Tuesday I told you I'd explain the reasoning behind the fuse holder having a melt down and the fuse not being affected at all. The fuse shown in that photo (see below) had been subjected to a DC load (in amperes) at or near its nominal trip rating for an extended period of time. A real world example of this would be the DC supply fuse for something like an inverter installation with continuously running AC appliances. The fuse in that situation may get hot enough to cause a melt down of the fuse holder and maybe even some of the wire insulation near the termination points at the fuse holder. Wayne Kelsoe and I were curious about how long this might take so one of the experiments we conducted in his lab was to hook up a variable load machine to a typical ANL fuse assembly and track the temperature rise over time. In our test we were never able to actually melt the fuse holder (high quality material selection on the part of the manufacturer) but we do know for sure that not all fuse holders are cut from the same cloth, as evidenced by the photo in yesterday's post and many others in our collection.
The question becomes how do you avoid this type of situation? The best solution is not to load fuses continuously at anywhere near their nominal trip point. Additionally, make sure the wire gauge you select is if anything oversized in high current draw situations. Larger wire will do a better job of conducting the heat away from the termination points at the fuse holder. In the video below, Wayne Kelsoe, chief technology officer for Blue Sea Systems in Bellingham, Washington provides a short explanation of what we are doing and what we expect to happen:
For several years now I and some of my colleagues have been raising questions about how we have traditionally prescribed applications for fuses and circuit breakers used on boats. The reasoning behind our questions is based on observations we’ve made in real field applications on real boats. To give you a visual to help you follow along here, the photograph below illustrates what can happen to a fuse holder on a boat under certain conditions. Now the uninitiated might ask: How come the fuse didn’t blow? It’s a great question and one that I’ll answer over the next several installments to Ed’s Boat Tips.
That is not the only question however. The next question is whether or not a fuse or circuit breaker will function in the event of a serious short circuit at or near your boat's battery bank.
First, you need to understand one of the basic, but extremely obscure ratings that all fuses and circuit breakers have, known as the AIC or ampere interrupting capacity rating.
Many folks wrongly think that if they install a 10 amp fuse in an electrical circuit the fuse will blow at a circuit load of anything greater than 10 amps. Well, that’s not actually the case. Most fuses and circuit breakers will actually trip out at somewhere between 125-200% of their nominal rating depending on their specific design. The AIC rating really has nothing to do with this fact.
AIC in simple terms describes how much amperage a fuse or circuit breaker can be exposed to without either turning into a solid ball of metal in the case of fuses, or welding the internal contacts together in the case of circuit breakers. This is obviously important because in the event of an electrical short circuit, we want to open the circuit and shut off the power flow ASAP!
For decades, the ABYC electrical standard has recommended AIC ratings for fuses and circuit breakers in DC applications based on a battery or battery bank’s CCA or cold cranking amp rating; the larger the CCA rating the higher the AIC rating, up to a maximum of 5000 amps.But, some of us in the industry have begun to really question this thinking because we are seeing increasingly larger battery banks in use, particularly on cruising boats both power and sail. Further, we are seeing more and more new battery technology being employed; AGM and lithium technologies are beginning to become mainstream in more sophisticated applications. We need to start thinking in terms of short circuit potential vs. CCA rating. This problem and the question gets further complicated by the fact that the battery vendors often don’t even provide a CCA rating on any labeling on their batteries and you sure can’t tell much by simply looking at the battery. Suffice to say that my colleagues and I know for sure that the short circuit amperage potential at a modern battery far exceeds the CCA rating in any event. The question becomes by how much? Well, it will certainly depend on the specific battery and its age and general condition for sure, but the value will in virtually every case be significantly higher than the battery’s CCA rating.
So during this week I’ll share with you some of the findings in a recent series of experiments myself and Wayne Kelsoe at Blue Sea Systems in Bellingham, Washington conducted in his lab. By the way, if you want to find out the CCA rating of fuses and circuit breakers you might be using, the Blue Sea web site is a great resource as they are all listed. Check it out at: www.bluesea.com
In my last post I promised some video of things burning up. I have the video, but need to spend some time on the exact nature of what's going on. Since I'm still on vacation, I'm going to hold off until next week for those.
Not a problem though. In the first leg of my vacation, I've been sailing around the San Juan islands here in Washington State and have managed to gather up several interesting photos of sights seen. Today's installment is of a rather unusual trimaran that we ran into at Friday Harbor. I've never seen one quite like it, and am wondering if any of my readers can identify this beauty.
As you can see, with this gem you can sail, or motor with and economical 2 hp Honda Four-Stroke outboard. Keep in mind that this is a part of the world where many boats are hand built by their owners in really small shops. One-offs are common. This particular boat looked like a manufactured product but again, I haven't seen one before anywhere. So, if anyone out there has any knowledge of this boat email me. Even better, if anyone has actually sailed one of these, let's hear about the experience.
Continuing with the theme I began in yesterday's post lets take a look at sea cocks and valves today. The photo below, again taken at the Mystic Classic Boat rendezvous over the past week end show one of the original sea cock valves used "back in the day".
Actually I see three gate valves in the photo above. This is a good example of the ABYC learning the hard way over time and adjusting what gets said within a standard as we learn about some of the real world problems that exist. In this case, as you look at the valves can you determine if they are opened or closed? I certainly can't, and that's the rub, and lesson learned. The valves could be opened, closed or somewhere in between, effectively restricting water flow, perhaps to an unacceptable level for the system being supplied with sea water. The valve on the far right side of the photo is the main sea cock supplying cooling water to the engine on this boat. If it's not opened all the way, the engine could suffer from water starvation and overheat, perhaps causing serious damage.
