Impact of Design Changes

I want to preface the following messages by saying I am not an engineer or naval architect, nor do I claim to be.

When people tell me the relative merits of the current and proposed rudder design, I want to know more than the differences between the designs. I want to know how and why these differences exist. So, I ask lots of questions.

The purpose of this and the subsequent messages are to pass on information that was provided to me that hopefully clarifies how and why certain changes in the rudder's design impact its performance. Much of this information came through email conversations with several members of the class.

In this thread, the first message is an email I wrote. It was my best attempt to summarize a very long chain of emails that included several people, but was mostly between Rick Whitehurst and myself. That message was sent to Paul Foerster to get his insight and feedback.

Rick and Paul are aware that I thought the information they provided would be beneficial to share with others. They granted me permission to post this to the forum. Any misrepresentation of content or facts was not intended. In such a case, I apologize in advance, and truly hope Rick, Paul or another individual will contribute to and clarify the points that have been made here.
 
I wrote:
"My take away from the conversations was that the new rudder blade will not change the amount of force necessary to keep the boat flat at any given wind speed. Based on fitness, weight, height and hiking style a person has a maximum amount of force they can apply to keep the boat level. There will be a point at which the forces applied by the breeze on the sail will exceed the possible opposing force an individual is capable of. Once that point is reached, as the breeze increases the boat will heel and there will more weather helm. In order to compensate for the boat's natural tendency to round up, sailors need to pull on the tiller. The more vertical rudder design will make this easier and more effective because there will be more leverage on the tiller and more of the rudder's surface in the water. In addition, a more vertical design will reduce the current design's tendency to stall at higher heeling angles.

Changing the rudder's angle and design may broaden the competitive weight range of the boat. However, it does not impact the driving force of the sail or the opposing force that is created by hiking. Therefore, it will not impact a sailors ability to keep the boat flat in a breeze. Instead it simply reduces the amount a sailor has to fight weather helm once the boat is overpowered and reduces the instances of the rudder stalling. This will make the boat easier and safer to sail while not flat. In turn, that will probably allow a person that does not exert as much force hiking to be more competitive in a breeze because they can concentrate on tactics and will not be hurt by the rudder stalling or acting like a brake upwind. But, they will still be giving up ground upwind because the boat is not flat."

Paul responded:
"1. It will not change the amount of force required to keep the boat flat.
2. Boat will still have more weather helm as the boat heels ( just much less than old rudder)
3. Boat will still have the same tendency to round up, but the pull on the tiller will be much less to stop the boat from rounding up.
4. As for stalling less at higher speeds, in my experience it does not depend on how verticle the rudder is. It depends more on the shape of the rudder. We had verticle rudders in the 470, but the thinner rudders stalled before the thick rudders stalled.
5. The modified rudder goes deeper in the water, so you will maintain control at higher heeling angles.
6. Most centerboard boats have more verticle rudders than the sunfish, but all centerboard boats are faster when sailed flat (except for scows). Examples, Laser, 470, FD, V-15, Finn, 49er"
 
I just want to borrow a quote from Bill McLaughlin that was put in another thread and is relevant to this conversation. Bill said "I suspect the testers are experiencing a lighter pull on the tiller because the center of effort of the new design is closer to the pintle, thereby reducing the lever arm. Still, if you are dragging the rudder because of weather helm, you are still making the same correction regardless of the rudder design, you just don't feel it."

I believe this same point was made by Richard Whitehurst. Hopefully he will confirm or clarify.

I would encourage people to look at the remainder of Bill's contributions here under the name wlmlaw.
 
