Genoa trim while on a broad reach.

[RichH]

I am struggling getting the correct trim on the genoa while on a broad reach. I have been sitting on the foredeck with the genoa sheet adjusting it and the car on the track as well as shifting halyard and backstay tension. It just doesn't look right. My bottom telltail is mostly pointing down. If let the sheet out too much the luff puffs forward past the forestay and the sail acts more like a kite. I am not sure how it should look.

On a broad reach on down to DDW, there will be little 'aerodynamic air flow' across the genoa, most of the 'drive' from the sail will be simply the maximum projected sail area that you can have at ~90° to the apparent wind ... when at a broad reach or lower (and the boat isnt planing with great speed) tell tales wont tell you 'much' as most of the 'flow' will be ' mostly stagnated' or essentially stopped by the air impacting directly onto the sail (stagnating).

What you're looking for when sailing deep downwind is SPEED, the maximum speed ... No matter how 'ridiculous' or not the sail 'looks' what is important is SPEED, so all adjustments made are made in reference to your SPEEDO or GPS.
All your trim 'adjustments' and 'tweaking' should be adjusted (as 'trials') first with the jib fairlead car (fore/aft ... usually more forward) to get as much of the sail @ ~90° to the apparent wind; and, then in/out on the jib sheets while watching your speedo/gps ... will tell you how much in/out. You adjust 'trim' to the maximum speed you can see on the speedo/gps ... and no matter how awful or good looking the shape of the genoa. Change course, do it all over again .... OR see if the tell tales are now showing you 'aerodynamic flow' and if so then use the tell-tales (and the speedo) to do your trimming.

Rx --- From a broad reach all the way down to a dead run ... trim according to what your speed / gps is telling you - trim (main then genoa then main and genoa, then 'tweak' again, etc. etc.) to get MAXIMUM speed on the SPEEDO/gps!

Addition: ... how to be sure the jib is at ~90° when the jib is all 'twisted' because you cant run the fairlead 'outside' the rail .... use a jockey pole, or reaching strut or use a spinnaker/whisker pole and push the clew outboard as far as it will go ... until the sail has little to no twist (and which is illegal in most racing venues, because it works so well in holding the clew 'out' and the sail quite untwisted).

 

[Joe]

That is a good explanation Joe, but I think that the J dimension is measured parallel to the water,

The J dimension has very little to do with the water.... It is based on a model that places the mast perpendicular to the deck....

while the LP is measured perpendicular to the headstay.

the LP is a SAIL dimension... not a boat dimension... it is measured from the sail's luff.... I know it sounds the same, but it's part of the sail, not the rigging. The J,I,P,E etc... are fixed physical dimensions of a boat, whereas LP, Luff, Foot, Leech are variable sail dimensions.

That means a 100% LP headsail will not quite be the same as the foretriangle. Things would be a lot simpler if the LP's of headsails were referenced to the LP of the foretriangle.

They can't, it's two different types of triangles... the foretriangle is a right triangle with the headstay being the hypoteneuse, the J (foredeck length) is the height connecting at 90 deg to the I (hoist, mast length from deck to headstay) which is the base. There is no need for a luff perpendicular to calculate its area. 1/2 x B x H.

The sail, however, can be any type of triangle... so... the luff becomes the base and the LP is drawn in to give us the height dimension to complete the area calculation.

That is why we express the sail size in terms of the relationship between J and LP.... they are both the height number of their respective triangles.

To make things a bit more confusing.... the length of the foot and leech have nothing to do with calculating sail area.... but they have everything to do with clew location and the amount of overlap.

 

[RichH]

They can't, it's two different types of triangles... the foretriangle is a right triangle with the headstay being the hypoteneuse, the J (foredeck length) is the height connecting at 90 deg to the I (hoist, mast length from deck to headstay) which is the base. There is no need for a luff perpendicular to calculate its area. 1/2 x B x H.

Not quite .... slight difference but not quite ....

