Slipstream
Member
Hi folks. I have an RV-7, IO-360-M1B engine, James cowl, Skybolt fasteners.
Getting the James Cowl to fit has been an excruciating process -- I speak from the experience of successfully installing a Van's cowling on a different engine, same airframe.
Anyway, finally got to it where it looked like it fit nicely, and took it flying. Holy chit, as soon as I get above 110 knots, the back edge of the top cowling pulls upwards, and causes a godawful vibration/noise that's just not going to work for me. The Skybolt fasteners are holding it down, obviously, but the fiberglass is flexing upwards in the 3.5" gaps between the fasteners. At 140 kts, the peaks are seriously .5" or more from their at-rest positions. At this point, the noise is painful through my Bose A20s.
I was able to verify this as the noise source by duct-taping the aft edge of the cowling to the aluminum airframe behind it. Blessed normal airplane noise.
Let's see, more details: I'm using Van's baffle system around the back and sides of the engine. I made fiberglass diffusers to join the baffles to the aluminum inlet rings. I'm using this system because the James plenum fit exactly as any fiberglass molded by a 4 year-old would. I'm using the James ram-air inlet.
Any thoughts are welcome before I scrap this troublesome system and send Van's more money.
Getting the James Cowl to fit has been an excruciating process -- I speak from the experience of successfully installing a Van's cowling on a different engine, same airframe.
Anyway, finally got to it where it looked like it fit nicely, and took it flying. Holy chit, as soon as I get above 110 knots, the back edge of the top cowling pulls upwards, and causes a godawful vibration/noise that's just not going to work for me. The Skybolt fasteners are holding it down, obviously, but the fiberglass is flexing upwards in the 3.5" gaps between the fasteners. At 140 kts, the peaks are seriously .5" or more from their at-rest positions. At this point, the noise is painful through my Bose A20s.
I was able to verify this as the noise source by duct-taping the aft edge of the cowling to the aluminum airframe behind it. Blessed normal airplane noise.
Let's see, more details: I'm using Van's baffle system around the back and sides of the engine. I made fiberglass diffusers to join the baffles to the aluminum inlet rings. I'm using this system because the James plenum fit exactly as any fiberglass molded by a 4 year-old would. I'm using the James ram-air inlet.
Any thoughts are welcome before I scrap this troublesome system and send Van's more money.