Well--admittedly, I'm a big fan of anaolgies. But trying to compare something that uses wheel on land with a very small grade (ie--little natural drag) and something that uses water for it's travelling medium (automatic drag) does strike me as the proverbial Apples & Oranges scenario.
I looked into this a little today and couldn't find any decent info. Maybe there's info for similar tonnage vessels that could be found on some commercial boat site. :hmm: