REFLECTOR: Updraft cooling
Dave Philipsen
velocity at davebiz.com
Sat Feb 17 22:08:06 CST 2007
Dean,
I'm in the same boat (plane) as you. I bought a Velocity that was built
by someone else and it has updraft cooling too. But, I think that's the
way they all were originally. The NACA scoops were introduced as
standard a little later. I'm in the midst of working on ways to cool it
more efficiently. At least this forum will help perhaps by providing us
with some ideas.
Unterreiner wrote:
> I have an IO-360 in my Velocity with updraft cooling. The guy who built the
> plane went to alot of trouble to get it to cool properly in cruise, and it
> still needs to be modified so it will cool better during takeoff. Also, the
> Lycoming engines are designed to be cooled from the top down. I wish the guy
> who built my plane would have used the NACA plenum system. It's alot
> simpler, cools the engine the way it's supposed to be cooled and is less
> prone to develop cooling problems.
>
> Dean Unterreiner
> ----- Original Message -----
> From: <reflector-request at tvbf.org>
> To: <reflector at tvbf.org>
> Sent: Saturday, February 17, 2007 5:52 PM
> Subject: Reflector Digest, Vol 33, Issue 47
>
>
>
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>> Today's Topics:
>>
>> 1. Re: updraft cooling (Scott Derrick)
>> 2. Re: updraft cooling (John Dibble)
>> 3. Re: updraft cooling (Douglas Holub)
>> 4. Re: updraft vs sidedraft vs updraft cooling (gpoole)
>> 5. Re: updraft cooling (Al Gietzen)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Sat, 17 Feb 2007 15:57:56 -0500 (EST)
>> From: "Scott Derrick" <scott at tnstaafl.net>
>> Subject: Re: REFLECTOR: updraft cooling
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Message-ID: <43917.63.164.47.227.1171745876.squirrel at tnstaafl.net>
>> Content-Type: text/plain;charset=iso-8859-1
>>
>> Doug,
>>
>> I had updraft on my IO360 and it worked fine. I had to run LOP in the
>> summer(I did all the time anyway) to keep the engine cool enough. There
>> were times when I stopped for gas and during the following departure
>> climbout I would have to level off at an intermediate altitude for awhile
>> to get the oil temps back down below 230.
>>
>> Installing my 520 I conferred with Velocity(ScottB and Brendon) and was
>> advised I would need to use downdraft as they had never successfully seen
>> an updraft system work for the big six cylinder engines. So I did the
>> conversion.
>>
>> I thought that using NACA intakes would "theoretically" be more drag
>> effecient ?
>>
>> Scott
>>
>>
>>
>>> I can understand why Burt Rutan and Nat Puffer are proponents of updraft
>>> cooling. From an engineering point of view, it has a lot going for it.
>>> You
>>> need more cooling when the airplane is climbing. If the cooling intake is
>>> below the wing, the pressure is higher during a climb so you
>>> automatically
>>> get more cooling during a climb. Similarly, it would be nice if cooling
>>> was minimized during descent. The pressure is reduced under the wing
>>> during descent, and so there is less cooling to the engine. Also, you've
>>> got convection working with you instead of against you with an updraft
>>> system.
>>>
>>> That all adds up to more drag with down draft cooling, because the NACA
>>> scoops have to be large enough so that there is adequate cooling during
>>> climb out, when the pressure at the NACAs is at its minimum.
>>>
>>> But the down draft is a lot simpler to implement, and that's probably
>>> going to be the deciding factor for me.
>>>
>>> Doug Holub_______________________________________________
>>> To change your email address, visit
>>> http://www.tvbf.org/mailman/listinfo/reflector
>>>
>>> Visit the gallery! www.tvbf.org/gallery
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>>>
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Sat, 17 Feb 2007 15:04:56 -0600
>> From: John Dibble <aminetech at bluefrog.com>
>> Subject: Re: REFLECTOR: updraft cooling
>> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>> Message-ID: <45D76DF8.5468770B at bluefrog.com>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> I assume that updraft simply refers to the intake air coming from below
>> as opposed to downdraft where the air comes from the NACAs above. I
>> think the way it passes the engine is the same. It would be inefficient
>> to pass the air past the exhaust pipes first.
