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Author Topic: Has anyone modelled a Walker Wingsail yacht yet?  (Read 1150 times)


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Has anyone modelled a Walker Wingsail yacht yet?
« on: August 25, 2011, 09:47:16 PM »

I worked there for many years, and the boats should make good models. The real wing had plenty of spare power

I have uploaded a picture of the complete boat and another with just the wingsail details

Referring to the close up wing picture, The wingsail assembly consists of a fixed wing that is the bit with the union flag, a tail which is the thinner bit to the right, and a moving wing that sits in front of the fixed wing. The moving wing can be positioned in 3 places, trailing edge right, where it is now, trailing edge centred, or trailing edge left. Consider these positions to equate to full power potential right, zero thrust, and full power potential left. The tail pivots to lets say 30 degrees left or right, with a central position that equates to zero thrust.

The entire assembly you see sat on a free to rotate bearing, that is positioned at the line in the lower conical fairing, and with the tail and moving wing portion centred, the whole lot rotated on a vertical axis just like a weather cock. This gave very little drag and no thrust, so this is where you put it when in dock.

The lower fairing structure, horizontal boom, and the"fixed" part of the wing with the Union flag are all fixed, relative to one another, with the wing aerofoil shape centred on the booms axis.

In simplistic terms, to power it up, you decided which tack you wanted, and positioned the moving wing either fully left, or fully right. This shift away from "everything centred" gave the pair of wings(combined)the classic wing shape, with less pressure one side than the other and some power was then increased this effect by using the tail to force the whole wing into a better angle of attack, just like a plane deploying flaps and lifting the nose.

So, let us now  pretend that the wing in the picture is centred in zero thrust position,(which it isn't) the wind is coming from the left, and the whole shebang has settled into the wind, with zero thrust... Now, imagine the front "moving" wing was rotated so its trailing edge moves away from you 30 degrees, to the position actually depicted. Immediately, the entire assembly will now rotate slightly to find a new equilibrium, with the left end of the boom coming towards you slightly and the right end of the boom moving away from you, taking the tail "out into the airflow" with wind pressure hitting it's far surface. The wing "pair" will now settle at a new angle of attack, and we can reasonably call this position "In first gear, clutch out at tick over", as the whole structure rotated on the bearing to find the a position of least resistance, but, as the far side of the wing now presents a longer path for the airflow, producing a low pressure, with a higher pressure this side, we get lets say 10% thrust away from us. To now increase the thrust on this chosen tack, the tail has to be rotated away from it's central position, moving it's trailing edge away from us. The forces on the tail now bring the tail end of the boom towards us, and bring the trailing edge of the wing assembly towards us as well. This puts the wing at a better angle of attack to the wind, more lift is produced, and we are cooking on gas! the more you turn the tail the more power you get, up to a limit, just like the aircraft analogy.

In the picture of the  complete boat, the assembly is on the other tack, with the front moving wings trailing edge 30 deg this side of boom centre, the tail is turned so its trailing edge is towards us, and the low pressure side of the wing assembly is on our side.

Hope this all makes sense! I can elaborate more should anyone decide to make one. It beats all that "flappy sailcloth rubbish into a cocked hat :}

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