catamarn with stern drive engine

There is no way any boat 23 knots flat chat with 250 hp outboards would be a halfway sensible powering option, they are designed to cruise higher than that, not efficient at all on a boat restricted to the low 20's max, heavy, heavy, heavy.

 

Try chaining 3 bedrooms a kitchen 2 bathrooms and a lounge to the back of you car and see how fast you can go.

 

They skated along on the tunnel roof, maybe this Chinese boat needs similar help.

 

Chaser when are you going to post decent pictures of the front and the back OUT OF THE WATER

 

lol....I think it may be a secret.

 

Well I dont know about you guys but I would like to see a picture of the front and back out of the water.

 

Why do you need to see a pic out of the water?

The fundamentals have already been given;

1. Much too heavy for a ~9m waterline be an efficient displacement hull, the hulls would need to be very fat and deep to displace 12m^3 of water from ~9m waterline length.

2. Incorrect buttock lines aft to be an effective planning hull - shown in side profile pic earlier.

3. The pics showing the enormous wake and bow trim, tells us its trying to climb over its own massive bow wave.

4. At 12 tonne displacement and 38ft LOA, the HP and lift required to plane would be substantial, it needs more effective lift by changing hull shape/dimensions, or more effective thrust to get over the hump (more horsepower)

You dont need to see anymore pictures to explain what is already obvious...

 

Thanks for your reply. Very interesting. I think it should be a serious option in initial design for short planning cats (7-10 meters) where the hull beams are narrow (low length/beam ratio) and the planning surface is limited. Of course some extra power would be needed.

Regards
APP

 

Hi APP,
A bit of Australian history may be of interest, firstly on the Sharkcat. . . . http://www.modernboating.com.au/boat_tests/boat_tests/full/142/Shark-Cat-18,-20,--23 and in particular this quote - - "The Shark Cat name has gone but the spirit lives on as Hennig's company, Noosa Cat, builds cats with a huge variety of cabin/deck configurations at 11 basic lengths from 5- to 12-metres. The Noosa 7.8-metre, for example, has four deck options, and 10 have just been delivered to the NSW Police for the Olympics; five have cuddy cabs, five have small cabins. All have twin 200hp Yamahas and are good for 40 knots."

Not to forget the Australian Powercat range of boats http://www.powercatmarine.com.au/page/Boat_Range/ renown for their rough & choppy sea handling and high speed as used in rescue craft, water taxis, fishing boats and most other activities will find their niche... in the range - take note of the hp and weights... As a volunteer in the Australian Coastguard for a while I can vouch for their ability to handle rough and nasty sea conditions in SAR operations (at speed are very bumpy)...

see http://www.powercatmarine.com.au/page/Boat_Range/2900_PowerCat_Sports_Fisherman - - for the 29ft option, - and 76kmh is 41knots using 2 x 175hp Suzuki 4 stroke outboards...

 

FWIW thats a Raymarine 2kw radar (the 4kw are lower profile),18" array so about 21" dome...looking at the pixels,it does seem to be a 30' sponson line (including the swim platform) and about 36'-38' OA.

For the sake of spending some money on pro advice,he could have saved probably 100 times that and much aggravation by doing the right thing first.

 

The right thing, would have been to leave it as a monohull...

 

It did 23 kts with outboards on.

 

say's he who cant post pics of the underside showing the drives
say's he who designed this "miracle"
say's he who spent MONEY on "that"

it will be a real education to REALLY see what the "design parameters" are actually about

I also want to learn how on earth did they do it :idea:

 

mmmm probably on the money

 

I want to se a picture of the stern drive out of the water. It did 23 kts with outboards on so what has he done to spoil that.

Cummins said that he has the props too deep ??? I dont care if they were 6 feet below the water it would still produce the power and how could that be possible. The limitations of the engine touching the bottom of the boat normally stops most fittings from being deep enough.

A catastrophe!!!! ---or a wind up