^^^^ That sounds about right nebs.
Off topic:- Could you please check your PMs or go to the sailing forum and read the "Cruising Forum" thread. Cheers Cisco.
I have to agree with Nikrum. He was asking a question and Kiwi 307 got his nose bent out of shape.
Kiwi 307- 0
Nikrum -1
At the top of the page under help there is a forum crash course that talks about misunderstandings etc
The written word can often be misinterpreted as it lacks the
facial expressions gestures and so on that are also part of communication
Any one who uses skype will know this
I believe that that is all this is
We have had it before and moved on We can do it again
It seems to me that people from across the Globe have a better understanding of Aussie Vernacular, colloquialisms, Slang etc. than our favored neighboring Sparing partners do. Aus' and NZ being so remote from the rest of the Anglicized Global population, until recent years, should have a greater affinity for each other than for a simple misguided assumption to cause a War of words as this.
Anyway, "WTF" I'm over it. We can't all agree with each other all of the time. It is part of the human condition and what adds a little Spice to Life.
Thanks Sabydent, obviously you enjoy my Banter.. All it takes is a Thick Hide and an Evil Snese of Humor..
Ron
PS; It is nice to understand what is being discussed, even if you are unlikely to use it.
The balance of CE, CG, CR is a VERY variable thing and constantly changes during sailing.
CE, [Center of Effort] the paper model is an interesting way of creating a theoretical point but it doesn't take into account the 3 dimensional shape of a sail, the real life CE point can be moved forward or back by down haul pressure, batten tension, sail out haul and sail sheeting angle as nebbian mentioned. Most wings and that's what a sail is, the maximum lift point is approx 1/3 from the leading edge... so the longer the leading edge the more lift, ever wonder why gliders have long thin wings compared to powered planes? and souring birds have longer wings (Eagles, Albatross and even Seagulls)
Mast rake also effects CE, it will go up and down with sail trim where as a straight up mast the CE would tend to be more consistent like a stayed mast water yacht.
CG, [Centre of Gravity] depends on the yacht construction I have found it on smaller yachts to be about in line with the front on the rear wheels BUT this will vary with the size, weight and proportion of the pilot.
CR, [Centre of Resistance] will depend on tyre size, inflation pressure, tread pattern of all 3 tyres. New tyres v worn out tyres and also the surface will effect CR.
The other often forgotten thing is the surface you sail on, asphalt and salt have very little side slip, sand will vary from beach to beach wet or dry, mud and wet grass are a different ball game again.
There are SO MANY variables when it comes to CE,CG,CR
More info on wings....
en.wikipedia.org/wiki/Aspect_ratio(wing)
en.wikipedia.org/wiki/Bird_flight
CG and CR would be very closely related and do move slightly forward when a yacht goes up on 2 wheels as the rotational axis line is front wheel to back wheel and not the centre line of the yacht.
The main problems occur when CE and CR/CG get way out of whack, to far back and the rear wheels break away side ways, to far forward and its hard to steer. And as I have said before it will very much depend on the surface your sailing on. IE. if you sail on grass or a slightly muddy surface you may want the rig further forward [move CE forward] to minimise the back end breaking away. On salt you may want CE back further with the extra grip from the salt.
Yachts evolve differently depending on the location they sail, many years ago the Perth yachts had lower aspect ratio rigs and much wider seats due to the prevailing wind conditions at their club than the Lefroy yachts.
Just as sailboards are different for flat water to surf and strong winds to light.
Just to complicate this subject further.... The way the Y frame yachts heel over is different than the T frame yachts. The Y frame does tend to heel over parallel to the center line of the frame, as it also leans back as it heels over.
It's FAR from an exact science... compared to F1 race cars for example.
And maybe thats half the fun of land sailing.
Interesting...
So if you felt the back starting to break away you could scoot your body weight back a bit which would then make the CR move back as well?
Cool
Your are probably right Paul, people do get confused when I start asking questions or the methods of doing so.
It is just that Under the new Sail and the conditions I have used it, it seems to me there is more torque on the Rear Wheels than with the Pryde Re-Cut. I will have to reconfirm that though but there is a total difference in how that new sail works compared to the others. So it would seem to me that this really is conjecture unless a Rolling Chassis and Sail are a Bespoke thing or constructed similar to Desertyanks Red Thing, (Long Mast Step)
That incident seemed to me like that bloke didn't like being questioned. Ain't none of us make things clear to all people, That is the way things are and we should never get our noses out of joint over being questioned or misunderstood. If that is going to be the reaction or behavior then give up trying to teach. Damn! Just imagine if Tassiefubar got that way. His students wouldn't have any respect for him and there would be no Landyachts in that school, let alone any other of their projects.
Ron
PS; You yourself have said to go ahead and ask questions even if they seem silly. There are only questions none are silly, that is a quantity that is relevant to some parties, not all
Ron, can you take a picture of the 2 sails you are refering to, one over lapping the other so we can compare the mast curves. And we will see if we can work out why they are so different in performance.
Hey Nikrum:
I agree with Gizmo, it would be very instructive if you could take a photo of the yacht rigged up the sail that worked, and again with the sail that didn't work, so we can compare the centre of effort of both sails and see if we can figure out an easy way to tune for the second sail. You may already have these photos...
If we can figure out the centre of effort of both sails, when rigged up, then it would be really cool to verify that the calculations line up with actual real world results
Here are the pictures I found:
Judging by this they don't look that different in the CE department...
Can you remember how much belly the new sail had? Also do you think it could have something to do with the different pulley arrangement?
Good Morning Nebian,
As near as I can make out , the mast curves are pretty much the same. I am thinking that the effect comes in most likely with the amount of sail along the trailing edge that is near or behind the Rear Axles even though the Sail Foot is shorter. With the Pryde Cut the majority of the trailing edge is low down and I think in slower moving Air whereas the converse is true of the Gastra Re-Cut. Both Sails shape nicely under preasure even though I've not had a constant strong wind to trial the Gasttra. Up shot; My feeling is the Sail Shape is throwing the Center of Effort further towards the Rear of OR. I know that sounds all wrong but that is my feeling at the moment. Further info when I can run more trials. Another thing is it seems to point Higher into the Wind on the Strip, Tarmac Surface.
Ron
I just had a little Play In Corel Photo Paint. Pic's you asked for.
Thanks for that Nikrum
Does the pic with the gaastra show the front pulley as hauled in as it can go? Because it looks like it needs at least another 5 cm of downhaul... This would definitely affect handling. You may be able to make a 5 cm mast tip extension which would do the same thing.
Nebian,
I already have an extension in there but can adjust it without too much trouble..
What effect do you think that will have??
Ron
More downhaul will stop the centre of effort wandering around like a lost sheep, which is, I imagine, what you could feel when you took it for a spin.
The sail is designed to set in a particular way, and if it's set up in a different way then it won't work nearly as well.