X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from access.aic-fl.com ([204.49.76.2] verified) by logan.com (CommuniGate Pro SMTP 5.1c.2) with ESMTP id 1311323 for flyrotary@lancaironline.net; Sun, 06 Aug 2006 22:52:43 -0400 Received-SPF: none receiver=logan.com; client-ip=204.49.76.2; envelope-from=unicorn@gdsys.net Received: from b9k4u9 (unverified [204.49.76.36]) by access.aic-fl.com (Rockliffe SMTPRA 4.5.6) with SMTP id for ; Sun, 6 Aug 2006 21:49:49 -0500 Message-ID: <002501c6b9de$c4c30030$514c31cc@b9k4u9> From: "Richard Sohn" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] First flight - late comer Date: Sun, 6 Aug 2006 22:02:12 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0022_01C6B9A3.F837C490" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2869 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 This is a multi-part message in MIME format. ------=_NextPart_000_0022_01C6B9A3.F837C490 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Sunday, August 06, 2006 6:45 PM Subject: [FlyRotary] First flight - Oil temp Thanks everyone for the congratulatory messages, and for the support = that is always so helpful. No pics to post yet because my camera = battery went dead after the first three shots, so I'm awaiting for shots = from my friend who took hundreds (OK, only about 150) and will be = editing for a while J. The principal issue of the day was the higher than comfortable oil = temperature; most likely due to insufficient air flow through the = cooler. For anyone who would like to think aerodynamics for awhile and = give an opinion on the simplest and best approach to remedy; read on. The custom cooler for this 265 hp engine is large. The core here is = about 5 =BC" wide, 22" long and 3 =BC" thick. It is located in the wing = root of the Velocity, behind the spar, with inlet underneath and exit on = the top. Alan Shaw, who I believe pioneered this approach, found the = location worked very well. When I discussed the installation with him = years ago, he opined that a scoop under the wing was probably not = necessary because of a pressure differential between bottom and top = surfaces. Since then, my investigations of pressure distributions, and = similar installations that aren't working so well, make me wonder. Photo 1 is a view under the wing showing the OC air intake, wheel = well, and the big armpit scoop for the coolant radiator in the cowl. = The inlet opening is about 1 1/8" wide and 23" long. There really isn't = a scoop, just an opening with an extended airfoil shaped lip which = extends about =BD" into the free stream. The idea was to minimize drag, = and assume a more negative pressure at the exit would produce the = necessary flow. Photo 2 shows a front view where you see the wheel well = and the inlet - very little extension into the free stream. Analysis = suggests that the turbulent boundary layer on a smooth surface at the = inlet location could be about 5/8 - 3/4" in thick. The air exit fairing is shown in photo 3; and is shaped as it is to = maintain attached flow and cause minimal turbulence going aft. The = effective exit area is about 1.6 times the inlet area. The thickness of = the core suggests the need for pretty good pressure differential for = adequate flow. Here are some options: a) For the first flight the landing gear was never retracted. Since = the open wheel well forward of the inlet would likely cause significant = turbulence; try another flight with the gear retracted to see if that = improves the results. b) Place some VGs forward of the inlet to 'energize' the boundary = layer, and see if that helps. c) Extend the 'lip' of the inlet to form a proper ram scoop, = possible also with VGs forward to break up the boundary layer, and = accept the slight increase in drag. d) Do something at the exit ( local 'expert' suggests there may be = flow separation before the aft end of the fairing causing high pressure = behind the exit). Put VGs on the top of the exit fairing and/or reduce = exit area. e) None of the above. I suspect the normal aerodynamic pressure differential between the = inlet and outlet points is minimal; especially in level flight where it = could be near zero. Option c) seems the most sure-fire to me. Thanks for input. Al Al, it is fantastic getting your machine into the air with such minor = things to fix. When I had my SOOB in the AVID inspected, it took me four = month until the first flight. All because of cooling issues.=20 I think your conclusion about the missing ram air at the intake is the = major reason why the oil cooling did not improve at higher air speed. A = second point may be the air outlet. It looks like a turbulence could = form where the back scoop protrudes from the wing surface. This = turbulence could produce vorticies over the edge at the outlet, reducing = the effective area of the outlet. A more continous transition from the = wing surface to the scoop surface would reduce the possibility of this = to happen. = =20 FWIW =20 You will enjoy every bit of this machine soon! Richard Sohn N-2071U = =20 -------------------------------------------------------------------------= ----- -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ ------=_NextPart_000_0022_01C6B9A3.F837C490 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Sunday, August 06, 2006 = 6:45=20 PM
Subject: [FlyRotary] First = flight - Oil=20 temp

Thanks everyone for = the=20 congratulatory messages, and for the support that is always so = helpful. =20 No pics to post yet because my camera battery went dead after the = first three=20 shots, so I=92m awaiting for shots from my friend who took hundreds = (OK, only=20 about 150) and will be editing for a while J.

