---------------------------------------------------------- RV-List Digest Archive --- Total Messages Posted Sat 05/19/12: 8 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:31 AM - Exit Fairing (mr.gsun@gmail.com) 2. 09:37 AM - Re: Exit Fairing (Ken Cantrell) 3. 09:54 AM - Re: Exit Fairing (mr.gsun@gmail.com) 4. 10:03 AM - Re: Exit Fairing (Larry Bowen) 5. 11:58 AM - Jig Stiffeners? (Charles Brame) 6. 05:38 PM - Re: Exit Fairing (Charlie England) 7. 05:50 PM - Re: Exit Fairing (Kevin Horton) 8. 10:06 PM - Re: Exit Fairing (Reuven Silberman) ________________________________ Message 1 _____________________________________ Time: 08:31:52 AM PST US Subject: RV-List: Exit Fairing From: mr.gsun@gmail.com Hey RV posters, In my never ending quest for another ounce of velocity, I installed a cooling air exit fairing at the bottom of the firewall in my RV-7. IO-360. 4 into 2 Vetterman Exhaust pipes. The idea is to straighten the exiting cooling airflow to more closely align with the slipstream. It was one of those easy to install mods that an experienced RV builder told me about. It is a curved piece of aluminum about 4" diameter and approximately 10" long. The lower surface is in line with the bottom of the fuselage. A photo is attached. The question is: Has anyone installed this sort of thing before? Did you get the same ZERO results? Did it cause increased CHTs? My #3 continues to be too hot but I can't tell if it was affected by this mod. Haven't decided if it is worth removing it. Do not archive ________________________________ Message 2 _____________________________________ Time: 09:37:58 AM PST US From: "Ken Cantrell" Subject: RE: RV-List: Exit Fairing Hello, I finished my RV6 just over 10 years ago and this was being done by some of my builder friends at that time and I assume a long time before that. I never did add the fairing myself but thought I should have. When I saw your picture, my first thought was to copy your fairing but if you're not seeing positive results, maybe I won't waist the effort.??? Ken Cantrell Lodi, CA 1275 hrs From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of mr.gsun@gmail.com Sent: Saturday, May 19, 2012 8:30 AM Subject: RV-List: Exit Fairing Hey RV posters, In my never ending quest for another ounce of velocity, I installed a cooling air exit fairing at the bottom of the firewall in my RV-7. IO-360. 4 into 2 Vetterman Exhaust pipes. The idea is to straighten the exiting cooling airflow to more closely align with the slipstream. It was one of those easy to install mods that an experienced RV builder told me about. It is a curved piece of aluminum about 4" diameter and approximately 10" long. The lower surface is in line with the bottom of the fuselage. A photo is attached. The question is: Has anyone installed this sort of thing before? Did you get the same ZERO results? Did it cause increased CHTs? My #3 continues to be too hot but I can't tell if it was affected by this mod. Haven't decided if it is worth removing it. Do not archive ________________________________ Message 3 _____________________________________ Time: 09:54:21 AM PST US Subject: RE: RV-List: Exit Fairing From: mr.gsun@gmail.com Ken I just can't measure any results. Greg On May 19, 2012 9:46 AM, "Ken Cantrell" wrote: > Hello,**** > > ** ** > > I finished my RV6 just over 10 years ago and this was being done by some > of my builder friends at that time and I assume a long time before that. I > never did add the fairing myself but thought I should have. When I saw yo ur > picture, my first thought was to copy your fairing but if you=92re not se eing > positive results, maybe I won=92t waist the effort.???**** > > ** ** > > Ken Cantrell**** > > Lodi, CA**** > > 1275 hrs**** > > ** ** > > *From:* owner-rv-list-server@matronics.com [mailto: > owner-rv-list-server@matronics.com] *On Behalf Of *mr.gsun@gmail.com > *Sent:* Saturday, May 19, 2012 8:30 AM > *To:* rv-list@matronics.com > *Subject:* RV-List: Exit Fairing**** > > ** ** > > Hey RV posters, In my never ending quest for another ounce of velocity , > I installed a cooling air exit fairing at the bottom of the firewall in m y > RV-7. IO-360. 