Folding prop replacement? Suggestions.

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paulwitney

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I have a two bladed folding prop which may be past its useby date - 22 yrs. Have patched worn pads where blades fold out to and close to with epoxy stick over the past two slips but this only lasts a max of 6 months. Then it is a juggle between forward & reverse to get both blades out. What's around that works and is good value? Shaft is 1 inch and engine 18hp volvo in 33ft yacht.
 
Haven't got one but I like the look & price of the Kiwi Prop and it has good reports performance wise from users- but don't know what an Aussie would make of the name tho! /forums/images/graemlins/grin.gif
 
Like these ones from VP site:
Propellers for S drives, 2-blade folding, bronze


45.13




Pos no. Part no. Ø x Pitch Engine
45.13 38585071) 14 x 8 MD2010, MD5B*, C, 2001, MD7A
45.13 3858508 15 x 9 MD2020, MD7B, 2002, MD11C
45.13 3858510 16 x 11 MD2030, MD11D, 2003, MD17C
45.13 3858512 17 x 14 MD2040
45.13 38585062) 14 x 6 MD5A, B**
45.13 3858511 17 x 13 MD17D

1)* Gear ratio 2:15.
2)** Gear ratio 1:66.
 
Because I had one replaced 2 times, never lasted more than 12 months on our 1st charter boat.

Volvo in the end gave me my money back which seemed an acceptance by them that they dont last the number of hours a charter boat puts on them - OK for light usage!

Likewise on 2nd boat the Volvo engine (middle cylinder seizing) but so many of them Volvo didn't want to know - could not afford to recognise that there is a problem? Gearbox changed once, water in saildrive leg 3 times.

Sold my Volvo problem now and new owner had continuing problems but he has now solved it completely - Changed complete engine and saildrive unit for a Yanmar! Drastic - yes but boat now has no cancellations/loss of income on the charter market.

For low power engines, private use I would suggest a Kiwi worth trying but i have no personal experience. If more power or heavy use go for Variprop as has a cushion effect in changing direction, comes as an assembled unit - just slide on and pitch can be adjusted from outside(as Kiwi). Darglow Maxiprop has pitch adjusted as you build it on the shaft and different hub for heavy usage.

I have had 2 Variprops on charter boats and no probs. Other charter boats I know report same.
 
Kiwiprop

Installation
2005 Jeanneau Sun Odyssey 35, Lifting keel, Twin Rudders, Yanmar 3YM30 engine with 2.62:1 reduction, LH.
Vessel is always loaded for cruising, and is thus low in the water,


http://i4.photobucket.com/albums/y128/jimdew/Jeanneau/Kiwiprop.jpg

Purchase price £795+vat all sizes

Documentation prior to delivery:
4 page diagrammatic requesting all vessel required details, and also current prop.
Simple, clear concise, no specialist knowledge required

Communication prior to delivery.
Order confirmation call,
Order despatch call., request if the greasing kit required.

Delivery
On time, with greasing kit (optional).
Robust packaging


Instructions
Owners Documentation, fitting instructions and warranty cert details included, in plastic sealed wallet.
Good photographs and details. Simple, clear concise, no specialist knowledge required
However, this could be improved if a clear acetate protractor template was included to be able to check blade angles.

Construction
Good quality stainless machinings to an acceptable finish. End stop faces for blade adjustment are not a machined surface, appearing to be an as forged condition. Tolerance not known, but appear to be similar for each of the 3 faces.
Blades are preassembled to hub and cut to length for arc of swing. Blades are factory adjusted for calculated best performance angles.
Blades appear to be uniform within a good plastic tolerance. Not individually weighed.
Grub screws for adjustment, and bush pins for blade retention appear to be of good quality.
Bush pins are an interference fit in the Zytel blades, passing through a machined shoulder in the blade hub spigots. These are robust, as I changed my blades. No looseness.
Retention hub for unit is good quality, and locking allen key feature is good fit to tool.
No prop mounted anode (standard on Jeanneau fit)

Installation
Removal of existing propeller took longer than installing new one.
Tapered hole in hub, keyways and keys good alignment fit.
Hub retention lock fitted and the unit locked at correct point on the shaft at top of taper.
Supplied grease was used, no issue.
Added extra grease to blade spigot nipples, all blades free to rotate about spigots, no binding.
Total installation time, less then 10 minutes with checks.

