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      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  

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4 hours ago, Doug Lord said:

WOLF concept model + foils + seats:

WOLF +foils+ seats    11-9-17 003.JPG

WOLF +foils+ seats    11-9-17 001.JPG

Couple of LEGO people, a little tiny card table and a tiny chess board and your set.

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WOLF and MPX 12(first version of Fire Arrow)-----

WOLF and little Fire Arrow   11-26-17 004.JPG

WOLF and little Fire Arrow   11-26-17 006.JPG

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1 hour ago, Doug Lord said:

WOLF and MPX 12(first version of Fire Arrow)-----

WOLF and little Fire Arrow   11-26-17 004.JPG

WOLF and little Fire Arrow   11-26-17 006.JPG

I’m sorry, the same photos again, why?

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Same as what?! Never been posted before-the WOLF is different than any other picture of it-amazing you can't tell.........Eye problems?

rotating wing mast, "chainplates",forward seat fairings , aft seat seals/drains,  mast step, seat back cosmetization, cockpit drains

WOLF mast ,foils, seats 11-25-17 002.JPG

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32 minutes ago, Doug Lord said:

Same as what?! Never been posted before-the WOLF is different than any other picture of it-amazing you can't tell.........Eye problems?

rotating wing mast, "chainplates",forward seat fairings , aft seat seals/drains,  mast step, seat back cosmetization, cockpit drains

WOLF mast ,foils, seats 11-25-17 002.JPG

Yep, same old shitter.

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2 hours ago, Doug Lord said:

Same as what?! Never been posted before-the WOLF is different than any other picture of it-amazing you can't tell.........Eye problems?

rotating wing mast, "chainplates",forward seat fairings , aft seat seals/drains,  mast step, seat back cosmetization, cockpit drains

WOLF mast ,foils, seats 11-25-17 002.JPG

It’s a fucking model Doug, get it working and then worry about the cosmetization

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The model is a unique concept model(not a sailing model) of a 15.5' sport trimaran . It's only important what it looks like-the technology has already been proven several times over.

MPX Fire Arrow-First Full Flying Foiling on video-7-24-14 009 (2).JPG

MPX Fire Arrow.jpg

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10 minutes ago, Doug Lord said:

The model is a unique concept model(not a sailing model) of a 15.5' sport trimaran . It's only important what it looks like-the technology has already been proven several times over.

MPX Fire Arrow-First Full Flying Foiling on video-7-24-14 009 (2).JPG

MPX Fire Arrow.jpg

By who?

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2 hours ago, Doug Lord said:

The model is a unique concept model(not a sailing model) of a 15.5' sport trimaran . It's only important what it looks like-the technology has already been proven several times over.

MPX Fire Arrow-First Full Flying Foiling on video-7-24-14 009 (2).JPG

MPX Fire Arrow.jpg

You know, most folks skip the model part and design on the computer these days.

Tell you what, how about a nice pat on the back for building a shiny toy? 

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WOLF concept model--- sail patterns for study(217 sq.ft.-upwind)  :

WOLF concept-- 2 001.JPG

WOLF concept-- 2 002.JPG

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On 9/29/2016 at 12:19 PM, Doug Lord said:

Many in this thread earlier had doubts that the Fire Arrow configuration would "work" despite the fact that in its last test on July 24th ,2014 the foil system worked 100% perfectly. Well, now there is proof beyond a shadow of a doubt that the central feature of the Fire Arrow system-a lifting foil on the daggerboard in combination with an ama UptiP foil works and works well.In fact what they say about it could have come from the design and build log here: http://www.boatdesign.net/forums/multihulls/high-performance-mpx-foil-self-righting-trimaran-test-model-36058-159.html

I think it is a huge accomplishment for Maserati and proves what I have said for over 6 years that this basic configuration is uniquely suited to a foiling trimaran and has tremendous advantages. This is only the beginning -as more people recognize how good the system is, more and more tris will use the configuration-great for foiling, great for trimarans!!

----

Now, I've got to get a 14-16' version of the boat built-using either uptip foils or Welbourn foils(or both for testing).

 

 

 

Watch the video above very carefully and you can see the foil on the daggerboard-this is so cool I can hardly stand it!

More: http://maserati.soldini.it/

 

What Maserati says:

First* trimaran in the world to fly with effortless stability on the horizontal loading-bearing surface of her centerboard, Maserati Multi70 brilliantly puts into practice Guillaume Vernier and his Team’s idea of flying on three resting points using a load-bearing centerboard, L-foil and a rudder instead of the two rudders and single foil adopted on America’s Cup cats.
Giovanni Soldini and his Team are engaged in a new challenge as they endeavour to turn Maserati Multi70 into the first ocean-going flying trimaran. An ambitious project that spans not just Guillaume Vernier’s excellent work (he worked on the modifications to her appendages) but also over 4.000 nautical miles of sailing clocked up by the Team this summer.
The straight central daggerboard plays a revolutionary role in this new flying trim as the horizontal load bearing surface at its end generates lift, raising the boat out of the water. “When Maserati Multi70 rises up on her lateral foil and rudder, the daggerboard wing acts as a third resting point – the central and largest one”.
Tests in wind of 40 knots have demonstrated that Maserati Multi70 is now much more stabilized and able to fly in conditions unthinkable before. Safely tackling also big seas.



* Wrong-the Fire Arrow was the first trimaran in the world to fly on a daggerboard foil in combo with uptip foils on each ama.

 

Fire Arrow pictures by Dan Burke and Doug Lord:

sg216b.jpg

 

 

do2ftk.jpg

Proof 2016!  And now, 2018, there is Gitana XVII, and Banque Populaire-all using the basic elements of Fire Arrow Foil System-with more to come.

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Douggie - Please just go away and play with your FaRt ArOuNd toy.  You are an embarrassment even to old white men from Florida

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Fire Arrow--- main foil dual  wand assembly-allows takeoff in 5mph wind:

Dual Wand Control--Rudder 002.jpg

MPX--new, shorter, adjustable wands 010.JPG

Wand system-final 001.JPG

MPX_Foiling--_Foil_Assist-Flying_Main_hull_Over_Powered_009 - Copy.JPG

MPX Fire Arrow-First Full Flying Foiling on video-7-24-14 013.JPG

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Fire Arrow Ama foil with wash-in(not wash-out)  utilizing iFLAP  :

This helps the foil work well throughout the speed range especially with low speed takeoff and allows the foil to work, in some respects, like a wand controlled foil but with no moving parts......

See pictures "A" and "B" below that represent two very different load and speed conditions-a perfect illustration of the automatic altitude control of this foil. Furthermore, in light and medium conditions the foils have never needed adjustment after being initially set up.

MPX i-flap-frnt view port foil low speed takeoff waterline.jpg

MPX i-flap-frnt view port foil --Twist (1).jpg

MPX i-flap-frnt view port foil waterline high speed.jpg

MPX Fire Arrow-First Full Flying Foiling --ama altitude--A.jpg

MPX Fire Arrow-First Full Flying Foiling---ama altitude B.jpg

 

 

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24 minutes ago, Doug Lord said:

Fire Arrow Ama foil with wash-in(not wash-out)  utilizing iFLAP  :

This helps the foil work well throughout the speed range especially with low speed takeoff and allows the foil to work, in some respects, like a wand controlled foil but with no moving parts......

See pictures "A" and "B" below that represent two very different load and speed conditions-a perfect illustration of the automatic altitude control of this foil. 

MPX i-flap-frnt view port foil low speed takeoff waterline.jpg

MPX i-flap-frnt view port foil --Twist (1).jpg

MPX i-flap-frnt view port foil waterline high speed.jpg

MPX Fire Arrow-First Full Flying Foiling --ama altitude--A.jpg

MPX Fire Arrow-First Full Flying Foiling---ama altitude B.jpg

 

 

same photo for the last 2+ years. Sad. Bigly.

