At 05:09 PM 1/18/98 -0500, Georgs Kolesnikovs wrote: >Paul-- > >Why did you not follow my suggestion to simplify matters for all >concerned? Why attach something that can only be read with difficulty by >a few? [snip] I screwed up, and I apologize. Hopefully better late than never, I will follow your original suggestion: TITLE: Design and Construction of my 60 Powered Catamaran AUTHOR: plkruse@iu.net (Paul Kruse) DATE: 12/31/97 ABSTRACT: My 16 year old son and I are in the process of building a 60 foot powered catamaran of our own design, to be outfitted for commercial fishing. We are about two years into a ten year building project. Our plans are to fish the boat together during the season, and to cruise out of the season; so the boat has been designed with both purposes in mind. While it is a displacement power boat, it has also been designed to make it easy to add a proper mast and sail latter on. The purpose of this essay is to outline the design and construction of this boat. I must apologize that I do not have any electronic pictures of the construction project that could be published on the Web. HULL FORM: Imagine a 24 foot compounded plywood catamaran hull which has been cut in the middle and stretched to 60 feet. Compounded plywood is sometimes also called "Tortured Plywood." It actually results in three dimensional compounded curves in a sheet of plywood. While I am not using this method to build this boat, it is a good devise to understand the shape of my boat. The compound curves are therefore in the forward and the aft 12 feet of the boat, with a continuous cross section in between. This construction method has the advantage of all the ribs being identical, which saves a great deal of construction time, since all the ribs can be made on the same jig. The hulls are very thin, with an aspect ratio on the waterline of about 12:1. I am currently building sub-assemblies in my yard, where space is very limited. I have therefore designed the hulls so that I can build them in 12 foot sections and transport them to a boat yard for final assembly. Each hull will have four twelve foot sections, with a four foot splice in between each section. Having a background in aircraft design, I have borrowed and modified construction methods from that industry to make the hull sections easy to splice together. The purpose of working like this is to put off having to pay yard space rental as long as possible; and also because working at home is always easier than working in a boat yard. With a hull depth of 14 feet and a super structure on top of that, and with a beam of 26 feet, I really cannot transport the entire fully assembled boat over the road -- so final assembly must be done at the boat yard. DECK LAYOUT: All the volume inside of the hulls is either fuel space, freezer space, or equipment space. All the living area is in the supper structure on top of the hulls. I will have two small bunk houses on either side of a 15 foot wide isle way down the center of the boat. The bunk houses will be bridged with sun roof, which will extend fore and aft over most of the boat. This layout will enable me to hoist in a long line over the bow, and simultaneously re-deploy it over the stern -- thereby eliminating the need to reel it onto a large spool, which is the normal practice. The helm is just forward of the bunk houses and aft of the forward shear wall, which is sort of a structural bulkhead. STRUCTURE: I really do not have to worry about the structure of the hulls themselves. They are deep enough to prevent hogging. The splices between the hull sections are as strong as the rest of the hull. The major structural concern are torsional loads between the hulls, as wave motion raises one hull and lowers the other. These loads are tremendous in a boat this size, and could easily tear the boat apart if not properly accounted for in the design phase. I have employed two different methods of taking out these torsional loads. One is a simple series of nine wooden I-beams that hold the two hulls together. These I-beams also define the thickness of the bridge deck between the two hulls at 24 inches. That space is used primarily for cabling runs, tankage, and for a small hot tub. The other structural devise that I am using to take out the torsional loads is a structural box in the supper structure. The sun roof, the two bunk houses, and the two shear wall form the basis of this box. One shear wall is four feet forward of the bunk houses, and one is flush with the aft wall of the bunk houses. Both walls have doorways in them, so that I can run the long line as previously described. DISPLACEMENT RANGE: My displacement range will vary between 30 tons for a basic and empty boat, to 110 tons when loaded to capacity with fuel, bait, fish, and supplies. This very large displacement range makes it very difficult to use a standard marine propulsion system, which has a single forward gear ratio and a fixed pitch propeller. Such a system works well only when operating conditions are always close to the same, with a very small displacement range. In my case, I need the equivalent of a variable speed transmission, or controllable pitch propeller. (I'll handle this in more detail later.) The only way to handle such a large displacement range with a catamaran is to also allow for a fairly deep draft, since a catamaran has such a small water plan area. At maximum displacement, I will draw about eight feet of water. This is with the two propellers located between the hulls, so that they do not require extra draft below the keel. The keel of this boat is therefore the lowest point. At minimum displacement, I will draw about four feet. POWER SYSTEM: Everything that needs to be turned by power on this boat, including the propellers and a whole bunch of other things related to the fishing business, will be turned by hydraulic motors. The only thing that each of the three air cooled Deutz diesel engines will turn will therefore be hydraulic pumps. Any one or any combination of these three engines can therefore run everything. When power requirements are low, one or two of the engines can be shut down to conserve on fuel. Two engines can fail completely, and the boat can still return to port under its own power. Since the engines will be turning variable displacement pumps, I will therefore have the equivalent of a variable speed transmission. Gear ratios are infinitely variable from full speed reverse to full speed forward. This is the reason for turning the propellers with fluid power. Since the engines are air cooled, they will not require any raw water for cooling -- not even indirectly through a heat exchanger. The exhaust will be dry stacked through a muffler. I will therefore be able to use a standard diesel engine with no marine conversions. This keeps costs down to a minimum, both the cost to buy the engines in the first place, and also the cost to maintain them over the years. The way engines are normally mounted into boats, air cooling simply does not work. I have therefore designed a new way of mounting the engines, in order to achieve the required air flow for cooling. Fortunately, the fluid power transmission system allows me to mount the engines any place I like. They will therefore be housed in a cabinet above deck, for good air flow; and they will be forward of the pilot house to get them out of the way of my fishing equipment. With the fishing equipment aft, I really needed to weight forward, anyway. Since Deutz diesels are just about the quietest engines on the market, it will be fairly easy to design the cabinets to attenuate the noise down to an acceptable level. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ :: Paul and Cindy Kruse :: KJV Joh 14:27 Peace I leave with you, 165 South Kenneth Court :: my peace I give unto you: Merritt Island, FL 32952 :: not as the world giveth, give I unto you. E-mail: plkruse@iu.net :: Let not your heart be troubled, 407-453-6206 :: neither let it be afraid. :: +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++