Return-Path: <13brv3@bellsouth.net> Received: from imf25aec.mail.bellsouth.net ([205.152.59.73] verified) by logan.com (CommuniGate Pro SMTP 4.1.3) with ESMTP id 2580155 for flyrotary@lancaironline.net; Mon, 15 Sep 2003 12:36:44 -0400 Received: from rad ([68.212.12.251]) by imf25aec.mail.bellsouth.net (InterMail vM.5.01.05.27 201-253-122-126-127-20021220) with ESMTP id <20030915163643.SUX1843.imf25aec.mail.bellsouth.net@rad> for ; Mon, 15 Sep 2003 12:36:43 -0400 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Good news, Bad news Date: Mon, 15 Sep 2003 11:36:44 -0500 Message-ID: <00c901c37ba7$8ca36820$0201a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00CA_01C37B7D.A3CD6020" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Importance: Normal In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_00CA_01C37B7D.A3CD6020 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable 1. The BUC is draggy, even worse than we thought (but doesn't really explain the lousy climb rate)=20 =20 This is a given, and the new cowl is being mentally designed as I type. = =20 2. The Warp Drive prop is never going to be an optimum high speed = stick. (but hell, you're not even to moderate speed yet) My gut feel is that = you should be running at least 17 degrees at tip. Anything less than 16 is = a waste of time unless you are resigned to flying a draggy RV-3 which I'm = sure you are not. This is assuming about a 68 - 69" prop length.=20 =20 Your gut feeling is pretty accurate. Warp originally estimated that I'd need 18 degree (3 blade, 68") for a 200 HP engine. I just got off the phone with them, and they're going to be calling back later today with = some real numbers. Off the top of his head, he said these sound a whole lot = like what the gyro guys get with their 120 HP Subaru's. Sadly, that's about what I expected to hear, but I guess the good news is that I may have identified the largest issue. The turbo's really becoming more trouble = than it's worth (Tracy, this is where you say "I told you so"). =20 =20 3. Your CG is near the fwd. limit which generates a LOT of trim drag.=20 =20 4. You may be underestimating the effect of gearleg & wheel fairings = (I think you mentioned you don't have them yet) I found that I could not = make ANY final decisions on airframe/engine performance, prop pitch or even cooling until these were in place.=20 =20 On the RV-8, the gear fairings and pants made about 12 kts difference at cruise speed, but didn't change climb performance that I could tell. =20 =20 Turbo stuff: I have no turbo experience but my best guess is that the air temp sensor should be up-wind of the turbo. Let the MAP table programming take care = of the temp rise due to adabiatic (Sp?) heating from the turbo. This = should work at low levels of boost like you are running and will eliminate the = big mixture difference between A & B controllers. With this setup in a = worst case scenario, the mixture might go too rich at high boost, a much = better thing than too lean.=20 =20 I'll have to think about this some. You're correct that it would be the safer way to go. On the 3rd gen, the temp sensor is in the intake = manifold, which is a large chunk of aluminum. Unfortunately, the sensor isn't = well isolated from the heat of the manifold itself, so it tends to read the = heat of the manifold almost as much as the air that passes through it. One almost certain way to blow up an engine is to drive your car for a while = in the winter, then park it for a few minutes. By the time you get back = in, the temp sensor is reading some really high, heat soaked temp, and will continue doing so for about the first 10 minutes of driving. The air getting to the engine is freezing cold, so when you jump on the = throttle, you get fuel to go with 150 degrees, but have 30 degree air. Boost + = lean mixture =3D new apex seals, and maybe new turbos. =20 =20 Thanks, Rusty =20 ------=_NextPart_000_00CA_01C37B7D.A3CD6020 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Message
1.  The BUC is draggy, even = worse than=20 we thought (but doesn't really explain the lousy climb = rate) 
 
This is a given, and the new cowl is being = mentally=20 designed as I type.  
 
2.  The Warp Drive prop is = never going=20 to be an optimum high speed stick.  (but hell, you're not even to = moderate=20 speed yet)  My gut feel is that you should be running at least 17 = degrees=20 at tip.  Anything less than 16 is a waste of time unless you are = resigned=20 to flying a draggy RV-3 which I'm sure you are not.  This is = assuming about=20 a 68 - 69" prop length. 
 
Your gut feeling is pretty accurate.  = Warp=20 originally estimated that I'd need 18 degree (3 blade, 68")  for a = 200 HP=20 engine.  I just got off the phone with them, and they're going = to be=20 calling back later today with some real numbers.  Off the top of = his head,=20 he said these sound a whole lot like what the gyro guys get with = their 120=20 HP Subaru's.   Sadly, that's about what I expected to hear, = but I=20 guess the good news is that I may have identified the largest = issue. =20 The turbo's really becoming more trouble than it's worth (Tracy, = this is=20 where you say "I told you so"). =20    
 
3.  Your CG is near the fwd. = limit which=20 generates a LOT of trim drag. 
 
4.  You may be = underestimating the=20 effect of gearleg  & wheel fairings (I think you mentioned you = don't=20 have them yet)   I found that I could not make ANY final = decisions on=20 airframe/engine performance, prop pitch or even cooling until these = were in=20 place. 
 
On the RV-8, the gear fairings and pants made = about 12 kts=20 difference at cruise speed, but didn't change climb = performance that I=20 could tell.   
 
Turbo stuff:
I have no turbo experience but my best = guess is=20 that the air temp sensor should be up-wind of the turbo.  Let the = MAP table=20 programming take care of the temp rise due to adabiatic (Sp?) heating = from the=20 turbo.  This should work at low levels of boost like you are = running=20 and will eliminate the big mixture difference between A & B=20 controllers.  With this setup in a worst case scenario, the mixture = might=20 go too rich at high boost,  a much better thing than too lean. 
 
I'll have to think about this some.  You're correct = that it=20 would be the safer way to go.  On the 3rd gen, the temp sensor is = in the=20 intake manifold, which is a large chunk of aluminum.  = Unfortunately,=20 the sensor isn't well isolated from the heat of the manifold itself, so = it tends=20 to read the heat of the manifold almost as much as the air that passes = through=20 it.  One almost certain way to blow up an engine is to drive=20 your car for a while in the winter, then park it for a few = minutes. =20 By the time you get back in, the temp sensor is reading some really = high, heat=20 soaked temp, and will continue doing so for about the first 10 minutes = of=20 driving.  The air getting to the engine is freezing cold, = so when=20 you jump on the throttle, you get fuel to go with 150 degrees, but have = 30=20 degree air.  Boost + lean mixture =3D new apex seals, and = maybe new=20 turbos. 
 
Thanks,
Rusty
 
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