Note: I installed an Ambassador Stripper at the same time, which required a 10mm spacer in the shaft joint to gearbox. All items interfaced well.


Antifouling.
I used International Trilux, 3 coats.
Instructions advise not to cover screw adjustment faces.
After 8 weeks, some barnacle on the stainless areas, but not on the blades. (River Crouch, high fouling year)
After 8 weeks, blades free to rotate to correct angles.


1st Performance trial, motoring
Initial bite going into forward gear is a bit slower than 2 blade fixed (Standard Radice 16x13). More engine revs needed to start acceleration. Back off after reaching steerage speed, probably 2 secs difference.
Logged performance using differential runs upriver and downriver on a very light airs day, no more than 3 knots true.
Using Log speed and SOG on GPS in 2 directions at 2000, 3000, and 3650RPM
At 2000 the 3 blade was 0.6kts slower than fixed
At 3000 the 3 blade was 0.8kts slower than fixed
At 3650 the 3 blade was 0.9kts slower than fixed
Reverse bite is very quick, better than fixed. Much reduced propwalk. Performance in reverse limited to 5.5kts as the wave entered the cockpit through the sugar scoop transom. More available for the brave/foolhardy. This design engages full maximum blade pitch in reverse as there is no blade angle adjustment for reverse.

1st Performance trial, sailing
Very good in light airs tacking, allowing much improved acceleration out of tacks
In 10 knots upwind, performance improved approx 0.25 knots.
Downwind similar performance increase.
No noise, vibration or propshaft rotation observed.

After trial, Vectamarine contacted to discuss performance. We agreed an increase of 1 degree to 23 degrees, and an increase to 16.5” from 16”. Blades were manufactured and despatched at no further cost, in approx 4 days. The data programme possibly did not take into account my hull form and keel arrangement.

Unit was dissembled using small hammer and 5mm punch after drying out on local beach. 3 blades removed and replaced in 90 seconds.
Forgot the protractor, so relied on visual chaeck of blade angles. (Bad idea as it turns out).

2nd Performance trial, motoring
Initial bite going into forward gear is a bit slower than 2 blade fixed (Standard Radice 16x13). More engine revs needed to start acceleration. Back off after reaching steerage speed, probably 2 secs difference. No change from 1st trial
Logged performance using differential runs upriver and downriver on a light airs day, no more than 5 knots true.
Using Log speed and SOG on GPS in 2 directions at 2000, 3000, and 3650RPM
At 2000 the 3 blade was 0.3kts slower than fixed
At 3000 the 3 blade was 0.5kts slower than fixed
At 3650 the 3 blade was 0.5kts slower than fixed
Small vibration observed, probably due to poor alignment of blades post change. No opportunity to correct alignment yet.
Probably performance will equal the fixed blade after correction

2nd Performance trial, sailing
As 1st trial. Impressive.


Observations
No dissimilar metals in shaft/prop assembly. Good for corrosion prevention.
No gearbox or other moving parts to go wrong
Zytel blades are damage/impact resistant but have good elastic qualities.
Simple greasing as maintenance.
Needs clear plastic purpose made protractor to quickly check angles of operation.
Excellent sailing performance
Equivalent motoring performance.
Excellent value for money
Only available up to 55hp engine use
UK concessionaire excellent service
 
I guess it depends upon your wallet and specific needs. We have a Brunton's Autprop which cost about twice that of the kiwiprop. Gives similar performance gains under sail as the kiwiprop and more speed for less revs under power (6.5 knots at 1800 revs, as opposed to 5.5 before).

Pre and post sales performance very good.

You pays your money and you takes your choice.
 
I have just used my Kiwi prop for it's first season.
Am reasonably impressed since my 40ft is underpowered with one 2GM20.
Motoring speed increased about 0.5kts.
Reverse frankly incredible, the coarse reverse pitch matching the reverse ratio and giving powerful accelleration and little prop walk.
Sailing speed is improved noticeably,perhaps by 0.75 kts.
It seeems fairly robust, the Delrin blades are strong enough IMHO.
It's great benefit is that the blades align with water flow rather than shaft angle.
I also feel that the rudder benefits from being fed clean flow water.
 
