Foiler Design

Thanks Doug, that's great.

 

Doug, what happens as the foil approaches the surface? Is there just more drag or tdoes the lift decrease/increase as well? If both change using the effect for alltitude control becomes more complex.

 

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I've never experienced it either in models or fullsize(that I know about) but I would assume if the lift goes down("significant reduction in lift inside two chords") then the L/D ratio of the foil changes. I read somewhere that some Russian lake/river foilers used the effect as a form of altitude control.

 

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Here you go Terry-Tom Speer earlier in this thread......

 

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See this thread for a comparision of Mirabaud and Rocker: http://www.boatdesign.net/forums/sa...at-racing-rule-uccsrr-31154-2.html#post340040

 

Learning

OK, I've gone through 61 pages. I'd feel like I've followed foiling from it's birth, except that I remember when Longshot and Yellow Pages were the latest hot boats and Russell Long had the prototype Tri-foiler at the Atlantic City sailboat show, before he joined Hobie.

If I'm going to post, I have to have at least one question. I've downloaded vortex95 to my version of Excel 2007, which is set up for Macros and Visual Basic, but I get an error during the download process saying that I'm missing some Excel component. I haven't tried to use it yet, but I'm assuming it won't work. Can someone give any clues?

Now a comment. Seems the goal of this thread is to share knowledge and to learn. Could we maybe collect pointers to various resources? Is there some place to do that on this site? Would someone be willing to host the collection on their site? The eventual goal could extend to a joint VP program that would be generally available. Maybe a basic one that covered Moths for a start. People interested in more would at least have a starting point. I'm thinking it would be in Excel and would include ways to import the data you need from other programs. We could call it FoilerSpeed and it doesn't have to cover everything.

The Bill Beaver, John Zselecxky paper on the full scale testing of a hydrofoil moth is one resource. Another is Vortex95, if I can get it to work. A third is Xfoil and a 4th would be something on sail performance. The best I think I've seen is the Finn sail testing and other sail information in Marchaj's book Aero-Hydrodynamics of Sailing.

There has also been a lot of good information on control theory, but I think that's a separate program. We could call it FoilerStability and it would take input form the same sources, or from FoilerSpeed.

Until I put it down, this seemed like a simple idea. At least it's simpler than trying to jointly design a boat, but of course I have ideas there too. Today I'd just like a way to play with those ideas.

Comments?

 

It might be worth asking Jeff-the owner/moderator if we could have a "sticky" post at the begining of the thread that has references gleaned from the thread and other places posted and doesn't move.
There are lots of angles when considering foils and you touched on some. One important aspect-at least to me- is developing foiling systems that are easy to use and nominally crash free with top end speed a second priority-a refinement of technology that could lead to a "Peoples Foiler" someday.
At any rate, welcome to the thread-don't hesitate to contact Jeff-he may have an even better idea.

 

Peter: your version of Excel is likely missing a component of a more recent version. You could searching for it try the Microsoft web site, assuming you know the filename. I'm not a computer expert but I would have thought that, if your copy was registered you would have been getting automatic updates: this is a feature that can be turned on or off - you may want to check that.

Jeff is struggling with a number of forum issues right now and may not be able to respond to a request for new features immediately.

 

Hi Peter
I would have guessed the opposite with excel.. the vortex spreadsheet works perfectly with 2003. We had all sorts of problems getting macro's written in 2003 to work with 2007. Sadly i wasn't the one who got half of them to work.

I'm working on a spreadsheet, working through the hydrodynamics for a surface piercing system. A lot of the direction of the spreadsheet seems to be driven from the design. but equally changes the design. For example the 50 odd lines looking at neutral balance will only work for certain sail shapes, this then impacts on rudder and foil design but would be completely different if using multiple sails or twin rudders. It might be possible to get one working for a moth design with minimal variables but anymore and the number of variables becomes massive.

 

Doug said: "It might be worth asking Jeff-the owner/moderator if we could have a "sticky" post at the begining of the thread that has references gleaned from the thread and other places posted and doesn't move."

I'd like to call it "teach a man to fish", but "design resources" might be more obvious.

laurencet said: "It might be possible to get one working for a moth design with minimal variables but anymore and the number of variables becomes massive."

I think I realized this as I was writing. I think it would be best to start with those minimal variables. Something along the lines of the calculator at VB sails:

http://www.wb-sails.fi/news/SailPowerCalc/SailPowerCalc.htm#Results

but configured to work for a moth. The sail parameters might be fixed, but you could change foil dimensions, skipper position and/or other variables. Simplest would be to let you pick speed, sailing angle and that sort of thing.

laurencet also said: "We had all sorts of problems getting macro's written in 2003 to work with 2007." I suspected that because the spreadsheet was titled vortex95, not vortex2010.

 

Andrew McDougall

There is a rumor that "AMAC" designer of the Bladerider and Mach II Moths may be about to introduce new foiler designs that aren't Moths. This could be real interesting! Peoples Foiler maybe?
http://www.mcdougalldesigns.com/McDougall_Boats_Foils_Sails.html
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Most recent "Peoples Foiler" threads on boatdesign: http://www.boatdesign.net/forums/sailboats/peoples-foiler-ii-newest-boats-18010.html

 

How about attributing the "rumor" to Clean on Sailing Anarchy (at 7:39PM)? This wasn't your "scoop".

You even get honorable mention in the thread for the excitement it will cause you.

--
Bill

 

Peoples Foiler

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I appreciate your interest but you are wrong. For this particular story I have my own sources.

 

Mach II Techno

This is interesting:

"Caring for your foils...

We want to advise you that extremely high temperatures can have a detrimental affect on foils. If you sail in typically hot enviroments, or are planning on attending events in hot climates please be aware that your foils are highly technical pieces of equipment and accordingly care is need in looking after them.


Mach 2 foils are a pressurised and sealed unit. Adverse temperatures can damage this product.

Keep foil temperature under 50 degrees"--- must be Celsius=122degreesF

 

pV=nRT

The ideal gas law, combines Boyle's and Charles Laws. Once you seal an enclosed gas, increases in temperature will attempt to cause volume changes. Since volume changes are very limited, pressure increases are the result. At some point (obviously 50 degrees C), these pressure increases will result in failure of the sealed chamber at it's weakest point.

I guess they had to balance to problem of sealing the core versus the potential for water ingress. They chose to prevent water ingress and the result is temperature sensitivity.

50 degrees C isn't that high - many places will reach 35-40 degrees C ambient, and the black/carbon color of the foils will raise the spot temperature of the foils well beyond 50 degrees C in a 25-30 degree C summer day (@85-95 degree Fahrenheit). Bagging the foils in a light colored foil bag should be immediate once the boat leaves the water.

Everything in product development and engineering is an exercise in compromise and choosing the least problematic of multiple bad choices!

It is surprising the United States hasn't given up the ghost of the Imperial measure of temperature like the overwhelming majority of the world. I grew up with both, but am now far more comfortable with Celsius, even though it doesn't graduate as finely in Fahrenheit. I still have to translate temperatures for my parents so they understand what it means.

A couple pretty simple (and memorable) gauges: -38C = -38F (same), 0C = 32F (freezing), 16C=61F, 28C=82F. The 16/61 and 28/82 ones are remembered by flipping the digits, and unfortunately I get to see the -38 meeting point once or twice a year here in Ottawa.

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Bill