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Soundboats

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  1. Chick and PAR Actually I have tried all these methods in experimenting with scraps. First I use a dull 4" mason's chisel to try to crush the corrugations. However the thickness of the plastic did not allow for a good bend. It would only bend 90 degrees. I then tried using a plastic welder that has a narrow tip. This melted the layers together and the result was so thick that no bending was possible. I then tried heating a 1/2" metal rod in the oven to about 325 degrees and placed it on the plastic this created a larger melted joint but again it was very difficult to bend. The layers melted together producing a plastic that was 2-3 mm thick. I may end up using this method if I can work joint somewhat to make it more flexible. The easiest way I have found to bend the Solexx is to cut the top layer. Even then if I want the uncut side to be on the outside of the bend I have to cut the inside in a V shape to allow for the bend. I use an angled mat cutter on which I can adjust the depth. Each layer of the Solexx is actually thicker than two layers of the plastic used in most corrugated products for signs. If I can figure out how to work the Solexx I think it will provide a dinghy with quite a bit more strength. Tom
  2. I will be trying this out with a product called Solexx. This is a square corrugated plastic for greenhouses. It should be UV resistant. I have just enough left from covering the carport to try it out. However, this product is quite stiff and will require careful cutting of the inside layer of a crease because it will not crease well enough to hold a bend otherwise. This will be my winter project, and I will post the results here when I get it done. Tom
  3. Thanks Charlie, And yes I have found the Ken Simpson's web site. That is what got me interested in the subject. What was your source of the corrugated plastic? And how do they actually move in the water? Can you keep them going in straight line? This will be my winter project using a Solexx panel I have left over from building a shelter. Tom
  4. Thull, Here is a link to an outfit that sells all kinds of metals on the internet http://www.onlinemetals.com/index.cfm Their prices were very competitive when I was looking for aluminum tubes to make the masts on the Sharpie I built. When it comes to fabricating stuff out of metal I end up using high strength epoxy and stainless bolts. I never learned to weld and the epoxy and bolts have worked well for me (a trailer, an electric pickup, and a powered trailer dolly). When using epoxy with metals you need to have the surfaces perfectly clean - 600 grit emery cloth and several washings with acetone. Tom P.S. After 35 years of building and re-building (aka fixing stupid mistakes - such as using polyester resin and glass on plywood) boats I am on my third moaning chair; and it has to be a single malt Scotch!
  5. Hi, Have you tried Glen-L for the hardware? http://www.glen-l.com/inboard-hardware/ They have a bunch of uncommon stuff for mounting inboards and rudders. However, I bought my hardware from them for an inboard 20 years ago so I don't know what their current reputation is on hardware. They are very good for plans. Tom
  6. I am intrigued by some of the folding dinghies I have seen on the web using corrugated plastic. I am curious to find out if anyone has tried making one of these and is willing to share their experience(s). I have an 8ft x 50" piece of corrugated HDPE left over from a roofing project that is just begging to be used for a folding dinghy. Thanks Tom
  7. Hal, I have found that using the lbs of thrust rating on outboards is useful only for comparisons between trolling motors. The thrust advertised is measured with the boat pulling against a spring balance tied to the dock. It has little to do with the actual power under way since your prop is 0% efficient; it is not moving forward. If possible you need to measure the power being consumed by the trolling motor by measuring the current and the voltage at any one time. A 10 amp current at 12 volts = 120 watts. If you run that way for an hour you will have consumed 120 watt-hrs of energy. There does seem to be something wrong with your power equation. Let us say you are traveling at one knot using 513 ft-lbs/sec. This means you are traveling at 1.7ft/sec. Your equation would then give 513/1.7 = 301 lbs. So I don't think you can do the calculation the way you have. It just came out looking right using the numbers you had. I would stick with watts. You should be able to determine the maximum current used by a motor from the manufacturer's specs. The volts of the battery pack x max current = maximum power available to you in watts. Here are the numbers for my boat - A 26 ft St. Pierre dory with a 20ft water line. I have two 36 volt trolling motors are rated at 105 lbs of thrust. At my hull speed each motor is consuming 1200 watts of power. The boat and occupants weigh about 3000 lbs, so I am using about 800 watts per 1000 lbs of displacement to reach hull speed. This is actual power consumption including the losses in efficiency in the motor and the prop. My boat is strictly power, no sails. I originally had 12 golf cart batteries that gave me a range of about 20 nautical miles. I replaced them with lithium iron phosphate batteries and increased my range to 60 nautical miles within the same battery boxes (and lost 150 lbs of weight) Rick, Yes the trolling motors are much quieter than the electric outboards because the motor is underwater rather than on top of the power train. The other advantage of the trolling motors is that I separated the controls from the shaft. I mounted the motors and shaft on the outside