Hmmm, I thought the opposite was true. But maybe I am misunderstanding your statement. Definitely takes more material to MAKE a spherical chute, and you have to cut the gores (segments) individually and so a certain amount of material is discarded.
from Richard Nakka (I don’t know him but for what I have heard about him he’s kind of a legend in Rocketry)
https://www.nakka-rocketry.net/paracon.html
The design that is presented here is of a true
parachute, having a "shaped" canopy, as opposed to what is referred to as a
parasheet. A parasheet has a canopy that is flat when not inflated, and may be cut from a single piece of fabric. When a parasheet inflates, the canopy material is "gathered" by the shroud lines, forming an approximately hemispherical shape. A parachute with a
shaped canopy is more efficient than a parasheet, since less fabric is required to produce the inflated shape.
also from.
Randy Culp (Tripoli #6926)
http://www.rocketmime.com/rockets/descent.html
- Cd is the drag coefficient of the chute, which is 0.75 for a parasheet (flat sheet used for a parachute, like Estes rockets), or 1.5 for a parachute (true dome-shaped chute).
rest of this is my own understanding.
downside of hemispherical chutes is they are more difficult to make than parasheets. For low power, parasheets are quite adequate. The more corners the more efficient, but the difference between 6 and 8 is not much. I just find using the fold and cut method for 8 sides easier than 6, and adding 2 more shroud lines isn’t much extra work but provides roughly 33% lower load per shroud line, which Can’t hurt.
I am curious if anyone knows the history of why a six sided chute became the standard For kits. I am guessing because it looks and works better than 4, and it uses fewer shroud lines than 8 and that cuts down cost, maybe
@hcmbanjo or
@jadebox can chime in here.