TP52s

[Mark 42]

...not an Elliptical planform but an elliptical PRESSURE spanwise distribution.

As it turns out... the first half of your statement is not totally correct.
The second half is 100% correct.
It turns out that the easiest way to get an elliptical lift distribution is an elliptical planform.
However, as the aspect ratio increases to ridiculous lengths, the effect becomes
less dramatic. If a sailboat keel had a 50:1 span to chord, the added efficiency
of an elliptical planform would be less dramatic of an improvement.
You could get an elliptical distribution of lift by changing airfoil shape along the span,
but I've not seen that done.

http://www.aiaa.org/content.cfm?page...re97&gID=56733

http://pdf.aiaa.org/getfile.cfm?urlX...AU%20%20%20%0A

Also, in sailplanes, there is a trade of between shape and structural complexity.
A tapered wing is an approximation of an elliptical planform (compared
to constant chord).
This complexity is the reason the Spitfire was one of very few fighter planes
ever to have
an elliptical planform (as well as the fact that L/D efficiency is not really a major design
driver for a fighter plane).
In bombers it probably would have made more sense, but speed of production was more
important at the (WWII) time.
For a sailboat keel, an elliptical planform keel & rudder make a lot of sense.
Actually, it's not an elliptical planform as much as an elliptical chord distribution,
which could have a straight eading edge or trailing edge, or all sorts of
weird swept or scimitar shapes.

[BOATMIK]

Originally Posted by Mark 42

As it turns out... the first half of your statement is not totally correct.
The second half is 100% correct.
It turns out that the easiest way to get an elliptical lift distribution is an elliptical planform.
However, as the aspect ratio increases to ridiculous lengths, the effect becomes
less dramatic. If a sailboat keel had a 50:1 span to chord, the added efficiency
of an elliptical planform would be less dramatic of an improvement.
You could get an elliptical distribution of lift by changing airfoil shape along the span,
but I've not seen that done.

Howdy Mark - thanks for the correction - funny how a misunderstanding (of mine) can hang around for quite a long time!

I was also driven to think (amusingly to me) that fighters and bombers don't generally have to deal with ballast - preferably at the wingtip!

But seriously...

I had a look at the references - couldn't open the first (password) - The second one I was able to look at the first page.

They explicitly state
Minimum induced drag for a thin flat wing is when downwash is constant is reflected in the well known result of an elliptical distribution of chord length and vorticity.

I did have some additional questions which someone may be able to help with.

I know that some glider wings change section partway along. And I'm also wondering how wing flex affects things as it moves the situation away from the 2D case.

Also with sails we are seeing a lot more area jammed up in the head (tip) of many modern sails - is this justifiable from a theory point of view? I imagine one of the differences with sails is the wind speed gradient (lower near the ground and higher further up). And also there is a change in camber and twist too (partly to deal with the wind gradient that "frees" the apparent wind angle.

I've wanted to ask these questions for ages - maybe now is a good time!?!

MIK

[Mark 42]

I think that if you look ath the large headed sails they sort of approximate an elliptical
shape, although at first the AC boats made me think the photographer couldn't fit
the full height of the mainsail in the frame of the viewfinder.

I think your first thought is probably right... the wind gradient has a lot to do with it.
It may be a rules-driven design Maybe mast height is limitted by the rules and
it's one way to get sail area up higher. I wonder if winglets made of lightwieght
materials (e.g. foam & mylar) would help reduce induced drag. Maybe I shouldn't say
it without a copyright first

Sailboat design is something I have followed as an enthusiast over the years...
aircraft (& spacecraft) design is what I studied in college, though my memory is aging and
so is the technology I learned. The basic priciples remain, but new information can
sometimes shed new light on old observations and theories.

These days, I work mainly as a bracket scientist. though I still dabble
in the arts I once learned on occasion...
http://www.youtube.com/watch?v=ljQuQfa98gU

On the flex of the wing - if it is only changing the dihedral it has the effect of rotating
the lift vector (it remains perpendicular to the surface becuase it is mainly pressure).
This will change how much lift there is a bit, and its greatest effect will be on stability.
If it twists the wing, it alters the angle of attack, and will change lift and the local
stall angle (like wing washout) in the twisted areas.
It isn't likely to change the airfoil except on hang gliders and ultralights with semi-rigid
wings (they have ribs, but the ribs flex on some of them). Of course, then you can get
into flaps and spoilers, which change the camber or disrupt the flow... and probably
flex a bit.

On a side note... in NASCAR they have a clever device. It is sort of like a hatch. It lays
flat when the car is moving forward, but deploys like the sploiler on a sailplane when
the car goes backwards to destroy lift and keep the car from becoming airborne.

