Canopy speed

[guest]

Hey out there. I have another question for the minds of BLiNC! I'm jumping a Fox 225 that is ideally wingloaded. What is the difference in my canopy's airspeed, when in deep brakes (factory setting) as opposed to shallow brakes? I can estimate, but what are the actual numbers? Also, how much do pilot chute sizes affect this? Will a 42"PC steepen my glide dramatically when compared to, say, a 36".
What about no PC static jumps? I don't do them ,I'd leave the PC on anyhow. Will I need to alter my approach to reach the same landing area, due to a flatter glide? I'm used to flying my canopy with a 42" and I'm just curious about what to expect when I change something. Are there other equipment configuration aspects that will affect air speed? Thanx---Dex

[guest]

Does your FOX have a multi?

[guest]

No multi...

[guest]

Here are my thoughts. I only have around 80 jumps with a 48" PC, each with minimal canopy time, and about 15 with no PC (direct bag). So, my experience base isn't very large (i.e. I'm not an expert here--or anywhere else, for that matter).

The only times I've really noticed a difference in canopy flight is with a huge PC (46 or 48) compared to no PC (direct bag). I can't really tell the difference between PC's (even a 32 to a 48 all seems the same to me).

In my opinion, a canopy with no PC glides a tiny bit flatter, and flares better than a canopy with a huge PC. This effect is far less noticeable on canopies equipped with a multi bridle attachment. I theorize that this is because the difference in flight profile results from deformation of the wing's top surface, rather than from the drag of the PC. A multi spreads the drag out more, resulting in less noticeable deformation.

So, to answer your original question, you may notice some minor differences in flight with no PC (slightly flatter glide, slightly stronger flare). However, the differences are, in my opinion, really minimal enough that they will make little or no difference to the jump itself.

I hope I've helped.

--Tom Aiello
tbaiello@ucdavis.edu

[guest]

If the canopy deploys in deep brakes, what is the air speed? How much faster if I'm using a shallow brake setting? (refering to factory settings)

Basically, if I jump a cliff with a slight headwind, my airspeed on deployment needs to exceed the headwind to avoid a strike....right?

Would it be advisable to use shallow brakes to counter the headwind?

If I use a shallow brake setting to avoid a cliff strike, will I need to go straight to toggles in the event of an off heading opening since my airspeed combined with the wind will take me into the wall faster?

My logic is with the faster airspeed resulting from the shallow brakes, a toggle turn will get me on heading faster.

Am I off on this one?? Oh yeah, don't tell me not to jump the cliff, these are hypothetical questions only. Thankx---Dex

[guest]

Deep brakes prevent you from hitting the wall due to opening surge following an off-heading. You will want to use these. In my mind, there is no such thing as a "headwind" in this situation. The wind is going to have to turn parallel to the wall at some point. It can't go through it. And if you're jumping close to a wall in wind conditions that would have you backing up in deep brakes, then you are not very bright.

[guest]

So you can honestly tell me you've never jumped when the winds weren't "just right"? I'm trying to gain a better understanding of canopy physics, because there's only so much you can learn under a canopy. There is a difference between knowing HOW and knowing WHY.

I understand if the wind is greater than your airspeed (on a cliff) it is a no jump situation. So how much wind is too much? Say I have an anemometer and I can accurately measure windspeed. If I already know the airspeed of my canopy in different configurations, I can better judge what constitutes an unsafe wind condition.

Knowing this information can be applied to all aspects of BASE, when it comes to avoiding object strikes.

Any positive input would be appreciated.---Dex

[guest]

If you have access to such an anemometer, then I would recommend putting it in your fanny pack, jumping your canopy out of an aircraft, and then holding the anemometer out to your side in flight. You have just measured your airspeed. Empirical data is going to give you your only accurate estimates given your specific combination of variables (wing loading, brake setting, etc.)

[crwper]

As I see it, your biggest wind-related hazard on a cliff is turbulence or rollers, not being pushed back into the cliff. According to BR, my canopy should have about 15 mph forward speed. On a 300-500 ft cliff, I would prefer to have as high as 3 mph wind from my back. My understanding has been that in this situation the rollers will stay toward the top of the cliff, and by taking a short delay you can get under them. Higher winds means deeper rollers. With a wind from the front, I think even very small winds will generate turbulence on the whole length of the cliff face. I'm not so concerned about getting penetration into the wind, as I might be on an antenna or bridge, but I am concerned that turbulence will have a very strong effect on my heading.

Michael

[guest]

Is there a good website where I can learn about how air behaves around various objects?---Dex