Max Draft With a Sailboat on the French Canals

[Oyvind]

Hi all,

let me start by introducing myself. I'm Norwegian and live in Bergen, the 'Capital of the Fjords' on Norway's west coast, with my wife and three kids. I have no previous practical experience with narrowboats and canals.

 

However, we do have a sailboat that we spend most of our summer vacations in. As the kids are happily growing, the need to upgrade our current 28' family sailboat is becoming more and more apparent.

 

I'm eyeing a specific yacht that is for sale in the eastern Mediterranean. I'd rather not be too specific about it for the time being. Suffice to say that the length is 40'+, built in the middle of the 80's as a serious blue water cruiser to a very high standard. The asking price is quite reasonable, perhaps because the yard was not known for prestige yachts and this particular model, which was their luxury model, was not made in large numbers and is fairly unknown in the market.

 

Now, one of my family selling points is that we could bring this yacht home through the French canals, which I imagine would be a quite enjoyable experience for the whole family. Only one smallish problem, the design draft is 1.9 meters. While this is OK for both the Rhône and Seine rivers, the deepest canal that links these two rivers, the 'Bourbonnais Route', has a stated max draft of 1.8 meters.

 

I'm only just starting to learn about inland waterways, but I understand that the canals on the Bourbonnais route were constructed to the 'Freycinet gauge', which specifies a minimum depth of 2.2 meters. This suggests that there is actually a clearance of 0.4 meters between the maximum draft and minimum depth.

 

I've been thinking about this, and come to the conclusion that a barge needs this clearance to the bottom because the water that the barge displaces needs some room to move around and under the hull. I believe there are some considerations re. the Venturi effect, where a hull moving over very shallow water may 'self-ground' so to speak due to the pressure reduction as the water speeds up under the hull?

 

With a sailboat, where the deepest point of draft is represented by only a thin point, there should be no such concerns. Am I right in thinking that, with a sailboat my only concern should be minimum depth and not maximum depth within a reasonable margin of safety? And will the French authorities agree with me on this one?

 

There is the alternative option of lightening the boat as much as possible, of course, and if that is not sufficient then lash some large, inflatable 'sponsons' on either side to lift the hull out of the water on the shallow parts.

Edited October 26, 2009 by Oyvind

[mykaskin]

I'm only just starting to learn about inland waterways, but I understand that the canals on the Bourbonnais route were constructed to the 'Freycinet gauge', which specifies a minimum depth of 2.2 meters. This suggests that there is actually a clearance of 0.4 meters between the maximum draft and minimum depth.

 

Navigations - especially now non commercial ones are not always as posted. Having a keel does make it easier to pus through, but at the expense of damage and rolling.

 

Mike

[Tam & Di]

I'm only just starting to learn about inland waterways, but I understand that the canals on the Bourbonnais route were constructed to the 'Freycinet gauge', which specifies a minimum depth of 2.2 meters. This suggests that there is actually a clearance of 0.4 meters between the maximum draft and minimum depth.

 

The Freycinet depth on waterways more or less south of Paris is 1.8m - 2.2m is for those to the north. Lack of dredging maintenance leaves this as an optimistic figure on the lesser used canals. There are a handful of Freycinet craft which do trade to the south and use the Marne à la Saône canal, so it is better than some, but not much. You should get through, but it could be hard work, and especially if you happen to meet one of said loaded Freycinets as there is nowhere for him to move over and make life easy for you.

 

Presumably the family are not keen on doing what yachts are made for and going round the edge?

[tosher]

I spent three years cruising the french canals, mainly south & west, in a 47 foot GRP ocean going sailboat drawing 1.8 mtrs. Ran aground constantly! Removing non sea going equipment including the mast made very little difference to the draft. Finally removed the 9 ton cast iron keel and substituted it with a fabricated steel 1 ton long shallow keel and reduced the depth of the rudder by a corresponding amount. This lifted her about 12 to 15inches above her marks and reduced her draft to 1 mtr. In this configuration she remained very stable and we were able to make a few short passages to sea in calm weather. But my greatest fear by far was puncturing the under water bilges on the rocky bolders which seem to line most of the canals, this seems to be the favoured method the french use to protect the banks from erosion. My advice would be to buy steel for the canals and the closer to 1 mtr draft you can get the better. Hope that helps.

[Oyvind]

Thanks all,

I would probably ship the mast overland, but mostly to protect it from damage and avoid deck clutter. The weight of an aluminium mast is not all that great, I can lift and carry the mast of my present 28-footer myself, but I suppose anything helps.

 

One option I'm contemplating is to lash some very large "superyacht" inflatable fenders on either side of the boat, below the turn of the bilge and with straps under the hull. The idea would then be to inflate these when needed to lift the hull out of the water. I'm eyeing some that are 60cm x 300cm and should provide up to 1.6 tons of lift. Dunno how much this would actually raise the boat out of the water, though. I would expect this to be a fairly complex equation since hull buoyancy quickly diminishes as the hull is raised, and I do not have any line drawings to refer to for calculations. Also, the prospect of puncturing one of these fenders on a shallow stretch is not a very pleasant one... Still, I haven't quite given up on this idea

 

As for going around, that is not really an option with a husband-wife crew and three small children. Yes, I'm aware that more people have motored across a calm Biscay than have had to endure a storm, but you have to prepare for the worst (and hope for the best...). Family cruising is basically shorthanded sailing, and much of the time you're actually singlehanding. It's OK for a short hop across the North Sea, but not something I'm eager to do in the heavily trafficked Biscay.

Edited October 27, 2009 by Oyvind

[Teadaemon]

Personally, I'd be inclined to suggest that reducing the draft by attaching some sort of home-brew buoyancy bags is not a practical option, and probably not one that the French authorities are likely to be happy with (not to mention your insurance company).

 

I would suggest that since you're an experienced sailor and the boat sounds as though she'd be well suited to it, that going by sea is likely to be the quickest and easiest option. I can fully understand your unwillingness to do this with a young family on board, so my suggestion would be to use a passage crew for the difficult part (which I'd guess might be from the Straights of Gibraltar to the Eastern end of the English Channel), with the rest of the family aboard for the easier parts of the journey.

 

The other option, which I'm not particularly familiar with, would be to investigate other inland routes to see if there is one deep enough for your new boat. Since you say that the yacht is currently in the Eastern Med, how about going via the Rhine-Main-Danube Canal? It's definitely big enough, and would avoid having to sail through the English Channel when you get out to sea at the other end.

[Oyvind]

I've investigated the Danube option previously. The primary problem seems to be that the Danube is very fast in places, 6-8 knots, so it would be next to impossible to make any progress with your average sailboat. Apart from that, there is generally not a lot of information available on the Danube alternative, it hasn't been much developed for tourism yet apart from hotel barges. What I have learned, though, is that there is a very real risk of piracy in the lower parts of the Danube, in Rumania, so boats are not recommended to stop there.

 

Yes, the boat in question is a serious blue-water cruiser, so is eminently suitable for the outside route. That may very well be what this boils down to. Do some Spanish and Portugese ports, and then ship off the family to Euro-Disney or whatever while dad takes on a few buddies, or a paid crew, and go for a quick dash across the Biscay

 

Thanks for your inputs

Edited October 27, 2009 by Oyvind