| Re: unirig pointing ability
[Re: denis 18 square]
#188417 08/19/09 11:40 AM 08/19/09 11:40 AM |
Joined: Nov 2005 Posts: 1,203 uk TEAMVMG
veteran
|
veteran
Joined: Nov 2005
Posts: 1,203 uk | Generally, pointing is all about leach tension.
Paul
teamvmg.weebly.com
| | | Re: unirig pointing ability
[Re: denis 18 square]
#188532 08/20/09 01:18 PM 08/20/09 01:18 PM |
Joined: May 2003 Posts: 4,451 West coast of Norway Rolf_Nilsen
Carpal Tunnel
|
Carpal Tunnel
Joined: May 2003
Posts: 4,451 West coast of Norway | Denis, what windrange do you define as light? I say that 0-3m/s is light and go flat in that range. You will probably experience that the telltales will more or less demand a flatter sail in that range becouse the wind separates from the sail easier. This is even with some chop. The reasoning is that even if it takes longer to accelerate with a flat mainsail, there is just no more energy to get from the wind even with a main with more draft. Does that make sense? In more wind and chop I want more draft, becouse then I need more power and can use it to accelerate faster after busting through chop. In more wind and flat water, the sail have more draft after manouvering and while accelerating, but is flattened for more speed after a while (changing gears) In light winds I ignore the lower telltales. It is the top telltales where the wind is strongest and possibly skewed to the surface level wind I sail in. By your description of the telltales I would hazard to guess that you have too much draft in the sail up there. I have no experience with the sail/mast combination! I would try more pre-bend, more downhaul and more sheet until the telltales are streaming (leech telltales acting up/indicating separation 50% of the time) If I am wrong, I hope the gurus will let us both know. | | | Re: unirig pointing ability
[Re: denis 18 square]
#188548 08/20/09 02:39 PM 08/20/09 02:39 PM |
Joined: May 2003 Posts: 4,451 West coast of Norway Rolf_Nilsen
Carpal Tunnel
|
Carpal Tunnel
Joined: May 2003
Posts: 4,451 West coast of Norway | I would try more downhaul as a 'first easy fix' to see if I was able to get both leeward and windward telltales to stream properly when the leech telltales break 50% of the time. If you get better speed and pointing that way, I would start changing my mast setup to make it match the luff curve. If the sail was made for you, the sailmaker can probably help you with some figures to get you into the ballpark for spreader rake and tension. E/P sails are good guys from what I know about them. I never liked the tension meters/gauges. I always measure spreader rake by releasing tension before putting a batten from tip to tip on the spreaders. Measure distance to the luff track. Then tension the spreader wires and tie off the halyard to the boom. Measure the distance from the (now tied on tight) halyard to the mast track at the spreaders. This is your spreader rake and pre-bend when done the old fashioned way. The way you described on hoisting the main outside the track and comparing curves is good. The real proof is when you go sailing though. The flatter sail will get you better airflow over the sail and more leech tension. It should result in better pointing and speed. Please keep us posted and study those telltales. They tell us all we need to know to get the setup right, but it takes some brainwork now Rolf I need some clarification when you say the telltales demand a flatter sail; Is this means top telltales streaming aft and leech telltale 50% of the time acting up? I am not certain if I understand the question. What you just wrote above is the ideal trim for max power for least drag. What you wrote earlier was that the top windward telltale lifted and the leech telltales stalled (separation in front of the leech). The latter description sounds like there is too much draft in the sail for the windspeed. Perhaps I can answer more fully if you try rephrasing your question. | | |
|
0 registered members (),
201
guests, and 92
spiders. | Key: Admin,
Global Mod,
Mod | | Forums26 Topics22,405 Posts267,056 Members8,150 | Most Online2,167 Dec 19th, 2022 | | |