Van's Air Force
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Floor vibration
- Thread starter 0ptions
- Start date
cthelan
Member
hi doug
I am also flyin an 8 with the same issue. In my case, the vibration is not too bad with my feet on the rudder, but as soon as i put my feet on the floor the vibration is very bad. From reading other posts, I've heard that its not so much the exhaust as the general vibration from the engine/prop. Could be wrong, but I'm in the same boat as you lookin for less vibration from the floors.
I am also flyin an 8 with the same issue. In my case, the vibration is not too bad with my feet on the rudder, but as soon as i put my feet on the floor the vibration is very bad. From reading other posts, I've heard that its not so much the exhaust as the general vibration from the engine/prop. Could be wrong, but I'm in the same boat as you lookin for less vibration from the floors.
rvpilot
Well Known Member
Addressed in another thread!
Check out this thread-
http://www.vansairforce.com/community/showthread.php?t=5649&highlight=cracking
It would be nice to know if any of these guys had any success. I am also having this same problem. Curious as to whether the planes experiencing this have short exhaust pipes or long pipes coming out of the cowl.
Check out this thread-
http://www.vansairforce.com/community/showthread.php?t=5649&highlight=cracking
It would be nice to know if any of these guys had any success. I am also having this same problem. Curious as to whether the planes experiencing this have short exhaust pipes or long pipes coming out of the cowl.
Floor Vibration
Thanks, sounds like others have the same issues. I have the Vetterman exhaust on a TMX 0360/FP. I was thinking of re-alligning the direction the pipes exit the cowl or some kind of expanding foam. (heat may be an issue). The cracking issues may require a doubler of sorts. I would do it now but I'm having too much fun flying the first 40 off. I'll check to see if it's related to a specific prop/floor harmonic at differnt RPM's.
Thanks, sounds like others have the same issues. I have the Vetterman exhaust on a TMX 0360/FP. I was thinking of re-alligning the direction the pipes exit the cowl or some kind of expanding foam. (heat may be an issue). The cracking issues may require a doubler of sorts. I would do it now but I'm having too much fun flying the first 40 off. I'll check to see if it's related to a specific prop/floor harmonic at differnt RPM's.
N130WN
Well Known Member
I've had these tips on my RV-8 since the beginning. I've been told my plane is quieter than others. No probs with floor vibration, and I have the pipes tucked **up** as far a possible . Might be worth a try....
http://www.wicksaircraft.com/catalog/product_detail.php/pid=4778~subid=1172/index.html
http://www.wicksaircraft.com/catalog/product_detail.php/pid=4778~subid=1172/index.html
piccolo pipes quiter inside and/or outside?
Larry,
From which perspectives are the comments about "quiter" aimed? From passengers inside your plane comparing it to other RV8s or from people on the ground comparing your planes sound as compared to another RV8's flying by or both?
Also, my cooling ramp has just now developed cracks round the two outer end rivets that attached the stiffener. On one the rivet no longer contacts the skin and can be completely pushed inside the skin. I guess the way to fix that would be to structural bond a small round aluminum patch over the bad rivet and also rivet that patch to the stiffener. The other rivet still has some skin meat under it so it can be stop drilled, I hope, but I guess it will fail too at some piont so might as well do that to both rivets. I think the exaust has a lot to do with it. There's a lot of oil canning to begin with on that ramp. It's a QB fuse and seems to be a very common problem.
Lucky
Larry,
From which perspectives are the comments about "quiter" aimed? From passengers inside your plane comparing it to other RV8s or from people on the ground comparing your planes sound as compared to another RV8's flying by or both?
Also, my cooling ramp has just now developed cracks round the two outer end rivets that attached the stiffener. On one the rivet no longer contacts the skin and can be completely pushed inside the skin. I guess the way to fix that would be to structural bond a small round aluminum patch over the bad rivet and also rivet that patch to the stiffener. The other rivet still has some skin meat under it so it can be stop drilled, I hope, but I guess it will fail too at some piont so might as well do that to both rivets. I think the exaust has a lot to do with it. There's a lot of oil canning to begin with on that ramp. It's a QB fuse and seems to be a very common problem.
Lucky
Mine has had floor vibration/resonance since day 1. It's less of an issue at 2400 rpm and above.
IMO, it's 100% due to the pulsations from the exhaust gases. One of these days, or on my next -8, I'll stiffen the sheet metal and thoroughly insulate the sub-floor (read stuff it full of fiberglass) from the firewall back as far as possible.
IMO, it's 100% due to the pulsations from the exhaust gases. One of these days, or on my next -8, I'll stiffen the sheet metal and thoroughly insulate the sub-floor (read stuff it full of fiberglass) from the firewall back as far as possible.
AlexPeterson
Well Known Member
Low Pass said:
You may be correct, but what do you base it on? The prop pulses are proportional to the exhaust pulses, so the only way to separate them is to extend the pipes way back and see what happens.
The pulses from the prop are impressive, just stand up with the canopy open at idle power! (Not recommended for tip-ups
)
13brv3
Well Known Member
The current Vetterman's exhaust instructions advise you to allow the exhaust tips to extend down low, near the cowl. The reason is to reduce the vibration effect the exhaust has on the floor. I did that on this -8, and can't say that it's any different from the first one where I had the pipes up high. Both vibrate, and you can change the tone by moving your feet around.
Cheers,
Rusty (6.3 hours)
Cheers,
Rusty (6.3 hours)
Good point. I hadn't considered prop wash. But it seems that stiffening the skin and damping the resonance with some filler would solve the prob in either case. Extending the pipes is not a very serious option for me.AlexPeterson said:You may be correct, but what do you base it on? The prop pulses are proportional to the exhaust pulses, so the only way to separate them is to extend the pipes way back and see what happens.
The pulses from the prop are impressive, just stand up with the canopy open at idle power! (Not recommended for tip-ups
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Stiffening the floor
Hi folks,
I am at the beginning of building the fuselage. Which skin are you suggesting stiffening and how would you go about doing so? If this is the forward section of floor, i.e. right under your feet and just aft of the pedals, then stuffing it with fiberglass wouldn't be difficult--but I am thinking that the time to do so is early in the construction process.
At any rate, if I should make this mod, I would really appreciate some advice on where exactly to beef things up.
Regards,
Michael Wynn
RV 8 (Just starting the) Fuselage
San Ramon, CA
Hi folks,
I am at the beginning of building the fuselage. Which skin are you suggesting stiffening and how would you go about doing so? If this is the forward section of floor, i.e. right under your feet and just aft of the pedals, then stuffing it with fiberglass wouldn't be difficult--but I am thinking that the time to do so is early in the construction process.
At any rate, if I should make this mod, I would really appreciate some advice on where exactly to beef things up.
Regards,
Michael Wynn
RV 8 (Just starting the) Fuselage
San Ramon, CA
I'd stiffen the cowling outlet air ramp and the outer skin immediately aft (the one between the gear penetrations, I believe). As for how to do it, there are many possibilities. Everything from refab'ing out of thicker sheet to adding angle stiffeners to laminating the sheets from the inside with some FRP material. Just have to look at the possible internal interferences and how you want to alter the sheet.mlwynn said:
As for how to insulate. Many options here too. Use some batting material, spray foam, or just loose fiber stuffed liberally into the void. I'd do the latter, myself.
Done during the forward lower fuse assembly would definitely be easier.
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jbDC9
Well Known Member
My -8 has a 180 hp O-360 with a 4 into 1 exhaust system; the single collector pipe runs out past the cowling and extends back maybe 10 inches or so along the outlet ramp and hangs several inches below.
This afternoon was its 4th flight for a whopping total of 4 hrs... so far it's been smooth on the floor, no vibrations or rattling; that is until I tried a bit of slow flight. As the speed bled back to around 55-60 kts indicated with power on to maintain altitude, I started hearing/feeling some vibration and rattling coming from forward and below. Dropped the nose, built up some speed and it went away.
So, after reading this thread I'm beginning to think that while at a high angle of attack and power on, the ramp skin starts rattling and vibrating from the slipstream and prop pulses... does this seem like a reasonable explanation? Anyone else run into this? It was a bit unnerving to hear/feel all that after being relatively smooth and quiet at normal speeds.
John
This afternoon was its 4th flight for a whopping total of 4 hrs... so far it's been smooth on the floor, no vibrations or rattling; that is until I tried a bit of slow flight. As the speed bled back to around 55-60 kts indicated with power on to maintain altitude, I started hearing/feeling some vibration and rattling coming from forward and below. Dropped the nose, built up some speed and it went away.
So, after reading this thread I'm beginning to think that while at a high angle of attack and power on, the ramp skin starts rattling and vibrating from the slipstream and prop pulses... does this seem like a reasonable explanation? Anyone else run into this? It was a bit unnerving to hear/feel all that after being relatively smooth and quiet at normal speeds.
John
Bill Dicus
Well Known Member
Floor vibes
Not flying yet so don't know if mine will vibrate a lot. However, Steve Raddatz who has built 2 or 3 8's suggested putting foam as a filler under the ramp and says this helps damp vibration - seems easy to try. Maybe 'twill help. Bill
Not flying yet so don't know if mine will vibrate a lot. However, Steve Raddatz who has built 2 or 3 8's suggested putting foam as a filler under the ramp and says this helps damp vibration - seems easy to try. Maybe 'twill help. Bill
Rick Freeman had what sounds like the same problem with his RV-8. In addition, he was getting some small cracks in the fuselage sheet metal behind the exhaust. We solved the problem by installing some turned down exhause extensions that came with the exhaust system I had purchased from John Forsling for my RV-8 project. His system is almost identical to the Veterman system with the exception of the extensions which seem to get the vibrations away from the fuselage. Anyway, you might try an extension and see what happens on your airplane. My RV-8 has been flying for over a year, and it has very little if any vibration in the feet area.
exhaust extensions?
Once he had the cracks then added the extensions I don't know how one can say it fixed future cracks definitavely. He may not have had any more anyway. The cracks I have already don't seem to be getting an worse and no new ones have popped up. Did he measure what the extensions did to his speed/different engine related temps? Was there a noticely different sound inside the fuselage? Quieter? My Vettermans exhaust has a slight downward bend towards the exhit end but they are very slight. I've never seen the extensions you are referring to. Can you describe it in more detail, maybe upload a picture? Is this something that can fit another design like the piccolo extensions?
Tom Schad said:
Once he had the cracks then added the extensions I don't know how one can say it fixed future cracks definitavely. He may not have had any more anyway. The cracks I have already don't seem to be getting an worse and no new ones have popped up. Did he measure what the extensions did to his speed/different engine related temps? Was there a noticely different sound inside the fuselage? Quieter? My Vettermans exhaust has a slight downward bend towards the exhit end but they are very slight. I've never seen the extensions you are referring to. Can you describe it in more detail, maybe upload a picture? Is this something that can fit another design like the piccolo extensions?
Vans Comment on cracking
Hi all,
I posed this to Van's to see if they had any experience. Here is what they had to say:
> There is also an ongoing thread about floor vibration in the -8 along
> with cracking of the cooling ramp area. Are you looking at this
> problem and should there be additional reinforcement as some have
> suggested?
>
We don't have a problem to look at; the 8 and 8A we have don't have
any cracks. They do have the older style exhaust with downturned
pipes, and possibly adding end pipes to the current Vetterman
system that deflect the exhaust stream down away from the ramp
might help prevent cracks. You could add some reinforcement, but
we don't have any plans/parts, so you'd have to decide what you
think is appropriate.
I from this that it is their opinion is that this problem is a result of the exhaust system. If that is true, perhaps Vetterman could be coaxed into making the tail pipe a little longer and downward directed. Would that somehow foul up its function? I am a true amateur here and wonder what the more experienced of you think.
Regards,
Michael Wynn
RV 8 Fuselage
San Ramon, CA
Hi all,
I posed this to Van's to see if they had any experience. Here is what they had to say:
> There is also an ongoing thread about floor vibration in the -8 along
> with cracking of the cooling ramp area. Are you looking at this
> problem and should there be additional reinforcement as some have
> suggested?
>
We don't have a problem to look at; the 8 and 8A we have don't have
any cracks. They do have the older style exhaust with downturned
pipes, and possibly adding end pipes to the current Vetterman
system that deflect the exhaust stream down away from the ramp
might help prevent cracks. You could add some reinforcement, but
we don't have any plans/parts, so you'd have to decide what you
think is appropriate.
I from this that it is their opinion is that this problem is a result of the exhaust system. If that is true, perhaps Vetterman could be coaxed into making the tail pipe a little longer and downward directed. Would that somehow foul up its function? I am a true amateur here and wonder what the more experienced of you think.
Regards,
Michael Wynn
RV 8 Fuselage
San Ramon, CA
Exhaust Vibrations
Rick Freeman has the same vibration problem in his RV-8. It got so bad that cracks were developing in the metal near the exhaust stacks. We solved the problem by putting some turned down exhaust extensions on his pipes. The extenxions are part of the Forsling exhause system for RV's. John's system is a very high quality cross over system that is made for the RV. It is similiar to the Veterman system and priced about the same, for those of you who are not familiar with it. I have his entire system on my RV and no vibrations. Tom Schad RV-8 N558TX
Rick Freeman has the same vibration problem in his RV-8. It got so bad that cracks were developing in the metal near the exhaust stacks. We solved the problem by putting some turned down exhaust extensions on his pipes. The extenxions are part of the Forsling exhause system for RV's. John's system is a very high quality cross over system that is made for the RV. It is similiar to the Veterman system and priced about the same, for those of you who are not familiar with it. I have his entire system on my RV and no vibrations. Tom Schad RV-8 N558TX
13brv3
Well Known Member
Tom Schad said:
Hi Tom,
Any chance of pointing us to a picture of these turned down exhaust extensions? "Turned down" can mean anything from a slight turn, to 90 degrees, so I'm wondering exactly what direction they point in relation to the bottom of the plane.