1/2 B X H is for a 'right' triangle, or a triangle who has one internal angle at 90°.
With a high clew, there isnt a 90° internal angle. So in that case, you must use the LP dimension line.
The LP now defines TWO triangles within the 'triangular' (but not 'right' triangular) area of the sail, each of the two 'inner' triangles with 90° internal angles (at the headstay where the LP line meets the headstay) .. and you calculate each of the TWO 'right' triangles by 1/2 B X H ... and add the sum of their 2 areas to arrive at the combined total area of the sail.

This may be splitting hairs but a high clewed jib (a 'yankee') will not have the same area of a 'deck sweeper', even if they are cut to the same J dimension.

Rx to find total area: calculate or measure the LP dimension, which divides the sail into two 'right' triangles, calculate the area of each and then add the two areas.

 

[SailingHarry]

In answer to the original post, I completely agree with SailingHarry as far as lead adjustments, and I would add that you really want to ease the sheet out until the leeward telltales stream, and not worry too much about the windward telltales.

Sandy is right about the telltales. I'll add something to his adding something! Off the wind (beyond 90), the telltales often get really squirrely. You can do the same thing as the telltales visually. The telltales help you line up the first several inches of the luff to point straight into the wind. If you have a windex, burgee, or some other wind indication at the masthead, you can go stand in front of the head stay, sight up the sail, and have the sail adjusted until the first part of the sail lines up with the masthead wind indicator. Crude, but it can help.

Harry

 

[Joe]

Not quite .... slight difference but not quite ....

1/2 B X H is for a 'right' triangle, or a triangle who has one internal angle at 90°.
With a high clew, there isnt a 90° internal angle. So in that case, you must use the LP dimension line.
The LP now defines TWO triangles within the 'triangular' (but not 'right' triangular) area of the sail, each of the two 'inner' triangles with 90° internal angles (at the headstay where the LP line meets the headstay) .. and you calculate each of the TWO 'right' triangles by 1/2 B X H ... and add the sum of their 2 areas to arrive at the combined total area of the sail.

You of all people, Rich....

Give it a bit more thought, then you'll laugh out loud... the formula works for all triangles... the difference is the right triangle's height is one of its perpendicular sides... any other triangle it must be drawn in.

the formula is simple.... the height or LP of the sail's triangle is the same number for both of your right triangles....the base of both of your right triangles adds up to the total luff dimension... you don't calculate for two separate triangles.... then add them together, it works but it's the same as: 1/2 L x LP, or L x 1/2 LP, or 1/2(L x LP)..... your formula is redundant.

This may be splitting hairs but a high clewed jib (a 'yankee') will not have the same area of a 'deck sweeper', even if they are cut to the same J dimension.

Again, I ask you to re think the properties of a triangle.... A sail's area is calculated with luff and LP dimensions not foot or leech dimensions. If luff and LP remain constant, you can alter the foot and leech dimensions proportionately, thus moving the clew up or down without changing the sail area.

Look at Jackdaw's drawing for reference. Moving the LP up and down the Luff, changes the clew position but not the sum total length of the foot and leech.

Finally, the J is a rig measurement...... I'm not sure I understand how you're using it in the sail area context....did you mean LP?

 

[twistedline]

Thanks once again, I have lots of new information and will keep playing around.

I have one more question. The previous owner added an additional track way aft, both port and starboard. I have never used it, I am not sure why its there.

See red arrow.

I think I may have a headsail which is >155% could this be what this track is for?

Thanks

 

[shemandr]

The telltales help you line up the first several inches of the luff to point straight into the wind. If you have a windex, burgee, or some other wind indication at the masthead, you can go stand in front of the head stay, sight up the sail, and have the sail adjusted until the first part of the sail lines up with the masthead wind indicator. Crude, but it can help.Harry

Exactly.

 

[Jackdaw]

Thanks once again, I have lots of new information and will keep playing around.

