Date: Thu, 13 May 93 14:25:23 GMT From: cdt@zoo.bt.co.uk (Clive Dennett-Thorpe) Message-Id: <1993May13.142523.11760@zoo.bt.co.uk> Organization: BT Laboratories Subject: Bridling again - this time a Rogallo Parawing.... Ok all you bridling experts out there - the Rogallo parawing is not exactly obscure by any means but whenever I see examples of it in kite books it's made from mylar and is 15 inches square with absolute measurements. What I'd like to know is ...is there a formula based on the proportions of the kite which I can use it to scale it up to about a 1 metre square???? Regards, Clive Dennett-Thorpe = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: 13 May 93 15:06:47 GMT From: sc5@prism.gatech.edu (CSEPLO,STEPHEN P) Message-Id: <97419@hydra.gatech.EDU> Organization: Georgia Institute of Technology Subject: Re: Bridling again - this time a Rogallo Parawing.... In article <1993May13.142523.11760@zoo.bt.co.uk> cdt@zoo.bt.co.uk writes: > >Ok all you bridling experts out there - the Rogallo parawing >is not exactly obscure by any means but whenever I see >examples of it in kite books it's made from mylar and is >15 inches square with absolute measurements. > > >What I'd like to know is ...is there a formula based on >the proportions of the kite which I can use it to scale >it up to about a 1 metre square???? > Well, I don't know if there are any set formulas for scaling up, but I've had good success with other kite designs by adopting a standard measure for the kite (normally the spine) and then using it as a constant to compute the relationships of the other various elements (dimensions) of the kite design to the constant. That results in ratios for the dimensions of the various pieces. Then it is a simple matter of filling in the dimension that is selected for the adopted standard to figure out the other dimensions (ie, some simple algebra/trig is all you need (always new it would come in handy)). An example: You have plans for a rokkaku that is 5 feet tall by 4 feet wide. Adopting the spine as a constant, the spine becomes a ratio of 1 (5/5) and with width becomes a ration of .8 (4/5). Now knowing this, say I want to make a 3 meter tall rokkaku. The spine will be 3 meters and the width will be 2.4 meters (.8 * 3 meters). The same principle applies to the rest of the dimensions and the bridle. I assume when you reference 15 inches square to 1 meter square you are refering to the outside dimesions of the kite. For area, the computations will be a bit more involved. Good luck. Gentle breezes. -- The Mad Hata "Hey, Mon....Tako Kichi!" = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: 14 May 1993 01:21:14 GMT From: jeffy@syrinx.umd.edu (Jeffrey C. Burka) Message-Id: <1sus6a$2a5@hecate.umd.edu> Organization: University of Maryland at College Park Subject: Re: Bridling again - this time a Rogallo Parawing.... In article <97419@hydra.gatech.EDU> sc5@prism.gatech.EDU (CSEPLO,STEPHEN P) writes: >Well, I don't know if there are any set formulas for scaling up, but I've >had good success with other kite designs by adopting a standard measure >for the kite (normally the spine) and then using it as a constant to compute >the relationships of the other various elements (dimensions) of the kite >design to the constant. The only kite I've really taken the time to scale was my Tracer, of which I made a 3/4. I measured virtually every possible part of the kite and then multiplied the measurements by .75 and rounded where necessary. It worked like a charm. This is basically what you suggest, but it leaves out the middle step of figuring out scale ratios for each part. This has advantages and disadvantages. The main advantage is that it takes far less work. The main disadvantage is that you must repeat all the work if you want to make yet another size (whereas by computing ratios first, to create a new size, you only have to do a small portion of the work). > You have plans for a rokkaku that is 5 feet tall by 4 feet wide. >Adopting the spine as a constant, the spine becomes a ratio of 1 (5/5) and >with width becomes a ration of .8 (4/5). Sort of an odd example, as it sounds slightly off. Isn't a traditional rok made with a 6/5/4 ratio? 6 units tall, 5 units wide, and 4 units between the horizontal spars. In which case your 5' tall rokkaku should actually be 50" wide, not 48". (yes, I know, a small difference, but significant when you start scaling). Jeff (who's finally come up with some cool rokkaku designs but lacks the funds to build them...;-) -- |Jeffrey C. Burka | "When I look in the mirror, I see a little clearer/ | |SAFH Lite [tm] | I am what I am and you are you too./ Do you like | |jeffy@syrinx.umd.edu | what you see? Do you like yourself?" --N. Cherry | = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: 14 May 93 12:52:57 GMT From: sc5@prism.gatech.edu (CSEPLO,STEPHEN P) Message-Id: <97552@hydra.gatech.EDU> Organization: Georgia Institute of Technology Subject: Re: Bridling again - this time a Rogallo Parawing.... In article <1sus6a$2a5@hecate.umd.edu> jeffy@syrinx.umd.edu (Jeffrey C. Burka) writes: >In article <97419@hydra.gatech.EDU> sc5@prism.gatech.EDU (CSEPLO,STEPHEN P) writes: > >>Well, I don't know if there are any set formulas for scaling up, but I've Blah, blah, blah.... (much deleted) >The only kite I've really taken the time to scale was my Tracer, of which >I made a 3/4. I measured virtually every possible part of the kite and >then multiplied the measurements by .75 and rounded where necessary. It Another good and valid idea. >> You have plans for a rokkaku that is 5 feet tall by 4 feet wide. >Sort of an odd example, as it sounds slightly off. Isn't a traditional >rok made with a 6/5/4 ratio? 6 units tall, 5 units wide, and 4 units between Not necessarily. As per a recent KITING, the 6,5,4 ratio is appropriate, however a 5,4,3 ratio is also noted as being appropriate. To make matters even muddier, Schimmelphennig has different ratios and then Marizio Angeletti (sp?) has a different set of ratios. For that mater, so does Werner Backes as I recall (I'ld have to go consult my library and notes at home). Then, of course, you get to the previously noted published kite authors' measurements for the bow (front and back) and bridle and they are all different also. I suppose it all relates to the Japanese master kite makers who over years and years of experience, experimentation and development, have come to their own conclusions as to dimensions and what works best. As I understand the situation, these measurements are some of the most closely guarded "secrets" they possess. All in all, the most important part of rokkaku design is that they are symmetrical about the spine and symmetrical about the mid point horizontal. To be really traditional, the bridle should be either 4 or 6 leg with equal number of legs extending from the spreaders to a common tow point. What this means is that when you gather the upper or lower legs to a common point and then join the two common points with a single line, as is done quite often (I've even done this for a work shop I conducted because the bridle is easier to get to come out for better flight), it is a good bridle, and is the key to the flip flop flight method, but is not truly traditional. Oh well, I've gone on enough. Gentle breezes. -- The Mad Hata "Hey, Mon....Tako Kichi!" = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =