New steamboat mess.

[johnp]

Well, i started my first steamboat project, never seeing or being in one, only experienced on the internet. My 80 year old uncle started talking about how neat it would be having a steamboat, i was intrigued so i decided to start building one to have ready for next summer when he comes up from Pensylvania to Muskoka for our annual family reunion.

First i purchased drawings for a Ray hasbrouck #10. Rated at 2 hp but if you apply the PLAN method of calculating, it works out to 3 hp, i found a 21' fiberglass lifeboat hull for resonable money and purchased it. I've come to realize that maybe the boat is a little big for my engine. Our cottage is on a small lake the water is never really rough, i don't need to go fast, or pull around other boats it's just about crusing around the lake (with my uncle next summer) making his day. Will it be able to do this? will the wind blow me backwards when i'm trying to go forwards? i guess i'm looking for some assurance, confidence, that this will workout.(until i get time to build a bigger engine and boiler).

John

[fredrosse]

The engine is a little smaller than is typical for that size boat, but you will be able to do fine with your hull & No 10 engine. Cruising around at 4-5 MPH should be easily achievable. The sidewheeler Margaret S has less than one engine horsepower, weighs about 1800 pounds with passengers, and has the disadvantage of non-articulated paddle wheels, which are less efficient than a propeller. Although not fast, the sidewheeler keeps up with the other steamboats when we are not racing, and provides pleasurable cruising. The paddle boxes are like large "windcatchers", and steaming against the wind slows the boat somewhat, but I have had no problems with being blown off course.

Get a boiler that has about 15-20 square feet heat transfer surface area, and the right propeller (I would think 16x16 or 17x16), you will get your desired results.

[johnp]

Hi Fredrosse

i found a 17x17 rh, what do you think?

John

[PeteThePen1]

Dear John and Steamy Friends

On the issue of windage, how about this heresy?

As it is fibreglass, you could attack the hull with an angle grinder and take the gunwale line down by (say) 6" or pssibly more if this boat is only for use on small lakes. While you were at it you could readjust the sheer line to whatever shape you happen to like ina steam boat. Do it on the drawing board first though! She will remain beamy, but then that is no serious disadvantage as she will be pretty stable.

What do you think?

Regards

Pete

[Mike Cole]

Dear John and Steamy Friends

On the issue of windage, how about this heresy?
If you are thinking of doing this, the be very careful as a lot of the strength of the hull is in the gunwale, and where the stem post and any other transverse members meet it.It would be a hell of a lot of work.but not inpossable

Mike

As it is fibreglass, you could attack the hull with an angle grinder and take the gunwale line down by (say) 6" or pssibly more if this boat is only for use on small lakes. While you were at it you could readjust the sheer line to whatever shape you happen to like ina steam boat. Do it on the drawing board first though! She will remain beamy, but then that is no serious disadvantage as she will be pretty stable.

What do you think?

Regards

Pete

[johnp]

Thanks for the replies everyone, being my first steamboat and never being in one or seeing one, I don't think I have the abilities to modify the boat to that degree. I'll try to put the stern tube in and finish the interior with wood and build a half canopy. If all goes well and she sails around the lake next summer then maybe I'll build or buy a boat from Pat Spurlock and build another engine and boiler 5-8hp. Keep the input coming I appreciate all the ideas and lessons.

John

[DetroiTug]

What I was told early on, the power of a steamplant is really dictated by the output of the boiler. From there on out, one can turn a small bore/stroke engine fast or a large bore/stroke engine slow. The size and pitch of the prop determine the shaft speed.

My buddy's steam motorcycle demonstrates this principle. He's using a "Strelinger" engine, small bore and stroke with a flash boiler. He runs at over 2000 RPM and speeds over 30 mph. It really boils down to how much steam can be generated.

So I would look for a boiler sized accordingly to the hull and spin the engine at higher RPM with a lower pitched prop.

-Ron

[johnp]

I don't want to run at too high of an rpm, it takes away from the beauty of mechanics. Math says its 3hp (I would think ihp) but it's rated at 2 hp (I would think shp/bhp). I think most engine advertised hp is ihp. I see a lot of boats being powered by surprisingly low advertised power, and some with surprisingly large pitch props.I have 2 boilers, one 20sqft and one 35 sqft the 20 sqft can run 100psi comfortably and the 35 sqft can run 150 psi. The engine is designed for 125psi and 400 rpm. Which boiler should I use?

[Youtube]http://m.youtube.com/index?client=mv-go ... 5hUEDZF2vg[/Youtube]

[Lopez Mike]

My apologies to those of you to whom this is VERY old news. I wish I knew how to put together a few graphs and post them on here. It would help. These questions come up so often. I'll think about doing this.

The formula for power shows that it is zero at zero RPM and rises linearly with speed with certain limitations. The number that I find interesting is BMEP (Brake Mean Effective Pressure). It is calculated from the power we get on a Prony Brake and gives a number that is what you would get if there was a constant crankshaft torque throughout the power stroke. (There are geometric complication that get in between piston pressure and torque. Not now, grasshopper.) On my single engine, this number is highest at mid stroke and stall where flow and frictional losses are zero.

IMEP (Indicated Mean Effective Pressure) is the area under the curve of pressure v.s. piston travel. It is the power produced at the piston rod. IMEP was the only way to measure output on big engines in the past as no one had a big enough brake (dynamometer) and the engineer/mechanic could hook up his indicator and mess with things in the field (ocean?). I have an indicator. Cute but I haven't had occasion to use in a coon's age. I don't have a planimeter anymore to measure the area within the graph!

One practical r.p.m. limitation is vibration and/or parts starting to fly about the boat. I don't have any enlightenment on this. It is, of course, aesthetic as well. Few people wish to share a space with some buzzing demon.

The big limitation of this linear rise of power with rpm is a falling off of torque. There are several reasons for this including friction. The steam passages, both within the engine and external to it are limited. My little single (3 x 4) at 500 rpm and 5 h.p. calculates to 70 p.s.i. BMEP. If I thought it was important, I could enlarge those passages and get more torque and thus power. I might possibly spin this poor thing at 1000 r.p.m. for a short while and get more power but I suspect that the BMEP would drop to 40 or so and the both life of the engine and the life of my interest in the experiment would be short.

This is all why there is no easy answer to the often heard question, "How do I decide what r.p.m. is right for my engine?" Most owners start high and slow down with experience. A manufacturer is under conflicting pressures. A high advertised power rating sells well but no one in their right mind runs their engine that fast for very long. Common automobile engines produce their maximum numbers at speeds seldom seen in use. So, also, our steam engines.

In locomotives (steam, of course!) very few manufacturers provided enough boiler capacity and steam passage area to have high torque at high speeds. The last of the Lima super power units used by the Union Pacific were exceptional in this regard. The surviving examples can produce nearly as much torque at highway speeds as they can at stall. Speed was more important to them than economy or raw pulling power. Things are far apart in the Western U.S.

I have all of my useful formulae on a spread sheet. I find it entertaining, if not always useful. In practice, staying fairly near to traditional designs keeps me from error and ridicule. Well, error anyway.

Mike