Does any one know at what speed ( in Knots ) does a slalom board start to plane at?
Do all boards start to plane at the same speed?
cheers
Hi Hardie,
But doesn't that mean that the boards starts to plane in different wind strenghts because of width , fin size , sail and rider weight. But they all should start to plane at around the same speed ? The speed the board is moving at as it lifts up on to the plane?
Here's a good session to look at, the wind was so marginal that I only got truly planing twice.
You can see that once the board gets 'over the hump' it accelerates well past its planing threshold.
I'd say that the planing threshold on this board (94 litre iSonic) is around 10 knots.
I'd also suggest that a boards ability to plane is affected more by the area of the flat planing surface (so width x length) rather than just width. I think it's a similar effect to 'wing loading' when designing airplanes.
So going by that info an iSonic 111 or 122 speeds should be just under 10 knots as it start to plane? So does this mean there is a very close planing window that all boards go through as they start planing of around 10 to 12 knots?
Thanks
Here's a good session to look at, the wind was so marginal that I only got truly planing twice.
You can see that once the board gets 'over the hump' it accelerates well past its planing threshold.
I'd say that the planing threshold on this board (94 litre iSonic) is around 10 knots.
I'd also suggest that a boards ability to plane is affected more by the area of the flat planing surface (so width x length) rather than just width. I think it's a similar effect to 'wing loading' when designing airplanes.
interesting subject.....i just checked my track from a very marginal sail a couple of nights ago...using an iso 105 it looked like the planning speed was around the 10 knot mark...it will be interesting to go through other tracks with different boards to see or try and determine the threshold for planning.
Jim Drake stated that a wider hull needs less speed to plane eg Forumal Board at 100cm will be planing at 8kts board speed wheras a 60cm slalom board at 8kts board speed will not be planing, just gliding. Once planing speed increases rapidly.
I just went and checked my tracks for my I-sonic 122 (75cm wide) with realspeed.
It looks like the board speed is between 9 - 10 knots to plane. It looks like its a very narrow window for all boards to hit the planing threshold.
I was surprised by my alphas a lot of them have minimum speeds around 12kts, but I'm sure I planned all the way round. I had thought planning speed was higher than that. So I'll go along with 10-12kt
I've checked more sessions for my I-sonic 122 and it looks like i'm wrong. I now think it is between 10 to 12 knots board speed to plane.
I think there's another way to look at this.
One definition I've seen of planning, is when the hull climbs over the bow wave and starts surfing down it.
All you need to know is the propagation speed of bow waves. (which is strange cause I thought I read somewhere that waves move about 15kts)
Think that will depend on a few things, like water density and depth. If I'm correct the planning threshold should be lower in shallow water, but not easier, because the bow wave will be bigger and harder to get over.