Das Boot – motion in big seas

This is more than just for interest’s sake, it is one of the key factors confirming my hull configuration. As those interested know, there are near identical versions of das Boot in mono form with ballast … or in catamaran form.

Have a look at this:

N1

This is an article on drogues:

https://www.yachtingworld.com/features/a-jordan-series-drogue-63180

Compare the motion through the water, 24/7, to this:

N2

Now let’s look at this:

N3

Notes

1. Cats such as Nos 1 and 2 are floating homes, tubs, hugely buoyant, highsided and with large wheelhouses. Roundbottomed and shallow, they can slide left and right, yaw round like deep fin keelboats. Roundbottoms are for speed and nontippability.

The opposite is a cat ‘on rails’, short [shoal] keel, full length, same with the mono. That tracks much better through angry seas downwind, and both those clips are of downwind or downwave surfing – N3 is sliding and yawing.

The solution in a mono is shoal keel or two bilge keels, both very popular in earlier days around Britain and the European coast.

In a cat, way to go is no keel but some vee, which neither of those floating tubs had. An example is the keel-less Wharram range, underpowered. But the best solution is never broach or lie side-on as a strategy – always either head into wind/wave or stern to wind/wave in severe conditions.

The solution downwind in N1 was to deploy a drogue [by far my preferred solution is to ‘run before the wind’] which stabilised her as long as the seas didn’t start this criss-cross, rogue wave biz. Also, one needs a winch to get the drogue back in. Par for the course I’d have thought.

I would suggest in a cat – some vee below in the hull, better tracking, but not too much, straighter sides, low wheelhouse protrusion, open deck with one rounded, low-lying central pod on deck to steer from, not too much freeboard.

Less important in a ballast-mono but still worth noting.

2. Obvious next question is why designers moved away from the well-founded designs from the 70s on – bilge keelers and the ancient Colin Archer types spring to mind in the monos [the Westerlies for example] – and the answer is commercial firms – speed, large accommodation wanted these days, plus that same factor in cars – they’re all becoming the same, computer generated.

I prefer the older designs which generally came through day after day, e.g. the fishing boats or Polynesian multihulls. Not floating palaces but seaworthy.

The old bilge keelers for example, were compromises for our conditions, not particularly great at any one thing but good all round and still popular, except designers are just not doing them anymore.

3. Coming back to the issues N3 was having, which N1 was not, yes it was certainly the tracking through the surf and any craft caught on top of a crest will yaw at least a bit, but one more thing and I’ve already put this in my designs – let’s look at side, not stern-mounted rudder[s].

The Viking boats all had them, the Polynesians use them now, the rudder to the side, not far from the stern, is a sensible idea if the blade can swing up when hitting obstructions and stay down when not hitting anything solid.

By the way, there is this word one encounters called ‘pooping’ – it’s when a following sea dumps down on the stern of your boat – you see that danger constantly with N1 above.

This is why the old boats were often rounded stern or pointy ended, this is also why N1 was sailing downwind without sails – the high wheelhouse back was a giant sail. What’s worse – doors are glass on such boats. The sane use acrylic if they must have high backs at all.

My sailing station is some 8 feet from the stern, the rudder 4 feet.

Now, coming back to N3 – you noticed her stern up in the air. No rudder traction, no ‘rails’ to run on. Rails and side rudder would help as she came back down.

Think it through further and the cat has two rudders. If both are between hulls and 4 feet for’ard of the sternposts, then tillers can be used direct-to-helm, no linkages needed.  The rudders are therefore protected from the sides and to an extent, from behind, but still not from below – that still requires a rounded rudderblade form, swing-up.

The now abandoned oar steering had things going for it, you know.

Downside of rudder forward is traction – off-stern rudders have better traction. But think of the old racers of the 30s, e.g. in my header – where are their rudders?

I believe we really can learn by observing what conventions were and more importantly – why they were.

4. Now, the last thing is this pooping. Truly by coincidence, the cat version of das Boot has two loos, each at the stern, behind the aft cabins. And as the sea does its thing at the stern, I propose that this boat does not have a ‘stern’ but a ‘derrière’ and that those two littlest rooms be called poophouses.

To compound the joke, the raised deck at the stern of old ships was called … yep … the poop deck. And as the English enjoy schoolboy poophouse humour … w-e-e-e-l-l-l.

One last thing – a dear friend has what was once a baby daughter who used to call the waves or water ‘wabu’. I suggest that that’s as good a name as any for what is chasing those two in N1 above.

One last, last thing – what they were doing in N1 was deploying just enough cones for them to keep crest-riding – not too fast, not too slow, way to go.  Speed is not the first priority downwind in those conditions.

The catamaran configuration with low deck and rig, I’d suggest, is the first priority.

2 comments for “Das Boot – motion in big seas

  1. April 26, 2019 at 19:07

    “She”.

    • Andrew
      April 26, 2019 at 19:51

      “It”. After all, in these wonderful modern times who are you to attribute a gender to it? There are more options to choose from than in the old traditional days of your youth, you know.

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