apkp777

apkp777

Well Known Member
Hey all,

8.9 hrs into Phase I and trying to nail down all the gripes. I am getting a rumble in my LH side FWD floor skin. I talked to Larry Vetterman today and he said this is common and that his sub-cowl mod took care of it on his RV.

I am not prepared to do his mod just yet and am wondering if anyone had a more simple solution?
 
Have you got the turn-down exhaust tips? I had some rivets working loose on the bottom of the RV-8 a couple of years ago, and we added the tips - the problem went away.

Larry supplied the tips.

Paul
 
No, I will get a set. I saw that he offers them. He said his "sub-cowl" is the way to go. I really don't want to get into to big of a mod right now. The tips will be easy.

My classic aero interior (2 weeks late so far) will have some padding in the FWD carpet. I am sure that'll help some. I'd rather solve the vibration rather than deaden it.

I was thinking of adding a cross stringer to help reinforce the floor. I can imagine there be cracks if this continues.
 
Brantel said:
Mine does this as well... On my second flight it scared me!!!!
Click to expand...

I ignored it and my Halo headset really helped. However, I had some time now to dial in all my issues and this is one I'd like to address.

Have you done anything to fix this?
 
Another way to help lessen the impact of this problem is to go to Walmart and buy a sleeping bag pad. It is a rolled up piece of foam rubber about 1" thick. I cut one up and glued it to my floors underneath the carpet. It helps to cut the rumble. I also had turned down tips on the exhaust as well, but you still can feel the vibrations in your feet and legs, expecially on long flights.
 
I talked to Larry Vetterman again yesterday. He told me the "turned down tips" are really for the RV-8. The rumble he thinks is not coming from exhaust but the airflow as it tumbles over the cowl exit and onto the FWD LWR skin. It makes sense. There is a YouTube video out their that shows what's happening.

He thinks the fix is the sub cowl. My interior should help as well. I think I'll have to live with it for now.
 
Think About It - You're Inside a Snare Drum.

Tony:
The carpeting is going to help - a lot. I've had closed cell foam between the stringers with carpeting over the top. Worked pretty well. Just switched to the Classic Aero carpeting and it's even better. You may find after installing that you don't need anything else. If you're going with the interior as well, you're plane is going to be quieter than most - even the aviator side panels seem to contribute to sound deadening. Now if I can just scrape together a few bucks for a Beyerdynamics headset.
Terry, CFI
RV-9A N323TP
 
terrykohler said:
Tony:
The carpeting is going to help - a lot. I've had closed cell foam between the stringers with carpeting over the top. Worked pretty well. Just switched to the Classic Aero carpeting and it's even better. You may find after installing that you don't need anything else. If you're going with the interior as well, you're plane is going to be quieter than most - even the aviator side panels seem to contribute to sound deadening. Now if I can just scrape together a few bucks for a Beyerdynamics headset.
Terry, CFI
RV-9A N323TP
Click to expand...

Thanks Terry,

I have the Halo headset and am loving it. Yes, I figure the interior will help a lot. I was on the fence about sidewalls, now I am thinking definitely yes.

I absolutely love my RV, but she sure makes lot's of noise.
 
Here's an update on my original "rumble" post.

First, as I originally posted, I was startled by the severe "rumble", "vibration", or just plane NOISE coming from the FWD lower skin under my feet. On long flights it was very distracting and actually quite fatiguing. Well, after I installed my Classic Aero interior with the thick pad, it really "dulled" the rumble, but did not get rid of it. I called Vetterman thinking that it was the exhaust stacks. He indicated he did not believe they were the culprit but rather the air flowing over the cowl exit. He told me that down turn tips would not help. They were really for the RV8. He thought his Sub-Cowl mod helped his "rumble". (He had the same condition on his -7A).

Anyway, I didn't have a fix, so I bought some heavy rubber automotive floor mats that along with the Classic Aero interior, really helped, but did not get rid of it. I hate to toot the "Vetterman Muffler" horn again, but I really thing that they have solved the "rumble". I even had another RV9 guy (he has the same problem) confirm my rumble is not longer there.

So, whether it's a "one of" situation or not, I don't know. But you may try a set of mufflers if you have the same condition.
 
My experience with upholstery and exhaust tips

When I built my RV-6A I got the upholstery video the floor pad material carpeting and upholstery from Becki Orndorf. I considered it part of the airplane and did not fly before all of that upholstery work was done so I do not have the desired before and after cases. The back side of the firewall is covered with an aluminum backed black foam rubber pad. The floor between the stringers is filled with a black foam rubber pad glued in place with 3M spray adhesive (77 seems like the number but it is what Becki recommended in the video). On top of that the carpet is glued in place with the same adhesive. On the sides of the cockpit back to the baggage compartment bulkhead I glued on thin white foam and on top of that the cloth upholstery. I never experienced the noise that many builders talk about and I have had no structural cracking after 600 hours and over 6 years. At one point in the quest for speed I cut off the turned down ends of my stock Vetterman crossover exhaust for my O-360-A1A and there was no noticeable change in noise. I have a Hartzell C/S B/A prop with F7496 blades now but originally had a non-blended airfoil Hartzell C/S prop with F7666 blades. Neither caused a noise problem. in cruise I run 2450 rpm and in races I run 2720 rpm (or what ever I can get - sometimes 2730 rpm). I notice no difference in the noise or vibration level following the dynamic balance by Hartzell. Consider this, you start out with every part of your power system statically balanced when you add some off center weight to the flywheel or aft spinner bulkhead to offset vibration at a specific rpm. The static balance is changed and the effect at other rpms is uncertain.

I suspect that you will be happy with the insulation, carpet and upholstery. My wife tried the light weight plug in you ear headset for a while but went back to the David Clarks to cut down on the noise. It is a noisy environment even with all of the insulation but no more so than other production airplanes I have flown.

If someday you add the stiffener angles to the floor you should report back your findings.

Bob Axsom
 
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DynaMat

I am using DynaMat on the floors and sides and seems to help a lot.
Balance is also the key.

Hope it helps.
 
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