Running a Full Wave Pipe

[Dave_Trible]

Randy makes a 75 muffler/pipe/header.

I don't think any of that has been available for awhile.   I'm not sure anybody is making stunt pipes these days.


Dave

[Dave_Trible]

One more follow up comment.   Yesterday I put the full wave pipe over into my Nats airplane ( ill- fated there due to a glob of solder in the tank it turned out) and the difference was just plain fun.   I have a prop on that needs to run a little more 4-2 that I normally run.   It is running like a classic 10 o’clock- 2 o’clock break in this mode.   When it breaks into the two cycle the airplane visibly slows down though still solid out there.   It slows BEFORE I put the nose down making the backside of maneuvers a casual thing without the downward rollercoaster feeling.   Like I said- fun!

Dave

[Brett Buck]

One more follow up comment.   Yesterday I put the full wave pipe over into my Nats airplane ( ill- fated there due to a glob of solder in the tank it turned out) and the difference was just plain fun.   I have a prop on that needs to run a little more 4-2 that I normally run.   It is running like a classic 10 o’clock- 2 o’clock break in this mode.   When it breaks into the two cycle the airplane visibly slows down though still solid out there.   It slows BEFORE I put the nose down making the backside of maneuvers a casual thing without the downward rollercoaster feeling.   Like I said- fun!

Dave

   Has anyone tried an after-muffler on this particular type?  I used one long, long ago on the 40VF but it was OK sound-wise without (albeit annoying). Everyone might want to just dismiss the issue, but, it's too loud without something.

    I didn't have one at the time (and it might not have existed), but has anyone tried the molded silicone FAI combat muffler?  That's about the right size.

     Brett

[Doug Moon]

One more follow up comment.   Yesterday I put the full wave pipe over into my Nats airplane ( ill- fated there due to a glob of solder in the tank it turned out) and the difference was just plain fun.   I have a prop on that needs to run a little more 4-2 that I normally run.   It is running like a classic 10 o’clock- 2 o’clock break in this mode.   When it breaks into the two cycle the airplane visibly slows down though still solid out there.   It slows BEFORE I put the nose down making the backside of maneuvers a casual thing without the downward rollercoaster feeling.   Like I said- fun!

Dave

This is great news! It is fun! The plane stays out there and stays in trim.

I'm curious if you're getting better fuel mileage?  I am for sure.
I have also noticed my time to set the needle is very short. I have about 15-20 seconds before it's heating up and gaining rpm. I also find it works at ONE rpm only. The range for operation is very narrow. Luckily for me the 2 props I have right now work really well at this point. Miss the needle 100 low and it's like there is nothing back there. I have figured it out now and really works well.

[Dave_Trible]

   Has anyone tried an after-muffler on this particular type?  I used one long, long ago on the 40VF but it was OK sound-wise without (albeit annoying). Everyone might want to just dismiss the issue, but, it's too loud without something.

    I didn't have one at the time (and it might not have existed), but has anyone tried the molded silicone FAI combat muffler?  That's about the right size.

     Brett

Brett my hearing isn't what it should be but I don't think it's really any louder that most the other pipes.  If anything the two baffle pipe I made seems more loud.   Maybe you could add an extra chamber aft of the convergence cone but it would make the pipe pretty long.   Since the 'hot spot' is in the cone about half way instead of the first baffle situation the whole pipe is shoved at least two inches further forward so there may be room.

[Dave_Trible]

This is great news! It is fun! The plane stays out there and stays in trim.

I'm curious if you're getting better fuel mileage?  I am for sure.
I have also noticed my time to set the needle is very short. I have about 15-20 seconds before it's heating up and gaining rpm. I also find it works at ONE rpm only. The range for operation is very narrow. Luckily for me the 2 props I have right now work really well at this point. Miss the needle 100 low and it's like there is nothing back there. I have figured it out now and really works well.

