Bonding System - Do I Need It ?

[Wotname]

Originally Posted by bony

Thanks fellas, it would appear that the nays have it. I wasn't sure if it was necessary or not and now realise I was stressing about it needlessly.

I will bond the r/w intake ball valve though because when I bought the boat the original valve was almost completely eaten away.

Many thanks to you all for the help on this matter, much appreciated.

".....Spend your money on useful toys"

Now that's the kind of advice I really like.

Cheers,
bony

Bony, I apologise if somehow I have derailed your thread, it has headed off down a timber hull track and I know you have a fibreglass hull

I would suggest that you don't bond your r/w valve; just replace it. It was probably eaten away because it was an unsuitable metal (say brass or poor quality bronze) or just old. Replace it with the best quality bronze valve you can source locally and keep an eye on it (along with your zincs).

[Mark Johnson]

It depends. One boat's requirements are different from another, even of the same make!
Experiment...


Some underwater metal does fine unprotected and un bonded, others not. If underwater bronze is turning pink right under the surface, then it is loosing zinc from the alloy, and needs protection. If not, and after scratching or sanding away the surface at haulout it still looks brassy underneath, NOT pink, then it's doing fine!

The shaft and or prop zincs will NOT protect the strut, as it is not in electrical contact with them due to the rubber bearing. This is where an interior shaft brush and bonding wire to the struts interior end, are definitely called for. This way, the shaft zinc protects the strut as well.

M.

[svBeBe]

To: OP

Yes, definitely you want a bonding system.

Bill

[bony]

Originally Posted by Wotname

Bony, I apologise if somehow I have derailed your thread, it has headed off down a timber hull track and I know you have a fibreglass hull

I would suggest that you don't bond your r/w valve; just replace it. It was probably eaten away because it was an unsuitable metal (say brass or poor quality bronze) or just old. Replace it with the best quality bronze valve you can source locally and keep an eye on it (along with your zincs).

No need for apologies Wotname, it has been interesting reading the comments. I read somewhere that it was advisable to bond a fibreglass boat which is why I have been looking for more info on the subject. The only timber on my boat is the marine ply that I used to build a new cabin and a new rudder. My hull was made in the 1970's it is made of laid fibreglass which varies from 3/8" to 1/2 thick. It is very solid compared to modern f/glass boats

My raw water intake was made of bronze as well as the ball valve/sea cock which was screwed to it. The thru hull intake fitting was fine, only the ball valve was eaten away. Probably because it was an inferior bronze.

When I tried to replace the ball valve I could not find one with the same thread. I think it must have been a yanmar intake and is obsolete now. I hunted everywhere but in the end settled for a complete new stainless steel through hull intake and ball valve, which is now installed on the boat.

Mark said ...."The shaft and or prop zincs will NOT protect the strut, as it is not in electrical contact with them due to the rubber bearing. This is where an interior shaft brush and bonding wire to the struts interior end, are definitely called for. This way, the shaft zinc protects the strut as well."

My prop setup does not have a strut. The cutlass bearing fits into a bronze housing which is moulded into the rear of the keel. On the inside of the boat the propshaft passes through a 1 3/4" f/glass stern tube and the end of the tube fits into the stuffing box bellows. You can see the propshaft housing and the new raw water intake in the accompanying photo.

I could use some advice on how to bond the propshaft to the prop housing so that everything is protected.

Thanks for the interesting replies,
bony.

[RUSTYNAIL]

If one of your through hull fittings was completely corroded, I would watch out for 12 volt positive electrical high resistance shorts. Bonding or not bonding has pros and cons, and I could probably honestly be an expert authority for either side in a court case. You have to protect you boat from corrosion and lightning. The ABYC book goes for safety of lightning, and requires bonding. I surveyed a boat once that lost it's propeller blades in less than a week after installing a new battery charger while in the yard. I found that a poisitive terminal touched the inside of the charger's anodized aluminum case. The anodizing was a high resistance connection, so the fuse or circuit breaker didn't blow. The weak positive current just made it through the whole boat, causing fast acting electrolysis instead of slow acting galvanic corrosion.. Even lightning protection has lots of people with different opinions. Good luck.