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I am a newbie to Dinghy Anarchy, a great forum.  I sail an old Sunfish from the lake behind my house, and am working on a number of areas where there appear to be room for improvement.   My 40+ year engineering career was mostly in fluid dynamics, so my focus is on things like fins and dagger boards, which are pretty much the same as wings and tail fins from airplanes.  This is all for recreational boaters who like to go fast on the water.   Friends with Lasers have asked me to apply what I am doing on my Sunfish to the Laser, so I just started on this.   See what I am doing at https://aerosouth.net/sailboats       I also started the 'Sunfish Speed Blog' (see separate thread on this forum) to encourage people to see if they can make this great little boat a bit faster.    https://aerosouth.net/the-sunfish-speed-blog       All comments are welcome, even the serious ones.....

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Laser innovations would appear to be non-starters because of one-design issues. (See threads on ILCA etc.) Figuring out how to put foils on a Sunfish might keep you busy for a while though.  

 

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2 minutes ago, PaulK said:

Laser innovations would appear to be non-starters because of one-design issues. (See threads on ILCA etc.) Figuring out how to put foils on a Sunfish might keep you busy for a while though.  

 

Note that this is for recreational boaters only.    There are plenty of Sunfish and Laser owners who sail just for fun by themselves or in regattas where One Design rules are not applied.  Our own sailing club has a wide variety of boats in the same race, including Sunfish and Lasers.  The small boats do quite well, and a good time is had by all.  One Design rules are well understood and certainly are there for a good reason.  On the Sunfish, I am working on modern rudder fins and dagger board, not a foil.   This has been tried by others already.    They are pretty neat but would probably be too unstable for the widely varying winds on my lake, surrounded by tall pine trees.

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Even if you are racing on handicap, those handicaps are calculated assuming sunfishes sail as sunfishes and laser sail as lasers. So, if you modify the boat to make it faster, the handicap should really be modified also. 

I'm sure it will be an interesting project seeing what mods you an do and how this affects performance. Most of the modifications will have been known by the designers at the time as well, it's not like either boat was designed to be fastest around. The clever design of both really revolves around ease of sailing, simplicity, and being able to manufacture with consistency to a cost. 

Looking at the shapes of your foils and sails will certainly highlight areas for improvement. Most heavily restricted opens designs or loose one designs play around in this territory. The speed increase are modest, but significant in terms of fleet placing. However, I doubt they will be perceptible sailing around on your own. Not many people can tell the difference between 4.2 knots and 4.4 knots! And if recording speed data, any increases are lost in our hugely variable power supply! 

The easiest way to add speed is to add leverage, but not significantly increase weight (displacement). Trapeze, sliding seat, racks etc. All those will put more load on the boat though, so you'll probably find a material limit, where the structural reinforcement required outweighs the benefits of moving ballast further out. Plus there becomes a self restricting limit when you try t sail boats with huge leverage where moving about reacting to shifts and gust, tacks and gybes becomes a real issue! Even a simple trapeze can be of little benefit on a small tree lined pond.

The next easiest gain is to reduce hull wave drag. So you can make it longer or change the shape of the hull. But easier is to reduce weight, to reduce displacement. Or, create foils that lift the hull, at least partially.  

 

Have fun!

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1 hour ago, Mozzy Sails said:

Even if you are racing on handicap, those handicaps are calculated assuming sunfishes sail as sunfishes and laser sail as lasers. So, if you modify the boat to make it faster, the handicap should really be modified also. 

I'm sure it will be an interesting project seeing what mods you an do and how this affects performance. Most of the modifications will have been known by the designers at the time as well, it's not like either boat was designed to be fastest around. The clever design of both really revolves around ease of sailing, simplicity, and being able to manufacture with consistency to a cost. 

Looking at the shapes of your foils and sails will certainly highlight areas for improvement. Most heavily restricted opens designs or loose one designs play around in this territory. The speed increase are modest, but significant in terms of fleet placing. However, I doubt they will be perceptible sailing around on your own. Not many people can tell the difference between 4.2 knots and 4.4 knots! And if recording speed data, any increases are lost in our hugely variable power supply! 

The easiest way to add speed is to add leverage, but not significantly increase weight (displacement). Trapeze, sliding seat, racks etc. All those will put more load on the boat though, so you'll probably find a material limit, where the structural reinforcement required outweighs the benefits of moving ballast further out. Plus there becomes a self restricting limit when you try t sail boats with huge leverage where moving about reacting to shifts and gust, tacks and gybes becomes a real issue! Even a simple trapeze can be of little benefit on a small tree lined pond.

The next easiest gain is to reduce hull wave drag. So you can make it longer or change the shape of the hull. But easier is to reduce weight, to reduce displacement. Or, create foils that lift the hull, at least partially.  

 

Have fun!

These are terrific ideas, thank you!    Since I'm not really interested in One Design or handicapped racing, my efforts focus on getting my boat around my baseline triangular course faster.   The prediction methods (CFD) I use for designing the dagger board and rudder fins are well validated, so I am sure that I will get the improvements in hydrodynamic efficiency.  I've used these methods to design aircraft parts since 1980.  Both the Sunfish and the Laser have rudders with area 60% of the daggerboard.  When the dagger board is retracted, the rudder is the main source of underwater drag.  From a configuration standpoint, these boats have tandem wings, not a large wing and small control surface as on airplanes.  The rudder is the equivalent of a 'full-flying' stabilator, which is different than a fixed stab plus small moving rudder.  On the Sunfish, I found that the current regulation rudder produces more drag than the fully extended dagger board, despite having 40% less area.  This is due mostly to a poor cross-section and high sweep.   From an efficiency standpoint, I see no reason for sweep on either dagger board or rudder.   But it may have been chosen to move the center of pressure in the longitudinal direction.  Sweep on the rudder fin leads to higher weather helm and premature stall, which I have already verified on my new rudder with very low sweep and thus lower weather helm.  This winter I will split my Sunfish hull and look for ways to reduce its weight.   At this time I will not modify the external shape, but could with my experience with composites.    This is something that few Sunfish owners could/would do.  I am limiting my mods to new parts that can be easily swapped for existing ones.  Many thanks for your expert advice, much appreciated.

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1 hour ago, martin.langhoff said:

Sounds like a lot of fun. In this size, the class where everyone experiments is the Moth - both floaters and foilers.

Floater moths might have cool ideas for you to borrow...

Thank you.   I have looked a bit at the long illustrious history of the Moth and am impressed by the many good improvements.   I am thinking a Moth might be a perfect first sailboat for my young grandchildren.   My impression is that the Moth is more common outside the US though.  Most sailing schools in my state (North Carolina, mid-Atlantic coast) use Sunfish and Lasers for training.

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"Most" of this is pretty obvious.

Increase sail area and go faster in light air and down wind.

Improve foils, point higher/ make less leeway go faster upwind.

Reduce weight better, but harder to do.

All of the above have little structural consequence and will only have incremental improvement in speed.

To go faster you have to increase the righting moment.

Read Frank Bethwaite's  book on Sail Carrying Power relative to displacement to inform this opinion.

Sailboat loads are driven by righting moment, so adding wings or racks ripples through the whole boat.

The Sunfish mast step assembly is a more robust than the Laser mast step in that the tube is glassed to the hull and bonded to the deck instead of the other way around.

Sunfish masts break after a few years of racing as specified, so you are going to have to ( at the very least ) sleeve the mast in the deck bearing area.

You could add shrouds. The hull deck joint can probably take a pretty good load. The hull is made of 2oz mat and 18oz woven roving and is robust .

You could place the chainplates slightly ahead of the mast so the boom can still be eased to 90 degrees.

If you add enough power to get the fish planing consistently, you will be frustrated by the relatively primitive hull form which is kind of a pointed scow with a constant dead rise angle.

It really is too wide up front and too narrow back aft.  Scow moths  evolved in this direction, but not to this extreme. This along with the amount of rocker means that the Sunfish trims very bow up as it goes faster. This is also called squatting and is slow.

One way to resolve this is to add a T foil to the rudder to counteract the suction much like the trim tabs or power tilt on a motorboat.

So I guess adding 1' wings wouldn't be that hard. I would laminate wood to fit the deck and kick up about 15 degrees at the gunwales. They could be bolted through the deck in front and behind the cockpit, and possibly trough the gunwales themselves.

I would get rid of the rudder head and build a cassette style rudder head that can accept a move vertical rudder with a 18" t foil at the bottom. The Sunfish rudder head is barely strong enough, and doesn't have enough range of motion.

I would reduce the chord length of the daggerboard by 25% and increase the draft by 30%. A NACA 5 digit series foil is not a mistake. By reducing the chord, you can get enough camber to be meaningful.

Plan to break masts, booms and gaffs and to reinforce as you learn.

Or give up on the Sunfish and start with an International Canoe hull which is already better than a Sunfish and has a group of like minded people top play with. Used Canoes are really cheap!

SHC

 

 

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1 hour ago, Steve Clark said:

"Most" of this is pretty obvious.

Increase sail area and go faster in light air and down wind.

Improve foils, point higher/ make less leeway go faster upwind.

Reduce weight better, but harder to do.

All of the above have little structural consequence and will only have incremental improvement in speed.

To go faster you have to increase the righting moment.

Read Frank Bethwaite's  book on Sail Carrying Power relative to displacement to inform this opinion.

