New propeller??

[tel1]

although i dont really need it im thinking of getting a new prop. ive fitted a new engine which was a bigger horsepower than the last, but after a test the other day it doesent seem to be to bad. the only real reason i want one is the fact i would like a folding prop. more sailing speed. my question is.

is it worth it??? do they do folding props for 78hp engines?? how do i work out how big the prop should be? what the pitch should be etc etc

any help would be very usefull

merry xmas!

 

[emandvee44]

propellers

The simple answer is, yes there are many folding propellers which you could buy, and in fact a review of folding props was done in either PBO or YM recently (I haven't got time to look it up 'cos I am trying to prepare Christmas lunch so that SWMBO can enjoy a sherry or two)

We have a 3 blade Bruntons auto prop on a 55hp Volvo saildrive, and apparently the yacht speed increased by about 0.75 kts after fitting (over the original 3 blade fixed)

Have a look at the websites - perhaps a google search of "folding props" would do it.

Must get back to the kitchen,

Cheers and Merry Christmas,

Michael.

 

[tel1]

if anybody knows what magazine the review was in please let me know!!!

i think im going to treat the boat to a new prop!!

 

[stevebirch2002]

Contact Paul Bell at First Marine Propulsion. He will tell you all you need to know. Nothing to do with the company, just a very satisfied customer.

Telephone: 023 8022 5944

http://www.1stmarine.com/aboutus.htm

Steve B

 

[NormanS]

although i dont really need it im thinking of getting a new prop. ive fitted a new engine which was a bigger horsepower than the last, but after a test the other day it doesent seem to be to bad. the only real reason i want one is the fact i would like a folding prop. more sailing speed. my question is.

is it worth it??? do they do folding props for 78hp engines?? how do i work out how big the prop should be? what the pitch should be etc etc

any help would be very usefull

merry xmas!

If you ever do any motor/sailing, go for a Brunton's Autoprop. Fantastic, but not cheap.

 

[oldfatgit]

On previous boat fitted a 3 bladed Brunton's Autoprop which I ordered direct from the company. I reckoned it resulted in a 20% increase in speed whilst under sail and significant saving in fuel through running at lower revs. Particularly good when motor sailing. Would have fitted to new boat but long keel with a fully attached rudder made it impossible so went for a 4 bladed Variprop sold by Brunton's under licence from a German company.

 

[johndove]

Always before careful with a folding prop on saildrives,

weight factor. a folding prop about 5 kg more in weight than a fixed alloy prop!

Can cause problems with sail drive and cost loads to sort!

 

[Coaster]

Another vote for the Bruntons' Autoprop. Particularly good for motorsailing.

 

[shaunksb]

Fitted a bruntons (2 blade) prop earlier this year - noticed a couple of things.

1) yes better speed through water. 20% ish
2) No point at all though if you don't keep bottom clean (the boats!)
3) better drive under power (as said in ym test)
4) worse performance in reverse (as said in ym test)
5) reverse not a problem - just need a few more revs - no extra prop walk
6) If shaft drive like mine - boat also points better - now that prop doesn't disturb water flow over rudder the foil is much more effective. This was a big surprise and poss one of the best benifits.

wish i had done it before

 

[emnick]

New prop

Pretty sure it was YM who did the prop test. I cant remember when though.

I was contemplating fitting a Ki-Wi prop at the time. Being East coast based, it would seem that the considered opinion is that a Ki Wi would jam due to lots of muddy water etc so I shelved the idea.

Good luck with it.

 

[Ex-SolentBoy]

I have just fitted a new prop to our 85hp engine. We did all the calculations ourselves, based on the formula's in Nigel Calder's book. I then went on the internet and downloaded several free prop calculalators. I also asked 2 propeller manufacturers to do the calculations. fortunately, we all came up with the same answers as near as dammit.

I would recommend you download one of the calculators. Getting the right size is important as otherwise you waste power, waste fuel or damage the engine.

By inputting boat dimensions, engine power, gearbox ratio's etc, all the diameter and pitch calculations are done for you and you then know what the recommended fixed pitch size is. That is vital data when you start talking to manufacturers of folding props.

FYI we have a Max-prop. Very pleased with it.

 

[DaveS]

Always before careful with a folding prop on saildrives,

weight factor. a folding prop about 5 kg more in weight than a fixed alloy prop!

Can cause problems with sail drive and cost loads to sort!

This might be true of folding props (but VP also sell folders for their saildrives so is it really an issue?), but isn't necessarily the case for feathering props. I replaced the fixed 2 blade alloy prop on my VP saildrive with a 3 blade Kiwiprop featherer with little or no weight increase since the heavier SS hub is outweighed (groan) by the plastic blades.

 

[dulcibella]

Bruntons may not be universally the best thing. After considerable trouble with mine (3-bladed) on a Rustler 36 (rapid bearing wear, vibration etc even after a refit by Brunton) I discussed the problem with Rustler while having other work done by them. They said that this sort of thing had happened with a number of Rustlers so they were no longer recommending fitting the Brunton. On their advice I replaced with a Featherstream which (so far) is much smoother and very effective. No inherent criticism of the Brunton but perhaps there is something about water flow round the prop aperture in this particular boat that doesn't allow the Brunton to behave properly?