of my hull on pivots and wired the controls next to the tiller in the cockpit. With regard to a 40# or 55# thrust motor - the actual difference in power consumption by the motors will be very little because the efficiency of the DC is steady across the full range of rpms. However, Your 55# thrust motor will probably have a larger prop (bigger pitch) and be turning more slowly so it will have a slight edge in the efficiency of the prop. So you may gain 5-10% in efficiency depending on the differences in the prop pitch and diameter. The larger motor will also give you a bigger margin of safety in case you get head winds. Head winds are like adding weight to your boat since they are expressed as resistance above the water, not resistance in the water. So the additional power can help. Currents however are expressed in the water. If either the 40# or 55# motors will get you to hull speed then there is no difference between them. Neither motor will be strong enough to get you above hull speed in a displacement hull. You will be moving at hull speed - current speed regardless. Tom
  8. Nice little motor. And, I would like to ditto some of the other comments. The critical factor in range is the power consumption of the motor and the storage capacity of the battery(ies). The watt-hrs stored (energy capacity) will determine the range at any specific power draw. Lead acid batteries, whether flooded or AGM, 2V, 6V, 12V or 24V, will store 17-20 watt-hrs per lb. Lithium batteries store about 46 watt-hrs per lb. With a motor drawing 300 watts you would need about 35 lbs of lead acid batteries for ever hr of cruising (300/17 = 17 lbs, but the lead acid battery should not be drawn below 50% capacity so that means a battery of about 35 lbs). You would need only about 8 lbs of lithium batteries for that one hour of cruising because lithiums can be drawn down to 10% of capacity without degrading their life span. A comment about efficiency. The critical factor in the efficiency of power transfer from prop to water is rpms and the pitch of the prop. Slow rpms where the pitch is about equal to the diameter provide the most efficiency. Most DC electric motors have a very similar efficiency of about 85 - 90%. The advantage of electric motors is that their curves of torque vs rpm are almost flat. That means the motor will put out its maximum power output based only on the current and voltage you are putting through - not on the rpms. So the big difference in efficiency between all of the electric propulsion systems is prop size and rpm. The Torqueedo has a 12" prop whereas the larger trolling motors have a 10" prop, so yes the Torqueedo is more efficient than trolling motors. However, in my experience the difference in price is not worth the slight loss of efficiency. As best as I can figure the Torqueedo prop has an efficiency of about 80%. This means that there is 20% slippage. Under ideal conditions a prop with a 10 inch pitch should move forward in the water 10 in for every revolution. An 80% efficiency means it actually moves forward only 8 inches in the water. My first electric boat was an inboard with a 16 " diameter prop with a 16" pitch. Hull speed was reached at 600 rpm and under these conditions my efficiency was 85%. Now I use two 36 volt trolling motors with 10" diameter props and I estimate my efficiency to be about 75% at hull speed (5.1 knots). So actually I am losing only 5% in efficiency by using the trolling motors instead of a Torqueedo. Trolling motors are designed to move big boats at low speed, so inherently they are fairly efficient at low speeds, and the Torqueedo can't do much to improve on that. Also, note that the power required to move a boat is independent of the motor used. It takes about 700 watts of power to move 1000 lbs of boat at hull speed under ideal conditions. If my prop is 75% efficient (and the DC motor is 90% efficient) I actually need about 1030 watts. If my prop is 80% efficient (and the DC motor is 90% efficient) I would need only 970 watts. Based on my experience over 20 years of electric cruising, the amount of energy used also depends of how much slower than hull speed one is going. If I were satisfied with going at 1/2 hull speed (2.5 knots for me) I would only used 1/4 -1/3 of the power needed for hull speed (about 200 watts/ 1000 lbs displacement). These numbers however, apply only to a displacement hull. A small boat with a planing or semi-planing hull would have different numbers. Tom
  9. For those of you interested in getting your exercise while building your boat I can also suggest using Japanese style pull saws to cut curves in plywood. These saws can be curved as you cut since the blade is so thin. The smaller blades with 15-20 teeth per inch are good for curves with a radius of 2ft or so in plywood that is 3/8" thick or less. The large blades are for larger curves and can be used in plywood up to 3/4 inch thick. I have often used these saws to cut plywood curves when I was too lazy to get out the power tools and only had a few cuts to make. I have had very good experiences with the Shark Saw brand of pullsaws. They have more than a dozen sizes of blades that fit into one of three handles, so you can just buy the blades as you wear them out. I am so pleased with this brand (mostly because it is about half the price of the usual Japanese pull saws), that I convinced Chuck at Duckworks to carry them. You can check them out on the Duckworks web site. Tom