Sailboat loads are driven by righting moment, so adding wings or racks ripples through the whole boat.

The Sunfish mast step assembly is a more robust than the Laser mast step in that the tube is glassed to the hull and bonded to the deck instead of the other way around.

Sunfish masts break after a few years of racing as specified, so you are going to have to ( at the very least ) sleeve the mast in the deck bearing area.

You could add shrouds. The hull deck joint can probably take a pretty good load. The hull is made of 2oz mat and 18oz woven roving and is robust .

You could place the chainplates slightly ahead of the mast so the boom can still be eased to 90 degrees.

If you add enough power to get the fish planing consistently, you will be frustrated by the relatively primitive hull form which is kind of a pointed scow with a constant dead rise angle.

It really is too wide up front and too narrow back aft.  Scow moths  evolved in this direction, but not to this extreme. This along with the amount of rocker means that the Sunfish trims very bow up as it goes faster. This is also called squatting and is slow.

One way to resolve this is to add a T foil to the rudder to counteract the suction much like the trim tabs or power tilt on a motorboat.

So I guess adding 1' wings wouldn't be that hard. I would laminate wood to fit the deck and kick up about 15 degrees at the gunwales. They could be bolted through the deck in front and behind the cockpit, and possibly trough the gunwales themselves.

I would get rid of the rudder head and build a cassette style rudder head that can accept a move vertical rudder with a 18" t foil at the bottom. The Sunfish rudder head is barely strong enough, and doesn't have enough range of motion.

I would reduce the chord length of the daggerboard by 25% and increase the draft by 30%. A NACA 5 digit series foil is not a mistake. By reducing the chord, you can get enough camber to be meaningful.

Plan to break masts, booms and gaffs and to reinforce as you learn.

Or give up on the Sunfish and start with an International Canoe hull which is already better than a Sunfish and has a group of like minded people top play with. Used Canoes are really cheap!

SHC

 

 

Outstanding ideas - thanks so much.   I have already snapped a rudder fin, a dagger board and my spruce mast has split twice during strong winds, so it seems this is normal when performance is pushed.   I am impressed by your knowledge and the freedom that the IC class allows people.   I will definitely keep this in mind as I exhaust the possibilities in my old Sunfish and as my skills hopefully improve.  Best regards, Kent

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On 1/7/2020 at 6:12 PM, kmisegades said:

Note that this is for recreational boaters only.    There are plenty of Sunfish and Laser owners who sail just for fun by themselves or in regattas where One Design rules are not applied.  Our own sailing club has a wide variety of boats in the same race, including Sunfish and Lasers.  The small boats do quite well, and a good time is had by all.  One Design rules are well understood and certainly are there for a good reason.  On the Sunfish, I am working on modern rudder fins and dagger board, not a foil.   This has been tried by others already.    They are pretty neat but would probably be too unstable for the widely varying winds on my lake, surrounded by tall pine trees.

Regardless it is bad form to tinker with a race boat and take it out of class and then sell it on. 

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9 minutes ago, Tink said:

Regardless it is bad form to tinker with a race boat and take it out of class and then sell it on. 

Understood.   I am sure if I raced I might think the same.   We are all recreational boaters on my lake with a wide variety of rides.   I am an engineer and builder though and love to experiment.   I actually owned a One Design in the past, a DR-107 aerobatic plane.  I completely understand the need for consistency in such competitions.

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Kent, as an aero engineer with a budding interest in dinghy design, you would absolutely devour Frank Bethwaite's books.

A fellow aero man, his experimental work on 14' dinghies in the 70s through 90s has revolutionised skiff and is now heavily influencing modern keelboat design.

Track down a copy of High Performance Sailing (of which there were two quite different versions). Not everything he explains will be relevant, but you're going to walk away much better informed regarding your Sunfish tweaks. 

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37 minutes ago, OneGoat said:

Kent, as an aero engineer with a budding interest in dinghy design, you would absolutely devour Frank Bethwaite's books.

A fellow aero man, his experimental work on 14' dinghies in the 70s through 90s has revolutionised skiff and is now heavily influencing modern keelboat design.

Track down a copy of High Performance Sailing (of which there were two quite different versions). Not everything he explains will be relevant, but you're going to walk away much better informed regarding your Sunfish tweaks. 

Much appreciated.   I have in fact a list of Bethwaite's books here in front of me and was not sure which to get, 'High Performance Sailing' from 2011 or 'Higher Performance Sailing' from 2008?  My main reference to-date has been 'Sailing Theory and Practice' from C.A. Marchaj.   I also plan to get 'The Science behind Sailing' from Joop Sloof, who is a friend of mine from our past aero work and having attended the same graduate school.  Joop is credited as being of the main creators of the winged keel for past America's Cup races.

