X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-m24.mx.aol.com ([64.12.137.5] verified) by logan.com (CommuniGate Pro SMTP 5.2.0) with ESMTP id 2774883 for flyrotary@lancaironline.net; Mon, 03 Mar 2008 11:03:30 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.5; envelope-from=WRJJRS@aol.com Received: from WRJJRS@aol.com by imo-m24.mx.aol.com (mail_out_v38_r9.3.) id q.c68.23c748b5 (34894) for ; Mon, 3 Mar 2008 11:02:14 -0500 (EST) Received: from WEBMAIL-DF14 (webmail-df14.webmail.aol.com [205.188.104.78]) by cia-da01.mx.aol.com (v121.4) with ESMTP id MAILCIADA013-884e47cc21051f0; Mon, 03 Mar 2008 11:02:13 -0500 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Cooling the 20B Date: Mon, 03 Mar 2008 11:02:14 -0500 X-AOL-IP: 65.161.241.3 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: wrjjrs@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CA4B5F14C3FB60_F70_10EA_WEBMAIL-DF14.sysops.aol.com" X-Mailer: AOL Webmail 34865-STANDARD Received: from 65.161.241.3 by WEBMAIL-DF14.sysops.aol.com (205.188.104.78) with HTTP (WebMailUI); Mon, 03 Mar 2008 11:02:14 -0500 Message-Id: <8CA4B5F149910B2-F70-864@WEBMAIL-DF14.sysops.aol.com> X-Spam-Flag: NO ----------MB_8CA4B5F14C3FB60_F70_10EA_WEBMAIL-DF14.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Al, You are correct on all your points of course. The rotary DOES have a sli= ghtly higher heat rejection requirement but the Oil cooler usually is what i= s handling it. I like to advise people toward the high side and then if they= duct very well they will have no problems. It agree that you can run 50% no= problem. You also have a slipperier plane than most of us. It will be inter= esting to see how Mark's ES will compare to your plane. I've always been imp= ressed with the efficiency of the canard designs. We are all re-learning abo= ut high speed duct work, sort of reverting to the end of WW2 just before the= jets took over. Ed just linked one of those old wartime reports. I have sev= eral of them and many are informative. As our GA aircraft get better and sta= rt running over 200 MPH on a regular basis we are back in that range that th= e fighters were in at the start of WW2. Of course by the end they were all w= ell over 300 with the fastest pushing 400 and that was the piston powered. I= 'm really glad that you are flying and getting such good numbers Al. I can't= wait to get=C2=A0my 20B in the air. By the way that Spal fan IS one of the=20= good ones. Do you remember what you paid for it? You may have a chaotic enou= gh exit on your plane (exhausting through the prop) that the turbulence and=20= any restriction is moot? It seems to me that the typical tractor exit=C2=A0w= ill be harder to blend with the airstream, but I may be incorrect in that th= ought.=20 Bill Jepson=C2=A0 -----Original Message----- From: Al Gietzen To: Rotary motors in aircraft Sent: Sat, 1 Mar 2008 9:43 am Subject: [FlyRotary] Cooling the 20B Bill; your point is valid, but I=E2=80=99ll take the liberty to add and clar= ify. =C2=A0 You will need to run between 75% and 100%=C2=A0 in your plane most of the ti= me! The rotary is well up to the task, but you need to concern yourself with= a totally different operation pattern. Radiator wise the rule of thumb is a= minimum of 2ci of radiator per HP for piston engines, Rotaries like closer=20= to 3 cubic inches per HP. I actually find that with the extra power of the 20B, cruising at about 50%=20= is just fine.=C2=A0 Unless you=E2=80=99re in a hurry, since speed goes up by= the cube root of power, an extra 25% + dosesn=E2=80=99t get you that much.= =C2=A0 I can fly 200 mph at 9.2 gph, or 210 mph at about 11.0 gph.=C2=A0 I t= end to think it is not worth $7 of fuel to gain 3 minutes each hour of fligh= t.=C2=A0 The numbers for a Lancair or Velocity will be different, but you ge= t my drift.=20 =C2=A0 But your right, of course; this is quite a different application than racing= .