[mholguin]

Mark, Mik:

Please don't do this. How on earth do you expect Frank to reply to any of these post?

Right now he should be sitting blank face in front of his PC, drooling and scratching his head....

[sailsmall]

When has Frank ever let the small matter of a lack of comprehension stop him from weighing in with a fully formed and lengthily expressed opinion?

[SailDesign]

Originally Posted by sailsmall

When has Frank ever let the small matter of a lack of comprehension stop him from weighing in with a fully formed and lengthily expressed opinion?

PLEASE do not use the words "small" and "lack of comprehension" in the same sentence EVER again if the subject is Migghi

Really! Some people.....

[sailsmall]

sorry

[mighetto]

Originally Posted by SailDesign

PLEASE do not use the words "small" and "lack of comprehension" in the same sentence EVER again if the subject is Migghi

Really! Some people.....

That sounds like a cry for mighetto. Lets liven things up shall we? Hottie is out of town and until Tallahassee Lassie returns I might as well share some information from the Kiss Me Arse Syndicate.

If you grew up in the San Francisco area, as I did, you are exposed to three kinds of sexuality. The transsexuals consider themselves the highest form of sexuality. Not that there is anything wrong with that. They could be correct.

Now there is also an interesting notion among polite society in the USA and I am testing this notion out in Italy as well. That is the notion that all boat owners are rich. In the USA we know this not to be true. A used boat can be had for thousands - even hundreds. Only the very knowledgeable can tell the difference. So there are three kinds of boat owners. There are the poor. There are the rich. And there are those who consider themselves the highest form of owner. These are the transpacific 52 owners. Not that there is anything wrong with that. They could be correct.

I hope some TP 52 owner spit up some Starbucks.

Now pay attention 30 and less somethings because I am not trying to be one of you all. I am trying to impart some wisdom which just might afford you the opportunity of greatness.

There are also three kinds of boat designers. There are sailboat designers, powerboat designers, and there are the kind of designers that consider themselves the highest form of designer. These are the work boat designers. Not that there is anything wrong with that. They are correct.

Frank L. Mighetto

[mighetto]

Ballast, ballast, ballast. Nothing ruins an elliptical platform as quick as considering ballast.

Hence a design that allows moving ballast off the vessel and taking it on when stability requires it is a superior design.

Also as far as elliptical platforms go, have a look at glider design.

You will not find turnbuckles in gliders. I love comparing sailboat design to hang gliders because the technology used in gliders is superior to what is used even on the TP52s. Yet you will find this technology on Macgregors.

Almost none to be seen despite the most cut-throat of competition - sometimes you see a radiused corner. The extreme aspect ratios reduce the induced drag to such an extent that an elliptical tip makes little sense. If it did ... they would be using it.

Bulbs on the end of extreme aspect ratio foils - like on the TP52s - make little sense ... but they are using it. The shape of the bulb has to assume a speed. If the bulb is torpedo shaped the boat will do well in wind that is enough to bring the TP52 at least to hull speed. If the bulb is more rounded then the boat will do better in light wind. These observations apparently are owing to turbulence created at the leading edge of the bulb. In higher winds the additional wetted surface of a thiner longer torpedo shape bulb is offset by less turbulence at the leading edge. But in air craft, the bulbs have been removed from all wing tips. It is well recognized that the weight that use to be kept in the form of fuel tanks on the wing, while giving stability at that point, is better kept in the body of the aircraft. The loss in stability from moving the ballast from the tip of the high aspect foil is gained via better controls, including artificial intelligence (neural networks) which adjust as fast as a human expert to keep the craft level.

These sorts of subjects get quite interesting as you dig a bit deeper - it is very rewarding to assume that there is NO ideal platform or no ideal solution for any physical system. Look at the underlying reasons and dig deep and be sceptical of what is the accepted wisdom.

Macgregor owners and readers of Chapman are taught that the ideal shape is the shape of a ball. Think of an air balloon or a beach ball. This shape is incredible for stability. The next best shape is a cylinder. The idea is that sea state is responded to in a predictable way by these forms so that in gusts the vessel spills wind but the rudder position need not be changed. The TP52s are hardly a balanced design.

I remember how most used to think that Genoas were actually EFFICIENT!!!! Or that a rudder separate from the keel would be impossible to engineer in a safe reliable way.

I love this. Try to think of retractable Genoas which are just as efficient when rolled to jib size. Then think how nice it is to go to 150 size when there isn't enough wind. Now consider the leading edge of the head sail. Little turbulence there. If you think Genoas can not be efficient then you are missing one of the great designs of today. You did not see TP52s put battens in Genoas for nothing. On that matter the vessels are trend setters. The argument that Genoas were invented owing to race rules forgets the real possibility that the leading sail is the sail most suited to power owing to its being in the cleaner air.

Same kind of argument for rudders. If the rudder is on centerline with the fin keel, then the rudder is in turbulence caused by the keel at some speed. This is avoided completely in designs where the rudder is to the side. Do you know the origin of the term port and starboard. The port side of a boat was the side the rudder was not on. How designers ever got to center rudders is something I have not seen researched.

To be skeptical is one thing but it has to be based on some knowledge and be open to correction unlike Mighetto's raving in aid of maintaining his fixed point of view. MIK Hey, look, I'm hijacking Mighettos thread!!!!!

The world is full of reasonable men. Hence we advance only by the efforts of unreasonable men. My point of view stems from boats designed by legals. Read the start of this thread. Lets proceed with the hijacking. Nice post.

[mighetto]

Originally Posted by sailsmall

A lot of respect for the Mac26 on the SA forum:
http://www.sailinganarchy.com/forums...howtopic=57634
Even there [edit: on SA, that is] no one has ever sugjestificated the TP52 for Americas Cup (that I'm aware of). Just one more data point demonstrating the correctivity of Frank's many argumentations.

Apologies four the questionable terminologizing. I'm still struggling with my decoder ring to translatify standard english into Frank speakish. Can't figure out what suddenly went wrong with the darn thing.

How fun. Here is the straight poop. You do not get threads on sailing anarchy regarding any design unless there is something exceptional about the design. You do not get press on a design unless it is a good design. And your design is not labeled a Piece of Crap (POC) unless there is genuine respect for the design.

I can not speak for the M model, but there will never be another sailboat with a production run as impressive as the X model. Over 5000 splashed in less than 7 years.

I also can not speak for Roger Macgregor, but it is refreshing to see him write letters to the editors of sail magazine when authors imply that trailerable sailboats are in any way of lesser design than water bound designs. Thanks so much for the URL.

I do think we deserved a duck the Tuesday before race week. Murrelet arrived about 40 minutes after the cruisers started and still completed the course in front of others in our class. We did employ forth mode. It was critical for getting out of that rotten wind at the sothern most mark. The funnest part was pretending we were going to better a melges 24 who decided to pace us. But then we may have. The Melges made an inordinate number of tacks possibly trying to plane. It was hard to keep track of her. There was no planing on my boat. My apologies to the raft, we had to get back early.

[Mark 42]

Originally Posted by mighetto

...your design is not labeled a Piece of Crap (POC) unless there is genuine respect for the design.
I do think we deserved a duck the Tuesday before race week. Murrelet arrived about 40 minutes after the cruisers started and still completed the course in front of others in our class. We did employ forth mode.

Reality is so far beyond your grasp.
Duck dodge is a SAILBOAT race.
Showing up in an unlimitted hydroplane does not mean you can win a sailboat race.
Using the motor is called CHEATING and is unsportsmanlike.
If you start the engine you should withdraw and get out of the way of the race traffic.
That means go away.
Do not hang in the race area.
Do not make wakes to screw up the racers and the moored boats.

[sailsmall]

Originally Posted by mighetto

Ballast, ballast, ballast. Nothing ruins an elliptical platform as quick as considering ballast.

Hence a design that allows moving ballast off the vessel and taking it on when stability requires it is a superior design.

Also as far as elliptical platforms go, have a look at glider design.

You will not find turnbuckles in gliders. I love comparing sailboat design to hang gliders because the technology used in gliders is superior to what is used even on the TP52s. Yet you will find this technology on Macgregors.

Almost none to be seen despite the most cut-throat of competition - sometimes you see a radiused corner. The extreme aspect ratios reduce the induced drag to such an extent that an elliptical tip makes little sense. If it did ... they would be using it.

Bulbs on the end of extreme aspect ratio foils - like on the TP52s - make little sense ... but they are using it. The shape of the bulb has to assume a speed. If the bulb is torpedo shaped the boat will do well in wind that is enough to bring the TP52 at least to hull speed. If the bulb is more rounded then the boat will do better in light wind. These observations apparently are owing to turbulence created at the leading edge of the bulb. In higher winds the additional wetted surface of a thiner longer torpedo shape bulb is offset by less turbulence at the leading edge. But in air craft, the bulbs have been removed from all wing tips. It is well recognized that the weight that use to be kept in the form of fuel tanks on the wing, while giving stability at that point, is better kept in the body of the aircraft. The loss in stability from moving the ballast from the tip of the high aspect foil is gained via better controls, including artificial intelligence (neural networks) which adjust as fast as a human expert to keep the craft level.