I haven't gotten far enough yet to see about the mileage.   I can tell though when I get to it.   I used this ship for the Worlds warm up flight so I know precisely what I had for fuel load.   Yesterday I was leaving more in so I could fiddle with the needle.   Now I have that set I can go back to what I used in Muncie and compare.  I did notice on both planes I had this pipe on that launch rpm for this prop (8560) had the engine running in a solid two cycle rather than four with the old pipes but within less than a lap it settled right down into a strong four.   I didn't yet try to move the needle too far from there so can't say how narrow the band-something else to learn.

[Doug Moon]

I haven't gotten far enough yet to see about the mileage.   I can tell though when I get to it.   I used this ship for the Worlds warm up flight so I know precisely what I had for fuel load.   Yesterday I was leaving more in so I could fiddle with the needle.   Now I have that set I can go back to what I used in Muncie and compare.  I did notice on both planes I had this pipe on that launch rpm for this prop (8560) had the engine running in a solid two cycle rather than four with the old pipes but within less than a lap it settled right down into a strong four.   I didn't yet try to move the needle too far from there so can't say how narrow the band-something else to learn.

8560!!??? What motor and prop?

[Brett Buck]

Brett my hearing isn't what it should be but I don't think it's really any louder that most the other pipes.  If anything the two baffle pipe I made seems more loud.   Maybe you could add an extra chamber aft of the convergence cone but it would make the pipe pretty long.   Since the 'hot spot' is in the cone about half way instead of the first baffle situation the whole pipe is shoved at least two inches further forward so there may be room.

   David has one, I had one, in both cases they were substantially louder than my baseline system (which is about the upper limit as far as noise goes and occasionally draws comment).

   Far for me to inhibit anyone's creativity and the sound is not a judged category, but for people to use it more, I think that is the problem that needs to be addressed, because there are very good, if not ideal, alternatives that are a lot quieter.

     Brett

[Lauri Malila]

.

[Doug Moon]

   David has one, I had one, in both cases they were substantially louder than my baseline system (which is about the upper limit as far as noise goes and occasionally draws comment).

   Far for me to inhibit anyone's creativity and the sound is not a judged category, but for people to use it more, I think that is the problem that needs to be addressed, because there are very good, if not ideal, alternatives that are a lot quieter.

     Brett

I flew mine as a warm up for the judges at the WCs on Saturday. It was very early not many people around. The sound was noticeably louder. But 96 db at 10'? Most likely not close. 96 DB is very loud.

I flew in a contest this past weekend. On our circle, adv and exp, there were 11 contestants and only 3 were running IC. 2 were side exhaust and then my piped rig. No one said the sound was a problem at all. I did get a few comments about it being a "growler". But that was it and nothing negative for sure. No one seemed to care. The carrier that was going on right next to use was WAY WAY louder on the high speed laps. I mean you couldn't have a conversation near the circles when they were up.   

[Matt Colan]

I flew mine as a warm up for the judges at the WCs on Saturday. It was very early not many people around. The sound was noticeably louder. But 96 db at 10'? Most likely not close. 96 DB is very loud.

I flew in a contest this past weekend. On our circle, adv and exp, there were 11 contestants and only 3 were running IC. 2 were side exhaust and then my piped rig. No one said the sound was a problem at all. I did get a few comments about it being a "growler". But that was it and nothing negative for sure. No one seemed to care. The carrier that was going on right next to use was WAY WAY louder on the high speed laps. I mean you couldn't have a conversation near the circles when they were up.   

For what this is worth…I’ve been holding this information back for fear of it going to your head Doug  . During the banquet, Mark Overmier told me he thought your loud ass pipe was quieter than the contra-rotating props the Polish were flying. However, during your warmup flight, Paul came up to us and said if it was competing that would’ve been put on the meter so quickly.

I think we need to get these pipes on a decibel meter to actually see if it’s the pitch that is so excruciating, or if they’re actually as loud as they seem to be.

[Doug Moon]

For what this is worth…I’ve been holding this information back for fear of it going to your head Doug  . During the banquet, Mark Overmier told me he thought your loud ass pipe was quieter than the contra-rotating props the Polish were flying. However, during your warmup flight, Paul came up to us and said if it was competing that would’ve been put on the meter so quickly.

I think we need to get these pipes on a decibel meter to actually see if it’s the pitch that is so excruciating, or if they’re actually as loud as they seem to be.

