Earth bonding P Bracket

[voiceman1uk]

Hi all just noticed the earth bonding going to the P Bracket on my SO 42i has broken..problem is I can’t see how I can replace as what’s left disappears into the gel coat has anyone had a similar issue I have included a picture

[MalcolmP]

Coincidentally I checked mine recently and it was fortunately still in perfect condition. I have a 39i but the moulding looks identical to yours. That braided copper does seem to be prone to rapid corrosion if it gets salt water on it.

In this thread  jeanneau.proboards.com/thread/6404/bracket-earth-strap  another 42i owner had same issue and decided to bolt on anodes externally direct to the P bracket. I have also done this as I suffered some stray current corrosion last year.

If you prefer to retain the inner bonding, it might be possible to carefully open up a hole next to where the remains of the strap emerge, by some careful shallow drilling and a dremel until you can expose 30mm or so of the braid, then attach a new cable - you might have to crimp that in some way, as doubt soldering would take to the braid. Then refill the hole with epoxy.

Others may have better ideas, hopefully based on actual experience of repairing this.

[ianpowolny]

Malcolm I’m also going to have to replace our earthing cable. This braid doesn’t look to good. Any thoughts on a better wire to use?

Are you coming my way in the near future? We’re bacl to Spain next Saturday.

Ian

[MalcolmP]

Aug 16, 2019 13:01:56 GMT ianpowolny said:

Malcolm I’m also going to have to replace our earthing cable. This braid doesn’t look to good. Any thoughts on a better wire to use?

Are you coming my way in the near future? We’re bacl to Spain next Saturday.

Ian

Hi Ian

I think joining onto the OEM braid is the main issue, possibly could make a clamp with washers onto the braid then bolt onto a crimped ring terminal on new wire. The standard braid ends are fairly agricultural in any case eg www.cablecraft.co.uk/braided-earth-lead-flat-stud-size-m10-8800

best to use a reasonably  large cross section, maybe something like a battery cable. Some of the sparkies here can probably give mm2 recommended.

I will email you about boat movements

cheers Malcolm

[voiceman1uk]

Thanks Malcom/Ian

i will bring my dremel over next time and some very careful excavating around what’s left...glad to here your moulding is the same though


thanks again

Paul

[Trevor]

Hello gents,

I agree to dig down and attach to the end buried into the moulding. The cross sectional area of the cable need not be too great. It is merely to provide a nice low resistance path between the P bracket and the propeller shaft.

To put a little science behind it, the cable is to carry very low current between the P bracket and the anode on the stainless prop shaft. It should be very low resistance but not because it is carrying high current, but rather because it needs to present a very easy path for currents to pass from the protection anode.

A typical bonding cable cross sectional area used when bonding underwater metals to sacrificial anodes is 10mm squared. That is about 7 AWG or about 3.6mm diameter wire. This has a resistance of about 0.5 ohms per 330 metres. Typically the distance of the wire to the engine is about 4 metres or 4/330 x 0.5 = 0.006 ohms......very very low resistance indeed.

I would use about 10mm squared cable if you didn't want to use braid like the original and it will perform the task very well. It is strong enough to handle the mechanical rigours of the job and well and truly has a low enough resistance to perform its intended purpose.

I hope this helps.

Trevor

[MalcolmP]

Aug 20, 2019 6:27:48 GMT Trevor said:

Hello gents,

I agree to dig down and attach to the end buried into the moulding. The cross sectional area of the cable need not be too great. It is merely to provide a nice low resistance path between the P bracket and the propeller shaft.

To put a little science behind it, the cable is to carry very low current between the P bracket and the anode on the stainless prop shaft. It should be very low resistance but not because it is carrying high current, but rather because it needs to present a very easy path for currents to pass from the protection anode.

A typical bonding cable cross sectional area used when bonding underwater metals to sacrificial anodes is 10mm squared. That is about 7 AWG or about 3.6mm diameter wire. This has a resistance of about 0.5 ohms per 330 metres. Typically the distance of the wire to the engine is about 4 metres or 4/330 x 0.5 = 0.006 ohms......very very low resistance indeed.

