Prop Choice for Liveaboard

[Jonny_H]

One of the items on the list before we cast off next summer is a new prop. The survey last year showed our current fixed 3 blader to be a little brittle on the edges.

I've been looking at various models:

Kiwi - Looks good, and not too expensive
Autostream - Again, looks good, but twice as much as the Kiwi
Maxprop - Awaiting quote
Autoprop - Way out of budget!

We currently get quite a lot of prop kick so thought a feathering prop may help this? She's not what you'd call overpowered, (36hp with 9 ton displacement) but stops of with the fixed - we therefore thought a folding would leave it underpowered in reverse.

However, even the Kiwi is a lot of money compared to a replacement 3 blade fixed.

What do other liveaboards think - is a feathering prop a good idea, will the extra 0.75 knot be worth it? Is the maintenance an issue if we're only planning on hauling out every 18 months or so?

Lots of other kit to buy (and limited funds) - so would you put a Kiwi (or other) prop on the xmas list, or save £500 to spend elsewhere and get another fixed prop?

Alternatively - can brittle props be repaired? (Only brittle on the edges)

Thanks in advance!!

Jonny

 

[Bajansailor]

If you REALLY do have to replace the propeller, I would be inclined to just get another 3 fixed blade prop - not much on it to go wrong, and you 'save' a fair wodge by doing so (which can then be spent on other kit....).

But how 'brittle' are the prop blade tips?
Perhaps when you next haul out, try walloping them with a wooden or hard rubber mallet and seeing what happens.
If bits fly off, umm yes, they must be a bit brittle.
If nothing happens, especially when you give the prop a few more wallops, then the odds are that it should last a while longer quite happily.

Edit :
PS - It could be worthwhile in the meantime acquiring a 'spare' fixed prop if you decide to stay with this type - and then if the 'brittle' one is still OK, then you have a spare (always useful, if you have somewhere to stow it). And if the brittle one falls apart, you have a new one already to hand.

 

[Salty John]

I went from a two blade fixed to a three blade fixed to improve my ability to make progress to windward against the trades. The loss of speed under sail in light airs wasn't a serious issue. Also, predictable prop walk in forward and reverse makes handling under power easier.
I'd stick to the fixed three blade, but you're cruising plans may require you to maximize light airs sailing performance whereas mine didn't.

 

[Jonny_H]

Cruising plans for the next few years are:

Atlantic Crossing, Caribbean, Panama Canal, Pacific, onto Australia

Then we have a couple of years in Oz.

Lots of downwind sailing (hopefully) - should be in the trade winds most of the way (done lots of planning on timings re weather routing etc).

Ours isn't the quickest boat in light airs - hence the suggestion by someone to go for a feathering prop. On the other hand .... when cruising whats the rush? Its only 0.7 of a knot max.

Thanks for the advice - keep it coming before the time comes to get the chequebook out and do something with the prop.

Jonny

 

[FullCircle]

0.7kt is a 100 miles a week. Call it 85 miles at 0.5 kt difference. Thats about a 10% difference, so 1 day gained every 10 days at sea. Consider that for the Pacific leg, would make a lot of difference.
Just a view.
PS I have a Kiwi, makes the difference on my 7 tonne 35 foot at the lower wind speeds. My boat would not work in less than 8 knots, now works the same in 4 knots. Big difference at that end of the scale. Not as noticeable in heavier breezes.

 

[Bajansailor]

Most of your sailing for the next few years is going to be in the tradewinds - so mostly down wind, although you will be sailing hard on the wind occasionally on passages between the islands in the Caribbean (and the Pacific as well I am sure).

And the trade winds typically blow between F 3-5, and sometimes a bit more if they are really in their stride.
If you do have very light winds, sailing downwind, eg in mid atlantic, I think that you will get more positive effect from using a spinnaker or cruising chute (when compared to say poled genny and main wing and wing).
This should easily overcome the 0.7 knot difference (is it really that much) between a fixed and folding prop.

It is also worth bearing in mind that a layer of slime on the bottom of your boat can knock up to 10% of your speed off, when compared to a nice smooth bottom.
So when you are in the tropics especially, it is well worthwhile diving over the side and giving the bottom a wipe down with a sponge to get the slime off.
And it is good aerobic exercise as well!

 

[jonic]

Hi jonny. For me it would be new 3 blade fixed, no question. The money saved will buy you things that will be of far more use. Or it can go in the repairs en-route jar. Tip- get a largeish jar.

You will also learn to use (and love) your prop Kick and appreciate the grunt and instant reverse of the fixed when it's 3am and you are coming into yet another unfamiliar place with the wind and currents against you. Especially if your hyrdrovane rudder is in the water making reverse even more "interesting".

 

[FAITIRA]

Stick with 3 blade fixed KIS.

 

[Jonny_H]

Thanks!

This is what I was thinking. The Kiwi is around £500 more than a fixed prop - that will pay for plenty of stuff thats still on the list!

