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Wunderlich Wind Deflector - Review and Testing
Yesterday I received a Wunderlich Wind Deflector. This reports on the installation, testing and effectiveness.
APPARTUS
- Me: 5'-9" tall, 30" inseam.
- Honda NC750-S 2014
- CalSci (tall screen)
- Wunderlich Wind Deflector (visor)
INSTALLATION
- The manufacturer recommends adding thread-lock to all screws. Instead, I added teflon plumber's tape to all threaded screws. This creates a resistive fit of the screws, while allowing future adjustment.
- The manufacturer provides rubbers seats for only one of the two sides of the metal mount, which contacts the plastic screens. Instead, I added rubber seats to both sides of mount at each contact. The rubber seats where affixed with two-sided tape.
TESTING
- Most screws were fully tightened except for the two screws responsibility for setting the height and rake angle of the visor. Those screws were partially tightened, to allow manual readjustment WHILE ridding the bike at speed.
- Added tell-tales (string) to edge of wind screen and wind visor. These reveal laminar or turbulent air flow that trails past the edge of the screens.
- Ride the bike at 100 kph on highway, with repeated adjustment of the visor's angle.
- Note the noise level to rider for various postures (height and rake angle) of the visor, and turbulence on the tell-tales.
MY THEORY
The visor had only the effect of changing the location of the boundary layer zone for the rider. It did not seem to have any effect on buffeting (neither creating nor eliminating). The experienced noise was attributed to the small eddies that form along the turbulent boundary layer.
The rake angle of the visor can create laminar flow in the start of the boundary layer, if the angle closely matches the wind screen. However, any such laminar flow will always turn into turbulent flow after reaching out to the distance where the rider's ears are. As such, the highest noise level is coincident with the rider's ears being within the boundary layer zone.
MY OBSERVATIONS
The posture with the quietest effect for the rider, is when the top of visor is at eye level (or no more than 1 inch below) of the rider - this is just above height of ears. The trailing air is very disturbed, as seen with turbulent tell-tales. However, the high turbulence does not have any acoustic effect (noise or buffeting) on the rider, since the boundary layer is above the rider's ears - on account of the tall posture of the visor. From previous sound meter testing, I would surmise the visor lowered the noise level by about -10 dB ... this is a huge improvement. Without the visor I would need to speak loudly to hear my voice in my helmet; while with the visor I would need only to speak calmly to hear my voice. This posture will give worse fuel economy (although its impact would be very insignificant).
The posture with the least force on the visor is when the rake of the visor is only slightly (5 degrees) less than the rake of the wind screen. Thus, the visor forms a continued circular arc above the wind screen (think of a semi-spherical profile on the leading edge of an aerodynamic tear-drop shape). At this posture, the air pressure of the front face closely matches that on the rear face. This serves to extend laminar air flow into a larger envelope than otherwise would exist without the visor. This posture will give best fuel economy. This was not quietest, since the boundary layer was below the rider's ears, thus some noise was experienced.
PHOTOS
1) Most quiet (tallest).pg
2) Most aerodynamic.jpg
3) Compromise to use.jpg
Yesterday I received a Wunderlich Wind Deflector. This reports on the installation, testing and effectiveness.
APPARTUS
- Me: 5'-9" tall, 30" inseam.
- Honda NC750-S 2014
- CalSci (tall screen)
- Wunderlich Wind Deflector (visor)
INSTALLATION
- The manufacturer recommends adding thread-lock to all screws. Instead, I added teflon plumber's tape to all threaded screws. This creates a resistive fit of the screws, while allowing future adjustment.
- The manufacturer provides rubbers seats for only one of the two sides of the metal mount, which contacts the plastic screens. Instead, I added rubber seats to both sides of mount at each contact. The rubber seats where affixed with two-sided tape.
TESTING
- Most screws were fully tightened except for the two screws responsibility for setting the height and rake angle of the visor. Those screws were partially tightened, to allow manual readjustment WHILE ridding the bike at speed.
- Added tell-tales (string) to edge of wind screen and wind visor. These reveal laminar or turbulent air flow that trails past the edge of the screens.
- Ride the bike at 100 kph on highway, with repeated adjustment of the visor's angle.
- Note the noise level to rider for various postures (height and rake angle) of the visor, and turbulence on the tell-tales.
MY THEORY
The visor had only the effect of changing the location of the boundary layer zone for the rider. It did not seem to have any effect on buffeting (neither creating nor eliminating). The experienced noise was attributed to the small eddies that form along the turbulent boundary layer.
The rake angle of the visor can create laminar flow in the start of the boundary layer, if the angle closely matches the wind screen. However, any such laminar flow will always turn into turbulent flow after reaching out to the distance where the rider's ears are. As such, the highest noise level is coincident with the rider's ears being within the boundary layer zone.
MY OBSERVATIONS
The posture with the quietest effect for the rider, is when the top of visor is at eye level (or no more than 1 inch below) of the rider - this is just above height of ears. The trailing air is very disturbed, as seen with turbulent tell-tales. However, the high turbulence does not have any acoustic effect (noise or buffeting) on the rider, since the boundary layer is above the rider's ears - on account of the tall posture of the visor. From previous sound meter testing, I would surmise the visor lowered the noise level by about -10 dB ... this is a huge improvement. Without the visor I would need to speak loudly to hear my voice in my helmet; while with the visor I would need only to speak calmly to hear my voice. This posture will give worse fuel economy (although its impact would be very insignificant).
The posture with the least force on the visor is when the rake of the visor is only slightly (5 degrees) less than the rake of the wind screen. Thus, the visor forms a continued circular arc above the wind screen (think of a semi-spherical profile on the leading edge of an aerodynamic tear-drop shape). At this posture, the air pressure of the front face closely matches that on the rear face. This serves to extend laminar air flow into a larger envelope than otherwise would exist without the visor. This posture will give best fuel economy. This was not quietest, since the boundary layer was below the rider's ears, thus some noise was experienced.
PHOTOS
1) Most quiet (tallest).pg
2) Most aerodynamic.jpg
3) Compromise to use.jpg
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