Ocean going barge to tow

Hi all,
I require a barge that can be towed from the South coast of the UK to Bordeaux where it will make its way through the canal du midi under it's own power and then pick up another tow to the eastern end of the Mediterranean.

The maximum size restrictions of the canal are 30m long 5.5m wide and a draft of 1.5m.
I would like to be able to carry around 20tonnes if possible although obviously physics will decide what's possible here.

The reason for the tow is that it will be towed by a sailing ship. Ie zero emissions. The leg through the canal will be by solar power.

Could anyone recommend a craft that would fit the bill or does anyone have experience of towing barges through oceans, parcularly by sail, who could perhaps advise me.

Many thanks
Will

 

I hate to burst your bubble.
But
Sailboats don't have the reserve power to tow significant amounts.

No sailboat will be able to tow that load.

 

Welcome to the Forums Will.
As we say on this side of the pond, 'you have picked a hard row to hoe'.
Two big things stand out.
1) The limitations on canal sizes (generally Beam to Draft) means that they tend to be poor sea boats.
2) You have to cross the Bay of Biscay
That said, there are some hull shapes that might fit your needs. Historically, there are the dutch and english river lighters that crossed the North Sea, many still existent today (i.e. the Humber Keels and Dutch Botters). The Bay of Biscay has a much different sea spectra than the North Sea though, and bulwarks and decks would have to be strengthened accordingly.

Given the size limitations, there is more than enough volume and displacement available to carry 20 tonnes of general cargo, however it would still take a detailed design study to make sure all safety requirements are meet.

 

Does the cargo have some special requirements? Why not just cross load it on to appropriate boats. Using diesel and not having a barge at all would be far more environmentally responsible than towing with sail. Diesel is extremely efficient and environmentally friendly for this service, if you just go at slowish speeds - say 4 knots. Better yet, load it in a container and put it on a big diesel boat. That would be far better still in terms of environmental footprint if the endpoint has port facilities. It would probably use less fuel than the crew of the other boats use for hotel loads. People use a lot of fuel, job one is take them out of the system to the greatest extent possible. You can move 20 tons in a container about 80 miles on a gallon of diesel. The people on your sailboat are going to have a hard time competing with that.

 

Are you planning on using two different sailing ships?
One to tow the barge as far as Bordeaux, and then another one to pick up the barge in the Med, once it has traversed the Canal du Midi?
What type / size of sailing ship do you intend to use?

Phil's suggestion above is the most realistic really - and if you ship the container from England to the Eastern Med on a large modern and efficient container ship, this will most probably be both the cheapest, and the 'greenest' (re emissions) in the long run.
Even if you can tow the barge under sail effectively, the sailing ship still needs diesel as well for calm periods, and for running a generator for electrical power on board.

 

For what it would cost to construct such a barge, as pointed out, you could ship more effectively and with less total emissions, by container.
From the UK, you could cross the Channel direct to the canal network, saving any reason to get into Biscay.
Where is the "end destination" and what happens with the barge when its goods are unloaded, a return trip?
I would be looking at a Dutch/French sailing barge/lighter. Larger ones have crossed the Atlantic, so coasting in the Med should not be an issue.

 

For experience with towing, you need to get hold of officers on tugs. I am not aware of any cargo being moved across oceans by tug. I guess the reason is that the tug and barge is much less maneouvrable than a ship carrying the same cargo, and that tug and barge are likely to be in different wave systems, which puts large strains on the tow rope, and threatens to capsize the tug if it turns too far relative to the tow rope when peak loads are high.

Tugs are economical on rivers where there is not enough fetch to build up much of a sea state, and where the tug can leave barges to be loaded and unloaded while to goes off to deal with other barges. Is that why you are interested in barges?

Towing under sail has additional problems. The performance of a sailing vessel, especially its ability to go upwind, depends on the respective lift to drag ratios of everything in the air and everything in the water. If you express each lift to drag ratio as drag angle = arccot(drag/lift), then the course made good can't be any closer to the apparent wind than the sum of the drag angles. Hanging a barge off the back of the boat adds drag and so increases the drag angles. It is worse than carrying cargo, both because barges tend to be less streamlined and therefore have more drag than carrying the same cargo in the sailing vessel's hull, and because cargo carried in the hull at least can add to stability, while cargo carried in the barge does no such thing. When the wind picks up enough, you have to reef. That reduces lift, but does nothing to the aerodynamic drag of the hull and therefore increases the drag angle. Cargo in a barge adds no stability, and therefore the sailing tug has to reef earlier. There are examples of sailing vessels towing stuff with high drag, namely nets, but as far as I know, they only ever towed downwind.

I can think of only two ways around that stability problem problem. One would be a rig that generates no heeling moment, which can be done with a kite. Dave Culp's concept of the kite tug seems like the logical end point of that idea (see AYRS booklet #124 Transport Sailcraft at Booklets – Amateur Yacht Research Society https://www.ayrs.org/booklets/; note that I am one of the editors of the AYRS journal Catalyst: Catalysts – Amateur Yacht Research Society https://www.ayrs.org/catalysts/). I don't know whether the kite tug is yet practical, never mind economical.

It sounds like you already have your sailing vessel, and you want to be able to use any arbitrary barge. If you had the option of designing both barge and sailing vessel, you might scale up the Twin Foils Experiment described in Messing About in Boats some years ago. That made a proa out of two hulls, each able to stay upright on its own, connected only with string. The windward hull carries a leeboard and rudders, the leeward hull the rig.



That would let you pile silly amounts of sail onto your sailing vessel, gaining stability from the cargo without carrying the cargo in the sailing vessel itself.

If you don't want purpose-built barges, in theory you could design a paravane that is either attached to the windward side of the barge, or perhaps even between the barge and the sailing vessel. Steer by diagonal lines that shift the paravane and barge fore and aft. I tried it once on a sailing canoe. The paravane worked, steering a deep V hull not so much.





If there is an industry-standard barge for which you would design your vessel, perhaps it would be possible to design a bow and stern section that attach at either end of the barge, and are detached and joined together to sail without a barge. That would be easiest if the barge were brick-shaped. I am still not sure this would be practical even if you started with a blank slate.

P. S. If anyone knows where to find the Twin Foils patent, please let me know. My search has failed so far.

 

Zeelandia is a joy to look at.

 

Indeedy. As a younger man I had pondered on hauling cargo around Europe in such a boat, but commercial rules really took the shine off the idea. A smaller example might suit a small retirement pension better.