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Dwain · September 25th, 2002

Adam.

I agree with nearly everything you are saying. Glide ratio is a highly variable and relative figure dependent on many many factors.

However if somebody is asking for a ballpark figure then I believe 2.5 – 2.6 is probably somewhere close to the maximum (not average) achievable glide ratio given average wing loadings, near sea level air density and nil-wind conditions for both Vtec FOX’s and Mojo’s.

However I do disagree with this statement:

>PC drag is a factor but bridle attachment style
>is probably negligable. The principal influence
>of a PC is related to form drag not compramises
>in wing shaping.

In extreme circumstances pc drag will make a noticeable change in wing shaping which in turn will affect glide ratio.
For example when I jump a Mojo220 with a 52”zp pilot chute, in full flight the drag of the p/c will deform the wing so much that the leading edge of the canopy will have a very noticeable V-shape due to the center cell being pulled back by the p/c. If fact the nose of the center cell will become reduced in width and can become almost pinched off, especially during hard turns. I have video evidence of this occurring on numerous jumps.
Glide ratio will significantly decrease as a result of this configuration due to the change in wing shaping. The canopy will still flare and land well, but glide performance is noticeably poorer compared with using a smaller p/c on the same canopy.
(Note: a 46" zp p/c does not create nearly as much visible wing deformation on a Mojo220 as a 52" zp p/c does).

In comparison a multi equipped canopy (such as a FOX225) will not suffer as much noticeable wing deformation when dragging a 52”zp p/c. The drag of the p/c remains the same but the wing deformation is less. This is because the load is spilt between cells 3 and 5. There is still a reduction in glide performance due to wing deformation, but not as much as with a canopy with a single bridle attachment point.

Although a 52” zp p/c is an extreme example, my point is that PC drag can change the wing shape, which can in turn severely effect the glide ratio of the canopy. I believe this was one of the main reasons for the invention of collapsible pilot chutes in the skydiving environments.

September 25th, 2002	#5 (permalink)
Dwain BASE Forum Guru Join Date: Dec 1969 Location: . Posts: 116 Rating: 0% (0)	RE: Glide Ratio Adam. I agree with nearly everything you are saying. Glide ratio is a highly variable and relative figure dependent on many many factors. However if somebody is asking for a ballpark figure then I believe 2.5 – 2.6 is probably somewhere close to the maximum (not average) achievable glide ratio given average wing loadings, near sea level air density and nil-wind conditions for both Vtec FOX’s and Mojo’s. However I do disagree with this statement: >PC drag is a factor but bridle attachment style >is probably negligable. The principal influence >of a PC is related to form drag not compramises >in wing shaping. In extreme circumstances pc drag will make a noticeable change in wing shaping which in turn will affect glide ratio. For example when I jump a Mojo220 with a 52”zp pilot chute, in full flight the drag of the p/c will deform the wing so much that the leading edge of the canopy will have a very noticeable V-shape due to the center cell being pulled back by the p/c. If fact the nose of the center cell will become reduced in width and can become almost pinched off, especially during hard turns. I have video evidence of this occurring on numerous jumps. Glide ratio will significantly decrease as a result of this configuration due to the change in wing shaping. The canopy will still flare and land well, but glide performance is noticeably poorer compared with using a smaller p/c on the same canopy. (Note: a 46" zp p/c does not create nearly as much visible wing deformation on a Mojo220 as a 52" zp p/c does). In comparison a multi equipped canopy (such as a FOX225) will not suffer as much noticeable wing deformation when dragging a 52”zp p/c. The drag of the p/c remains the same but the wing deformation is less. This is because the load is spilt between cells 3 and 5. There is still a reduction in glide performance due to wing deformation, but not as much as with a canopy with a single bridle attachment point. Although a 52” zp p/c is an extreme example, my point is that PC drag can change the wing shape, which can in turn severely effect the glide ratio of the canopy. I believe this was one of the main reasons for the invention of collapsible pilot chutes in the skydiving environments.