jib sheet leads

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jib sheet leads

Postby Clyde » Thu Jun 20, 2013 8:14 pm

Somewhere in the back of my mind is the idea that the lead of the jib sheet should be perpindicular to the luff of the jib. If this is so then the turning block would be quite far back from the cuddy along the gunwale rather than just at the aft end of the cuddy. Am I nuts?
Clyde Starr
DS1 #11354
"Downsized"
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Re: jib sheet leads

Postby Alan » Thu Jun 20, 2013 9:51 pm

While waiting for the real sailors to chime in, I'll pass the time with my uninformed opinion. :)

If the clew is in its normal position, that is, somewhat close to the hull and, in the case of racing sails that sweep the deck just about on the hull, you would need the jib sheets to be cleated forward, not far back, or the angle wouldn't be perpendicular to the luff. To have a perpendicular angle with the cleats far aft, the clew would have to be way the heck off the deck, meaning a very high-cut foot.

My Neil Pryde jib, which I'm pretty sure is original to my 1980 DSII, has a high-cut foot, but the sheets are just about perpendicular in the factory-original cleats, which are on the inside of the coamings just aft of the cuddy bulkhead.
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Re: jib sheet leads

Postby GreenLake » Fri Jun 21, 2013 12:53 pm

The instructions that came with my sail essentially said to cleat at the forward end of the track in all conditions and then use various amounts of barber hauler.

That rule about the right angle is only an approximation. You do want slightly different directions of pull depending on conditions, because different conditions call for various degrees of twist.

Nothing beats observing the airflow around your sail directly, and the way to do that is to fit tell tales. Most will have a set of tell tales about a foot in from the front and 2-3 feet up, but you can mount additional sets higher up. If they all fly in unison, the set of your sail would match the wind. Same as luffing to see whether the jib breaks everywhere along the luff or first at the top or bottom, but tell-tales react more quickly and may give you a more explicit signal.

Now for the theory:

Winds below about 5 kt over the water have laminar flow, so called because the air is in layers of increasing speed from the bottom (0 at the water level, due to friction) to the full speed higher up. With the boat stationary, a series of streamers up the mast would fly more horizontally as you go up, because wind speed increases. Once you are moving, the apparent wind is combines a fixed boat speed with a variable speed of true wind, as you go up the mast. The resultant vector will show a change of apparent wind direction as you go up the mast. The same set of streamers would now fly at different directions. At the bottom they would fly aft more, because the effect of boat speed dominates, at the top they would fly somewhat more in the direction of the true wind.

So if you have twist in your sails so that it matches the twist in the wind, more of your sail will draw.

In higher winds, the apparent wind is more uniform (turbulent airflow allows full wind speed almost to the water) but twist in your sails can be helpful again if it will spill the wind when you are overpowered.

With a full set of tell tales you can be in control.

In his book, High Performance Sailing, Frank Bethwaite has a nice series of photos of just such a streamer experiment.
~ green ~ lake ~ ~
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Re: jib sheet leads

Postby Salty Dog » Sat Nov 16, 2013 2:23 pm

Greenlake

I have swivel cleats w/ fair lead mounted on top of my coaming about a foot or so back from my cuddy top. There is a pic of them in my album on this site.( pay no attention to fishing rods in cock pit, pic was taken while in storage :) ) I am going to replace them with same but better quality cleats in same place due to recent cleat failure trouble During a race. I saw some mounted on cars on tracks a foot long at D & R and I was wandering if you thought the cars would be the way to go for the adjustments you were talking about or would a foot track on a DSII jib make that much difference. They were a $190 for a pair which was prob. closed to what I would pay for stationary swivel type.
I don't know if you are familiar w/ D&R but you can look at them there.
The ones that are on there are brass cleats and were worn I dressed them with a file but I think i will replace them. The center to center screw for the cleat itself does not match any of the other plastic cleats I have, and the swivel does not swivel too well

SD
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Re: jib sheet leads

Postby GreenLake » Sat Nov 16, 2013 4:07 pm

Your gallery image shows them in action
1615

The advantage of a track would be that you could adjust the trim of your jib. If you moved the cleat back the foot of the sail would be pulled more into a straight line while the leech would curve more (spilling wind at the top). If you moved the cleat forward, the leech would be closed with the foot curved more.

