Noise and vibrations in RV-6

triguyinla · #1 02-05-2009, 05:02 PM

How loud is normal in an RV6 with O-320? Since I have very limited experience in any RVs other than mine I'm wondering if there might be something wrong with mine. It's much louder than a certificated aircraft. I have no insulation or dampening foam or anything in the firewall or on the sidewalls, etc. The vibrations are more concerning. At cruise approx. 2250 RPM if I put my feet flat on the floor, there is definately a reasonably annoying constant vibration that makes me wonder if it is normal.

Anyone in S. CA? I'd like to see your RV if you're in the local area.

Steve

N55CU · #2 02-05-2009, 05:11 PM

Check your clamp's on the tailpipes where they exit the cowl. I had vibrations on my 7 and Vetterman told me that the clamps should be even with the firewall. I adjusted and changed and adjusted and most are now gone! Adding carpet and foam to the side panels aft of the firewall also helped!
Randy "Utz"
N55CU / RV-7 / 180 hrs
Charlotte, N.C.

L.Adamson · #3 02-05-2009, 08:23 PM

Quote:

Originally Posted by triguyinla

How loud is normal in an RV6 with O-320? Since I have very limited experience in any RVs other than mine I'm wondering if there might be something wrong with mine. It's much louder than a certificated aircraft. I have no insulation or dampening foam or anything in the firewall or on the sidewalls, etc. The vibrations are more concerning. At cruise approx. 2250 RPM if I put my feet flat on the floor, there is definately a reasonably annoying constant vibration that makes me wonder if it is normal.

Anyone in S. CA? I'd like to see your RV if you're in the local area.

Steve

I have an 0360 & no insulation. It's very loud, and I use ANR headseats, and just got the mic covers from Oregon Aero. But..................although there is some vibration, it's actually not annoying. I suppose I'd check the exhaust mounts as suggested.

L.Adamson --- RV6A

Geico266 · #4 02-08-2009, 09:10 PM

Have the prop dynamically balanced.

Paul Eastham · #5 02-08-2009, 09:21 PM

My 9A is a similar situation, both with the noise and the floor vibration, and I wonder about it as well. For the noise, I got a Halo headset and am comfortable. The floor vibrations are strong despite a layer of that black foam. They don't bother me much -- though some of my passengers have seemed a little concerned.

I have had my prop dynamically balanced.

I haven't done much troubleshooting...one of these days. Not sure I have enough clearance between my cowl and engine mount to lower the exhaust clamps.

BillOrcutt · #6 02-28-2009, 11:07 PM

This is a very common problem, and I've had it on 3 RV's dating back to the early 90's (RV-6A, 2 -7A's). If the exhaust stacks are not touching the firewall, heavy rubber matting on the floor helps a lot. However, Larry Vetterman recently displayed pictures of a faired-in cowling underside that may be the answer. Apparently the angle between the firewall and the floor pan should not be 90 degrees, but should be rounded out to minimize the airflow disturbance. Racers know this, and the RV-8's incorporate it, I believe. Vetterman's underside fairing might just be the answer to this very common, long-standing issue, which most RV pilots grow to ignore.

penguin · #7 03-01-2009, 03:22 PM

I found one of the key issues for floor vibration is the length of the exhaust stacks and the angle they make to the fuselage - always assuming the exhaust supports are clamped to the engine (if they're clamped to the airplane they can transmit vibration). Check if there are any exhaust stains on the underside. If there are it indicates the exhaust gas is hitting the fuselage floor and inducing vibration. One cause is shortening the regular tail pipes, another is making the angle between the tailpipe and the bottom the fuselage too shallow. It should be greater than 25 degrees. You can reduce the vibration to a reasonable level, difficult to eliminate it altogether

Hope this helps, Pete

Steve Barnes · #8 03-01-2009, 07:40 PM

When building my plane, I put a 3/4 " fire resistant foam on my floor, then built another .025 floor on top. I also insulated my firewall, and thats it. Some people spend alot of time and extra weight insulating their whole cockpit and luggage area. I'm very pleased with how quiet my plane is at 190 Kts. There's only one other place that I would recommend insulation, and that is the canope, however I haven't figured a way to do it, and still be able to see out. When I take my head sets off in flight, the main noise that I hear is wind. The most significant noise reduction comes from ANR headsets. The headsets are DC 10-30 with the headsets Inc. kit.

Steve Barnes, The Builders Coach

Jamie · #9 03-02-2009, 05:24 AM

I have the classic aero designs carpet, which incorporates a thick foam padding and fits perfectly in my -7A. The carpet makes a big difference in terms of noise and vibrations. In fact, the first time I flew with the carpet I was caught off-guard when I went full throttle on the runway because it was that much quieter and I found myself checking my instruments more than usual to make sure I was developing full power.

So in short, I really like the carpet. I've loaned my front carpet to others to try and they reported similar findings.

The carpet is the only insulation I have. I have none on the firewall or side walls.

As for ears, that's what good ANR headsets are for.

wv4i · #10 03-02-2009, 06:47 AM

I assume thread starter has a c/s prop, Hartzell? At 2250 prop rpm, you're at the top of the stated rpm range to avoid, at least on the O-360 application, can't remember if the O-320 is the same? In my fmr RV6 with an O-320 and current RV6 with O-360, both Hartzell CS props, I found/find that about 2300 rpm is where vibration begins, even with my very well balanced prop, in cruise flight. My tach is accurate to within 10 rpm.

As with any new vibration or sound, you definitely need to find out why, the source, especially if this vibration is new.

I recently had a new vibration emerge, and it turned out to be a cracked backing plate for the prop spinner. Grabbing the spinner on pre flight was unremarkable. Another set of eyes found this problem, i.e. a VERY experienced home builder (not me) and experimental driver. Does not jump out at you with our close spinner to cowl clearances. Many other subtle problems will not jump out as well.

You might also want to look at motor mount attach points, firewall and engine. These can lose torque over time, even with witness marks, become a vibration source, set up a harmonic, etc.

You don't mention TT in your airplane, but might be worthwhile to take another RV6 driver for a ride in your plane, get another opinion?