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7 minutes ago, kmisegades said:

Much appreciated.   I have in fact a list of Bethwaite's books here in front of me and was not sure which to get, 'High Performance Sailing' from 2011 or 'Higher Performance Sailing' from 2008? 

Whatever is easier to find. I understand they share a lot of content but also differ in other content.

I think I have the earlier version. Haven't seen the other. I also have his "Fast Performance Technique" which is more about the sailor than the boat. Haven't finished either - I'm digesting slowly as I go.

I trained in naval architecture (but never worked in the field - I spent 20 years in noise and vibration engineering (via fluid dynamics) before retraining in clinical audiology. So I probably have a more analytical reading of his material than those with less formal technical training. Some of HPS is quite heavy going... but with real lightbulb moments.

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Hi guys.

High Performance Sailing [HSP1] is best described as a text book, and is very heavy going.

Higher Performance Sailing [HSP2] is more of a sailing journal and its 2000 on wards.  Much lighter read.

Sure is some latter editions  of HSP1 there is reference to work though into the late 2000's but these where editors tantalizing you.

The bulk of HSP1 is pre 2000, and is very much dad and has not been corrupted by the 49er/29er and all the spin off projects.

HSP2, besides being lighter, get's into detail of the finer nuances, which may sound flippant, but a few small % change, for-instance, the square-head rig, when we started everyone was in the dark as to how it worked, even Chris Carins whom I credit with it's creation.       But the 49er development in 2007-8-9 changed the basis of how it worked and that is still evolving today.    Dad was instrumental in all that work.    His training was initially as a pilot (in 1936 - 1965) and then as a scientist (1959 - 2012) and that comes through.  

He was very proud of FHT, and it's a great book in it he explains why the techniques others use work.

          My favorite is very definitively Higher Performance Sailing.

                               jB

 

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14 hours ago, OneGoat said:

Whatever is easier to find. I understand they share a lot of content but also differ in other content.

I think I have the earlier version. Haven't seen the other. I also have his "Fast Performance Technique" which is more about the sailor than the boat. Haven't finished either - I'm digesting slowly as I go.

I trained in naval architecture (but never worked in the field - I spent 20 years in noise and vibration engineering (via fluid dynamics) before retraining in clinical audiology. So I probably have a more analytical reading of his material than those with less formal technical training. Some of HPS is quite heavy going... but with real lightbulb moments.

Good advice, thank you.  I like rigorous books full of math.  Started my fluids career writing algorithms to solve flow equations as there were no commercial CFD codes back then.  Fun stuff, especially when things converged....

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13 hours ago, JulianB said:

Hi guys.

High Performance Sailing [HSP1] is best described as a text book, and is very heavy going.

Higher Performance Sailing [HSP2] is more of a sailing journal and its 2000 on wards.  Much lighter read.

Sure is some latter editions  of HSP1 there is reference to work though into the late 2000's but these where editors tantalizing you.

The bulk of HSP1 is pre 2000, and is very much dad and has not been corrupted by the 49er/29er and all the spin off projects.

HSP2, besides being lighter, get's into detail of the finer nuances, which may sound flippant, but a few small % change, for-instance, the square-head rig, when we started everyone was in the dark as to how it worked, even Chris Carins whom I credit with it's creation.       But the 49er development in 2007-8-9 changed the basis of how it worked and that is still evolving today.    Dad was instrumental in all that work.    His training was initially as a pilot (in 1936 - 1965) and then as a scientist (1959 - 2012) and that comes through.  

He was very proud of FHT, and it's a great book in it he explains why the techniques others use work.

          My favorite is very definitively Higher Performance Sailing.

                               jB

 

Outstanding and humbling to receive your good comments, sir.   I'll probably get both books - one can never read enough from such good references.  Your family has made such important contributions to the science of sailing, congratulations!   I often wondered if the highly tapered tips of conventional sails did not cause the same aerodynamic problems one has on similar aircraft wings, namely early stall at tips with loss of control.  I wonder if your father had learned about cropped tips from modifications of the original Supermarine Spitfire, with its lovely elliptic wings?   These were cropped starting with the Mark V.  Some argue for better maneuverability.  Others claim these were easier to produce.  Another claim was that the 'Spit' had three different interchangeable wingtips that were chosen depending on the mission. The 49er is a beautiful boat.   I will certainly keep it in mind should my sailing skills improve beyond the Laser.  Right now I am still working on taming my Sunfish on gusty days.  Can a 62 year-old newbie to sailing handle a 49er?

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Well I'm also 62, I probably could steer a 49er but there is no way in hell I could crew one.     Sir JJ keep threatening me to a one up race in 49ers in China, I probably can't say no!