I would use about 10mm squared cable if you didn't want to use braid like the original and it will perform the task very well. It is strong enough to handle the mechanical rigours of the job and well and truly has a low enough resistance to perform its intended purpose.

I hope this helps.

Trevor

Very helpful as always Trevor.

I wonder why Jeanneau use braid originally for this? Guess it won't break easily if subject to vibration. But it does seem to so easily corrode when subject to salt water...

[Trevor]

Hi Malcolm,

Yes, the flexibility of the braid is probably why they used it as it is glassed into the hull at the P bracket. It can handle vibration and will not snap off at the fibreglass with movement. The unintended consequences is the corrosion problem. It would have been better if they had provided a solid bolt to terminate the bonding cable. The braid does fairly quickly convert to a cable as seen in the photo so it is only used where the connection is made into the hull.

Trevor

[Trevor]

Just as a follow up. Maybe a good solution would be to dremel the fibrglass around the braid in the hull and attach that to a 10mm bolt that is glassed back into the hull. Now attach the cable to the engine with a lug to the bolt. With two nuts, one above and one below the lug, the pressure when tightening can be controlled and the problem will be solved. It would have been a good solution at the time of manufacture. Stainless bolt, nuts and washers would be suitable and provide a really good solution.

Regards,

Trevor

[MalcolmP]

Hi Trevor

Great idea, would be a much better permanent solution.

Malcolm

[Tafika II]

Hey Trevor!
Using SS fasteners in a mechanical solution at the existing P-Bracket and engine sounds like a great solution, but could you us a SS briaded grounding strap also rather than copper or bronze?

[Trevor]

Hi Brent,

Yes I think that sounds like a great idea.

Regards,

Trevor

[voiceman1uk]

Good idea I give it a try and keep you posted back to Denia in 3weeks dremel in hand

[voiceman1uk]

Just a quick update..dremel in hand went down about 10mm around the braid, unfortunately the braid just crumbles. Was not feeling brave enough to go much further, so not sure were to take this now and even it it is a real issue

[MalcolmP]

Sept 23, 2019 7:37:32 GMT voiceman1uk said:

Just a quick update..dremel in hand went down about 10mm around the braid, unfortunately the braid just crumbles. Was not feeling brave enough to go much further, so not sure were to take this now and even it it is a real issue

Frustrating to say the least...
Guess the corrosion must have wicked down the braid.

Maybe consider bolting a zinc direct to the P bracket.

[Trevor]

Yes that is very annoying indeed. As Malcolm mentioned, providing protection by connecting an anode right on the “P” bracket may be the best option.

[mthackray]

My recently purchased 2007 39i has exactly the same problem.  The strap coming out of the top of the propeller bracket housing in the interior has become corroded, brittle and broken off.  During the survey, the surveyor recommended to "re-connect the interior bonding strap and at the next haul-out fix a zinc anode directly to the strut to provide cathodic protection."

I had the same problem others had trying to reconnect the bonding strap.  There is but a small stub left sticking out of the top of the bracket.  I have jury rigged a connection to that but have no confidence in its long term viability nor the quality of the electrical connection.

I plan to add a zinc at the haul-out this fall.  My question to the experts: what size, shape and type of zinc would be recommended?

Mark

[MalcolmP]

Mark

Suggest you look for a disk type anode that has as small a hole as possible to reduce the dia of the fixing hole you need to drill.

You can add one each side, with GRP boats I am advised that you cannot over zinc

[shawnkaplan]

Super useful posts. I too am wrestling with the same issue. Dang. A bolt would sure have been the right design technique. If/when I Dremel into it that’s certainly the way to go.

Did you guys say that there is a conductive epoxy that could be used? Like to just drill in a hole place in a post- and then fill with a conductive material.

[pagoda54]

Sept 30, 2019 8:16:05 GMT MalcolmP said:

Mark

Suggest you look for a disk type anode that has as small a hole as possible to reduce the dia of the fixing hole you need to drill.