Derrick and Paul,

You both seems to agree that the new rudder is trying to solve a problem that is not
the result of the old rudder but the result of some sailors failing to keep the boat
at the proper sailing angle in heavy going. When they can not "keep it up" or heal in
the puffs, the weather helm increases. Because the old rudder's center of effort is
back from the transom, the pull on the tiller becomes noticeable. As an asside, I
never noticed the tiller pull as a major effort when compared to the sheet and the
exersion of hiking. But in any case, once the sailor starts to carry helm (rudder drag), this is not good in terms of speed, and if it causes stalling, is not good in terms of turning
force. (control) Changing the rudder to make it easier to steer while carrying helm
does not "solve" the problem, it only hides the problem. The good heavy air sailors
(which include many under 175 pounds) have learned to adjust their gooseneck, jens, vang, mainsheet and outhauls to reduce power by making the sail flater, and most
importantly moving the center of effort of the sail forward with the gooseneck. (moving the gooseneck back) That is consistent with almost all dinghys. The idea is to keep it at
the correct angle by hiking with maximum effect, then reducing the "power" of the sail
(camber) when the wind increases. If you are carrying excess helm, something is wrong and a different design for the rudder is not going to fix it. It is certainly not going to make
the poor hikers or those who are "too light" competitive. I would suggest that the class (fellow competitors, teachers and trainers) make it more clear what the rig controls do, and how to adjust for high winds when healing force overcomes hiking force. Besides the rig, steering technique is also important. Feathering into puffs, keeping the mainsheet tight to bend the spar and keep the sail flat, and setting up the vang to keep the spar bent in extreme conditions when the main must be eased, are a few.

I personally never considered the current rudder design as so fundimentally flawed that it required a rework. Control, balance and feel seem fine even in force 5 conditions. The rudder also has the advantage of not picking up weeds. The new plastic model is very impressive in its shape and finish but the wood rudders can be fixed up quite nicely as well. I just do not see the advantage of a change that would appear to challenge the one design nature of the class. The board had to be changed and made one design, the rudder has always been so. (Ignoring the real old design for the sake of argument)

In short, the proper setup and adjustment of the jens rig, gooseneck and vang will do more to help the lighter or poor hiker than any rudder design. In my experience the sailors with problems in heavy air do not have a clue about balance and sail controls, which is the source of weather helm and control issues. Solve that and rudder "problems" will go away.

Bill McLaughlin 77721
 
The current class rules have all competitors using the same basic rudder design, and since as many submissions have noted, the rudder is not going to prevent weather helm, why change it? The last thing you want to do is mask the fact that you have the helm cranked over 20 degrees, and are making more leeway that headway. Every effort needs to be made to keep the tiller within a few degrees of centered, As said earlier, that is done through hiking out, and/or depowering the rig. Look how easy it is to numb your senses to excessive helm when you have a 6 ft. diameter wheel, that is why people either mark the wheel of the tiller post, so that they have some way to know how much helm they really have.
 
I agree with Derek and Paul, but would add that Paul’s points are closely related and interactive, particularly so for our beloved Sunfish.

Why is the Sunfish credo ‘sail it flat’ so important? True, it is a general principle that stems from the physics involved for all centerboard boats. But the Sunfish hull shape and shallow rudder ‘sweet spot’ combine to make flat sailing downright critical. The many things we do to keep the boat flat (jens, gooseneck, vang, outhaul, etc.) are so important because they stem from what happens when we don’t keep it flat, and THAT is a function, among other things, of the current rudder design.

Beyond a certain low heel angle, about 12 degrees, the Sunfish starts to exhibit a dramatic decrease in steering ability. At 12 degrees, the leeward bottom of the boat is parallel with the water’s surface. Beyond that point, the chine digs in, which increases weather helm but also starts to lift the stern vertically. (This lifting effect is pronounced compared to many other boats.) The problem is aggravated by the current rudder angle, almost 45 degrees from vertical. A greater proportion of the rudder surface is decreased than with a more vertical rudder. On top of that, the lateral center of the rudder moves farther aft, increasing the force needed on the tiller. More rudder force is needed at a time when less rudder surface is available. The helmsman must use even greater rudder angles to keep the boat flying straight.

These effects combine dramatically with just small additional increases in heel angle. The rudder is soon acting as much as a break as it is a rudder. The sailors who just can’t quite keep the boat flat enough soon disappear to the back of the fleet. It doesn’t take much and it doesn’t have to be this way.

Some sailors who have tested the new rudder are a little confused. I was at first. Why isn’t the new rudder, with less drag, faster than the current rudder? I think the error here is to assume that there is less drag. A deeper rudder probably increases drag and the foil shape probably decreases drag. Overall, there is probably little change in drag (except as noted in the paragraphs above).

There is also no change in ‘weather helm’. What has changed is the force needed on the tiller to control that helm. The helm is still there, but with greater leverage you just don’t feel it as much.

I once broke my tiller off about a foot up from the rudder at the start of a regional regatta. I jammed the jagged edge into the bottom of my boot and soldiered on in about 8 to 10 knots of wind, steering with one leg or the other. It felt just like straight leg lifts, only someone was pushing down at the other end. It just about killed me. I needed about 4 times as much force on the tiller to steer. Between races, I lashed on the broken off section to get about 2.5 feet of tiller and a hiking stick - MUCH better.

Hey! If the rudder is changed, you could always shorten your tiller to compensate. That might make you feel right at home with a ‘comfortable tug’ on the tiller.

What do we get with the new rudder (or rudder angle)?
1. Less tiller force is required to control weather helm (the rudder’s lateral center is moved forward). This is just like my example of increasing the length of my broken tiller from 1 foot to 2.5 feet; only we’re doing this on the rudder side of things.
2. Reduced onset of increased drag and/or stalling effects as heel angle increases (the rudder’s lateral center is lower). This change, in my view, is the more important one. It will keep the younglings in the game longer and make to boat easier, safer, and more fun to sail.

You will still need to feather up, sheet in/out, hike harder to get ahead in higher wind conditions, puffs and lifts. A flat boat is still faster. Those at a disadvantage won’t be penalized as early or as severely with this rudder change. They will still need to generate a sufficient ‘power to weight’ ratio, as we all do, to remain competitive. This change will give them a better shot at it (less rudder breaking action). The reduced onset of stalling will also help keep them out of irons.

I would like to hear from those who might disagree regarding the technical aspects of the current and proposed rudder designs. Bring it on! Everyone needs a complete and accurate picture. Some disagreements might be generated from different definitions of ‘weather helm’ vs. ‘force on the tiller’. Anything you can add to help clarify the picture for non-geek types is always welcome.

I will reserve my thoughts on other pro’s and con’s for another posting.

Finally, don’t confuse me with my kid brother Tom. He is truly carrying the load on this one, and I am free to throw rocks from the sidelines.
 
I'm surprised the Sunfish class has lasted from the 50's with all the weatherhelm caused by the incorrect angle of the rudder.

If the class is going to make a change to the rudder shape and position why not just use a laser rudder. This would allow LP to keep the cost down ($161.39) and would allow the Sunfish to have the more vertical rudder that the users are looking for. I look at the propsosed rudder shape and this looks like a throw back to the orginal Sunfish rudder from the 50's. Using the laser rudder would allow sailors to get used to this shape as they progress from Sunfish to Lasers.
 
I'm surprised the Sunfish class has lasted from the 50's with all the weatherhelm caused by the incorrect angle of the rudder.

If the class is going to make a change to the rudder shape and position why not just use a laser rudder. This would allow LP to keep the cost down ($161.39) and would allow the Sunfish to have the more vertical rudder that the users are looking for. I look at the propsosed rudder shape and this looks like a throw back to the orginal Sunfish rudder from the 50's. Using the laser rudder would allow sailors to get used to this shape as they progress from Sunfish to Lasers.

When the new rudder project was started, I first made a list of requirements. One requirement was that it needed to operate with the existing rudder/tiller system so that only the blade would need to be replaced and not the entire rudder/tiller assembly. These requirements had an impact on the final design. As to how it looks, comes from the design of the daggerboard. There were many designs presented including existing Vanguard ( now Laser Performance ) blades but this one meet all the requirements.

Another consideration was that most sailors did not want another plastic blade like the current sunfish daggerboard or those on the Laser. They are not very durable, very hard to repair and it was desired to have a FRP ( Fiberglass Reinforced Plastic ) blade instead. These are very durable, easy to repair and require very little maintenance. The material of choice will be up to LP although this is preferred.

TW
 
Wow, i think you guys need to get your heads out of the sand and look at the bigger picture . Is the new proposed rudder aimed (a)solely for the benefit of current owners or (b) is the hope that it will also stimulate interest in the class from sailors outside the class. If the answer is "a" then good luck; from the response on this forum and the general apathy amongst current members i dont think it will make a blind bit of difference whichever way the vote goes.The class will remain insular, newcomers will be put off and numbers will continue to diminish.

If on the other hand the answer is "a" and "b" then for god sake do things properly. Have a decent rudder which is vertical not some compromised version of the existing monstrosity. Furthermore the existing mainsheet system and sail controls should be modified in a similar fashion to the Laser

We live in the 21st century, with numerous designs competeing for marketshare if the boat is to continue its appeal it should be marketed to reflect this not some nostalgic dinosaur.

And for those people who bemoan the cost, look upon it as a cheap opportunity to enhance your beloved boat without the expense of buying a new one. As for those citing the one design nature of the class ;well so mis the Laser and it certainly didnt do that class any harm.

Two of lasers biggest sellers in Europe over the last 30 years have been the Laser standard and the Dart Catamaran. The former introduced new sail controls in the face of increased competition back in 2001 and immediately opened up a whole new market to woman and youths. There was no increase in performance but it just became more manageable and a whole nicer sailing experience.. The boat continues to sell in huge numbers.

On the other hand the members of the Dart association continually disregarded calls for change. The boat clearly needed improved rudders ,mainsheet and sail controls to ward off competition from newer more efficient classes. They were never approved and Europes largest Catamaran class (which once boasted over 300 boats at a world championship) is now all but dead , no longer built by Laser and only attracting a few old regulars. How different this story may have been if the class had been more open to evoloution as was the Laser

I think there is a great opportunity to breathe new life into the class; i only hope its not wasted !!!
 
Wow, i think you guys need to get your heads out of the sand and look at the bigger picture . Is the new proposed rudder aimed (a)solely for the benefit of current owners or (b) is the hope that it will also stimulate interest in the class from sailors outside the class. If the answer is "a" then good luck; from the response on this forum and the general apathy amongst current members i dont think it will make a blind bit of difference whichever way the vote goes.The class will remain insular, newcomers will be put off and numbers will continue to diminish.

If on the other hand the answer is "a" and "b" then for god sake do things properly. Have a decent rudder which is vertical not some compromised version of the existing monstrosity. Furthermore the existing mainsheet system and sail controls should be modified in a similar fashion to the Laser

We live in the 21st century, with numerous designs competeing for marketshare if the boat is to continue its appeal it should be marketed to reflect this not some nostalgic dinosaur.

And for those people who bemoan the cost, look upon it as a cheap opportunity to enhance your beloved boat without the expense of buying a new one. As for those citing the one design nature of the class ;well so mis the Laser and it certainly didnt do that class any harm.

Two of lasers biggest sellers in Europe over the last 30 years have been the Laser standard and the Dart Catamaran. The former introduced new sail controls in the face of increased competition back in 2001 and immediately opened up a whole new market to woman and youths. There was no increase in performance but it just became more manageable and a whole nicer sailing experience.. The boat continues to sell in huge numbers.

On the other hand the members of the Dart association continually disregarded calls for change. The boat clearly needed improved rudders ,mainsheet and sail controls to ward off competition from newer more efficient classes. They were never approved and Europes largest Catamaran class (which once boasted over 300 boats at a world championship) is now all but dead , no longer built by Laser and only attracting a few old regulars. How different this story may have been if the class had been more open to evoloution as was the Laser

I think there is a great opportunity to breathe new life into the class; i only hope its not wasted !!!

I have to admit that the project was to achieve both A and B if possible.

As for a compromise to some extent yes it is but if it didn't solve the issue than some of the requirements would also have to change. This was not the case and the final design is good. It is truly a different rudder but does comes with some degree of change with the one-design aspect and the cost being the primary concerns. The intent was to minimize the impact of A while achieve B. It is our hope that most people see the need to progress with this enhancement.

TW
 
A GRP daggerboard and rudder, now there's a good idea, your absolutely right the new foils are not up to much abuse. As for the new rudder design, if it's production is dependent on a consensus being reached it'll never happen. This forum has generated feed back from a tiny percentage of those that own Sunfish so one might assume the issue is not that important to most. What exactly is LP waiting for? X number of owners to pre order the new foil? Short of polling all the Sunfish fleets how does LP make it's decision on going into production or not? Even if it appears there is sufficient interest LP is still gambling, as simply saying you think it's a great idea ain't the same as money in the bank.
 
Example - Using the same size blade area, one rudder in the old position, one rudder in the new position.

The new rudder position will have less weather helm as the pivot point has been moved closer to the center pressure on the boat.

The new rudder position will have to be turned more than the old rudder position for the same amount of turn, as the pivot point has been moved closer to the center pressure on the boat. which will cause more drag.

In this example the new rudder position will have more drag than the old rudder position for the same size blade. More drag will slow the boat down. If the new blade has more area than the current blade, this will cause even more drag and slow the boat even more.

Since, one design races are won with slight speed differences; I will stick with my old rudder position and put up with some weather helm to be faster.
 
Example - Using the same size blade area, one rudder in the old position, one rudder in the new position.

The new rudder position will have less weather helm as the pivot point has been moved closer to the center pressure on the boat.

The new rudder position will have to be turned more than the old rudder position for the same amount of turn, as the pivot point has been moved closer to the center pressure on the boat. which will cause more drag.

In this example the new rudder position will have more drag than the old rudder position for the same size blade. More drag will slow the boat down. If the new blade has more area than the current blade, this will cause even more drag and slow the boat even more.

Since, one design races are won with slight speed differences; I will stick with my old rudder position and put up with some weather helm to be faster.

Please provide your reference material on your statement. "as the pivot point has been moved closer to the center pressure on the boat. which will cause more drag"

1) Drag is proportionate to the amount of surface area.
2) Lift is greater with a thicker blade but has more drag.
3) Thicker blades stall at a greater angle of attack than thinner blades.

I believe the distance you reference ( center pressure ) is the distance between the rudder and centerboard. This has nothing to do with drag but leverage. Rudders in earlier design were skegs on the end of keels. Modern design found it better to have two separate lifting surfaces ( a keel & rudder ). By increasing the distance between these two surfaces also increased the leverage ( quicker to turn ).


Please see page 115 in the following link:

http://books.google.com/books?id=Gl...num=7#v=onepage&q=rudder design stall&f=false
TW
 
By increasing the distance between these two surfaces also increased the leverage ( quicker to turn ).

Correct, the old blade position is greater than the more vertical position, the old blade is ( quicker to turn).
 
Tom, firstly i would like to applaud the time and effort you have obviously given to this project ; its obviously a thankless task and you are never going to appease everyone. However i do think the adoption of the proposed rudder in its current format would be a mistake. Whilst it is undoubtably an improvement on the current rudder it still falls someway below the design level of all other classes; off the top of my head i can only think of the Optimist (which has far superior blades) that doesnt use a vertical blade . If anyone doubts the benefit of a vertical blade just look at the time and effort top Laser sailors spend ensuring their rudder is locked into a solid position as far down as it will go. I understand under the present design you are governed by retaining the existing stock in an effort to minimise costs to existing owners; however its design is almost as flawed as the blade itself. So rather than having a design which is still a compromise why not do things properly and have a new stock (without all the movement of the old one) and blade. Im not sure at the likely cost of the proposed rudder but i feel pretty certain ( using the Laser price of 290 dollars for a complete new rudder system) that a redsigned stock and blade wouldnt be that much more !!
 
The new(er) style Opti Blades are more or less vertical and do not allow the kids to scull (as much). Opti parents who have kids that race do not blink at dropping 500-700 bux for a new set of blades. Being a female under 140 pounds I am all for the new rudder change. I learned to sail 5 years ago and am almost 50. Sunfish is really realistically the only dinghy I can compete in. If you want to race, get the new rudder.My two cents....
 
Example - Using the same size blade area, one rudder in the old position, one rudder in the new position.

The new rudder position will have less weather helm as the pivot point has been moved closer to the center pressure on the boat.

The new rudder position will have to be turned more than the old rudder position for the same amount of turn, as the pivot point has been moved closer to the center pressure on the boat. which will cause more drag.

In this example the new rudder position will have more drag than the old rudder position for the same size blade. More drag will slow the boat down. If the new blade has more area than the current blade, this will cause even more drag and slow the boat even more.

Since, one design races are won with slight speed differences; I will stick with my old rudder position and put up with some weather helm to be faster.

Don't be confused with how a boat turns on its axis and the pressures on a rudder. They are two different issues.
The current Sunfish rudder is an unbalanced design. It is an unbalance rudder because the CLR ( center of lateral resistance ) is aft of its pivot point of the rudder. This is what determines most of the leverage required to steer. It’s always there but as the pressures increase as the wind increase it becomes more apparent. Raking the rudder forward does two things to help minimize the leverage required to steer.
1) It moves the CLR forward and closer to the pivot point .
2) It also moves the CLR lower in the water so there is more rudder to steer with as the boat heels.