Yes I would love to put it on the meter. I am very curious.

You need a ride on it as well.

[Matt Colan]

Yes I would love to put it on the meter. I am very curious.

You need a ride on it as well.

Hoping for the weekend of the 15th. You need a ride on mine too

[Dave_Trible]

8560!!??? What motor and prop?

It's a RO Jett .76 on my own 12.25x 6something three blade carbon.  Any chance some of your extra noise is whatever prop you are using?  I didn't get a chance to see your warm up flight so I didn't hear it.   Wish I could have.   I am just not thinking my full wave is producing any more noise than some of the other pipes.  In some sense it's just a big expansion muffler.   I'm sure one or two are louder.  Wish I had a meter to measure.  I'm planning to use it in Tulsa.   I'll know if they run me out of town.

Dave

[frank williams]

   David has one, I had one, in both cases they were substantially louder than my baseline system (which is about the upper limit as far as noise goes and occasionally draws comment).

     Brett

"one" what ?

[Brett Buck]

"one" what ?

  One of the baffle-less pipes close to if not identical to the one you were showing.

     Brett

[Dave_Trible]

This past weekend Doug and I were both at the Tulsa contest with the only two full wave pipe airplanes flying (in the world?) back to back.   It seemed to me the performance of both pipes was about the same,  showing the same amount of braking and gaining no speed vertically.    We agreed this was the way to go.   I will admit both planes seemed to be louder than the other ships present but I don't think enough to matter to anyone on the field and still not like running them open-faced.  Doug has a PA .65 I think and I the RO Jett .76.   I'm running a Merco .61 open faced in my winter airplane and it is louder.....

Dave

[EricV]

This past weekend Doug and I were both at the Tulsa contest with the only two full wave pipe airplanes flying (in the world?) back to back.   It seemed to me the performance of both pipes was about the same,  showing the same amount of braking and gaining no speed vertically.    We agreed this was the way to go.   I will admit both planes seemed to be louder than the other ships present but I don't think enough to matter to anyone on the field and still not like running them open-faced.  Doug has a PA .65 I think and I the RO Jett .76.   I'm running a Merco .61 open faced in my winter airplane and it is louder.....

Dave

It's all relative Dave. Sensory deprivation from listening to Electrics tends to make our pipes seem louder, so, the inverse must also be true. In that case, take a flight in the morning on an unmuffled Fox 59 short shaft (work great in a Viking) and for the rest of the day, people will marvel at how quiet your full wave pipes are.
EricV

[Dan McEntee]

This past weekend Doug and I were both at the Tulsa contest with the only two full wave pipe airplanes flying (in the world?) back to back.   It seemed to me the performance of both pipes was about the same,  showing the same amount of braking and gaining no speed vertically.    We agreed this was the way to go.   I will admit both planes seemed to be louder than the other ships present but I don't think enough to matter to anyone on the field and still not like running them open-faced.  Doug has a PA .65 I think and I the RO Jett .76.   I'm running a Merco .61 open faced in my winter airplane and it is louder.....

Dave

   I forgot to ask you if you had yours installed in your airplane. I watched both rounds from the little bleacher seats by the pits, which is not very far from the circle if you remember ( maybe 25 or 30 feet?? ), and I could not really hear much difference between yours, Doug's, or any of the other piped ships. Mark launched Doug both round and from that position, he thought it was loud, but Mark does have some sensitive ears. Being right at the back of the airplane , on the concrete take off strip with the sound echoing right off of that didn't help it much.  I have a slight hearing problem on certain frequencies and certain people's voice levels and such, but on a hard, sharp sound like an exhaust note, I can still tell which is louder or not from one to another. I don't think you have much to worry about. I'm assuming that he had the PA-65 and you had the RoJett .67?? Even with the RPM difference, I couldn't tell from where I was sitting.
    Type at you later,
    Dan McEntee

[Dave_Trible]

It's all relative Dave. Sensory deprivation from listening to Electrics tends to make our pipes seem louder, so, the inverse must also be true. In that case, take a flight in the morning on an unmuffled Fox 59 short shaft (work great in a Viking) and for the rest of the day, people will marvel at how quiet your full wave pipes are.
EricV

You know with most of us at a certain age all we have to do is turn our hearing aids off..........like I do when all the grandkids come over......

