HP requirements to get to 30 knots?I'm building a boat

[stormchaser]

Well, make that 3 boats...

So, my employer here in Belize has tasked me with PMing the build of our 53ft passenger ferries. The boats will weigh in around 20,000# when done and are power catamarans with a 2ft draft (before running gear) and 18' beam. He WANTS them to cruise in the upper 20s to lower 30s. Anyone know a good way to calculate the hp requirements to get there?

Thanks...

 

[Boatsb]

It will require the plans and more information. Check with the original designer.

 

[stormchaser]

No way to even get a decent estimate? the problem is, my employer bought the molds on eBay before he hired me (he knows NOTHING about boats), and the molds are virgin, never used, so there's no boats of this design out there to get info from. I was thinking twin 400hps would get it there, but just not sure? Sadly, the designer is not being very communicative...

 

[Sparky1]

Lots of variables in that one stormy, but you might start with horsepower to weight ratios compared to some larger power cats whose specs are available.

 

[nyrussell]

Stormy,

Find another naval architect then

 

[stormchaser]

Yeah, that's kinda the plan at this point.

 

[Boatsb]

Virgin Molds.............
No help from the architect........
No similar vessels to compare to........
No laminate schedule or structural requirement either I bet.

Looks like an accident waiting to happen if you don't get a good handle on the structural and power issues. 30 Kts puts a lot of stress on a boat. add passengers and you need to consider the risk of doing this one commando style.

 

[stormchaser]

Well, in THEORY, they are supplying a laminate schedule, but so far they have been less than responsive...but I totally agree...I am NOT at all comfortable with any of this right now...definitely need a good naval architect to work with us...

 

[spartonboat1]

I you are considering cold-molded wood (very strong, Rybovich are several layers wood/glass I believe), contact VanDam Marine in Charlevoix, MI, or Amaya (sp?) Boat works, Detroit (Harrison Township), MI. Amaya may be in Sterling Hgts. Both firms build quality wooden boats entirely new and may be able to provide advice.

 

[stormchaser]

Plywood is VERY expensive here. I can get solid mahogany for FAR less than marine grade ply or balsa. Any IMPORTED wood has a 100% duty! So, they will be foam cored or solid...

 

[fissioneng]

There is a cat builder at my marina. Here is one of his for sale. 54', cold molded, twin 370 HP 6B Cummins, 18 knots, 46K lbs. At least it's a data point.

20K lbs for a 53' boat sounds really light. Where did that number come from?

http://www.yachtworld.com/core/list...nits=Feet&access=Public&listing_id=76454&url=

Here is a link to the architect:

http://www.searunner.com/about.html

 

[stormchaser]

That number came from my boss, who (honestly) is known for just making numbers up when he doesn't know for sure. So, it IS suspect until I get a hold of the original designer. But, the boats we will be making is MUCH more basic and lighter than the one you mentioned. Its the 53ft version of this:

http://www.yachtworld.com/boats/200...-Deck-1661989/ST.-Pete-Beach/FL/United-States

 

[krush]

Get with a real naval architect (as already stated)