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Old 23-02-2015, 09:58   #16
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Re: Weatherhelm Advice, Seeking Balance

Quote:
Originally Posted by Cheechako View Post
Here's a pic:
With the working jib as shown the combined CE is just at the forward edge of the mast. Now visualize a 150 genoa in the plan. The CE of the Genoa will be considerably aft of the one shown on the jib. Combining the CE's will move the total CE aft of the mast.... creating more weather helm. Right?
Not in my opinion, because of the disparity in sail sizes between a reduced headsail and a full main. But as I said, you can see this easily yourself when you're on the boat, just try it. pete
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Old 23-02-2015, 10:40   #17
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Re: Weatherhelm Advice, Seeking Balance

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Originally Posted by pete33458 View Post
Not in my opinion, because of the disparity in sail sizes between a reduced headsail and a full main. But as I said, you can see this easily yourself when you're on the boat, just try it. pete
Well....... that is Ted Brewer's explanation....
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Old 23-02-2015, 10:49   #18
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Re: Weatherhelm Advice, Seeking Balance

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Originally Posted by Cheechako View Post
Well....... that is Ted Brewer's explanation....
What does he know???

Let's take a hypothetical where you are using a roller furling headsail and you have furled it all the way up until only 5% or so of the sail is set. Clearly, the CE of the headsail is well forward. Would this move the overall CE forward? I don't think so.

Are there people out there that put a smaller jib on, without changing the main, specifically to reduce weather helm? This goes against my experience and everything I was ever taught, which is to reduce mainsail area first. But I guess I could be wrong. And every boat is a little different. Some boats are a lot different. Pete
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Old 23-02-2015, 10:50   #19
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Re: Weatherhelm Advice, Seeking Balance

Quote:
Originally Posted by Cheechako View Post
Here's a pic:
With the working jib as shown the combined CE is just at the forward edge of the mast. Now visualize a 150 genoa in the plan. The CE of the Genoa will be considerably aft of the one shown on the jib. Combining the CE's will move the total CE aft of the mast.... creating more weather helm. Right?
Close, except that the CE should be shown aft of the CLR, not ahead.
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Old 23-02-2015, 11:11   #20
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Re: Weatherhelm Advice, Seeking Balance

Rig and sail tuning will be a wast of time with poor sails and if you lack controls such as reefing. My advice would be look at the used sail sights and get some cheap but serviceable sails and sort ot the sail controls. This should not be mega $. The sails you get can be 'under weight' they don't need to last. Once you do this then tuning should work and you will start to understand it because the right things will be happening. At the moment t may be that you have so much drag from some sails that anything you do to adjust other to correct the balance simply wont be enough so does not seem to work.
This approach has worked for me and then when you do come to get new sails you have the confidence to get good one because you really know what works on your boat for the sailing you do
Hope this helps
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Old 23-02-2015, 11:26   #21
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Thumbs up Re: Weatherhelm Advice, Seeking Balance

Well said Roland.
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Old 23-02-2015, 11:41   #22
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Re: Weatherhelm Advice, Seeking Balance

Further though if you want to play with sails. I use this design program both to plan configurations and to create sail shapes and patterns. It also allows you to do things like plot centers of effort and centers of drag (but not calculate them). Might be fun learning tool and its free. X-SailcutCAD For fore & aft sails; sailcut_6_1_7151 for downwind sails. If you cant find them on the internet PM me with an email address and I can send you zipped copies. Not huge, they run fine on a laptop.
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Old 23-02-2015, 11:51   #23
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Re: Weatherhelm Advice, Seeking Balance

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Originally Posted by pete33458 View Post
What does he know???

Let's take a hypothetical where you are using a roller furling headsail and you have furled it all the way up until only 5% or so of the sail is set. Clearly, the CE of the headsail is well forward. Would this move the overall CE forward? I don't think so.

Are there people out there that put a smaller jib on, without changing the main, specifically to reduce weather helm? This goes against my experience and everything I was ever taught, which is to reduce mainsail area first. But I guess I could be wrong. And every boat is a little different. Some boats are a lot different. Pete
We're not discussing the difference between a 10% and 5% jib.

Once again, the extra area on a 150 genoa is not at the front, it's at the rear. A 100% already fills the fore triangle, so the extra area on a 150 is AFT OF THE MAST. Add to that the fact it's got far too much draft in stronger winds.
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Old 23-02-2015, 11:54   #24
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Re: Weatherhelm Advice, Seeking Balance

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Originally Posted by MarkSF View Post
We're not discussing the difference between a 10% and 5% jib.

Once again, the extra area on a 150 genoa is not at the front, it's at the rear. A 100% already fills the fore triangle, so the extra area on a 150 is AFT OF THE MAST. Add to that the fact it's got far too much draft in stronger winds.
Mark's earlier comments are well taken.

He & I read the same material:

Jib Size Selection
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Old 23-02-2015, 12:08   #25
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Re: Weatherhelm Advice, Seeking Balance

The other complication with large overlaps is that the CE changes significantly depending on the main. If set with no main it is calculted in the convetional way as the center of the sail area. Set with a main that extends past the head-sail leech half the sail is acting as a vortex slot to decrease pressure on the lee surface of main giving very diferent (and complex) dynamics. You probable need to ignore anything over 125% in order to get a true centre off effort. Correspondingly reducing sail area on a 150% head sail does not alter it's center of effort but rather changes the drag characteristics or the overall sail plan.
My boat was designed with this sail plan. It was a common one in early IOR boats. It's only advantage is that under the rating rules any sail beyond the 100% foretryange did not count in the sail plan. When racing this means you can carry more sail. It is actually very inefficient and difficult to handle. The sails are really unwieldy and do not adapt well to roller furling.
On the plus side the giant head sail/small main combo means the mast is set well back so they convert very well to a cutter rig. Use about 115% overlap o ate stay sail and a 90-110% high cut jib and you get a very good cruising setup. The icing on the cake is to add a short bowsprit and fly the old (usually quite light) 150% Genoa from it as a Goaster.
Hull shape also comes into the equation as differnt hull keel configurations change the balance depending on angle of heel.
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Old 23-02-2015, 13:02   #26
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Re: Weatherhelm Advice, Seeking Balance

There is a very good book written by Ivar Dedekam: "Sail & Rig tuning"
Illustrated Nautical Manuals - Dedekam Design
cover all main issues,including helm balance and a lot more.
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Old 23-02-2015, 13:11   #27
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Re: Weatherhelm Advice, Seeking Balance

Well....I'd like to add another thought or two:

1. I looked up the Alberg 35 and saw what is almost a full keel cruising boat with forward and aft lower shrouds and an upper with a masthead rig. I don't expect this boat to point any higher to the wind than 40 Degrees with the 100% headsail. To attempt to do 40 degrees to windward with a 150% Genoa would be a lot of work if not fruitless. 'Gentlemen sailors do not sail to weather' I read that somewhere.

2. We sailors are trying to point higher to the wind by creating a wing like an airplane, lift over drag if you will. Therefore to go to weather optimally we move the draft in the main sail forward by increased halyard tension and in applying tension with a Cunningham on the main and a great amount of outhaul tension. The head sail works the same except it accelerates the wind across the windward side of the main as well.

3. The sail maker told the OP that he should cut 1.74 inches off the forestay. I find that to be absurd to change the design. That is a lot of stretch on a wire rope rig to need that much adjustment. That is why I posted earlier that the mast needs to be straight before making changes to the design. It appears from the spec that this boat may have a dagger or centerboard in the profile drawing I looked at. We all know that to be a factor if it is true.

If the OP does not modify or replace the old main, I would say apply lots of outhaul, lots of halyard and sheet it off to where the roach or leach of the main is driving the boat, coupled with a footed off jib and 5 degrees of leeward heading from the highest point of sail. I suspect the boat moves adequately off the wind. To go to weather with an old main my require living with a backwind bubble in the front of the main to get it balanced.

I'm just saying.....
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Old 23-02-2015, 13:19   #28
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Re: Weatherhelm Advice, Seeking Balance

Assume that your boat has no reef points is because the boom is that abominable roller reefing type. See if you can resurrect the reefing of the boom. Will usually have a worm drive set up on the goose neck to rotate the boom. You'll need a handle with the proper receptacle to get it to work. See if you can find such an animal in the detritus aboard. If not there, make one up out a socket or any suitable piece that a welder can jury rig for you. Try reefing the main with the roller furling when you get it functioning and see if that helps.

Those old roller furlers are pieces of crap that will ruin a sail and might have already done that with yours. If you go with a new sail, get reefing points put in the sail and set up the boom for slab reefing. A couple of cheek blocks, cleats and probably a small winch will get it done. Buying the parts used off Ebay, Craig's List or a consignment chandler will get it done cheap.

Raking the mast forward will change the CE and reduce weather helm. It can also induce lee helm in low winds/boat speeds. I can live with weather helm, lee helm is an absolute no no for me, however. From your sailmakers recommendation, sounds like you need to shorten the headstay as the turnbuckle is maxed in. Get yourself a Norseman/StaLok terminal for the wire and try shortening it. Probably wouldn't hurt as an experiment. If it doesn't work, another terminal and 40' feet of SS 1x19 wire will get you back where you started. Probably time to replace the headstay anyway.
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Old 23-02-2015, 13:43   #29
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Re: Weatherhelm Advice, Seeking Balance

All this talk of CE/CLR assumes the forces are static, no heel. With increased heel, the CE moves outboard over the water. The drag in inboard, creating a torque that drives the boat into the wind as well. This is a large reason that boats head up in gusts when they heel. Nothing to do with the fore and aft location of the sails.

Baggy sail/too big sail = too much heel equals weather helm.
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Old 23-02-2015, 13:52   #30
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Re: Weatherhelm Advice, Seeking Balance

[QUOTE=D.C.Y.;1756917]I have a 1965 Alberg 35. She has a degree of weather-helm.

I may just be too concrete in my reading but 1 degree of weather helm is about as good as it gets. What I think I am saying is that if you have to turn your wheel or tiller 1 degree to sail the course you want, than that is 1 degree of weather helm. Up to 4-5 is fine. The more weather helm the more you have to turn your rudder, the more rudder drag you have i.e. less effecient.
I also think a little weather helm is a little bit of a safety factor. If you become over powered the boat will turn into the wind and loss power.
I am a beginner but in reading about using wind vanes, your boat has to be very balanced to have the vane work good. In acchieving that well balanced sail configuration I think you should expect a little loss of speed.
I would be interested you your experts opinions on my post!!??
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