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Darglow Propellor

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robin View Drop Down
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Post Options Post Options   Quote robin Quote  Post ReplyReply Direct Link To This Post Topic: Darglow Propellor
    Posted: 02 Sep 2009 at 2:33pm
I have had my Darglow 3 bladed feathering prop for 5 years and until recently had few problems with it.  However, this summer we would be happily motoring along at 6 kts when the shaft would start to vibrate and our speed would reduce to 2-3 kts. 
 
If we then put the prop astern for 30 secs - then ahead again - all went back to normal. It was pretty random but happened nearly all the time in the Solent - sometimes as often as every 2-3 minutes!
 
Indeed during Cowes week we nealry couldn't get back form Lymington to Cowes because of the problem.
 
The pop was fully serviced over the winter and I have dived and checked and there is nothing around it?  I checked with Darglow and they wee at a loss to explain it.
 
Having watched from the bow while motoring I notice that there are many 'balls' of sea weed in the water about 3 ft beneath ther surface in many areas of the Solent.  I can only assume that these are getting wrapped around the prop and preventing it from deployng properly ...
 
Has anyone else had similar experiences?
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Post Options Post Options   Quote George Isted Quote  Post ReplyReply Direct Link To This Post Posted: 02 Sep 2009 at 4:25pm

Hi Robin,

It has been reported in the media and I have noticed myself that this has been a particularly bad year for sea weed (or rather a good year for growth) and I have often had to remove boot-lace type weed from round the prop.  That said it has not slowed the prop/boat significantly.

 

On the other hand, I can confirm that fishing net on the prop, in-between the channel shipping lanes, in no-wind and thick fog - That does cause a problem....   

 
George Isted
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Post Options Post Options   Quote robin Quote  Post ReplyReply Direct Link To This Post Posted: 02 Sep 2009 at 6:07pm

Do you have 'FEATHERING' prop?  ... because the hydrodynamic flow aver the blades forces them in to the appropriate driving posiiton.  A small amount of weed could distrupt the flow.  This won't affect a solid prop ...

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Post Options Post Options   Quote George Isted Quote  Post ReplyReply Direct Link To This Post Posted: 06 Sep 2009 at 12:19am
yes Robin, Darglow.  Prob around 7-8 years old now.
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Colin Pritchard View Drop Down
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Post Options Post Options   Quote Colin Pritchard Quote  Post ReplyReply Direct Link To This Post Posted: 24 Sep 2009 at 6:56pm
On a slightly different point, could you let me know what diameter and pitch your Darglow props are and what engines you've got? I've had a Darglow feathering prop for 3 years now and find my speed under engine a little disappointing. Darglow are looking into the problem so I hope they can come up with some suggestions.

Regards

Colin Pritchard
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Post Options Post Options   Quote George Isted Quote  Post ReplyReply Direct Link To This Post Posted: 25 Sep 2009 at 10:49am
Originally posted by Colin Pritchard

On a slightly different point, could you let me know what diameter and pitch your Darglow props are and what engines you've got? I've had a Darglow feathering prop for 3 years now and find my speed under engine a little disappointing. Darglow are looking into the problem so I hope they can come up with some suggestions.

Hi Colin,

If your Darglow is one of the older generation (like my own) the stops that control the pitch become worn/damaged over time.  I have this problem and Darglow have offered to reset these for me, I think it is going to cost £100-150 and I plan to send it off this winter.  In flat water I can just achieve 5.5kts but only at well over 3000 rpm at which point it sounds like the pistons are trying to escape through the deck.  

 

This is the reason why Darglow say to only engage forward or reverse gear at idle/tickover speeds as doing so when the engine is at a higher rpm makes the change in blade angle more violent and damages the stops.  Unfortunately, as you know, occasionally you need to go from full ahead to full astern quickly to avoid other boats, flotsam, etc.

 

Ideally you need to record your speed through the water at various RPM’s from 1000 - 3500 at 200-300 intervals and then send this data off to Darglow with your engine info.  They will then deduce what adjustment is required.  

 

Having had a chat with them at SIBS they showed me the new design they now supply for the Contessa, these have the stops that are adjustable/replaceable without removing the prop.

 

Hope this helps.

George Isted
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Post Options Post Options   Quote Colin Pritchard Quote  Post ReplyReply Direct Link To This Post Posted: 25 Sep 2009 at 9:05pm
Hi George

Thank you for that useful information. My prop dates from January 2007 and doesn't have any adjustments available, other than sending it back. As you know, removing the prop is a fairly diffficult job as it involves either removing the rudder, removing the aquadrive and/or moving the engine forward. Also, presumably if Darglow make the adjusments, then further wear is going to occur over the next couple of years so more adjustment will be needed.

Another problem I've had is the anode falling off. At the end of each season so far, when the boat is hauled out, the anode has disappeared. Darglow say this is due to corrosion of the anode, which it may be, but there is no sign of any corrosion anywhere else. It could also be due to grease remaining in the anode fixing screw holes after the greasing operation, which is impossible to clean out and makes it impossible for loctite to fix the screws in place. If so, this is poor design in my view. It all makes me a little disillusioned with the feathering prop and in many ways I wish I'd stuck with my fixed 2 blader, which made the boat go at a decent speed and didn't involve all this messing about....and expense.

Regards

Colin Pritchard
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Post Options Post Options   Quote moongirl Quote  Post ReplyReply Direct Link To This Post Posted: 27 Sep 2009 at 12:49pm
Has your speed always been low with the Darglow or have you noticed a gradual drop? On Polar Star we had a gradual drop until the speed became very poor - this was found to be wear which reduced the pitch. Pitch is the critical bit for any prop. Darglow took Polar Star's prop apart built up the gearing and re-machined it and  the speed was restored.
COLIN
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Post Options Post Options   Quote Colin Pritchard Quote  Post ReplyReply Direct Link To This Post Posted: 27 Sep 2009 at 8:53pm
Hi Colin

The boat speed wasn't quite as good as I'd hoped when the prop was new and it does seem to have gradually reduced over time. At this stage of the season the speed reduction could be affected by hull fouling as well. It's difficult to tell. I'm slightly worried that if internal wear is a problem and the prop needs re-engineering, is the wear going to recur and in 2 or 3 years time further adjustments will be needed.

Regards

Colin Pritchard
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Post Options Post Options   Quote George Isted Quote  Post ReplyReply Direct Link To This Post Posted: 28 Sep 2009 at 1:26pm
Originally posted by Colin Pritchard


Another problem I've had is the anode falling off. At the end of each season so far, when the boat is hauled out, the anode has disappeared. Darglow say this is due to corrosion of the anode, which it may be, but there is no sign of any corrosion anywhere else.
I have never lost an Anode and have not found it necessary to use locktite or similar.   I just make sure the bolts are good and tight before launch.  On lifting the anode is normally about 30-40% waster so I just stick a new one on.  How long do you leave it in the water (or how much use does the boat get) inbetween anode checks?
 
It does sound odd that your prop pitch has gone off so quickly, perhaps this should be a warranty repair...
 
George Isted
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