Dave

[Matt Colan]

I have my full wave pipe installed on the Artemis ready to go! Same pipe as Doug’s. Frank Williams was kind enough to send it to me. Planning for flights next week to see how it goes!

[Dave_Trible]

Matt be prepared to retire your old pipes!

Dave

[Lauri Malila]

I have my full wave pipe installed on the Artemis ready to go! Same pipe as Doug’s. Frank Williams was kind enough to send it to me. Planning for flights next week to see how it goes!

Hi Matt!

So, the one in your photo, does it have any baffles in it? I've thought about putting a pipe to my next model, just haven't decided what kind of a pipe yet.
Once I know, it's time to start machining the molds. L

[Matt Colan]

Hi Matt!

So, the one in your photo, does it have any baffles in it? I've thought about putting a pipe to my next model, just haven't decided what kind of a pipe yet.
Once I know, it's time to start machining the molds. L

No baffles in this one. This is the same pipe Doug used when he warmed the judges up on the last day of the world championships.

[Matt Colan]

Finally got out today for the first flights after the WC. I tried the pipe. Like Doug and Dave, it was a huge change in how the motor ran and the airplane flew. For whatever reason, the tank shim is way off now, it was a good bit leaner on insides and richer on outsides. I also had a lot better economy as well, I think I’ll end up taking out close to 1/2oz of fuel per tank. At the WC I was taking out 3ml.

For whatever reason I can’t explain, the airplane just flew better, the state of trim was better. Then the boost and brake was a lot better as well. You could eat a pizza on the downleg of the hourglass. Then there’s the corner and and locking ability. Wow!! This was the same prop I ran at the WC, and there was a TON more corner available. It also locked a lot better as well and had perfectly flat exits. I could fly the sh*t out of the airplane and it flew great!!

This pipe isn’t coming out anytime soon! 

Edit: forgot about the noise. It’s pretty loud. I downloaded a Decibel reader on my phone and had Doug walk around the plane to see what readings we got at 10ft. In front of the prop, it read 94-95db. Behind the tail it read 88db. It’s like when Mazda ran the rotary engine at the 24 hours of LeMans and was heard for miles

[frank williams]

The “secret” of the “pipe with no baffles” is not solely the fact that it has no baffles.  The key factor is the length of the contraction cone.

The exhaust pulse traveling down the pipe is continuously sending pressure information back to the engine.  If the wave is traveling down a part of the pipe that is increasing in area, negative pressure pulses are reflected back toward the engine.  The reflection takes place for a period of time that is proportional to the length of the diverging pipe.

Likewise, when the wave-front encounters a contracting section of the pipe, a positive reflection occurs.  This reflection occurs for a length of time proportional to the length of the contracting cone.

The key point to make here is that the reflection is not a discrete event, but happens over a period of time.  The time-span of reflections are a product of the wave velocity times the length of the pipe with the area change.  A contraction cone length of 4 inches has twice the plugging pulse of a contraction cone that is 2 inches long.  (size matters).  Taking a standard baffled pipe and removing the baffles I don’t think is as good as a pipe that was designed with a significant length of contraction cone.  The “de-baffled” pipe typically will have, at best, a very acute tail cone and I don’t think will perform as well.

[Brett Buck]

The time-span of reflections are a product of the wave velocity times the length of the pipe with the area change.  A contraction cone length of 4 inches has twice the plugging pulse of a contraction cone that is 2 inches long.  (size matters).  Taking a standard baffled pipe and removing the baffles I don’t think is as good as a pipe that was designed with a significant length of contraction cone.  The “de-baffled” pipe typically will have, at best, a very acute tail cone and I don’t think will perform as well.

    I tried that and that's exactly what happens. A standard Randy/Billy pipe with the baffles removed "works", sort of, but it's way too peaky and woe be unto you if you get the RPM dragged low enough to be on a positive slope instead of a negative slope - it will rapidly drop even more speed and stabilize itself there, while getting boiling hot.