>>
>> John
>>
>> Chuck Jensen wrote:
>>
>>
>>> I've not seen the layout of an updraft cooling system, but does the
>>> air get preheated from passing by the exhaust pipes before it every
>>> gets to the cylinder heads? If it does, that would greatly increase
>>> the volume of air required because of the reduced delta T across the
>>> heads. By comparison the top NACAs provide clean, cool air directly
>>> to the CHs. Too simple--I must be missing something?
>>> Chuck Jensen
>>>
>>> -----Original Message-----
>>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]
>>> On Behalf Of John Dibble
>>> Sent: Saturday, February 17, 2007 2:41 PM
>>> To: Velocity Aircraft Owners and Builders list
>>> Subject: Re: REFLECTOR: updraft cooling
>>>
>>> I think the amount of air going past the cylinders will determine the
>>> degree of cooling, so it's a matter of making the NACA or armpit scoop
>>> and ducts big enough for sufficient air.
>>>
>>> John
>>>
>>> Ron Brown wrote:
>>>
>>>
>>>> And, the downdraft NACA cooling for some unexplainable reason, runs
>>>> about 40 degrees cooler than the updraft cooling. Mark Machado
>>>> converted what is now the factory trainer from updraft to downdraft
>>>> and says the heads ran 30-40 degrees cooler. My 173 Elite RG runs
>>>> 360-370 max on a long climb out and 320-340 degrees during a 2600
>>>> rpm/155 kt cruise. I highly recommend the NACA cooling system.
>>>>
>>> ----------------------------------------------------------------
>>> _______________________________________________
>>> To change your email address, visit
>>> http://www.tvbf.org/mailman/listinfo/reflector
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>> ------------------------------
>>
>> Message: 3
>> Date: Sat, 17 Feb 2007 16:13:01 -0600
>> From: "Douglas Holub" <doug.holub at tx.rr.com>
>> Subject: Re: REFLECTOR: updraft cooling
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Message-ID: <007e01c752e0$ca67f130$6a01a8c0 at Workshop>
>> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>> reply-type=original
>>
>> "I thought that using NACA intakes would 'theoretically' be more drag
>> effecient ?"
>> -------------------------------------------------------------------
>> I was just comparing updraft to downdraft. It looks like I could put one
>> big
>> NACA underneath the rear seat. I was thinking of using that spot for ram
>> air, though.
>>
>> I'm a little confused about the benefits of a NACA scoop. I need to read
>> up
>> on them some more. I think that if the cowl lip were extended up a little
>> to
>> catch the air it might be more efficient than the NACA scoops. But even
>> if
>> it were more efficient, you would be making it a little harder for air to
>> flow to the propeller because the cowl would be getting a little taller.
>> But
>> then, you lose some head room in the back seats with the NACAs. Decisions,
>> decisions.
>>
>> Doug Holub
>>
>> ----- Original Message -----
>> From: "Scott Derrick" <scott at tnstaafl.net>
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Sent: Saturday, February 17, 2007 2:57 PM
>> Subject: Re: REFLECTOR: updraft cooling
>>
>>
>>
>>> Doug,
>>>
>>> I had updraft on my IO360 and it worked fine. I had to run LOP in the
>>> summer(I did all the time anyway) to keep the engine cool enough. There
>>> were times when I stopped for gas and during the following departure
>>> climbout I would have to level off at an intermediate altitude for awhile
>>> to get the oil temps back down below 230.
>>>
>>> Installing my 520 I conferred with Velocity(ScottB and Brendon) and was
>>> advised I would need to use downdraft as they had never successfully seen
>>> an updraft system work for the big six cylinder engines. So I did the
>>> conversion.
>>>
>>> I thought that using NACA intakes would "theoretically" be more drag
>>> effecient ?
>>>
>>> Scott
>>>
>>>
>>>
>>>> I can understand why Burt Rutan and Nat Puffer are proponents of updraft
>>>> cooling. From an engineering point of view, it has a lot going for it.
>>>> You
>>>> need more cooling when the airplane is climbing. If the cooling intake
>>>> is
>>>> below the wing, the pressure is higher during a climb so you
>>>> automatically
>>>> get more cooling during a climb. Similarly, it would be nice if cooling
>>>> was minimized during descent. The pressure is reduced under the wing
>>>> during descent, and so there is less cooling to the engine. Also, you've
>>>> got convection working with you instead of against you with an updraft
>>>> system.
>>>>
>>>> That all adds up to more drag with down draft cooling, because the NACA
>>>> scoops have to be large enough so that there is adequate cooling during
>>>> climb out, when the pressure at the NACAs is at its minimum.
>>>>
>>>> But the down draft is a lot simpler to implement, and that's probably
>>>> going to be the deciding factor for me.
>>>>
>>>> Doug Holub_______________________________________________
>>>> To change your email address, visit
>>>> http://www.tvbf.org/mailman/listinfo/reflector
>>>>
>>>> Visit the gallery! www.tvbf.org/gallery
>>>> user:pw = tvbf:jamaicangoose
>>>> Check new archives: www.tvbf.org/pipermail
>>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>>>
>>> _______________________________________________
>>> To change your email address, visit
>>> http://www.tvbf.org/mailman/listinfo/reflector
>>>
>>> Visit the gallery! www.tvbf.org/gallery
>>> user:pw = tvbf:jamaicangoose
>>> Check new archives: www.tvbf.org/pipermail
>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>>
>>>
>>
>>
>> ------------------------------
>>
>> Message: 4
>> Date: Sun, 18 Feb 2007 09:29:29 +1100
>> From: "gpoole" <gpoole at zeta.org.au>
>> Subject: Re: REFLECTOR: updraft vs sidedraft vs updraft cooling
>> To: "'Velocity Aircraft Owners and Builders list'"
>> <reflector at tvbf.org>
>> Message-ID: <00b801c752e3$1725de40$4deb64cb at gregb97b7132b4>
>> Content-Type: text/plain; charset="windows-1250"
>>
>> I have been making the same deliberations as Doug for quite some time.
>> There are compromises with every option ..sigh! Scoops vs NACA ducts...
>>
>> If pinching air before the prop with a scoop on the belly is considered to
>> affect prop efficiency then perhaps (surely?) Al G's & several other's
>> approach of putting radiators in the wing is the way to go. I like the
>> idea
>> of being able to tailor the amount of air to the radiators to balance the
>> compromise between drag and amount of cooling required by having variable
>> inlets. Only problem is that the air needs to do several sharp turns to
>> get
>> to the cylinder heads....which would should slow it down considerably....
>>
>> Would be interested in this thread continuing to see what others think....
>>
>> Greg in Sydney.
>>
>> gregpoole at saaachapter11.com
>>
>>
>> -----Original Message-----
>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>> Behalf Of Douglas Holub
>> Sent: Sunday, 18 February 2007 9:13 AM
>> To: Velocity Aircraft Owners and Builders list
>> Subject: Re: REFLECTOR: updraft cooling
>>
>> "I thought that using NACA intakes would 'theoretically' be more drag
>> effecient ?"
>> -------------------------------------------------------------------
>> I was just comparing updraft to downdraft. It looks like I could put one
>> big
>>
>> NACA underneath the rear seat. I was thinking of using that spot for ram
>> air, though.
>>
>> I'm a little confused about the benefits of a NACA scoop. I need to read
>> up
>>
>> on them some more. I think that if the cowl lip were extended up a little
>> to
>>
>> catch the air it might be more efficient than the NACA scoops. But even
>> if
>> it were more efficient, you would be making it a little harder for air to
>> flow to the propeller because the cowl would be getting a little taller.
>> But
>>
>> then, you lose some head room in the back seats with the NACAs. Decisions,
>> decisions.
>>
>> Doug Holub
>>
>> ----- Original Message -----
>> From: "Scott Derrick" <scott at tnstaafl.net>
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Sent: Saturday, February 17, 2007 2:57 PM
>> Subject: Re: REFLECTOR: updraft cooling
>>
>>
>>
>>> Doug,
>>>
>>> I had updraft on my IO360 and it worked fine. I had to run LOP in the
>>> summer(I did all the time anyway) to keep the engine cool enough. There
>>> were times when I stopped for gas and during the following departure
>>> climbout I would have to level off at an intermediate altitude for awhile
>>> to get the oil temps back down below 230.
>>>
>>> Installing my 520 I conferred with Velocity(ScottB and Brendon) and was
>>> advised I would need to use downdraft as they had never successfully seen
>>> an updraft system work for the big six cylinder engines. So I did the
>>> conversion.
