mollusc 0 #1 April 23, 2003 I saw that Aerodyne research has launched a new value for measuring canopy ellipticity, namely the planform factor or Pf, by using this formula: Pf=(1-(end cell chord/center cell chord))x(#tapered cells/#total cells)x100 In my opinion this does not give any new understanding of the canopy at all. What I would like is a value for canopy flying characteristics, performance or radicallity, not the planform. I know that planform is one of many variables regarding flying characteristics. Pf is actually misleading in some cases if you believe it would help you make a sound decision regarding flying characteristics (as they claim). Some examples: Crossfire2 21.6 Safire2 16.4 Stiletto 13.3 Sabre2 5.4 Anyway, the idea trying to find a way to calculate flying characteristics is good. Using this formula though.....I would give it an E. Quote Share this post Link to post Share on other sites
skygod7777 0 #2 April 23, 2003 the person to ask about this would be Ian Bellis. he posts on here (i think he just started). i'm sure he will enlighten us on this. if not, i'll send out an e-mail to my buddy dominic that works at aerodyne. and see what he has to say. later Quote Share this post Link to post Share on other sites
Professor 0 #3 April 23, 2003 Does it seem to anyone else that this gives undue weight to the number of tapered cells? The Safire 2 is marketed as being fairly forgiving, and has quite a bit less taper than a stiletto, but has a noticably higher Pf, just because all of it's cells are tapered. Seems like it's the end cells that really matter anyway, since that's where the control lines connect. I didn't realize the springo was so radical. Too bad we can't get that frog stuff over here, sounds like fun. Ted Like a giddy school girl. Quote Share this post Link to post Share on other sites
ibellis 0 #4 April 24, 2003 The Planform Factor (Pf) was a concept I introduced at the PIA Symposium. It is still a "work in progress" The idea was to get all manufacturers to standardize on a method for objective comparison of planform, since there has been so much marketing hype surrounding this characteristic. I know what you are thinking and yes, I take my share of the responsibility for this. The fact is that semi-elliptical, dual tapered, slighly elliptical, PRO Taper, fully elliptical, etc, etc mean nothing. A "semi-elliptical" canopy can have more taper than a "fully ellipitical" one. The Pf addresses this by quantifying the change in chord from center to wingtip along with the amount of the total wing that distributes this change (number of cells or percentage of total span). These two factors are very important in terms of defining the amount of ellipticity. There are more (leading edge taper vs. trailing edge taper for example) as well as many other characteristics trim angle, airfoil shape, etc. etc. that affect the canopy's performance characteristics. The goal for now is to establish some standards and expand from there. Eventually we may get to a point where the consumer can actually be confident they are comparing known entitites. Remember, as it stands right now, when comparing two canopies from two different manufacturers, you may not even be comparing similiar sized wings, although the labels tell you that you are. I have been in contact with George (Galloway) who has the unenviable task of trying to rewrite PIA TS-104 (measurement standards) and come up with something all manufacturers will agree to. I have suggested we include Pf along with a standard for Span, Chord, etc, so that consumers are comparing "apples to apples" or are at least aware of where some of the differences lie. The amount of taper over the entire wing (not just the end cells) does have a significant affect on flight characteristics. For example, one friend (designer from another company) agreed with me and stated that 1/2 degree of taper on the thrid cell inboard from the end cell, was enough to noticeably change the characteristics of a particular design of his we were discussing. I hope this answers some of the questions. Blue skies, Ian Bellis President Aerodyne Research Corporation Quote Share this post Link to post Share on other sites
skymedic 0 #5 April 24, 2003 Thanks for clearing that up for Ian...well clearing it up as much as you can for now. it is a good concept...problem is in the delivery for now...but I'm sure you'll tackle it just fine. I love DZ.com due to the fact that all of the big names are here and can answer directi questions and concerns. marc Quote Share this post Link to post Share on other sites
Professor 0 #6 April 24, 2003 Quote The idea was to get all manufacturers to standardize on a method for objective comparison of planform, since there has been so much marketing hype surrounding this characteristic. Agreed, completely. Quote known entitites. mmmmmm, tities...... Quote The amount of taper over the entire wing (not just the end cells) does have a significant affect on flight characteristics. No doubt, but it seems like you're trying to define a set of complex and interconnected characteristics into a single number. Wildly different canopies can end up w/ very similar numbers, and there's no explanation of what Pf means to the jumper (higher Pf = more responsive? more lift? faster turns? more sensitive openings?) That's what people really care about, in the end. The only way that you can really communicate all of the planform intricacies to the jumper is to give them all the dimensions, and 90% of jumpers wouldn't know what to make of that anyway, and that's without thinking about trim and airfoil and such. Anyway, I applaud your efforts to clear up the inconsistencies and marketing-speak surrounding canopy design, it's a herculean task and I wish you luck. Thanks for coming here and explaining this, as well. Keep up the good work Ted Like a giddy school girl. Quote Share this post Link to post Share on other sites
