Long range project

@TANSL Thank you for the offer, and I have no issues problems with intellectual property. It is intended as a motorboat, and I'll post the file here. They are free for anyone to use as they wish.
Mr Efficiency and Ad Hoc thanks for the guidance. I was concerned about the way the PC came out so your tips will help with that.

 

I have been in a few displacement motor boats that size, one was fine bowed and tapering at the stern, rolled like all hell, another was similar length, but pretty full bow and broad transom stern, it was a league apart, albeit with more installed power.

 

Chris, you mention a budget of US$ 500,000 - I fear that this will be totally unrealistic, even if you are in charge of building it yourself.
I can easily see that sum being spent on materials, parts and equipment alone, with no allowance for labour - and you will have to employ a lot of labour to help you build a vessel this size if you want to do it in less than 20 years.

The Schooner Ruth was built on the beach here - she is of steel construction (rather than aluminium, which would have been a lot more expensive), 30 metres length overall, but a tad under 24 m. on the waterline.
She took her owner 15 years to build, employing labour at a fraction of the cost of welders, fitters and carpenters in Oklahoma.
She was launched 6 years ago, and her final cost was pushing US$ 2 million.
Schooner Ruth | Barbados' Sailing Ambassador http://www.schoonerruth.com/

Re the SOR of sorts mentioned by Chris - I think that Steve Dashew has already done all the hard work with his FPB 78 - the only difference is that she is of round bilge construction.
SetSail FPB » Blog Archive » FPB 78 The Dream Machine: Reality – Updated May 24, 2017 https://setsail.com/fpb-78-the-dream-machine-reality-updated-may-24-2017/

In my previous post above I was thinking that the very first FPB, Wind Horse, was / is 78', but of course she is bigger at 83'.
SetSail FPB » Wind Horse https://setsail.com/wind-horse/

 

I am curious how you settled on the size. Your SOR is easily achieveable in a smaller vessel, 50-60ft, and you have a higher chance of actually building it.

 

hard to disagree, given there will be a "skeleton" crew. I don't know about 4000 nm, but if you slow down, it helps ! And have a good handle on ocean currents and prevailing winds. Beamy, full ends, chop the size back.

 

Bruce Roberts, CATAMARAN boat plans, CATAMARAN boat building, boatbuilding, steel boat kits, boat kits https://www.bruceroberts.com/POWER_CATAMARAN_PLANS.htm

Perhaps a cat will give you more efficiency. Certainly twin engines but 2 smaller ones as compared to a larger single unit and you get redundancy. Long range travel to desolate places invites redundancy.
I expect that there are other suppliers of long range yacht plans where the engineering, stability, mechanical aspects are already completed. If you are building it yourself, you should purchase the current copy of
the ABYC standards as it is a bit of a roadmap on specifications for the fitting out of a boat. Also, if you want to get insurance on your boat, you may have to or should employ a certified marine surveyor as you
begin to build your boat so you will have a work in progress inspection so the surveyor will be able to give your insurance company a true survey to facilitate getting it insured.

It is hard to survey a boat that is complete as a lot of items are covered.

I believe there are quite a few aluminum cat plans suppliers in Australia though maybe Metal Boat Kits, and Specmar and there are others who can supply what you need.
Frequently, first time boat builders do not realize the time it takes to build such a project working on the "I can build it cheaper" path. If you are building in aluminum and buying as a retail customer and spending literally months cutting and fitting pieces and not being sure that you are doing things correctly, the cost of getting a DXF file from a reputable plan supplier and having the pieces cut will save you tens of thousands of dollars.
Most companies with the ability to cut the large sheets that you will need, will probably already be purchasing aluminum in large quantities, tons per year, so that they can supply you the aluminum cut for
a cost not far off you trying to do it all yourself. There is a thread somewhere on the forum, that shows the progress of two young people building a large boat in steel and their trials and tribulations along the way.

Before you begin, you owe it to yourself to take say the Bruce Roberts plan, the study plan, which I believe gives you the weights of the aluminum needed for the build. Take the list down to your local aluminum supplier,
and pick a big one, not Billy Bob's Aluminum Supply house, but one of the large industrial places and get a quote on the base aluminum.
Then head over to a large fabricator and there should be quite a few around your location on the Miss that can supply and cut the aluminum to size. I expect that the price difference will not be far apart from just
buying the material from an aluminum distributor uncut. It will be more BUT you will save thousands of hours of cutting the shapes that you will need. Don't worry, there will be thousands of hours left to
keep you busy with the rest of the systems.

 

I can definitely go with a shorter length. The length was set somewhat arbitrarily based on existing designs just so I could work out the hull form. If I reduce the length it would effectively add more beam and I can modify the ends.

 

As Barry says, being out on the raging main, with just the one main engine, does seem incompatible with prudence, I always think if you must have twin engines, then cats have automatically to be considered. The range could beat you, though.

 

Trawlercat Marine used to build displacement long range trawler catamarans in China, but they do not appear to be in business any longer.

Here is one of their trawler cats for sale - 67', but she has a range of 'only' 1,800 miles - and a price tag of US$ 995,000......
Trawler 67' Canadian Design Power Cat, 820.483 € | iNautia.com https://www.inautia.com/used-boat-72746070141698100100541015210052.html

 

I guess it depends how you calculate range, and whether is is feasible to use one engine to extend it. Probably not in some cases.

 

A delivery captain I knew, (since passed away,) made a name for himself by delivering power boats from SoCal to Hawaii, and sometimes on to Gaum.
He accomplished it by using fuel bladders, sometimes strapped down in the cabin, and in the case of "sport fishing" boats, by having bladders in the cockpit.
A couple of times he had a refueling vessel rendezvous with him in mid Pacific.
His experience with twin-screw boats was that better "mileage" was generally obtained by having both engines running slowly rather than one engine running faster.
I suppose that the drag of the shut-down engine required enough more fuel to the running engine that it offset any savings, and required more effort by the auto-pilot,, the constant drag by the necessary rudder offsets/trim would also add to the drag of the non-powered prop.

 

Yes, rudders would increase drag, but the dead engine's prop dragging as well. Interesting thought. I guess in a boat with retractable drives (not really applicable to this discussion) it is a different matter.