Published by the Open Canoe Sailing Group

Lift (Paul Marks)
From New Scientist, 15 Oct. 2005

Pterosaurs, the reptiles that ruled the air 200 million years ago, had a neat aerodynamic trick. Like aircraft today, they used wing flaps to generate extra lift.

The discovery may help clear up an enduring mystery of Pterosaur flight. Calculations on what we know from fossils failed to explain how they could have generated enough lift to become airborne from a standing start, or fly slowly enough to land without breaking their bones. Yet fossil tracks show that they could do both these things.

The riddle has been solved by Matthew Wilkinson and colleagues in the animal flight group at Cambridge University who have studied well preserved fossils from the Santana formation in Brazil. Earlier calculations were wrong, say the researchers, because they did not take into account an articulated bone called the pteroid, which Wilkinson says supported a flap of skin at the leading edge of the wing that could be angled downwards to increase lift.

"Even the largest Pterosaurs may have been able to take off simply by spreading its wings while facing into a moderate breeze", Wilkinson says. Similarly the enhanced lift would have cut the creatures flying speed by about 15 per cent, allowing them to land smoothly and safely.

To find out if the wing flap aided lift Wilkinson built an aluminium and nylon scale model of a broad forewing and tested its aerodynamics in a wind tunnel. It had extraordinary aerodynamic properties, he says, boosting the lift by 30 per cent.

In normal flight the pteroid bone rested at 10 degrees, but when extra lift was needed for low speed take off or landing it could be deployed to between 40 or 50 degrees.
 

Access To Water (RoyB)

I noted recently in the press that the BCU, following the recent opening of access to open countryside, is to begin a campaign for similar access to water. We have heard from EddieP of a law of this sort in Scotland, but in the more heavily populated, crowded landscape of England and Wales opposing interests might well prove too strong.

Included in the activities the BCU says would benefit from such access is gorge walking. I wonder whether the plants and creatures in gorges would relish the prospect of armies of humans scrambling through their homes? Still, that has little to do with canoe sailing.

Reservoirs (Rutland Water, for instance) that provide drinking water, the property of private utilities, would be unlikely to come under such provisions, I think.
 

Spinnakers On Canoes (RoyB)

How about spinnakers on canoes? Here Ann and KeithM on Windermere, probably...

"Near Perfect" Trimaran (RoyB)

GOSSIP has received from TrevorB a copy of an article in the bulletin of the AYRS which describes a trimaran designed by Louis Macouillard. This design is 'as near to the perfection of the configuration as we are likely to see for some time'. When this was published is unclear, some time may have elapsed, Solway Dory may have edged that bit closer to perfection but what interests the editor most about the craft is the shape of the floats. They are of square section set so that an edge, not a face, comes in to contact with the water when the boat heels slightly. This edge sweeps "up to a point both fore and aft, there can be no dragging of water behind them no matter what the immersion".

The main hull is of very simple design: a flat, rockered bottom and a single flared plank either side. Apparently it is a dry boat, having a very fine entry and generous freeboard, a point that was made to me when I was considering building a trimaran for myself. Indeed, my boat, which is now under construction, has much higher sides than my monohull canoe. This might seem unnecessary as the degree of heel on a trimaran should be less than one would expect with a monohull. Perhaps it has something to do with the narrow beamed main hull not throwing aside waves as well as a broader bow would do. If anyone has any ideas on this, GOSSIP would be interested to know.

The writer of the article considers that a simple 'vee' cross section on the floats with a flat deck on top would be better, as when 'the side chines of the box section become immersed due to wind pressure eddying flow will occur'.

Trevor, who first made our acquaintance at Hickling Broad, is about to start building a trimaran. Let's hope we see it in action at Hickling (at the latest) next year.

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