I have one more question. The previous owner added an additional track way aft, both port and starboard. I have never used it, I am not sure why its there.

See red arrow.

I think I may have a headsail which is >155% could this be what this track is for?

Thanks

Yes. As a good starting point, a headsail sheets angle to the clew of the sail should project onward so it would have bisected the luff. This allows the sheet to apply equal tension to the foot as well as the leech. See below (blue lines).

The forward tracks would give a lead that would pulled hard on the leech but let the foot loose. The aft tracks solve that.

 

[Joe]

That's a very good drawng that we can all learn from.... the red lines are LP's.... the blue lines bisect the clew angle from the sail's luff midpoint. If you have trouble seeing it on the boat, you could actually draw an arrow right on the sail, at the clew, pointing to the mid point on the luff when you have the sail spread out on the ground.... then your starting lead block position would have the sheet lined up with the arrow....adjust from there depending on conditions or strategy.

 

[twistedline]

That's a very good drawng that we can all learn from.... the red lines are LP's.... the blue lines bisect the clew angle from the sail's luff midpoint. If you have trouble seeing it on the boat, you could actually draw an arrow right on the sail, at the clew, pointing to the mid point on the luff when you have the sail spread out on the ground.... then your starting lead block position would have the sheet lined up with the arrow....adjust from there depending on conditions or strategy.

It helps a lot. I am going to try and find some blocks for those aft tracks.

 

[SailingHarry]

I was just looking at the picture of those aft tracks, and realized that your toe rail is the aluminum type with holes in it. When you see that those tracks have a car on them, I as thinking you may want to get a pair of snatch blocks. That would allow you to use the tracks, AND to use the rail as a sheeting point when further off the wind.

Snatch blocks are pricey (I got a pair for my 34' boat for around $120 on ebay, but you have to watch to get that good a price), but barely a weekend goes by that I don't use one of them for something.

Harry

 

[twistedline]

I was just looking at the picture of those aft tracks, and realized that your toe rail is the aluminum type with holes in it. When you see that those tracks have a car on them, I as thinking you may want to get a pair of snatch blocks. That would allow you to use the tracks, AND to use the rail as a sheeting point when further off the wind.

Snatch blocks are pricey (I got a pair for my 34' boat for around $120 on ebay, but you have to watch to get that good a price), but barely a weekend goes by that I don't use one of them for something.

Harry

Thanks, I am looking on ebay for a used pair, can't believe how expensive they are.

 

[Joe]

Thanks, I am looking on ebay for a used pair, can't believe how expensive they are.

Garhauer Marine makes them and the prices are not bad.

Snatch blocks are pretty handy, but you can use a regular block with a shackle for the same purpose....you just have to use a different technique.... one way is to re run the lazy sheet then tack over.... the other is to run a SECOND sheet through the outside block, tie it on to the sail.... take the strain and release the old inside sheet. You can even control the athwartship position by changing tension on both sheets.

This is a perfect example of why having two separate sheets, instead of one long sheet folded over, is a superior set up.

 

[SailingHarry]

Thanks, I am looking on ebay for a used pair, can't believe how expensive they are.

Yes, they are typically. I just looked up what I paid for mine, and I bought them on eBay in 2009 for $94 for the pair, delivered. You do have to watch for a while.

Joe's suggestion for Garhauer is a good one, and they make really good stuff.

You have a bit of a problem with your boat size. "Dingy" size stuff is probably too small for your jib sheets, but most of the "big boat" size stuff starts at a size (and price!) suitable for boats up into the mid 30 foot range.

You might want to look at the Holt Allen ones at APS:
http://www.apsltd.com/c-546-SnatchBlocksMagicBoxes.aspx
The larger ones are $54 each, but I think they aren't big enough for you. The Antal ones for a bit more are $87 and good for a WORKING load of 1300 lb, which might be enough - and unlike the Holt Allen, they come with a "shackle" (actually a rope thinggy).