0
BrianSGermain

Canopy Downsizing Chart by Brian Germain

Recommended Posts

Many folks believe that we need better guidelines for canopy downsizing. I have spent a great deal of time putting together a chart for exactly that purpose, along with 21 pages of ideas that make sense of the chart.

Here is the link:

http://www.bigairsportz.com/pdf/bas-sizingchart.pdf
Instructional Videos:www.AdventureWisdom.com
Keynote Speaking:www.TranscendingFEAR.com
Canopies and Courses:www.BIGAIRSPORTZ.com

Share this post


Link to post
Share on other sites
If you look at the numbers carefully, you will see that the wingloading recommendations are not linear. Smaller canopies match you with a somewhat lighter loading, while big ones suggest a heavier load, to reflect the non-linear nature of scale effects.
Instructional Videos:www.AdventureWisdom.com
Keynote Speaking:www.TranscendingFEAR.com
Canopies and Courses:www.BIGAIRSPORTZ.com

Share this post


Link to post
Share on other sites
Sweet!! According to the chart at exit wt 235 (don't laugh) and 500+ jumps, I should be jumping between a 150 and 139.

Kidding aside, I'm very happy with my 190 and have no plans to downsize anytime soon. However, much thanks Brian for putting that together. That should help a lot in helping the young (and stupid) from jumping a canopy that's too small for them.

Butthead: Whoa! Burritos for breakfast!
Beavis: Yeah! Yeah! Cool!
bellyflier on the dz.com hybrid record jump

Share this post


Link to post
Share on other sites
I think you misunderstand the chart. The chart is describing the MINIMUM canopy size.

Note the following direct quote from the chart:

*Jumpers are welcome to use a larger parachute than the chart suggests.
The choices we make have consequences, for us & for others!

Share this post


Link to post
Share on other sites
I just tried to stall my 168 Pilot loaded at 1.17. I pulled the brakes all the way down and held it for good 10s. It did not collapse or anything like that. It was square, stable and slow. I already shortened the brakes cause it had no flare. Is it normal? Are the brakes still too long?

Share this post


Link to post
Share on other sites
Quote

I pulled the brakes all the way down and held it for good 10s. It did not collapse or anything like that. It was square, stable and slow. I already shortened the brakes cause it had no flare. Is it normal? Are the brakes still too long?


What is the connection? How would anyone able to tell if they are long or not from this info you provided?

Share this post


Link to post
Share on other sites
Canopies over 150 square feet often run into this conundrum. Either you can stall it or you can front riser it, but not both. It is generally less costly to be unable to stall a large wing, since the slow flight prior to the stall is sufficiently slow to allow for good landings. If you tighten the brakes too much in order to reach the stall, you will sacriice the ability to front riser effectively and may be in brakes when you arms are all the way up. It is possible that the optimum configuration for this canopy is right where you are, or even slightly
longer.
Instructional Videos:www.AdventureWisdom.com
Keynote Speaking:www.TranscendingFEAR.com
Canopies and Courses:www.BIGAIRSPORTZ.com

Share this post


Link to post
Share on other sites
My Pilot 188 was the same way. I had to take a wrap to stall it out on toggles. Like Brian said, the stall speed on those bigger canopies is low enough that the speed you can slow down to with the toggle stroke is more than enough to flare correctly.
"Are you coming to the party?
Oh I'm coming, but I won't be there!"
Flying Hellfish #828
Dudist #52

Share this post


Link to post
Share on other sites
Nicely presented.

I just had a very heads-up newer jumper ask me to explain to his 150 jump, 88lb girlfriend that she would be fine jumping a Nitro 108 because her geared up wingloading was only .98 to 1. He was surprised when I told him absolutely not. He was operating on the limited information that is readily available that wingloading is the most important (or only) consideration. We are failing new jumpers by giving them incomplete information.

The "Non-linear Nature of Parachute Performance" should be required reading for every new jumper and anyone who advises jumpers on the canopy they should fly.

Share this post


Link to post
Share on other sites
BG,
I have 125 jumps and fly a Heatwave 190 loaded at 1.4. I have been working on 90 degree landings and carving. I have read your book, down sizing chart, and Novack's checklist. I am wondering at what point can a jumper disregard the jump numbers for down sizing and use the ability of the pilot. I would like to get a recomendation from you for a canopy coach in the midwest " Oklahoma Area" that could evaluate me on my ability and not the jump numbers. I would like someones honest opinion weather I could be safe on a smaller canopy.

Also, I was reading about the non-linear nature of scale effect. Your book says that aerodynamics don't scale, and I can't understand why they wouldn't. Having taught aerodynamics for airplanes and helicopters I thought I knew this subject pretty well. Airplane manufactures in the past used scale models to determine stall speeds, stability characteristics, and drag ratios prior to ever building a prototype. If it works on a rigid airfoil how does that differfrom a nonrigid canopy? Are there any theoretical differences between a canoy and an airplane wing?

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

0