Kites for SFAP

Many types of kites may be employed, but no single kite is optimum for KAP under all circumstances. Various kites are utilized depending on wind conditions and weight of the camera rig. The goal is to provide enough lift to support the payload—normally ranging from 1 to 3 kg. For a given camera rig, large kites are flown for lighter wind and smaller kites for stronger wind. Kite designs fall in two general categories.

• Soft kites have no rigid structure or support to maintain their shape. The kite inflates with wind pressure and forms an airfoil profile, like the wing of an airplane, which provides substantial lift. Soft kites have several advantages for KAP. They have quite low weight-to-surface-area ratios, they are exceptionally easy to prepare and launch, and they are a breeze to put away—just stuff the kite into a small bag. For lightweight travel or backpacking, soft kites are the type of choice. Soft kites do have a tendency to collapse when the wind diminishes, so a watchful eye is necessary while in flight.

• Rigid kites employ some type of hard framework to give the kite its form and shape. Traditional supports of wood and bamboo are replaced in most modern kites by graphite rods and fiberglass poles. Their weight-to-surface-area ratios are intrinsically greater than soft kites, but rigid kites do have some important advantages for KAP. The primary advantage is the ability to fly well in light breezes without the danger of deflating and crashing. The frame maintains the kite's proper aerodynamic shape regardless of wind pressure. Although frame members may be disassembled, rigid kites can be troublesome for packing and travelling.

Among the most popular SFAP soft kites is the Sutton Flowform, invented and patented in 1974 by Sutton (1999). The flowform design employs venting to reduce drag and control air pressure within the kite body; these kites are known as smooth and stable flyers under moderate to strong wind (Fig. 8-23). Many other types of soft airfoils are utilized for SFAP. Various types of parafoils, vented or unvented, range in size up to > 10 m and can loft substantial payloads (Fig. 8-24).

Many rigid kite designs are suitable for KAP, including delta and delta-conyne types. Delta kites have a basic triangular shape, and the wing dihedral provides stability in flight (Fig. 8-25). The delta-conyne is essentially a triangular box kite with wings for added lift (Fig. 8-26). Both these styles are easy to fly and not likely to crash unexpectedly. They are good choices for both beginning and advanced kite flyers. However, they suffer from relatively high weights compared with their surface areas, particularly the delta-conyne, which may limit the payload capacity.

Kite Flowform Cartoon

FIGURE 8-22 Cartoon showing the typical arrangement for kite aerial photography. The camera rig is attached to the kite line, and a radio transmitter on the ground controls operation of the camera rig. The kite line normally is anchored to a secure point on the ground. Not to scale; adapted from Aber et al. (2003, fig. 1).

FIGURE 8-22 Cartoon showing the typical arrangement for kite aerial photography. The camera rig is attached to the kite line, and a radio transmitter on the ground controls operation of the camera rig. The kite line normally is anchored to a secure point on the ground. Not to scale; adapted from Aber et al. (2003, fig. 1).

The rokkaku is the favorite rigid kite of the authors (Fig. 8-27). This traditional Japanese kite has a low weight-to-surface-area ratio, and through centuries of design improvements it has achieved an elegant status among kite flyers. It provides the greatest intrinsic lifting power compared with other types of rigid kites in our experience. Rokkakus may be somewhat unstable in near-surface ground turbulence, but once aloft they are remarkably smooth and powerful fliers. We utilize rokkakus for the majority of our KAP, choosing for each survey from a selection of different sizes and tether lines depending on the current wind conditions.

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