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If you were to lay out a Rock Dragon 303, nice and flat, on the ground...
and then:
lay a Troll 285 nice and flat on top of it...

would they REALLY be the same size? (Give or take 2 sq. ft?)

I can say for certain that my Troll 290 and Tom Manship's Blackjack 310 were within 2 inches in both dimensions.

I can try to lay out my Dagger 313 and Troll 290 and check them against each other, too, if you want, but I don't have a Rock Dragon to check against.

I wonder how the air gap compares between top skin and bottom skin on those. Depth I guess.

Do you know the PIA standard for sq footage? First measure 6" aft of the leading edge, spanwise. Next lay the canopy on it's side and measure from the upper edge of the load rib to the tail in a straight line, multiply the two. It's a flat dimension and a way to get accurate measurements. Some manufacurers measure a "Projected inflated size" and it is just that, projected. So the 310 and 290 might be really close.

I have found that very few manufacturers actually use the same measuring method, even if they actually all claim to be using PIA spec.

I tend to treat square footage measurements on canopies as "model names" rather than as "size measurements." The same can be said of pilot chute size measurements. One manufacturers "42" is not necessarily the same as another manufacturers "42."

Funny you should mention that. Hookit took some interesting measurements a few days ago...

I have a 46 inch and a 48 inch pilot chute.

My 46 is really 46 inches in diameter measured across all load tapes. The 48, ranges from 45 1/2 inches to 46 1/4 inches in diameter depending on the load tapes being used.

Needless to say, it's not a 48.

It's really in the interest of apple to apple comparison, say if the "Whizzbang 260" flys just as well as "Whooo-Hooo 287.5" and nobody measures them the same.Who is to say if the "Whizzbang" company did a total ripoff on the "Whooo-Hooo" design. Then they call it a 260 and say "Ours superior to the "Whooo-Hooo" in performance with a "smaller wing" Just something to chew on at dinner.....

Tom, that's not necessary, but thank you!
You answered my question with the Black Jack / Troll comparison.
Thanks.

A few months back I was buying a new reserve and was debating on what size to get...after some discussions with my rigging mentor and the PD rep. I learned that their 143R is really more like 150 square feet.

I thought this was odd, but later heard about the difficulties in accurately measuring 3-D objects that are only full size when inflated, how many people with limited experience buy canopies by the model numbers, and how some numb-nut skydivers always think smaller is better.

I'll get you a comparison between a RD 303 and a Troll 305 as soon as the little sucker finally arrives.