Folding or Feathering Prop?

[AlexL]

Afternoon All.

I'm in the process of investigating extras for my new boat (a shiny new Hanse 371 - due in Jan '05). As its quite a quick boat it seems a shame to leave a fixed prop on it, but i'm not sure weahther folding or feathering is best? my walk around SBS yesterday got me info on a few props.
My engineering brain thinks that a feathering prop is more 'pure' from a theoretical prop blade shape perspective, but I'm a bit unsure about the feathering mechanisms.

Any body got any thoughts?

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[boatless]

Personally, and for much the same reasons as you, I'd go feathering - or the Brunton Autoprop.

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[Sailfree]

The feathering prop requires regular maintenance (greasing and normally an anode change). Depending where you are berthed the anode change could be every 6 months. The anodes are special and normally only available from the propeller supplier. Cost per kg of this anode is normally out of all proportion to your normal anode cost!
Most folding props I have seen (except the volvo) do not have an additional anode but rely on the saildrive/prop shaft anode.
While both will reduce resistance when sailing the blades of a feathering prop can still pick up ropes etc while the blades of a folding prop are out of the way!
The main advantage of a feathering prop is that it produces full power astern while a folding prop tends to also try to close when going astern. Could be important if you hit the putty!
Another factor to consider is if you want to fit a rope cutter. Rope cutters need to pick up drive and the one I bought required two hole drilled into the back of the propeller. Unfortunately their position was on the edge of the centre "boss" which needed to turn independantly from the outer boss/housing to enable the prop blades to reverse direction. With wear (1 year) these holes "necked" causing extra friction.
Whatever you choose make sure the supplier confirms it will be OK to also fit a rope cutter.
Finally if you have a Volvo saildrive/gearbox pray you don't have any problems with it - Volvo will state that fitting a non standard propeller caused the problem. If it is a Volvo it is safest to use the standard prop for the warantee period.
Happy sailing in the new Hanse.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by Sailfree on 12/09/2004 20:31 (server time).</FONT></P>

 

[AlexL]

its a yanmar 3ym30 saildrive - I'll have a chat with them and see what they say.

I did like the look of the autoprop at the show

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[GeorgeP]

Hi Alex. I have a folding prop which makes a big difference to sailing speed. (If it starts turning while sailing, I soon notice the drag.)

Hopeless in reverse though, and not much better going forward.



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[Sailfree]

My limited understanding is that Yanmar enjoy a better reputation (I believe Jeanneau have recently nominated them as their standard engine with Volvo now as the option)


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[ChrisE]

After much humming and ha-ing and advice from this board we bought a Brunton Autoprop. We are dead impressed. In light winds an extra knot and more directed power in reverse. Excellent pre- and post-sales service. Plus VAT knocked off price at London boatshow. Need I say more?

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[AlexL]

Chris - how often do you lift out to maintain it? and are the anodes a problem? I would like to lift out once per year max - maybe even strech to 18months

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[ChrisE]

We've only had the prop since March so can't give you a definitive answer but I believe that Bruntons recommend a once a year service to grease the blade mountings and to replace the anode which is sited in the centre of the rear of the prop.

I looked at ours after 4 months when we dried out alongside and it looked as though the anode, whilst pitted, had plenty of life left in it.

If you are going to SIBS pop into their stand they are an extremely knowledgeable and approachable lot.

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[snowleopard]

not quite clear on which engine/drive you have, the numbers don't tally - is it the 3GM30(C) with SD20 sildrive leg?

if so, the warranty condition is that a folding prop must have a rubber-bushed hub to absorb shock when engaging gear. any other type will get you into strife. the flex-o-fold claims to be the only one to meet this requirement though how true it is i don't know.

we were looking at brunton and maxprop but went for the folder for two reasons: the first two can bump-start the engine on a fast boat (17 knots plus) but more importantly the folder was half the price of the others, a big factor when you have 2 to buy!

don't worry about lack of drive in reverse with a folder, ours can stop the boat in its own length from 10 knots! given that i can't really see the benefit of the maxprop. if i were building a monohull i'd probably go for the brunton.

we haven't picked up a rope in 2000 hours of motoring, without cutters.

surprisingly the props do turn when sailing unless we leave them in gear.

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[AlexL]

The Engine is the 3YM30 which aparently is the upgrade / replacement / new version of the 3GM30 - i'm not sure which saildrive leg - I thought there was only one! I went to SIBS on saturday and am planning another visit next saturday having had time to research some of the info i've got. We looked at the autoprop and were impressed, and it seems to crop up alot on this thread so I'll have a more detailed look.

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[Miker]

I've had an Autprop for four seasons, including this year. It gives the extra performance as stated by Chris and what I like about it is that the boat handles better going backwards and will stop on a sixpence - a great help in a crowded marina.
When I take the boat out each winter, I remove the prop and change the anode. The anode might last two seasons (14-15 months) but I'd prefer not to chance it.
I've found that the prop needs an initial hard rev to get going and does not like plastic bags around it - a hazard in a marina next to a shopping centre - but what prop does!

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[Robin]

We have an older Brunton Autoprop with open bearings which came with our boat and very good it is too, it does everything it says on the box. We lift out every 12 months and simply bright polish the prop (and I mean BRIGHT) before launching, cleaning off with an old sail batten on lift out goes back to the bright finish. The 1st year our anode fell off beause it corroded around the mounting holes, Brunton advised putting a dab of paint in the mounting holes (we use Primocon) to stop this part of the anode wasting away first and since then the anode has lasted 12 months and with some left though we change it anyway, there is a normal pear shaped anode as well.

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[Miker]

My first anode had brass (?) bolts which caused heavy wastage around them. As you say, Brunton then advised putting antifouling around them. Last year I used the new Brunton supplied plastic bolts without any antifouling and found no appreciable wastage after eight months. Fingers crossed for this year!

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[Aeolus_IV]

If you go for a folding prop can I recommend the Gori 3 blade prop? I have a Gori 2 blade folding prop (I couldn't afford the extra blade /forums/images/icons/frown.gif) and this is every bit as good as the fixed prop it replaced, certainly much better in ahead and no worse in astern. The 3 bladed version is simply better still.

I also have a rope cutter installed - a "Stripper" - this requires no modifications to the prop, but a little extra space on the prop shaft between the p-bracket and the back of the prop.

The folding prop has certainly the lowest drag, but the Bruntons Auto-Prop must be the best "techie" solution optimum drive in forward and astern, and nearly as little drag as a folding prop. However, it does seem possible to "over prop" a boat with an auto prop as a friend has found out - this is something that he has to take up with Bruntons.

Regards, Jeff.

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[Robin]

Mine that fell off was fixed with the nylon screws but the paint idea seems to work.

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[Becky]

We fitted an Autoprop on Cornish Maid, and it seems excellent. The blades were quite stiff initially, but it works very well. Good speed ahead an astern, just needs a few secs to allow the blades to change when going into reverse.

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[Miker]

Thanks. I'll put a bit of antifouling on this winter - better safe than sorry.

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[bedouin]

I will second that - I fitted a Gori 3 bladed prop a couple of seasons ago and it is a stunning piece of kit. Although it is a folding prop in terms of it's characteristics (and price).

In particular it works better in reverse than almost any other prop, fixed or folding, and has less drag than any feathering prop (though that is probably not significant).

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