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Overview of the design
 
This page contains a general description of the design and construction of the new Steam Launch Artemis. Selecting a topic listed below will take you directly to that area on this page. In the future, and as more in-depth information is put together in a topic, selecting the "button" that is the topic name will take you to another page where additional details are available. When the lettering in a topic name button is no longer blue, that separate topic page is available.

| HULL | ENGINE | BOILER | OTHER |

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P R O L O G U E

Having been around hobby steamboating for over 30 years, ridden on many boats, and owned the previous Artemis, I've developed - with help from my partner - criteria for what we believe is the best hobby steamboat FOR US: small enough to be easily trailerable; big enough to allow comfortable day cruising for several people; have the capability to cook aboard and sleep two adults for "overnighting"; have a steam plant that is relatively self-regulating - requiring little attention while underway - yet somewhat different from most. With these parameters in mind, the following design has emerged.

HULL

Viking ship replica under a fair wind

The Viking ships of 800 to 1000 C.E. - as seen to the left - are some of the finest examples of the wooden shipwright's craft. Light, fast, maneuverable and shallow draft; desired attributes of the trailered hobby steamboat I envision. The hull lines are modelled from those of the Oseberg Ship - a karv or inshore yacht and dated to early 800 C.E. I've modified the hull form by "chopping off" 25% of the hull length from the stern, introducing a slightly raked transom, and flattening the bottom as it rises to the transom - the underside of which is barely submerged. These modifications were done with the help of a Naval Architect and, among other things, allow a free passage of water to the propeller while maintaining a very stable and shallow draught hull. The hull will be built of lapstrake plywood plank construction, following the guidelines of Iain Oughtred. The "bare" hull will measure 21' 6" LOA, 20' LWL, 6' 8" beam on deck, 5' 9" beam at the waterline, 12" draught amidships. The completed vessel, at the dock, will weight approximately 1500 pounds. For one person operation, direction and speed will be controlled by a "Kitchen Rudder" ( an explanation and design guidelines will be found on the "OTHER" page, accessible through the OTHER topic at the bottom of this page ). TOP

ENGINE

Model of the Ericcsson Vibrating Lever engine - photo courtesy of Rich Carlstedt

Having determined a hull, the next step - one would think - would be the engine. Well, no, not exactly. I wanted to achieve 6 knots sustained speed, hence the hull design selected. The propeller is the real next step. I took the model to a local firm that specializes in slow-turning "wheels". They recommended a 16" diameter by 24" pitch turning at 375 rpm and requiring 3 shaft horsepower. The present owner of the shop and his father ( who founded it in 1948 ) were both available so I had the benefit of over 80 years of expertise! Taking a diagram factor of 66% and mechanical efficiency of 92% I arrived at a figure of 5 design HP needed. Turning an engine at 375 rpm ( a "blur" rather like a sewing machine ) was not what I had in mind and my earlier selection simply didn't have the power. After considering many "somewhat different" designs I settled on the U.S. Navy standard for it's coastal monitor ironclads, an improved design by John Ericsson based on his prototype for the U.S.S. Monitor. Properly called a "half trunk, vibrating lever, back-acting" engine, it is comprised of two cylinders, double acting, with bores of 5", a stroke of 2.75" and at 85 psi ( and 20" Hg vacuum ) will develop 5 design HP at 125 rpm. A simple "step-up" drive from the crank shaft to the propeller shaft keeps the engine speed low enough that "onlookers" ( and myself ) can observe the motion the machinery. Much more detail on this little known ( but fairly common ) mid 19th century naval warship engine can be found on the ENGINE page. TOP

BOILER

The Winslow type boiler without casing and firebox

A watertube boiler was chosen as it keeps down weight and is more responsive to load changes. When we installed a "new" boiler in the previous Artemis a high efficiency boiler built to ASME code was modified ( a code shop did the work ) by removing several "sections". At that time I had the necessary fittings to connect the "extra" sections and, thinking that it would make a nice 25+ sq.ft. boiler for someone, someday, had a smaller boiler constructed. It will do very nicely for the new Artemis. Overall measurements to the outside of the casing will be 20" wide, 24" long, 36" high and the weigh approximately 300 lbs. The efficiency of this "Winslow" design is very good and, with the experience from the larger version, I should be able to incorporate controls that will make it more stable and self-regulating. The boiler is rated to 600 psi so a safety valve set at 100 psi will be well within design parameters. We plan to use wood and/or biodiesel as fuel. TOP

OTHER

There are many "accessories" that are needed to make a marine steam plant perform well and each hobby steamboat has her own variants which the owners prefer. Ones that I've designed and/or built are listed on this page. If a drawing is helpful I've provided them in a .gif format that can be downloaded or printed on a piece of 8" x 11" paper. TOP

 

Latest update, July 6, 2004

COMMENTS  
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