Power cat unlikely performance?

[DogCavalry]

Oops. Thread misdirection. Sorry about that.

 

[Mr Efficiency]

Yep, you have the sea sled mania. The appeal of being able to run economically beyond "hull speed" that is found in some cats, seems not so evident with the boat that is the subject here, largely because it isn't a light boat, and the slimness ratio of the hulls isn't allowing it.

 

[DogCavalry]

Yeah. That big, chubby and heavy, cats don't have much to offer.

 

[fallguy]

Yep, you have the sea sled mania. The appeal of being able to run economically beyond "hull speed" that is found in some cats, seems not so evident with the boat that is the subject here, largely because it isn't a light boat, and the slimness ratio of the hulls isn't allowing it.

cruising along that slow is the real question; if the OP can take it or will always be trying to run at half throttle and double the burn rate

personally; it would be hard for me and I'd rather have a sail up at that point

 

[DogCavalry]

Indeed. That's painfully slow for such an investment in boat,engine, and fuel.

 

[Mr Efficiency]

Not much use having a cat, if 8 knots is your cruise speed, you really want to have the advantage that both displacement and planing hulls do not have, of being able to cruise in the mid-teens.

 

[DogCavalry]

Bottom line Bostjak: don't buy that boat.

 

[DogCavalry]

cruising along that slow is the real question; if the OP can take it or will always be trying to run at half throttle and double the burn rate

personally; it would be hard for me and I'd rather have a sail up at that point

Yes, if 8 knots is adequate, a 53' junk will give you that.

 

[fallguy]

pretty obvious which boat this is and personally I find it to be seriously range limited for what a boat its class ought to be able to do

take the 20meter Domino powercat; it cruises at 10, has a top end of 22 and can easily got to Hawaii so double the range, and is listed at 500k used

2009 Malcolm Tennant Domino 20 Power Catamaran for sale - YachtWorld https://www.yachtworld.com/boats/2009/malcolm-tennant-domino-20-3495698/

if on the other hand you want to take out a group of couples for charter, then you have no plans to sail the world and the boat might be right if you avoid the throttle unless absolutely needed

 

[Bostjak]

Hey guys, thanks for the welcome. Yeah I think this whole boat is a bit of a mess. The miles you can travel per litre of fuel is just ridiculously low after 8 knots. I just couldn't understand how
it was as bad at 12 as at 24. I think these engines are even used in the Landcruiser car if I'm not mistaken. What sea sled are we talking about here?

 

[Bostjak]

Bottom line Bostjak: don't buy that boat.

How do I like this post?

 

[jehardiman]

You know, from a naval architecture perspective about the performance of power cats transitioning from displacement to planning, it looks like the NA got it right. For some background, go see this old post: Expensive Hull Speed.
You can actually see the first and second wave making humps in the fuel consumption, and just at the right Fn's for a ~53' LwL hull.

I think the issue here is we don't know what was the sponsor's SOR was. If they were: It has to be a cat under 55' to fit a given slip/marina (Whickham Cay), it has to have better accommodations than a Class A motorhome, it has to do 20+ knots so anywhere in the BVIs is an hour or two, it has to have a 1000 nm range and get to Miami in less than a working week (5 days so it can be on charter both weekends)....they didn't do that bad.

 

[fallguy]

You know, from a naval architecture perspective about the performance of power cats transitioning from displacement to planning, it looks like the NA got it right. For some background, go see this old post: Expensive Hull Speed.
You can actually see the first and second wave making humps in the fuel consumption, and just at the right Fn's for a ~53' LwL hull.

I think the issue here is we don't know what was the sponsor's SOR was. If they were: It has to be a cat under 55' to fit a given slip/marina (Whickham Cay), it has to have better accommodations than a Class A motorhome, it has to do 20+ knots so anywhere in the BVIs is an hour or two, it has to have a 1000 nm range and get to Miami in less than a working week (5 days so it can be on charter both weekends)....they didn't do that bad.

This is fair. It is important to understand the users wishes for the boat. It is easy to assume on the pricetag of the 53 that the user might want to go further. Might not be true.

 

[DogCavalry]

Hey guys, thanks for the welcome. What sea sled are we talking about here?

Well. Let me tell you. Actually, the best place to start is to take a look at NA Dave Gerr's website. He has a section devoted to articles and publications. In there he has 2 excellent articles on Sea Sleds. I'm off to work now, but I provide links later, if these instructions are too vague. Or email you the pdf's this weekend if you PM me.

I'm building one now.

 

[Yellowjacket]

Google Hydrofoil Supported Catamaran. If you want to go faster more efficiently that's probably the best way to go.