Julian,
No problem pointing out the possible negatives about ferrocement, they can be real and there are a lot of problems with many home made boats out there. I had much trepidation myself before I bought this boat and I did a lot of research. In the end, the price point and potential for the boat made it worth the risk. Since buying it almost six years ago I have absolutely NO REGRETS. Having worked on it for several years and cruising it nearly 2000 miles in the last two years I've gained nothing but the utmost respect for both its design and construction. Because the flip side of ferrocement is that if it's done right, it's about the best thing you can build a boat out of. You get the strength and durability of steel with non of the maintenance issues. Also, the thermal mass of the concrete keeps it bone dry inside and I've never had any sweating or mildew issues like I have had with all fiberglass boats I've owned in the past. I don't have any experience owning a steel boat, it was actually what I was looking for when I found the Arc and decided to take a chance on ferrocement. Homemade cement boats have a well earned bad reputation but not all of them are bad apples.
One unique aspect of the Arc, besides an excellent design and outstanding construction from the bottom up, is that it is completely skinned, inside and out, in fiberglass cloth and epoxy. So it also has some of the positive characteristics of a fiberglass boat as well. I've had occation to do some core sampling on a few locations of the Arc as I've made various penetrations and so far the steel mesh has remained pristine. There is actually a special galvanized spring steel mesh made in Belgium that you are suppose to use and many home builders cut cost by using inferior products that resulted in problems later. I take great comfort in the fact that the original builder of the Arc knew what he was doing and did it right. The boat is 32 years old now and going strong.
That's why I'm so paranoid about messing it up by creating some galvanic issue with my extreme solar makeover. I've gone to great effort to keep the system components isolated from the hull but I'm still not totally comfortable with letting the 120V AC system float either. It's something I am constantly investigating and questioning other people about and your reference was excellent. I've saved it to my favor.
Thanks again.
Carter
From: Julian Webb <julian.proto@gmail.com>
To: electricboats@yahoogroups.com
Sent: Thursday, August 22, 2013 11:37 AM
Subject: Re: [Electric Boats] proper grounding for electric yachts
To: electricboats@yahoogroups.com
Sent: Thursday, August 22, 2013 11:37 AM
Subject: Re: [Electric Boats] proper grounding for electric yachts
Hi Carter
- The boat I am refitting is a 1965 steel hull so which is showing all the signs of pitting around the anodes (too many anodes?) brass props chemically bonded to steel shafts, sea cocks eaten away etc etc so I was paranoid about getting it right.
- This was the first and best site I saw that made bloody good sense, and yes i had forgotten about those not on the boat etc etc, sobering stuff for someone who plans on living on canals etc.
- I saw a ferro cement boat years ago that was hit by a steel boat and a huge (.5M x 1M) piece fell away to reveal the rusty traces of the metal reinforcing that had been used to build the sub frame. After a bit of further drilling etc the owner found that there was hardly any steel left, most had turned to rust "tracks" through the cement.
- The theory at the time was acidic cement and all sorts of other "back porch expertise" but at the time I wondered if it might not be a galvanic action thing?
- Cement is porous after all and it would make a weak but very real battery with it's salt water electrolyte and steel (reo bars) and zinc (galvanised steel ties/mesh) or any two different metals inside the cement?
- Not meaning to be negative at all just food for thought.
Julian
On 21 August 2013 02:13, Carter Quillen <twowheelinguy@yahoo.com> wrote:
Julian,Thank you for the excellent reference. I've researched this subject ad nausium and so far, this is the best explanation I have seen on the subject. Although even after reading it several times, I have to admit I'm still a little confused on some of the finer points of galvanic corrosion hazards. I even went to the section on it and read that twice. One thing is for sure, there are a lot of people with a lot of different "opinions" on the subject and this article really set a few things straight.The issue of possibly shocking people "not on the boat" with an improperly bonded shore connection is certainly the most important take away here. It is something I hadn't considered and I'm relieved that I don't have the capacity for a shore connection any more to create this hazard. Originally the Arc was equipped with an isolation transformer on the shore power connection and although I knew "why" it was there, I never really understood exactly "how" it provided galvanic protection. Since the boat's AC side was not bonded to the hull, I'm not clear if it actually provided proper protection anyway. Although the guy that built that boat really seemed to know what he was doing so maybe it did.As for the shock hazard for "people on the boat" from an improperly bonded internal AC system on a fiberglass or wood boat, I would point out that the possibility of actually creating a shock hazard, although possible, would be quite remote. However since the galvanic corrosion hazards to a fiberglass or wood boat are almost non existent, there is no good reason not to bond them and you might as well do it. As for a steel or Aluminum boat, this is an entirely different matter and I can certainly see the importance of proper bonding in their case, even if it might create a possible galvanic corrosion issue, because the likelihood of a potential shock hazard from an interanal AC system would seem much greater on a metal boat.However, for a ferrocement boat like the Arc where the shock hazard is pretty nil like a fiberglass or wood boat but the potential galvanic hazards are very high like a metal boat, I'm going to continue to take my chances and hold off doing any bonding to the hull until I fully understand all the potential implications. I have gone to great efforts to electrically isolate all the solar panels and power electronics from any connection to the hull. I even installed gfi breakers on my panel box from the inverter that feeds the AC outlets on the boat. The last thing I want to do now is provide a direct electrical path to the ferro in the cement. I believe my ultimate solution may be to install a dynoplate that is isolated from the hull for my earth ground and simply keep the hull out of the equation completely.It may be an unfounded paranoia on my part but I'm personally am just not comfortable grounding my 120V AC system to the ferrocement hull.CarterFrom: Julian Webb <julian.proto@gmail.com>
To: electricboats@yahoogroups.com
Sent: Tuesday, August 20, 2013 4:21 PM
Subject: Re: [Electric Boats] proper grounding for electric yachts
- it matters a lot!!!- there is more myth and bullshit around on this than almost anything else i've come across.- if you can read the attached article and find one "hole" in it, i'd love to hear it, otherwise earth, earth, earth, the correct way of course.- there is no knowledge based argument against doing it correctly, and several reasons why it should/must be done.