  10. OK, I will have to beg to disagree. But, then this is what is great about these discussions. One can get many different opinions and make up their own minds. Not all cordless saws are "gutless." I was referring only to cordless jigsaws. As I mentioned I have had really good experience in building boats using the B+D Matrix small circular saw with plywood. I also use the Ryobi 1+ (18V) circular saw with a 5 1/2" blade. It will cut great through plywood that is more than 1/2" and it much lighter than the standard 71/2" plug in. As I get older I find I need to use tools that weigh less. It even cuts through a 2x6 or 2x8 without any problems. The Ryobi 1+ miter saw is also great for cutting all those little pieces that go into building a boat, and it is light enough to move from one end of the boat to the other. The cordless tools have one big advantage, I can have all of them ready to use without creating a hazard with all the extension cords around the boat I am building. Also, it lets me build my boats in an outside boat shed without having to snake a 12 gauge cord through the yard every time I go out and work. The Ryobi 1+ system has several tools I have found very useful in building boats. In addition to the miter saw, I use the router for rounding over stock lumber and the planer for fine touch ups. Note: These tools let me work inside the cabin when I decide that my original ideas really won't work, and I don't have to disassemble everything and bring it back into the shop. Yes cordless tools are not as powerful as the corded models, but more than adequate for building boats, especially smaller boats that don't require massive lumber. I have even found a 16" cordless chain saw (40volt) that lets me go into the forest to cut my firewood without waking my neighbors. My corded tools end up sitting on the shelf and may get used once or twice a year. I have not used my corded circular saw in over one year and my corded router has been sitting idle for much more than that. And, yes, having good quality saw blades is critical when using cordless tools. I have found that the circular saws by Freud (Diablo brand) are quite a bit thinner than the usual less expensive blades. But, because they are thinner the battery operated saws don't have to work as hard. Finally, I agree that lithium batteries are the only ones to use. The older cordless tools that used the Nickel-cadmium batteries suffered from the fact that the batteries were the problem. NiCads self discharged fairly rapidly and they had a "memory." If you charged them up without draining the battery completely, the next time you would have less power available.
  11. This hatch subject is of interest to many. I thought I would add my "two bits" with article that I wrote for Duckworks Magazine this spring. So here it is. My latest project is a 21 ft Sharpie for my daughter and son-in-law. Since my son-in-law is 6'3" and the cabin height is only 4 ft I decided that Phil Bolger's idea of a full-length cabin hatch was something I needed to include. The major problem I was facing, however, was a cabin length of 7 ft. A solid 7 ft hatch would have been quite heavy and difficult to hinge along one side. I liked the ideas of Gary Blankenship I saw in Duckworks Magazine, but it still seemed a bid daunting. I had almost decided to scrap the full length hatch when I realized that the hatch does not have to be solid. What if the hatch is made of a marine vinyl cloth that can be slid along the hatch coaming? This concept has been discussed, but I have never seen anyone trying it. Well, there is always a first time, so I decided to try it. Here is a description of my first attempt, and I think it will work. The basic structure is marine grade vinyl fabric stretched onto wood ribs with the ribs having small blocks that ride in aluminum U-channels that are attached to the outside of the coaming (Figure 1). Figure 1 Figure 2 shows a rib made out of 1x3" lumber with ¾ " square wood extending down the sides. The slides are 1.5 inches wide and can be any height that is a little less than the opening of the aluminum channel. I used some ¾" x 1.5" PVC trim boards I bought at Home Depot. Figure 2 I use PVC to keep the sliding friction to a minimum (Figure 4). The picture also shows the ¼ inch shim I used to set the exact distance as I attached the slide. Figure 3 I cut the vinyl width so it was exactly the distance along the outside of the rib, plus 2" for hems (1" on each side). In my case that was 23.5 + 2" or 25.5". Then I hemmed the sides with 1" hems. This width gave me enough material so the truss head screws I used to attach the vinyl to the ribs would go through 2 layers of material. To simplify the process of attaching the vinyl to the ribs, I used double sided, exterior grade, foam tape. I used the 3-M product since past experience has shown that this works best for me. Other brands such as Harbor Freight, don't last long in the harsh marine environment. I put the tape first on each rib and then taped the rib to the vinyl along lines I had drawn. The truss head screws were used to permanently fix the vinyl to the ribs (Figure 5). Figure 4 The final step was to attach a gate latch to the outermost ribs (forward and aft) on each side. These latches had a ¼" rod that could slide into predrilled holes in the coaming. The cover is now in place and can be opened from either the bow or the stern. The vinyl and ribs can be compressed to about 1 ft, so actually this in not a hatch that spans the entire cabin. However, it can be opened from either end and will not interfere with the handling of the mainsail. I have not yet finished the boat, so don't have a discussion of how it actually works in reality. However, the initial set-up and testing suggest it will work well. The hatch can be opened while under-way. I bought the vinyl at Rochford supply. They often have the best prices. They have different grades and colors so you can pick and choose what you want. P.S. The boat has been in the water now and the hatch is very effective at keeping the water out whether rain or spray.
