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Old 23-04-2013, 06:12   #31
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Re: Excessive weather helm even on reach

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Originally Posted by stevensuf View Post
We recently crossed the atlantic and we did vristually from gibralatar to cananries to cape verdes to antigua under poled out genoa, so i am wondering it it has bagged slightly depowering the genoa and too much in the main, but i still think surely a bagged out genoa should be less of an issue with the wind on the side, than on the nose?
Downwind sailing, especially with the sail poled out causes less stretching than upwind sailing on a genoa all things being equal.

A bagged out genny will still generally have the same "power" in fact it will have more power as the draft depth of the sail has increased and will generate more lift - although at the expense of increased drag. This may mean that you have to furl earlier as your sail is more powered up than a new sail with the same settings.

The really undesirable part of a blown out headsail is the fact that the draft location has shifted forward. This can dramatically change your pointing ability by 10-20 degrees since with the draft location forward your entry angle for the headsail also changes which effectively changes your sails angle of attack - and you cant point as high.

Below a beam reach a blown genny, that still has an aerodynamic shape, doesnt dramatically affect boat performance from a cruisers point of view.
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Old 23-04-2013, 06:39   #32
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What I forgot: a genoa gets flatter when it has a foam leech and is partially furled. This reduces sail area at the same time so that heel gets reduced even more.

I agree with Andrew and am still surprised how many sailors still think about the fore- and aft sail area to be the factor in weather helm. Try to see/imagine how the boat gets pulled around to windward when pulling on a heeled mast. This, together with the asymmetric hull shape is all a cruiser needs to work with: the rest is for racers. The easy part is that both problems are the direct result of heel. Reduce heel.

On a reach, a rudder angle of 5-8 percent is normal. Being a ketch, we can trim it all the way back to 0 degrees, but that slows us down. Our best performance (which on a reach is measured by true wind speed vs boat speed at same wind angle) is with 7 degrees rudder.

Big genoas are the result of race class designs, even for non-racers. To keep these in shape is a costly business. Our original foresail was a 100% jib and after evaluating the sailplan and optimizing it (by Elvstrom-Sobstad), we even went for a 95% jib. But it is tri-radial cut and high aspect. This is the trick:find the smallest sail area that gives you all the forward drive required. This leads to the requirement of very efficient sails and high tech construction, and away from in-mast furling.
The small sail area does not result in slower performance when kept within these specifications: it results in less heel and faster performance. We can do 300+ nm days with it.

Look at the shape of the jib, the heel angle and the speed:
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Old 23-04-2013, 06:53   #33
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Re: Excessive Weather Helm Even on Reach

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Originally Posted by s/v Jedi View Post
Big genoas are the result of race class designs, even for non-racers.
That may have been true but is not the case now. Sail plans for modern race boats are mainly using larger high aspect mains and smaller high aspect head sails.

Many cruisers dont have or dont want to use spinnakers or asyms so a larger headsail has a much greater range of functionality off the wind, especially when poled out. If you are going downwind it is much easier for a couple cruising to keep up twin poled out headsails on furlers in moderate conditions than it is an asym or chute.
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Old 23-04-2013, 07:57   #34
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Re: Excessive Weather Helm Even on Reach

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Originally Posted by foolishsailor View Post
That may have been true but is not the case now. Sail plans for modern race boats are mainly using larger high aspect mains and smaller high aspect head sails.

Many cruisers dont have or dont want to use spinnakers or asyms so a larger headsail has a much greater range of functionality off the wind, especially when poled out. If you are going downwind it is much easier for a couple cruising to keep up twin poled out headsails on furlers in moderate conditions than it is an asym or chute.
Oh, I didn't mean modern racers... I meant that current cruising designs are often based on -older- racing designs, like IOR etc.

