In reply to:
Regarding 52" p/c's:
There are six main phases in deployments (note: some of these phases overlap in sequence):
Phase 1: Pilot Chute (p/c) is released (via BOC or hand held)
Phase 2: p/c reaches bridle stretch
Phase 3: p/c inflates
Phase 4: p/c extracts canopy to line stretch (there are multiple sub-stages here such as container opening, extraction of canopy from container and lifting of the canopy to line stretch)
Phase 5: canopy achieves bottom skin inflation (there are multiple sub-stages here)
Phase 6: canopy achieves cell pressurization (there are multiple sub-stages here).
The 52" p/c in very low airspeeds will speed up Phase 4 slightly compared to a 48" p/c. However due to the extra weight of the p/c it can slow down Phase 2 slightly. Also due to the extra size of the p/c it can also slow down Phase 3 slightly. So basically a 52" p/c (compared to a 48") will generally make Phase 2 and 3 worse, but improve Phase 4.
The net result of a 52" p/c is still positive, but only small. From video analysis my conclusions were that a 52" p/c results on in a higher opening of maybe
about 10-15 feet on average. Still, if you are freefalling very low objects then this can make a big difference.
I don't really care if I have a 48" p/c or a 52" p/c until my exit height gets below 170 feet. However this is with canopies around the 220 - 245 square foot / weight range. For the bigger canopies (293) I would probably recommend using a 52" p/c for anything under 190' to be safe (I'm just guessing here).
The construction of the 52" p/c is very important. Weight is a critical factor that will slow Phase 2, and to some extent, Phase 3. My 52" p/c does not have any load tapes on the ZP material (as they aren't needed for re-enforcement as the p/c is only used in low airspeeds). Load tapes on the mesh are very important as they limit the mesh from stretching and therefore air from spilling out around the skirt. I have 8 load tapes on the mesh of my 52" p/c (same as the BR 48") and I think it is a good balance of weight versus the amount that the mesh can stretch.
The technique you use for freefalling very low objects is the most critical. It takes almost the same amount of time from Phase 1 to Phase 3 to occur as it does for Phase 4 to occur (about 1.3 seconds on average for Phase1-3 and about 1.5 seconds on average for Phase 4, but this varies hugely from jump to jump). Using a 52" p/c will speed up Phase 4 slightly, but the biggest difference you can make is on Phase 2. If you just throw the p/c to the side it will go into freefall with you. You will then need to fall faster than the p/c to overtake it before it will reach bridle stretch. The p/c won't fully inflate until after it reaches bridle stretch and is being dragged through the air by your body. However if you throw the p/c up when you exit it will reach bridle stretch quicker and the p/c will begin to inflate sooner. The sooner after the exit the p/c becomes inflated and starts doing its job, the better. Your acceleration is exponential, so something done up front which will shave a fraction of a second off the end, will make a big difference. If you throw a 46" p/c up to bridle stretch on exit you will open much higher than if you throw a 52" p/c to the side. The best technique is similar to throwing a basketball through the hoop. You jump up in the air and you throw the basketball(p/c) upwards and forward when you are at the top of your jump. In a perfect ultra-low freefall the p/c should inflate above the exit point and already be starting to pull on the shrivel flap (or pop a pin) when it becomes level with the exit point. In a way it is cheating as you are getting part of the deployment to occur above the exit point. There are other techniques as well that help, such as the forward push on your launch, your body position in freefall (to minimize swing through on line stetch), and the way you release your brakes, but I won't go into them here.
In summary, the 52" p/c will help a little but technique will make a bigger difference. I suspect a 52" p/c may make a more noticeable difference on heavier canopies (eg. Flik293). For you to notice the difference of a 52" p/c over a 48" p/c you will have to be really pushing the envelope of low freefalls. 99.9% of BASE jumpers won't freefall something low enough to need a 52" p/c which is why BR doesn't make them as standard.
Also the glide of the canopy will suffer with a 52" p/c (more of a difference on smaller canopies) so they can cause more problems then good depending on the jump.
If you are planning to freefall some very low stuff then I'd recommend getting a 52" "Big Bertha" from BR.
Also keep in mind that the opening height variability of low freefalls is huge – even when everything else is the same (packjob, p/c, canopy, technique, etc etc). Sometimes you open super high and sometimes you open in the dirt. I've done 13 freefalls from 156' over hard earth and this height does have a small margin for error. On the best freefall from this object I had enough height to pop my brakes and make a 90 degree turn before doing a nice soft flare. On my worst freefall I opened and then hit the ground straight away. Gear and technique remained constant but the opening height varies wildly (I also have about 80 freefalls from under 185 feet with the same results of wild variation in opening height). My point is to not draw any conclusions after just a few jumps. Hesitations eventually will occur during some phase of the deployment sequence so make sure you have some margin for error built in.
Hope this helps,
Dwain
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