 

[Tranona]

although i dont really need it im thinking of getting a new prop. ive fitted a new engine which was a bigger horsepower than the last, but after a test the other day it doesent seem to be to bad. the only real reason i want one is the fact i would like a folding prop. more sailing speed. my question is.

is it worth it??? do they do folding props for 78hp engines?? how do i work out how big the prop should be? what the pitch should be etc etc

any help would be very usefull

merry xmas!

There are broadly 3 choices.

The first is a folding prop, but generally speaking there is a loss in motoring performasnce, but the greatest gain in drag reduction. 3 and even 4 bladed folders have come on the market to improve motoring performance.

The second is a feathering prop with geared blades, some of which can be adjusted for pitch. Traditionally this type of prop has been considered the best compromise of performance and drag. The self feathering Kiwi prop does not go big enough for your power.

The third is the self pitching Bruntons Autoprop - much loved by people who do a lot of motorsailing.

All are expensive compared to a fixed prop and whether it is worth it depends on your priorities. However they have become very popular in recent years so the number of types available has grown - perhaps adding confusion for buyers! All you can do is get all the manufacturers information and recommendations and make your own decision. As you see already you have support for all types if you ask on the forum.

For size, download the Propcalc programme from Castle Marine to work out the appropriate sizes. Use this as base information but when you buy use the supplier's recommendation so that if it is wrong they are responsible.

 

[Vamoose]

Ditto

I also have a Bruntons 2 bladed Varifold and agree with shaun10463

Fitted a bruntons (2 blade) prop earlier this year - noticed a couple of things.

1) yes better speed through water. 20% ish
2) No point at all though if you don't keep bottom clean (the boats!)
3) better drive under power (as said in ym test)
4) worse performance in reverse (as said in ym test)
5) reverse not a problem - just need a few more revs - no extra prop walk
6) If shaft drive like mine - boat also points better - now that prop doesn't disturb water flow over rudder the foil is much more effective. This was a big surprise and poss one of the best benifits.

wish i had done it before

 

[stav]

I have fitted a bruntons to a Hillyard and excellent, even on the Hillyard it improved the sailing experience. It replaced a hugh fixed 3 bladed prop. It did not seem to have the real bite when punching in to biggish Channel seas but would still fit one. The folks at Bruntons where really help full and provided various drawing until I found a way off fitting it, though I did have to take two bites out of the rudder to allow it full articulaion.

On the Nic 36 fitted a variprop as it was the only one that really fitted the aperture and again really pleased. Especially being able to adjust the pitch which I have played with until I got what I wanted.

When buying any new (secondhand) boat would always now factor in a feathering or folding prop. Although I am thinking of down sizing and down costing and would not be able to justify the cost but would still look at a Kiwi prop.

 

[emandvee44]

Yachting Monthly May 2009.

Cheers,

Michael.

 

[Quandary]

YM prop test

They did not include Volvo, Radice or J prop.
They tested static pull ahead and astern, motoring speed etc and got some odd results, (the popular Kiwiprop was close to last and three blade folders generally were reported as not much better than the equivalent two blade) The best performer was Flexofold: Varifold and Slipstream also did well. Autoprop was in the middle but best feathering. They reported that many of them outperformed a fixed prop. except at stopping. Motoring speed ranged from 7.0 kts to 7.65, so not that big a range (long term durability can be an issue with folders and not all have anodes).
The results sequence for stopping were almost the reverse of thrust ahead and astern.
Both Flexofold and Slipstream two blade folders were reported to produce thrust very close to the three blade for a lot less money (1/2 to 2/3 of the price)
A 3 blade Flexofold cost between £1.5 and £4k while the Kiwi in any size is below £1k so I suppose you get what you pay for.
There was a thread recently critical of Radice (low thrust, I think)
Tests were all on an Oceanis 323 and suppliers were asked to provide the most suitable for test, for a bigger boat and engine I think the difference between two and three blades is bound to be greater.
I have a Volvo 3 blade bronze folder,looks well engineered, very smooth low drag shape, impressive thrust ahead and astern, fantastic fuel economy but the anodes on it need changing every season, it came with the boat so I don't know the price but the extra over a 2 blade (2007)was £514.

 

[Seanick]

Vote for Variprop!

We have a four blade 22" feathering VARIPROP, supplied by Bruntons, but came direct from Germany where it is made to save time. Its driven by a 69HP 5 litre straight 6 Perkins.

Under power she is better in ahead and stops really well, better in fact than before.
They set the pitch, which is less in astern to reduce propwalk.

After a year we added 2" to the ahead pitch to load the engine more and reduce consumption, and in astern added 1" of pitch to get the propwalk back!

http://eng.variprop.de/

Under sail we have gone from the back of the fleet to the front!

Changing the ptich is so easy with a mask on you could do it underwater.

Beautifully made and priced accordingly!

The reason for going for this one is it has the shortest hub, and needs minimal alteration to an apperture.

When sailing gearbox and shaft wear has of course stopped (which is how I justified buying it, plus the cost of fuel going up


I have since supplied a few to my customers and they have been very happy with the strong astern and better sailing speed.

 

[tel1]

ok, well ive got some really good advice here, im seriousley considering a brutons. and its the london boatshow rather soon! what details will i have to take to the show regarding a prop? is it just boat size and engine size?

would anybody have a rough idea on cost as well? id look in mays issue of ym but like a fool i left it on the boat!

many thanks again!