Is bigger better?

[SailorHarry]

Hello all,

So I'm finally ready to start building my steam boat. I will be ordering plans from Selway-Fisher for a boat in the 19-22' size range. I am about to order an engine and boiler from Tiny Tech India. He has continued to develop his engines over the last year or two. His engines now come in a wide range of sizes; all feature piston valves and Stephenson links. For some reason the lower ends seem to be metric now with an 80mm (3.15") stroke on the smaller engines. However, for the same price I can get it with a 3 1/2" cylinder rated 6hp or a 4" cylinder rated 8hp.

The boiler is a Yarrow type with 70 sq. ft. heating surface, I believe it will be sufficient for either engine. I was only planning to go with the 6hp engine but going bigger is tempting. It probably wouldn't push the boat any faster but it might do it at a lower RPM. On the other hand, it might have worse vibrations and might use more steam.

Any help would be appreciated. By the way I can post a current list of his products if anyone is interested.

Harry

[Mike Rometer]

Fear not Harry, help is on it's way, you've come to the right forum for that. Welcome.

[SL Ethel]

You will probably have the most fun and be most relaxed while steaming if your engine is just a bit bigger than you absolutely need, and your boiler is just a bit bigger than your engine needs. With this setup, you can be relatively relaxed and flexible about how you fire the boiler (if with solid fuel), and cruise at moderate engine revs.

For the size boat I think you are describing, 8 hp is likely very much overkill. I have a heavy, beamy 20' boat with a 3x4 engine. This would be plenty of power if my boiler could keep up easily (see above). A 3.5" bore engine would likely be plenty, especially if you have adequate boiler capacity. Obviously you will need more power if you have an extremely heavy or beamy hull, but all of the SF designs I've seen have nice lines. Anything shaped like a barge is likely to make a poor steamboat hull anyway.

Cheers,
Scott

[DetroiTug]

Starting a steamboat project and acquiring the necessary components; one thing to keep in mind. Don't be overly anxious. Start working on the hull, buddy up with steamfolk in your area (they can be found by subscribing to steamboating magazine and looking on the registry). Put the word out, attend local meets if there are any and the hardware will just start materializing. Lots of us have engines and boilers stuck back and will part with them sometimes when we hear of another boat going together. Read all you can and determine closely which engine and boiler you need. I use the term "closely" because typically what we wind up with is something other than we went shopping for, and it eventually works out in the long run.

Engines are probably the easiest to find as that is how most projects are started- generally by machinists. Sometimes the project never goes beyond that and the engines wind up being sold. And some people just like to build engines as a hobby. As Scott wrote, something in the 5 hp range is ample for your intended hull.

Boilers are quite rare to find and one should be wary of any used boiler. And even new boilers constructed beyond any local or standardized codes. One option on a boiler is make all the components and then have it assembled by a code shop. That saves a lot of money and the end result is a boiler you know will be safe. Some of the museums have code boiler shops and will often build boilers as well, at a much reduced price to help with their operational costs. One offered to build one for me about the time I found my boiler, can't remember which one exactly.

-Ron

[Johnlanark]

Hi Harry best wishes for your project. My tuppence (or two cents) worth is to say that there is a surprising difference between the volume/seating capacity/power requirments of some hulls with apparently similar specs. The 21ft Indian Runner is a lovely hull and and there are a number of very successful boats around. It is much bigger boat than my own 20 ft Cambrian-in-progress, that looks much the same in the catalogue. So perhaps you may choose the hull first and then the plant.
John

[farmerden]

As far as boilers go I think it all depends on the size of your Whistle!! This side of the pond tends to go for bigger whistles-Are we making up for some other inadequacy?

[SailorHarry]

Thanks all. The particular Selway-Fisher plan I'm looking at is the double-chine 22' Ruby as I want an aluminum hull. Yes, it's a little different and certainly not traditional but I'm not going for period-correct. The suggested engine for that hull is 6-8hp. I've about decided to go with the larger engine as there don't seem to be any downsides to it.

Harry