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Darglow propeller

Printed From: CONTESSA 32 ASSOCIATION
Category: Technical Help
Forum Name: Engine, Gearbox, Stern Gear, etc
Forum Discription: Problems or questions about your Engine, Gearbox, etc
URL: http://www.co32bb.org/forum_posts.asp?TID=345
Printed Date: 17 Oct 2018 at 9:14pm


Topic: Darglow propeller
Posted By: Jerry
Subject: Darglow propeller
Date Posted: 13 Feb 2013 at 7:52pm
My Darglow prop was fitted, new,Angry a year ago + a new anode. My boat lives in Portishead Marina. I took it out of water this week to find the anode had completely disappeared. The two retaining screws remained. Could that be 100% erosion or did it break off ?



Replies:
Posted By: George Isted
Date Posted: 14 Feb 2013 at 12:05pm

If the machine screws are still in place that means the anode has been doing its job.   I normally get two years out of Darglow anode but it depends on where you berth, boats in marinas (especially if plugged into shore power and all skin fittings connected to a common earth) will eat an anode more quickly.

 

Do you have a separate anode that the prop/engine are electrically bonded to, that will help.



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George Isted
Contessa 32 "Concerto"
Co32 Class Captain and Measurer.


Posted By: moongirl
Date Posted: 14 Feb 2013 at 7:27pm
On Polar Star I found that there was either very little left of the anode or it had gone completely at the end of the Season. Polar Star was on a HISC mooring & thus not subjected to the electrical problems generated by shore power.

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COLIN


Posted By: Silver Harmony
Date Posted: 26 Feb 2013 at 9:01pm
The first year I had Silver Harmony, the anode fell off the Darglow propeller, taking a chunk out of the rudder on it's way past. I spoke to Darglow about it and they said that the screws can provide the lowest resistance electrical path from anode to propeller and therefore the anode disappears preferentially around the screws until it falls off, leaving the screws behind. The solution is to make sure the back of the propeller boss under the anode is really clean, to give good electrical contact, and to paint the back portion of the screws before installing them to insulate them electrically. This has worked fine for me for the last couple of years.

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Robert Fox
Contessa 32 "Silver Harmony"


Posted By: rocketman
Date Posted: 01 Mar 2013 at 12:01am
I have had a Darglow prop for over 10 years and spent a fortune on prop anodes. I have always been concerned about the conductivity through the R&D coupling on my Yanmar engine. The electrical path through the R&D relies on a small piece of 'metal loaded' foam rubber.  This time last year I fitted a Mcduff spring loaded carbon brush assembly onto the prop shaft and the prop anode is showing no sign of depletion after a season, however the main anode may have suffered a little.

Stuart. 


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Stuart


Posted By: GlennG
Date Posted: 10 Mar 2013 at 4:38pm
Are they worth it when compared with a £250 three bladed normal prop?

I appreciate there's a tiny bit more drag,  but lets face it,  when there's little wind you use the engine!


Posted By: Alastair Pugh
Date Posted: 10 Mar 2013 at 5:08pm
Ooh, wash your mouth out!  "A tiny bit more drag" is an anathema to any hard-racing-antifoul sailor who trimmed his 3" wide two-bladed prop down to 75mm. Smile


Posted By: Keny
Date Posted: 12 Mar 2013 at 9:54am
One day when I had nothing to do I worked out what effect a standard 3 bladed fixed propeller would have on my boat speed. It worked out at approx. 0.8% at 5 knots. i.e. 1.5 minutes in a 3 hour race, or with my prop.  45 seconds. That could lose you a lot of places!!!
keny


Posted By: George Isted
Date Posted: 13 Mar 2013 at 11:23am
Ha!   I'm with Alastair and Keny.   No point in having a clean bottom and good sails if you are dragging around a three-blade sea anchor.  
 
Then-again, if I was just cruising I may not care as much.
 
Reminds me - I need to check if I have a spare anode in the garage.


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George Isted
Contessa 32 "Concerto"
Co32 Class Captain and Measurer.



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