On 23 July 2013 22:14, Carter Quillen <twowheelinguy@yahoo.com> wrote:Thanks Tom, that's good to know, I've been told I was not in compliance by letting it float and that it was technically suppose to be grounded, although many do not.What about the 120V house power system? I've left that ungrounded as well and I'm pretty sure that is not in compliance but it would be nice to know if it was. I know every set of directions I've ever seen shows it should be grounded. I've spoken with the inverter supplier and he said it was technically wrong but would not hurt the inverter and that many people do it that way. Seems it is a disputed subject.The risk of a shock hazard is there I know, but it is minimal. First I'd have to have a significant ground fault in my system, then I'd have to be grounded good enough myself to pass current if I came in contact with a component that was hot. While possible, it seems unlikely since the boat itself is not really grounded so you would have to be in sumultaneous contact with your neutral which is possible but unlikely.You know you can stand on a rubber mat and stick your finger in a light socket and not get shocked. I've seen it done more than once. Actually tried it myself once. While you rise to a 120V potential, if you are isolated from ground, there is no current flow and thus no shock. Kind of spooky and I don't recommend doing it but it does work. No ground, no shock!One professional installer of solar systems I talked to said that oil rig operators absolutely forbid grounding of a system on thier rigs and insist on letting it float for the same reason I have. Fear of a ground fault causing excellerated galvanic corrosion.CarterFrom: Tom <boat_works@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Tuesday, July 23, 2013 12:59 AM
Subject: Re: [Electric Boats] proper grounding for electric yachts> http://www.archemedesproject.blogspot.com/
No worries, Carter. ABYC allows your configuration. And as far as I can tell, the USCG hasn't addressed electric propulsion for recreational boats.
Re ABYC Standards:
For DC systems 50V or less:
E-11.5.4.74 allows, but does not require, the DC negative side to be connected to the DC grounding bus.
E-11.16.1 allows, but does not require, a DC grounding bus.
For electric propulsion systems >50VDC but <1000V:
TE-30 requires the propulsion electrical system to remain isolated from the boat's grounding system. Non-current-carrying conductive parts (e.g. motor case) should be tied into the boat's grounding system.
My copy of the standards is a few years old now, these documents may have been revised by now.
-Tom
--- In electricboats@yahoogroups.com, Carter Quillen <twowheelinguy@...> wrote:
>
> That's the way I set up my boat as well and a lot of people do it that way but I believe it is in direct contradiction to the ABYC standards. However I don't think it matters unless you're trying to get your vessel certified by the Coast Guard for commercial endeavors. If you have a steel, or in my case, ferrocement boat, grounding your system to the boat can cause a disaster if a ground fault develops in your system.
>
> If your vessel is for private use, not being in compliance with the ABYC guidelines is usually not a problem, (unless you're doing something realy stupid), except maybe to qualify for insurance. But when you're talking about old refurbished boats, it's almost impossible to get affordable insurance anyway and most people simply self insure anyway.
>
> Carter
>
>
> ________________________________
> From: Fred Liesegang <fred4936@...>
> To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
> Sent: Monday, July 22, 2013 5:45 PM
> Subject: Re: [Electric Boats] proper grounding for electric yachts
>
>
>
>
>
>
> Hello, I converted both a truck and my boat to electric. They both have floating grounds. It is best to keep the two systems completely isolated.
>
> Fred Liesegang
> Tartan 27-2 Eagle
>
>
>
> ________________________________
> From: semicolonsutra <no_reply@yahoogroups.com>
> To: electricboats@yahoogroups.com
> Sent: Saturday, July 20, 2013 1:54 AM
> Subject: [Electric Boats] proper grounding for electric yachts
>
>
> Can anyone give me pointers on how to properly ground my DC electric system on my electric powered boat? Previously the negative ground wire went to a Perkins engine and now I have a ME0913 from Thunderstruck and not really sure or competent as of yet as to how to properly ground it or if this indeed is possible. Any tips or references, or pictures would be appreciated.
>
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