What differences do wider or narrower tunnels make?

More like the power requirements and the hull shape will be determined by the loads you wish to carry and the speeds you wish to achieve.

Loads and speeds are going to be determined by the economics of what you're doing and we expectations of your customers.

Also, again, skinny hulls are not better in everyway. The narrower the hulls, the more the boat will list and go out of trim as people and cargo move around.

 

First things first - you have to understand that doing business in Egypt is an incredibly slow thing - nothing in Egypt happens in a hurry - everything is an incredibly slow process, the rules keep changing - both the written and unwritten ones, and nothing is simple. The bureaucracy is beyond anything that you have ever seen - to give you an example, for a westerner who owns a car to transfer the registration to another person when they sell the car - expect it to take a month to work your way through the process and it will require visits to at least eight different government offices getting forms stamped, various fees paid etc etc - been there - done that.

Secondly - you have to understand that things we take for granted in the western world either don't exist or are located in places that simply don't work for what you need done. Boat lifts are an example - pretty common in the western world in places where there are a lot of boats - but not in Egypt - there is one boat lift on the entire Egyptian coast in the Red Sea - and it is in the least useful location. Container ports are another problem - there is one container port on the Egyptian coast in the Red Sea - the container boats that go there are ones that come from ports in East Africa or the Persian Gulf - the big container ships that come from Asia etc (where we are likely going to end up getting this boat built - possibly Vietnam) go into Port Said or Alexandria up on the Mediterranean - which then means that once it is put in the water then coming back down through the Suez Canal on a 400 nautical mile run to get to where the boat needs to be - transiting the canal is more complication.

And it just keeps going from there.

As for finding an aluminium boat design that already exists - I've looked but haven't found one that ticks all of the must have / must be able to do boxes. However I have one more thread to start on here in a few days once I have done a bit more reading myself and once I have the answers for that I will be able to write a SOR with some general drawings of what my thoughts are and then hand it to a naval architect and then things will start happening.

 

I will let the naval architect earn his money and work all that out, but a cat is the only realistic option to give us the deck space we need within the 12 metre length limit.

 

Its a bit of a go around in circles thing until all the numbers fall in the right places. Speed wanted has already been determined by the distance vs time wanted to get to the farthest dive site. Loads are limited to 12 people including crew by the one person per metre of length rule that operates there.

I hadn't thought about list caused by the divers all moving potentially to one side etc, however all diving is going to be done off the centre of the stern so that should help keep that under control... but then again keeping divers under control...

 

It is very common for all the passengers to go to one side to look at something unusual or exciting.

 

This sounds more along the lines of a small ferry or a people mover. Have you searched for existing designs in that vein?

(12 passengers / m) X (11 m loa) x ( 75 kg ) = ~10,000 kg

That's about 5x the load of the Skoota I referenced earlier which only has a useful load of 2000kg. And that's not including other stuff like dive gear, fuel, etc. Your hull widths are going to be pretty wide. As gonzo said earlier "Starting with an SOR, it may be that a catamaran is not the right type of boat."

 

@RSD look here, a lot of designs that could possibly be modified to meet your SOR

Albatross Marine Design Thailand - Boats & Catamarans https://amdesign.co.th/

 

RSD,

Thank you for your reply.

I do understand, I worked in Ethiopia and have been in Egypt.
It's not about that but rather endless inquiries about certain design features
that can be generalized but are primarily influenced by all the other design features,
how they interact and finally the overall effect and how it applies to your SOR.
That means multiple prototyping, redesigning, modifying, mistakes, delays...
Blah, blah, blah.

I thought you were going to go with modifying a manufacturer's proven catamaran product.
I trust they will do the modifications to your SOR.
Crazy expensive but so very much cheaper than the convoluted circus above.

Do you have a desired launch date?
Have you revealed the budget?

Inlist @bajansailor for your best catamaran choice advice.
He's made some suggestions on one of your other threads I believe.

 

This is simply not accurate. No Skoota design has available loading to DWL of 4400 pounds.

I am going to disagree with Bluebell some. I spent 3 years deciding what boat to build and it wasn’t enough.

Also, the stability of the catamaran cannot be beaten without a gyro.

 

The spec shows the loaded displacement to be 2100 kg more than the empty displacement. I'm taking that number at face value.

https://www.sailingcatamarans.com/freedownloads/Skoota36_initial_studyplan.pdf

Or a barge.

 

Don’t take it personal. The number is invalid.

Consider the outboard. If the PPI immersion is 1100 pounds per inch, the outboard would move up and down 4” under loading conditions.

The likely story is the loaded means empty bdeck with no fitout of anything. I have an acquaintance who built the Skoota 36 and he had to add sponsons and bow extensions to get the boat to float properly; so let’s just leave it there..

 

F%&king Dolphins!

 

I've had a look through the website of GMD tonight - they may have something that could be tweaked and finessed.

A cat is the only thing that I can think of that fits the 12 x 5.5 metre requirements - a monohull would be seriously butt ugly, maybe a trimaran might work...

 

Cheers! I will send them an email as their website has tons of designs but not a lot of info on the designs.