What boiler to use

[Maltelec]

I have received this question from a fellow enthusiast and have relayed it to here in the hope some of you can answer:

I have been a member for a couple of years and am working on 25 foot steel tug. I have 5 by 5 single acting with stevensons link. have many questions,and trying to decide on boiler type and size to build.

[fredrosse]

The most simple boiler, a Vertical Firetube (VFT) type. About 24 inch diameter x 24 inch tube length, with a wet furnace about 15 inches high. If an ASME Code boiler is to be built, this is simple enough to not cost a small fortune.

Second option, a Gunboat style firetube boiler, lower center of gravity in the boat, very similar to the VFT, and still relatively easy to build. A Gunboat Boiler has the advantages of a Wetback Scotch Marine Boiler, but with much less complication.

Third option, a Roberts type watertube boiler, very popular with the steam launch crowd, but hard to build to Code requirements. Good steaming, lighter weight, but requires more control of the fire to match the engine's requirements.

The firetube types are much easier to control, and for a relatively heavy boat, such as a tug, I would recommend the firetube types. Although ASME Code construction is usually not required for a small launch, it is a good idea to comply with the Code, there are reasons why it is so prevalent in industry. Laws may change, and ASME Code compliance may be forced upon steamboaters some day.