I grew up with fastidiously beautiful balsa model aeroplane wings that where all elliptical tips and all the way through to 2008 dad believe that an elliptical (pin head) rig was the right way to go.     We did our own bit of coding (then excel program) and got heavily into cord-length vs mast-bend ratios, developing methods to label them and then mix and match.    The early 49er rig was part of this, and tuning an 18teen footer rig with scissors on the beach, taking off 20-25mm of roach, it was pretty amazing.

But then, I was with him, in my speed boat, following my 18 year old son Harry, and Simon Watin (FRA) early 2008, sail a new fan-dangled square head on a 49er and it was a light bulb moment.   You saw dad's eye's light up, because he could not believe he was seeing what he was seeing.     Just remember he was 88 at this stage, and mum told me he did not sleep for 3 days, doing long hand maths in radians!  Watin was doing the same thing on mat-lab and the project just exploded fwd from that point.

My strongest memory of my father is once he had proved something right (or wrong) he simply pivoted and was fully committed to the new path.      I hope I am 1/4 of the mental capacity he was at when I'm 70, let alone at 88.     Very hard act to follow, dare I say impossible!

Spit's, he flew them a few times when he was seconded to the RAF, early in 1940s.     His love (bad word) was the Pacific theater and the Ventura when he at the age or 24 and a Squadron Leader was seconded to Gen McCarther along with Cat's.   End up with one or 2 DFC's for his trouble.     His best mate ended up being a Captain of a Japaness warship and they took great efforts trying to kill each other over the Solomon's,   Kenji Yashakawa     (one of this DFC's was for that)       

Talking of cropped wings, the other shot is him launching his World Record winning RC flying boats ( once your flown a Cat, there is no coming back) in 1955 (pre-me) in Torbay NZ, he kept it in the air for over 12 hrs, motor was good for less than a hr, it really only got it up to a critical height and then it was slope soaring.   Very cropped wings.

My flying was limited to sitting on his knee from 7-14 flying all sort of planes but I did end up with a VFR and then flew gliders extensively.    As a result, I went from a also-ran sailor to a RS [Rock Star] in about 2 months and I put that all down to being able to visualise the wind from a 3d perspective.    Highly recommend it.   Dad is fairly prolific on wind and 3d patterns.

Enjoy the books,   jB

image.jpeg

Dad, Torbay 1955.jpg

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Howdy Julian, Thank you for the fascinating details on the evolution of the square head rig.  I just read your piece "SQUARE HEAD VS PIN HEAD RIGS" from November 2017, which answers some of my questions.  I have been searching for a similarly-rigorous description of dagger/center board and rudder fin design but have not come across much yet. Any ideas?   Airplanes, model airplanes and sailing share so many common elements that it is no wonder your father built models, as mine did and I still do.   

Yesterday while sailing my Sunfish in gusting wind the spruce mast snapped at its base, which was pretty dramatic.  Getting to shore dragging the rig was interesting.   I knew that it would eventually happen as I push the old boat pretty hard upwind.  Reading in your article about the science of gusts explained things better.   

I just watched the 49er World Cup Series final from Santander, Spain, June 2017 (Youtube).   I can fully understand why this sort of racing is something for the younger fellows.   For the life of me though I can not figure out how the trapeze system works during tacks.  The guys bolt to the opposite side of the boat without fouling any cables.  It must be magic from Oz?     

I regret I have only been to Australia once, in 2003 for business, so I did not see much.  I left my wife and youngest son in Manly while I was on business.  Son Tim was surfing then and enrolled in classes on Manly Beach.  The best part was when the lovely young Australian ladies appeared after school for a swim.  I am not sure he learned much more about surfing as a result, but he sure did enjoy the sights.  We spent some time with the great folks from Chapter One of the Sport Aviation Association of Australia (SAAA), very hospitable and friendly people, as well as terrific craftsmen in aircraft construction. 

My father did a fair amount of work with Fisher-Paykel in NZ towards the end of his career with GE Appliances. This included a ride on a 12-meter boat during one visit.  A former Korean-war Navy man, he said he could live in NZ, he enjoyed visits so much.  My wife keeps asking me when I will take her to OZ and NZ again. Might be fun for our 40th anniversary in two years.  Now I am way off-topic, sorry folks. 

Back to topic - below is a picture of our first rough-cut 'Sabre' rudder fin for the Sunfish.   Solid poplar is being used only for setting up the 5-axis Homag mill and fixtures.  The actual parts will be made from a laminate of Sapele, an incredibly hard and strong variety of mahogany.  The fin ( and our similarly-shaped dagger board )  features custom-designed sections and the planform was chosen from 100+ variants.  It will fit the existing rudder cheek hardware and will flip up when beaching as for the current fiberglass fins.  I hope to have it in the water in a week or so.  I considered using glass or graphite, but having a nearby shop with the advanced HOMAG CNC capabilities and the inexpensive Sapele makes wood an attractive alternative to the mess/cost/labor of composites.   Our state of North Carolina is a major producer of furniture, so the equipment and expertise is pretty good here.

