I've been trawling around for a definitive answer and so far they're all slightly different. I use them a lot on the Seagull MC2 and find them very useful. I've seen percentages, measured distances, one above the other on different sides (which is correct), even different luff placements. Help.
Cheers Col
On my water + land yachts previously I used to have the tell tails about 1/3 back from the luff but having a look at a couple of books tonight, I probably had them to far back.
We know that the 1/3 approx from the luff is about the max draft point and where the optimum shape should be so the airflow needs to be at its best at this point so from what I have read the tell tales should be froward of this 1/3 point, some of the figures quoted are 15-25% of the chord length (width) of the sail.
The number of tell tails should be minimum of upper, middle, and lower, but for very tall sails maybe an extra one or two.
Wool tufts on land yachts work fine as they don't get wet like on water yachts.
Sometimes you will see the tails higher on one side than the other its comes down the personal choice.
try 25% of the chord length back , 4 telltales up the sail and also 3 on the trailing edge. that should be plenty
I want them on to tell me when I'm about to stall. They tell you when the flow over the sail has parted company with the leech so you're not getting as much out of the available wind as you could do.
Cheers Col
(Cue an expert who can explain more and better).
I guess I should have been more specific. I'm asking about the trailing edge ones. What should they look like when things are good, and what do they do when something's wrong? And what would the wrong thing be ??
often you will see people trying to get sailing in a landyacht downwind and they are baffled as to why the yacht wont take off,particularly in lighter winds.
if theyhad telltales on the leach they would see them pointing in the same direction as they are trying to sail
.when you see that you need to swing away from downwind till the telltales start to flow,then slowly start sheeting in . if the telltales start to reverse you know you have oversheeted.
AND dont forget to look where you are going at the same time
Cheers Guys..job done! Sail is now complete (that's sail No 1, another 2 to go but less urgency).
Cheers Col
