Round parachute, apex vent size?

[Mr.Burns 0]

What size are the apex vents on typical round parachutes? If anyone knows any specifications for a t10 or a PC or anything at all, for any size parachutes, please respond. Thx.

[Cloggy 1]

Apex vent size on SF-10a is 15" diameter.

On the PC the opening in the apex is approx. 15". I guess the effective opening is a bit smaller in flight, as the apex lines are pulled down in a cone shape.

[councilman24 36]

Cloggy

On the PC the opening in the apex is approx. 15". I guess the effective opening is a bit smaller in flight, as the apex lines are pulled down in a cone shape.

You say this about a PC, I've got three hundred jumps on a PC and two downstairs and I guess I never paid much attention to the actual apex. Just crown lines and packing the silly things. That was before I cared.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[Cloggy 1]

I never cared either, Mr Burns' question triggered my curiosity and the PC was unpacked.
I'm wondering if the apex hole on the PC was meant as a vent, or if it's just there to make construction easier/better (Otherwise you'd have a lot of tapes, fabric, lines and sewing meeting in a very small area). It's not that the PC is lacking holes

[Bob_Church 7]

Mr.Burns

What size are the apex vents on typical round parachutes? If anyone knows any specifications for a t10 or a PC or anything at all, for any size parachutes, please respond. Thx.

I sent a copy of your request to a friend who knows rounds. I mean KNOWS them, and hopefully this will help. Also, if you end up needing to know a detail about any particular canopy let me know and I'll run it by him.

"There's no rule of thumb for how large the apex vent is in a round parachute because of many factors. But. primarily, the porosity of the fabric and the geometric porosity of the canopy are the big drivers for determining how much venting there should be for the particular type of inflation that is desired. Some round parachutes have no apex vent. Many have an apex vent only because it's a very difficult task to completely close the apex. A ParaCommander is an example of a parachute where the central vent served no useful purpose except to make fabrication easier.

If you ever saw the NOVA channel program about the parachute system for the Mars rover "Curiosity", you would have seen me come in to help them when they had an inflation problem in the NASA wind tunnel. It appeared to me that the apex was initially venting too much air so I installed a textile "washer" in the vent area and all was good after that. Of course, the parachute that went to Mars had no washer but it did have a vent that matched the size of the hole through my washer.

I just measured a T-10 vent and it's about 19.6" in diameter. "