MARINTEK VERES: catamaran seakeeping calculations

Discussion in 'Hydrodynamics and Aerodynamics' started by sottorf, Aug 18, 2012.

  1. BMcF
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    BMcF Senior Member

    The difference in lightship and deadship weight between a 40m 40-kt cat and a 40m 40-kt SES is simply the extra pair of propulsion systems in the cat, less the weight of lift engines, fans and seals. Typically..the SES would have a pair of MTU4000 engines with KaMeWA jets and two 2000s of about 400 kw each for lift. The cat wuld have 4 MTU400s and 4 jets.

    Not a huge difference at all. But back to the point: the 40m SES is carrying the same number of passengers as the 40m cat, but burning 35% less fuel to do it.
     
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  2. Ad Hoc
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    Ad Hoc Naval Architect

    That's my point. It is much more than that. That is the standard answer/reply given in those "efficiency factor" papers.

    Hence what is the lightship. Need to compare like with like for a proper comparison.
     
  3. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Was this a variation of the T-craft project?
     
  4. BMcF
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    BMcF Senior Member

    No..completely unrelated high-speed sealift development effort that ONR abbreviated as "HSSL". Some of the same companies were involved as were in T-craft though; we supported the Alion/JJMA team on the HSSL project, as did Lawry Doctors. We were on two other teams for T-Craft.

    Of the various designs that came out of the HSSL program, ours was the only SES; about 1100' LOA with a beam of 105'. T-Craft, on the other hand, required an SES solution to meet other requirements in the matrix..
     
  5. BMcF
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    BMcF Senior Member

    So carrying the same passenger load with the same LOA vessel using 35% less fuel to do it is of no interest to the potential buyer/operator of same? What else is that operator interested in ..efficiency-wise?
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    The weight of the structure that is supporting those fans/lift engines/seals etc...the weight of the electrical cabling of the aforementioned. The weight of the piping for the aforementioned, the increase in genny size to run the aforementioned, the fuel increase to supply the additional hardware of the aforementioned, the extra space requirement to house the aforementioned, the insulation to dampen the screaming noise of the aforementioned to the pax in the saloon adjacent to the housing, the change in layout to ensure the same number of pax, which adds more weight, of the aforementioned. And so on..

    All this is up front capital cost coupled with higher maintenance.

    The cost of a typical 40m cat v a typical 40m SES which is higher??...the SES by approximately 80%...not a small sum of money. So the more energy efficient SES takes significantly longer to pay for itself; whilst being maintained at a higher cost.

    That's why!

    Still interested in a skirt??:D :eek:
     
  7. BMcF
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    BMcF Senior Member

    ?? The 'best' ones I helped build (20 or so) were between 0% and 20% higher initial purchase cost than the equivalent speed and payload cats I helped build (30 or so).

    Not sure where you get your data. I'll admit that I've only been involved in building maybe 30 SES and only 40 or so similarly sized passenger cats..so maybe my my experience is/was a bit limited.
     
  8. Ad Hoc
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    Ad Hoc Naval Architect

    Old data I had from the 90s...which is a bit vague at best too :D:D

    However, i fail to see how (other than under quoting as some yards do to get an order :eek: ), some could quote 0% or even just 10% higher than an equivalent cat, given all the extra dangly bits hanging off your skirt. M/c'ry costs account for roughly ~60% of the vessel. Doesn't come for free :p

    I think I'll file this one away in the same draw as the submerged bodies of revolution arguments I always have too :p
     
  9. BMcF
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    BMcF Senior Member

    I suppose it 'tis an argument over moot points...since both the quad-engined over-powered fast cat and the SES have gone the way of the dinosaur. Can't recall the last time the phone rang with someone on the other end wanting to haul passengers at 50 knots. *sigh*
     

  10. Ad Hoc
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    Ad Hoc Naval Architect

    Indeed...it's all gone quite :(
     
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