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Fire Arrow Main and Rudder foils:   since the last , most successful test of the boat in July 2014 a lot of study went into the foils including the main and rudder foils. Both the daggerboard and rudder were shortened 6" (1.7' to scale) to reduce wetted surface. The daggerboard was tricky since the foil had to be opened up and the flap pushrod disconnected, then the  daggerboard was cut and lengthened. Finally the pushrod was lengthened, the board closed up, sealed and  cosmetisized. Then the mainfoil flap was lengthened and small experimental endplates were added to the flap.

Note the short and long partial span mainfoil flaps.

MPX Fire Arrow -experimental flap endplates-8-26-14 002.JPG

MPX Foil Junction 002.JPG

MPX Foil Junction 006.JPG

Fire Arrow mainfoil.JPG

MPX finished foil mods painted 006-short flap.JPG

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It's always good for a laugh to see how Doug does the exact opposite of what is considered state of the art. Take the rudder. If you look at almost every development on rudder foils, they have pushed them further and further aft compared with the vertical. This is for 2 reasons. The lesser one is that it increases "wheelbase" which provides more stable flight but by far the biggest is that it greatly reduces control problems due to flow separation/ventilation. I have to conclude that to experience these problems you need to get foiling properly and achieve some speed, which Doug has never done with this model, so he has never experienced the issues.

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The Super Foiler doesn't have foils on the main hull they have twin rudders with foils in the floats. Their foils look nothing like the crap from doug, perhaps they know something that doug doesn't.

 

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1 hour ago, Team_GBR said:

It's always good for a laugh to see how Doug does the exact opposite of what is considered state of the art. Take the rudder. If you look at almost every development on rudder foils, they have pushed them further and further aft compared with the vertical. This is for 2 reasons. The lesser one is that it increases "wheelbase" which provides more stable flight but by far the biggest is that it greatly reduces control problems due to flow separation/ventilation. I have to conclude that to experience these problems you need to get foiling properly and achieve some speed, which Doug has never done with this model, so he has never experienced the issues.

Actually, my foils are based on the work Mark Drela did with Decavitator, foil below. At it's fastest Fire Arrow would be operating at Reynolds numbers very close to Decavitator. The shape of foils is greatly affected by the speed they are intended to work at so foils on a scale model of Super Foiler or of an AC 50 would look a lot different on the model.  Since Fire Arrow is a scale model of a 19.5 ft. foiler , the model foils and the fullsize foils would be somewhat different particularly in thickness/chord ratio. Planform would be very similar.

As to "footprint" your comment was more nonsense: whether the rudder and board are aft or forward on the foil, as long as both are the same the footprint wouldn't change!-

Decavitator foil from Dr. Mark Drela on boatdesign.net 10/27/13 :

It is currently in storage at MIT. On 27 October 1991, Mark Drela set the human powered world-record speed with Decavitator of 18.5 knots (21.3 mph; 34.3 km/h) over a 100-meter race course on the Charles River in Boston, Massachusetts.

Fire Arrow has done 2 times wind speed in initial testing- about 10mph in  a 5mph wind the very first time she foiled.

My 56" LOA by 72" F3 did 18mph max reefed in a 22mph wind about 18 years ago and over 2.4 times windspeed in a 5 mph breeze. She had extremely thin foils...... 

 

Decavitator foil-mark drela 10-27-13 bd-net foiler design.jpg

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53 minutes ago, Doug Lord said:

Actually, my foils are based on the work Mark Drela did with Decavitator, foil below. At it's fastest Fire Arrow would be operating at Reynolds numbers very close to Decavitator. The shape of foils is greatly affected by the speed they are intended to work at so foils on a scale model of Super Foiler or of an AC 50 would look a lot different on the model.  Since Fire Arrow is a scale model of a 19.5 ft. foiler , the model foils and the fullsize foils would be somewhat different particularly in thickness/chord ratio. Planform would be very similar.

As to "footprint" your comment was more nonsense: whether the rudder and board are aft or forward on the foil, as long as both are the same the footprint wouldn't change!-

Decavitator foil from Dr. Mark Drela on boatdesign.net 10/27/13 :

It is currently in storage at MIT. On 27 October 1991, Mark Drela set the human powered world-record speed with Decavitator of 18.5 knots (21.3 mph; 34.3 km/h) over a 100-meter race course on the Charles River in Boston, Massachusetts.

 

So you are quoting a 1991 design as your reference, on a boat that is far lighter and where the foils in question are mounted on the front of the boat. Even more telling, in later developments of the concept, the wings were moved back in relation to the verticals.

Quote

 

Fire Arrow has done 2 times wind speed in initial testing- about 10mph in  a 5mph wind the very first time she foiled.

 

How was that measured? An estimate from your video. You are so full of shit.

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1 hour ago, Doug Lord said:

Actually, my foils are based on the work Mark Drela did with Decavitator, foil below. At it's fastest Fire Arrow would be operating at Reynolds numbers very close to Decavitator. The shape of foils is greatly affected by the speed they are intended to work at so foils on a scale model of Super Foiler or of an AC 50 would look a lot different on the model.  Since Fire Arrow is a scale model of a 19.5 ft. foiler , the model foils and the fullsize foils would be somewhat different particularly in thickness/chord ratio. Planform would be very similar.

As to "footprint" your comment was more nonsense: whether the rudder and board are aft or forward on the foil, as long as both are the same the footprint wouldn't change!-

Decavitator foil from Dr. Mark Drela on boatdesign.net 10/27/13 :

It is currently in storage at MIT. On 27 October 1991, Mark Drela set the human powered world-record speed with Decavitator of 18.5 knots (21.3 mph; 34.3 km/h) over a 100-meter race course on the Charles River in Boston, Massachusetts.

Fire Arrow has done 2 times wind speed in initial testing- about 10mph in  a 5mph wind the very first time she foiled.

My 56" LOA by 72" F3 did 18mph max reefed in a 22mph wind about 18 years ago and over 2.4 times windspeed in a 5 mph breeze. She had extremely thin foils...... 

 

Decavitator foil-mark drela 10-27-13 bd-net foiler design.jpg

How are you calculating the Reynolds numbers Doug?

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Well, you weren't gone long!!

For water:  speed in mph X Chord in ft.X 121,000

or for quick reference, table p35 vellinga's book

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49 minutes ago, Team_GBR said:

So you are quoting a 1991 design as your reference, on a boat that is far lighter and where the foils in question are mounted on the front of the boat. Even more telling, in later developments of the concept, the wings were moved back in relation to the verticals.

How was that measured? An estimate from your video. You are so full of shit.

Latest development of decavitator foils(record setting) :

Decavitator rudder foil showing offset.pdf

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12 minutes ago, Doug Lord said:

Well, you weren't gone long!!

For water:  speed in mph X Chord in ft.X 121,000

or for quick reference, table p35 vellinga's book

I’m restraining myself from you polluting other threads, this however is fair game.

How are you using Froude numbers in all your calculations?

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12 minutes ago, mad said:

I'm restraining myself from you polluting other threads, this however is fair game.

How are you using Froude numbers in all your calculations? 

And I was thinking good riddance! Don't let the door hit you in the ass......

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1 minute ago, Doug Lord said:

And I was thinking good riddance! Don't let the door hit you in the ass......

Feel like answering the question?

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why I waste my time with a complete ass like you beats the hell out of me...

I don't -generally- use Froude #'s in design work. I use the old "speed-length ratio"(1.34 X square root of the wl length) or as modified in Vellingas book- 1.5 instead of 1.34 for monohulls. Of course, if for any reason I needed a Froude number I would just multiply the SLR X .30........

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21 hours ago, Doug Lord said:

why I waste my time with a complete ass like you beats the hell out of me...

