US Hawks Hang Gliding Association

Stuffings for DS Hang Glider Sails
This topic is meant to explore the arts, science, technology, and results of stuffing DS hang glider sails to affect the aerodynamics of the gliding HG.
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We know hang gliders with ribs between an upper and lower sail, thus DS. DS may be 100% of chord or 50% of chord or other % of chord. In the DS portion of a HG sail things might be "stuffed" into the interior between the upper and lower sail. Ribs that are hard connected to spars may not qualify as a stuffing. But a loose rib just might be stuffed into the cavity between the upper and lower sail. Many of us stuff battens and rib-battens into pockets sewn to the sail; so that might quality as a stuffing to a SS or DS sail; the arts of that kind of stuffing is invited in this topic. But feel free to advance pockets for stuffing as well as o ther means of stuffing. What forms and what materials? What artsy tactics? What benefits of doing something this way or that way? Targets and objectives?

Is one after low mass HGs while having still having approximations to special airfoils? What might be the refined purposes of having stuffings inside the wing? How might the position of a stuffing be stabilized? How much trouble or todo is there in having a certain stuffing system? What happens to performance of the HG with this or that stuffing? How might stuffings be used for active control of a HG? Can a stuffing be varied during flight? How will the stuffing affect changes in the various aerodynamic centers of the HG? Design, shape, weight, anchors, positioners, durability, etc. of stuffings? Reports of use of certain stuffing systems?

Teasing non-exhaustive stuffings for DS sails in a HG listed for possible study and development:
robust ribs
balloons
cheering sticks inflated
airbeams
compressible foam forms
CFRP veneer patches
Mylar segments
rods and tubes
LED strips on low-mass stick held up by line drops from rigging lines to help form the camber of a chosen airfoil.
Faust Vee items for various purposes: control, airfoil shaping,
Folder paper forms
Food
Camping gear
Gliding-system gear
Tools for wing care and fliking cares (fly-hike)
air pump
balls
coms
signs
ID, money, medicine
sail-repair materials
line for HG and other activities
kites
last will
literature for others
pillows
space emergency blanket
batteries,cell or satellite phone, camera
fishing gear
privacy curtains

First note local on matter JoeF wrote:Pull flat with a string that attaches to aft edge of the flat while the front edge of the flat is stuffed beneath LE spar and DS sail sock. Have the pull line have a stopper. The pulling causes the flat item to curve up to press the upper sail to form a camber in the wing. Judicious design of the flat will bring about the height of the camber wanted. By adjusting the string, the camber may be adjust and the tautness of the sock sail will be altered. Such variation could be a variable geometry control device. But all could be the formation of camber and twist in the wing. For twist the sock and the flat may be designed to effect wing twist.

This is a posting of a rough note to be developed.
See note below about spar case. The flat item intended for camber forming would tuck in a reinforced tiny pocket at the LE spar case; there will be motion of the flat during flight and wing handling; such motion could wear the pocket; perhaps a soft tip to the flat could be mounted. The aft end of the flat would be pulled by a string; the string could be anchored to the lower sail on the sail's exterior. Changes in the pull could change the camber at a span station.
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Sock sail's three chambers

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To effect some wing stuffing for DS sock HGs, one may want the sock to be triple chambered in some cases: the global main sock chamber, a spar case chamber for LE spar to slip into, and a spar case chamber for the TE spar to slip into. Such sock of three chambers may be one way to control that the lower sail stays taut while the upper sail may be designed with various looseness;the two small cross sectioned chambers are sewn to the sock. The looseness allows stuffing the bird. Some stuffings may press on the lower sail and that pressing may be made less by the tautness of the lower sail. Such challenge pertains to the rough note quoted above in this post. That is, the flat used will be pressing on the lower sail and the upper sail, but because the upper sail has looseness to start, the the arch of the flat will bulge upwards and form camber in the resultant airfoil. So, one would keep note that both upper and lower sail will be affected in shape. Similar shared presses occur in many kinds of other wing stuffings.

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Making one's own Mylar foil balloons for stuffing a HG's wing is doable. One tactic is to avoid having a case for the foil balloons; just stuff the raw foil balloon into the main chamber of the DS wing. The foil balloons could be with a shape designed by the maker of the HG. One approach is a stack of flying-saucer foil balloons anchored to the LE spar. Another approach is to make full ribs in foil balloon; stuff the balloon to the interior main chamber of the sock DS sail; stay-up anchoring could be by tiny strings in three places; valving could be hosed out the aft bottom of the sail or some other judcious position; the foil balloons could be inflated after all rigging and socking is done; then the inflation would make the sock sail taut. Flight check, clear, fly. Report results.

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https://www.willswing.com/t3/ See wing inserts.
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