  12. As the post above just stated... It's all a matter of opinion and preference. For me, it all depends on what I am cutting. If the curves are tight then a jig saw is what I use. My experience is that cordless jigsaws just don't have the speed and power for smooth cuts. If I need a jigsaw I use a corded one. That said, however, I have had very very good experiences in cutting shallow curves (larger than a radius of 4ft or so) in plywood with the saw attachment on the Black and Decker Matrix 20V tool. The carbide blade is only 3 3/8" in diameter, quite thin, and extends 3/4" below the platen. It will cut well in plywood that is 1/2" or thinner and with the 4 amp-hr battery will last for about 30ft of cuts in 1/2" ply. I have two batteries in case the first one dies before I am done for the day. It is also much lighter than a corded 7" circular saw or even a 5" cordless saw. I could easily make cuts that were at shoulder height. I used the Matrix to cut the plywood sides and bottom on the 21' Sharpie I just finished. It was a lot faster than a jig saw and resulted in much smoother curves that required very little planing to get a nice fit. Before I had the matrix I used a jig saw and that resulted in wavy curves... so I had much more planing to do. Also I could not control the lateral pressure on the saw on large sheets of plywood. This sometimes resulted in the blade not cutting perpendicular to the plywood sheet.
  13. OK I stand corrected. I agree that plywood will work for frames if they are circular and the stresses can be transmitted around the entire piece. The same can be said of a solid frame that spans the entire cross section of the hull (e.g. a transom). I am not familiar with the design of the kayak being discussed, and did not realize it has "circular" frames. My reference to not using plywood for frames regards frames that are U or V shaped where the frame has to bear the pressures only along one side. I have used plywood with a hole cut out in the middle for the first and last set of frames (bow and stern) in the Rob Roy canoes I have built. I have never had problems with plywood in these situations in the 9 canoes I have built. Tom
  14. John, I would not use plywood for the frames. if you cut a strip of plywood you will note that half of the layers will have the grain perpendicular to the long side. This grain has very little strength when compared to grain that runs parallel to the strip. So as a rough estimate, a frame of 1/2 inch ply will have only 1/2 the strength of a similar sized piece of wood. The value of plywood in boat building is its ability to span large surfaces without the need for joints and its resistance to punctures. However, it does not compare well with regular wood in terms of bending strength. Furthermore, plywood has very little resilience (bounce back) compared to regular wood. This ability to absorb shock and bounce back is critical in frames. You can convince yourself of this by doing a simple experiment. Cut a 1" strip of 1/2" (or 3/4") plywood that is 18" long and a strip of wood of similar size. Put each piece between two blocks and add weights to the middle until the strip breaks. Instead of weights I like to use a 50 lb hand held scale and hook it to the middle - pulling either up or down.That will be give you an idea of how the different materials compare. You can use this technique as well to test the breaking strength of different woods you might be able to purchase at the lumber yard. Tom
  15. Hi John, There are several small boat designs called the Curlew. Which one is of interest to you? The one by Devlin Boats? So I can't comment on your choice for stringers and gunwales. Generally dimensional wood and plywood is OK if you are selective. Start visiting your Home Depot and Lowes and look for clear lumber with tight (closely spaced) growth rings of the sizes you want. There may be one or two pieces in each batch that are great. Pick through them and purchase just the good ones, and start stockpiling them. With plywood I would avoid the standard A/C in the thinner sizes. I have found that 5mm underlayment plywood really works well for the thinner sheets. In Florida you might be able to find A/B pine plywood which I think works better. Home Depot does carry plywood from Ecuador that has almost no voids in it and more plies than the usual (1/2" has 7 plies instead of 5). I have build two boats with it with great success. In any case, I have always covered regular plywood that is not marine grade with glass (4 or 6 oz) and epoxy (just in case there is a void somewhere that might cause problems). I add pigment to the epoxy so I don't have to worry about painting (ever!). To avoid possible degradation of the epoxy from UV sunlight I spray several coats of satin marine spar varnish on (Minwax Helmsman Urethane spar varnish is the brand I use since it is the only brand I have found that also comes in a spray can). Three cans were enough to cover the 21 ft Sharpie I just finished. Tom