I don't -generally- use Froude #'s in design work. I use the old "speed-length ratio"(1.34 X square root of the wl length) or as modified in Vellingas book- 1.5 instead of 1.34 for monohulls. Of course, if for any reason I needed a Froude number I would just multiply the SLR X .30........

Hang on a minute. We are talking foiling boats. SLR is irrelevant!

22 hours ago, Doug Lord said:

Latest development of decavitator foils(record setting) :

Decavitator rudder foil showing offset.pdf

You do know they continued the development past that point as has the rest of the world. Seriously, don't come on here quoting 1991 stuff as evidence of what is best practice today. It makes you look rather stupid and out of touch. 

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1 minute ago, Team_GBR said:

Hang on a minute. We are talking foiling boats. SLR is irrelevant!

You do know they continued the development past that point as has the rest of the world. Seriously, don't come on here quoting 1991 stuff as evidence of what is best practice today. It makes you look rather stupid and out of touch. 

SLR is somewhat relevant when you are designing for a specific takeoff speed-particularly low speed ,light air takeoff.

Show me a picture of a later development by the Decavitator team instead of just running your poorly informed mouth!!!!!

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22 hours ago, Doug Lord said:

why I waste my time with a complete ass like you beats the hell out of me...

I don't -generally- use Froude #'s in design work. I use the old "speed-length ratio"(1.34 X square root of the wl length) or as modified in Vellingas book- 1.5 instead of 1.34 for monohulls. Of course, if for any reason I needed a Froude number I would just multiply the SLR X .30........

The case rests for the prosecution. 

Thank you Doug. 

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2 minutes ago, mad said:

The case rests for the prosecution. 

What an uninformed idiot you are............

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6 minutes ago, Doug Lord said:

What an uninformed idiot you are............

Oh really? Uninformed about what exactly? You’re delusion, and  lack of hydro, aero, composite and basic engineering skills?

thats a given for all to see. 

Seek help Doug, you need it. 

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3 hours ago, Doug Lord said:

SLR is somewhat relevant when you are designing for a specific takeoff speed-particularly low speed ,light air takeoff.

Speed length ratio (SLR) is an approximation of the maximum practical speed for traditional displacement hulls based on their waterline length. Do you have some other definition?

There are many hull designs that can greatly exceed their SLR without planing. The SLR number is irrelevant for a modern high speed hull that is intended to foil unless the lift–off speed is close to the actual maximum hull speed.

The SLR for a Moth is 4.4 kn, none will start foiling at that speed so in theory Moths can't achieve sufficient speed to start foiling, which we all know is bollocks. Even using the higher 1.51 factor, the SLR is 5 kn so still a theoretical impossibility (except for maybe a couple of the very latest boats). But Moths (and many other dinghies) have been exceeding their SLR without planing for decades. The SLR for a 100' boat is 15 kn (using the higher factor), yet even 60' boats smash that. I used to travel to work on a 26m catamaran ferry that cruised, not planing, at 28kn, which is more than double its SLR.

If you're designing a foiling boat that should foil at 5 kn through the water or less, which apparently you're trying to do, then SLR is utterly irrelevant. What hull are you designing for a foiler where the actual hull speed is anywhere near 5 kn?

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As if we needed further evidence that Doug hasn't got a clue what he is talking about. Good job, everybody, but if Doug is to be believed, you are all uninformed idiots!:D

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1 hour ago, RobG said:

Speed length ratio (SLR) is an approximation of the maximum practical speed for traditional displacement hulls based on their waterline length. Do you have some other definition?

There are many hull designs that can greatly exceed their SLR without planing. The SLR number is irrelevant for a modern high speed hull that is intended to foil unless the lift–off speed is close to the actual maximum hull speed.

The SLR for a Moth is 4.4 kn, none will start foiling at that speed so in theory Moths can't achieve sufficient speed to start foiling, which we all know is bollocks. Even using the higher 1.51 factor, the SLR is 5 kn so still a theoretical impossibility (except for maybe a couple of the very latest boats). But Moths (and many other dinghies) have been exceeding their SLR without planing for decades. The SLR for a 100' boat is 15 kn (using the higher factor), yet even 60' boats smash that. I used to travel to work on a 26m catamaran ferry that cruised, not planing, at 28kn, which is more than double its SLR.

If you're designing a foiling boat that should foil at 5 kn through the water or less, which apparently you're trying to do, then SLR is utterly irrelevant. What hull are you designing for a foiler where the actual hull speed is anywhere near 5 kn?

Holy Crap - my I14 ain't a flyer, yet according to Doug is breaking the laws of physics. Dark Energy?   (might be a good boat name..  hmmm)

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5 hours ago, Team_GBR said:

As if we needed further evidence that Doug hasn't got a clue what he is talking about. Good job, everybody, but if Doug is to be believed, you are all uninformed idiots!:D

Not only us, but just about everyone else building flapless J or L foils. They've all gone to tapered, pointed tips, the reverse of Doug's clearly superior iFlap which goes in completely the opposite direction.

And who is putting big winglets on their flaps? The ones on his model are massively bigger than the tiny winglets on the full–sized Mach2 high lift foil (which was designed using CAD that Doug can only dream of).

M2F3FH__22741.1431250779.jpg?c=2&imbypas

So far ahead of the curve…

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As I said the SLR is "somewhat relevant"  when designing for low takeoff speed but the relevance depends on the L/B ratio of the hull or hulls contacting the water before takeoff and the size of the boat.

Moths are 10-11/1 L/B ratio, many other multihulls are 15-20/1. The L/B ratio of the  main hull of Fire Arrow is 6.6/1. The test model and full size version(19.5') are designed to take off in a 5 mph(model) or 5 knot(full size) breeze. Boat speed at take off for the model is about 4-5 mph-the SLR for the model is 3.5mph using Velinga's formula.

The SLR for the fullsize version is 6.62mph which is about what her projected takeoff speed would be in a 5 knot wind(5.75mph).

The SLR for the 15.5' WOLF is 5.59mph with an L/B ratio of 6.65/1 which corresponds to her estimated takeoff speed in a 5 knot wind.

The SLR is never more than somewhat relevant, even less so on models but an interesting reference for fullsize hulls with less than an about 8/1 L/B ratio for earliest takeoff target.

The relatively wide planing hull on Fire Arrow/WOLF keeps the main hull rocker small for clearance when flying and provides reserve buoyancy forward and planing area forward for incidental contact with the water at speed.

 

Note difference in rocker between Rave and Fire Arrow:

Rave pix from Hydrosail website/Dr.Bradfield--

Fire Arrow pix DL and Dan Burke---

 

Rave hydrosail site.jpg

MPX Fire Arrow-First Full Flying Foiling on video-7-24-14 012 (3) - Copy.JPG

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4 hours ago, RobG said:

Not only us, but just about everyone else building flapless J or L foils. They've all gone to tapered, pointed tips, the reverse of Doug's clearly superior iFlap which goes in completely the opposite direction.

And who is putting big winglets on their flaps? The ones on his model are massively bigger than the tiny winglets on the full–sized Mach2 high lift foil (which was designed using CAD that Doug can only dream of).

M2F3FH__22741.1431250779.jpg?c=2&imbypas

So far ahead of the curve…

What you ,apparently don't get, is that foil design depends  to a large extent on the operational RE for the foils and on the way they are intended to be used. So foils for the Moth and for the Fire Arrow Model are bound to be different. Further, the Fire Arrow foils are designed for very low speed takeoff as a priority not top end speed and are very experimental. For instance, the iFLAP allows the UptiP ama foil to work almost like a wand controlled foil(with no moving parts) with high lift at low speed and low drag at high speed.

The small endplates being tried on the partial span flap of the Fire Arrow main foil are experimental and based on an endplate installation on an airplane. They may not work beneficially at all because the characteristic of a partial span flap is that the change in lift can extend past the end of the flap and the endplate may prohibit that causing more drag ,not less. Then again because this partial span flap is longer than the adjacent foil chord that may not happen. Experimental!