A gennaker is easier to sail than twin headsails boomed out I think. Surely, the designs with big genoas are not put on paper for downwind sailing; all designs are based on upwind sailing, except for very specific boats that are a minority on the market (like ours which is a reaching machine, despite it's small jib! I can't think of a big genoa design that is faster reaching than our boat now that I think of it...)
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Old 23-04-2013, 13:45   #35
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Re: Excessive weather helm even on reach

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Originally Posted by goboatingnow View Post
I wouldnt regard 4-6 degrees as "excessive" weather helm in many boats, 10 degress yes. Id regards 4-ish degrees as about right. You want some weather helm for safety

Dave
+1

Maybe you don't actually have a problem at all?
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Old 24-04-2013, 06:02   #36
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Re: Excessive Weather Helm Even on Reach

the 4-6 degrees was when i let the main right out to spill most of the wind before this it was more like 8-10 degrees, on a side thought, we damaged our davits last week, (let the dinghy get full of water and one side bent) i noticed it is pushing slightly on the port side backstay, i wonder if this is the cause of it all? certainly the mast wont be able to flex forward as much as it used to.
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Old 24-04-2013, 06:19   #37
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Re: Excessive Weather Helm Even on Reach

It's possibly worth adding that excessive weather helm is (in my experience, on most boats) more prevalent power reaching than on any other point of sail. On a boat with a swing keel, it's generally worth swinging it well aft when power reaching.

Furthermore, the main should be fully out against the rigging on anything from a true beam reach, (at which point the apparent wind is still ahead of the beam) particularly if it's blowing. The vang should be hard on to prevent the sailcloth working and chafing against the rig.

Good thread, lots of interesting points. Thanks for the education, guys!

Steven: I doubt the backstay issue is significant, or connected to what you describe.

Is it possible that you've put in a lot of miles and simply got a bit more gung-ho or blasé than you use to be about how much sail to carry on a reach in a breeze? combined with the sails bagging out - (which alone, IMO, could easily explain it)
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Old 24-04-2013, 07:29   #38
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Re: Excessive Weather Helm Even on Reach

I think as Jedi has pointed out on this and many other threads on sail trim - excessive heel is usually the leading factor in excessive helm.

Reduce/balance sail until your heel is under control first and if you still have excessive helm then try all the other things on this thread.
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Old 24-04-2013, 07:32   #39
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While heel is a major factor. On the 28 footer I race on, its the power of the main to drive the boat to weather that cause weather helm. I mean its mainsail can easily overcome the ruddder, we have to trim to steer , irrespective of heel angle.

Dave
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Old 24-04-2013, 07:37   #40
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Re: Excessive Weather Helm Even on Reach

Quote:
Originally Posted by s/v Jedi View Post
Oh, I didn't mean modern racers... I meant that current cruising designs are often based on -older- racing designs, like IOR etc....

...Surely, the designs with big genoas are not put on paper for downwind sailing; all designs are based on upwind sailing...
Fair enough. However the change from IOR to IRC for racing desing happened in the early 90's. Any production boat built after that was no longer influenced by IOR design as it was not utilized any longer. you can see this change reflected in the design changes in the production boats like Bene's. Especially the design changes Bruce Farr brought in.

Since IRC favors smaller headsails I have to question the idea that large headsails on most cruising oriented boats are based on influence of racing design but instead as they are more practical to the needs of a boat that will be doing more than beating and deep reaching/running?

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Originally Posted by s/v Jedi View Post
A gennaker is easier to sail than twin headsails boomed out I think.
Agreed - but up to what wind speed?
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Old 24-04-2013, 07:47   #41
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Re: Excessive weather helm even on reach

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Originally Posted by Jim Cate View Post
Yes, RAku, sometimes that can help. However, if the material is stretched enough to cause the problem, it is likely to continue to stretch after recutting and soon one is back to where you started.

Might be interesting to get Island Planet's take on this if he is around... his advice is usually quite sound IMO.

