X-Junk-Score: 0 [] X-Cloudmark-Score: 0 [] X-Cloudmark-Analysis: v=2.3 cv=PbaBeRpd c=1 sm=1 tr=0 a=c2S5A7n/ooz/KAakJUltow==:117 a=x7bEGLp0ZPQA:10 a=K7ySfSCCDxUA:10 a=_RQrkK6FrEwA:10 a=K9YiWmrbAAAA:8 a=W-IJHtK-AAAA:8 a=5lucXWJGAAAA:8 a=UKPAHat8AAAA:8 a=Ia-xEzejAAAA:8 a=xPyZ54XvAAAA:8 a=pGLkceISAAAA:8 a=jV3BzgDzAAAA:8 a=o1OHuDzbAAAA:8 a=jThZ7_-JAAAA:8 a=7g1VtSJxAAAA:8 a=zAN3-NYJ1Yu1bs-oh3AA:9 a=DTWYOVXiwN-4Kdc_:21 a=X2GpJCHQHppALweq:21 a=QEXdDO2ut3YA:10 a=KGhxpC5zL1cA:10 a=Qa1je4BO31QA:10 a=lbVkQV85mo0A:10 a=F6a2BMeBdsAA:10 a=gvSQh4r-fQ0A:10 a=S0wkRrzPavQA:10 a=m2OGfQcOE2RhorMbiocA:9 a=7NOAyDjiS2OZzmxt:21 a=Oe_8RonmPgQ48LnW:21 a=AC04EjlwvtUTgEnX:21 a=4fN42X7Z35HiWFx1RDDL:22 a=PjCiafSWRo16AjQHjZXP:22 a=tjNemD4wtFR24VrVMQME:22 a=Fc6xXSS-RxGHxrvp76Qp:22 a=Urk15JJjZg1Xo0ryW_k8:22 a=LQCduUwlY3eUW_MavTj7:22 a=9Uz93n4haClHrRxSevy5:22 a=5YQ6H4ZxyGn-KoBYtt8s:22 a=NVbvhy2gKIdozzgvQOKv:22 a=grOzbf7U_OpcSX4AJOnl:22 From: "Matt Boiteau mattboiteau@gmail.com" Received: from mail-ej1-f42.google.com ([209.85.218.42] verified) by logan.com (CommuniGate Pro SMTP 6.2.14) with ESMTPS id 507064 for flyrotary@lancaironline.net; Wed, 08 Jul 2020 20:10:06 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.218.42; envelope-from=mattboiteau@gmail.com Received: by mail-ej1-f42.google.com with SMTP id p20so299541ejd.13 for ; Wed, 08 Jul 2020 17:10:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=UFx9LM/ITqScAwDecOTe2WysgCdbPzNxQLs8tIdxqx0=; b=Dte772PL2tNytHDdarbMRas/HpZffpyF6hHiPLoG2XjVAxlGBdt/kp4uKKNnEhkbWD fo39VBgKNuadjH3+UGHIAQWC9uqS1uI6Y5P5+f+ksIPt5TYWhFn7TZN4+bG8kVnaZjjW exnMoxBYguVqO94ccZEv0u5KYe0vckTLqzeCvo5tkkaeJd6VgmbPdXDySdXQmrDCAkNH XczeMaq3XcHu/IQn3EIcQLAraHK1SDtpGLuIjva7K0ML6RXo+LeDi9eVYZpKm6NJrUin QohrLwOVF+6nTM4KPngD/ynYjhWKngeV/EEqBfvfkgdQnfZxXtfNgIxvLHt7+w3X/1Np E/2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to; bh=UFx9LM/ITqScAwDecOTe2WysgCdbPzNxQLs8tIdxqx0=; b=YIekJpM0m/Xv9IjARZdBNZvH3VaJ21l4fpJwPtaLEzjibxmnlaXnwl199jIi8oFayV NkSXPa0EavyZiHt+lxc5cusJc0cPU+0tzo7/lszGFoAr67oTLAHSG/p9bKcAm4mTburW JKHrMBw8XpSpR2DHna86x7TbmYAIHQ+MuG9Ps+xMJifnJkerJPS02+JOeRX+buIuobRh 3DCMyiCHaajoBcYb9H8R6N7WQMJi+dnJZTRc1ksrMpeBZIEMlMN9w3WwX/Id3pV9jjpY BZ+1wvuJEn/KEuOWtbC+Ay0o5SDQK+BeOQXcfghYAKj1jqMkxXpH+93a77xa25IsWCln 8j0g== X-Gm-Message-State: AOAM5322tNyClLSuSg4aaBmCvu/bnwDqtfXmyKkYGND+wumpvVOGYY4c nkXsVy3zTl54QywAeMIGSuGs1WuBLN63LfGs1nnyS0vfJdc= X-Google-Smtp-Source: ABdhPJxrY3lrW0SJSWdeYbt+Jqb+cI4S135Ebd/03/9tWHZuLh9QKJEIOYmTePeCk86BRVerLB40OrIaCW0RGDEpVD8= X-Received: by 2002:a17:906:a242:: with SMTP id bi2mr48679685ejb.243.1594253388930; Wed, 08 Jul 2020 17:09:48 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: Date: Wed, 8 Jul 2020 20:09:37 -0400 Message-ID: Subject: Re: [FlyRotary] Re: Mufflers To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary="000000000000ede2ad05a9f70a91" --000000000000ede2ad05a9f70a91 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sadly, by the time the welder and I finished, I only got about 2 hours on the plane before I had to pack up my winter trip. I was planning to go back in March to FL (I live in Canada) to start flying off the 25 hours, but you know how that all went. So I'm just sitting here waiting for the borders to open up and fly my plane! Early conclusion is it worked pretty darn good. I'd say I'm equivalent to an IO-360, maybe a tad quieter. Also on ground testing only, I quickly mocked up a long tube under the plane with holes drilled in it (with the end capped off), and it pretty much got rid of all the engine noise, only prop noise. Haven't flown with that yet. One thing I still want to do is test the backpressure. Making sure the CAN has enough holes inside. The best price I found on 321 was from ProFabrication. I went with 2.75" 20ga (0.035") on the downpipe & outlet. https://www.profabrication.com/index.php/products/straight-tubing/321-stain= less-steel.html I did use SPD Exhaust for the double slip joints at the primaries and downpipe. 