MPX Fire Arrow experimental flap endplates-8-26-14 004.JPG

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6 minutes ago, Doug Lord said:

What you ,apparently don't get, is that foil design depends  to a large extent on the operational RE for the foils and on the way they are intended to be used. So foils for the Moth and for the Fire Arrow Model are bound to be different. Further, the Fire Arrow foils are designed for very low speed takeoff as a priority not top end speed and are very experimental. For instance, the iFLAP allows the UptiP ama foil to work almost like a wand controlled foil(with no moving parts) with high lift at low speed and low drag at high speed.

The small endplates being tried on the partial span flap of the Fire Arrow main foil are experimental and based on an endplate installation on an airplane. They may not work beneficially at all because the characteristic of a partial span flap is that the change in lift can extend past the end of the flap and the endplate may prohibit that causing more drag ,not less. Then again because this partial span flap is longer than the adjacent foil chord that may not happen. Experimental!

MPX Fire Arrow experimental flap endplates-8-26-14 004.JPG

Doesn’t experimental imply, well, experiments?

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On 4/30/2015 at 6:21 AM, Doug Lord said:

Doug, if you spent as much time building your dreams instead of arguing on forums you may have something worthwhile to contribute.

 

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5 hours ago, Doug Lord said:

the iFLAP allows the UptiP ama foil to ....

 

That's it, back on ignore.

This groundhog day DL foil shit and the VOR leg 4 thread are making me question humanity

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On 21/01/2018 at 9:55 AM, Doug Lord said:

why I waste my time with a complete ass like you beats the hell out of me...

I don't -generally- use Froude #'s in design work. I use the old "speed-length ratio"(1.34 X square root of the wl length) or as modified in Vellingas book- 1.5 instead of 1.34 for monohulls. Of course, if for any reason I needed a Froude number I would just multiply the SLR X .30........

Why do you waste your time coming here at all, literally 100% of people wish you would leave this forum, stick to boatdesign.net.

No one at all cares for you, no one cares about what you do, no one wants you here, no one wants to read your posts.

I can literally share thousands of posts about how stupid you, your model, your maths, or anything you do is. Yet have never seen one that says "Thanks for the images you posted".

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12 hours ago, darth reapius said:

Why do you waste your time coming here at all, literally 100% of people wish you would leave this forum, stick to boatdesign.net.

No one at all cares for you, no one cares about what you do, no one wants you here, no one wants to read your posts.

I can literally share thousands of posts about how stupid you, your model, your maths, or anything you do is. Yet have never seen one that says "Thanks for the images you posted".

Apart from a whole pile of vitriol and anonymous computer heckling, what may I ask do you bring to this forum ?

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21 hours ago, Liquid said:

 

That's it, back on ignore.

This groundhog day DL foil shit and the VOR leg 4 thread are making me question humanity

Plus 1!  I only had DL on ignore till the VOR threads but yea those have become as unreadable as well.  So much noise!!  This place is becoming a cesspool of attention whores.

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11 hours ago, Waynemarlow said:

Apart from a whole pile of vitriol and anonymous computer heckling, what may I ask do you bring to this forum ?

Absolutely nothing at all, I don't sail, nor do I design or build anything, I play with toys and post on the internet.

Oh wait, that's not me.

It's hilarious that you say I post a whole pile of vitriol while I have 400 posts and DL has 11500 posts...

Maybe, you should go through my old attachments or posts? Maybe you'd see some of the content I shared, only to have DL begin sharing it but with all his bullshit. So I have done the same thing to him.

The differences being I've posted some quality original content (some CAD sketches), answered some questions on boats I've owned and some for boats I've sailed in events, added some knowledge from my experience on building a few different things, some bullshit directed only at the people who I believe deserved it (which is like two or three people), and maybe just some general sailing/boating knowledge as I'm on the water around 100 times a year, and after all that have 400 posts total in 15 years of SA reading.

DL posting 11500 times, and posting one piece of original content (4 images) 5 years ago and re-posting that thousands of times since, re-posting other peoples content thousands of times (going as far as saying they copied him, when they haven't), the literal thousands of posts incorrectly describing how things work, how about the thousands of posts calling people an idiot, ill-informed, moronic, absurd (come one you must know all the stupid things he calls people by now right?) but all that at people who are well respected, how about when he says that to the people who literally run and moderate the forum, or even (I wonder if anyone remember this) but the time he called the moth world champion at the time an idiot when talking about moth foiling?

But that's cool mate, you obviously think someone posting a thousand times a year about how amazing they are when they haven't sailed in 10-20 years and all they do it post either bullshit or other peoples content here and play with toy sail boats on the lawn all day is far more important than someone who on the water almost daily, posts on here maybe 50 times a year total, has posted some helpful OC, joined in a few conversations they can help in, and hurled some insults at a couple of idiots when he thinks they deserve it (because fuck PC culture, sometimes the right thing to do is to call someone a moron to their face when they don't shut up, I mean do you let a child cry for hours in a restaurant over a desert they can't have anyway, or do you tell them to shut up or they get nothing at all?).

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12 hours ago, darth reapius said:

Absolutely nothing at all, I don't sail, nor do I design or build anything, I play with toys and post on the internet.

Oh wait, that's not me.

It's hilarious that you say I post a whole pile of vitriol while I have 400 posts and DL has 11500 posts...

Maybe, you should go through my old attachments or posts? Maybe you'd see some of the content I shared, only to have DL begin sharing it but with all his bullshit. So I have done the same thing to him.

The differences being I've posted some quality original content (some CAD sketches), answered some questions on boats I've owned and some for boats I've sailed in events, added some knowledge from my experience on building a few different things, some bullshit directed only at the people who I believe deserved it (which is like two or three people), and maybe just some general sailing/boating knowledge as I'm on the water around 100 times a year, and after all that have 400 posts total in 15 years of SA reading.

DL posting 11500 times, and posting one piece of original content (4 images) 5 years ago and re-posting that thousands of times since, re-posting other peoples content thousands of times (going as far as saying they copied him, when they haven't), the literal thousands of posts incorrectly describing how things work, how about the thousands of posts calling people an idiot, ill-informed, moronic, absurd (come one you must know all the stupid things he calls people by now right?) but all that at people who are well respected, how about when he says that to the people who literally run and moderate the forum, or even (I wonder if anyone remember this) but the time he called the moth world champion at the time an idiot when talking about moth foiling?

But that's cool mate, you obviously think someone posting a thousand times a year about how amazing they are when they haven't sailed in 10-20 years and all they do it post either bullshit or other peoples content here and play with toy sail boats on the lawn all day is far more important than someone who on the water almost daily, posts on here maybe 50 times a year total, has posted some helpful OC, joined in a few conversations they can help in, and hurled some insults at a couple of idiots when he thinks they deserve it (because fuck PC culture, sometimes the right thing to do is to call someone a moron to their face when they don't shut up, I mean do you let a child cry for hours in a restaurant over a desert they can't have anyway, or do you tell them to shut up or they get nothing at all?).

And how long did it take to consider and write that whole passage of how fuckin great I am, its been a long time since I've seen anything from you other than vitriol towards DL. In some ways I do agree with you but baiting as you do, does nothing but bring on the worst of responses from DL which just pollutes the thread even more.

To be on the water 100 times a year puts you into the professional sailor category, perhaps you could enlighten us on exactly what you do and where as that sounds a lot of days in a year to me.

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On 1/23/2018 at 12:02 AM, Doug Lord said:

What you ,apparently don't get, is that foil design depends  to a large extent on the operational RE for the foils and on the way they are intended to be used. So foils for the Moth and for the Fire Arrow Model are bound to be different.

Please don't make assumptions about what I do and don't get.

