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 Post subject: H20 Downhaul question.
PostPosted: Thu May 21, 2015 7:04 pm 
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Last weekend I was out on my 20 and decided to use the downhaul to control lifting the hull out of the water. Problem was, my downhaul is slow to react when I pull it in or let it out. I have the standard H20 downhaul with new lines (the correct size) all the blocks move freely and my sail doesn't seem to be jamming up in the track. I've tried having the sail both in and out of the track and it doesn't seem to make a difference. My mainsail is about 6 years old and not in bad shape.

All the reading I've done says to use the downhaul to control the hull lift out of the water and not the mainsheet yet I can't seem to get the reaction I need out of the downhaul to make this happen.

Any thoughts, ideas or advice would be greatly appreciated.

Cheers!

tm

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1999 Hobie 20, Sail #1005
2001 Hobie 16, "Spirit of 76 sails" #18515. Sold
1981 Hobie 18, Dead!
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PostPosted: Sun May 24, 2015 3:36 am 
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Location: Jersey Shore
The stock H20 downhaul system was not the greatest. Most racers developed "cascading" systems to improve the downhaul function. A cascading system builds a pair of pulley systems stacked on top of one another in order to reduce the number of blocks required in the system and reduce friction.

For example, with the stock 8:1 system, you would have eight blocks required to generate the 8:1 purchase. In a cascading system, you multiply the purchases of each individual system to get the total system purchase. So you would have a 4:1 primary system and then a 2:1 system leading from each control line. 4:1 x 2:1 = 8:1 but you achieve this with 4 blocks + 2 blocks = 6 blocks so a 25% reduction in friction over the stock system.

The last post by HobieAndy in this discussion shows an example of a cascading downhaul system. http://www.hobiecat.com/forums/viewtopic.php?f=34&t=50719



The original H20 sails (Elliot Pattison) I believe had more luff curve a less luff length than the later Hobie built sails. The EP sails had no issue with wanting to go up when you loosened the downhaul. In fact 8:1 downhaul purchase was only marginally powerful enough for these sails, but they were very responsive to downhaul tuning. The Hobie sails, at least in my experience, were less tunable. They had a much flatter cut and were softer in the luff, so that could be why your sail doesn't want to go up when you release the downhaul.

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PostPosted: Fri May 29, 2015 5:13 pm 
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Make sure your mast track is clean, then lubricated with dry silicone or something similar. Next make sure you are not maxed out on the outhaul. A small amount of dirt/salt on the mast or bolt rope will stop the entire system from moving. Also note, if you are sheeted in hard the sheet alone will keep the tack down when you release the downhaul. It's all about balance.


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PostPosted: Sun May 31, 2015 6:45 pm 
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I didn't consider the outhaul, I'll work with it next time and see what kind of difference I can make by easing off on the outhaul and mainsheet. My sail track and sail are in good shape and the sail moves pretty easily in the track so no issue there.

Thanks for the info.

Cheers!

tm

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1999 Hobie 20, Sail #1005
2001 Hobie 16, "Spirit of 76 sails" #18515. Sold
1981 Hobie 18, Dead!
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PostPosted: Wed Jun 03, 2015 9:46 pm 
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Location: Tucson, Arizona

I think the importance of the downhaul is overstated. The crew will set it and after that it isn’t touched unless conditions change dramatically. For example, on a reach or going to weather the crew will take the wrinkles out of the luff of the main and tighten the downhaul only if looks like the conditions are going to build. A similar approach is used for the jib. It is adjusted so that the skipper can sail by it and then it is left alone.

The crew will use the main sheet traveler and the main sheet to keep the boat flat. The traveler is adjusted such that the main can be set very tight going to weather or on a fast reach.

The crew does not cleat the main. This allows him to sheet out the instant the boat starts to pick up the windward hull.

Small adjustments to the tight main allow the roach of the main to spill air and this is much better at controlling the heeling forces than the downhaul.

