Autoprop v Folding

[Dann]

I currently have a Volvo 3 blade prop on a Volvo saildrive which is pretty efficient both ahead and astern and gives good sailing performance, but after 9 years use is showing signs of wear. As we do a fair bit of motorsailing, I am considering an Autoprop. However, will it be as efficient as the Vovo folder under power alone or will I be trading one advantage for another. Comments please ?

 

[oldsaltoz]

I suspect the o9ld adage that no folding prop was ever as efficient as a fixed prop, and no fixed prop is as efficient as an auto prop.

This also includes performance when maneuvering or stopping in a very short distance.

Go to http://www.autoprop.com/ and select test results.

Avagoodweekend......

 

[gardenshed]

Get a feathering prop (max prop or equivalent)
why:
minimal drag when sailing
goes into forward or reverse very quickly and effectively when needed
easy to re-set pitch angle(blade angle when needed

if you go for a folding prop, they often don't flick open into reverse as quickly as you want it to so there is a delay between selecting reverse and you getting the effect that you need.

The autoprop should have most of the advantages of the feathering prop but will have (slightly) more drag than a feathering one

I've got a feathering prop and have sailed with a all sorts over the years but always found the feathering ones to be best.

 

[kengill]

Bruntons make the Varifold folding prop as well as the Autoprop and I've found the varifold to be excellent. also at about a thousand squids less there's lots to be said for the simpler approach. Reverse performance is excellent IMHI.

 

[Paulka]

I fitted a Kiwiprop last spring, and am enchanted about the result.
It completely changed - for good - the behaviour aof the boat when sailing, without any difference when motoring.

and ... it's cheaper than any other folding or feathering prop.

As usual : no connection other than being a satisfied customer.

 

[piscis]

I fitted a Kiwi last year it has transformed the boat's handling
under power. Astern she can stop on a sixpence.

 

[CSFenwick]

Autoprop drag is only very slightly more than a true (flat bladed) feathering prop although you do need to lock the shaft (a problem with some gearboxes). I saw some tank tests and from recollection a fixed 3 blade had a drag of about 400 Newtons (obviously varies with size), an equivalently sized MaxProp was 12N and the Autoprop was about 40N. Very slightly more than the feathering but still an order of magnitude lower than the fixed prop. FYI folders were the same as the feathering props. The difference when motoring was stark - the AutoProp was better than a 3 blade fixed and far better than a flat-bladed feathering prop.

Every prop design is a compromise somewhere but for me the AutoProp is the best all-rounder and I've been very pleased with ours.

 

[Paulka]

You are right, I should have mentionned that my former prop was a fixed blades one.
Thus no, or little difference when motoring with my new Kiwiprop.

 

[davidbains]

Autoprops are very good at motorsailing and better in reverse than other folders.
However if your gearbox has a higher ratio in reverse, then the extra coarse reverse pitch of a Kiwi prop is a revelation. Kiwis seem to have the lowest drag of any featherers since they align to water flow rather than shaft angle. I am very pleased with mine.
Autoprops for motorsailing although not cheap. Kiwis for sailing and affordability and reverse power.

 

[Sailfree]

Best prop for going forwards is a standard fixed shaped prop.

Best prop for motorsailing is an autoprop as pitch adjusts to work required but it hesitates most before going astern.

Best prop for minimum resistance when sailing is a folding prop. Modern designs improve astern performance but still "weakest" of all for astern power. Least likelihood of picking up a rope when sailing

Best prop for going astern is a feathering prop as blades completely reverse in direction. Has next minimum drag after a folding prop but flat blades mean it cannot be 100% as efficient going forwards. Kiwi prop is cheapest but astern pitch cannot be adjusted and limited in power ability.

On charter boats heavy use soon reveals the more robust designs. I only go for Varifold or the Variprop. Had a Variprop on last 2 boats and consider it the best compromise for my requirements, Can handle 75HP, Almost as good going forwards, in fact have found no decernable difference (does 10kts), Pitch both forwards and astern can be adjusted from outside prop for maximum efficiency for engine/hull characteristics (maxiprop you set pitch only during assembly). Best feature for me is the maximum power astern - can stop boat from 6kts in own length and maximum power to get off the putty. One boat on our fleet tried a Kiwi prop and gave up but others with light use like them. I get the impression that owners of 30hp engine and less are happiest with Kiwis.

As others have said all boats and all propellers are a compromise. I have difficulty believing advice from people that say Prop "A " is best in all respects.