About speed

[Michael Rogers]

With regard to Jeremy's post above, there is at least one water skier (Irish, I believe, but I'm sure that's irrelevant) who, having bought his skis, has been looking for a sloping lake to ski on. Perhaps his search will not necessarily be in vain?

[Colin Morley]

Impressive Colin !
This is exactly the point. Even assuming 2 knots of confidence level, the speed is quite above the theoretical hull speed and the BR must be planing then, do you agree ?   From what speed on does she start to, if so ? Could you tell us more about her behavior at 11 knots ? One day it would be interesting to see a video of that moment.

Guy
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Catchando Bay (BR 48)

All I can do is quote what the GPS read out was. It is a Garmin 556S. I find it hard to believe that a GPS readout is systematically wrong. I appreciate that this is speed over the ground and may be affected by tides, currents etc. That is why I quoted the speed on a lake. If one looks at windermere on a still day it certainly does not look as though there are surface currents.
My experience is that my BR certainly picks up speed and goes remarkably fast in a stiff breeze. It is certainly going much faster than 5 knt

[Guy Rossey]

Colin,
no doubt you reached this speed. My point is that since the BR is planing from 5,7 knots on and that really higher speeds can be observed, even if in some other cases currents may reduce the true speed  : how does the BR behave when planing and how manageable is she then from your experience ? You reached the highest speed apparently and 11 knots must be exhilarating indeed.
Guy

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Catchando Bay (BR48)

[Julian Swindell]

You have to be a little cautious with GPS speeds. The figure tells you how fast the GPS unit's aerial is moving through space at a specific point in time, it isn't directly measuring your boat speed as such. If you are swooping over the crest of a wave, the unit itself is being sung rapidly through an arc, and this can result in a momentary speed peak which is way out of the ordinary. Similarly when you gouge through a trough in the waves, the boat as a whole is clearly still moving forward but your GPS speed might apparently drop right down to 0. The temptation is to see the maximum speed recorded and get the thrill that you are really blasting along at that. I made a mad dash to the Solent from Poole in the summer in a following F7-8 wind and apparently hit 9.1knots at some point (I didn't see it, I had other things to concentrate on, like surviving) I don't think I was doing that really, the unit was reading around 6-6.5kts much of the time, and the moving average was a more modest but very creditable 4.5kts.

Having said that, BayRaiders and Cruisers can clearly plane, especially unballasted. They are just big dinghy's with flat bottoms after all. I should say anytime you are holding a speed of over 6kts you are planing. If the wind increases, the sea is smooth and your nerve holds, the sky is the limit after that...

By the Way, my spell checker just suggested the correct spelling fro BayRaider was backslider...

[Julian Swindell]

I reckon Daisy Grace is planing in this photo...

[Colin Morley]

Interesting comments.
I guess you are right about the hull speed and planing although when ever I look at the formula for calculating boat speed it seems a bit of a fudge. In the past I raced a Wayfarer and was well aware when that got up on the plane. I have not noticed anything like that with the BR. When the GPs says we are going fast the boat seems just as steady as at slower speeds particularly if we adjust the sails to keep her flat.
As for my GPS rocking about, I am sure that is theoretically possible but the GPS sits on the back end of the centre board case, so it is not high in the air. We have not been sailing when there are big waves - except when one of those nasty stink boats goes passed too close and too fast and then I am too focussed on cursing them than looking at the GPS.
I suppose what we need is a BR time trial. Any one for a race? About time the BR had a Portsmouth yardstick.

[Peter Cockerton]

Julian

It does indeed look as if she is planing, what opinions are out there on angle of heel and planing then, this would also relate then to the point of sail as close hauled as the boat is likely to be heeled greater with the same amount of sail up then if she was reaching. What point of sail and how flat must she be to get the hull on the plane.

I have got myself all wound up this, i don't know why as i'm normally quite happy to meander along at 5.0 kn, who started this thread.

[Julian Swindell]

Hi Peter
I tend to sail as upright as possible. In the photo I have got one reef in and am sailing close hauled and fairly upright. I was "posing" for the Practical Boat Owner photographer who was writing the article on the Baycruiser last year. He kept asking me if I could shake the reef out, and each time I got ready to do this the wind got up and I took off. I was unaware of any instability or erratic movement. The BayCruiser tends to be rock solid (with ballast in) and the only vice to watch out for is a tendency to broach when sailing down wind in F8...