Just one guy’s opinion.


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PostPosted: Mon Jun 08, 2015 7:35 pm 
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Abraham Jones wrote:

I think the importance of the downhaul is overstated. The crew will set it and after that it isn’t touched unless conditions change dramatically. For example, on a reach or going to weather the crew will take the wrinkles out of the luff of the main and tighten the downhaul only if looks like the conditions are going to build. A similar approach is used for the jib. It is adjusted so that the skipper can sail by it and then it is left alone.

The crew will use the main sheet traveler and the main sheet to keep the boat flat. The traveler is adjusted such that the main can be set very tight going to weather or on a fast reach.

The crew does not cleat the main. This allows him to sheet out the instant the boat starts to pick up the windward hull.

Small adjustments to the tight main allow the roach of the main to spill air and this is much better at controlling the heeling forces than the downhaul.

Just one guy’s opinion.

+1

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PostPosted: Tue Jun 09, 2015 2:49 am 
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Abraham Jones wrote:
I think the importance of the downhaul is overstated.


Maybe if you aren't racing. But that wasn't my experience and we raced the 20 in a relatively competitive fleet for about 10 years. All the top racers played the downhaul extensively. Sheet and traveler were virtually always kept centered and tight and the boat was controlled through steering and downhaul.

The advantage of using the downhaul to manage puffs is that tightening the downhaul bends the mast which flattens the sail and causes the top the twist open. This reduces drag and lowers the CE of the rig which allows the boat to sail flatter and faster. Easing the mainsheet has the opposite effect - it straightens the mast which makes the rig fuller and causes more drag. You have to dump a lot of sheet to get the boat to depower and you lose your upwind pointing angle. Similarly, if you try to do it through traveler adjustment, you close off the slot between the main and jib and you lose upwind pointing angle.

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PostPosted: Sat Jul 04, 2015 11:15 am 
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Location: Tucson, Arizona

Usually when I go sailing it’s to go racing. Unfortunately, when the H16 was traded for a H20 the days for going out and messing around went with the H16 but I digress.

I almost never race against other H20(s) though. In these parts I sail with a multihull fleet and we’re up against P19(s) and NACRA5.8(s). Sad to say but in the 4 corners area I can probably count the number of H20(s) on one hand.

The downhaul controls the “belly” of the main? Full versus flat. In light wind I want a full sail and the reverse in high wind. This makes me think of the downhaul like the position of the jib cars. In light wind I want a tight jib leech, forward, and in high wind I want a tight jib foot, back. I set it and forget it.

With the boat on the beach and the main sheeted very tight the leech is flat. When the sheet is eased about a foot the boom will move up not out and the leech will start to curve. This curve is what allows the main to spill air?

How well does this work? I’m usually in the hunt with the other multihulls in triangle racing. I think mark roundings are what dominate triangle racing. Speaking of which when is the last time anyone was in a race with a reaching mark? In distance racing, I think the technique is faster. On a long reach when can case down the other multihulls and never look back.

Again, just one guy’s opinion.

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PostPosted: Mon Jul 06, 2015 10:50 am 
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The downhaul is huge in the 20. Div 3 guys would attest to this as our crews all effect the downhaul to adjust for the puffs.

We effectively use it to bend off the top of the mast and spill the wind out of the top of the sail. This moves the center of effort lower in the sail and flattens the boat out.

The last and least depowering option is easing the main sheet unless in extreme situations. This is more multiple reasons.
1. It releases the tension on your forestay which affects your pointing ability.
2. It creates a larger wing (main sail) which creates more drag.
3. Moves your whole rig forward.
4. It takes longer to recover the speed you just gave away.


