The concepts applied to accomplish a stable flying position for recreational skydiving are well established as they are applied to student training from the very begining. Most everyone starts with the arching technique to accomplish stable belly-flying. The principles are well formed and involve establishing a low center of gravity(CG) and raising the extremities of the body to a level above the center and maintaining symmetry amoung those extremities. This principle should not be forgotten as you begin to learn or experiment with other flying positions.
Applying this basic concept to sit flying runs into a snag which the V-sit position resolves. The wide stance of the legs used in the advanced sit-flying position is a partial violation of symmetry and low CG considerations and will cost you jumps trying to get a handle on the aerdynamics of the many body parts which are now in a position of advantage over your moderately high CG above those a-symmetrical extremities, potentially a big problem. Solution,,,, restore aerodynamic symmetry and an artificial CG for the legs alone. Result,,, gradual familiarization to the balance issues of a head-high/mass-high flying position.
"V-sit" involves taking your feet out of one position of dominance in the aerodynamics equation and re-assigning them as wedges to cut through the air ahead of your middle and upper legs. Picture a "V" shape made with your knees and feet. Knees spread wide and feet held together at their inside edges, heals or, in the extreme bottoms, in firm contact and kept together, or somewhere there abouts. Upper legs and torso form 'somewhat' of a right-angle ('L') as does your upper legs in reference to your lower legs(when viewed from the side). With the feet together you are presenting a larger drag component with the lower leg so keep this in mind in your selection of pants or leg-wear. As you advance into the standard sit-flying position this element will change. To furhter enhance your advantage over the moderately light leg areas and their substantial drag component, the slicing of the air with your feet and lower legs in 'V' arrangement can be aided with enhanced drag established at upper body surfaces. At this point, of learning a head-high flying position, a floppy longsleve shirt is likely to give you an advantage well worth the discomfort during those hot days on the ground.
More to follow in the days ahead, as well as some background which brought me to apply this technique in my own struggles with sit flying. With a limited capability to rack up massive jump numbers and the desire to learn an emerging flying style this adapted technique gave me a boost toward rapid success and fun, without needing an arch.
From your hips up you are establishing another area of drag and weight arrangement, so rather than the single center of gravity of the belly fly position, you now have two seperate parts of your body to manage and balance the drag/weight component. The upper body arrangement is like the advanced sit position's arrangement and is pretty straight forward, remembering to keep your upper torso over your hips will get you started and using your arms and hands to push forward on the air will help you stay upright. Since your legs are controlling themselves and slicing through the air you can adjust fallrate by driving them down into a steeper "V", or drawing them up to a flatter knees wider arrangement. You are balancing in a very dynamic position and the authority of your arms plays an important roll. Keeping your feet, knees, hips, shoulders, head and arms symmetrically arranged will have favorable results and from there you can go dynamic on any axis by getting out of symmetry and then begin to develop the stopping awareness to the starting position. Movements are partly aerodynamic and partly gymnastic. Your stopping mechanism is timing, balance and drag management. Your feet can be drawn back under your body as necessary as you push with your arms extended aft to get you back on top of the centerpoints or wedges, your feet and fanny.
This position may help you move faster into the more advanced position of a wide stance with feet and knees. "V" Sit is primarily for falling straight down and learnng to balance yourself in a head-up position. This is as far as i've gone toward sit flying but i'm have lots of fun with "V"sit.
Have fun and remember to allow ample time to slow down before your deployment altitude.
Write with your questions or comments.
Remember the basics of stability and progress in stages, get the most out of your AndrewJ.