conversations.from: human
conversations.value: a description for a book titled Marine Diesel Engines about Marine, Engineering, Engineers with the genre: Engineering & Transportation, Transportation
conversations.from: assistant
conversations.value: the author, a full professor of Marine Engineering, has taught at the United States Merchant Marine Academy for three decades, receiving the Alice B. McNulty Award for Excellence in Distinguished Teaching. the author is a registered Professional Engineer in New York. He holds a Bachelor of Marine Engineering with Honors from New York Maritime College, and an Ocean Engineers degree from the Massachusetts Institute of Technology and the Woods Hold Oceanography Institution. The author has earned a First Assistant Engineers License, Unlimited Horsepower Steam and Diesel from the United States Coast Guard. He has coauthored several papers on diesel engine combustion and presented a paper on Diesel Engine Room Simulation in Nantes, France. the author is a member of the American Society of Engineering Educators (ASEE) and the Society of Naval Architects and Marine Engineers (SNAME).
conversations.from: human
conversations.value: the first five paragraphs for this book. Start with the sentence 'Marine Diesel Engines
  Only in exceptional circumstances will you find that a displacement hull requires more than 1 hp per 500 pounds (fully loaded) displacement (see Figure 9-3)'.
conversations.from: assistant
conversations.value: Marine Diesel Engines
  Only in exceptional circumstances will you find that a displacement hull requires more than 1 hp per 500 pounds (fully loaded) displacement (see Figure 9-3). For many years, we had a 30 hp engine in a 30,000-pound boat (i.e., 1 hp per 1,000 pounds) and always found it adequate, but then we had an efficient variable-pitch propeller. We were operating at the lower end of the power requirements for our boat.
  The square root of the wavelength (in feet) ×1.34 = the wave speed (where wavelength is in feet, and speed is in knots).
  This is a fact of nature that simply has to be taken into account when designing boats. Figure 9-4 shows how dramatically wavelengths increase with small increases in speed—the doubling of a wave's speed from 5 to 10 knots increases its wavelength fourfold (from 13.9 to 55.6 feet).
  The bow wave of a boat is moving with the boat. Because of the physical relationship between wave speed and wavelength, the faster a boat moves, the faster the bow wave moves, and consequently, the farther apart it is from its second crest. At some point, this distance—the wavelength—will be such that there will be a crest at the bow and another at the stern. If a boat goes faster, the wave crest at the stern moves farther aft, dropping the boat's stern into the bow wave's trough so that the boat is now attempting to "climb" its bow wave. Heavy-displacement boats, which generate large bow waves, need more power than can normally be generated by sails or an engine to do this, and as a result many sailboats do not go this fast.
  Lighter-displacement boats make smaller waves. This results in a greater potential to get somewhat ahead of the stern wave, and as such hull speed may go as high as 1.7 ×the square root of the waterline length (in exceptional cases, it may reach 2.0 ×the square root of waterline length).
conversations.from: human
conversations.value: five more paragraphs
conversations.from: assistant
conversations.value: If a seal fails, at the very least the propeller shaft coupling must come off in order to replace it. On some boats, the propeller also has to come off to create sufficient longitudinal shaft movement to get off the coupling, and occasionally the engine has to be moved off its mounts. In the meantime, if the boat is in the water, the flow rate from the failed seal into the boat is determined by the clearance between the shaft log and the propeller shaft. On those boats in which a rubber sleeve bearing is inserted in the shaft log (mostly boats with a propeller in an aperture in the rudder), the flow rate is almost always relatively low, such that a bilge pump can keep up with it. But on those boats in which the rubber sleeve bearing is installed in a separate strut (the majority of modern boats), the flow rate may be quite high (see below for more on rubber sleeve bearings). In the latter case, it is worth ensuring that the shaft log makes a close-enough fit around the propeller shaft to keep the maximum flow rate down to a level that the bilge pump can handle.
  I once found the bilge pump on my last boat constantly kicking on. An investigation revealed that the sealing ring on my shaft seal had worked loose, and the two halves of the seal had separated. Water had been flowing into the boat since the last time I used it, two weeks previously! The boat had not sunk because the shaft log on our boat was a moderately close fit around the shaft, which kept the flow rate relatively low, and we had a large battery bank, which was able to support the bilge pump for two weeks. Further investigation revealed that the locking screws had been left out of the sealing ring when it was installed. After locking the ring, I added a propeller shaft zinc behind it as a backup.
  It is this nagging fear of a major leak as much as any other factor that causes many boatowners to remain wary of mechanical seals. The various lip-type seals on the market attempt to address these concerns by seeking to eliminate the leaks of a stuffing box without in any way increasing the risk of a catastrophic failure. This is done, essentially, by replacing the packing in a conventional stuffing box with a nitrile lip seal of the type universally used to seal crankshafts and output shafts in engines and transmissions.
  The simplest units are water lubricated and closely resemble a flexible stuffing box. One end of the seal body is fastened to the shaft log with a length of hose; the other end has a recess into which the seal is slipped. In order to keep the seal lubricated, provision is made to maintain a water supply from the engine's raw-water circuit. Experience has shown that unless corrected for, shaft vibration will cause such a seal to leak, so a rubber sleeve-type bearing is built into the inside of the seal body, forming a close fit around the propeller shaft. This keeps the seal in a constant alignment with the shaft, regardless of engine misalignment and other problems (see Figure 9-33).
  Other seals are oil lubricated. These are physically similar in appearance, but instead of a single seal at the inboard end, they have seals at both ends of a tube (see Figure 9-34). Lubrication is provided by a gravity-feed tank of oil set above the seal. There seems little doubt that the oil-lubricated seals last longer than the water lubricated, but on the other hand, the oil reservoir must be checked regularly, and if it is allowed to run dry, the seal will heat up and fail. Unlike the water-lubricated seals, these shaft seals require a minimal level of operator attention and maintenance.
conversations.from: human
conversations.value: the last three paragraphs
conversations.from: assistant
conversations.value: An impact wrench is a handy tool to have around. These take a variety of end fittings (e.g., screwdriver bits and sockets) to match different fasteners. Hit the wrench hard with a hammer and hopefully it will jar the fastener loose. If an impact wrench is not available or does not work, apply other forms of shock but with an acute sense of the breaking point of the fastener and adjacent engine castings, etc. Unfortunately this is generally only acquired after a lifetime of breaking things! Depending on the problem, shock treatment may take different forms:
  Heat expands metal, but for this treatment to be effective, frozen fasteners must frequently be raised to cherry-red temperatures (see Figures E-1 and E-2), which will upset tempering in hardened steel. Uneven heating of surrounding castings may cause them to crack. Heat must be applied carefully.
  Heat applied to a frozen nut will expand it outward, and it can then be broken loose. But equally, heat applied to the bolt will expand it within the nut, generating all kinds of pressure that helps break the grip of rust, etc. When the fixture cools, it will frequently come apart quite easily.