Forums > Windsurfing   Gps and Speed talk

Planning

Reply
Created by Bilabog > 9 months ago, 6 Jun 2009
Bilabog
NSW, 211 posts
6 Jun 2009 12:45PM
Thumbs Up

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

hardie
WA, 4076 posts
6 Jun 2009 11:06AM
Thumbs Up

Bilabog said...

Does any one know at what speed ( in Knots ) does a slalom board start to plan at?
Do all boards start to plan at the same speed?

cheers


Depends on the width of board, sail size, fin size and rider weight. With all non-board variables equal, the width of the hull is probably the most important factor in planing. Wider hulls plane earlier. My 80cm wide slalom board planes in about 10kts, needs to be pumped onto plane, then will stay on plane. My 48cm Missile speed board probably needs an absolute minimum of about 16 to 18kts to get planing. My 60cm wide slalom boards need about 12 to 15 kts to plane.

Bilabog
NSW, 211 posts
6 Jun 2009 1:18PM
Thumbs Up

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?

hardie said...

Bilabog said...

Does any one know at what speed ( in Knots ) does a slalom board start to plan at?
Do all boards start to plan at the same speed?

cheers


Depends on the width of board, sail size, fin size and rider weight. With all non-board variables equal, the width of the hull is probably the most important factor in planing. Wider hulls plane earlier. My 80cm wide slalom board planes in about 10kts, needs to be pumped onto plane, then will stay on plane. My 48cm Missile speed board probably needs an absolute minimum of about 16 to 18kts to get planing. My 60cm wide slalom boards need about 12 to 15 kts to plane.




nebbian
WA, 6277 posts
6 Jun 2009 11:26AM
Thumbs Up

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.

Bilabog
NSW, 211 posts
6 Jun 2009 1:40PM
Thumbs Up

Select to expand quote
Hi Nebbian,
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.



nebbian
WA, 6277 posts
6 Jun 2009 12:13PM
Thumbs Up

Bilabog said...

Hi Nebbian,
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


I'm no expert, but from what I've experienced you're right on the money. Most boards that I've tried get planing at roughly the same board speed (which is different to wind speed!). It's hard to tell because once you start planing you accelerate to well above the threshold...

snides8
WA, 1729 posts
6 Jun 2009 12:53PM
Thumbs Up

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.

hardie
WA, 4076 posts
6 Jun 2009 1:42PM
Thumbs Up

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.

Bilabog
NSW, 211 posts
6 Jun 2009 4:42PM
Thumbs Up

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.

decrepit
WA, 11823 posts
6 Jun 2009 7:33PM
Thumbs Up

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

Bilabog
NSW, 211 posts
6 Jun 2009 11:19PM
Thumbs Up

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.

Bilabog said...

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.


decrepit
WA, 11823 posts
7 Jun 2009 6:30PM
Thumbs Up

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.



Subscribe
Reply

Forums > Windsurfing   Gps and Speed talk


"Planning" started by Bilabog