Quote

Further, the Fire Arrow foils are designed for very low speed takeoff as a priority not top end speed and are very experimental. For instance, the iFLAP allows the UptiP ama foil to work almost like a wand controlled foil(with no moving parts) with high lift at low speed and low drag at high speed.

The small endplates being tried on the partial span flap of the Fire Arrow main foil are experimental and based on an endplate installation on an airplane. They may not work beneficially at all because the characteristic of a partial span flap is that the change in lift can extend past the end of the flap and the endplate may prohibit that causing more drag ,not less. Then again because this partial span flap is longer than the adjacent foil chord that may not happen. Experimental!

I used the Mach2 2.3 foil as an example because it's designed expressly for high efficiency at low speed to get foiling early (i.e. exactly what you're trying to achieve). The winglets are not there for top speed so should indicate to you that where winglets are beneficial, they are very small.

Your iFlap is extremely draggy at low and high speed, the key to a high lift/drag ratio is not more chord but more span.

You only need look at real world implementations to see that the end–plated flap is not a good idea. Large commercial jets travel many thousands of kilometres per day, if there was even a 0.01% efficiency benefit to endplates on flaps, they'd have them. So if you ever manage to scientifically test your end–plated flap, I suspect all you will do is confirm that it's inefficient, i.e. the antithesis of what you want.

My guess is that you've used an oversized, short flap as an attempt to get more lift because it's cheaper and simpler to build than a full width flap and that the end plates are an attempt to address its obvious inefficiency. You should have gone for a much longer span with a full width flap, but then you'd need to build a new foil. To maximise efficiency, span is absolutely key. Gliders do not have short stubby wings with oversized flaps to generate lift.

Regarding foil design, Moths have been refining their foils for well over a decade and actually using them, across all boats, for thousands of hours per year in competitive racing. They are so highly refined that the cost of making them better is now prohibitive for all but a very few, and their price is so prohibitive that very few can afford new ones.

You claim to have based your foil design on Mark Drela's Decavitator, which set the human powered record in 1991. 27 years ago! It's now literally a museum piece (though apparently removed from public display in 2015). The foil is similar to a 10 year old John Ilett Fastacraft rudder design (say circa 2007), which might have been a good starting point, but had been well and truely superseded within in a few years.

If you want an extremely efficient, high lift, low drag foil, you should just copy one of the more recent Moth foils. If you want to do better through independent design, invest in some serious CAD and be prepared spend a lot of money and time designing, building and testing. You will never get there using thought bubbles and 2 hours sailing in 4 years. Further, any testing you do is unlikely to be as comprehensive or useful as the time others (and their customers) spend actually racing their foils against competitors.

So instead of theorising about yet another incarnation of a design riddled with issues, why not put your energy into building a foil that has a chance of doing what you claim you want to do?

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On 1/24/2018 at 2:06 PM, Waynemarlow said:

To be on the water 100 times a year puts you into the professional sailor category, perhaps you could enlighten us on exactly what you do and where as that sounds a lot of days in a year to me.

Not for nothing but I have been on the water 100 days for a number of years and I ain’t no professional sailor. Just somebody that loves the water and is fortunate to live near it. There are 52 weeks in a year. Just doing the weekend winter frostbiting and Wednesday evening summer beer cans got me half way there. Add in cruising, daysailing, and other racing.... 100 days easy. 

But this seems tangential to the topic of the Lord of Idiots son I will just say that Darth added lots of value to AC thread and shut up the idiots repetition and falsehoods. 

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On 25/01/2018 at 3:06 AM, Waynemarlow said:

And how long did it take to consider and write that whole passage of how fuckin great I am, its been a long time since I've seen anything from you other than vitriol towards DL. In some ways I do agree with you but baiting as you do, does nothing but bring on the worst of responses from DL which just pollutes the thread even more.

To be on the water 100 times a year puts you into the professional sailor category, perhaps you could enlighten us on exactly what you do and where as that sounds a lot of days in a year to me.

10 minutes, didn't say I was great or a professional as you seem to have read. Although I'm pretty damn good (that's beside the point, I'll leave people's opinion of me up to them once I've sailed with them), and would happily take someones money to sail/design/build for them (which is the definition of professional), but I sail for the love of it and not money (at the moment) as I make better money in an office working 40 weeks per year it gives me heaps and heaps of time to get out!

Apologies this took so long to reply, as we had a long weekend here, I took some extra time off and have been on the water about 7 of the last 10 days (not counting the fact I went out a couple of times on a couple of the days - like Sat/Sun, morning and arvo). I live like 200m from the beach, so a couple times kiting, had some fleet racing on little boats and some fleet racing on big boats, a couple twilight's, and on the couple mornings with no wind was out diving from my powerboat. We have damn nice weather in Australia :)

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On ‎30‎-‎4‎-‎2015 at 3:21 PM, Doug Lord said:

Dario Valenza along with many others (including me) has been doing much research on foils-particularly for the A Class.

This is a segment published Wednesday December 10, 2014:

 

Active foils with mechanical sensors tend to be at a disadvantage in light winds and marginal foiling conditions because there is a drag penalty associated with the control system.
In non-foiling conditions the sensors can be disconnected and retracted. But then no lift is available so any puffs would see the passive boat move ahead in foil-assisted mode.
Arguably the active setup is also heavier depending on where the sensors are located and how they connect to the foils.
 
So on a small cat the passive foil would have the competitive edge in very light winds.
The exact crossover remains a subject of investigation and will be found to depend on variables such as displacement/length ratio, sail area/wetted area ratio and the exact design of the foils...
 
Once foiling the active system requires less deliberate correction by the skipper.
This favours the less advanced sailor but probably makes little difference to the nuanced expert who is constantly making adjustments by muscle memory.
 
The crucial difference is this: An active foil can be smaller for a given takeoff speed because lift coefficient can be maximized when needed and dialed out when not required.
You can have an aggressively cambered foil on takeoff and a flat low-drag one at high speeds.
 
This is not impossible with passive foils. For example, the section used in the upper portion can have more camber than the one used near the tips.
But the compromise is more critical.
It is more difficult to have early takeoff and low drag at high speeds.
 

post-30-0-12354800-1430400251_thumb.jpg

post-30-0-87406200-1430400968_thumb.jpg

Has anyone investigated the use of little foils near the bows of a cat for anti-dive / going over the diagonal?

(or is this already covered somewhere in this thread) 

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I epoxied some surfboard fin boxes into the overlap of the sheer to deck joint on my Prindle 15 and then tried a couple of different sized skegs to try and keep the bow up when pressed hard. I didn't feel that it was very effective and I could just throw my weight back on the trap wire and pretty much yank the bows out just as easily. I never tried the long skegs that came out later for windsurfers because I didn't really want to slice and dice myself if I went 'asshole over teakettle'.  I could right that little P15 so quickly that I often got accused of deliberately pitchpoling so violently that boats behind me would slow down to see if I was OK and I would flip it up and take off leaving them far behind. That was my 'dead possum' strategy.

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25 minutes ago, Rasputin22 said:

I epoxied some surfboard fin boxes into the overlap of the sheer to deck joint on my Prindle 15 and then tried a couple of different sized skegs to try and keep the bow up when pressed hard. I didn't feel that it was very effective and I could just throw my weight back on the trap wire and pretty much yank the bows out just as easily. I never tried the long skegs that came out later for windsurfers because I didn't really want to slice and dice myself if I went 'asshole over teakettle'.  I could right that little P15 so quickly that I often got accused of deliberately pitchpoling so violently that boats behind me would slow down to see if I was OK and I would flip it up and take off leaving them far behind. That was my 'dead possum' strategy.

Thanks for your answer Rasputin, I can imaging that surfboard fins didn't have much effect on the pitchpoling.