 

Sabre_Poplar_First_Roughcut.jpg

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Off-topic, but you start to understand where we are coming from, I just found these, 

#1 is Sqd Leader Bethwaite leading his team home after a sortie.  Note the NZ reg number and the NZ roundels stuck over the US star.  About 1944 in his Ventura.   The photo was taken over the Solomons.     I'm told he did not loose a single plane or crew member in his Sqd, and they could out run Mosquitoes if they hit them hard (std stuff, coming out of the sun) and the hit the deck (less than 500ft)!     The Mosquitoe suffer over heated engine, to light, too much drag, plus there was a lot of lead moving vary fast in their direction from the 4 rear facing guns.

Lots and lots of ellipses!

10 years latter this is him, left hand seat landing a Solent in Auckland, and this is still pre us, 1955, still lots of ellipses.   TEAL is the pre-cursor to Air New Zealand!

~~~~~~~~~~~~~~~~~~

Comments on foils.

The single biggest thing is that Air is fundamentally different from Water.   The fact water is 812 x more dense is important but not the key difference.

The key difference is that water is non-compressible!!!!!!!

So any reliance on sectional CoL's or CoD's from a wind tunnel are very limited.    

The next big thing from my POV is that the Centerboard and the Rudder do vastly different jobs.

The centerboard operates 99% of it's life at 1.5 - 2° AoA.    The only time it operates at above that AoA is coming out of a tack or a violent maneuver and you can only sustain a AoA of 4-5° and upwards, for 1/2 a second, maybe, any longer and you capsize, or flip out or whatever.    It's sole function is to limit yawl to about 2°.   Stop the boat going sideways.

So a centerboard needs to be a given % camber which will be dependent on mean hull speed.   A sunfish/Laser is likely to be around 12-13%, but otherwise needs to be minimum drag section, which tends to be semi circular with a elliptical front 40-45%, LE radius will determine how much stick you get out of a tack (more the better) and then how much drag you have once you get going (less the better), and at a guess a Laser/Sunfish wants to be 2-2.5% LE Rad.

Rudder dose a completely different job.  1st thing, if you have the boat balance well both in terms of CoE/CLR position and in terms of the area of the rudder  (rudder wants to be 27-29% of the total surface area (Centerboard and rudder combined)) then it will have about 1/2 the loading of the centerboard.   2nd thing is it operates maybe 80% of its time at 1.5-2° AoA but occasionally you want it to operate at a much higher AoA when your tacking, gybing or avoiding another boat, or a rock, or going around a bouy, and its pretty embarrassing if it lets go doing those maneuvers.    So they tend to be a bit fatter than the C-board, (1-2%) the max camber is a bit further fwd,   around the good old 1/3 aft but we have found that the elliptical front 30% bending into a semicircular run aft still gives the best results.

So by definition, the C-board section has to be different from the rudder section.

If you start getting into hollows (TE's) it's because you have messed up somewhere, either not enough depth or not enough area or you're put the rudder where it will ventilate.

Truncated ellipse makes huge sense for the c-board.    When we had 4 foils for the 18teen, #1 was the big ellipse, 11% camber, #2 we cut 300mm off the tip and droped the camber to 9.5-10%, #3 we took almost 900mm (off a 2.1m LOA #1 board) and dropped the camber under 8.5% & the #4 we made just longer than the rudder (39" so about 1m out the bottom of the boat) and 6% camber.    Just remember these c-boards where hanging onto 280-300kgs on 33ft wings of RM, #4 mast was 27ft    (#1 mast was 35ft)

Rudders, there is a reason why aircraft use slab rudders, minimum drag, maximum effect!    With the 18teen we had very slab rudders.   The 49er and more so the 29er have prettied up slab rudders.     49er rudder is a bit close to the wind (would not want to be any smaller), 29er rudder is bloody good!

The parallels in foil design (as above) mirror 787, 777 & A350 almost word perfectly.     Strange that!     Back to the 2 photo's.

Then you can get into feathering foils and sectional tapers, but that's another 2-3 pages.

              jB

Ventura_1944_Solomons.jpg

Solent_Dad_and_his_flying_boat_(2).jpg

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On 1/7/2020 at 12:51 PM, kmisegades said:

I am a newbie to Dinghy Anarchy, a great forum.  I sail an old Sunfish from the lake behind my house, and am working on a number of areas where there appear to be room for improvement.   My 40+ year engineering career was mostly in fluid dynamics, so my focus is on things like fins and dagger boards, which are pretty much the same as wings and tail fins from airplanes.  This is all for recreational boaters who like to go fast on the water.   Friends with Lasers have asked me to apply what I am doing on my Sunfish to the Laser, so I just started on this.   See what I am doing at https://aerosouth.net/sailboats       I also started the 'Sunfish Speed Blog' (see separate thread on this forum) to encourage people to see if they can make this great little boat a bit faster.    https://aerosouth.net/the-sunfish-speed-blog       All comments are welcome, even the serious ones.....

