The Steamboating Forum

Thanks Fred,

What if I go with 1/2 inch of Mineral Wool insulation between the boiler and the Lagging ? Would that be workable ? I have a roll of 1/4" on the way that I was thinking of doubling.

jon

P.S. - Are you going to Lee's Mills this year ?

I realize this is an old thread, but thought some might be interested in mahogany lagging. My slats are 1/2 inch thick by 1 inch wide and shaped to the boiler o.d. Made three 120-degree sections, each with the slats held together with hi temp epoxy. Three brass bands to hold the 3 sections to the boiler shell. Finished the wood with several coats of teak oil.

I've run the boiler for about four hours between 90 and 115 psi with no deleterious effects noted on the mahogany lagging whatsoever.

I was initially concerned because the char temperature of mahogany is close to the temp of the water inside the boiler, but so far, not a problem.

Rick

I agree with Fred on this one. I have a locomotive with about 1/4" spacing between the shell and the sheet metal lagging. I have tried various fiberglass layers, both compressed and not compressed at all. I cannot measure any difference on the outside of the lagging between the various insulating schemes and having just an air gap.

In your case, where you are trying to keep the lagging safer to touch, I would try to get some air circulating between the lagging and the shell. Some fairly big holes at the top and bottom perhaps. It helps with the metal guard behind my wood stove in the shop. Open at top and bottom.

My water tube launch boiler has 1 1/2" of fiberglass blanket under wood lagging and I love the gain in efficiency. It will hold pressure for ages with the draft closed and hardly any fire at all. I load onto the trailer with 120 lbs. showing and just a few coals. I drive the mile or so home, put everything away, have dinner and still have 50 lbs. on the gauge for a blow down.