Both the above help to minimize the amount of torque required to steer. This is what is being addressed in the new rudder design. There are other improvements but this is the biggest impact.

Bill McLaughlin’s comment to move the CE ( Center of Effort of the rig ) forward fixes this but not so. It only helps to reduce the amount of helm but doesn’t make a balanced rudder. He is not wrong in his statement and moving the CE is still required to balance the boat as wind increases.

Anyone what to know more on the other improvement in the design just ask.

TW [email protected]
 
The proposed rudder design changes the pivot point distance between the rudder and centerboard. The proposed rudder position is decreasing this distance. Distance is what makes the boat turn, the bigger the distance the faster it will turn. The bigger the distance the less movement of the tiller to steer the boat.

So if you have a boat with the current and another boat with the proposed and they do the same maneuver the skipper with the proposed rudder will have to move the tiller in a greater arch to be able to turn the boat as fast as current blade. From what I have read, you try not to steer a lot as this is drag.
 
The proposed rudder design changes the pivot point distance between the rudder and centerboard. YES

The proposed rudder position is decreasing this distance. YES,

You have to look at the percentages gained and or loss. The loss in the leverage you’re talking about is extremely small compared to the percentage gained to balance the rudder which is very great. In essence the boat is EAISER turn because there is less torque in turning the rudder. Not that the radius is less. If you want to boat to turn quicker, you can always raise the daggerboard too which is much more efficient but let’s not try to change the subject.

From what I have read, you try not to steer a lot as this is drag. Yes, but we steer a lot in waves.

So if you have a boat with the current and another boat with the proposed and they do the same maneuver the skipper with the proposed rudder will have to move the tiller in a greater arch to be able to turn the boat as fast as current blade. Not likely

There is less leverage required to pull the rudder plus there is more rudder deeper in the water which you’re not considering. Again, when there is a lot of pressure on the rudder ( higher winds ) it is very difficult to steer with the current rudder. Just try doing a 360 in 15+ not easy!

So lets’s talk about drag. This too has an effect on the angle required to turn.

If you steer a lot, you want a thicker blade. A thicker blade ( up 12 % of it cord ) produces more lift in proportion to the gain in drag. Plus, a thicker blade stalls at a greater angle of attack. The new blade is both symmetrical and thicker which are some of the other factors in the design to address lift, drag and stall characteristics. One more note is the aspect ratio is also increase which also decreases drag.

Again, there are many factors and compromises to consider in what is optimal.

I hope this helps!

TW
 
My experience with the Sunfish rudder is described by Bill McLaughlin (wlmlaw), the 4'th post to this thread.

When I first started sailing the Sunfish, I had such a hard time sailing upwind in lots of wind (18mph +). In fact I enjoyed sailing my Laser more since it is so much easier to depower as the conditions change. But I slowly learned over time how to depower the fish, with the techniques Bill described. I love the Jens rig now when the wind is blowing. The only thing is I don't have my Jens rig setup so that I can put it in easy on the water. I have not noticed the weather helm that others talk about. I've looked at my tiller when sailing in strong wind but I do not see it bend.

I have tried a version of the new rudder when it was at Melbourne Yacht Club. Yes it was very easy to steer upwind but I didn't seem to have any speed advantage compared to the other boats. When I tried the prototype rudder the wind conditions were about 10-15 mph.

What worries me now from reading Bill's response is that the new rudder can hide the feeling of the boat so that you won't know when you are over powered so you won't realize that you need to do things to depower. Will you create drag on the rudder without realizing it and slow down? Maybe I'll keep my rudder.... I would hope that the class would not ban the old rudders. But then would there be a time where only the new rudder would be available. I'm not sure I would be happy about that.

Oh, another thing that worries me is when I did the class survey there was a warning that if you sailed were there were a lot of weeds the rudder could pop up. I would not want that. A lot of grass floats in the lagoon where I sail during certain parts of the year and weed maintenance becomes important. It would be fun if the rudder popped up while sailing.
 

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