  I am dubious that anyone realized that the baffles - put there for noise reduction, as far as I can tell - are also returning closely-spaced multiple return waves that smooth out the response enough to be practical. Maybe Bobby or Dean Pappas can tells us if that was intentional or a beneficial side effect.

     Brett

[Doug Moon]

Finally got out today for the first flights after the WC. I tried the pipe. Like Doug and Dave, it was a huge change in how the motor ran and the airplane flew. For whatever reason, the tank shim is way off now, it was a good bit leaner on insides and richer on outsides. I also had a lot better economy as well, I think I’ll end up taking out close to 1/2oz of fuel per tank. At the WC I was taking out 3ml.

For whatever reason I can’t explain, the airplane just flew better, the state of trim was better. Then the boost and brake was a lot better as well. You could eat a pizza on the downleg of the hourglass. Then there’s the corner and and locking ability. Wow!! This was the same prop I ran at the WC, and there was a TON more corner available. It also locked a lot better as well and had perfectly flat exits. I could fly the sh*t out of the airplane and it flew great!!

This pipe isn’t coming out anytime soon! 

Edit: forgot about the noise. It’s pretty loud. I downloaded a Decibel reader on my phone and had Doug walk around the plane to see what readings we got at 10ft. In front of the prop, it read 94-95db. Behind the tail it read 88db. It’s like when Mazda ran the rotary engine at the 24 hours of LeMans and was heard for miles

I really should have just kept my mouth shut.    I was there watching and Matt's plane has way more corner than he had at the WC and it was way more in control speed wise across the maneuvers and especially on exit from a square bottom. My motor was also richer outside than inside BUT the outside burp on the round 8 is much more pronounced. I don't know why.

I also have way better mileage. My 65 was still breaking in when I started using this pipe. At first it was just one roll out on the pump. Now several gallons later it has settled at about 4 rounds out on the pump.

Dave's plane in Tulsa has tons of pipe action. On his down legs you could hear it shutting down and backing off. He has a really good working pipe.

A note about the noise.  We measured Matt's plane at 10' circle 94-95 db in the front, prop noise, and 88 in the back. Phillip Nickles was there and we measured his PA75 on Eather 9. At 10' on the front he was about the same 92-94 and running 88-90 at the back and sides. But his Eather pipe has such a softer tone. It's not quieter its just softer and deeper but the volume is damn near the same. Interesting....

[Matt Colan]

I really should have just kept my mouth shut.    I was there watching and Matt's plane has way more corner than he had at the WC and it was way more in control speed wise across the maneuvers and especially on exit from a square bottom. My motor was also richer outside than inside BUT the outside burp on the round 8 is much more pronounced. I don't know why.

Yeah you should have!  It’s on now!! Should’ve just kept complaining about how terrible it was

I did learn the reason my tank shim was so far off is because the tank floor broke. Got that fixed and extremely excited to try it again

[Brett Buck]

Yeah you should have!  It’s on now!! Should’ve just kept complaining about how terrible it was

I did learn the reason my tank shim was so far off is because the tank floor broke. Got that fixed and extremely excited to try it again

   Oh, Doug told you the good stuff!? Big mistake, at least David knows better than that...

     Brett

[Jake Moon]

Dang Matt, you’ll really have something once you build a plane where the tank floor, bottom block, tip weight box, and pushrod ends don’t break.

[Matt Colan]

Dang Matt, you’ll really have something once you build a plane where the tank floor, bottom block, tip weight box, and pushrod ends don’t break.

  the Salvage Title just keeps on ticking!

[Doug Moon]

   Oh, Doug told you the good stuff!? Big mistake, at least David knows better than that...

     Brett

Yeah, that wont happen again.. 

[Doug Moon]

Dang Matt, you’ll really have something once you build a plane where the tank floor, bottom block, tip weight box, and pushrod ends don’t break.

Wow that is cold blooded! Hahahahaha  Love it!

[Doug Moon]

the Salvage Title just keeps on ticking!

Yes this was totaled by insurance and the owner bought it back at a premium, and he still had to fix it.  The issues will never really go away but the result is worth it...