Third attempt

The leech is a bit scalloped. Do you think it could have done with a bit more leech tension??

Don't have anything to contribute to the OP but I am looking forward to reading this thread - great idea for a topic.

I reckon you're slightly over sheeted, I'd ease the main sheet a bit, all the leach telltales are flowing to leeward, just till the luff flutters, and trim in again slightly
Get the crew on the rail to practice calling the lulls and gusts
The leech line only needs to be tight enough to stop the leech fluttering, otherwise it will curl and only create drag
Good topic !

I reckon the trim is not too bad. I'm just jealous of the racing numbers!

All,

thanks for the feedback.

Photos above show the foot, and the reefing arrangement. Single line reef, nice and easy, works for me.

A couple of comments / questions.

I will look at leach tension next sail.

re the vang. with the gusty conditions I actually wanted the head of the sail to twist downwind a bit, to depower. I would have thought that the tell tail backed behind (downwind) of the sail would indicate that the head of the sail is to tight, so ease the vang further. Pekeri, any further thoughts?

re putting the crew on the rail. I could try, but suspect that she would tell me where to shove the rail! For me a relaxing sail is autopilot on, and play with sail trim. For her it is sit, relax and think about life.

re the racing numbers. Came with the boat, out of registration, but I like them too.

Better view of he sail now. The top seems to be fairly full, and the drop off will depower the sail a little.

Sticking to one thing at a time is probably the best way forward here, so I will concentrate on the vang. (remember there are many variables. hopefully we will cover these one at a time.)

The Vang is a very important system for achieving good sail trim. Cant quite see the purchase of your vang but is should be somewhere around 16:1 or more.

Therefore the loads are very high and in order to use the vang correctly it must be worked together with the main sheet. Ie. to tighten the vang pull in the main sheet hard and immediately set the vang. While pulling in on the main check the flow across the sail this then dictates how tight to set the vang (generally tighter than you think). Then release the main sheet to set the main at just the point of luffing. If you have tell tales about 1 to 2 feet from the luff the ideal set is to have these flutter upwards slightly. Very hard to do properly and in some cases impossible to maintain while sailing. but an excellent indication that the main is working well.

Position of tell tales, mast bend, sail fullness, roach, relationship of Main and jib can be discussed as this thread progresses.

Can I recommend taking a photo from under the boom looking up?

More like this


As for what i can tell in the pics, I don't think the vang is too tight but the top battern tension may be a little too tight as the rest of the batterns and the leech looks ok.

rumblefish said..
Can I recommend taking a photo from under the boom looking up?

More like this


As for what i can tell in the pics, I don't think the vang is too tight but the top battern tension may be a little too tight as the rest of the batterns and the leech looks ok.

North 3DL sails have a "camera" point indicated on the foot and an app that will analyse sailshape.
WRT of the original poster you probably have to take a few steps back and look at the fundamentals of your boat, sailplan and sailing leg.
The Cav 37 is an older style (heavy) boat with a masthead rig with large headsails supported on a solid mast.
Upwind the boat will be headsail driven, trim the headsail with car position set fore and aft to achieve an even break in all telltales, then trim main to suit with upper ribbons flowing with constant adjustment. When the wind exceeds the range of an unfurled headsail you have a catch 22 as reducing the area by furling will balloon out the sail increasing drag, pointing ability and dropping boatspeed.
Reaching unless in very light conditions, probably better to furl the headsail to 100% overlap (preventing a massive twist in sail and the aft part of the foot from being grossly oversheeted. Then use full main and try to get a mainsail driven sailplan. Will be easier to trim the main without the distorted airflow created by the oversheeted/twisted overlapping headsail.
Downwind pole out the full size overlapping headsail. Area equals speed.

LMY said..
I am going to need to go for a sail, and play with the vang, 4:1 purchase by the way.

I will take a photo and re post. Work calls so this might take a while.

In in the mean time, anyone else want to post a photo for discussion? Sailing a reach in gusty conditions is for me challenging and I sometimes struggle to get the boat to "sit in the groove". I now have a idea to try sometimg different, so why not give posting a photo a try.

Reaching in gusty winds I would be more inclined to twist off the main. You will have more than ample power and traveling at hull speed. No point in keeping a tight leech , it's only going to heel the boat more and make the steering difficult.

