Problem with lee helm

This is good stuff latestarter ... thank you!

 

I agree with Dennis that, if it can be done readily given the mast step & partners design, I'd try to rake the mast as step #1.

Looking at the boat, I would attribute the lee helm largely to the length of the bowsprit, and how far forward it brings the outer forestay. So my suggestion for step #2 is to bring the forestay (and martingale) aft on the bowsprit (your option whether to shorten the bowsprit or leave it current length).

The third measure I would suggest is to get a roachy mainsail with at least one full length upper batten. Have the mainsail cut on the full side, and have any new jib you purchase made flatter than typical. The full length batten(s) will press on the the mast at the luff end, so if you don't have batt-cars, make sure you have some sort of slider at this location that will not jam.

There are a couple approaches you can take to helping such a mainsail if it hits the backstay when coming about. One is a backstay kicker. Another is to suspend length of UV resistant PVC conduit around the backstay with lightweight rope from the masthead so it flies at the appropriate height. Steve Dashew has done this and written about it. It works.

There's a possibility that hull shape is a contributing factor, and there are (not entirely scientific, but empirically workable) methods for beginning to quantify this if you have a lines drawing. Hull mods are not a direction I would suggest to remedy lee helm, though (except to note that re-fairing of the keel can occasionally affect balance).

 

I am not convinced that you can compare the angle of pull from the fairlead to that of towing the boat from that same position via an external force (eg a towboat). You are right in implying that if you tried to tow the boat with another boat using a line connected to the rear of your boat it would have a tendency to want to swap ends. But this is not comparable to the boat being towed by a force which comes from the boat itself via sail that is connected to other areas of the boat internally (Ie forestay and mast). No matter where the attachment points are the sail will still pull from its COE. However if the fairlead is lead to a position that is not optimal for sail shape you might inadvertently cause the COE of that sail to shift forward due to a less than optimal sail shape.

Just by eyeballing the sheeting angle of your new jib I think that you have moved the sheeting angle too far forward. The leach will be too tight and the foot will be loose, making a sail shape that has more of a tendency catch and hold the air, pushing the front of your boat downwind rather than a tendency to divert the air rearward which would be happing if the foot was tighter and the leach was looser.

Sorry for my lack of fancy terms. I'm no NA, but I would try moving the sheeting angle back. Just throwing it out there. Take what I say with a grain of salt. You could just temporarily fit a few blocks further aft to see what effect this has. My eyballometer has the optimal sheeting point around your rear most shroud. I think some testing would be worth the effort and it wouldn't take a lot to try.

 

Please note, this IS a trim problem.

The guy at Doyle who told you the lead through clew should intersect the midpoint of the luff is an idiot and shoud be fired, or at least you should know to never buy a sail or get advice from them again. Anyone who is giving this kind of advice should know the line should intersect close to 40% of the way up the luff. Note the green lines on the attached sketch. Your old Yankee intersects close to the 40% mark. Your new sail/lead isn't close.

The lead for the new sail should be closer to the upper shroud chainplate, as shown by the purple line in the attached sketch.

If you think the sail looks right with the lead a couple of feet too far forward you need to take some sailing lessons. Basically when you sheet in the sail to that lead you have a big airbrake.

I can't believe some of the advice/comments given/made on this thread. The blind leading the blind.

 

So I take it you are agreeing with my last post Paul? I didn't actually measure it like you did so my guess was further aft than optimal. I admit I didn't know the 40% rule, but just from sailing experience the sheet trimming angle looked too far forward after seeing the picture. I normally just set the point by looking at the respective tightness of the foot and leach and adjust accordingly until the correct setting is reached.

 

Yes, you saw what is very evident for anyone who knows how to sail. Measuring is not required to see when a lead is far too far forward (or aft). The lead problem is magnified by the higher aspect ratio of the sail, compared to say a 150% genoa.

One designer who is very famous for his cruising designs and boat reviews has openly stated that putting adjustable leads on a cruising boat is next to useless, since most people who buy those types of boats have no idea where the lead should go and the lead would always be wrong anyway.

Judging from this thread I fear he is right.

 

I have almost no racing experience. But I like to get the best out of a cruising boat.

Well in that case, I am fortunate that all the boats I own or sail on have had adjustable lead angles. I would certainly want this feature on any boat I own. When using cheap secondhand sails with different sailplans to the original, adjusting the points is essential for decent performance. Usually swapping a no1 for a no2 or 3 in increasing wind conditions requires a change in the point with the sails I have available.

