How to build boat to carry a single shipping container?

I live up the coast from a port where I need to transport shipping containers 40ft/8ft to and from.

1.) need cost estimate for doing this on the cheaper end of things (not cheap as in junk) that is still durable and made well enough to last 30+ years.

2.) There is a 40 ft barge for $30,000 here: Truckable Barge 196 http://barges.leefelterman.com/index.php/43-truckable-barge-196.html

Could I save money buying a fiberglass boat?

 

I think the weight required to be carried, needs to be specified, as does the centre of gravity of the load, if a heavy one, whether traversing sheltered water or not, etc etc. So many variables, including the method of loading and unloading.

 

Weight = 27,600 kg. the center of gravity may vary some. It would be on the open ocean. Method of loading and unloading is crane.

Would there be any differences if it were for a sheltered waterway?

 

There was a thread here a few years ago about the same subject. This was the current state of affairs at the time.
Any alternative for this kind of 20'container transport? https://www.boatdesign.net/threads/any-alternative-for-this-kind-of-20container-transport.41709/

 

A sheltered waterway will not require the stability of open ocean use. Unless you are loading the containers yourself, and able to control the center of gravity when loaded, you should consider the worst case scenario where the CG is near the top.

 

Sounds like you need a 50' barge, with plenty of beam, just in case the COG is higher than desirable. That is a lot of weight to deal with, above waterline. I suppose considering the container is lifted and dropped in by crane, you could have it in a well, down below waterline, that would simplify the stability issues, but then keeping water out of the boat becomes a problem.