4 into 2 Vetterman Exhaust pipes. The idea is to > straighten the exiting cooling airflow to more closely align with the > slipstream. It was one of those easy to install mods that an experience d > RV builder told me about. > > It is a curved piece of aluminum about 4" diameter and approximately 10" > long. The lower surface is in line with the bottom of the fuselage. A > photo is attached. > > The question is: Has anyone installed this sort of thing before? Did yo u > get the same ZERO results? Did it cause increased CHTs? My #3 continues > to be too hot but I can't tell if it was affected by this mod. Haven't > decided if it is worth removing it. > > Do not archive**** > > * > =========== =========== =========== =========== > * > > ________________________________ Message 4 _____________________________________ Time: 10:03:45 AM PST US Subject: RE: RV-List: Exit Fairing From: Larry Bowen That's the same ramp that is on the RV8, per plans and prefabricated, as you probably already knew. Not sure why the 7 is different. - Larry Bowen Larry@BowenAero.com http://BowenAero.com On May 19, 2012 12:56 PM, wrote: > Ken > I just can't measure any results. > > Greg > On May 19, 2012 9:46 AM, "Ken Cantrell" wrote: > >> Hello,**** >> >> ** ** >> >> I finished my RV6 just over 10 years ago and this was being done by some >> of my builder friends at that time and I assume a long time before that. I >> never did add the fairing myself but thought I should have. When I saw y our >> picture, my first thought was to copy your fairing but if you=92re not s eeing >> positive results, maybe I won=92t waist the effort.???**** >> >> ** ** >> >> Ken Cantrell**** >> >> Lodi, CA**** >> >> 1275 hrs**** >> >> ** ** >> >> *From:* owner-rv-list-server@matronics.com [mailto: >> owner-rv-list-server@matronics.com] *On Behalf Of *mr.gsun@gmail.com >> *Sent:* Saturday, May 19, 2012 8:30 AM >> *To:* rv-list@matronics.com >> *Subject:* RV-List: Exit Fairing**** >> >> ** ** >> >> Hey RV posters, In my never ending quest for another ounce of >> velocity, I installed a cooling air exit fairing at the bottom of the >> firewall in my RV-7. IO-360. 4 into 2 Vetterman Exhaust pipes. The >> idea is to straighten the exiting cooling airflow to more closely align >> with the slipstream. It was one of those easy to install mods that an >> experienced RV builder told me about. >> >> It is a curved piece of aluminum about 4" diameter and approximately 10" >> long. The lower surface is in line with the bottom of the fuselage. A >> photo is attached. >> >> The question is: Has anyone installed this sort of thing before? Did >> you get the same ZERO results? Did it cause increased CHTs? My #3 >> continues to be too hot but I can't tell if it was affected by this mod. >> Haven't decided if it is worth removing it. >> >> Do not archive**** >> >> * >> >> t="_blank">http://www.matronics.com/Navigator?RV-List >> tp://forums.matronics.com >> _blank">http://www.matronics.com/contribution >> * >> >> * > =========== =========== =========== =========== > * > > ________________________________ Message 5 _____________________________________ Time: 11:58:54 AM PST US From: Charles Brame Subject: RV-List: Jig Stiffeners? Hey guys, Its been nearly 12 years since I built the elevators and rudder for my RV-6. I recently damaged my right elevator and need to replace the skin and stiffeners. My feeble memory seems to recall I made a small jig that greatly sped up shaping and drilling the stiffeners, but I cannot recall how the jig was made and/or how it was used. Can anybody help? Charlie Brame RV-6A N11CB San Antonio ________________________________ Message 6 _____________________________________ Time: 05:38:31 PM PST US From: Charlie England Subject: Re: RV-List: Exit Fairing On 05/19/2012 10:30 AM, mr.gsun@gmail.com wrote: > Hey RV posters, In my never ending quest for another ounce of > velocity, I installed a cooling air exit fairing at the bottom of the > firewall in my RV-7. IO-360. 4 into 2 Vetterman Exhaust pipes. > The idea is to straighten the exiting cooling airflow to more closely > align with the slipstream. It was one of those easy to install mods > that an experienced RV builder told me about. > > It is a curved piece of aluminum about 4" diameter and approximately > 10" long. The lower surface is in line with the bottom of the > fuselage. A photo is attached. > > The question is: Has anyone installed this sort of thing before? Did > you get the same ZERO results? Did it cause increased CHTs? My #3 > continues to be too hot but I can't tell if it was affected by this > mod. Haven't decided if it is worth removing it. > > Do not archive There's a very long and on-going discussion on the VAF forum about cowl exit experiments (with not much useful info). As someone else said, the firewall treatment is standard on the -8. I think that all the really fast RV's have something similar to that, or something much more elaborate (ramps that extend all the way up to the cylinders, in a lot of cases). One thing to think about in your installation is the horizontal brace on the exhaust pipes. It's round (plus the hose clamps), meaning that you've got a really draggy structure directly in the exit path. Could you run separate braces from each pipe outward, instead of across the exit? Charlie ________________________________ Message 7 _____________________________________ Time: 05:50:18 PM PST US Subject: Re: RV-List: Exit Fairing From: Kevin Horton A smooth, rounded ramp like that should lead to a decrease in CHTs, in theory. But, the devil is in the details. I