If the price is the similar, I'd opt for tracks - but only if you are interested in actually figuring out the best adjustment for each conditions.

Are you happy with having the cleats at the leeward coaming? My tracks just have the blocks and the cleats are fixed on the CB trunk. Something to consider when you do the upgrade.

I had a track of similar make as the D&R fail on me the first time I took out the boat (there was an issue with the screws not holding). But I opted to replace with a Harken track which is stiffer. (Model 453 and cars model 450 with some suitable block). I recall not paying quite as much as what these are listed for nowadays....

With barber haulers, you could sheet in more, which might be what you'd want in this situation
1611
~ green ~ lake ~ ~
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Re: jib sheet leads

Postby Salty Dog » Sat Nov 16, 2013 5:18 pm

How long are your tracks? I am deffinatly going to try them out and I know their porpose but I was not sure a 1 ft track would make a difference and I did not want to put on a track too long that it inter fered with sitting on the rail and hiking out. I will have to reconsiter the track if you had a failure. I thought they looked lite but I always over build and it is a dingy, but i'll look at the better tracks.because "FAILURE IS NOT AN OPTIONNNNN" I"ll whip this boat into shape till its sailing like a "WELL OILED MACHINE"...............Where did I put my screw driver?..... It was right here!
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Re: jib sheet leads

Postby GreenLake » Sat Nov 16, 2013 9:02 pm

Now, I have a DS1, and that means that the tracks are mounted on the insides of the coamings and not on top.946
(From the picture it looks like a 12" track)

1034
Located as they are, and cleated off at the CB trunk
there's a pull away from the base, loading the screws on tension.

In your placement, the screws would be loaded on shear, which makes them
less likely to pull out. My old track broke when a screw pulled out and one end
of the track received bending loads it was not designed to hold.

I do like the appearance of the replacements better, perhaps just a question
of the design not looking like stamped sheet metal.

Now, the one thing I don't like 100% about my layout is that the slightest tug
on the jib sheet will uncleat it, and it's hard to re-cleat it without pushing down
on the sheet. If I had a fairlead before the cleat, that would hold the sheet
down, but then I would be unable to grab the sheet near the track, pull it tight
with one hand and cleat it (I would need always grab it on the far side of the
cleat - which is amazingly often not the best place to grab it). A solution
would be a fairlead that has an opening - so you can feed the sheet into
it from the side. However, I haven't seen such a design anywhere.
~ green ~ lake ~ ~
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Re: jib sheet leads

Postby Salty Dog » Sat Nov 16, 2013 9:30 pm

Greenlake

I looked at the tracks you told me about and they do look pretty good and cost more but not that much more. I think I will order me some and put them on my to do list. I guess the best place to put the track is half and half on the point perpindicular to the forstay thru the clew( Neutral) and that would give you equal adjustment both ways. Or do you find more adjustment one way or the other is needed on the DS jib.

i like where my cleats are now I can cleat and pop them loose right in front of me. but I guess it's all what you get used to. Plus that trick of tieing the sheets together you told me about makes it easy to come up with the right sheet even hiked out.

SD
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Re: jib sheet leads

Postby jeadstx » Mon Nov 18, 2013 3:33 pm

My tracks are also on the inside of the coaming which is common with most DS2's. I had to put inspection ports in the coaming to repair my tracks as they had pulled loose during the Texas 200 this year. I used 5" Inspection ports. The backing wood was completely rotted. I put in new backing plates and with the inspection ports I will be able to access them in the future. I had previously moved my cam cleats to the CB trunk.

John
1976 Day Sailer II, #8075 - Completed the 2011, 2012, and 2013 Texas 200
1952 Beetle Boat Swan Catboat
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1973 Mariner 2+2, #2607 - Completed 2014, 2015 and 2016 Texas 200
1969 Day Sailer I, #3229
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