With regard to righting your flipped P15, you touch a sensitive subject of me. Because once (30 years ago) I was like you, have my P15 in 20 seconds righted. Each afternoon I sailed, I flipped atleast three times, on purpose. But I'm now in my 72th year and I cannot do that anymore. Last spring I had to call for the lifeboat when I went over in a hard offshore wind.

Problem is, I don't have a normal tramp but a net, which catches no wind (or waves) so the cat will Always float with the sail in the undesired wind direction. Mast is sawnoff P19 mast and far too heavy to lift by one person. ( I broke so much P15 masts). I used to swimm fast to the mast top, lift it, place it in the direction to the wind, go fast back along the side stays, etc. I cannot do that anymore.

Do you have suggestions? 

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That p15 mast was a noodle with no spreaders. Light though and at 225 lbs I was far beyond optimum weight for the wee cat but was racing in the Virgin Islands and with good tropic trade winds could clean up on handicap. My nemesis on the race course sailed a P-18 and the handicap between the two was about right. He broke one of the bows on that P18 off and went up to a nice P-19. The handicap margin between it and the P15 was so great he could have finished and sailed back to the club and put the boat away and showered and be at the bar awaiting his cheesburger after a couple of beers before I finished and would correct out ahead of him. And this guy won the P19 Nationals in one design. I guess our reaching courses in St Thomas for the multihull fleet favored the boardless P15 and P18 over the dagger or centerboard boats without long windward legs.

    I have a P-18 now and hesitate to sail in singlehanded in anything over moderate winds. By the time I get your age, I would probably get a WETA.

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8 hours ago, northsea junkie said:

Has anyone investigated the use of little foils near the bows of a cat for anti-dive / going over the diagonal?

(or is this already covered somewhere in this thread) 

C-fly (a foiler) rests on steerable diamond foils at the front end which prevent pitchpoling. It should be possible to have the same idea at the front end without the boat resting on it all the time, thereby having less drag. This might also work on a non-foiler if the foils are above the waterline. Whether they need to be supercavitating like on C-fly, I don't know - that may only be necessary in breaking waves.

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49 minutes ago, Rasputin22 said:

That p15 mast was a noodle with no spreaders. Light though and at 225 lbs I was far beyond optimum weight for the wee cat but was racing in the Virgin Islands and with good tropic trade winds could clean up on handicap. My nemesis on the race course sailed a P-18 and the handicap between the two was about right. He broke one of the bows on that P18 off and went up to a nice P-19. The handicap margin between it and the P15 was so great he could have finished and sailed back to the club and put the boat away and showered and be at the bar awaiting his cheesburger after a couple of beers before I finished and would correct out ahead of him. And this guy won the P19 Nationals in one design. I guess our reaching courses in St Thomas for the multihull fleet favored the boardless P15 and P18 over the dagger or centerboard boats without long windward legs.

    I have a P-18 now and hesitate to sail in singlehanded in anything over moderate winds. By the time I get your age, I would probably get a WETA.

 

It's a pity that the WETA isn't an option for me. I sail on the Northsea in a place with shallow waters. So its too rough for a WETA, see my vids.

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15 minutes ago, David Cooper said:

C-fly (a foiler) rests on steerable diamond foils at the front end which prevent pitchpoling. It should be possible to have the same idea at the front end without the boat resting on it all the time, thereby having less drag. This might also work on a non-foiler if the foils are above the waterline. Whether they need to be supercavitating like on C-fly, I don't know - that may only be necessary in breaking waves.

 

Thanks David, I will look into that C-fly and see if this gives me ideas for my cat.

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14 hours ago, northsea junkie said:

Has anyone investigated the use of little foils near the bows of a cat for anti-dive / going over the diagonal?

(or is this already covered somewhere in this thread) 

It's been looked at for non foiling boats and hasn't gained any traction. You can get the same effect by adding winglets to the rudders. It transformed the A's when it was first done and allowed us to drive the boats far harder downwind.

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Hu??, that I don't understand. How can winglets at the transom side lifting up the bows? 

Or do they suc the transoms down?

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They suck the transom down only when the bow is pointing down, hence creating a negative AoA (angle of Attack) for the winglet

If your A-Cayt winglet is 0.30 meter span and 0.075 m average chord with elliptical leading edge and straight trailing edge you ll have an aera of (0.88 x 0.30 x 0.075)= 0.0198 sq meters

At Cl=0.5 around 4° AoA the downward lift would be around 250 Newtons @ 14 knts boat speed (equivalent to V^2=50).

But at  0 ° AoA  you have  0 lift and minimum drag

At the same time you can compute the pitching moment of the rig and compare them

According to Paul Bieker design philosophy rudder winglets contribute to minimize stern drag for planning boat like  I 14.

It increases the aspect ratio of the rudder blade which balances a little bit the increase in wetted area due to winglets.

 

Cheers

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Agree with the comments about how rudder winglet work, because as the bow goes down, the winglet produce "negative lift" pulling the back down and our friend Archimedes does the rest!

9 hours ago, Erwankerauzen said:

According to Paul Bieker design philosophy rudder winglets contribute to minimize stern drag for planning boat like  I 14.

It increases the aspect ratio of the rudder blade which balances a little bit the increase in wetted area due to winglets.

Careful you don't get concepts mixed up. The Beiker rudder winglets need to operate fairly close to the surface and this causes issues on cats which lift their windward hull. To get a benefit from the increased aspect ratio effect, you need the winglets on the bottom of the rudders, in a T format. This negates the "Bieker" effect.

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10 hours ago, A Class Sailor said:

Agree with the comments about how rudder winglet work, because as the bow goes down, the winglet produce "negative lift" pulling the back down and our friend Archimedes does the rest!

Careful you don't get concepts mixed up. The Beiker rudder winglets need to operate fairly close to the surface and this causes issues on cats which lift their windward hull. To get a benefit from the increased aspect ratio effect, you need the winglets on the bottom of the rudders, in a T format. This negates the "Bieker" effect.

Thanks both of you for filling the gap which I have concerning wingtheory. I really have to read more about that for a good understanding.

A practical problem for applying this winglets is that I'm a beachcat sailor on the Northsea. So in the start off the beach (but also in the landing) my rudderblades are almost horizontal because of the shallow grounds. That gives by the way an enormous pressure on the steering; which I can only decrease by letting the main almost completely open. So winglets on my rudder are impossible.

But a solution could be to mount winglets on the inside of the hulls near the transoms. I also have a sort of mini-beam ( a bar) behind the rearbeam which could serve as extra support. 

With regard to your calculation given for a certain winglet, I wonder if that size is enough for my purpose. When I'm facing a pitchpole ( or atleast having fear for it) I'm sailing full speed on a broad reach returning to the beach  with a running sea at my back. In that situation 25 kilogram (250 N) weight on the transom seems not enough. Sometimes I really have to go with my full weight just behind the rear beam to feel safe for antipitchpole ( but not for my equilibrum!).

By the way are these rudder winglets also used on the VOR boats because I see them also sort of automatically recover from bow-diving.

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"To get a benefit from the increased aspect ratio effect, you need the winglets on the bottom of the rudders, in a T format. This negates the "Bieker" effect."

 : I don't see why putting the winglet on the bottom of the rudder would negate your downward lift at 4° AOA !

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Pat,

I think A-Class Sailor means that if the winglets are not at the bottom tip of the rudder blades, they will not increase the effective aspect ratio relative to the geometric aspect ratio with the same efficiency.

AFAI Understood the Bieker effect: Even with the winglet at the bottom of the rudder blade like for International 14 skiff*, the low pressure at the top of the winglet (positive AoA and hence lifting force oriented upward), combined with the change in pressure under the hull, due to the stern wave (we are talking about monohull planing dinghies), contribute to a lower hull drag.

I guess , at least for I14,  the winglet has a multiple role:

1-Provides positive lift in most normal sailing conditions.