Also, assuming an emergency situation with water gushing into the boat and now it's time to close the valve. How many turns (and how much time) will it take to stop the flow of inrushing water?
So, in the photo below you see a different type of valve, in this case several "ball" valves.
The valves above happen to be installed in a boat's fuel system to control switching of fuel delivery from one fuel tank to another. What's more important here and really the lesson learned, is that the valves function in a 90 degree sweep from fully closed (as shown) to fully open (the handles in line with the piping). Categorically this is the preferred valve type today, and recommended in several ABYC Standards. Whether in a fuel system, or sea water valve, by using this type of valve you can instantly tell whether the valve is opened or closed and when you need to close it in an emergency, it just takes a quick flip of the valve handle to accomplish the task.
So, check your own boat and see what valve types you have installed. Replacement could be a very worthwhile project over the winter if you find gate valves in use.
This comes as the result of a question from Tom Bandoni, who is curious about the best product to use for his Aquarius 22 beach catamaran. He doesn’t want to use anti-fouling bottom paint, and is definitely interested in maximizing boat speed. He’s planning on leaving the boat in the water for a while and is of course concerned about fouling growth on the bottom. He’s perfectly willing to wipe down the boat’s undersides occasionally vs. using a poisonous anti-fouling paint system.
After a bit of research the available choices seem to narrow down to three primary options, each with very different approaches to solving this problem. Let’s begin with the most radical.
HullSpeed performance marine coatings are manufactured by Greenfield Manufacturing here in the US and are an epoxy/silicone blend that can be applied much like paint, providing a super slick coating. This system has been used in commercial, military and performance power and sailboat applications. This is not a system that is going to meet Tom’s requirements as the prep work involved before the coating is applied will be considerable. But, on a new build, or major bottom job, this is an intriguing option. Let’s say you were going to strip your boat’s bottom and apply an epoxy barrier coating anyway………this is the sort of coating that may have appeal to some boaters. The manufacturer claims that if kept clean, that is the occasional wipe down to make sure things like barnacles are not adhering to the bottom, several years of service can be expected from a typical 5 mil coating thickness. This can be further enhanced with the addition of a top coat from their product line called “SuperGlide”, which will reduce drag even further. The SuperGlide gets applied over the HullSpeed base coating simply by rubbing it on with a clean towel, much like applying conventional wax. The difference here is that this product is actually a catalyzed epoxy. Once the coating has been applied, buff it out in a circular motion.
Keep in mind that with the coatings mentioned here, there are two things to take into consideration, one is creating a surface that will enhance boat speed and reduce fuel consumption (in the case of power boats) but also to create a surface that is so slippery, that marine growth will have a hard time adhering to it.
Next up is a product called “Aqua Speed” made by German company Holmenkol. Unlike the above mentioned HullSpeed system, Aqua Speed is an ablative product that utilizes nanotechnology to fill microscopic voids in the base surface to achieve its extreme slipperiness. But, because it is ablative, service life will not be as long as with Hullspeed. In fact, the manufacturer claims that their base coat, called “Sport Polish” will last up to 12 months and the top coat, or Aqua Speed will last 5-7 days, but can be reapplied as needed over the Spot Polish base coat. As with the HullSpeed product, all old coatings and waxes must be completely removed before application.
It’s interesting to note that nanotechnology itself has raised many questions among some international groups about the toxicity and environmental impact of nano-materials, something that I’m sure can cause hours of debate among chemists. To find out more go to: www.envere.com (US distributor).
Last but by no means least in this round-up, Team McLube’s HullKote. For the environmentally concerned, this product is perhaps the friendliest of all. Its citrus based and its OSHA status is non-hazardous. The product’s MSDS (material safety data sheet) lists its ingestion impact as “low oral toxicity”, sort of like drinking a Margarita. Don’t try that with any of these products of course, but as a point of comparison the epoxy based Hullspeed could kill you and the Aqua Speed is quite questionable. The Aqua Speed sheet tells you to wear solvent protective gloves when working with the stuff, and not to induce vomiting if swallowed and does describe its ecotoxical effects this way: “Contains water polluting substances/water polluting classification: I/II.” Not sure how severe that is, suffice to say this stuff is not apple juice. All of the MSDS sheets for these products are extremely vague due to the proprietary nature of these products. But McLube claims that their product is considered GRAS (generally recognized as safe) by the FDA.
As for the McLube product, it certainly has received a lot of testimonials from the sailboat racing set as to its effectiveness. When you check out their website (www.mclubemarine.com) it seems like half the US Olympic sailing team and Volvo Ocean Race participants have something great to say about the products.
McLube HullKote is also the easiest to apply of the three products. It both cleans and polishes in one step according to the manufacturer. So, if the bottom surface is just bare gel-coat, you should be good to go. But in fairness, if your boat’s bottom has already had anti-foulant pain on it, just like the other products, you are going to have to get that all off first. But, once down to a relatively smooth surface, the McLube is just wipe on wipe off. Mclube claims it will last 20 days with hard use and certainly some of the Volvo Ocean race participants have confirmed this in their testimonials. With 2-3 coats of the HullKote, McLube claims it will last over 30 days in service.
So, my answer to Tom’s question is this: I am environmentally concerned and based on everything I can compare with these three products and his expectations, it seems like the McLube HullKote, with a service life of 20-30 days and an FDA “endorsement”, might just do the job for him quite nicely.