Angle of mainsail top batten

[srah1953]

Hi all
I've read in various articles about mainsail trim that the top batten should be parallel to the boom. I've never understood whether this means that the batten should be in the same vertical plane as the boom or whether it means that the batten has to be in the same horizontal plane as the boom but could also be to leeward of the boom. I hope I've explained what I'm trying to say and that my use of the word “plane” is used correctly.
Thanks

 

[Keen_Ed]

When you sight from below the boom looking up, the aft bit (depending on length) of the top batten should line up (..ish, depending) with the boom.

http://www.northsails.com/uk/SailBetter/MainsailTrim/SetTwist/tabid/7033/Default.aspx

 

[macd]

+1
apart from anything else, to check whether they were parallel horizontally, you'd probably need to get in the tender

 

[srah1953]

Many thanks for this. I understood that, because of the differing wind conditions on high, there should be a degree of twist in the mainsail to allow for this. If the top batten is parallel to the boom and in the same vertical plane as the boom, surely that means there is no twist in the sail?

 

[[2574]]

Many thanks for this. I understood that, because of the differing wind conditions on high, there should be a degree of twist in the mainsail to allow for this. If the top batten is parallel to the boom and in the same vertical plane as the boom, surely that means there is no twist in the sail?

I'm with you on this question. I've never understood it either. To get the top tell tale flying I need to induce twist in to the sail with the top of the sail "falling off" to leeward and therefore never parallel with the boom. Thanks for asking the question.

Rob

 

[dunedin]

Actually if there were no twist in the sail (eg flat calm and full kicker tension on) the sail cloth would go in a straight line from the top of the sail to the end of the boom - which would mean the curve of the back of the sail (the leach) is to windward of the boom. Hence the batten front end wold be to leeward and the batten end to windward - not parallel and what is referred to as a "hooked leach".
Easing the kicker and a bit of wind should allow a little bit of twist - and magically if get the right tension the batten flies parallel to the boom but a short distance to leeward.
Difficult to explain in words, but easy to observe in practice if you look up the back of the sail as somebody adjusts the kicker or main sheet tension when close hauled

 

[lpdsn]

Easier to use tell tales on the leech. If they're all flying and the top one is stalled you need more twist.

 

[dave_gibsea]

A top racer and sail-maker once told me to aim to get the top batten tell-tale flying off about 50% of the time with the other tell-tales flying all the time. If you don't have enough leech tension then your boat won't point. Use more twist if the sea is lumpy, less in flat water. Also, the outhaul should be eased in lumpy sea and pulled on hard in a flat sea

 

[Clive]

It is usually the back third you should be looking at. When sailing up wind in light / med breeze ie full power, the back third should be parrell to the bottom third of the mainsail. as the wind increases or the waves gets bigger you should allow the mainsail to twist, depowering or matching the wind shere.

The simple way to know if you have got it right is to have some tail-tails on the leech either side of the top batten, these should fly about 80% of the time, so keep adding leech tention until the top stalls out about 20% of the time or until you are over powered

If you are over powered, I find it faster to allow twist at the top of the mainsail but keet the boom on or near the centre line of the boat, to do this, ease the main sheet, no kicker and pull the traveller to windward. don't forget to move the jib cars back to allow the jib to twist as well. As I have been in the 10% of the ISC class in the RTI for the last 3 years we must be doing some thing right.

 

[flaming]

Entire, rather thick, books have been written about trim. So to simplify it to "get the top batten parallel" is a little, well, simple!

What I think is more helpful would be to say "never pull the sheet on so hard that the top batten is past parallel". There are occasions where you want the top of the sail falling off to leeward, but you never, ever want the top of the sail to be hooking to windward.

That said, there are some funny trim quirks in some classes, and the usual rules don't apply. With the old first class 8s that the RYA used to have for match racing for example it was found that to be super quick upwind in moderate breeze you pulled the car all the way to the top so that the bottom 1/3 of the main was over the center line. Shouldn't work, but did!