Thoughts on this hull design - what seas and speeds etc.?

My quest for a fast stable boat to take recreational divers out has been on hold for a while due to life getting in the way, but I came across this vessel and would appreciate everyone's thoughts on what height seas etc it would be able to do various speeds at. From what I have gathered it is 15 metres / 50 feet long, I don't know the beam yet unfortunately, but it has diesel inboards powering propellers and does 25 knots at full speed. What are people's thoughts about how it would handle say 1 metre waves at what speed, 1.5 metres waves at ? speed, 2 metre waves etc? The waves in the Red Sea tend to fairly short interval - around 4s.



Any and all thoughts would be appreciated.

 

It is not easy to know how a boat sails just by looking at photographs. What I can tell you is that a boat for divers needs a platform that is as wide as possible, and close to the flotation, to transport the diving equipment and for the divers to attach the equipment and jump into the water, or get out of it. The ship's freeboard should be as small as possible, within the permitted limits. That doesn't seem to be a feature of this boat.

 

Sorry I should have added that if the design is suitable then will be adding a largish platform on the stern that raises up and down on rails - this boat is for technical diving which means the divers are carrying closed circuit rebreathers, several extra cylinders of breathing gases etc - they need the platform to get them out of the water.

 

It's a Grandsea AL-1500B, see the link for a little more information.

Grandsea 15m Aluminum Catamaran 50 Passenger Ferry Boat https://www.grandseaboat.com/products/passenger_ferries/15m_aluminum_catamaran_50_passenger_ferry_boat.html

They also sell them on Alibaba, for $325 000. I'm wondering if that is expensive for a diving company and how all the stuff will be financiated.

 

Many thanks for that information - that gives me a beam and freeboard by the look of it amongst other things. Do you know anything about that design?

 

I do not know more than stated on their website, sorry!

 

Cheers! Will have to contact them!
Looks like the props and rudders are fairly well tucked up out of the way which is always a damn good thing in the Red Sea!

 

Only basing this on years of experience testing fast catamarans and not any direct knowledge of this particular vessel, but....I wouldn't expect that hull would manage even 1-meter HS waves without difficulty. It appears to be suitable for calm-water taxi service.

 

Ah OK - we might skip that one then! If that's the case they might be having some really ugly times with it - I've just found out that it is in service as an inter-island ferry and sightseeing vessel in the Comoro Islands several hundred miles off the east coast of Africa - so pretty open ocean!

 

That was might thought as well, based on the information provided.
First impression - top-heavy.

 

Agreed.
Also its LD ratio is low, so would squat lots as she approaches hump speed, and in a heavy chop, would not be pleasant at all.

 

Apologies for the thread drift, but I found it 'interesting' how the Grandsea folk appear to have acquired this fishing cat design from MacDuff Shipyard in Scotland -
12.40m Aquaculture Catamaran - Lonabrak - Macduff Ship Design https://www.macduffshipdesign.com/ship-design/lonabrak/

Or maybe they have copied it - here is the Grandsea version :
18.5m Aluminum Catamaran Work And Utility Boat for Sale - Buy cat https://www.grandseaboat.com/products/work_boats/18_5m_aluminum_catamaran_work_and_utility_boat_for_sale.html

The Grandsea vessel is apparently 6 metres longer, but they post a photo of the 12.4 metre MacDuff vessel......

 

...and the cabin somehow fits a lot more seats into it!

I learnt recently that when you see CE in advertisements for Chinese things it doesn't mean that it has European approvals - cleverly they have decided that CE also stands for "China Export"

 

The problem with any vessel that is ever advertised is that they only ever show photos and videos of it on glassy smooth seas - never how it rides in anything else.

 

So it appears Grandsea isn't so grand at sea after all?