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Weather helm, under headsail only?

Sep 30, 2013
2,909
1988 Catalina 22 central Florida
Can someone explain to me how the heck this happens, before I scratch my head bald? We're talking about a masthead sloop here. I had read some time ago that this could happen, but I didn't really believe it.

Then recently, on a friend's Cal 33, we were sailing under just a 150, with the main down and bagged. And I'll be darned if she didn't pull pretty hard to windward in the puffs. This made no sense to me. There should have been lee helm if anything, darn it.

I have one theory: most of the hull (this boat has a lot of freeboard), most of doghouse, the Bimini, the boom, all the people in the cockpit, etc ... are all aft of the CLR. That's a lot of windage, maybe this was enough to push her bow up? Also the jib winch is obviously way aft of the CLR, and I assume there would be at least some force to leeward exerted on the winch, via the sheet?

Or, am I not even close. ;)
 
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Oct 22, 2014
10,380
CAL 35 Cruiser Portland OR, moored EVERETT WA
It is a bit unusual.
You are looking at the right suspects.
You said Genoa. 150. So if fully unfurled 50% of the sail would be behind the Mast. With the mast as the center of the boats longitudinal mass the combination of windage, sail, and direction of wind might be able to give you weather helm.

I conjecture you were not close hauled beating up wind at the time.
 
Oct 22, 2014
10,380
CAL 35 Cruiser Portland OR, moored EVERETT WA
The weather helm is a subtle signal from the boat that you may have a bit too much canvas flying for the puffs.

Again assuming that the wind was greeting the boat abeam.
 
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May 17, 2004
2,007
Beneteau Oceanis 37 LE Havre de Grace
Also remember that the sail is pulling you not just sideways but also forward. That forward pull can cause weather helm if its vector is "outside" the center of lateral resistance. For example, on a reach, when the sail is eased out and pulling forward, the center of effort the sail is basically just pulling the leeward side of the boat forward, which will tend to round you up.

Also, as the boat heels more that center of effort goes, with the mast, further outside the boat, and the mast becomes a lever trying to turn the boat up.
 
Apr 16, 2017
679
Federation NCC-1701 Riverside
Also remember that the sail is pulling you not just sideways but also forward. That forward pull can cause weather helm if its vector is "outside" the center of lateral resistance. For example, on a reach, when the sail is eased out and pulling forward, the center of effort the sail is basically just pulling the leeward side of the boat forward, which will tend to round you up.

Also, as the boat heels more that center of effort goes, with the mast, further outside the boat, and the mast becomes a lever trying to turn the boat up.
This..
pinwheel.en.gif


ALL sailboats want to spin like this. If you where heeled over more rotation...more weather helm.
 
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Joe

Jun 1, 2004
6,810
Catalina 27 Mission Bay, San Diego
Sounds like you are experiencing a broach....,.the headsail becomes quickly overpowered, the boat heels and wants to round up quickly.
 
Jun 25, 2004
604
Corsair F24 Mk1 003 San Francisco Bay, CA
How much were you heeling In the gusts? Heeling always produces a moment arm around the center of lateral resistance underwater that torques the bow into the wind.
 
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Nov 26, 2012
1,106
Hunter 34 Berkeley
It’s because of heel. The center of force on the sail moves out laterally with the rig when the boat heels over. That puts the moment rotating boat into the wind. My boat does this especially with the Genoa where the center of force is not that far forward to begin with.
 
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Sep 30, 2013
2,909
1988 Catalina 22 central Florida
How much were you heeling In the gusts? Heeling always produces a moment arm around the center of lateral resistance underwater that torques the bow into the wind.
The wind was building, so we were gradually falling off from close hauled to almost a beam reach. We had been paralleling the coast, trying to point high enough to stay off it, but losing. So there was a good bit of heeling involved, and eventually we had to drop the sail and motor. But it was pretty rough and we already had one seasick crew, so we wanted to keep the better motion of sailing as long as possible.

The explanations above make perfect sense. I get it now. Many thanks to everyone!! :beer:
 

Brian D

Moderator
Feb 17, 2006
4,553
Lancer 27PS MCB Camp Pendleton KF6BL
To show how dumb I really am, but I thought all boats were designed with a tad bit of weather helm built in. I swear I read that somewhere many years ago.
 