 

The principal issue of = the day=20 was the higher than comfortable oil temperature; most likely due to=20 insufficient air flow through the cooler.  For anyone who would = like to=20 think aerodynamics for awhile and give an opinion on the simplest and = best=20 approach to remedy; read on.

 

The custom cooler for = this 265=20 hp engine is large.  The core here is about 5 =BC=94 wide, 22=94 = long and 3 =BC=94=20 thick. It is located in the wing root of the Velocity, behind the = spar, with=20 inlet underneath and exit on the top.  Alan Shaw, who I believe = pioneered=20 this approach, found the location worked very well.  When I = discussed the=20 installation with him years ago, he opined that a scoop under the wing = was=20 probably not necessary because of a pressure differential between = bottom and=20 top surfaces.  Since then, my investigations of pressure = distributions,=20 and similar installations that aren=92t working so well, make me=20 wonder.

 

Photo 1 is a view = under the wing=20 showing the OC air intake, wheel well, and the big armpit scoop for = the=20 coolant radiator in the cowl.  The inlet opening is about 1 = 1/8=94 wide and=20 23=94 long.  There really isn=92t a scoop, just an opening with = an extended=20 airfoil shaped lip which extends about =BD=94 into the free = stream.  The idea=20 was to minimize drag, and assume a more negative pressure at the exit = would=20 produce the necessary flow.  Photo 2 shows a front view where you = see the=20 wheel well and the inlet =96 very little extension into the free = stream. =20 Analysis suggests that the turbulent boundary layer on a smooth = surface at the=20 inlet location could be about 5/8 =96 3/4=94 in = thick.

 

The air exit fairing = is shown in=20 photo 3; and is shaped as it is to maintain attached flow and cause = minimal=20 turbulence going aft.  The effective exit area is about 1.6 times = the=20 inlet area.  The thickness of the core suggests the need for = pretty good=20 pressure differential for adequate flow.

 

Here are some=20 options:

a)  For the first = flight=20 the landing gear was never retracted. Since the open wheel well = forward of the=20 inlet would likely cause significant turbulence; try another flight = with the=20 gear retracted to see if that improves the results.

b)    = Place=20 some VGs forward of the inlet to =91energize=92 the boundary layer, = and see if=20 that helps.

 

c)    =20 Extend the =91lip=92 = of the inlet to=20 form a proper ram scoop, possible also with VGs forward to break up = the=20 boundary layer, and accept the slight increase in = drag.

 

d)    = Do=20 something at the exit ( local =91expert=92 suggests there may be flow = separation=20 before the aft end of the fairing causing high pressure behind the=20 exit).  Put VGs on the top of the exit fairing and/or reduce exit = area.

 

e)    = None=20 of the above.

 

I suspect the normal = aerodynamic=20 pressure differential between the inlet and outlet points is minimal;=20 especially in level flight where it could be near zero.  Option = c) seems=20 the most sure-fire to me.

Thanks for=20 input.

 

Al

 

Al, it is fantastic getting your machine = into the air=20 with such minor things to fix. When I had my SOOB in the AVID = inspected, it=20 took me four month until the first flight. All because of cooling = issues.=20
I think your conclusion about the missing = ram air at=20 the intake is the major reason why the oil cooling did not improve at = higher=20 air speed. A second point may be the air outlet. It looks like a=20 turbulence could form where the back scoop protrudes from the wing = surface.=20 This turbulence could produce vorticies over the edge at the outlet, = reducing=20 the effective area of the outlet. A = more=20 continous transition from the wing surface to the scoop surface would = reduce=20 the possibility of this to happen.        &nb= sp;           &nbs= p;            = ;            =             &= nbsp;           &n= bsp;           &nb= sp;           &nbs= p;            = ;            =             &= nbsp;=20
FWIW   
You will enjoy every bit of this=20 machine soon!
 
 Richard Sohn
N-2071U
 
         &nbs= p;            = ;            =             &= nbsp;           &n= bsp;           &nb= sp;      

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