I can't really explain it except to say that prop walk is caused by the difference between the force of the prop and the actual direction the prop is traveling. The prop is a screw, it will move forward through the water as a screw through wood the amount of pitch per revolution. Unfortunately the prop is not aligned to the exact motion of the boat. The blades are at an angle to the actual direction of travel and this difference causes a paddle wheel effect due to the misalignment of the rotation to the true direction of travel. The Autoprop is self pitching and also aligns it's self to the actual direction of the boat not the angle of the prop shaft. It screws itself through the water at whatever pitch the balance of rotation (centrifugal force) and water pressure bear upon it. I would like to take a GoPro video sometime this summer and film it. That would make a great video to post here. I don't know if this explanation helps but I can tell you that I only have prop walk until the prop settles which is a second or two.

 

[SG]

First, don't go under the boat and film it -- You'd be amazed what can happen with a prop pull or push you. Seriously, it's dangerous down there when anything is moving. ;^)))

I think that the simple explanation is: Until there is sufficient flow either push or pull the boat (and/or water across the control surfaces, usually the rudder on a sailboat) the boat will be "paddled sideways". (i.e., "Prop walk")

Some boats with large rudders and that are driven easily have little prop "walk" -- while others seem to less affected by the sideways motion. It is affected by the speed in which you apply the force; and, it's often more noticeable when the boat is put in reverse.

Heavy boats with very long keels and relatively small rudders seem to me to display the tenancy to prop walk a lot more than our fin keeled J/Boat. Our deep and big rudder extends to over 6'-6" below the surface. I still will notice the phenomenon if I get too aggressive in reverse. Generally, less aggressive maneuvers seem to be display less "walk" for us.

 

[uncledom]

When there was a fixed three blade I had PLENTY of prop walk. It was difficult to reverse using the Autoprop at first because I was counting on the walk. And I will surely not be under the boat for the video, thanks, I will arrange a mount for the camera.

 

[Solstice]

I know I'm gonna get flak from at least three directions for this but I have a Brunton's AutoProp and love it.
It has free spinning blades that rotate on the hub. They require SPECIFIC MAINTENANCE. And anyone who has seen loose blades and heard a story of one blade going through a hull need to understand that they need to be serviced. The blades auto pitch depending upon rotational speed (centrifugal force) and water pressure on the blades. It has almost NO prop walk because it is at the correct pitch at all speeds and the blades orient themselves to direction. This means that in reverse they have the same variable auto pitch as they do in forward and no similar boat to mine with a different prop can stop faster or back up faster. Yep the boat does 7.5k forward and backward. Here is the coolest part, on those light wind days, for me that's less than 14 knots of wind, you can add a small amount of motor and reach hull speed without using much diesel. On days when the wind is say 8 knots I can hit hull speed with only 1200 rpm of power, way below cruising rpm. It really helps you tick off the miles and stay on target for time on trips when you need to. It was stupid expensive at 4k but I would buy it again in a minute. As a side note it is imported from England and the last group of gentlemen on this side of the pond that represented it were not the sort I like to deal with. A new dealer has emerged in VA. and seems to be much more customer focused and I would not hesitate to deal with him for anything. King Propulsion has helped me out already and was not the company that made the original sale.

Agree with everything you say! Had an AP for 12 years and absolutely loved it. Really the perfect prop. Unfortunately the prop will not fit on my current boat as I have a partial skeg. Some of the old stories about blades flying were few and far between and they did redesign the pins. Also agree with you on the original distributor....

 

[fstbttms]

First, don't go under the boat and film it -- You'd be amazed what can happen with a prop pull or push you. Seriously, it's dangerous down there when anything is moving. ;^)))

Having observed props spinning from close by underwater many times, I can tell you that if you use caution and stay four or five feet away from the prop, it is not particularly dangerous.

 

[chuckwayne]

there is a good animation of the autoprop on the web, I think either the bruntons or the distributor website...