2-Contributes to a lower stern drag in the same normal conditions

3-Prevent nose diving as soon as the boat starts to pitch with a negative AoA

* Not sure, but for I14, I think the winglet span is not that different from stern width

To be sure we should post something on the SA dinghie forum, and ask skiff's specialists.

 

Cheers

 

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I put foils on my A Cat rudders before the 2002 Worlds on Martha's Vineyard. We had tested them on the C six years before, and had confirmed that with the rudder foils, pitchpoling was someone else's problem.  We didn't use them in the event because Duncan wasn't convinced they were faster across the entire range of conditions. We aligned the foils with a point just under the top of the stem.  This was something like+ 3 degrees.  So the foils would lift until the bow was about to disappear.

2002 was right in the middle of the "no hydrofoils" debate. Someone asked me what they were.  I said, " attention getting devices."

One notable race in the pre Worlds saw a NW front come though and the whole fleet save Me and Dave Brewer went over the handlebars.  Ashby's boat was cartwheeling away downwind when I stopped and picked him up, we gybed twice in about 25 before  Glen said "just drop me off in front of it" and did a Steve Irwin croc wrestling impersonation. I was so chuffed, I turned back upwind not knowing the race had been abandoned, a few minutes later, I pulled the downhaul that final little bit too hard and folded the mast up. Bugger.  Other than that, I had just tabbed Windsurfer skews to the rudders, they caught weed very nicely and were way too big.

The major benefit in on the 14 is different , and a bit less relevant to catamarans, but still significant.  The rudder foil on a 14 is big enough to carry about 1/2 the weight of the boat and crew. This allows the crew to move significantly aft, which moves th e LCG ( longitudinal  center of gravity) aft. This lightens the bow, so the boat rides easier through the waves. Further permitting the designers to eliminate flare and buoyancy forward.  On cats this is less critical because the hulls are not blunt instruments. The wave making effects are not critical because the catamaran has a displacement length ratio of about 1/2 of the 14.

The major reason why I chose to put the rudder t foils at the bottom is to keep the windward foil in the water instead of going in and out all the time which is a drag. 

SHC

 

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On 03/02/2018 at 11:11 PM, Erwankerauzen said:

AFAI Understood the Bieker effect: Even with the winglet at the bottom of the rudder blade like for International 14 skiff*, the low pressure at the top of the winglet (positive AoA and hence lifting force oriented upward), combined with the change in pressure under the hull, due to the stern wave (we are talking about monohull planing dinghies), contribute to a lower hull drag.

If you mount the winglets on the bottom of the rudder, you do not get the Bieker effect. It needs to be positioned in the main flow around the hull and that far away from the hull means that it isn't in the flow. How do I know? I still have a 14 rudder with winglets on the bottom of the blade. I had 2 rudders like that and I remember the transformation when I took the winglets off one rudder and put new ones on in the right place. It was like letting off the handbrake.

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On 03/02/2018 at 6:29 PM, northsea junkie said:

A practical problem for applying this winglets is that I'm a beachcat sailor on the Northsea. So in the start off the beach (but also in the landing) my rudderblades are almost horizontal because of the shallow grounds. That gives by the way an enormous pressure on the steering; which I can only decrease by letting the main almost completely open. So winglets on my rudder are impossible.

You might think so, but A's have been sailing like this for a number of years and they get off beaches like you are saying. When A's started putting winglets on rudders, before they started foiling, they were placed about 150mm up from the bottom like this

Large_RG030214218.thumb.JPG.a434c349d5c1a911f1ea0075e11b10b0.JPG

This size is all you need to stop nosediving and transform your boat.

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8 hours ago, A Class Sailor said:

You might think so, but A's have been sailing like this for a number of years and they get off beaches like you are saying. When A's started putting winglets on rudders, before they started foiling, they were placed about 150mm up from the bottom like this

This size is all you need to stop nosediving and transform your boat.

 

Thanks for your answer. 

The only way I can imaging for beach-starting with rudders like above, is having them up during starting. I assume that works for an A-Cat but really seems impossible for my beachcat because I have to steer also in the breaking waves (see my vids in the profile).

The winglets on the photo seem to have no real profile; is this true?  For now I'm thinking of placing such small foils near the stern on the inside of the hulls 10-15 cm above the bottom. Does that look possible according to you?

 

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Team BBR, I suspect your braking effect is the fact of hydroelasticity. The farther away from the rudder pintles, the bigger the stress induced by the foil's drag and the strain on the rudder blade will induce more AoA on the fence and induced drag. As for the flow around the fence, It could be effectively faster in the vicinity of the stern of a planning hull like I14, which is not the case for a catamaran hull.

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15 hours ago, northsea junkie said:

 

Thanks for your answer. 

The only way I can imaging for beach-starting with rudders like above, is having them up during starting. I assume that works for an A-Cat but really seems impossible for my beachcat because I have to steer also in the breaking waves (see my vids in the profile).

The winglets on the photo seem to have no real profile; is this true?  For now I'm thinking of placing such small foils near the stern on the inside of the hulls 10-15 cm above the bottom. Does that look possible according to you?

 

Again, you are wrong with your assumption. I have sailed out through breaking waves with the rudders part down. It adds extra drag in the fore and aft direction, but not steering which feels about the same with or without winglets. Of course, your transom and rudder fittings need to be strong enough, but when we started using winglets we fitted them to standard rudders and there weren't lots of breakages. You need to be careful with the latest A Class rudders, with the winglets on the bottom because they load up far more, but that is because they are close to double the length of what they used to be. The new boats have moved to dagger style rudders so it isn't a problem.

As for profile, those winglets are a proper aerofoil profile. It's just a matter of thickness as a percentage of the cord. They are probably only 6- 8mm thick which is hard to see in the picture

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On 2/3/2018 at 4:11 AM, Erwankerauzen said:

Pat,

I think A-Class Sailor means that if the winglets are not at the bottom tip of the rudder blades, they will not increase the effective aspect ratio relative to the geometric aspect ratio with the same efficiency.

AFAI Understood the Bieker effect: Even with the winglet at the bottom of the rudder blade like for International 14 skiff*, the low pressure at the top of the winglet (positive AoA and hence lifting force oriented upward), combined with the change in pressure under the hull, due to the stern wave (we are talking about monohull planing dinghies), contribute to a lower hull drag.

I guess , at least for I14,  the winglet has a multiple role:

1-Provides positive lift in most normal sailing conditions.

2-Contributes to a lower stern drag in the same normal conditions

3-Prevent nose diving as soon as the boat starts to pitch with a negative AoA

* Not sure, but for I14, I think the winglet span is not that different from stern width

To be sure we should post something on the SA dinghie forum, and ask skiff's specialists.

 

Cheers

 

4- reduces pitching. A lot...

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11 hours ago, A Class Sailor said:

Again, you are wrong with your assumption. I have sailed out through breaking waves with the rudders part down. It adds extra drag in the fore and aft direction, but not steering which feels about the same with or without winglets. Of course, your transom and rudder fittings need to be strong enough, but when we started using winglets we fitted them to standard rudders and there weren't lots of breakages. You need to be careful with the latest A Class rudders, with the winglets on the bottom because they load up far more, but that is because they are close to double the length of what they used to be. The new boats have moved to dagger style rudders so it isn't a problem.

As for profile, those winglets are a proper aerofoil profile. It's just a matter of thickness as a percentage of the cord. They are probably only 6- 8mm thick which is hard to see in the picture

 

Thanks again for your patience. But now I'm more and more confused; it seems so "contre-coeur" to hang a flat braking surface behind my sterns. Especially in the braking waves just after starting and having in that timeperiod too less speed for coping the incoming sea.

Maybe this also has to do with the difference between an A-cat and  my beachcat which has oldfashioned sort of Prindle like assymetric hulls.