  16. Hi, I just redesigned a Marconi rig to a Balanced lug for the sharpie I just completed. Rather than starting to figure out the relationship between CE and CLR for the boat and changing it, I drew up a balanced lug with the same CE (in the vertical location) as the original sail. Here are my suggestions based on what I did, and it did result in a balanced sail plan that sails quite well. 1. On a scaled drawing draw the mast and the triangular sail. I suggest you use 2 inches to the foot for your 10' Spindrift so small errors in drawing and measurements won't cause problems. I used the standard scale of 1" to the ft because my boat was 21ft. 2. Then draw a line perpendicular to the mast roughly where the hull starts (or even better draw the entire hull to scale). 3. Find the CE of the original sail draw a vertical line down to the "hull." This is your starting diagram. 4. Now you can try out different sail patterns for the balanced lug. Calculate the CE for each design and place it (or draw it) on your starting diagram. The goal is to make sure the CE of the balanced lug lines up anywhere on the vertical line or the original CE of the triangular sail. 5. You should also use the scaled drawings to calculate sail area. The total area of the balanced lug should be about the same as the area of the triangular sail, unless you consciously decide to make it bigger or smaller (bigger means more powerful and maybe difficult to sail, and smaller means you won't be sailing as fast) If you don't know how to calculate the CE of a sail, most books on sailmaking describe how to do this. Your local library should have some of the standard books on this. I used The Sailmaker's Apprentice by Emiliano Marino. Finally, I suspect you will probably be making your own sails. If so, I suggest you start with the much less expensive Polytarp sails. This will let you experiment with different designs at a minimal cost. If the first one doesn't work out you won't feel like you have wasted a lot of $$ on a dacron sail. Tom
  17. Rick, I am somewhat confused. I was unable to find the specs for a Great White 50. All they now have is a Great white 82 lb/24 volt and an 105 lb/36 volt. Just to get you started here are some numbers that I come up with. Assuming you want to more 1200 lbs at hull speed you will need a motor that produces about 900 watts. The 36 volt Great White I have consumes about 1080 watts at maximum power (30 amps +-). I don't have the specs on the 24 volt version but I expect its max power is slightly below 900 watt. Lithium cells are rated at 3.2 volts so you would need 12 cells to make up the nominal 36 volts. The actual voltage of the pack is closer 40 volts when fully charged. The trolling motors were designed for lead acid batteries, but the slightly higher voltage should not cause problems. I checked with Motor Guide and the max voltage for the motor is 49 volts but they refuse to commit themselves to saying that lithium batteries are OK. However, I have had lithiums for two years without any problems. If you go with the 24 volt motor you will need 8 cells. Your comment about 1-2 20-25# lithiums confusing. The smallest "pristmatic" lipo cell is 40 amp-hrs and they go up from there to 60, 100, and 180 amp-hrs. At 40 amp-hrs you will have 40 amp-hrs x 38 volts = about 1.5 kwatt hrs of energy. If your motor is consuming 1000 watts/hr your cruising time will be a little less than 1.5 hrs. You do a similar calculation for the 24 volt motor. For example, assume you motor consumes 800 watts at maximum throttle. 8 of the 180 amp-hr cells would give you about 4.8 kwatt hrs of stored energy and about 6 hrs of cruising time. Here is a sample of the CALB lithium cells available and a reasonable pricing . This is from http://evolveelectrics.com/calb/ CALB 40Ah CALB 40Ah - 3.2V LiFePO4 Battery $60.00 CALB 70Ah CALB 70Ah - 3.2V LiFePO4 Battery $95.00 CALB 100Ah CALB 100Ah - 3.2V LiFePO4 Battery $140.00 CALB 130Ah CALB 130Ah - 3.2V LiFePO4 Battery $182.00 CALB 180Ah CALB 180Ah - 3.2V LiFePO4 Battery $252.00 CALB Busbars Laminated copper busbar to fit each CALB battery variant. $3.50 Tom
  18. Hi Bill It all comes down to cost vs. weight, vs. longevity. Sealed lead acid batteries cost about $210 per kwatt-hr. A 6 volt 200 amp-hr sealed battery costs about $250 and it stores 6 v x 200 amp-hrs = 1.2 kwatt-hrs. However, you only have about 60% of that capacity that is usable. Lead acid batteries should not be taken below about 40% of their rated capacity. If you do, the number of charging cycles you get is significantly reduced. So your initial costs are about $350 per kwatt-hr of usable energy stored for the AGM batteries. This is about the same for either 6 volt or 12 volt batteries. The AGM deep cycle batteries at this lower price range have an expected life of about 500 charge discharge cycles (or 5 years whichever comes first). Thus, over the life span of the battery you will end up paying 350/500 = $0.70 per kwatt-hr used in you electric motor. There are sealed batteries used in the solar world that are good for about 1000 -1200 cycles but they cost double. Lithium iron phosphate batteries cost about $450 - $500 per kwatt-hr of energy. This includes the needed battery management system. One advantage of lithium batteries is they can be drawn down to 10% of their capacity. This means that 1 kwatt-hr of usable stored energy costs $500 for lithium compared to the $350 for the lead acids. However, lithium cells are good for over 2000 charge discharge cycles. Thus if you look at the cost of power amortized over the life span of the batteries, one kwatt-hr of power to your motors actually costs only $0.25/kwatt hr. The large capacity lithium batteries have been readily available for only 5 years of so, so we don't have any data on their longevity. One report from a dealer in parts for electric cars found that the cells lost only 10-15% of their capacity after 5 years. Another advantage of Lithiums is that they take up about 1/2 the space (volume) of lead acid batteries for that 1 kwatt-hr and weigh less than 1/2. Lead acids weight about 50 lbs per kwatt-hr of rated capacity regarless of voltage. Lithiums weigh about 23 lbs per kwatt hr of rated capacity. When I replaced my lead acid batteries (15 kwatt-hrs of total energy) with lithium batteries in the same space I was able to get 28 kwatt hrs of stored energy and thus more than doubled my cruising range. So my lead acid batteries were good only for about 10 kwatt hrs of cruising while my lithiums are good for 25 kwatt-hrs of cruising within the same space and weight. If you cruise in a cold climate be aware that lead acid batteries have a reduced capacity when it gets cold. At freezing a lead acid battery has only 1/2 of its rated capacity, while the CALB CA lithiums (the brand I have) are reduced only by 8% at freezing. So you will have to juggle the different variables to meet your needs. If you cruise only a few dozen times a year in a warm climate, and have the space and can carry the weight, then the lead acid batteries are just fine and more cost effective. If you are interested in the large capacity lithium iron phosphate batteries you will need to explore the web sites that sell parts for electric vehicle conversion. I have had good experience with the CALB 180 amp-hr cells in both my boat and in my electric pickup truck. One thing to note about lithium batteries. The "cells" are only 3.2 volts so you will need to put together more of them to achieve your desired voltage. Lead acid cells are 2.1 volts but the manufacturers put them together for you in 6.3 or 12.6 "batteries." Also note: the lithium iron phosphate cells (LiPO4 or LiPo) are the not the same as used in electronics or the Tesla. LiPo cells are much more stable and don't suffer from the temperature (and in extreme cases, explosions) that the lithium ion cells do. Tom
  19. Trying to estimate the cost of building a boat is always difficult but I wanted to give you an idea of what you might expect. As an example I will do a rough estimate for the Glen-L 18' sailing dory. The Glen-L plans are suited for a beginner because they provide full sized patterns for all the important parts. No need to learn how to loft. Here is the blurb from their web site Our ALPHA-2 is even faster and cheaper to build than ever before! Built over a simple temporary form, the hull has no permanent frames. Only a little over six sheets of standard sized plywood and a few board feet of lumber are required. And with our comprehensive plans featuring Full size Patterns, no lofting is required (although dimensions for the hull are given for those who wish to go through this exercise). Detailed instructions cover all phases of the construction making this a simple project even for the amateur. The ALPHA-2 features a centerboard and shallow draft rudder for easy launching and beaching. Steering is accomplished by a rudder yoke and stern sheets, however, a tiller can be fitted optionally. Wood spars are detailed in the plans, or you can us an aluminum spar (see Dwyer.com). Here is an approximate cost estimate as best I can make it: 7 sheets of plywood = $175 1.5 gal. epoxy resin (from Duckworks) = $100 ($200 if you want to coat the inside as well - I would recommend that) I would use some of the epoxy with a filler such to make epoxy glue where needed or use polyurethane glue = $10 fiberglass cloth (12 yds of 4 oz cloth = $72 (from Duckworks) Lumber = $100 Sails (polytarp) = $100 Polyurethane varnish or paint to cover the epoxy and protect it from UV (I use polyurethane porch paint that is 1/4 the price of marine paints) 1 gal = $30 Aluminum tubing to be used as spars and mast = $150 (a metal supplier will have this much cheaper than an outfit that caters to the marine world) Hardware and lines = $300 (again here I go outside the marine market - I have found marine grade polyester braided rope at half the price sold by stores that cater to horses and horse equipment. The colors may be limited but the prices are great) Plans from Glen-L = $120 So the basic cost of materials for this sailing dory comes out to about $1100 - $1200. Adding oars, life jackets, small anchor and safety equipment will add another $400 - $500 or so to the price. The trailer however may easily add another $1000 to the price if you buy a galvanized marine grade trailer. This is where looking for a used one may pay off. Tom
  20. Hi David, I would suggest checking out the different plans on the Glen-L web site. They have a number of sailboats in the 14-15 ft range. https://www.boatdesigns.com/Sailboats/departments/12/ AND their designs can be built with inexpensive lumber from your local Home Depot and Lowes. If you decide to use lumber from these sources, however, I suggest you start stocking up early. You can usually find several clear pieces of lumber in each batch, but you have to pick through a pallet and then wait until the next one to come in several days later to build up your supply. Since you are on a tight budget I also suggest that you look into making sails using the polytarps rather than dacron. A kit for a boat this size would only be about $100. If you do decide on polytarp sails I suggest you read the slight refinement I have proposed to the original plans provided by Dave Gray. I was able to make my sails without wrinkles on the first try. http://www.duckworksmagazine.com/15/chest/apr/index.htm#.VWOV7E9Viko I am also going to stick my neck out and suggest you look into using regular plywood with a coating of glass and epoxy if you are on a tight budget (rather than marine plywood). I know there are some very strong feelings among boat builders on this subject, but that is the way I have been building boats for 35 years, and it works for me. Home Depot carries (sometimes) a line of plywood made in Ecuador that has few voids and more layers than the standard construction plywood. Below is a picture of the Glen-L 14 that might seat four. Good luck. Building a boat from scratch is always a very rewarding activity. Tom
  21. This is an old post, but I wanted to add my "two bit's worth ". To start I am not a proponent of either dagger boards or center boards. They tend to jam or get filled with sediment whenever a boat is beached. My preference for beachable sailboats is bilge keels. These have a long tradition in Europe, especially in England, but for some reason in disfavor here in the US. I won'the go into the arguments pro and con since these discussions on the Web on this are already quite extensive, especially on its sailing characteristics. Here in the US, Phil Bolger seems to have been the only proponent of bilge keels. I favor this design because: 1. It simplifies hull construction in small boats (no need to worry about the torque on the box creating leaks) 2.It allows for easy beaching and sailing in shallow waters 3. Bilge keels that are about 1/2 the length of the bottom do not have to be very deep. My little logo shows the 21 ft Sharpie I just finished. The bilge keels on it are only 9 inches deep and 10 ft long but their cross section is equal to that of the 3.5 x 6 ft centerboard in the original design. 4. With the tiller hanging off the stern it turns easily and does not fall off the wind when tacking. Tom
  22. I checked out the wooden boat forum and this is what Bob Smalser had to say. Our three "lightweight" cedars are predominantly used as planking woods for in thicknesses varying from 3/8" to 1 1/4" on boats up to around 35'. They are around 25% lighter (and correspondingly weaker) and proportionally more stable than our four "heavy" cedars, which are generally used to plank larger boats and also sometimes for framing. The heavy cedars are Alaska Yellow, Port Orford and Eastern Red Cedar. These are closer to Doug Fir in weight, hardness and strength than they are to the light cedars. Baldcypress has similar properties and can also be included in this group, as most of the trees we call "cedars" are really in the cypress family. Eastern Red is the heaviest of the group and not normally used for boatbuilding. The light cedars are Northern White (Arborvitae), Atlantic White (Juniper) and Western Red. Of the three, NW is lightest by a slight degree and bends the best. The trees are generally quite small however, with usually only knotty flatsawn stock available. Western Red comes from the largest tree, making clear, stable vertical grain stock easily available, but is a significantly stiffer wood than the other two. All have rot resistant heartwood, all are easy and pleasant to work, all take glue exceptionally well, and all are among the most seasonally stable of woods. Qsawn light cedar panels through widths of around three feet can be successfully epoxied and glassed just like plywood. They are also relatively soft, but boats protected by nothing but paint hold up very well in hard use. I personally have used California redwood sold as porch decking sawn into thin strips. I don't know if it is still readily available. If you want a general description of woods used in boat building check out this page from Glen-L https://www.glen-l.com/wood-plywood/bb-chap5d.html Tom
  23. Hello, I just came across this very interesting discussion and would like to add my suggestion. I don't know if my comments will still be helpful since the last post was over 6 month ago. Anyway.... I see that no one has mentioned Glen-L marine that provide plans for many different type of boats of different sizes. Most of their plans are for plywood construction and sometimes they even have full sized patterns for the ribs, transom, and stem. They have a nice trailerable 25' cabin cruiser that might meet your needs http://www.boatdesigns.com/25-Coastal-Cruiser-trailerable-motoryacht/products/802/But, in any case it is always fun to look at their inventory of over 300 plans. I myself have built their 26' St. Pierre Dory and cruised it extensively in Puget Sound. It is one of the safest boats in which I have ever been but its hull speed is only a little over 5 knots (it has a 20' water line). That said however I can get to hull speed with only the equivalent of a 6hp gas engine. The nice thing about this design is that Glen-L provides plans for an inboard with a shaft that can be lifted into the hull for trailering or beaching. I use a regular bimini top over the cockpit to keep out the sun and the rain (we are in the Pacific Northwest) Tom