Cheers,

Jim

I had another thought about this -- maybe it's a good idea to periodically really harden up the sails, even if that requires steering off course for a while, to encourage those fibers to line up properly again? You can do this with lighter weight, more simply woven fabrics (I'm not talking about marine fabrics here). Eventually a sail is going to wear out, the sail will sag, and it has to be replaced, but maybe that time could be extended by getting at least some of the bias out sometimes? Maybe on extended cruising it's just not worth it ...
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Old 24-04-2013, 07:52   #42
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Re: Excessive weather helm even on reach

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Originally Posted by foolishsailor View Post
Regardless of how much the headsail has blown and the draft has shifted back, the vector of the headsail will still be in front of the CE for the sail-plan.

With a reefed main and full genoa your CE should be forward of optimal causing LEE helm - likely even if the main was over-trimmed.

However you mention weather helm. The only variable left would be the heel angle as others have mentioned.

DO you normally leave a full genny with reefed main? Some boats can carry a full genny with the first reef, some cant.

I would do the following to reduce heel:
1. Ensure traveller is all the way out
2. If you have an adjustable backstay bang it on hard
3. Try either of the extremes on your vang tension - either on hard or really loose to open the leech
4. Most important - if you are unable to reduce heel and correct weather helm using sail controls then you need to reduce sail

edit: I am assuming that halyard tension on your headsail will have little affect on draft position since you describe what you think is blown sail, but increased halyard tension on both main and headsail can help shift CE forward as well.
Which raised an interesting question in my mind -- no one has mentioned the use of a Cunningham to help harden up the mainsail ...
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Old 24-04-2013, 07:53   #43
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Re: Excessive Weather Helm Even on Reach

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Originally Posted by goboatingnow View Post
While heel is a major factor. On the 28 footer I race on, its the power of the main to drive the boat to weather that cause weather helm. I mean its mainsail can easily overcome the ruddder, we have to trim to steer , irrespective of heel angle.

Dave
Yes indeed. Let me mention again that everything I wrote in this thread is NOT for racers. That remark might got lost in all the rest

Modern racers see the same problems but they are multiplied because the design is more extreme. This makes factors, which are not very relevant for cruisers, big enough to become important for sail trim.
It also multiplies the heel factor: weather helm gets much worse with 10 degrees extra heel than for a cruising design. The same factors still apply and are still at the top of the list.
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Old 24-04-2013, 07:59   #44
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Re: Excessive weather helm even on reach

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Originally Posted by Rakuflames View Post
Which raised an interesting question in my mind -- no one has mentioned the use of a Cunningham to help harden up the mainsail ...
Many cruising boats dont have a cunningham so increasing halyard tension is used instead. Both tools in effect tighten the luff.
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Old 24-04-2013, 08:04   #45
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Re: Excessive Weather Helm Even on Reach

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Originally Posted by foolishsailor View Post
Fair enough. However the change from IOR to IRC for racing desing happened in the early 90's. Any production boat built after that was no longer influenced by IOR design as it was not utilized any longer. you can see this change reflected in the design changes in the production boats like Bene's. Especially the design changes Bruce Farr brought in.
Bruce Farr saved Beneteau when he designed a Whitbread racer that became the basis for the Beneteau First series. When Pininfiara designed the interior it became a boat everybody loved.
He was then hired long enough for them to computer model his designs so they could put their own design team on it again. That's when true innovation stopped again.

On boats built after IOR went obsolete: unfortunately they still to this day build boats based on IOR designs. What you must mean is that boats that were designed after IOR were mostly cured of the big belly and huge genoa.

Quote:
Since IRC favors smaller headsails I have to question the idea that large headsails on most cruising oriented boats are based on influence of racing design but instead as they are more practical to the needs of a boat that will be doing more than beating and deep reaching/running?
I think you are very optimistic about the connection between sailboat designers and us cruisers. I can name Steve Dashew and Dirk Nauta as two who did know what cruisers wanted. Most of the rest just did what the charter companies wanted, which wasn't even enough for the Moorings who hired their own guy to modify the designs even further.

Quote:
Agreed - but up to what wind speed?
Now you make it too easy for me : up to the wind speed that one standard jib is enough sail again
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