Submitted to Yachting World magazine by the author:
"I was fascinated by your special feature, 'Greed for Speed', in the May, 2002 edition of Yachting World, but I was left with a nagging question in my mind - if a land-yacht can hit 100-knots+, why can't a water-yacht? What's the difference? Well, 'wheels'. This got me thinking: if maintaining the vessel/water contact via a hydrofoil or a fixed-float/'skid' has hit its natural limit, what about fitting a wheel or two instead?
To take this further I came up with the following design concept: picture a body very much like a glider; attach a mast; replace the tail-section with a buoyant wheel; and adjust the weight distribution such that, at speed, the tail is subject to a moderate, downward force - say, the equivalent of a 20 to 30-kg mass - in order to keep it in constant contact with the water. At speed, only the tail will 'drag' in the water and this single point of contact will rotate instead of being fixed. You can see a picture of this concept (and get a bit more detail) at [link to this page].
The idea can be optimized to provide an asymmetric platform by lengthening the leeward wing (and/or shortening the windward wing) in order to provide more lift on the leeward side of the vessel. To steer it, any/all of the following could be used: an aileron-type rudder on the nose (i.e. works by the action of air, not water); a pivoting rear wheel; a mast-canting system (c.f. Unlimited Speedsailer).
Has anyone tried this concept already? Wouldn't Yellow Pages be faster if it replaced its fixed-floats with rotating ones?"
Here's a picture of what I was endeavoring to describe (not to scale), followed by a little more design concept detail...
- A pair of smaller float-wheels are fitted to the under-side of the wings in order to provide a stable platform when the vessel is at rest and as it gets up to speed. These lift clear of the water's surface once the vessel is up to speed.
- The cross-section of the rear float-wheel will need to be optimized. A sphere will provide the maximum buoyancy for a fixed surface contact area, but will provide little directional stability. A more elliptical wheel will also provide more control of spray. This spray represents a significant drag factor and the spray shield in the concept above is in the shape of a cardioid curve. A cardioid curve ensures that tangentially flung spray will be intercepted at exactly 90° which provides maximal ability for spray momentum re-capture. A spray shield that re-captures spray momentum in an upward and forward direction could help to provide a small boost to the vessel by way of additional lift and thrust.
- An variant on the above concept could involve 'force-spinning' the rear wheel (by a wind-powered, mechanical linkage in order to stay within the spirit of the speed-yacht design brief). This would further reduce drag at the surface contact point, but bear in mind that a rotating body generates lift (in this instance in a downward direction) and thus will effect the buoyancy experienced by the vessel's tail section.
- The wings of the vessel have ailerons to control the height of the vessel's nose at speed. An angle to the water of around 10° needs to be maintained when the vessel is at speed in order to keep the main body clear of the water's surface.
- If a mast-canting device is not fitted, the mast should be vertical when the vessel is at speed (i.e. will be canted forward when the vessel is at rest).
Further Ideas On This Theme...
A more 'mainstream' application of the water-bourne wheel would be a dinghy whose body resembles a giant in-line skate (rollerblade) stabilized by a pair of small outrigger wheel-floats. People will only laugh at you until you burn past them at 65-knots, after all.
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