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    Olympia WA
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    I am interested in small boats that can built by most. Over the last 40 years I have built 2 boats by Phil Bolger (18' dolphin and 21' sharpie yawl-Otter II); nine Rob Roy canoes of my own design, three St. Pierre Dories, and one 21 ft. Sharpie yawl.

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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
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