=C2=A0 The limiting factor on cooling is takeoff and climb. If you get that= done, then you=E2=80=99ll start wondering how to reduce the unnecessary coo= ling drag when cruising. =C2=A0Be really careful about fans in your plane. At the higher air speeds w= e see a fan can become a real restriction. Also not many fans, (only the REA= LLY expensive ones), are designed to be freewheeling in a 200 MPH airstream!= =20 I use an auxiliary fan behind the in-cowl radiator (which is handling most o= f the coolant heat load) in my Velocity (rear engine, of course). It=E2=80= =99s a 4-blade SPAL fan that covers about 65% of the radiator. =C2=A0With th= e fan on I can sit and wait for takeoff for long periods of time without con= cern.=C2=A0 It gets turned off when I get clearance.=C2=A0 When I installed=20= the fan, I did not notice any reduction in the cooling ability in the air, s= o I conclude that it does not restrict the airflow. The scoop inlet is about= =C2=BC the rad area, so the air exiting the rad is 50 mph or less. I haven= =E2=80=99t concerned myself about the fan spinning in flight, and it has ope= rated for about 60 hours of flying and doesn=E2=80=99t show noticeable signs= of wear.=C2=A0 Although I should perhaps rig the relay to short the fan ter= minals when turned off. The fan has a secondary function which I think is also important.=C2=A0 I tu= rn it on as I=E2=80=99m about to shutdown, and leave it running a few minute= s after shutdown. It definitely reduces the in-cowl temps while things (espe= cially the exhaust system) is cooling down. =C2=A0Good for things like the c= oils and alternator. Radiator wise the rule of thumb is a minimum of 2ci of radiator per HP for p= iston engines, Rotaries like closer to 3 cubic inches per HP. Unless I=E2=80=99m overlooking something; except for a bit lower BSFC (maybe= 10 =E2=80=93 15%) there is no reason to believe that a rotary takes any mor= e cooling capacity per hp than a piston engine. The split between oil and co= olant heat loads is quite different. The rotary puts close to 1/3 of the was= te heat into the oil, whereas a piston engine may be more like 10% or less.=20= So although the combined heat rejection requirement is a bit higher, the coo= lant side requirement (radiator) of the rotary is actually less; the oil coo= ler quite a bit more. As my installation has turned out, the airflow through the oil cooler is les= s than anticipated, and the effectiveness of the in-cowl rad greater.=C2=A0=20= I typically see oil temps 20 to 40F higher than coolant =E2=80=93 so I=E2= =80=99m about to face some re-plumbing to put in an oil/water heat exchanger= . Al ----------MB_8CA4B5F14C3FB60_F70_10EA_WEBMAIL-DF14.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="utf-8"
Al, You are correct on all your points of course. The rotary DOES have=20= a slightly higher heat rejection requirement but the Oil cooler usually is w= hat is handling it. I like to advise people toward the high side and then if= they duct very well they will have no problems. It agree that you can run 5= 0% no problem. You also have a slipperier plane than most of us. It will be=20= interesting to see how Mark's ES will compare to your plane. I've always bee= n impressed with the efficiency of the canard designs. We are all re-learnin= g about high speed duct work, sort of reverting to the end of WW2 just befor= e the jets took over. Ed just linked one of those old wartime reports. I hav= e several of them and many are informative. As our GA aircraft get better an= d start running over 200 MPH on a regular basis we are back in that range th= at the fighters were in at the start of WW2. Of course by the end they were=20= all well over 300 with the fastest pushing 400 and that was the piston power= ed. I'm really glad that you are flying and getting such good numbers Al. I=20= can't wait to get my 20B in the air. By the way that Spal fan IS one of= the good ones. Do you remember what you paid for it? You may have a chaotic= enough exit on your plane (exhausting through the prop) that the turbulence= and any restriction is moot? It seems to me that the typical tractor exit&n= bsp;will be harder to blend with the airstream, but I may be incorrect in th= at thought.
