Abstract: A system may include one or both of a light emitter and a light receiver. The system may include an optical filter adjacent one or both of the light emitter or the light receiver. The optical filter includes a wavelength selective scattering layer. The wavelength selective scattering layer may have a near-infrared scattering ratio of less than about 0.9. The filter may have a visible reflective haze ratio of greater than about 0.5. A method may include disposing the wavelength selective scattering layer adjacent one or both of the light emitter and the light receiver. An article may include the optical filter. The wavelength selective scattering layer may have an average near-infrared scattering of less than 60%, an average visible scattering of greater than 10%, and a difference between the % total visible reflectance and the % diffuse visible reflectance of less than 20.

Abstract: A propeller guard assembly for watercraft that, in cooperation with a rotating propeller, creates a substantial increase in propulsive thrust and provides improved all around shielding of the latest state of the art propeller configurations such as wider propeller blades and contra rotating dual propeller systems.

Abstract: A propeller guard assembly for water craft that, in cooperation with a rotating propeller, creates a substantial increase in propulsive thrust and provides improved all around shielding of the latest state of the art propeller configurations. The increase in propulsive thrust of the propeller guard assembly of the invention is created primarily by the angle of the attack and hydrofoil cross section of the four guard rings or cowlings of the device. A secondary reason for the increase in propulsive thrust of the propeller guard assembly of the invention resides in the fact that the thrust realized is equal to the ratio between the effective projected propeller area and the area of trailing edges of the large primary and secondary guard rings which decreases the tendency of the propeller race to spread, particularly at high propeller slip during acceleration and take off.

Abstract: A propeller guard assembly for water craft that, in cooperation with a rotating propeller, creates a substantial increase in propulsive thrust and provides improved all around shielding of the latest state of the art propeller configurations. The increase in propulsive thrust of the propeller guard assembly of the invention is created primarily by the angle of the attack and hydrofoil cross section of the four guard rings or cowlings of the device. A secondary reason for the increase in propulsive thrust of the propeller guard assembly of the invention resides in the fact that the thrust realized is equal to the ratio between the effective projected propeller area and the area of trailing edges of the large primary and secondary guard rings which decreases the tendency of the propeller race to spread, particularly at high propeller slip during acceleration and take off.

Abstract: In all three versions, the bottom rail has a flat, smooth bottom and does not tilt. In two versions, transverse horizontal holes receive ladder cords. In one of these versions, another horizontal hole opening at the rear of the rail extends obliquely into intersection with the transverse hole midway between the front and rear of the rail. A vertical hole extends down from the rail top to this intersection. A lift cord extends down through the vertical hole into the oblique hole where a knot on the lift cord fixes the end of the cord in the oblique hole. In too the other of these two versions, a horizontal transverse hole above each ladder cord hole receives a lift cord which extends out at the front and rear of the bottom rail. These lift cords, and the ladder cords, extend entirely up to the headrail. In this version, each slat has a notch at the front edge and rear edge, receiving the corresponding lift cord and ladder cord.

Abstract: A propeller duct assembly for use on water craft which enhances the thrust of the propeller, increases fuel efficiency, stabilizes boat handling, serves as a safety factor for swimmers, and which also serves to protect the propeller against submerged objects.