2" 16ga (0.06") http://www.spdexhaust.com/pdfs/22-23_Tubing.pdf For the CAN, McMasterCarr 24"x24" 18ga (0.05") rolled into I think a 5 or 5.5" can. You can go heavier ga, I just guessed. https://www.mcmaster.com/1754T51/ - Matt Boiteau On Wed, Jul 8, 2020 at 2:35 PM Bobby J. Hughes bhughes@qnsi.net < flyrotary@lancaironline.net> wrote: > I=E2=80=99m at the exhaust header stage in my S21 FWF build. I=E2=80=99m = considering a > traditional header, 3-1 merge collector with 1.75=E2=80=9D primaries to = a 2.5=E2=80=9D > tube. I=E2=80=99m trying to be very weight conscious and looking for poss= ible > alternatives. The CA manifold can likely be built for nearly the same > weight as the header design in the picture. I=E2=80=99m a little concerne= d with the > tangential design. Mark S. built and tested one on his 20B. It ran hot an= d > caused the outer water jacket seals to fail. Mark was not running a > wideband so he couldn=E2=80=99t see a clear relationship between F/A and = EGT=E2=80=99s. He > may have be running at or near peak EGT=E2=80=99s. EGT=E2=80=99s for the = renesis can be > kept to between 1500F -1600F with a little extra or a little less fuel. I > will like install the coolant radiator on the belly so adding an external > muffler would keep it off centerline. > > > > I have located some reasonable priced Inconel 625 0.040 sheets. If rolled > into a 5-6=E2=80=9D tube, would this thickness be sufficient for a muffle= r shell or > the CA / tangential manifold tube? > > > > Matt, > > > > How is your CA header holding up? > > > > Thanks, > > > > Bobby > > > > *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] > *Sent:* Saturday, January 25, 2020 7:53 PM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: Mufflers > > > > Okay so after 2 full days of having our welder out, finally brought the > CAD design to life. Except both days were all nighters, so I was too tire= d > and busy to take 'in progerss' pictures. Was tricky to build, which made > the hourly welding cost sky high, more then the engine itself. Hopefully > that means I can save money in the future on hearing aids. > > Thanks Charlie for the tip on the spectrum analyzer. I didn't get any > before numbers, but it's all low Hz now. That harsh high pitch is gone. > Db's are still there, but I'd say with just the muffler design, it's > comparable to typical lycoming. I can start to hear the prop noise over t= he > engine noise. I measured back pressure around 3.5psi @ 2200rpm prop. > > I ran out of time to flight test the long pipe under the airplane. I > quickly held it up with my hands and the exhaust pretty much disappeared > with the prop taking over the noise. Before flying, I want to add > backpressure gauge to that part and drill holes to find a balance between > backpressure and noise. > > > > SO the "header" muffler should make quite like any other plane, and the > "under belly" pipe will make you standout in silence. > > > > Since this email type newsletter is from the dinosaur ages, I'll add > pictures and video to > https://www.homebuiltairplanes.com/forums/threads/exhaust-within-subcowl.= 30848/page-2#post-512762 > > > > - Matt Boiteau > > On 2020-01-18 5:29:51 PM, Matt Boiteau wrote: > > Have started on the exhaust. Made all three primaries 2" double slip > joints (that alone took almost a whole day with welder). The big can (CA > - Centrifugal Accumulator) rolled into a 5" can and we'll secure it to th= e > engine with straps. > > The inside pipe is 2.75" which has an area of 5.94sq". I'm not sure if > there's a magic number, but all the holes I drilled equaled to just under > double the area (11sq"). Most are 3/8, but I did add some 1/2 to get the > total area up. Could we get away with drilling less holes? Not sure. I'll > be able to drill out one side end of the CA and pull out the inner tube a= nd > change out. Will experiment later with less holes and monitor back > pressure. Will weld a npt bung on the CA and use the wideband bung to > measure the different. > > The previous exhaust with just an Aero Turbine 2525XL, measured ~113dBA. > With nothing, was closer to 120dBA. Funny around 2000 prop rpm was louder > then at 2300 full static. > > > > - Matt Boiteau > > On 2020-01-07 12:19:23 AM, Matt Boiteau mattboiteau@gmail.com < > flyrotary@lancaironline.net> wrote: > > Okay I'll make all 3 primary tubes (2" diameter) all double slip fit. > Welding batwing tabs (picture below) on to either side on the slips, will > hold the muffler to the header but allow expansion. > > > > Having troubles finding 2.75" bends in 321, so I might have to just switc= h > to 3" downpipe that is more common. Vband clamp before downpipe for easie= r > removal and under the plane to allow adding additional exhaust setups (lo= ng > pipe with holes drilled in it, fishmouth tailpipe, etc) > > > I found a company that makes flex bellows in 321. I'm just not sure if I > should have it vertical on the downpipe or close to the muffler horizonta= l > before