You can add one each side, with GRP boats I am advised that you cannot over zinc

As per my much earlier post - you need to look for a "trim tab" anode - two clam-shell halves about 50-75mm diameter with a 5 or  6mm bolt between. We use them with our 42iP which lost the in-board braid to corrosion some time ago.  A 5-6mm hole and anode will do no meaningful harm to a P bracket.
Galvanic corrosion might !

[mthackray]

All,

As stated earlier, I have jury rigged a new internal connection between the engine and the propeller bracket by connecting onto the stub sticking out of the top of the propeller bracket housing but am not confident in its long term viability.

In October the boat was pulled out for new bottom paint.  At that time I had a 50mm clam shell anodes attached to the bracket. See the picture below.

At that time, the folks doing the bottom paint also polished the propeller and propeller bracket.  Of particular interest to this thread may be the condition of the bracket.  As can be seen, the metal is very pitted.  I cannot say how long the interior connection was undone.  (I purchased the boat this summer and the survey found it unconnected.)  I suspect it was for some time.

The question now is will the clam shell anodes, and somewhat suspect internal connection, prevent further degradation of the bracket?  Any comments welcome as I'd prefer not to learn the hard way that these fixes don't work.  Replacing the propeller bracket looks to be extensive and costly.

Regards,
Mark



www.23hq.com/MThackray/photo/62564595/original

[MalcolmP]

Nov 23, 2019 19:46:42 GMT mthackray said:

All,

As stated earlier, I have jury rigged a new internal connection between the engine and the propeller bracket by connecting onto the stub sticking out of the top of the propeller bracket housing but am not confident in its long term viability.

In October the boat was pulled out for new bottom paint.  At that time I had a 50mm clam shell anodes attached to the bracket. See the picture below.

At that time, the folks doing the bottom paint also polished the propeller and propeller bracket.  Of particular interest to this thread may be the condition of the bracket.  As can be seen, the metal is very pitted.  I cannot say how long the interior connection was undone.  (I purchased the boat this summer and the survey found it unconnected.)  I suspect it was for some time.

The question now is will the clam shell anodes, and somewhat suspect internal connection, prevent further degradation of the bracket?  Any comments welcome as I'd prefer not to learn the hard way that these fixes don't work.  Replacing the propeller bracket looks to be extensive and costly.

Regards,
Mark

Mark

I thought that was my photo of our 39i bracket at first....



I had almost the same issue, but I am fairly convinced this was due to stray current in the marina we overwintered in last winter in Valencia.  We have had our 39i from new in 2008 and the earth bonding strap is still in perfect condition and we had never had any pink dezincification  in all those year. Like you have fitted a disk anode, will be hauling out in March (now in different Marina) so will report back then. Full story and very useful comments and explanation by others on this thread:

jeanneau.proboards.com/thread/7459/stray-current-corrosion

[zaphod]

My 39i came with a zinc already bolted to the strut. I have no idea if the bonding strap is intact, but I suspect it is, I will check next time I am down at the boat.

My strut is in perfect condition. On my last boat there was no bonding, and there was no zinc on the strut. The boat was 40 years old and there was no sign of corrosion of any kind on it.

I have only ever had 1 zinc on the prop shaft, and nothing else, and replace that zinc once per year. Never any signs of corrosion on prop, shaft or zinc.

Am I just fortunate because there is very little electrolysis at our docks? (Boats are tested for leakage annually). Or is it because my last boat had minimal electrical systems?

[blackpearl]

Appears to be a common issue with the 39i (mine is a 2009).  I had the same issue and wound up installing a clam shell zinc


www.23hq.com/blackpearl/photo/62607053/original

[pagoda54]

Ouch!  

That is surely more than 1 season's corrosion??

Both our shaft anode and propeller anode were part  eaten away when we lifted out a couple of weeks ago. The P bracket anode was less used up. (But partly used).

We also use a galvanic isolator on our shoreside electricity connection to reduce the chance of stray currents from faulty nearby connections in other boats.  It's difficult to quantify the benefit, but we still have some zinc left at the end of the season. 

Zinc costs a lot less than replacing what it protects!