I didn't see anything Laser-related but just ran across a Laser innovation on craigslist that brought back some fond memories.

This might fall under the "buy an ad" category since I know the builder, but...

Sailboat wing sails for Laser - $150

00J0J_aFh4ZERJA9v_1200x900.jpg

That's me in XL1. For more see the tale of the Wingsail Laser World Championships

We had lots of fun with those wing sails. They're surprisingly powerful if you can figure out how to keep them powered up. Powerful enough to break the mast step right off the bottom of the boat...

tilted-wing.jpg

It didn't finish falling in the water until I got back to the ramp.

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  • 5 months later...

rs=w:388,h:194,cg:true

Dear friends:

We are pleased to announce that our new "FS" series of recreational rudder blades are now in pre-production.

While these are for the Sunfish, we know that many Laser owners also sail the boat.   Longer term, we plan to apply the knowledge gained from the design of advanced rudder blades and daggerboards to the Laser.

The result of our close collaboration with Dutch hydrodynamics expert Joop Sloof, creator of the winged keel for the 1983 America's Cup winning Australia II and a friend of mine, the "FS" includes a number of unique features to lower drag, reduce weather helm and weight.

The blade has performed well in our own tests and is now being evaluated by an accomplished Sunfish sailor on the Atlantic coast.

You will find details on the "FS" here:

https://aerosouth.net/sailboats

We are also nearing production of standard rudder blades as well as our newly-designed "Sabre" daggerboard.

Other helpful components for Sunfish and Laser are available for purchase now, ie our sheet guide clips, mast hole cover and tiller extension.

All AeroSouth products for Sunfish and Laser sailboats are designed to improve recreational sailing.

They are proudly engineered and made in North Carolina, USA!

happy sailing,

Kent Misegades
President
AeroSouth
Seven Lakes, NC
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On 1/7/2020 at 12:51 PM, kmisegades said:

I am a newbie to Dinghy Anarchy, a great forum.  I sail an old Sunfish from the lake behind my house, and am working on a number of areas where there appear to be room for improvement.   My 40+ year engineering career was mostly in fluid dynamics, so my focus is on things like fins and dagger boards, which are pretty much the same as wings and tail fins from airplanes.  This is all for recreational boaters who like to go fast on the water.   Friends with Lasers have asked me to apply what I am doing on my Sunfish to the Laser, so I just started on this.   See what I am doing at https://aerosouth.net/sailboats       I also started the 'Sunfish Speed Blog' (see separate thread on this forum) to encourage people to see if they can make this great little boat a bit faster.    https://aerosouth.net/the-sunfish-speed-blog       All comments are welcome, even the serious ones.....

If you want I have a laser hull you can hack up and mod ($150)

 

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18 hours ago, JBOATTROUBLEMAKER said:

If you want I have a laser hull you can hack up and mod ($150)

 

Thank you very much!  What I need however is a usable Laser for test purposes.    A neighbor of mine has offered his.    We'll start looking at Laser fins and boards this fall once the parts for the Sunfish are in full production.   From our first glance though there is plenty of room for improvement - for recreational use, of course.

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  • 3 months later...

Dear friends, with our new "FS" rudder blade in production and the new daggerboard in testing, I thought others would be interested in the details of our efforts. I attach here a report on this, which can also be found as the last PDF on the list here: https://aerosouth.net/media

AEROSOUTH_SUNFISH_RUDDER.pdf

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3 hours ago, kmisegades said:

Dear friends, with our new "FS" rudder blade in production and the new daggerboard in testing, I thought others would be interested in the details of our efforts. I attach here a report on this, which can also be found as the last PDF on the list here: https://aerosouth.net/media

AEROSOUTH_SUNFISH_RUDDER.pdf

Interesting.

- Does it sail well?

- Sunfish and other small dinghies are often sailed with the daggerboard partially raised in heavy conditions, does the new daggerboard design handle this? the original clearly did. 

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Hello Martin.

First question - well, we sure like it, as the weather helm, quite pronounced for the legacy blade, is nearly gone.   Since its drag is half that of the older rudder blade, it is guaranteed to improve speed, but of course these things are hard to quantify initially.  Anecdotally we're hearing this from the first users.   See some of their comments on the bottom of my report.

Second question - yes, our new daggerboard has the same dimensions as the legacy board in the trunk area.  It can be retracted just as with the legacy board, and has similar holes in the top for an easy switch of hardware and rigging.  Same for the rudder, which was designed to be compatible with existing attachment hardware and tillers.  We'll add some pictures of both in action to our web site when we get a chance.