the first 90degree bend downwards. > > https://www.aceraceparts.com/products/3-000-flex-bellow-assembly-321-stai= nless?variant=3D11067135556 > > > > > > Batwing tabs > > > > - Matt Boiteau > > On 2020-01-03 4:22:18 PM, Neil Unger 12348ung@gmail.com < > flyrotary@lancaironline.net> wrote: > > Mat, > > As usual I have no idea. I made all 3 slip joints and > to date no grief in that area. I am coming around to the stock manifold = in > some way. Yes it is heavy, but appears to muffle the noise as well. Kno= w > of 2 installations that use the stock manifold with a simple muffler afte= r > and both claim "acceptable" noise. It appears that the stock manifold has= a > big influence on noise?? Would prefer a DB reading, but if not available > it is what it is. All is compromise, weight, cost, time, but at the end = of > the day it has to work. > > Still working on the turbo even though the world is on holidays. All to > save my hearing. So far the rotary is definitely "unique" as far as a > turbo is concerned. The heat generated exceeds all else. Two things to > date -- special exhaust wheel and water cooled bearing body =3D, all for > heat. Have modified the stock front plate on the renesis to take an > electric water pump. That is the simple bit. > > Neil. > > On 1/4/2020 5:37 AM, Matt Boiteau mattboiteau@gmail.com wrote: > > okay I found a good company called SPD Exhaust. They have everything you > need in 321ss. > > With the engine being an RX8, we have three exhaust ports. Should I weld > the front and back solid to the muffler, and make the middle one a slip f= it > for expansion? Or vice-vesa? > > > > - Matt Boiteau > > On 2019-12-28 11:03:42 AM, Finn Lassen finn.lassen@verizon.net > wrote: > > I did something similar with my RV-3 13B decades ago. It split open at th= e > welds around one of the pipes from the manifold into the the big outer > tube. True, it did use individual manifold base plates, not the connected > factory manifold and the big tube was only 0.035. > > Still, I would recommend slip joints on two of the three pipes, like I > added on one of the pipes (cut through and a surrounding bigger pipe -- > missing in picture). > > > > Can't remember why I went from the above to individual runners into a > perforated pipe under the fuselage. Probably got lured by promise of > increased power by tuned lengths and still uncomfortable by the muffler > being inside the cowling. > > Finn > > On 12/28/2019 12:10 AM, Matt Boiteau mattboiteau@gmail.com wrote: > > This is what I'm going to try in a few weeks. > > "*Exhaust valve opens and a pulse of hot gas puffs out through a short > pipe, then **tangentially** into a cylindrical canister. Being > tangential, the pulse flattens out and travels **helically** (rather than > bouncing and reverberating around) along the inside curved wall of the ca= n, > spiraling toward the exit, where it comes out more uniform in flow and so > pretty quiet."* > > > > Outer pipe =3D 321 ss 0.050 thick. Flat plate bent to a 5" tube > > Inner pipe =3D 321 ss 0.036 thick. 2.5" diameter > > (I might use 302ss 0.065 since I already have it) > > > > From my understanding, the area of the holes should be double the area of > the inner pipe. > > > > - Matt Boiteau > > > > > > *Disclaimer* > > The information contained in this communication from the sender is > confidential. It is intended solely for use by the recipient and others > authorized to receive it. If you are not the recipient, you are hereby > notified that any disclosure, copying, distribution or taking action in > relation of the contents of this information is strictly prohibited and m= ay > be unlawful. > > This email has been scanned for viruses and malware, and may have been > automatically archived by *Mimecast Ltd*, an innovator in Software as a > Service (SaaS) for business. Providing a *safer* and *more useful* place > for your human generated data. Specializing in; Security, archiving and > compliance. To find out more Click Here > . > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html > --000000000000ede2ad05a9f70a91 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Sadly, by the time the welder and I finished, I only got a= bout 2 hours on the plane before I had to pack up my winter trip. I was pla= nning to go back in March to FL (I live in Canada) to start flying off the = 25 hours, but you know how that all went. So I'm just sitting here wait= ing for the borders to open up and fly my plane!

