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mac_la

Weight Loss + Jumping (Landing) at Altitude

Question

Hi,

 

Novice “A” licensed jumper here with 38 jumps. Learned to jump at Spaceland, now living in Colorado. I have two questions:

1) I just lost almost 90 lbs. I was a fat fuck. Down from 265 to 180, 5’9”. As such, what are your thoughts on proper canopy size now? I have NO clue what jumping will now be like with this weight loss. I was jumping a 280 and 300. Accounting for wing loading and being a novice jumper, I’m guessing around 200-220? That would put my wingloading at 1.22 on the high end. But, do you think otherwise? Very open to advice and discussion.

2) Landing at altitude: I’ve made a few jumps at altitude so far, but drastically fucked up my landing each jump (broken tailbone, herniated discs). Can you please help me problem-solve this issue? I can’t keep fucking these landings up and it’s very, very frustrating. During AFF STP and fun jumping at sea level, I almost always nailed my landings (even at 265 lbs). But, I cannot figure out what I am doing so wrong here in Colorado. It’d maddening.

 

I greatly appreciate your time and thoughts. And, please, take it easy on me - I’m still new and I know it. 

 

- Mac

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1) At my home club, a wingloading of 1.22 would be considered too high for a 38-jump A-licensed student. Conventional wisdom calls for a wingloading around 1.0. But if you are 82kg now, and add ~15kg for equipment, your exit weight would be around 95-100kg. Round up to 100kg, and you would need a 220sqft canopy to hit 1.0 wingloading.

2) Breaking stuff on every landing is indeed unsustainable. High altitude is typically equated to an effective smaller canopy size. So you will likely need to jump a bigger canopy. But you also need to be able to roll out a landing. Practice it lots on the ground, and upsize further if needed. Upsizing is underrated.

My advice: find a colorado-local skydiving club, and talk with their instructors. Let them know your history and experience (bring your logbooks) and listen to their advice regarding canopy and training. They should know how to handle students jumping in higher altitudes, and they should have the correct student gear available for rent.

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Newbie here as well. Might be a stupid question to some but can someone explain how landing at sea level and altitude are different ?

 

Congrats on the weight loss Mac_la

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1 hour ago, IJskonijn said:

Easy, it all has to do with air density. At high altitude, the air is less dense. This means that your canopy (all else kept equal) will have lower air resistance at the same speed. Thus, for steady flight in less dense air the canopy ends up going faster. Both faster forward, and faster downwards. Both of these is also something a smaller canopy will do relative to a larger canopy (at same exit weight). To counter this behaviour, the best way is to increase canopy size.

Right on, that makes sense.

Thank you for the explanation.

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Easy, it all has to do with air density. At high altitude, the air is less dense. This means that your canopy (all else kept equal) will have lower air resistance at the same speed. Thus, for steady flight in less dense air the canopy ends up going faster. Both faster forward, and faster downwards. Both of these is also something a smaller canopy will do relative to a larger canopy (at same exit weight). To counter this behaviour, the best way is to increase canopy size.

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You're doing the WL division the wrong way around. It's your 220lbs weight against the 280 lbs canopy, not the other way around, so your WL is roughly 0.78 now and well within limits.

I'm about 195lbs myself (5'10") and currently jumping a 210 sqft at 57 jumps and a canopy course. I can say that the Belgian canopy restrictions allow for pretty fast downsizing when compared to many other countries or for example Brian Germain's downsizing list:

based on his list you'd be ok jumping a 230 sqft, not downsizing before #100. However given that you're jumping at altitude, upsizing is probably a good idea.

On the other hand I find it strange that you're having such problems landing on a large canopy like that, even at altitude I wouldn't expect much problems landing calmly & controlled (even if falling over or sliding on your butt) under a 300sqft. What exactly is happening on your landings?

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On 3/24/2019 at 4:28 PM, mac_la said:

 

2) Landing at altitude: I’ve made a few jumps at altitude so far, but drastically fucked up my landing each jump (broken tailbone, herniated discs). Can you please help me problem-solve this issue? I can’t keep fucking these landings up and it’s very, very frustrating. During AFF STP and fun jumping at sea level, I almost always nailed my landings (even at 265 lbs). But, I cannot figure out what I am doing so wrong here in Colorado. It’d maddening.

 

You need a canopy course.  they film the landings and can help you correct things.  That way they can correct if you look down to much, flare to early or late or whatever it is.  Also, its not pretty but remember to plf.  At least if you are ready to plf you can turn that into a stand up landing.

I know you are low jumps but learning to fly the canopy in a variety of situations like high elevation and high temperatures is a valuable tool in the tool box.  I don't jump at colorado high but at 1500 ft and desert temps I can feel a big difference in how the canopy handles versus a DZ an hour away at the coast.  You will get it but seek out some local help so you don't break anything else!

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