Foiling is making amazing advancements.  As an aerodynamicist by profession, I'd love to design the wings for these, although what I am seeing on the new production foiling boats like the UFO sure look good.  My lake, with very unsteady winds, makes foiling a real challenge, but who knows? A neighbor just bought a foiling UFO.   My gut feeling is that the Sunfish is perhaps not the best starting point for a foiling boat.  I know some have attempted this and I really commend them for the effort.

Happy Sailing!

Kent

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  • 1 month later...

Based on initial user comments, we've tweaked a few things on both our FS rudder blade and the Sabre daggerboard.  Otherwise they are performing well.  details at aerosouth.net Thanks to all here for the inspiration, comments and support.  In the AeroSouth Skunk Works now is a mod/kit to allow the Sunfish to foil above water.  They say it's not possible.  We want to at least give it a try.  Anyone interested?  We'll post some sneak-peak pictures here as things progress.

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3 hours ago, kmisegades said:

Based on initial user comments, we've tweaked a few things on both our FS rudder blade and the Sabre daggerboard.  Otherwise they are performing well.  details at aerosouth.net Thanks to all here for the inspiration, comments and support.  In the AeroSouth Skunk Works now is a mod/kit to allow the Sunfish to foil above water.  They say it's not possible.  We want to at least give it a try.  Anyone interested?  We'll post some sneak-peak pictures here as things progress.

I'm not trying to be that guy but have you bought an ad with Sailing Anarchy since you're on here selling stuff?  At least you should go into the classifieds and buy an add in the gear section offering up your Sunfish blades, even if you don't take out an ad on the homepage.  Seems like the right thing to do since this is somebody's company that employs people.

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5 hours ago, spankoka said:

As I understand it, my ancient Laser could have wooden blades and still be class legal. I am interested. 

Yes, it's true. If the wood blades are the original Laser class blades, they are still legal to race with.  We have a couple of those in our fleet, just spares at this point but they do get used from time to time.  

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  • 2 months later...

what ever happened to the SUPER sunfish class ?

my limited understanding was the hull was to be let alone

but all the other bits were free to change as long as they fit the stock hull

or was that called something else as the super was an AMF/ALCORT class

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5 hours ago, nota said:

what ever happened to the SUPER sunfish class ?

my limited understanding was the hull was to be let alone

but all the other bits were free to change as long as they fit the stock hull

or was that called something else as the super was an AMF/ALCORT class

Super Sunfish was produced by AMF-Alcort as a one-design. It used the hull of the Sunfish but a cat rig instead of the lateen rig. It was a cool idea but didn't see to get much traction probably due to the Laser and the AMF-Alcort Force 5 (and others). A cousin had a Sunfish that came with a Super Sunfish rig. I sailed the Super Sunfish once and it sailed nicely (but not nice enough to convince me to switch from a Laser!). Very very stable downwind compared to a Laser. I don't know if it was faster than a Sunfish.

I believe the picture below was used in the AMF-Alcort Super Sunfish brochure.

Here's an interesting blog found with Google

https://my2fish.wordpress.com/2011/10/25/restoring-sailing-a-super-sunfish/

An interesting 21st century "take" on the Super Sunfish concept is the Fulcrum Rocket with a UFO rig. See the Rocket thread.

Screen Shot 2021-03-14 at 5.48.55 PM.png

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3 hours ago, Alan Crawford said:

Super Sunfish was produced by AMF-Alcort as a one-design. It used the hull of the Sunfish but a cat rig instead of the lateen rig. It was a cool idea but didn't see to get much traction probably due to the Laser and the AMF-Alcort Force 5 (and others). A cousin had a Sunfish that came with a Super Sunfish rig. I sailed the Super Sunfish once and it sailed nicely (but not nice enough to convince me to switch from a Laser!). Very very stable downwind compared to a Laser. I don't know if it was faster than a Sunfish.

I believe the picture below was used in the AMF-Alcort Super Sunfish brochure.

Here's an interesting blog found with Google

https://my2fish.wordpress.com/2011/10/25/restoring-sailing-a-super-sunfish/

An interesting 21st century "take" on the Super Sunfish concept is the Fulcrum Rocket with a UFO rig. See the Rocket thread.

Screen Shot 2021-03-14 at 5.48.55 PM.png

I remember the ad in Sailing World comparing it to “Brand L” with claims that upwind speed was comparable, but off the wind it wasn’t even close.

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