Finding downwind speed – Planing in OzRacers and OzGeese.

From the OzRacer Archive.

Planing and speed downwind in squareboats

There was a lot of discussion about whether the OzRacer would plane. Bolger had said the original boat, the Brick, would not. Was he right?

The OzGoose at 12ft, but otherwise similar, planes very easily and has much more moderate behaviour.

The position of the Australians (ie us) was that they had enough sail and were light enough and if handled firmly enough … “they probably would”.  But what handling methods would be necessary?

So here was the strongest wind we had sailed in, so…Follow the story!

Went for a sail today up the river here.

Ran out of wind because the river is narrow and there are lots of trees on either side partway up – so wasn’t able to keep pace with the outgoing tide – but wiled away a couple of hours very nicely catching the catspaws, making a bit of progress and then losing it when the wind died or when i hit a mudbank or rock ledge with the centreboard.

Pleasant sailing indeed.

On the way back came out of the trees and the wind had picked up a bit.

Probably very close to a solid 12 knots with short puffs a couple of knots more.

Anyway – a couple of times I was on a beam reach, caught a puff and the boat accelerated onto the plane briefly.

Much of my life I have raced fast planing dinghies and sailing canoes so today – definitely on the plane – maybe for about 10 seconds each time.

Flat wake – little rooster tail off the rudder.  Stern wave moves about 6ft behind the boat – this correlates to a speed of around 4.5 knots which also correlates quite well with the speeds others have been getting on their GPSs

If there had been a few more knots of breeze the PD Racer would have been solidly on the plane so am looking forward to more wind (forecast tomorrow along with thunderstorms).Note too that the river here is quite protected by trees down one side and buildings down the other this

a/ Cuts the wind velocity and making gusts short and sharp – not good for planing
b/ Keeps the water flat – good for maintaining boat control easily.

Keep it flat by steering and sail trim

Certainly did notice some of the bow digging behaviour that some of the sailors of the 8ft boat have mentioned – it certainly happens if you don’t trim and steer to the puff quickly enough and a move back about 8 inches along the side of the boat at the same time as hiking your body hard to keep the boat just a little short of dead flat..  But if you get it right and the boat accelerates lifting its bow high so theres little risk of sticking the nose in.

Get it wrong and the OzRacer and the other 8ft ducks pigroot. it is easy to fix and the boat is happy to go where it is pointed, unlike a lot of other boats.

The PD Racer is certainly the most sensitive boat I have ever sailed as far as for and aft crew placement.  A few inches too far forward and the bow digs a bit making noise and making waves (creation of waves, sound and turbulence indicate the loss of energy that could be used for driving the boat if they were eliminated).

You can see all of this happen in this planing video with Dave Gentry sailing. The OzRacer has a bouncy look as speed jumps up and down – with any deceleration the bow drops into the water with the start of the gust, the crew has to move back -the boat accelerates and the bow comes up.   Its not a “flat out” plane by any means – not enough wind or space – but yes it is planing.

Compare with the Oz Goose in a much lighter wind. It is planing so easily it is dreamlike. No jumping up and down of velocity. Just a lovely smooth movement without stress or strain.

I found myself sailing it much like a catamaran – move as far forward as possible without the flat of the bow actually hitting the water.

It is also important that when the sail is eased to keep the boat flat to bear away to keep the sail full of wind. The boat will still stay flat because the angle of the wind is now pushing less sideways to cause heel and more forwards to give speed.

You can see this clearly in the Goose Video here in much much more wind. Sail out, bear away, run out of power, point up, sail in.

There is an explanation of the Goose planing video here.

When the power reduces pull in some sail while pointing higher to keep the speed up by balancing your weight against the maximum power the sail can develop while still keeping the boat flat.

In the goose video above, the wind is well over the level where normal sailors will go out with full sail. It was a cancelled race day with a crash boat and start boat nearby.

Lateral weight is also important as much heel will cause either the bow or stern transom to be immersed causing splashing and/or turbulence.

I can look out of the window here and see the PDR with its sail rolled around the mast lying on its side to stop it from blowing over if the wind gets strong tonight.>

Hope it stays strong for tomorrow morning – tide will be high to increase the length of the runs I can make.

Sadly Biting Midge has gone back to work – so no photographer OR camera.

Best Regards
Michael Storer

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