[EDIT: I remember someone suggested one topic at a time so feel free to ignore until the current topic is well-cooked. Not an urgent issue.]

I have a basic question: where to position my tell tales. Would you agree with the following?

This source [www.jasperandbailey.com/tech/news.html ] states as follows:

headsail

- starboard side of the sail, about one foot aft from the luff, at 1/4,1/2 and 3/4 height increments. port side six inches below each one on the starboard side.
- none at the leech apparently

mainsail,
- one telltale right on the leech at each batten pocket or at 1/4, 1/2 and 3/4.
-You should also install telltale sets in the middle of the mainsail (halfway between the luff and leech) at 1/2 and 3/4 heights.

This source [ http://cdn2.hubspot.net/hub/209338/news/95_11_Tellingtales/Tellingtales.html], which seems much more detailed, states:

Main:
"In the mainsail telltales are only needed in the leech."
- 2-4 tell tales. If three at 1/4, 1/2, and 3/4 points

Jib/Genoa:
- 2-4 in the leech also at 1/4, 1/2, and 3/4 points
- 1 set nearer the head of the sail (not stated exactly where)
- 2 sets of 'steering tell tales' 1-2.5 metres from the tack, at a distance from the luff of 7 to 15% of the width of the sail at that point.

Regarding the 2 sets of steering telltales, he states, "One set should be installed a bit higher and closer to the luff than the other. The telltales further away from the luff are more forgiving and you should steer according to them in rough seas and in heavy winds. The telltales closer to the luff are more sensitive and you should use them in smooth seas and lighter conditions." Also useful in case one is obscured or stuck.


So the first source differs by having two additional pairs in the middle of the main and another half way up the luff of the foresail and none on the leach of the headsail.

I'm a newbie to sail trim so it probably doesn't matter much, but if I'm going to put them on they may as well be in the right places.

Any expert opinions?

i,m no expert .. but for what its worth my head-sail doesn't have them on on the leach . so much like the first set up.....

its a new main , so as built . ............but old heady ....so not sure on that . but thinking about it now , ive never seen them on the leach of a head-sail

Leech telltales on a main but also telltales mid draft, just the lower section so that you get an idea what is happening reaching.

Remember that tell tales are only worth having when the sail is set correctly, especially luff tension. Tell tails streaming is not always the best either, there will be occasions when the windward side stays vertical on a headsail upwind!

Keeping in mind this is sail setting 101. Nothing fancy and trying to maintain the KISS principle. (Repeat, repeat repeat until it's second nature)

We now have the jib lead/car block set at a know position.

2. Basic trim of the jib.
Assuming tell tales in place as per previous posts (easier if they are but not critical as yet.)

Go for a sail and raise/unfurl the jib so that the small crease along the luff is formed.
Point the boat in a tight reach.
Now tighten the jib sheets and look up at the top third of the jib leech.
Tighten the sheet until that part of the jib stops fluttering.
Now change your attention to the lower luff tell tale or front of jib
Slowly continue to tighten the sheet until the tell tale flow or in the absence of a tell tale until the vertical luff crease disappears.
Now If there is a tell tale tighten up a little bit more until the tell tale flutters up but the luff still holds its shape - no back winding.

You now have the optimum position and set for that point of sail and conditions.

LMY said..
lets try and improve all our sailing skills.

The attached photo is my main, with one reef in.

The wind was around 10 to 12 knots when the photo was taken, and on the beam. Boat speed in the high 6's. We were out for a relaxing sail, certainly not racing.

The wind was gusty, up to 20 knot gusts, so I had the halyard tension high to flatten the sail and keep things under control in the gusts. There are small vertical creases in the sail, so possibly to much tension?

Note that there is a tell tail at the top battery, behind the sail, so I could ease the main sheet a bit.

So, please provide your opinions, or if you want to learn from others post pictures of your sails and others may be able to help.

If you think that you have the art of trimming perfected, then post your pictures, and why you have set as is and we can all learn.

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Great idea!
excellent responses
for novices,like myself,the RYA "Sail Trim" handbook ,by rob Gibson is v useful
good balance of theory,with clear diagrams
my tuppence worth