Arwen's meanderings

Hi everyone and welcome to my new blog. My name is Steve and i am the lucky owner of a John Welsford designed 'navigator' named Arwen. I built her over three years with the help of my father, father-in-law and two children. She was launched in August 2007 at Queen Anne's battery marina in the barbican area of Plymouth. This blog is a record of our voyages together around SW England.
Arwen has a YouTube channel of her own. Search "plymouthwelshboy".

Sunday, 23 August 2015

Using your sail's tell tales!

Tell tails are somewhat absent on Arwen. I've decided I need some and I need to position them correctly. So for the last few days I have read around a couple of articles and this is a summary of what I have gleaned thus far.

My aim by the way, is to try and improve my genuinely appalling sail trimming knowledge and technique!!

So a summary thus far, which of course, as normally is the case, I have no idea whether its useful and  accurate or not. The problem with being a newbie sailor is you have nothing to fall back on in terms of experience when dealing with new things and so cannot determine whether what you are reading is genuinely useful or not. I guess you just have to go out there and try it!

I like experimenting anyway!!

So, a summary, thus far

  • tell tales show airflow over the sail surface.
  • when the sail luff passes through the wind, the wind velocity at the sail's surface decreases due to friction with the sail and this is called 'the boundary layer'
  • correctly trimmed, the boundary layer stays intact and the tell tales stream aft, parallel to each other, on either side of the sail
  • if the velocity of the boundary layer decreases and separates from the sail, it results in more loss of speed and power
  • too close to the wind or under trimmed - the boundary layer slows on the windward side and the tell tale lifts
  • too far off the wind or over trimmed and the opposite happens - with the tell tale on the leeward side of sail lifting or stalling along with a consequence loss of power
That seems to be the basic theory - I think!

It seems that getting the leeward sail tell tale streaming is the most important thing to do and this follows the basic maxim "if in doubt - let it out"! Doing this encourages more airflow over the outside leeward side of the sail and thus reduces loss of power/velocity.

Another maxim I read was "inside drops, pull in - outside drops, let out" which I think is based on the premise that if the inside, i.e. windward tell tale stalls or drops, pull in the sail and/or bear away; and if the windward, i.e. leeward outside tell tale drops or stalls, ease out sail and/or luff up towards the wind.

Has anyone else found that as they get older, retaining this stuff in their head.....becomes harder? Maybe it is just me then!

I found these videos helpful:

so, where to position new tell tales on Arwen? Ah well, that seems a little harder. The advice seems to be

  • on the jib - two sets - each 30cm approx. back from the luff
  • on the mainsail - one set 50 cm back from the luff and approximately 60cm up from foot of sail. here it is at optimum position for glancing up to, without losing the gaze on the water in front
  • and using 15 cm pieces of fine wool; although jury appeared out on that one - some arguing wool when wet stuck to sails; others favouring thin strips of sail cloth, which doesn't

and what about leech tell tales I hear you ask? Just when I thought it couldn't get more complicated......

  • mount three sets on the mainsail, where the battens are
  • around 20 cm long wool strips
and how do you use them?
I'm glad you asked! It would appear that leech tell tales are used as follows:

  • to gauge the degree of twist in the leech of the sail and how it affects wind flow across sail surfaces
  • want to have all of them streaming straight back for about half the time. Over half the time indicates too much air flowing over sail freely and therefore losing lots of its power, so trim the mainsail. Under half the time - need to loosen the leech and ease the sheet

Ah Ha! Well that was as clear as mud to me; and do leech tell tales really matter on Arwen anyway. Probably not!

If I have got any of this wrong, do let me know via the comment box below



robert.ditterich said...

Nice to have to think this through. I've always taken them for granted, just being there. I'm with you though, about remembering things- it does get harder.

steve said...

Ach Robert, it is getting bad
I struggle to remember children's names, names of my colleagues. I frequently lose the car in park parks. I can't retain all the knowledge I need to teach on a daily basis any more. And never ask me to recount what I did last week............can't remember what I did yesterday! But I'm well, a cheerful soul and married to extraordinarily wonderful tolerant woman; two fantastic kids and amazing friends and work colleagues.......they all put up with me, tease me nicely and adapt around me
It's clearly an age thing!


robert.ditterich said...

Yes mate, there are plenty of positives and you are patently aware of them!

Ayen said...


I found your blog while pondering telltales for my Chebacco 25, a bigger boat but one with a lot of common themes with the Navigator - a glued clinker lug yawl.

My conclusions have been that leach telltales on the main are the way to go. (I think I will put leach telltales on the mizzen while I am at it.) After reading lots, I tried sellotaped cassette tape on the mainsail leach of an old Mirror last weekend and was surprised at how poor my "feel" for sail trim often was. That experiment convinced me that I was kidding myself that I could do without them. Luff telltales work better on a jib.

What did you end up doing?


steve said...

Hi Andrew

Haven't got anywhere near tell tales. OFSTED has just got in the way again. Will look at it all I two weeks time at half term
Stay in touch