 

Stephen Ditmore,
The BCC as it was first built had a little to much weather helm. Over the years most people have adjusted the designed mast rack out of her to compensate for this. If I want I can just go back to the yankee I have and solve this problem. Which I may just have to do.

I made some changes for my new jib in the CoE and CoA to move the CoA down and increase overlap with the stays'l. It appears that I past a tipping point and introduced the lee helm. The tail will be told when I take her out with both sails and compare them side by side as it were.

I started this thread so I could get some thoughtful input as to the causes and theory's as why this has happened.

DennisRB,
I agree that if the sail were not properly trimmed I could introduce all kinds of problems. I posted the sail plan for the purposes of comparing CoE, CoA and relative sheet lead of the two sails. If you had read my post, as it seems some people haven't. I stated the the drawing was not entirely accurate and the sheet lead came to a point aft of the forward shroud.

I have always trimmed my sails by observing the luff. It needs to luff evenly from top to bottom to be trimmed correctly. Or watch tell tails if one has them so they all break at the same time from head to tack.

I added the reference to Doyle as a confirmation to my normal method of trimming stated above, for two reasons.
1) I had never heard of their method of determine the trim point. Only after months of sailing with the new jib did I actually go up on deck, lay on my back and check the accuracy of their trim strip. I found it lined up perfectly with my visual trimming of the sail.
2) I talked to a designer at Doyle that had worked on the last Americas Cup sails. I would take that resume over some of the self proclaimed experts I run into on these forums from time to time.

Paul B,
I find your comments pompous and irrelevant. I know how to sail, as well as most anybody. This is not a trim problem as you seem to take such relish in.

I would like to again thank all those who have contributed. Even if not technically correct, they can open up paths of thought that can be very useful.

Gary

 

Random thought here.

Besides the new sail's COE being different, could it be the new sail simply providing significantly more power?

Despite the small change it the location of the COE, more thrust acting thru that sail's COE could shift the overall sail plan's COE further forward than one would suspect. Especially if you are basing expected performance on another, perhaps less efficient, sail.

If so, shifting the stay or mast rake aft some amount seems the best option.

And sorry about the sampson post suggestion. I just glanced through your websites first page pics briefly and totally missed the correct sail plan.

 

Since North Sails was the supplier to both of the boats in the last A Cup maybe you should question this claim.

If this person told you to line up the lead and clew with a line through the center of the luff then they are ignorant, regardless of what their resume says. This is a very easy thing for you to investigate (40% vs 50% of luff). Of course if you can't admit you have a problem then go on believing whatever you want.

You obviously do not know how to sail "as well as almost anybody", based on the things you have said in this thread. You have some nerve calling anyone else pompous.

This lack of self awareness is probably your biggest problem.

 

Allways so understanding and emphatic

 

Paul B

And your Lack of humility makes it impossible for me to take you seriously.

 

I hope you don't come to the correct solution, just to spite me.

Facts are facts, regardless of my lack of humility.

 

People, people, why does an exchange of insults and accusations of incompetence always seem to spoil a perfectly good thread? We have lost many helpful and skilled members in recent months due to precisely this kind of thing.

By far the best response to an incorrect statement is a simple correction. It is possible to agree to disagree without being disagreeable. There is also the option to unsubscribe, which I may do if the posts deteriorate further. Maybe this thread has done all it can be expected to.

 

I agree ancient kayaker. This is my first time on this forum. I am about to abandon this thread. This is not a sail trim problem. And I do not want or need a discussion about it. I am trying to understand how all these forces work together to create weather/lee helm.

This is a complex interaction of many different forces. Most of which one can not quantify.

Hey GTO, now that is something I have been thinking about. The new sail has a beautiful air foil shape when set and pulling. The old sail (its a long story) seems to have been built for reaching, and is not as efficient for going to weather. Its one of the reason I had a new sail made.

I'm starting to think this lee helm problem is the result of a number of small factors which are adding up to the lee helm. Many of the BCC owners over the years have taken the designed mast rake out of the boat to ease the heavy weather helm. Shanti has had this done. Maybe its a case of having reached a tipping point in the balance of the rig and I have past that. Going over to the dark side.

Ancient Kayaker, I think you are also correct that this thread has run it's course for now. I need to take both sails for a sail. Then report back at a later date.

Thanks everyone, there has been some great input and I appreciate it!