Bonding/grounding flexible shaft coupler

[KWKloeber]

I recall "recommended" and "mandatory" requirements. What's meant by "voluntary" requirement?

Jon to frame a little tighter what I meant by voluntary standard, I'll use Rod's post from 2009 (referring to bonding the prop shaft) which explains it well -
"ABYC is NOT mandatory but a suggested good standard based on years of combined experience by its many voting members."

When no one (i.e., states, CG, etc.) enforces a standard (i.e., "NOT mandatory"), it's use is "voluntary."  But mea culpa - my using "voluntary" with "requirement" was an oxymoron.  I should have written "ABYC (voluntary) standard" rather than "requirement."

There's no ABYC Police so the use of "must" is pretty meaningless.  One "must" take an action in order to comply with that standard, but the standard itself is voluntary -- so it's circular reasoning.
A "must" code is different from stating a fact (e.g., to bond the AC to DC one "must" jumper between the two busses.)  That's true whether or not the owner decides to do it.

This is in no way meant to imply that any particular ABYC standard is bogus, or that insurance companies don't rely on it -- but pointing out facts that are facts.

-k

[Noah]

b]an alternative means of grounding the shaft must be provided[/b]."

Mainesail, can you please explain the reason for this? Is it an AC, DC (or both) shock protection issue or...? And, as Alex asked, can one use the strut as a ground if shaft is isolated by flexible coupling? Also, how much resistance measured between engine and shaft is permissible.

[Jon W]

What's the composition of the cutlass bearing? Mine looked to be composite material no metal. If no metal, it would isolate the shaft from the strut so wouldn't provide a ground.

[Noah]

Think what Alex was asking is if one were to attach a ground wire to the strut bolts inside the boat, would that give an acceptable path to seawater if the rubber lining in the cutlass bearing and a flexible coupler are isolating the shaft. Would that be a acceptable alternate ground path INSTEAD of the shaft.

[KWKloeber]

What's the composition of the cutlass bearing? Mine looked to be composite material no metal. If no metal, it would isolate the shaft from the strut so wouldn't provide a ground.

Jon,

Regardless of whether the bearing shell is brass or composite, the rubber inside insulates the strut from the shaft.

[KWKloeber]

...the Feds simply adopted (incorporated by reference) ABYC A-16 as part of the CFR requirement.

Mates, I think key is to understand differences between citing technical manufacturing standards and "enforcing" standards or codes that involves an action.  Granted, it's oftentimes challenging to accurately interpret Fed regs -- there's another famous (maybe infamous?) Fed reg example involving displaying documentation numbers.

The Feds DID NOT adopt A-16.
The CFR incorporates A-16 ONLY to this extent: lights must "Be certified by a laboratory listed by the Coast Guard to the standards of ABYC A-16."  In English: "We (the CG) allow a light that a lab (that we approve of) certifies it meets A-16."  Way different.  A-16 also covers installation and the CG reg doesn't say boaters must "install lights per A-16."  CG has its own reg for that.
So no, the CG doesn't enforce A-16 -- Coasties don't carry a copy of and enforce A-16 when they board your boat.  Maybe it's a misunderstood or imperceptible difference, but it's an important difference when it comes to regulations.

In fact, if you look at A-16, 95% of it merely copies COLREGS.  Does that equate to ABYC enforcing COLREGS?  No.
A-16 also cites the Society of Automotive Engineers, so does that equate to ABYC enforcing SAE requirements?  No.

boaters should always try and follow the ABYC guidelines when doing work on their boats. 

No question!! To the extent possible and appropriate.

[Noah]

The reason I split this thread earlier, from the "re-wiring my boat" thread, was to hopefully have some expert(s) weigh-in on what is the science/reasoning behind requiring the prop shaft provide an electrical path from inside the boat (either AC or DC or both), to the sea. Unfortunately, I am still unclear about what the reasoning is.

[Jon W]

Noah, think it was Antoni, but I didn't think of tieing the internal strut bolts to a shaft or flange hub rotating at 800-3,000 rpm. Why not use the silver impregnated rubber strip intended for this purpose available from R&D mentioned in his first post of this thread?

Well Ken I was going to say the cutlass bearing electrically isolates the shaft from the strut, but thought someone would comment it depends on the material composition (like the silver impregnated rubber strip) so tried to head that off by providing a caveat.

[Noah]

Jon—I am not talking about connecting the shaft to anything. Alex asked about tying the strut to electrical system to bypass a need to include shaft. There are lots of devices to tie or jumper flexible couplings (silver impregnated wire for R&D couplers, or external shaft brushes), but I want to know WHY it is needed at all. Notably, Vetus, makers of the Bullflex coupler that I have, doesn't mention the need nor market a jumper, that I could find. Why? Maybe because it is made in Europe and a ABYC recommendations don't apply?? I would like to know the logic/need to connect the shaft. I am a sailor not an electrician, so I am NOT knowledgeable in this subject, thus the call for expert help.

[Jon W]

Mainesail's post says the shaft must be grounded. How do you ground it without connecting to it? I'm looking forward to the reasons behind the requirement as well. Guess it isn't my night. Quick look at my watch and realize it's tequila time. 

[Noah]

Mainesail's post said: "6.5.5.2 If a non-conductive flexible coupling is used, an alternative means of grounding the shaft must be provided."

An "alternative means" could perhaps be provided by the strut. (?)

[lazybone]

I'm going to guess that the reason for the prop shaft ground is that in case for some reason the AC neutral/ground is lost.   The AC neutral would be replaced by the DC ground to sea water.   

Any divers in the water are considered collateral karma.

[Noah]

I am also wondering how much resistance is deemed to be "non-conductive"? Lots of question here...

[LogoFreak]

I ask questions in a weird way sometimes, English isn't my first language but I don't think it's a language thing LOL. What I asked originally is. Since I have a flexible coupler that breaks the electrical continuity to the shaft and the grounds that are connected to the block no longer have a path to seawater can that path be restore by grounding to one of the bolts that hold the prop strut on. No that will not re establish an electrical continuity to the prop shaft as the cutlass bearing has a rubber sleeve, but I don't think the requirement is to be specifically grounded thru the shaft, but more so to have a ground that goes to sea water.

The other question related to that is, does a dc ground connected directly to a bronze fitting that's underwater "invite" extra corrosion? If so then using the prop strut wouldn't be a good idea, in which case I'd opt to install a sintered bronze plate for my grounding.

I've got 2 days before I hit the water, let's come to a consensus quick yeah? Lol

[Admiral_Swellson]

I like this guys inexpensive solution:

https://www.cruisersforum.com/forums/f114/grounding-shaft-with-a-driversaver-56582.html#post648238