Canopy forward speed

[vpegyed 0]

I didn't know if this should go into this forum or under the canopy piloting section, sorry.

I've just gotten to the point where I'm going to be off rental gear and jumping my own gear and staying current making 10-20 jumps a month now that time and money allows for it. I've been jumping sabre 2 230's for my last 30 or so jumps, and the parachute in my container is a PD-230 (0-3cfm fabric) with less than 100 jumps on it. My question pertains to the canopy's penetration into the wind loaded at about .95:1. What would be the forward speed of this canopy at this wing loading. I've searched trying to find a real answer but just a bunch od ambiguity.

The main reason I ask has to do with the upper reaches of the wind limits. Anything more than 18 I felt a little uncomfortable in my rented sabre 2, just because a gust could easily have me flying backwards.

I know it doesn't mean much, but I've stood up and felt totally in control of my canopy for landing on nearly every skydive I've made. I "feel" the lift generated by my canopy during a flare and love flying my canopy more than freefall. I always do practice flares before entering the pattern.

[Nigel 0]

I think your post has the data to answer the question:

If heading into 18mph wind, and slight gusts will push you back, then 18 mph is close to your top forward speed (depends, of course, how 'slight' is defined. 2-5 mph would be my 'slight, which would make your max speed 18-23 mph)

I 'calibrated' my canopy (Stiletto 120, loaded at about 1.7 lb/sf) forward speed empirically by slowly increasing the upper windspeed at which I'd still jump without going backwards with no brakes. It's between 25 and 28 mph. So without knowing how to calculate drive speed formally, your 18ish mph estimate sounds right.

The factors I can see affecting this would be condition of the canopy, composition (spectra, vectran or HDMI etc) lines and trim, plus changes in your weight. Also altitude of DZ above sea level and air temperature.

I have 3 Stiletto 120's. One has > 1000 jumps, the other 2 are both new, have < 100 jumps each. With steady 30mph winds, I'll happily jump one of the either newer Stiletto. For the old Stiletto, I don't go beyond 25 mph.
Maybe a canopy designer can chime in here...?

That you're standing up your landings is great. But 30ish jumps over 2 years would, I think, raise questions of currency at most DZs. I would aim to do 50 hop and pops in quick succession, in varying conditions, on your current 220 (or maybe with a 210, but nothing smaller)

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[potatoman 0]

You won't find the answer, since there are tooo many factor to calculate. take the winds as they come, find where you are happy and not happy, and go with that, or what the SO says.

Things you need to consider:
Your body size, and shape - how you hold your legs.
How loose your chest strap is has effect on wing
Slider stowed, open..
Pilot chute size, collapsed, lentgh of bridal.
AIR temperature. Hot days are faster.
AIR density, from 1 dz to another.

And remember that the airspeed of wind changes with elevation above ground. so what is 18 on the ground might be 5 or 30 up there.

Closest you will get to finding out, do what you normally do with your gear and legs etc. Jump early morning when there is absolutely no wind, and get a buddy on the ground with one of those police shooters things.

You have the right to your opinion, and I have the right to tell you how Fu***** stupid it is.
Davelepka - "This isn't an x-box, or a Chevy truck forum"
Whatever you do, don't listen to ChrisD.

[shropshire 0]

potatoman

Closest you will get to finding out, do what you normally do with your gear and legs etc. Jump early morning when there is absolutely no wind, and get a buddy on the ground with one of those police shooters things.

Or use a GPS ... fly Full drive.. into wind (look at wind sock!) and fly down wind... This will give your your GROUND SPEED .... simple maths will then give your Approximate AIRSPEED ...... then map you course when you get back to your P.C

(.)Y(.)
Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome

[potatoman 0]

mmm, yeah. I also seen software for smartphones, that the Hang gliders use. GPS plus the accelrometer etc.....Works a charm.

You have the right to your opinion, and I have the right to tell you how Fu***** stupid it is.
Davelepka - "This isn't an x-box, or a Chevy truck forum"
Whatever you do, don't listen to ChrisD.

[pchapman 262]

Although you can collect all the data you want, nobody decides whether they want to jump by punching in numbers on a computer and doing a calculation based on their canopy, air density, how much you ate for breakfast, etc.

You decide to jump based more on empirical factors. What are other jumpers doing? Are they reporting turbulence or gusts? Is the windsock showing gusts? Are the uppers a lot stronger than usual? And finally, you'll look at wind meter or forecast or windsock (or whatever best info you have) and compare that to conditions you jumped in before, and decide whether you are comfortable in those conditions.

So you don't take "18 mph" on a wind meter and plug that into a computer. You ask yourself if the last time you jumped when "18" was showing, you were comfortable or not.

There's nothing wrong with going backwards under canopy up at altitude. It does make navigation harder but in itself that isn't a problem.

Going backwards on final approach is a little uncomfortable, but often with a bit of such backwards movement, you'll still end up coming down no worse than vertically just at touchdown, where the winds have continued to decrease close to the surface. Actually going backwards on touchdown gets a little rough though, making it tough for anyone other than a PLF expert from round canopy days.

Turbulence also has to be considered, as that can completely change whether a given wind speed in a given location on a given day is comfortable or safe or not.

Looks like you are already getting a feel for what is comfortable or not with the canopy you fly. A tricky part is then to decide whether to keep that limit or learn to go to higher limits. Other jumpers watching your flight would be able to help there.

On the one hand you don't want to get into situations that are too scary, on the other hand you can learn to expand the range of situations you are comfortable with.

I've jumped big accuracy canopies at .65 loading in high winds where I was going backwards until the last 10 feet of descent, or even very slightly backwards to touchdown. No big deal if you fly right. But if I were jumping a faster, smaller parachute, I probably would not want to be in wind fast enough to give me no forward speed on final approach. If I were under a canopy with a 35 mph forward speed, at a lot of DZ's, if the wind were that strong, there would also be nasty turbulence in which I absolutely wouldn't want to jump.

Although turbulence (& gusts) and wind speed are somewhat correlated, in the end, it tends to be turbulence (& gusts) more than average wind speed that determine whether conditions are jumpable.

[vpegyed 0]

Thanks for the help, you guys confirmed everything that I was thinking. I just didn't know if the difference in fabric would make a significant difference in the speed.