Reply to Yuri:
> ...Therefore, you could define "the best flight capability of that particular canopy", but not the wing - it will be a different wing for the different flight modes...
Yes, what I meant is "wing" in a general term. Obviously at each amount of brake applied it varies slightly (or greatly!) the shape of the canopy. Still it remains our only "wing"!!!
> A major disagreement: full flight mode does not give you the best glide ratio on a majority of the
canopies.
Yes, you are right indeed, Yuri. I just said so to semplify. It is true that the best glide ratio is achieved with a little bit of brakes applied, or, better, with a little bit of
risers pulled down. Again, what I meant, simplifying, is that there is ONE SINGLE "CONFIGURATION" for a given "WING" that achieves the best glide ratio. For a rigid wing, it is THE pitch that gives you THE maximum efficiency. For a "soft" wing like our parachute, it is THE amount of brakes (or, better, THE amount of pull on rear risers) that gives you the best glide ratio. Anything different from what above, yields a "worsening" of the "best glide ratio".
You are very precise, Yuri. What I meant with my long post above, is that any "wing", rigid or soft that could be, has its OWN UNIQUE "GLIDE RATIO", that can be reached ONLY in a certain "configuration". For our parachutes, we can say that we have the "glide ratio1" if we are using a little bit of brakes and we have "glide ratio2" if we are pulling down a little bit the risers. For sure, it holds true that: "glide ratio2" > "glide ratio1".
Any other "configuration of brakes" (or risers that could be) gives you a worsening of the best glide ratio. I.e.: to use the glide ratio of your canopy, you must stick your hand in a given position (=amount of brakes) and not moving from there (apart from correcting the route or turning).
And to end up this story, I would simply like to say that what we would want in a BASE canopy is the highest possible glide ratio!!!! And finally, we SHOULD know at which "brake amount" we get this famous "best glide ratio"!!! In fact, when I am in doubt about reaching the designated landing area of our
terminal wall (low pull, but, you know,
tracking is so fun!!!), I simply attach myself on rear risers and look carefully if I am going to make it...!!!
To Bryan:
I would like to say in advance (without any willingness to offend one of the best BASE jumpers in the world) that Dwain's numbers (around 2.6) of glide ratio for Fox and Mojo seems slightly high, if we consider that PD gives for a Sabre a glide ratio of 2.7, being a Sabre "thin" as profile (=less drag) and ZP made (=less surface induced drag).
When you say:
> ...I estimate that with the a generous tail wind and the gear config of the original post, that a glide of 3:1 ...
Yes, it can happen. Consider that when I got "my" average on my Fox of 2.2, I got "legs" of my flight path of 2.4-2.5 when I was flying downwind (moderate wind) and "legs" of 1.8-1.9 when I was flying upwind.
What I don't understand, though, is what you do with a glide ratio of 3 under a "generous tail wind"?!?!?!?
You cannot plan a flight path down to the landing given for granted a glide ratio of 3 under a generous tail wind" simply because you cannot have a guarantee that the wind remains "generous" and with no change in direction all the way from canopy opening to landing. What if the wind reduces its intensity (generally, it happens approaching ground) or if it changes its direction (and so it is not any more a "tail wind")? You cannot make it any more to the designated landing area?
I think that the usefullness of glide ratio of your canopy, that you would prefer to be as much "accurate" as possible, is to give you an idea if in a "no wind" condition, you can make it to the landing with a good safety margin, or not. Then, from there, you must keep into consideration that for any "quantity" of wind you must reconsider your "glide ratio under that wind" (to semplify: tail wind or front wind) and from there move on to consider another safety margin for your flight down to the landing.
Stay safe out there
Blue Skies and Soft Walls
BASE #689