capnrazz Posted January 4, 2005 Report Share Posted January 4, 2005 Hi Graham, I bought plans for Princess 26 #7 a few months ago. I plan to outfit it with an electric outboard in the 6hp range and a 60v 210 amp hour (12kWh) battery bank as a minimum. We exchanged a couple of emails about this over a year ago before the Princess plans were completed. We're talking about either 10 6v batteries or 5 8d 12 volt batteries with a total weight between 650 and 1000 lbs depending on which batteries. The narrowest 12v I found for this kind of capacity is 5"w x 13"h x 22" long 131lbs for an 8D type 210ah 12v Northstar AGM. Lifelines GPL4C 6v 220ah is about 10.3"l x10.3"h x 7.2"w, 66lbs. There are quite a few options in the 7.5-8"w range from Trojan, Rolls, and others. The largest battery I would consider is the Rolls modular 12-hhg-325-hsm at 200lbs each 325ah and 21.75"L x 13.25"w x11.5"h. The individual self-contained 2v cells for this modular battery are 5.75w x6.25"L x 10.75"h and could be bolted together in a single long string in a keel box if removed from their battery boxes. I like this idea because the individual cells only weigh about 32lbs each, and would be easier to handle. Would it be practical to build a centerline box keel to house these as optimum ballast, or would it work about as well to distribute them under the settees and save the trouble? What would be the approximate effect on the stability curve for these two options? Thanks Razz Quote Link to comment Share on other sites More sharing options...
Designer Posted January 7, 2005 Report Share Posted January 7, 2005 capnrazz, After looking at the plans it would not be possible to fit any of your options in the keel without raising the cabin sole or increasing the draft and lengthening the keel. I like the 2v cell option but I presume that you will need 30 to get your 60v which adds up to a length of 15' 8". That is about 50% longer than the standard keel and they would weigh close to 1000#. I think that I would go with the lightest combination with the lowest height and put them under the setees as close inboard as you can. I ran a calculation with 700# of batteries with their combined cg at 4 1/2" above the WL. It raised the boats CG 1" which means that when you factor the extra weight into the righting moment you will have at least the same stability at normal sailing angles but you will have less ultimate stability in the case of a knockdown. How much less depends on the many options that you will choose in building her. Quote Link to comment Share on other sites More sharing options...
Greg Luckett Posted January 8, 2005 Report Share Posted January 8, 2005 capnrazz, Assuming you were able to do this, how would it affect the displacement of the boat and the number of possible passengers? Greg. Quote Link to comment Share on other sites More sharing options...
MikeY Posted January 8, 2005 Report Share Posted January 8, 2005 I bought plans for Princess 26 #7 a few months ago. I plan to outfit it with an electric outboard in the 6hp range and a 60v 210 amp hour (12kWh) battery bank as a minimum. My first post on the forum. Thanks for letting me in! Just an out-of-the-box thought. I work at a research lab where we build undersea vehicles. We have one that is powered by over 9,000 (yep, that many) D-cell alkaline batteries. They could be rechargables. They are slotted in tubes for easy placement. The D-cells allowed the designers to fit them into the form of the vehicle much better than larger cells. Also, there was a DARPA program on micro air vehices that achieved it's goals by making the batteries part of the structure too. Diameter 38 inches Length 28 feet, 6 inches Displacement 10,000 pounds Range 500 nautical miles at 4 knots Payload Volume 10 cubic feet (approximately) Power Source (initial) Alkaline Batteries (quantity 9,216) http://www.arl.psu.edu/capabilities/us_sea_syseng.html Quote Link to comment Share on other sites More sharing options...
Guest Posted January 8, 2005 Report Share Posted January 8, 2005 Welcome and thanks for taking the time to share this with us. What is the skin made out of, on the exterior? I read that it used divinicell was for boyancy, but is it incorporated into the actual skin, too? Quote Link to comment Share on other sites More sharing options...
MikeY Posted January 8, 2005 Report Share Posted January 8, 2005 Welcome and thanks for taking the time to share this with us. What is the skin made out of' date=' on the exterior? I read that it used divinicell was for boyancy, but is it incorporated into the actual skin, too?[/quote']No it's not. The vehicle is very modular. Not sure what the skin is (not my project), either aluminum or composite attached to an underlying frame. The skin is not a pressure bulkhead. Quote Link to comment Share on other sites More sharing options...
capnrazz Posted January 9, 2005 Author Report Share Posted January 9, 2005 Greg Luckett wrote: Assuming you were able to do this, how would it affect the displacement of the boat and the number of possible passengers? If I'm interpreting the specs correctly the boat has a payload capacity of around 1000lbs at 3700 lb design displacement with 700lbs of ballast in place. The pounds per inch immersion is listed as 498. So if I built it with the 700lb ballast keel as designed, the total weight of the electric installation + 2 crew and gear for a week's cruise would probably push displacement to around 4500lbs for about 2 inch increase in waterline depth. I imagine this would nail the boat firmly in the displacement speed range. Without the ballast keel and sailing light she would be more likely to plane in a breeze. My intended use is primarily daysailing and weekending out of Big Water marina on Lake Hartwell, SC-GA border where I currently keep a Gloucester 22. A few times a year I may make longer cruises between marinas on the lake or trailer to the coast for inshore vacation cruises. The freestanding tabernacled rig will make it possible to get under bridges on the lake, opening up 1100 miles of shoreline and 60 miles of lake to camp cruising. From Big Water I have 14 miles of open water until you hit the first bridge on the main body of the lake. A 12kWh battery on either an OEC or RAY electric outboard should give around a 25 mile range under power alone at 5 knots, that increases to 40 miles at 4 knots and shrinks to about 8 miles at 7 knots based on calculations for a 2 long ton boat with 25' lwl. This is roughly equal to the range of my Gloucester with a 6hp 2 stroke and 6 gallons of gas, except the the Gloucester will only make about 6 knots max with the Evinrude. So 650lbs of lead acid battery is about equal to 6 gallons of gasoline. Question for Graham: If the boat is built with the shoal keel and ballast shoe as designed and I use the Northstar batteries (650lbs) turned on their side under the settees so the height above hull is about 5 inches what would the displacement and stability curve look like? Razz Quote Link to comment Share on other sites More sharing options...
capnrazz Posted January 9, 2005 Author Report Share Posted January 9, 2005 Mike wrote: "Just an out-of-the-box thought. I work at a research lab where we build undersea vehicles. We have one that is powered by over 9,000 (yep, that many) D-cell alkaline batteries. They could be rechargables. They are slotted in tubes for easy placement. The D-cells allowed the designers to fit them into the form of the vehicle much better than larger cells." Interesting idea. The Honda Insight hybrid uses a battery pack of 120 NiMH D-cells. Cost Vs capacity Vs cycle life is too high currently for the more exotic battery chemistries for this application. There is an interesting new lead acid technology that has been spun off from Caterpillar as a startup called Firefly Energy. It reduces the weight for a given capacity by 70% using some kind of lead/polymer matrix for the grid plates. There is also some reduction in size vs capacity too and the polymer grids are impervious to sulfation and positive plate corrosion that limit the life of conventional batteries. Supposedly they can be manufactured on existing lead acid infrastructure at comparable cost. These may be available by the time this boat is built. Quote Link to comment Share on other sites More sharing options...
MikeY Posted January 9, 2005 Report Share Posted January 9, 2005 I had this vision in my mind of the keel being made out of D-cell batteries. Some fairing fore and aft (use AAA's?). Have your cake and eat it too. Of course then you'd have to try to find a way to harness your excess wind to recharge them, via dragging a prop with an alternator setup. Thinking as I'm typing here...one could build a modular add-on keel to a boat that would contain batteries, prop, and motor/generator all in a single bolt-on package. That'd be a cool project. Maybe just the generator and deployable prop on the keel, use a standard troll motor. :wink: Quote Link to comment Share on other sites More sharing options...
Greg Luckett Posted January 9, 2005 Report Share Posted January 9, 2005 What sort of Northstar batteries are you speaking of? Quote Link to comment Share on other sites More sharing options...
capnrazz Posted January 9, 2005 Author Report Share Posted January 9, 2005 Greg L wrote: "What sort of Northstar batteries are you speaking of?" I ran across these during a web search on battery technology. They are a sealed VRLA absorbed glass mat type lead acid battery, so they can be installed in any orientation except upside down. PDF attached. Razz [attachment over 4 years old deleted by admin] Quote Link to comment Share on other sites More sharing options...
capnrazz Posted January 9, 2005 Author Report Share Posted January 9, 2005 Hi Mike, We're thinking along the same lines regarding the box keel. My dream setup would be a somewhat larger boat, around 30' with a Solomon Technologies ST37 inboard motor and about a ton of batteries in a ballast keel. The Solomon motor has a regen mode to charge the batteries under sail with a freewheeling prop. I will look at the possibility of using NiMH D cells for the Princess, but they are likely to be rather expensive compared to 8D AGMs for the capacity required. Finding or building a proper charger for them would be a challenge too. Trolling motors would work OK for short distances on boats up to the size of a Princess 22, but are not built for continuous operation as primary propulsion units. The controllers will overheat and fail if run for more than 20 minutes or so at a time at near maximum current. This is a much discussed problem on the eboats.org forum. By contrast the OEC motor has pushed an 8000lb sailboat to 7.5 knots and will run continously at 80% of maximum current for as long as your battery lasts, producing nearly 200lbs of thrust, compared to about 60lb max for a heavy duty trolling motor. The trolling motor would be good for only 3-1/2 knots or so on a 2 ton boat maxed out. The OEC outboard equals the thrust of a 9hp gas motor. Quote Link to comment Share on other sites More sharing options...
Greg Luckett Posted January 10, 2005 Report Share Posted January 10, 2005 Greg L wrote:"What sort of Northstar batteries are you speaking of?" I ran across these during a web search on battery technology. They are a sealed VRLA absorbed glass mat type lead acid battery' date=' so they can be installed in any orientation except upside down. PDF attached. Razz[/quote'] Razz, I cannot seem to see or download this picture. Do you have a link to the information? Thanks. Quote Link to comment Share on other sites More sharing options...
capnrazz Posted January 10, 2005 Author Report Share Posted January 10, 2005 Northstar battery Link: http://www.northstarbattery.com/index.php Razz Quote Link to comment Share on other sites More sharing options...
Greg Luckett Posted January 10, 2005 Report Share Posted January 10, 2005 That works. Thanks. Quote Link to comment Share on other sites More sharing options...
MikeY Posted January 10, 2005 Report Share Posted January 10, 2005 This is a much discussed problem on the eboats.org forum. Ahhh, didn't know there was such a thing. Way ahead of me. Neat site. Quote Link to comment Share on other sites More sharing options...
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