Nov 26, 2012
1,106
Hunter 34 Berkeley
To show how dumb I really am, but I thought all boats were designed with a tad bit of weather helm built in. I swear I read that somewhere many years ago.
This is true. They are designed to have a little weather helm with both sails up, i.e. the center of force in the sails is aft of the center of resistance of the keel. When raising just the headsail, however, the center of force is more forward usually forward of the center of resistance of the keel. BUT. When the boat heels you add a third dimension which is the forward force of the sail acting off center and wanting to rotate the boat back to windward.
 
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May 25, 2012
2,193
john alden caravelle 42 sturgeon bay, wis
brian, you are not dumb, the healing of a mono hull is the nature of the design and designed into it. the force of effort, which is up in center of the sails, moves farther and farther off centerline of the hull giving increasing weather helm with ever more healing. so what you read would be correct. weather vane-ing the sail plan to balance the helm is another part of the puzzle as well. helmsmanship is another factor as well. seeing a puff coming and countering the forces before they change momentum forces, say adding a little wheel a split second before the puff hits will keep weather helm in check better.
like playing chess, there are many things to consider, to play well :)
 
May 17, 2004
2,007
Beneteau Oceanis 37 LE Havre de Grace
As the others have said, yes, weather helm is usually built in. Helps in 2 ways - on smaller boats it's a bit of a safety feature that if control is lost the boat will round up and depower. Also, having the rudder turned to leeward just a few degrees adds lift which reduces leeway.
 
Sep 19, 2016
169
Hunter 23.5 Sebastian, FL
I've recently experienced the same problem on my Caliber 33 flying just a 150 genoa in 15 to 20knts on the beam. Is there any way to address it? Had to roll in 1/3 of the genoa to keep from rounding up. I feel like the boat should be able to handle more than this. Is it just too much sail for this boat?
 
May 17, 2004
2,007
Beneteau Oceanis 37 LE Havre de Grace
I've recently experienced the same problem on my Caliber 33 flying just a 150 genoa in 15 to 20knts on the beam. Is there any way to address it? Had to roll in 1/3 of the genoa to keep from rounding up. I feel like the boat should be able to handle more than this. Is it just too much sail for this boat?
A 150 in 15 to 20 knots is probably pushing the edge a bit. Do you know if the sail is original or otherwise worn? As sails age they stretch and the draft moves aft, increasing healing and weather helm.
 
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Sep 19, 2016
169
Hunter 23.5 Sebastian, FL
Yes. The sail is original and likely contributed. I guess I'll start by trading down to a newer 120. Alternately considering a jib on a solent stay then putting a code zero on the forestay.
 
Oct 19, 2017
5,213
O'Day 19 Littleton, NH
I feel like the boat should be able to handle more than this. Is it just too much sail for this boat?
How does your rig tuning look under 20 knots of wind? Are your lee turnbuckles too loose? That could let your mast lean outboard farther than necessary, do you have the right amount of rake? That could change the center of effort a few inches forward or aft.
Everyone talks about the center of effort (CE) vs the center of lateral resistance (CLR), when heeling, there is also the center of longitudinal resistance that goes to windward. That is what the above comments about lever arms and such are saying. The forward drive over the rearward resistance of the keel. The heavy leeward steering of the helm causes it to get even more exaggerated as the rudder angles the below water form up and windward at the same time.
I would solve the problem by reefing the headsail and setting a reefed main. This reduces sail aloft while keeping the balance and sail area as close to the design specs as possible.

-Will (Dragonfly)
 
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Jun 25, 2004
604
Corsair F24 Mk1 003 San Francisco Bay, CA
This is true. They are designed to have a little weather helm with both sails up, i.e. the center of force in the sails is aft of the center of resistance of the keel. When raising just the headsail, however, the center of force is more forward usually forward of the center of resistance of the keel. BUT. When the boat heels you add a third dimension which is the forward force of the sail acting off center and wanting to rotate the boat back to windward.
Actually, the geometric center of effort (geometric centroid) of the sail plan is designed so that it is forward of the geometric center of lateral resistance (geometric centroid) of the underwater profile. The term for this is called “lead”.

The lead is built into the design so that the helm will be balanced when the boat has some heel.
 
Feb 14, 2014
4,099
Hunter 430 Saba Waveland, MS
The wind was building
So there was a good bit of heeling involved, and eventually we had to drop the sail and motor. But it was pretty rough
Good discussion on the Sails.

But...

When your boat is in even moderate seas, you must add the Rudder design to the mix.

Since your Rudder can be partially exposed, as you heel on the downside of a wave, you will experience some variation in your weather helm.
Jim...
 
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