Sorry for the mishaps You had to experience.
I averaged 100/150 hours a year and, except scaling in the seawater cooling part, quickly solved by a bottle of acid, never had a problem with engine, drive and propeller; maybe because they were 1980's units.

Now I have a Yanmar 54 hp (larger boat) which pisses seawater from antisiphon walve and dealer can't cope with it.

Cheers
 
I have a 40 footer with a Yanmar 4JH4E (55HP) It was fitted as standard with a volvo 3 blade folder. Prop looks very nice with very hooked blades and is supposed to give reverse thrust similar to a fixed prop.
Under sail goes great, shaft turn initially but pop it into reverse to lock it and then back into neutral and it stays staionary. Under power she goes well, accelerates quickly and runs smoothly with little vibration. Stick it into reverse to stop the boat and nothing, increse revs, still nothing, max revs - has the prop fallen off? No wait somethings starting to happen - the sterns going to port - a long way to port - still not slowing much! From around 2 knots fwd requires about 30 secs of full reverse to bring boat to a stop and about 2 boat lengths. From stationary to getting underway in reverse require max revs for about 10 secs to get about 1/2 knot of reverse speed and then knock into neutral to overcome propwalk - during which time boat has rotated about 90 deg to port.

Mostly due to high redn ratio in reverse of Yanmar box (3.21) means prop only spins at about 920 rpm so blades dont fling out enough. Probably OK for someone with saildrive which has same ratio fwd as rev, or a shaft drive with a lower redn ratio. - Getting it's marching orders for me.

Have considered Kiwi but have concerns as my engine is at the top of it's HP range. Unfortunately the social secretary doesn't see the point in spending money on something she cant see - even if it looks pretty!
 
Bonny,
You are describing exactly my first month experience with the Oceanis 393: I used to define it a "mule" for her kindness in reverse.
So I summoned the Club retired coxswain and in two mornings he worked out all my insecurities and doubts on manouvering in reverse and in close quarters.
Trick is to anticipate the manouvering (say, as the point around which I want to turn is halfways between bow and mast), to use half full reverse throttlewith rudder all the way to the side the prop wash would push the stern and use WITOUT MOUVING THE RUDDER a series of forward pushes to correct the astern progress (ehr, regress in english? Sorry for my pidgin folks).
Now I can turn the boat left or rifht, forward or reverse, within her lenght.

Technically one of the causes is the false keel which hosts the propeller axis and mahes the boat very stable (forward and backward!).
Cheers
 
One of the major factors in choosing a Variprop on a charter boat is that if someone messes up either berthing or putting it on the putty the power astern is fantastic. 6kts to stop in one boatlength.

I did not appreciate that the Kiwi prop is not pitch adjustable astern. The pitch on the Variprop can be adjusted from outside for both forwards & astern.
 
I've used Gori propellors on two boats, good product and good service from their UK agents Sillette . I gave them my old prop and they copied the taper and keyway. Fitted like a glove. Gave an extra .75 kt flat out.
 
gianenrico,
Amazing, how did you know I also have a mule? Yes it's a 393. I've had it about 18 months and have done a little over 2000 miles, with very little use this year. I have become aware of the limitations and often use some of them to my advantage, particularly the port propwalk. It's only when berthing that problems can arise. On one occassion I had to berth at the bottom of a long leg and I knew the only way to do this was to use the propwalk to move the boat sideways through the entrance and reverse all the way down the leg ~200m and then turn sharp to stbd to lie alongside, went perfectly and the harbourmaster commenetd - by god you've done that before - you could teach a few of our berthholders how to do it forwards! Little did he know that if i'd done it fwds I'd have finished in a crumpled mess at the bottom because I couldn't have stopped with a tail wind.

If the conditions are in my favour - no prob. If the conditions are against me, or I'm not sure where I'm supposed to berth, that's when things can go wrong - and sometines do. I just want to limit my damage limitation.
 
Jim: this ties in perfectly with my observations.
I've put a RPM meter on the propshaft and did 50 + measurements on it, since I found my KIWIprop about 0,5 - 1 knots slower then my old 2-bladed prop. The dealer informed me this was normal, since the manufacturer "always sets the speed so hull speed is reached at near maximum engine RPM's, whereas in Europe, we prefer to reach hull speed at 2200 - 2400 RPM."
I have to return the prop anyway to have the reversing mechanism modified, and the dealer will adjust the speed accordingly.
 
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