fprintf

Sail trimming workflow to memorize before the season?

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I've been trying to understand all the moving parts of the trimming of sails on the fractionally rigged sloop rig that I sail on (Atlantic Class). I've been watching videos all winter and was thinking I should be able to create or find a workflow that will help with decision-making at my end of the boat (jib trimmer, and halyard tension) in a series of If-then thoughts. 

Such as:

If the upper jib tell-tale is stalling before the lower two, ease the sheet a fraction if the boat is pointing well, otherwise check the halyard tension and position of the jib car. 

Otherwise how does one go about getting the complexities of pulling all these different strings and wires well ingrained besides years and years of trying different things? I can't honestly tell when the boat speeds up or slows down since my butt isn't that finely tuned nor are speed measuring devices allowed in the class. So I think I have to create a set of rules or guidelines for myself. 

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You our tryeng re-inventte the wheelle, dointe you halve morre experinenced peopel you cane talkle to?  Bounce ideales off of?  Tommey is goode with Atlantics, I forgette what name hese poesteng undere.....  I'lle see if I cane rouste hime.                    :)

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Atlantics are beautiful. I sailed on one, decades back, and pretty much wasn't allowed to touch anything important.

It would be interesting to develop a generalized trimming algorithm, but the specifics vary a LOT from boat to boat. One of the biggest differences is the effectiveness of the vang and what the backstays does... I tend to work the backstay too much for most frac rigs.

Rule of thumb for upwind, get the twist right and then use the traveler for incremental adjustments to trim. Increase twist -slightly- to depower, this is where a good trimmer makes his bones upwind. Invert the sail and you just hit the brakes, overpower the helmsman and you've not just hit the brakes but caused a major pissed-off cascade of bad vibes that will cause harm for the rest of the race.

Getting the twist right (which is really all about leech tension) is also the key to going fast downwind but uses different tools since the traveler is at the stop.

This is generic, if somebody with specific knowledge of how to make Atlantics go fast says different, do it their way!

FB- Doug

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Doug, you seem to be talking about mainsail trim.  I don't think vang will have much effect on the headsail and most 'travellers' i.e. barber haulers on jibs aren't powerful enough to be trimmed continuously and smoothly.

What about headsails?

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I think years and years of trying different things is the most accurate answer. At the end of the day it's an art not a science

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6 hours ago, Brass said:

Doug, you seem to be talking about mainsail trim.  I don't think vang will have much effect on the headsail and most 'travellers' i.e. barber haulers on jibs aren't powerful enough to be trimmed continuously and smoothly.

What about headsails?

Yes, the main. Thought that was long-winded enough. Also, the Atlantic has -really- big mainsail, old fashioned boat with a tiny jib. What i was getting at, sort of, is that sail trim is based on simple physics, getting the angle of attack right (and twist is matching AoA to the differing wind at the top of the mast); but is really situational. Are you trying to accelerate? Trying to point? Overpowered and dealing with waves/chop? Light air and trying to get air to flow? I don't know enough about it to put it all in good order, yet what I do know suggests that there is an underlying systematic approach.

 

10 hours ago, fprintf said:

I've been trying to understand all the moving parts of the trimming of sails on the fractionally rigged sloop rig that I sail on (Atlantic Class). I've been watching videos all winter and was thinking I should be able to create or find a workflow that will help with decision-making at my end of the boat (jib trimmer, and halyard tension) in a series of If-then thoughts. 

Such as:

If the upper jib tell-tale is stalling before the lower two, ease the sheet a fraction if the boat is pointing well, otherwise check the halyard tension and position of the jib car. 

Otherwise how does one go about getting the complexities of pulling all these different strings and wires well ingrained besides years and years of trying different things? I can't honestly tell when the boat speeds up or slows down since my butt isn't that finely tuned nor are speed measuring devices allowed in the class. So I think I have to create a set of rules or guidelines for myself. 

One way to develop a sense of boat speed is to sail little, zippy, tippy, boats. It's also fun.

One systematic way to look at it, you are observing two edges of the sail, luff & leech, and moving one corner to try and optimize airflow over those edges.

Luff tell-tales: best indicator of angle of attack. At the basic level, they tell you "ease or trim" and they are also guiding the helmsman, so communication with him is always good. But the helmsman doesn't know (and doesn't need to know) where your jib sheet is. Can you trim more, or are you all the way into "point' mode? What he does know, is the boat fast and are there waves/gusts/traffic ahead that will require something other than "keep the telltales flowing."

The specific thing mentioned, upper telltale stalling (inner or outer? I'm guessing inner) means that the angle of attack is to slight ie that part of the sail needs to move toward the boat's centerline. To fix that, you'd move the lead forward.

OTOH if the boat is fast and pointing well and we're not overpowered, I like to see the inner telltales flip/flopping a little bit. That tells me that the sail is still driving but is at (or close to) the tightest angle of attack it can get. You don't always want that, to accelerate for example you want them streaming and the leech telltales getting a little antsy.

One more jib thing- there should be some kind of indicator specific to your boat that tells you when the jib is right at it's best angle of attack for going close-hauled. Many boats have a stripe on the spreader which matches up to the leech telltale. Others have a line on the deck to match to the foot of the jib. Get familiar with whatever your boat uses and work out how your helmsman likes to communicate where the boat is in the cycle of "ease for speed, trim for point" etc. This is how the fast sailors consistently inch away from the rest.

Once you've got the angle of attack right (sheet) and dial it in for the whole sail (sheet lead fore/aft), then work on flow & power which will be your barber haulers and halyard tension. Deep bellied round sails (adjust with barber haul) are powerful but they don't point high. Sails with the deep part of their belly in the middle can point fairly high and still develop power but they break up flow easily (sometimes you can even fuck up the main this way), which is especially bad in chop, so you pull that belly forward with the halyard. Tighten halyard for power / build flow, ease for pointing. But don't fuck with any of that until you've got the sheet & leads right!

OK sorry, I did not intend to write a book here. There have been some great discussion of sail trim & dynamics here, by guys who really know it well and also know specific boat finesse too. Unfortunately I don't have any of those thread handy....

FB- Doug

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I don't think jib trim lends itself to an 'algorithmic' approach.

On an Atlantic, it looks like the jib trimmer is only concerned with the jib halyard tension, sheet and barber hauler.

You can sort of use sheet and halyard to shape the sail, then use barber hauler to adjust angle of attack, but you'll have to re-adjust sheet and barber hauler, because they interact.

As Doug has said you need to use spreader or sheet/deck marks to replicate the fully close hauled trim for light, medium and strong breeze

A good starting point would be the Class Trim Guide https://www.atlanticclass.org/images/pdf/Atlantic_Tuning_Guide_2010.pdf

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look up a fellow named Don Guillette who wrote a book called The Sail Trim Users Guide. It is very systemic and full of guidelines. You buy it direct from him and it is worth the money in my view. 

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