In big winds my first options are:
1. Ease the traveler out 3- 4- 5 inches. This keeps the rig tight and keeps the jib shapely (boat will continue to point)
2. Move the jib cars out. (Open the slot)
3. Increase the bend in the mast with prebend on the beach. (only if you know it's howling because I don't like giving power away before I leave the beach)
4. Manage puffs with downhaul and pointing up.
5. Ease sheet

If you are in a race condition it is important to keep the boat flat. I was second in this weeks Hobie 20 Regatta in Monterey (8 boats) and the guy that beat me never lifted his hull out of the water. Winds were 8-17 knots all three days. The key to being fast on these boats is your ability to depower the boat effectively without big swings in rig shape...... The downhaul is a big part of that. Flat flat flat.........

Hammond wrote:
Make sure your mast track is clean, then lubricated with dry silicone or something similar. Next make sure you are not maxed out on the outhaul. A small amount of dirt/salt on the mast or bolt rope will stop the entire system from moving. Also note, if you are sheeted in hard the sheet alone will keep the tack down when you release the downhaul.


+1

srm wrote:
The advantage of using the downhaul to manage puffs is that tightening the downhaul bends the mast which flattens the sail and causes the top the twist open. This reduces drag and lowers the CE of the rig which allows the boat to sail flatter and faster. Easing the mainsheet has the opposite effect - it straightens the mast which makes the rig fuller and causes more drag. You have to dump a lot of sheet to get the boat to depower and you lose your upwind pointing angle.


Perfectly stated srm!

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H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
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PostPosted: Mon Jul 06, 2015 7:50 pm 
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Location: Florida Panhandle
Wow! Great inputs on the topic and I'm definitely working on learning to use the downhaul more. I did a couple things these last few weeks to help out.

#1. I replaced the mast base due to a broken ear where the pin goes through below the mast ball, as part of the change I also replaced all the hardware associated with the mast base including new sheaves for the downhaul and halyard, that alone made a huge difference in not only raising the mainsail but also in the effectiveness of the downhaul as the new sheaves and blocks rotate so much more easily.

#2. I focused on the rudders to control adjusting the height of the windward hull above the water, this gave me confidence so I wasn't relying on the mainsheet to keep the boat from flipping and making adjustments. I was able to leave the main sheeted up tight and start working the downhaul more and I did notice much better response and felt much more comfortable and confident as the day wore on. There's still a ways to go and I did put the boat on it's side twice which was a bummer since I was sailing single handed this weekend. I had an assist once and the second time I had the boat back upright in less than three minutes by myself.

I continue to learn each time out and am getting much more confident with the boat although it humbles me quickly if I get too cocky!

One thing I am noticing and can't seem to get corrected is; the luff of the mainsail seems to be always stalled, usually the front 1/3 of the sail above the first batten up to the top most batten seems to continuously be stalling. I've adjusted everything I can think of to change the shape of the sail however, I can't seem to get the entire mainsail generating power. My mainsail was new in 2008 and the Jib is the original 1999 if that makes a difference. Any advice would be appreciated and I'll repost this in a new thread if needed.

Thanks again for all the help wish you guys were close to Ft Walton Beach so I could pick your brain over a cold beer... out on the water of course!

Cheers!

tm

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1999 Hobie 20, Sail #1005
2001 Hobie 16, "Spirit of 76 sails" #18515. Sold
1981 Hobie 18, Dead!
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PostPosted: Thu Jul 09, 2015 9:26 am 
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If the leading edge of your main is luffing down low, you may be cutting off the slot by having the jib cars too far inboard. From my recollection (o more then 10 years ago now) we typically ran the jib leads about half way between the hiking straps and the inboard edge of the hull.

Otherwise, maybe try pulling on more downhaul (and possibly outhaul) to flatten the lower section of the sail.


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PostPosted: Thu Jul 09, 2015 12:22 pm 
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srm wrote:
you may be cutting off the slot by having the jib cars too far inboard


+1

-You could be pinching to much in stronger winds. (ease the traveler out to depower)
-Mast rack could be to far forward.........(how much helm do the rudders have?)

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H18 '85
H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
Fleet 259 Central Coast California


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