The old Vetterman exhaust didn't have a turn, but the newer systems do, and they also warn you to let the pipes hang fairly low, to keep the exhaust farther from the floor. Best I can tell, that doesn't help, because I still have the vibration despite following all the recommendations.
Cheers,
Rusty
DHeal
Well Known Member
Be careful with those pinched-off / multi-holed exhaust stack ends -- particularly if your mufflers have interior flame tubes. We had a set of those supposed exhaust quieting tips on our F33A. The interior flame tube in one muffler failed in-flight and the disintegrating parts blew back into the pinched-off / multi-holed exhaust stack end and virtually shut down the engine due to total blockage of the right-side exhaust pipe. We took them off and flew happliy ever after.
Danny King
Well Known Member
Guy's,
I've flown 860 hours and I do not have the floor vibration others have reported. My Vetterman Exhaust system is an early one that has turned down tail pipes. As I understand it, the turndown cost me three MPH of top speed, but the exhaust pulses are directed down away from the cooling ramp. Most guys want to go fast, so Larry Vetterman started making his system with strait exhaust tailpipes for those guys, and offers turndown tips for those that prefer a quieter ride. All you have to do is ask for them when you order.
I've worked with Larry and found him to be very helpful. I sent him a Sky Dynamics cold air induction sump along with the intake tubes and he built a one off system just for me, and charged me the standard price.
Call him if you want the turndown tubes, and I'm sure he will help you out.
Email me directly if you need his number.
[email protected]
I've flown 860 hours and I do not have the floor vibration others have reported. My Vetterman Exhaust system is an early one that has turned down tail pipes. As I understand it, the turndown cost me three MPH of top speed, but the exhaust pulses are directed down away from the cooling ramp. Most guys want to go fast, so Larry Vetterman started making his system with strait exhaust tailpipes for those guys, and offers turndown tips for those that prefer a quieter ride. All you have to do is ask for them when you order.
I've worked with Larry and found him to be very helpful. I sent him a Sky Dynamics cold air induction sump along with the intake tubes and he built a one off system just for me, and charged me the standard price.
Call him if you want the turndown tubes, and I'm sure he will help you out.
Email me directly if you need his number.
[email protected]
Airman Glen
I'm New Here
Exhaust extensions
My stacks were so short, I had to add extensions back in 2000 shortly after first flight.
I have good pictures of my work, but don't see where I can put them on for all to see. No vibration, no cracks, no problems of any sort.
My stacks were so short, I had to add extensions back in 2000 shortly after first flight.
I have good pictures of my work, but don't see where I can put them on for all to see. No vibration, no cracks, no problems of any sort.
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Dynamat applied to the cooling ramp (interior) worked for me. Just pull the hinge pin, drop the ramp and cover the entire ramp. I didn't cover the foward, curved portion, just the two rear squares. A little over 1 square foot of dynamat is needed.
I bought the wedge pak just in case I needed to cover the area under the rudder pedals above the cooling ramp but I haven't done that area yet.
The results were immediate.
BTW, I already have the turndowns on my Vetterman exhaust and had turned them in several different directions wth little difference noticed.
I bought the wedge pak just in case I needed to cover the area under the rudder pedals above the cooling ramp but I haven't done that area yet.
The results were immediate.
BTW, I already have the turndowns on my Vetterman exhaust and had turned them in several different directions wth little difference noticed.
I found this interesting concept (http://www.acoustop.com/pdf/AVP.pdf) at the Auckland Boat Show this year. Speaking to the guys on the stand about it, they reckoned they could laminate virtually any grade of aluminium sheet which could then be subsequently formed in the same manner of conventional Al sheet. The internal damping was quite remarkable
I was considering looking at swapping out some of my fuse floor panels with this stuff and getting them pre-punched by a local (Melbourne, Aus) supplier, however, since I'm still working on my wings and currently I'm away in the UK for a while, this could be some time away...
If anyone wants to explore the idea before me, fill your boots!
Cheers,
Andrew
I was considering looking at swapping out some of my fuse floor panels with this stuff and getting them pre-punched by a local (Melbourne, Aus) supplier, however, since I'm still working on my wings and currently I'm away in the UK for a while, this could be some time away...
If anyone wants to explore the idea before me, fill your boots!
Cheers,
Andrew