can't tell from the picture, but is it possible that the bottom of that fairing extends down far enough to decrease the exit area from what it would be if the fairing was not installed? If so, it is quite possible that you have less air flowing than before, and thus may see an increase in CHTs. Normally, if there is less air flowing, there should be less cooling drag, and a speed increase. But, the decrease in air flow, with the same frontal area from the part of the cowling that is dropped down where the exhaust pipes exit, would give extra wake drag which may cancel out the decrease in cooling drag. Ideally, the rounded radius would end on a tangent to the bottom of the fuselage. If the radius keeps going so there is a sharp corner where it meets the bottom of the fuselage, there May be some flow separation behind the radius, leading to extra drag. Kevin Horton Sent from my iPad On 2012-05-19, at 11:30 AM, mr.gsun@gmail.com wrote: > Hey RV posters, In my never ending quest for another ounce of velocity, I installed a cooling air exit fairing at the bottom of the firewall in my RV-7. IO-360. 4 into 2 Vetterman Exhaust pipes. The idea is to straighten the exiting cooling airflow to more closely align with the slipstream. It was one of those easy to install mods that an experienced RV builder told me about. > > It is a curved piece of aluminum about 4" diameter and approximately 10" long. The lower surface is in line with the bottom of the fuselage. A photo is attached. > > The question is: Has anyone installed this sort of thing before? Did you get the same ZERO results? Did it cause increased CHTs? My #3 continues to be too hot but I can't tell if it was affected by this mod. Haven't decided if it is worth removing it. > > Do not archive > ________________________________ Message 8 _____________________________________ Time: 10:06:06 PM PST US From: Reuven Silberman Subject: Re: RV-List: Exit Fairing Cooling is an art, science, and black magic all rolled into one.- If your looking for efficient cooling read LoPersit or Lazlo Pazmany's stuff.- Y ou can also-Google aircraft piston engine cooling and you will get pages of stuff.=0A-=0AIf you having problems with one cyl- look from the top down between the cooling fins in and around the spark plug and top the the cyl and clean out all the casting slag.- =0A-=0AReuven Silberman-- =0A=0AEnjoy life now=0AIt has an expiration date.=0A =0A=0A________________ ________________=0A From: Kevin Horton =0ATo: "rv-list @matronics.com" =0ASent: Saturday, May 19, 2012 5:4 9 PM=0ASubject: Re: RV-List: Exit Fairing=0A =0A--> RV-List message posted by: Kevin Horton =0A=0AA smooth, rounded ramp like th at should lead to a decrease in CHTs, in theory.- But, the devil is in th e details.- I can't tell from the picture, but is it possible that the bo ttom of that fairing extends down far enough to decrease the exit area from what it would be if the fairing was not installed?- If so, it is quite p ossible that you have less air flowing than before, and thus may see an inc rease in CHTs.- Normally, if there is less air flowing, there should be l ess cooling drag, and a speed increase.- But, the decrease in air flow, w ith the same frontal area from the part of the cowling that is dropped down where the exhaust pipes exit, would give extra wake drag which may cancel out the decrease in cooling drag.=0A=0AIdeally, the rounded radius would en d on a tangent to the bottom of the fuselage.- If the radius keeps going so there is a sharp corner where it meets the bottom of the fuselage, there May be some flow separation behind the radius, leading to extra drag.=0A =0AKevin Horton=0A=0ASent from my iPad=0A=0AOn 2012-05-19, at 11:30 AM, mr. gsun@gmail.com wrote:=0A=0A> Hey RV posters,- - In my never ending ques t for another ounce of velocity, I installed a cooling air exit fairing at the bottom of the firewall in my RV-7.- - IO-360.- 4 into 2 Vetterman Exhaust pipes.- The idea is to straighten the exiting cooling airflow t o more closely align with the slipstream.- It was one of those easy to i nstall mods that an experienced RV builder told me about.=0A> =0A> It is a curved piece of aluminum about 4" diameter and approximately 10" long.- T he lower surface is in line with the bottom of the fuselage.- A photo is attached.=0A> =0A> The question is:- Has anyone installed this sort of th ing before?- Did you get the same ZERO results?- Did it cause increased CHTs?- My #3 continues to be too hot but I can't tell if it was affected by this mod.- Haven't decided if it is worth removing it.=0A> =0A> Do no = ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rv-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RV-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/rv-list Browse Digests http://www.matronics.com/digest/rv-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.