Upwind Mainsail Trim: Shaping Your Sail, Part 4 - Controlling Twist

[@mdteason]

Thank you very much for the excellent guidance, which we think will help us race and cruise better! One very minor but fun point on weather- in the sixth minute, this video incorrectly suggests that global Coriolis effects consistently veer or back masttop wind direction. That effect is insignificantly small at the scale of a boat and its mast, or a bathtub drain, contrary to popular belief. Local obstacles, or squalls swirling either direction, cause any actual shifts in true wind layers. Of course, you correctly stated the typical apparent wind shift factors.

[@SailZing]

I believe you to be absolutely correct that the global forces are overstated. I’ll put a note. Thanks! Glad that the videos are helpful.

[@mattt945]

I'm learning a lot about sailing from your videos. That being said, even though this is a common belief, the motion of the earth does not cause the whirlpool in a drain. Just thought I would point that out to you. Thanks again though for the informative and well made lessons about sailing.

[@bugstream]

This is an excellent video :) It makes clear what options are there for a range of conditions. Well done, thank you!

[@emmeranm9654]

This is what i was searching for for the last ten years or so!

[@SailZing]

Thanks for the feedback!

[@mytube001]

It's in 480p, so you can pretend it's 10 years ago! ;) It's a great video though!

[@ΛάμπηςΓιαννούλης-ω7λ]

Very useful thanks

[@mrkoopsy]

In light airs and with a fully battened sail with large roach, how do you reduce hooking of the leech if the vang should be left loose to achieve twist? I’m wondering how best to play the vang versus the mainsheet in the light conditions.

[@jameslittlewood7663]

Trimming a 38 ft light weight, short keel yacht, vang-sheeting seems most critical form cracked sheets to beam reach, with depower cycle in the order of vang, then traveller, then sheet (and vice versa to power back on).

[@SailZing]

Thanks for the comment. In our overpowered MC Scows, we use vang first as well. We also pull cunningham. Then drop traveler. We also vang sheet in the gusts, but we try to maintain as much sheet tension as possible to keep the sail flat. If we have to drop more traveler to do so, we will. In waves, we will crack off a little.

[@samstenson4920]

Hi. These are great videos. Very new to sailing, but learning quickly with the help of these. Sailing on an Elliot 7.9 at the moment. Do you have any videos on Jib trim?

[@SailZing]

Thanks for the feedback. We plan to finish the mainsail trim series with a few more installments. Then we'll look at jib trim. I have a lot to learn about jib trim!

[@samstenson4920]

@@SailZing hello! Are you still planning on releasing a jib trim video?

[@SailZing]

Yes, but timing is uncertain.

[@martyhownice2441]

”Leech telltales streaming intermittently”. Does that mean they are just about to stall or just about to luff? I mean do we seek maximum lift or maximum lift/drag ratio here?

[@SailZing]

Thanks for the question and sorry for the slow response. We're talking about the leech ribbons here. I don't think of this as stalling or luffing. They're responding to the vortices that get generated when the air moving over the windward side of the sail meets the air from the leeward side at the leech. in light to medium air, the ribbons will disappear behind the sail and then stream intermittently. If you're not pointing well in light to medium air and your leech ribbons are always flowing, try trimming the mainsheet a few clicks. In heavier air the ribbons might always stream.

[@mboyer68]

Hello, thank you for the great videos! When you mentioned Cunningham, were you referring to downhaul? Thank you:)

[@SailZing]

Thanks for your question. The cunningham is a line that tensions the luff of the sail by pulling down on a grommet just above the tack of the sail. A downhaul usually refers to a line that pulls the entire spar down. A downhaul on the boom would have a similar effect to a cunningham.

[@sandynicholson6516]

Downhall refers to the line attached to a bridle centred at the bottom of the spinnaker pole, when this downhall control is located at the outboard end of the pole it is called the foreguy

[@johnmcdonald284]

@@sandynicholson6516 On most small catamarans like @SailZing said the downhaul is a purchase that pulls down the whole boom causing a similar affect to the traditional cunningham

[@BackVintageWines]

No mention of using the backstay to help manage twist?

[@SailZing]

Thanks for the comment. I've often wished for a backstay, but the dinghies and small boats we are targeting in our content don't have them. Maybe someday ...

[@BackVintageWines]

@@SailZing a FarEast 28r is just a big dinghy ! Really like the effort and thought you have put into this series. Well done.

[@bigglyguy8429]

Bit confused... at 3:30 you say the angle of attack will be 'smaller' (?) at the top of the sail. Is that because it IS twisted, or because it IS'N'T, and so needs twisting? Or would twisting make it worse? And I'm afraid no, I cannot see the twist very well with the diagram, as I'm not sure what I'm looking at... then you say a twisted sail will have LESS camber? So it's more twisted when it's flatter? I'm just totally confused now

[@SailZing]

Yes, it's flatter when more twisted. But, a sail can be flat without being twisted - think of a heavy air sail. With a fuller sail, it's a little hard to picture. Think of it this way: As the upper sail leech twists off, the sail becomes flatter over the entire chord length. Just picture taking a curved sail and pulling the leech to leeward. A flatter sail is gong to have a small angle of attack at the luff of the sail. It's hard to see from my drawing. This depowers the top of the sail.

[@bigglyguy8429]

@@SailZing Thanks for the reply. I think I need to go back to basics...