These sorts of subjects get quite interesting as you dig a bit deeper - it is very rewarding to assume that there is NO ideal platform or no ideal solution for any physical system. Look at the underlying reasons and dig deep and be sceptical of what is the accepted wisdom.

Macgregor owners and readers of Chapman are taught that the ideal shape is the shape of a ball. Think of an air balloon or a beach ball. This shape is incredible for stability. The next best shape is a cylinder. The idea is that sea state is responded to in a predictable way by these forms so that in gusts the vessel spills wind but the rudder position need not be changed. The TP52s are hardly a balanced design.

I remember how most used to think that Genoas were actually EFFICIENT!!!! Or that a rudder separate from the keel would be impossible to engineer in a safe reliable way.

I love this. Try to think of retractable Genoas which are just as efficient when rolled to jib size. Then think how nice it is to go to 150 size when there isn't enough wind. Now consider the leading edge of the head sail. Little turbulence there. If you think Genoas can not be efficient then you are missing one of the great designs of today. You did not see TP52s put battens in Genoas for nothing. On that matter the vessels are trend setters. The argument that Genoas were invented owing to race rules forgets the real possibility that the leading sail is the sail most suited to power owing to its being in the cleaner air.

Same kind of argument for rudders. If the rudder is on centerline with the fin keel, then the rudder is in turbulence caused by the keel at some speed. This is avoided completely in designs where the rudder is to the side. Do you know the origin of the term port and starboard. The port side of a boat was the side the rudder was not on. How designers ever got to center rudders is something I have not seen researched.

To be skeptical is one thing but it has to be based on some knowledge and be open to correction unlike Mighetto's raving in aid of maintaining his fixed point of view. MIK Hey, look, I'm hijacking Mighettos thread!!!!!

The world is full of reasonable men. Hence we advance only by the efforts of unreasonable men. My point of view stems from boats designed by legals. Read the start of this thread. Lets proceed with the hijacking. Nice post.

Thank you for so effectively illustrating my point.

[Mark 42]

Stability is not something Frank is associated with.

[mighetto]

Originally Posted by Mark 42

Stability is not something Frank is associated with.

I dare say I know more about it than Jim Teeters. I can hardly believe that Teeters wrote an article in Seahorse. His experience with the Mac26x must have converted him to my way of thinking. Or.. and this is always possible with those who subscribe to east-coast thinking, Teeters may have hired a ghost writer.

Points for discussion:

- unfortunate yet profound trends in design

• fixed fin as opposed to lifting or swing
• boats that heel to much
• wide beam vs slab sides
• wide deck

- revelation; hull acts as a sail enhancer; "beneficial effects of deck edge" AKA freeboard to driving force
- no mention of IRC

Conclusion: well thought out article worthy of a read that explains why TP52 resale values have and will continue to fall in spite of designer guarantees and why TP52 designers are a risk of law suits regarding those guarantees.

[mighetto]

Originally Posted by Mark 42

Reality is so far beyond your grasp.
Duck dodge is a SAILBOAT race.
Showing up in an unlimitted hydroplane does not mean you can win a sailboat race.
Using the motor is called CHEATING and is unsportsmanlike.
If you start the engine you should withdraw and get out of the way of the race traffic.
That means go away.
Do not hang in the race area.
Do not make wakes to screw up the racers and the moored boats.

Did somebody lose a race to a Mac26x?

Years ago I read an article where the author had been asked to describe the sailing life. He started the article by saying that the sailing life and life itself were just the same reality. I then went back and reviewed the film Wind which is often criticized as not portraying reality but by my experience is right on.

There are two key clips in the film and the second follows the first in short order. The first involves the notion that to win a sailboat competition you must be willing to pull the trigger of a gun and shoot those in your way. And the second involves a dance between two racing sailboats (represented as hands) - one trying to cover and the other trying to stay out of its shadow and find its own clear air and path.

This first approach is dirty and represents the reality of mobsters. The second is clean and will be the reality of our sport in short order. Young potentials need to stay out of the shadow of designers like Jim Teeters and others on the east coast of like minded ways. Their's are the ways of mobsters. I speak as a US patriot.

This media, this forum, for a US citizen, is like sailing. If an author were asked to describe the blogging life today his response would have to be that blogging life and life itself are the same reality. It is not true in other countries were calling a vessel a POC - or Teeters a has been - puts family wealth at risk owing to needed defenses in courts of law. Our form of democracy is unique in the world in that way.

Murrelet will not be on the log boom for the unlimited hydroplanes this week end. We were to late on the registration. But you will find her crew and myself some place on the boom or shore Saturday.