Bill Jepson 



-----Original Message-----
From: Al Gietzen <ALVentures@cox.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Sat, 1 Mar 2008 9:43 am
Subject: [FlyRotary] Cooling the 20B

Bill; your point is= valid, but I=E2=80=99ll take the liberty to add and clarify.<= /div>
 
You will need to ru= n between 75% and 100%  in your plane most of the time! The rotary is w= ell up to the task, but you need to concern yourself with a totally differen= t operation pattern. Radiator wise the rule of thumb is a minimum of 2ci of=20= radiator per HP for piston engines, Rotaries like closer to 3 cubic inches p= er HP.
I actually find tha= t with the extra power of the 20B, cruising at about 50% is just fine. = Unless you=E2=80=99re in a hurry, since speed goes up by the cube root of p= ower, an extra 25% + dosesn=E2=80=99t get you that much.  I can fly 200= mph at 9.2 gph, or 210 mph at about 11.0 gph.  I tend to think it is n= ot worth $7 of fuel to gain 3 minutes each hour of flight.  The numbers= for a Lancair or <= SPAN style=3D"FONT-SIZE: 11pt; COLOR: blue; FONT-FAMILY: Verdana">Velocity will be different, but you ge= t my drift.
 
But your right, of=20= course; this is quite a different application than racing.  The limitin= g factor on cooling is takeoff and climb. If you get that done, then you=E2= =80=99ll start wondering how to reduce the unnecessary cooling drag when cru= ising.
 Be really careful about fans in your plane. At the=20= higher air speeds we see a fan can become a real restriction. Also not many=20= fans, (only the REALLY expensive ones), are designed to be freewheeling in a= 200 MPH airstream!
I use an auxiliary=20= fan behind the in-cowl radiator (which is handling most of the coolant heat=20= load) in my Velocity<= /FONT> (rear engine, of course). It=E2=80= =99s a 4-blade SPAL fan that covers about 65% of the radiator.  With th= e fan on I can sit and wait for takeoff for long periods of time without con= cern.  It gets turned off when I get clearance.  When I installed=20= the fan, I did not notice any reduction in the cooling ability in the air, s= o I conclude that it does not restrict the airflow. The scoop inlet is about= =C2=BC the rad area, so the air exiting the rad is 50 mph or less. I haven= =E2=80=99t concerned myself about the fan spinning in flight, and it has ope= rated for about 60 hours of flying and doesn=E2=80=99t show noticeable signs= of wear.  Although I should perhaps rig the relay to short the fan ter= minals when turned off.
The fan has a secon= dary function which I think is also important.  I turn it on as I=E2= =80=99m about to shutdown, and leave it running a few minutes after shutdown= . It definitely reduces the in-cowl temps while things (especially the exhau= st system) is cooling down.  Good for things like the coils and alterna= tor.
Radiator wise the rule of thumb is a minimum of 2= ci of radiator per HP for piston engines, Rotaries like closer to 3 cubic in= ches per HP.
Unless I=E2=80=99m=20= overlooking something; except for a bit lower BSFC (maybe 10 =E2=80=93 15%)=20= there is no reason to believe that a rotary takes any more cooling capacity=20= per hp than a piston engine. The split between oil and coolant heat loads is= quite different. The rotary puts close to 1/3 of the waste heat into the oi= l, whereas a piston engine may be more like 10% or less. So although the com= bined heat rejection requirement is a bit higher, the coolant side requireme= nt (radiator) of the rotary is actually less; the oil cooler quite a bit mor= e.
As my installation=20= has turned out, the airflow through the oil cooler is less than anticipated,= and the effectiveness of the in-cowl rad greater.  I typically see oil= temps 20 to 40F higher than coolant =E2=80=93 so I=E2=80=99m about to face=20= some re-plumbing to put in an oil/water heat exchanger.
Al
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