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| This page is posted here since on some www. pages were misleading information
for Props and Fans - it is a safety issue and please don't use the next
best fan / prop on any engine without being familiar with your resulting
Tip speed.
I want to mention as well that "Gougeon Brothers" with the help of NASA have done multiple studies on wood composite for wind turbines ! If a composite part is correct build it has better physical properties than most plastics / metal's. As well as the physical properties of plastics is changing with temp. ( + / - = more flex / brittle ) and if not correct protected against UV will lose their strength. There is a lot more in a prop than just plain plastic is better than wood !!!!! The following part is from "Construction Requirements for Cruising
Hovercraft" of the HCGB
A number of proprietary axial and centrifugal fans are available and
suitable for use on light Hovercraft. The use of these fans is to be limited
to a combination of rotational speed and diameter giving blade tip speed
of less than that shown in the Table below.
Tip speeds in excess of 137 m/sec are likely to produce noise levels
in excess of 78 dBA at 15m distance. A maximum design tip speed of 122
m/sec is recommended to be used for this reason where practical. On the
next Table you find the fan speed in RPM for the limiting tip speeds -
122 m/sec is recommended - 137 m/sec design maximum - 168 m/sec is
the absolute limit for Multiwing Z and Nylon blade fans.
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