Early conclusion is= it worked pretty darn good. I'd say I'm equivalent=C2=A0to an IO-3= 60, maybe a tad quieter. Also on ground testing only, I quickly mocked up a= long tube under the plane with holes drilled in it (with the end capped of= f), and it pretty much got rid of all the engine noise, only prop noise. Ha= ven't flown with that yet. One thing I still want to do is test the bac= kpressure. Making sure the CAN has enough holes inside.

The best pri= ce I found on 321 was from ProFabrication. I went with 2.75" 20ga (0.0= 35") on the downpipe & outlet.
http= s://www.profabrication.com/index.php/products/straight-tubing/321-stainless= -steel.html

I did use SPD Exhaust for the double slip joints at = the primaries and downpipe. 2" 16ga (0.06")
http://www.spdexhaust.com/pdfs/22= -23_Tubing.pdf=C2=A0=C2=A0

For the CAN, McMasterCarr 24"x24= " 18ga (0.05") rolled into I think a 5 or 5.5" can. You can = go heavier ga, I just guessed.=C2=A0
https://www.mcmaster.com/1754T51/=C2=A0=C2=A0

- Matt Boiteau


On Wed, Jul 8, 2020 at 2:35 PM Bobby J. Hughe= s bhughes@qnsi.net <flyrotary@lancaironline.net> wrot= e:

I=E2=80=99m at the exhaust header stage in my S21 FWF bu= ild. I=E2=80=99m considering a traditional header, =C2=A03-1 merge collecto= r with 1.75=E2=80=9D primaries to a 2.5=E2=80=9D tube. I=E2=80=99m trying t= o be very weight conscious and looking for possible alternatives. The CA ma= nifold can likely be built for nearly the same weight as the header design = in the picture. I=E2=80=99m a little concerned with the tangential design. = Mark S. built and tested one on his 20B. It ran hot and caused the outer wa= ter jacket seals to fail. Mark was not running a wideband so he couldn=E2= =80=99t see a clear relationship between F/A and EGT=E2=80=99s.=C2=A0 He ma= y have be running at or near peak EGT=E2=80=99s. EGT=E2=80=99s for the rene= sis can be kept to between 1500F -1600F with a little extra or a little les= s fuel. I will like install the coolant radiator on the belly so adding an = external muffler would keep it off centerline.

=C2=A0

I have located some reasonable priced Inconel 625 0.040 shee= ts. If rolled into a 5-6=E2=80=9D tube, would this thickness be sufficient = for a muffler shell or the CA / tangential manifold tube?

=C2=A0

Matt,

=C2=A0

Ho= w is your CA header holding up?

=C2=A0

T= hanks,

=C2=A0=

Bobby=

=C2=A0

<= span style=3D"font-size:10pt;font-family:Tahoma,sans-serif">From: Rotary motor= s in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Saturday, Jan= uary 25, 2020 7:53 PM
To: Rotary motors in aircraft
Subject= : [FlyRotary] Re: Mufflers

=C2=A0

Okay so after 2 full days of= having our welder out, finally brought the CAD design to life. Except both= days were all nighters, so I was too tired and busy to take 'in proger= ss' pictures. Was tricky to build, which made the hourly welding cost s= ky high, more then the engine itself. Hopefully that means I can save money= in the future on hearing aids.

Thanks Charlie for the tip on the=C2= =A0spectrum analyzer. I didn't get any before numbers, but it's all= low Hz now. That harsh high pitch is gone. Db's are still there, but I= 'd say with just the muffler design, it's comparable to=C2=A0typica= l=C2=A0lycoming. I can start to hear the prop noise over the engine noise. = I measured back pressure around 3.5psi @ 2200rpm prop.

I ran out of = time to flight test the long pipe under the airplane. I quickly held it up = with my hands and the exhaust pretty much disappeared with the prop taking = over the noise. Before flying, I want to add backpressure gauge to that par= t and drill holes to find a balance between backpressure and noise.<= u>

=C2=A0

SO the "header" muffler should make = quite like any other plane, and the "under belly" pipe will make = you standout in=C2=A0silence.

=C2=A0

S= ince this email type newsletter is from the=C2=A0dinosaur=C2=A0ages, I'= ll add pictures and video=C2=A0to=C2=A0https://www.homebuiltairplanes.co= m/forums/threads/exhaust-within-subcowl.30848/page-2#post-512762=

=C2=A0

- Matt Boiteau

=

On 2020-01-18 5:29:51 PM, Matt Boiteau <mattboiteau@gmail.com> wrote:<= /u>

Have started on the exhaust. Made all three prim= aries 2" double slip joints (that alone took almost a whole day with w= elder). The big can (CA -=C2=A0Centrifugal Accumulator) rolled into a 5&quo= t; can and we'll secure it to the engine with straps.

The inside= pipe is 2.75" which has an area of 5.94sq". I'm not sure if = there's a magic number, but all the holes I drilled equaled to just und= er double the area (11sq"). Most are 3/8, but I did add some 1/2 to ge= t the total area up.=C2=A0Could we get away with drilling less holes? Not s= ure. I'll be able to drill out one side end of the CA and pull out the = inner tube and change out. Will=C2=A0experiment=C2=A0later=C2=A0with less h= oles and monitor back pressure. Will weld a npt bung on the CA and use the = wideband bung to measure the different.

The previous exhaust with ju= st an=C2=A0Aero Turbine 2525XL, measured ~113dBA. With nothing, was closer = to 120dBA. Funny around 2000 prop rpm was louder then at 2300 full static.= =C2=A0

=C2=A0

- Matt= Boiteau

On 2020-01-07 12:19:23 AM, Matt Boiteau <= a href=3D"mailto:mattboiteau@gmail.com" target=3D"_blank">mattboiteau@gmail= .com <flyrotary@lancaironline.net> wrote:

=

Okay I'll make all 3 primary tubes (2" diameter) all = double slip fit. Welding=C2=A0batwing=C2=A0tabs (picture below) on to eithe= r side on the slips, will hold the muffler to the header but allow expansio= n.

