Date: Tue, 26 Sep 1995 07:55:30 -1000 From: Pierre Audette Message-Id: <449eqi$630@crchh327.rich.bnr.ca> Organization: Bell Northern Research Subject: Bell's Tetrahedral Kite: History and Plans Alexander Graham Bell's Tetrahedral Kite: The History Well, since I could not find any info on the net on tetra kites, I ended up going to the library to look it up. The best information I came across was from Bell's biography. It had a lot of interesting facts, as well as a copy of his original design notes. Here are some of the historical tidbits on the tetra kites: * Bell started developing tetras in 1902, and received a patent on it in 1904. * It started as an R&D effort for a powered and manned aircraft project. Bell's first concerns was for safety, so he was looking for an aircraft which could hover close to the ground at low air speeds while tethered. This way, the pilot, crew and passengers could disembark from a ladder. His thoughts was that in case of engine failure, the pilot could drop a line and anchor, and climb down while the craft was still in the air. It's only later that he went back to a more conventional airfoil design. The L/D was really not that good after all for an aircraft. * Bell started his work from the Hargrave box kite concept, after realizing that triangular structures are more rigid than square ones. * His basic description for the cells was a 'triangular cone'. It's only later that he found that the proper name for the shape he had was tetrahedral. * Each cell consisted of a three sided pyramid, with four faces, where two faces are covered with fabric. It's hard to visualize, and Bell couldn't even draw it in his notes. * His design was based on cells with 10 inches sides for the triangles. The minimum number of cells needed to make a kite is four. With the two on the top side by side, and the two on the bottom in line. * In 1905, Bell built a prototype with 1300 cells in two banks side by side. When the winds got about 10 mph, he manage to lift a 165 lbs man from the line to a heignt of about 30 feet. This was enough to convince him that his design created enough lift to fly a man and motor. * In 1906, after creating the 'Aerial Experiment Association' group, he built a kite with 3400 cells with floats, which carried a man while the kite was towed by a samll boat. It raised to 168 feet and hovered for seven minutes until the wind dropped. The kite (and man) then descended slowly towards the water 'gently as a butterfly'. Unfortunately, when it touched the water, the line was not disconnected, and the kite was dragged to pieces. The passenger managed to clear the wreckage unhurt. This was the last tetra kite experiment Bell attempted, since the AEA decided to pursue their work on a biplane design instead of the tetrahedral aircraft. All of this took place about the same time the Wright brothers were tinkering in their bike shop on their own design. * The tetrahedral was also used for construction purposes. Bell built a tower from four feet cells, into a tetrahedron shape with 72 feet legs, with half inch iron pipe. The structure was raised from the ground, by adding cells from the bottom without the assistance of a crane. This became the birth of space frame architecture. The Plans: Based on the pictures and sketches I've seen, I will attempt to draw and explain the four cells kite design (not an easy task in ascii characters). cell 1 2 1,2 ________ /\ \ /\ / / a\ a= Cell surface covered with fabric. \/__\/ <--a /____\ Visualize each cell as a 'V'. When \ / /a\ /a\ viewed from the front, cells 1 and 2 3,4 \/ <--a /___\/___\ are side/side. Cells 3 and 4 end/end. 3 4 Each 'V' is made of 2 triangles, long edges at the bottom, tips on top. Front/Rear View Side View Each cell should be made with equilateral triangles. Cells can be added, but typically maintain an equilateral framework. The four cells can be made with six spars (or struts), which creates a three sided pyramid. Start with three spars to make a triangle, then use the remaining three to finish the pyramid. They are then connected at their midpoint with the subdividing spars. Each 'V' surface is covered with fabric, on the inside and outside of the framework. You end up with uncovered inverted 'V' structures. The bridle: It's attached at both ends of the lower edge of the framework (ends of cell 3 and 4). The length of the briddle should be 2 times the length of the lower edge. Put at loop at 5/9 of the length of the briddle. The short end then becomes the front. Additional lateral lines can be added to improve the stability of the kite. They are attached from the loop to the upper side corners of the kite, but do not change the position of the loop. Flying: Launching should be done with a helper, by tossing it gently into the air while pulling in the line until the kite gains altitude. About one hundred feet of line is recommended. If the kite nosedives when it gets overhead, the front of the briddle should be lengthened (or the rear shortened). Construction: Easy and low cost if you are using 1/8 inch wooden dowels. Just lash the ends with thread or wire. When covering the kite, do not distort the framework, and eliminate any wrinkles. You don't need to cover the surfaces right over to the corners, a half inch opening is acceptable. Portability of this type of kite is most likely the reason for its limited popularity (try to handle a 3400 cells kite like Bell did). However it can be broken down in sections. Say you have a 16 cells kite, it can be made with four 4 cells sections, and tied together at the flying site. That's all I have for now. I will be building a four cells kite shortly, and will test this almost century old design. Happy winds, Pierre. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 26 Sep 1995 20:20:41 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Bell's Tetrahedral Kite: History and Plans Pierre Audette writes: > Here are some of the historical tidbits on the tetra kites: > [*Excellent* summary deleted] You overlooked how advanced the design is. There are two main advantages of the design. 1) Strength to Weight ratio. To make a single cell requires several sticks. When you start packing them together, they share the sticks, until on a large grid, you aproach an average of merely 1 stick per cell. This has been written up in the Kiteflier and Drachen, but I can't find either article this morning. 2) Stability. A normal kite becomes unstable when the line is short in relation to the size of the kite. With an Indian, this is with just a few feet of line. With something big enough to lift a 200lb payload, it becomes unstable many tens of feet off the ground. The many cells tend to act like a bunch of little kites, and thus the kite remains stable on a very short line. Andrew -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this->| Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome/index.html 80+ chrs/line looks messy on many screens. Often too messy to bother reading. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Wed, 27 Sep 1995 15:09:28 -1000 From: emcair@emc2.win-uk.net (Maurice Cairnduff) Message-Id: <6@emc2.win-uk.net> Subject: Re: Bell's Tetrahedral Kite:History and Plans REPLY-TO: emcair@emc2.win-uk.net We have been experimenting with the Bell tetrahedral kite format for the past year as an environmental design project to demonstrate the educational and recreational possibilities of re-using a variety of post consumer waste materials. Our experience is that tetrahedral kites can be constructed at zero material cost and can be flown using a single line without bridle. We find the tetrahedral kite design stable and remarkably resilient. Even using low strength materials, the multi-cell nature of the design allows kites to remain flyable after sustaining damage in heavy landings in force 5 winds. The scaleability and simplicity of construction potentially lends itself to large scale educational and / or community kiting projects. If anyone is interested in receiving our tetrahedral design specifications, constructed using re-use post consumer waste, we will happily make the design available by e-mail at a modest charge. Contributions will be gratefully received to help us further our research in developing low energy designs for the re-use of post consumer waste materials. regards Maurice Cairnduff = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Fri, 29 Sep 1995 06:20:27 -1000 From: gilchgw@zoology.washington.edu (George W. Gilchrist) Message-Id: <44h6cb$r60@nntp4.u.washington.edu> Organization: University of Washington Subject: Re: Bell's Tetrahedral Kite:History and Plans In article <44e2sr$kus@crchh327.rich.bnr.ca>, pierre.audette.qupxa01@nt.com says... > >Maurice, care to share where you connect the single line to the kite w/o a >briddle? > I don't know if Maurice will respond, but I will. The line for the tetra is attached at a single point, the apex of the kite. While it is easier to make a dacron loop with a knot or metal ring to attach your flight line to, there is no reason you could not just tie the line to the kite. There is no additional bridling required for the tetrahedron kite. Cheers, George -- ============================== George W. Gilchrist gilchgw@zoology.washington.edu University of Washington Department of Zoology Box 351800 Seattle, WA 98l95-1800 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Fri, 29 Sep 1995 05:32:23 -1000 From: samef@shout.net (Sam Francis) Message-Id: <44gsul$ebf@treflan.shout.net> Organization: Shouting Ground Technologies Subject: Re: Bell's Tetrahedral Kite: History and Plans DHAXTON@SSSP.GSFC.NASA.GOV (Donovan Haxton) wrote: good stuff clipped >The Wright brothers considered this young man a spy from the 3Bell Group2. >They really didn9t want anything to do with him. However, the Army said >that they did not want to obtain an airplane unless it carried two people. >This young man apparently was the only one in the Army who could clam to >have flying experience (i.e., from the Bell Kites) , so therefore it was >requested that he be the passenger in the demo flight. >I am sorry but I don9t remember the young officer9s name. Maybe someone >can help me. Don, The passenger was US Army Lt. Thomas E. Selfridge, who has the destinction of being the first fatality of powered flight, when he crashed with Orville Wright and died. Sam = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sat, 30 Sep 1995 08:29:48 -1000 From: samef@shout.net (Sam Francis) Message-Id: <44jrnb$k3k@treflan.shout.net> Organization: Shouting Ground Technologies Subject: Re: Bell's Tetrahedral Kite:History and Plans gilchgw@zoology.washington.edu (George W. Gilchrist) wrote: >I don't know if Maurice will respond, but I will. The line for the tetra is >attached at a single point, the apex of the kite. George, I have seen Tetras 'bridled' this way too. More often they are bridled nearer the top 250f the leading edge. "Leading edge" being the entire stacks' leading edge. A 4 cell high stack may be bridled at the bottom of the top cell. A single cell might be bridled 1/4 of the way down the leading edge. I suspect this would give much more lift in less air due to the stack not laying back so far. A 2 legged bridle gives you much more flexibility here. My 2 pennies, Sam = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sat, 30 Sep 1995 11:59:53 -1000 From: emcair@emc2.win-uk.net (Maurice Cairnduff) Message-Id: <7@emc2.win-uk.net> Subject: Re: Bell's Tetrahedral Kite:History and Plans In article <44e2sr$kus@crchh327.rich.bnr.ca>, Pierre Audette (pierre.audette.qupxa01@nt.com) writes: >Maurice, care to share where you connect the single line to the kite w/o a >briddle? > >George Gilchrist over in Seattle hit it on the nose with his advice to connect a single control line to the apex of a tetrahedral kite. As non-technical kite fliers we are impressed by the simplicity and effectiveness of this control line attachment and the natural flying stability inherent in the tetrahedral kite's geometry. They can on occasions flip over and fly inverted for short periods before righting themselves. Maybe someone can contribute some more technical insight. regards Maurice Cairnduff = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 2 Oct 1995 08:04:23 -1000 From: Pierre Audette Message-Id: <44p9j7$i0n@crchh327.rich.bnr.ca> Organization: Bell Northern Research Subject: Re: Bell's Tetrahedral Kite:History and Plans Just to make sure on the terminology, I'm assuming that the apex is the forward and lower tip of the front bottom cell (or 'V'). Right? With the model I just built with the front and back briddle arrangement, It seems to have some serious imbalance. The kite flies on an angle instead of flying straight. I suspect the geometry isn't quite symmetrical. Are there any tricks to balance these kites, short of starting from scratch? Does the single line attachment minimize these problems? Regards, Pierre. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Wed, 4 Oct 1995 23:37:11 -1000 From: pat@cs.strath.ac.uk (Patrick Prosser) Message-Id: <450907$161@todd-06.cs.strath.ac.uk> Organization: Comp. Sci. Dept., Strathclyde Univ., Glasgow, Scotland. Subject: Re: Bell's Tetrahedral Kite: History and Plans For a technical discussion on Bell's kites see P. PROSSER, "Observations on tetrahedral kites" The Kiteflier, Newsletter of the Kite Society of Great Britain, Issue 54, 20-24, January 1993 P. PROSSER, "Beobachtungen zu tetraedischen Drachen" Drachen Magazine, Summer 1993 They give a brief history of Bell's kite work, a review of a paper written by Bell in National Geographic, some mathematics associated with his kites, and something that he overlooked (ie. just how effective the structure is as its size increases) I'm sorry, but I did not do it in latex and I do not have a copy that I can post. Patrick = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 5 Oct 1995 15:46:23 -1000 From: dickbell@netcom.com (Dick Bell) Message-Id: Organization: NETCOM On-line Communication Services (408 261-4700 guest) Subject: Re: Bell's Tetrahedral Kite:History and Plans I have always flown my tetra from a single point without a briddle. Just take a loop of string about 4 inches long and larks head it to the apex of the kite. The kite will fly as if it were an upside down pyramid. Of all the kites that I have. The tetra has always stopped more traffic. People just dont get to see that many tetras in the air. they are way cool. The tetra that I fly was designed by Spencer Chun and I know that Randy Tom flys his design also. One of the best designed tetras I have ever seen. It folds up to a triangle with sides of two feet. very easy to carry. -- -------------------------------------------------------------------------------- Dick Bell dickbell@netcom.com Dallas, Texas = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 8 Oct 1995 14:06:13 -1000 From: Mark de Roussier Message-Id: <813222373snx@murder.demon.co.uk> Organization: damage Subject: Re: Bell's Tetrahedral Kite: History and Plans In article <450907$161@todd-06.cs.strath.ac.uk> pat@cs.strath.ac.uk (Patrick Prosser) writes: > For a technical discussion on Bell's kites see > > P. PROSSER, "Observations on tetrahedral kites" > The Kiteflier, Newsletter of the Kite Society of Great Britain, > Issue 54, 20-24, January 1993 > > P. PROSSER, "Beobachtungen zu tetraedischen Drachen" Drachen Magazine, > Summer 1993 > > They give a brief history of Bell's kite work, a review > of a paper written by Bell in National Geographic, some mathematics > associated with his kites, and something that he overlooked > (ie. just how effective the structure is as its size increases) > > > I'm sorry, but I did not do it in latex and I do not have > a copy that I can post. Well if you had done it in latex this would be the wrong group to be posting in...:). -- Mark de Roussier ******************************************* I do not want people to be very agreeable, as it saves me the trouble of liking them a great deal. Jane Austen. ******************************************* = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 22 Oct 1995 14:28:15 -1000 From: aqualieb@aol.com (Aqualieb) Message-Id: <46eniv$a3f@newsbf02.news.aol.com> Organization: America Online, Inc. (1-800-827-6364) Subject: Re: Bell's Tetrahedral Kite: History and Plans I posted an item to this group about a week ago that didn't appear. I'm surprised. It delt with the issue of "tetrahedrals." I'm looking to find out if there are any of you out there that build or buy tetrahedral kites. I've built about a dozen over the past twenty-five years, and I love the kite. I curious about others' experience with them. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 23 Oct 1995 05:42:28 -1000 From: neitzke@elk.miles.com (Robert C. Neitzke) Message-Id: Organization: Bayer Corporation Subject: Re: Bell's Tetrahedral Kite: History and Plans At the WSIKF this last August I met a couple who were competing with a tetrahedral kite. They shared their card and I will now share it's details with you. Skip & Jan Herzog 3474 West 6975 South West Jordan, Utah 84084 Give em a shout They were a very nice couple and could possible share their experienceswith you. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 26 Oct 1995 06:25:22 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Bell's Tetrahedral Kite: History and Plans aqualieb@aol.com (Aqualieb) writes: >I'm looking to find >out if there are any of you out there that build or buy tetrahedral kites. Since you mention it, I have a copy of Patrick Prosser's excellent paper on the mathematics of these kites, access to a scanner and optical character regognition software and his permission. Some time soon I'll get my act together and make it available on the web. Andrew -- New to rec.kites? START HERE! | To: www@kfs.org send an email message like this-> | Subject: service /-\ () >< () |\/| () >< () /-\ | http://www.kfs.org/kites/welcome Psst! Wanna buy a roll of white, wide, Carrington seconds? gimme a call! = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sat, 28 Oct 1995 13:30:31 -1000 From: dlw@odi.com (Dan Weinreb) Message-Id: Organization: Object Design Inc., Burlington, MA Subject: Re: Bell's Tetrahedral Kite: History and Plans In article andrew@tug.com (Andrew Beattie) writes: Since you mention it, I have a copy of Patrick Prosser's excellent paper on the mathematics of these kites, access to a scanner and optical character regognition software and his permission. Some time soon I'll get my act together and make it available on the web. Was the paper published in a journal? If so, could you provide the citation? In fact, where might papers about mathematics of kites be published, anyway? Thanks! = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =