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Author Topic: Doug Stout's stunt kite design tool  (Read 6733 times)
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RonG
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« on: April 25, 2012, 04:36 PM »

Anyone remember Doug Stout, and his mathematical approach to kite design?  Doug gave me a copy of the article he wrote about it circa 1995, and if memory serves there was a spreadsheet to go along with it as well.

He produced some interesting kites and was an active competitor on the US circuit back in the day.
« Last Edit: May 04, 2012, 11:28 AM by inewham » Logged
Doug S
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« Reply #1 on: April 25, 2012, 07:50 PM »

Ron,

Thank you for remembering me.  A few years ago I got back into kiting for the fun of it and built an updated 7-foot version of my Raptor (1995), called the Bird of Prey (2009).  I am very thankful to Jon at Sky Burners for helping me select the framing materials from his great SkyShark tubes for the two versions of the kite (Standard and Light Wind).  This past winter I started updating my old Geokite Program in the current version of Excel, which was originally written in Lotus 1-2-3.  The updated version will hopefully be able to capture and model the effects of the tail weight and active bridles in the current breed of stunt kites.  The update is currently on hold, since I have been expanded my kite enthusiasm into the world of no wind delta and canard soaring kites, where I also use Geokite to assist in the design process.

For those who have not seen my old article, the Geokite program’s main focus was to calculate aerodynamic centers of our unique flying platforms (i.e. geometry), while also calculating the center of mass for each component and mass balance of the design, so that you can estimate the final weight of the kite prototype and have it balance at the desired center of gravity and static margin.  The program also calculates a three point bridle as an excellent starting point for each design.  Since kite materials can be quite costly, the program saved me quite a bit of construction time and materials.  I only needed one prototype for each of my subsequent stunt kite designs that were sold under my boutique kite company, Falcon Aero Designs:  Falcon-SL (1992), Talon (1993), Talon-2M (1994), Raptor (1995).  In the fall of 1990 to the spring of 1991, it did take numerous modeled stunt kite designs for each prototype and 10 actual prototypes to calibrate and refine the program.  During this time, I experimented with using a leach line that was used in the 6th prototype, which also had a high aspect ratio.  The results of this initial work allowed me to develop my first contest ready stunt kite design (10th prototype) called the Falcon (1991), which I introduced to the stunt kite community while competing at the 1991 Wildwood, New Jersey Event.  With the Falcon, I also introduced the concept of a totally silent kite by using of a leach line, and all of my subsequent stunt kite designs used a leach line.

In closing, I wish to thank Ron for introducing me to this forum, which continues to be a great location for me to understand how our kiting community keeps pushing the envelope of designs with the incredible materials that we have to work with.  While working with Jon, I also acquired one his excellent Solus Stunt Kites.  Ron also introduced me to Will Sturdy and I have acquired one of Will's excellent Sabre II Stunt Kites.  This year I am hoping I can teach these old hands some new tricks.  Thank you again.

Sincerely,

Doug Stout
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« Reply #2 on: April 26, 2012, 10:22 AM »

Is it possible to have a look to this article & the program?Huh
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Doug S
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« Reply #3 on: April 26, 2012, 05:00 PM »

This excellent forum does not let one post a PDF file, which is the format my article is in.
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« Reply #4 on: April 26, 2012, 05:11 PM »

This excellent forum does not let one post a PDF file, which is the format my article is in.
Verily thou canst post a link unto a PDF.

Mike.
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« Reply #5 on: April 27, 2012, 12:32 AM »

I too would be very interested to see the article and Geokite, if you need somewhere to put it let me know. I can host it and put links on here.
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« Reply #6 on: April 27, 2012, 07:56 AM »

What Ian said, your post and previous posts have gotten my attention too and I would be very grateful to view any of your research you would share. Google Drive, MS Live/Skydrive, Dropbox or Ian's offer, dozens of free ways to share files now. I'd really look forward to seeing your research Doug.

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Doug S
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« Reply #7 on: April 27, 2012, 08:14 PM »

I sent Mike an E-Mail with a copy of my technical article so he can provide a link for others to download.

As to my current kiting distractions, the attached picture shows three canard kites I have recently built.  The top one is my version of Leong Ceewan's great Plutz kite design.  The one on the lower left is a larger version (4-foot wing span) with my preferences for sail shape and a front sail (black in color), which can be removed.  And as they say on the old Monty Python show "Time for something completely different," the one on the lower right is my sweep forward canard I call the Arrow.  All three glide great.  The sweep forward canard kite is a work in progress regarding framing stiffness on the canard wing, which I hope to have resolved when the wind becomes more reasonable.

Doug

« Last Edit: Yesterday at 08:56 AM by Doug S » Logged

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« Reply #8 on: April 27, 2012, 08:21 PM »

I  am not   much  into  Glider  Doug   but   dang  them  look   nice        some  times  I  wish  I  did  not  have  a  phobiea   of  sewing
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« Reply #9 on: April 27, 2012, 08:52 PM »

Here's Doug's Article he forwarded to me - I haven't gotten to look it over yet myself, I wanted to get it accessible for those interested. View it or right click and 'save target as' on Windows if you prefer.

Technical Article - Stunt Kite Aerodynamics by Doug Stout.pdf

*Cydonia - Sorry were are sort of polluting your thread, we get sidetracked sometimes and don't mean you any disrespect or intention to detract from your work either, I hope you find Doug's work usefull too - Mike

« Last Edit: April 27, 2012, 09:00 PM by mikenchico » Logged

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« Reply #10 on: April 27, 2012, 10:04 PM »

there's no problem for me. it is very interesting to compare with doug's work.
I could probably complete my file with this article.
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« Reply #11 on: May 04, 2012, 01:13 AM »

Doug has also shared his Excel sheet that he mentions above

Geometric Stunt Kite Comparison by Doug Stout - May 2 2012.xls

And his original article again to keep them in one spot
Technical Article - Stunt Kite Aerodynamics by Doug Stout.pdf

Many thanks again Doug for sharing all this info

Here's Dougs email

Mike,

I have been getting some questions on my stunt kite design article.  To assist our stunt kite design friends, I have attached my current version of Geokite 8 in Excel.  I have reformatted the input sheet.  I need to reformat the output and graphic equation sheets, and add other interesting things in the future.

As a treat to everyone and show them how the program works with real data, the file includes my old school Bird of Prey design, which shows how I use a model (equations within many of the cells) to automatically adjust the shape of the kite by only changing a few values.  Please post the link to allow our stunt kite design friends have fun with it, and take my years of work to the next level.  Have fun with it and thank you.

Sincerely,

Doug Stout


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Doug S
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« Reply #12 on: May 04, 2012, 06:58 AM »

Mike,

Thank you for posting for me, but Geokite was not included as one of the links.  To assist and as suggested by you, I setup a Google Drive for the files.  The following provides the links to my Technical Article, Geokite 8, and a comparison of my modeling efforts back in the 1990s.

      Smiley  Technical Article - Stunt Kite Aerodynamics by Doug Stout.pdf - https://docs.google.com/open?id=0B_TPx1W-lkmSRnZuQWJVbzFYRVk

      Smiley  Geokite 8 with Bird of Prey Stunt Kite Design - Program and Stunt Kite Design by Doug Stout - May 2 2012.xlsx - https://docs.google.com/open?id=0B_TPx1W-lkmSQ3dRQVdwaFBiZ0U

      Smiley  Geometric Stunt Kite Comparison by Doug Stout - May 2 2012.xls - https://docs.google.com/open?id=0B_TPx1W-lkmSOVFHZUM5dUdQTms

If anyone has any problems downloading the files, please let me know.  Please note that as a disclaimer, Geokite was designed by me for my sole use in modeling and designing kites many many years ago, but not in a place far far way.  I am not offering the program to be critiqued, but as a learning tool for others who wish to use modeling techniques to design kites.

To allow you see how Geokite 8 works with a real stunt kite, the file includes my modeling efforts for my Bird of Prey, which was modeled in 1999, updated in 2003, but not constructed with current materials and construction techniques until 2009.  My picture to the left is of my Bird of Prey.  Please note that I did not update the input values for the mass balance section, which is why the estimated and actual weight, CG and SM do not match.  When you have been modeling kites for a long as I have, a specific shape will provide a CG where desired.  Poor excuse, but I got lazy and I adjusted the CG with the Center Spine, as indicated in a sheet in the third link. 

Geokite uses 10 panels per side to allow for a curved LE and TE, and placement of the standoffs where I desire.  You will note that in many of the input cells there are equations the reference other cells on this sheet.  Using a spreadsheet allows me to build a mathematical model of the kite within the program, where you can change a few key parameters and the entire shape of the kite changes automatically.  Most of the equations in the input cells are in the Sail Shape Section and Material Center of Mass Location Section of the Input Sheet.  If you wish to measure one of your own kites or design from scratch, just enter your own data and input 0 in the unused cells.

With regard to my experience, it is my preference to have the end of the upper spreader (Upper Bridle Connection Point) and the inner standoffs align with the PAC, when using only two standoffs or four standoffs with the outer standoffs being near the lower spreader/wing spar connection point.  This preference normalizes the pressure of the air under different wind speed conditions (i.e. the rate of turn and control of the kite stays the same over different wind speeds).  You will note that a good starting point for a three point bridle is with the connection point over the PAC, which can be viewed in the Graphics – Top View.  This will provide a neutral moment arm when compared to the PAC.  I use an adjustable lower/outer bridle line to shorten this line and move the bridle line connection point outward to obtain the desired control.  In the Graphics – Top View, you will see that another preference is to have a 90 degree angle between the two lower bridle lines.

Regarding the depth of the sail, since many current trick stunt kites have much deeper sails than back in the late 1990s, the included model of my kite allows you to change the length of the inner standoff (Input Sheet:  Panel 4, Cell E29) or the outer standoff (Input Sheet:  Panel 6, Cell G29) and see how the depth of the sail automatically changes it shape when viewed in Graphics – Top View.  With the current breed of trick stunt kites using close together standoffs, I would have to update the model so that outer standoffs would be at Panel 5, and one could vary the span of this panel to adjust the standoff spacing.  Also, it may be prudent to align the PAC to be centered between the inner and outer standoffs when they are close together.  Just my thoughts and enjoy my old work.

Sincerely,

Doug Stout
« Last Edit: May 04, 2012, 08:44 AM by Doug S » Logged

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« Reply #13 on: May 04, 2012, 07:27 AM »

Sorry Doug guess I missed there were two different attachments in the last two mails. It was late last night  Sad 

Glad it got you to get into one of the free hosting arrangements available now. Hopefully you'll find it usefull in sharing your generosity in the future. Thanks again
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« Reply #14 on: May 04, 2012, 11:33 AM »

I hope you guys don't mind I've taken the liberty of splitting this thread and stickying both. Theyre both great pieces of work so its a good idea to keep them at the top where people can find them easily.

Thanks Cydonia and Doug  Cool
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