I was wondering if anyone has studied the effect of wind gradient for landsailing here?

US772 said...

I was wondering if anyone has studied the effect of wind gradient for landsailing here?

I think the simple answer will be NO....

Its one of those things land sailors can't do much about (unlike kiters).
To some degree the evolution of rig design has been limited by a few unchangeable things, In Class5 the mast height / length is regulated in the class rules, and in the Mini5.6 the mast configuration has tended to be composite sailboard masts (preloved / used)
Rigs for landyachts over the years have changed, in the early days the 'Manta' low aspect style was the normal, this tended to change to a slightly higher aspect ratio as yacht performance increased, but on the other side to that is at some very windy locations people tended to stay with the lower aspect ratio for yacht stability.
Some people have lowered yacht chassis to get the CG low to the ground for stability yet by doing this it sort of makes the yacht site specific.
I was recently contacted re; the advantage of making a yacht with 50mm ground clearance.... that might suit a very smooth salt lake but on a coastal beach the yacht would be useless with clumps of seaweed that wash in.

This might be a starting point.
cdn2.hubspot.net/hub/209338/news/Ad_aerodynamics/index.htm

There are many articles there that might be of interest, there are several books written by Czeslaw Marchaj.
en.wikipedia.org/wiki/Czes%C5%82aw_Marchaj

so is what your asking what shape/size should my sail be in class X for some particular windstrength for a particular surface type given my body weight is Z with a centre of body mass at my belly button( whichever side it has flopped to) and I am running a.oo x b wheels with hookworm tyres...............
basically we could discuss it at length but youll need to supply a few parameters for those of us who have been studying at length . we are certainly well beyond chopped up windsurfer sails at this point

US772 said...
Just trying to figure out if some twist is desirable for land sailing like it is for water sailing

now i see what your asking. before we look at boffin pics what we need to consider is
class
bodyweight and centre of mass
surface type
surface condition
wind strength
wind direction for the particular location( why did we want more sail area in 25knts in rada Tilly?)
wheel and tyre combination.
why not give us a set of parameters for what you sail on and your personal configuration and we can go from there

kiwi307 said...
Simple answer, yes we did quite a bit of study in the early 80s relating to landyachts, along with the Auckland university windtunnel (who designed much of the rigs with Tom Schnakenberg).
I no longer have the figures, but it was quite clear that for landyachts, even with a 5 meter mast there is some consideration should be given.
Controlling the twist is something else again with a soft rig, and the big heads as used on windsurfers IMHO give too much for the speeds landyachts achieve. Likewise the simple triangles as many US yachts used to use don't give enough.
I do have some data and non tech discussions from Cogito the C Class cat which are interesting, but I do not think over relevant.

The more I've dug into this the more I think your right about being very relevant at higher speeds.