You have me totally confused, but thats fine, you have me helped enormous.   I think, I still first try this little foils on the hull near the stern . 

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On 04/02/2018 at 3:13 AM, Steve Clark said:

I put foils on my A Cat rudders before the 2002 Worlds on Martha's Vineyard. We had tested them on the C six years before, and had confirmed that with the rudder foils, pitchpoling was someone else's problem.  We didn't use them in the event because Duncan wasn't convinced they were faster across the entire range of conditions. We aligned the foils with a point just under the top of the stem.  This was something like+ 3 degrees.  So the foils would lift until the bow was about to disappear.

2002 was right in the middle of the "no hydrofoils" debate. Someone asked me what they were.  I said, " attention getting devices."

One notable race in the pre Worlds saw a NW front come though and the whole fleet save Me and Dave Brewer went over the handlebars.  Ashby's boat was cartwheeling away downwind when I stopped and picked him up, we gybed twice in about 25 before  Glen said "just drop me off in front of it" and did a Steve Irwin croc wrestling impersonation. I was so chuffed, I turned back upwind not knowing the race had been abandoned, a few minutes later, I pulled the downhaul that final little bit too hard and folded the mast up. Bugger.  Other than that, I had just tabbed Windsurfer skews to the rudders, they caught weed very nicely and were way too big.

The major benefit in on the 14 is different , and a bit less relevant to catamarans, but still significant.  The rudder foil on a 14 is big enough to carry about 1/2 the weight of the boat and crew. This allows the crew to move significantly aft, which moves th e LCG ( longitudinal  center of gravity) aft. This lightens the bow, so the boat rides easier through the waves. Further permitting the designers to eliminate flare and buoyancy forward.  On cats this is less critical because the hulls are not blunt instruments. The wave making effects are not critical because the catamaran has a displacement length ratio of about 1/2 of the 14.

The major reason why I chose to put the rudder t foils at the bottom is to keep the windward foil in the water instead of going in and out all the time which is a drag. 

SHC

 

Thank you Mr Clark for bringing a more Cartesian rational analysis of the winglets

Thank you too Team GBR with your I14 experience, both help a lot to have a better understanding.

Northsea Junkie, you should not be discouraged:

In order to start from the beach in breaking waves with T foils at the bottom of the rudder blades , you might have to change the package including the rudder casing with vertical movement instead of pivoting movement for the rudde blades.

Depend also where the wind is coming from, and the waves size, sometimes it is possible to walk in the water until deep enought for the rudders down, push the  bow downwind, jump on the windward hull and lock the windward rudder first, get some clearance from the beach and waves before to tack and lock down the second one.

In this case you can use winglets at the bottom with the same casing and rudder blades it is probably the cheapest solution to prevent pitchpoling.

As precised by Mr Clark with winglets at the bottom, the windward one remains in the water  when flying a hull while it is not the case if positioned higher on the blade.

In addition, if the Prindle 15 paltform twists a little bit under rig loads the windward one might have the bigger effect.

 

Best regards

EK

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Woah!  This thread got interesting and informative.  And the disruptive one seems to have been silenced or otherwise given up.  Great to see and read useful dialogue!  Thanks to whomever made that happen however they made it happen!!

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1 hour ago, Erwankerauzen said:

Thank you Mr Clark for bringing a more Cartesian rational analysis of the winglets

Thank you too Team GBR with your I14 experience, both help a lot to have a better understanding.

Northsea Junkie, you should not be discouraged:

In order to start from the beach in breaking waves with T foils at the bottom of the rudder blades , you might have to change the package including the rudder casing with vertical movement instead of pivoting movement for the rudde blades.

Depend also where the wind is coming from, and the waves size, sometimes it is possible to walk in the water until deep enought for the rudders down, push the  bow downwind, jump on the windward hull and lock the windward rudder first, get some clearance from the beach and waves before to tack and lock down the second one.

In this case you can use winglets at the bottom with the same casing and rudder blades it is probably the cheapest solution to prevent pitchpoling.

As precised by Mr Clark with winglets at the bottom, the windward one remains in the water  when flying a hull while it is not the case if positioned higher on the blade.

In addition, if the Prindle 15 paltform twists a little bit under rig loads the windward one might have the bigger effect.

 

Best regards

EK

 

Thanks EK for your encouraging words.

I wish my sailing spot today was as simple as you described it. Please see my vid :   and directly skip to 3 min 15 for seeing the beachstart.

 

Thats also the reason why I have my rudderblades pivoting with the same locking mechanism as Prindle used.

Extra is the operation of the mechanism with ropes near the front beam,  to pull the blades down ( avoiding having to go to the sterns).

I'm however quite familiar with the sort of sailing spot which you describe. But I moved 15 years ago to the north coast where the shore is much more difficult. More's the pity.

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Since this thread is getting interesting again with a lot of good information in it, i would like to post the following question to everyone but Doug (who is on mute for the rest of eternity.)

I am building a radio controlled test bed that fits into the Mini40 / Formula 48 'box' so I can actually race it against others and learn.

What approach for foils would you recommend for this platform, where there is no 'manual intervention' from the controls?  focusing on a main hull with T rudder (may have trim on the foil to control pitch) and want controlled T foils with the wand up as far forward as possible. This is based on a design shared along time ago.

2 part question - is that the right platform (vs. cat with fixed z foils or the like)?

If that is the right platform, what should the details around the T foils look like?  (remember it is a 48inch box so we can't go crazy on width of the akas or span of the foils, so we may need to cheat using shorter span and end plates due to this limitation.)

Fire away!

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2 hours ago, Erwankerauzen said:

In order to start from the beach in breaking waves with T foils at the bottom of the rudder blades , you might have to change the package including the rudder casing with vertical movement instead of pivoting movement for the rudde blades.

@northsea junkie - you can check online videos and pictures of the Whisper from WhiteFormula. Rudder blades slide down on a rudder stock / casing. There's a couple of alternatives to hold them half-way-up; currently I clip them to the trapezes. Compared to the ease of use of a good kick up rudder it is awkward; but the tradeoff is worth it.

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8 hours ago, northsea junkie said:
12 hours ago, northsea junkie said:

But now I'm more and more confused; it seems so "contre-coeur" to hang a flat braking surface behind my sterns. Especially in the braking waves just after starting and having in that timeperiod too less speed for coping the incoming sea.

wish my sailing spot today was as simple as you described it. Please see my vid :   and directly skip to 3 min 15 for seeing the beachstart.

I honestly cannot see anything in that video that i could not sail through with my A with pivoting rudders and winglets like I posted above. Sure they add a braking effect, but it isn't that bad. They aren't so big as to be a problem. It will put more load on the transom and rudder fittings, but if they are strong enough, it won't be an issue. Remember, it doesn't add much to the steering loads which will always be high because the rudders aren't down.

I do not believe placing winglets on the hull will help. When the bow goes down, the stern comes up, and I cannot see how the winglets will work properly when that happens. Having them further down gives them some "leverage" and ensures they are never close to the surface.

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13 hours ago, northsea junkie said:

  I think, I still first try this little foils on the hull near the stern

This has been tried and wasn't very good. First time I know of it was with the old lowriding Moths when the Magnum 9.5 design had a pintail transom with winglets. They only built 2 boats like that before changing it to winglets on the rudders. Thye problem is that when the front goes down, the winglets at the back come out of the water. Sorry to say, i think you are wasting your time.

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6 hours ago, Team_GBR said:

This has been tried and wasn't very good. First time I know of it was with the old lowriding Moths when the Magnum 9.5 design had a pintail transom with winglets. They only built 2 boats like that before changing it to winglets on the rudders. Thye problem is that when the front goes down, the winglets at the back come out of the water. Sorry to say, i think you are wasting your time.

 

A Class and GBR you both are right. I have to stop being a bore. I'll have to do a little DYO and  try it. 

I come back.

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