I would say you are unlikely to plane if you are heeled too much, the boat needs to be fairly flat.

[Michael Rogers]

IS it possible to plane close-hauled?? Surely, in the first place it would be difficult to sail fast enough (although it does seem to be remarkable what you guys with built-in water ballast can do in a really fresh wind): secondly, and critically as I understand it (which isn't very well, I must admit), you would be planing with the board down - which simply isn't possible - is it??

[Peter Cockerton]

I'm going to try these words of wisdom next time i'm out if conditions permit

Techniques used to promote planing in a sailing boat
Albacore dinghy planing

Planing in a sailboat designed for it is promoted by the usual techniques for increasing speed:

    Sailing on a reach or broad reach to begin
    Raising the centreboard or daggerboard
    Keep the hull level, trapeze if necessary

in addition to these:

    Moving the crew weight increasingly towards the rear to begin and to sustain planing
    Flicking or pumping the sails (although there are restrictions on doing this in a race)

While planing, it is important to steer through the waves, avoiding any collision with the wave in front.

Will let you know how i get on.

PS The trapezing will be another day when youth and gullibility on board


Peter

[Julian Swindell]

Flying 15s plane and they are keel boats. I don't think there are any special reqirements for planing other than fairly smooth water, fairly upright boat with a flattish bottom, fair breeze and going like stink, which usually means a light boat and lots of sail area. Spinakers help because they tend to lift the nose if they are working properly.

[Terry Cross]

After reading all the comments on speed, rumour has it that Matt is busy designing a hydrofoil version of the Bayraider.
To see his prototype  Google:  UTUBE Moth

[Anthony Huggett]

I think it is theoretically possible for a sail driven craft to plane upwind. Sailboards certainly do, and I believe some of the high performance racing skiffs can also manage it.
A boat planes when it is no longer floating (hydrostatically supported), but the forces of the wind and water take over so the boat is hydro- and aero- dynamically supported. It is skimming across the surface of the water, the wake becomes detached from the boat.

The problem with a dinghy is that most of the lift (in the up and out of the water sense) is coming from the hull, (unlike a sailboard where the rig inclines into the wind and provides a lot of lift). On a beat most of the force produced by the sail is acting sideways (which is why you have the centreboard down to reduce leeway), so only a fracton of the available force is pushing the boat forwards. The wind and waves are also slowing you down, acting against the hull.

So whilst it is possible to plane to windward it is unlikely that it can be achieved by a cruising boat because the sideways force increases to capsize proportions before the forwards force is stong enough to get you planing. If someone wants to prove me wrong with a twin trapeze on a BR I'd love to be corrected!

[Colin Morley]

I owe you all an apology.

Earlier I had written that my BR20 was doing over 11 kt and was told by several very knowledgeable people that this was impossible with a 20ft boat.

I have now found that my Satnav was reading 11 kh, which I foolishly thought was knots per hour. I was wrong kh is the shorthand for kilometers,hour.

Today I set it to knots/hour (abbreviation kt) and found I was doing about 6 knots. In one gust the boat lifted onto the plane and was doing 7.5 knots. Not bad with four adults and water ballast. beating back into a force 4/5 wind with just jib and mizzen we were doing about 5 kt. The BR20 certainly sails well.

So message - beware of confusing the abbreviation kh and kt when referring to boat speed.

[Julian Swindell]

The pedant in me can't resist. They are not knots per hour. A knot is a nautical mile per hour, so a knot is just a knot. Knots per hour would actually be an accelerationn, not a speed.
For the discussion, my Baycruiser can often get up to 7kts in a breeze, and once actually hit 9.1kts in a wind that I really shouldn't have been out in. But generally she cruises at around 4-5kts. The theoretical hull speed is just that, theoretical. The Bay range of boats are so light and so flat to the rear that they are really semi-planing hulls and are not going to stick to theory if the conditions are just right for them. On one of my first sails with my daughter we had just the right gust on just the right wave and hit 8kts against a strong current without even trying.
To put it in perspective, 7kts is about the speed of a jogger! Sailing is the only sport where you get high speed thrills whilst actually going quite slowly.