We have got used (quite quickly!) to the prop kick - coming into marinas etc this summer made a real difference provided we could pick preferable berths! The only trouble with the prop kick is that its quite strong and it is difficult to make her go astern in a straight line - I'm not looking forward to med moorings (if we get any) - may end up bow to instead!!

Hope your well - love your latest newsletter!

Jonny

 

[HoratioHB]

Have to disagree - we have a Kiwi and its great. Shortly after we got the boat we hit something and broke a blade. Put the fixed three blader on and lost 3/4 of a knot and 5 degrees on the wind, no stern power and lots of prop walk. Obviously I was concerned about why the blade broke but the subsequent analysis suggested that had it been a conventional prop the whole thing would have been written off and probably bent the shaft to boot.
BUT most importantly it was fixed by me for £50 with a new blade, which is simply held in with a metal pin, which taps in or out. I now have another spare blade and know that wherever I am I can change it (diver see). Getting off a metal prop is a boat lift and puller job, repairing a Kiwi is a 2 minute boat in water job - gotta be good when in the boondocks - and you get the performance as well.

 

[FAITIRA]

Agree jonic, but I find, (mind I can reach it on this boat), that the hydrovane rudder is a great help, astern and ahead in tight spots.

 

[damo]

Prop kick is great if you can anticipate and use it properly /forums/images/graemlins/smile.gif

My pulpit has a step-through cutaway, so it is easy getting on and off the bow, but from what I can see of your avatar yours doesn't?

One of the highlights of last summer for me - using the wind and prop kick to back into a berth without touching the neighbouring boat or the finger pontoon /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif

 

[Jonny_H]

We don't have a pulpit cutaway - however we don't have a sugar scoop at the stern either - so neither bow or stern to would be 'easy' to negotiate (both would require a board plank).

We've coped well with the prop kick so far - the only time we've made a pigs ear of berthing was when we tried to coax the back end to go against the prop kick when leaving the marina - didn't work - but when we let the stern go with the prop kick we got out no problem!

Sounds like a fixed 3 blader is the way forwards - no rush when cruising, less to go wrong, sailing (hopefully) in tradewinds, and more ££ left for other items - how much would people suggest a 3 blader should be then? I have the invoice from the original prop (1996 price £189 - 17x11x3 Aquapoise) - any suggestions on a good place to get the next one from (Hamble Propellers did the last one)?

Thanks all

Jonny

 

[Jonny_H]

Has anyone had any experience with 'Perfect Pitch' props from the US?

They are fixed props but have Urethane blades which 'flex' between 1-2 inches in pitch in reverse as the material is semi-flexible.

Sounds like a good idea - any experience / opinions??

http://www.sailcdi.com/ppmain.htm

Jonny

 

[Salty John]

I've always used Michigan Wheel in the USA because they give excellent tech support, including prop selection:
http://www.michiganwheel.com/index.htm

They may have a UK agent. If you complete their prop selection form they'll do the selection which you could compare to your present prop to confirm suitability.

Sorry I can't help with UK suppliers, never having bought a prop here.

 

[bryantee]

sillette -sonic usually have a good stock.

 

[jonic]

[ QUOTE ]
- I'm not looking forward to med moorings (if we get any) - may end up bow to instead!!

Hope your well - love your latest newsletter!

Jonny

[/ QUOTE ]

We have med moored a gazillion times this season and are bows to each time.

1. It's easier

2. We prefer the privacy of having our sleeping cabin and cockpit away from the dock

3. All the nickable stuff like outboards/ liferafts/solar/wind genny etc is then off the dock as it were.

 

[Tranona]

I would be more concerned about why your existing prop is "brittle". The "ringing" test with a hammer will indicate if it is dezincifying and suggest if it is , you sort out your anodes. A new prop will likely go the same way. If the ragged edges are because you have been hitting debris over the years and the prop is sound otherwise, it can be repaired.

New prop likely to be up to £300 in UK, but prices fluctuate because of price of bronze. Plenty of suppliers still in UK. Pukka (bronze) feathering prop of this size would be over 5 times this, although Darglow have a new one just out that is about £1k.

Best budget buy would be repair if possible, keep as spare and buy new fixed.

Hope this helps

 

[Jonny_H]

Current prop doesn't have ragged edges - infact looks quite good:

However the surveyors report last year said: "There is a three bladed, bronze propeller and it was found to have become brittle through the action of electrolytic corrosion. The propeller is still in a serviceable condition" The electrolytic corrosion was due to a bad anode - which has been replaced.

The prop (above) is 17 inch x 11 pitch, I've been recommended a 16 x 10 - what effect will this have on the prop's performance?

Thanks

Jonny

 

[TigaWave]

For cruising fixed, and an old refurbed two blade as spare. I'd also get it drilled and tapped to take a prop jack so it can be easily removed with the tools I carry onboard.

When cruising I'm usually taking it easy on the boat and fittings so very rarely pushing for speed, besides I have a towed generator behind most of the time which adds a bit of drag.