  24. Thanks Chick, Looks like I got the last one of these on the used book option. New copies no longer seem to be available. Tom
  25. I will answer Rick and then Chick, First Rick: Yes the Torqueedo is quite pricey and I think over-rated compared to the trolling motors available for a lot less. I have studied the specs for the Torqueedo and I think their ad campaign doesn't address the real issues in using electric for longer cruising. Their propeller is slightly larger than that of a 36 volt trolling motor (12" vs 10") so they will be slightly more efficient, but not so much more to warrant the cost difference. The efficiency of a prop is based on diameter and pitch and rpm. The calculations are nicely described in the book that Chick mentions and that I often use. My first dory had an electric inboard motor with a 16x16 inch prop. I would get to hull speed at about 600 rpm and had an efficiency of about 85%. The trolling motors and the Torqeedo are in the range of 70-80% because of smaller diameters and higher rpms. So yes, I might need only 1800 watts of power to move my dory with a Torqueedo when my trolling motors require 1900 watts to maintain hull speed. Based on my calculations and experience you need about 700 watts of power to move 1000 lbs of displacement at hull speed (My dory is about 2800 lbs and needs 2000 watts to move it at hull speed; if I am willing to go 80% of hull speed my consumption drops to 1300 watts). A Torqueedo is a 24 volt motor so it will need to a current of 30 amps to move 1000 lbs of displacement at hulls speed. The largest Torqueedo lithium battery (at a very expensive price) stores at most 2600 watt-hrs of power. That means at 30 amps the torqueedo will provide about 3 hours of cruising time using their largest battery for a boat weighing 1000 lbs. If your boat weight 2000 lbs that reduces the cruising time at hull speed to 1.5 hours. For comparison I had 15,000 watts-hrs of energy storage in the lead acid batteries I first used, and now I have 28,000 watt-hrs in the lithium batteries. The lithium batteries take up the same amount of space as the lead acids and weigh about 630 lbs. compared to the lead batteries weighing 800 lbs. The other big advantage of the lithium batteries is that they can be taken down to 10% of their capacity without a reduction in battery life. Lead acid batteries should not be taken below about 40% of their rated capacity. In addition Lithiums are usually rated at over 2500 charge/discharge cycles whereas the less expensive lead acids are usually good for only about 600 cycles. Anyway the cost and capacity issues is another whole topic and worth a separate thread if there is interest. I have done extensive calculations on cost per mile and the lithiums come out close to the flooded golf cart batteries and lower than the AGM type batteries if you do extensive cruising. The one disadvantage of lithiums however is that you will need a battery management system (BMS) since they are very sensitive to overcharging and full discharge. You can buy batteries with a BMS included but that doubles the price of the batteries. If you are willing to attach it yourself you are looking at about 5-10% the cost of the batteries. I personally have had a good experience with the Mercury electric outboards (called Motor Guide Great White). These are a bit less expensive than comparable Minn Kota motors. I have been cruising with the Mercury Marine version for 7 years now without any problems. The nice thing about the trolling motors is that I can remove the head from the shaft and mount the shaft separately on pivots along the side of the boat (see previous photo). There throttle only needs two small wires to the shaft and the main power cables can be placed separately. This you cannot do with the Torqueedo. If you want test data, I have been collecting it myself for 17 years so can try to answer questions you may have. By the way, lbs of thrust have little meaning when you are trying to figure out power needs for cruising. And, don't fall for the Torqueedo hype about horsepower. Generally 1 true electric horsepower (=750 Watts) is equal to about 3 hp of a gasoline engine. In that sense the Torqueedo is no different than the trolling motors. So if Torqueedo rates its motor as equivalent to a 6hp gas outboard it is actually putting out about 1500 watts (but at 24 volts that would require a current of 60 amps). Each of my trolling motors is rated at 1080 watts and the max current is 30 amps at 36 volts. Electric motors are close to 90% efficient at transferring power regardless or rpm. This is not true for gas motors. Hope this helps. And now Chick. Yes I have the book by Douglas Little. It was what got me started in the first place. It does cover many of the basics, but the technology has now improved significantly with trolling motors and the Torqueedo, and different battery technologies. Now that I am retired I am considering writing an update that includes discussions of electric power for larger boats. There is another venue called "Electric Seas" on the web where we do discuss and share experiences, but few people have found it. Tom
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