=C2=A0<= /u>

Having troubles finding 2.75&q= uot; bends in 321, so I might have to just switch to 3" downpipe that = is more common. Vband clamp before downpipe for easier removal and under th= e plane to allow adding additional exhaust setups (long pipe with holes dri= lled in it, fishmouth tailpipe, etc)


I found a company that makes flex bellows in 321. I= 9;m just not sure if I should have it vertical on the downpipe or close to = the muffler horizontal before the first 90degree bend downwards.
https://www.aceraceparts.c= om/products/3-000-flex-bellow-assembly-321-stainless?variant=3D11067135556<= /a>

=

Batwing tabs

On 2020-01-03 4:22:= 18 PM, Neil Unger 1= 2348ung@gmail.com <flyrotary@lancaironline.net> wrote:

Mat,

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 As us= ual I have no idea.=C2=A0 I made all 3 slip joints and to date no grief in = that area.=C2=A0 I am coming around to the stock manifold in some way.=C2= =A0 Yes it is heavy, but appears to muffle the noise as well.=C2=A0 Know of= 2 installations that use the stock manifold with a simple muffler after an= d both claim "acceptable" noise. It appears that the stock manifo= ld has a big influence on noise??=C2=A0 Would prefer a DB reading, but if n= ot available it is what it is.=C2=A0 All is compromise, weight, cost, time,= but at the end of the day it has to work.=C2=A0

<= p>S= till working on the turbo even though the world is on holidays.=C2=A0 All t= o save my hearing.=C2=A0 So far the rotary is definitely "unique"= as far as a turbo is concerned.=C2=A0 The heat generated exceeds all else.= =C2=A0 Two things to date -- special exhaust wheel and water cooled bearing= body =3D, all for heat.=C2=A0 Have modified the stock front plate on the r= enesis to take an electric water pump.=C2=A0 That is the simple bit.=

Neil.

On= 1/4/2020 5:37 AM, Matt Boiteau mattboiteau@gmail.com wrote:

=

okay I found a good company called SPD Exhaust. They have everythin= g you need in 321ss.

With the engine being an RX8, we have three exh= aust ports. Should I weld the front and back solid to the muffler, and make= the middle one a slip fit for expansion? Or vice-vesa?

=C2=A0

- Matt Boiteau

On 2019-12-28 11:03:42 AM, Finn Lassen finn.lassen@verizon.net <fly= rotary@lancaironline.net> wrote:

<= p class=3D"MsoNormal">I did something similar with my RV-3 13B decades ago. It= split open at the welds around one of the pipes from the manifold into the= the big outer tube. True, it did use individual manifold base plates, not = the connected factory manifold and the big tube was only 0.035.

Stil= l, I would recommend slip joints on two of the three pipes, like I added on= one of the pipes (cut through and a surrounding bigger pipe -- missing in = picture).



Can't remember why I went fr= om the above to individual runners into a perforated pipe under the fuselag= e. Probably got lured by promise of increased power by tuned lengths and st= ill uncomfortable by the muffler being inside the cowling.

Finn
<= br>On 12/28/2019 12:10 AM, Matt Boiteau mattboiteau@gmail.com wrote:

This is what I'm going to try in a few week= s.=C2=A0

"<= i>Exhaust valve opens and a pulse of hot gas puffs ou= t through a short pipe, then=C2=A0tangentially<= /span>=C2=A0into a cylindrical canister. Being= tangential, the pulse flattens out and travels=C2=A0helically=C2= =A0(rather than bouncing and reverberating around) along the inside curved = wall of the can, spiraling toward the exit, where it comes out more uniform= in flow and so pretty quiet."

=C2=A0

Outer pipe =3D 321 ss 0.050 thick. Flat plate bent to a 5" tube

Inner pipe =3D 321 ss= 0.036 thick. 2.5" diameter

(I might use 302ss 0.065 since I already have it)

=C2=A0=

From my understanding, the area of the h= oles should be double the area of the inner pipe.=C2=A0

=C2=A0

- Matt Boiteau

<= /div>

=C2=A0

<= /blockquote>


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