>>>
>>> I thought that using NACA intakes would "theoretically" be more drag
>>> effecient ?
>>>
>>> Scott
>>>
>>>
>>>
>>>> I can understand why Burt Rutan and Nat Puffer are proponents of updraft
>>>> cooling. From an engineering point of view, it has a lot going for it.
>>>> You
>>>> need more cooling when the airplane is climbing. If the cooling intake
>>>> is
>>>> below the wing, the pressure is higher during a climb so you
>>>> automatically
>>>> get more cooling during a climb. Similarly, it would be nice if cooling
>>>> was minimized during descent. The pressure is reduced under the wing
>>>> during descent, and so there is less cooling to the engine. Also, you've
>>>> got convection working with you instead of against you with an updraft
>>>> system.
>>>>
>>>> That all adds up to more drag with down draft cooling, because the NACA
>>>> scoops have to be large enough so that there is adequate cooling during
>>>> climb out, when the pressure at the NACAs is at its minimum.
>>>>
>>>> But the down draft is a lot simpler to implement, and that's probably
>>>> going to be the deciding factor for me.
>>>>
>>>> Doug Holub_______________________________________________
>>>> To change your email address, visit
>>>> http://www.tvbf.org/mailman/listinfo/reflector
>>>>
>>>> Visit the gallery! www.tvbf.org/gallery
>>>> user:pw = tvbf:jamaicangoose
>>>> Check new archives: www.tvbf.org/pipermail
>>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>>>
>>> _______________________________________________
>>> To change your email address, visit
>>> http://www.tvbf.org/mailman/listinfo/reflector
>>>
>>> Visit the gallery! www.tvbf.org/gallery
>>> user:pw = tvbf:jamaicangoose
>>> Check new archives: www.tvbf.org/pipermail
>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>>
>>>
>> _______________________________________________
>> To change your email address, visit
>> http://www.tvbf.org/mailman/listinfo/reflector
>>
>> Visit the gallery! www.tvbf.org/gallery
>> user:pw = tvbf:jamaicangoose
>> Check new archives: www.tvbf.org/pipermail
>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>
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>>
>> ------------------------------
>>
>> Message: 5
>> Date: Sat, 17 Feb 2007 14:52:30 -0800
>> From: "Al Gietzen" <ALVentures at cox.net>
>> Subject: Re: REFLECTOR: updraft cooling
>> To: "'Velocity Aircraft Owners and Builders list'"
>> <reflector at tvbf.org>
>> Message-ID: <000001c752e6$4ecd94c0$6400a8c0 at BigAl>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> Subject: REFLECTOR: updraft cooling
>>
>>
>>
>> I can understand why Burt Rutan and Nat Puffer are proponents of updraft
>> cooling. From an engineering point of view, it has a lot going for it. You
>> need more cooling when the airplane is climbing. If the cooling intake is
>> below the wing, the pressure is higher during a climb so you automatically
>> get more cooling during a climb. Similarly, it would be nice if cooling
>> was
>> minimized during descent. The pressure is reduced under the wing during
>> descent, and so there is less cooling to the engine. Also, you've got
>> convection working with you instead of against you with an updraft system.
>>
>> Doug;
>>
>>
>>
>> I'd think that both climbing and descending are high AOA, and would have
>> similar air pressure under the wing; and given the strake configuration,
>> it
>> is not clear that there is increased pressure during climb. I also think
>> that the main reason for difficulties with the stock armpit scoops and
>> updraft is they are poorly designed scoops. Need to have ever increasing
>> x-section after the entrance, and possilby placing them a bit further
>> outboard from the strake/fuselage intersection would be helpful.
>>
>>
>>
>> I have an 'armpit' scoop for my radiator which is very effective.
>>
>>
>>
>> But the down draft is a lot simpler to implement, and that's probably
>> going
>> to be the deciding factor for me.
>>
>>
>>
>> And since it seems to work well, why not? The amount of natural
>> convection
>> driving force is likely overcome by a few knots of forward speed.
>>
>> Al
>>
>>
>>
>>
>>
>> Doug Holub
>>
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>> ------------------------------
>>
>> _______________________________________________
>> Visit the gallery! tvbf:jamaicangoose
>>
>> End of Reflector Digest, Vol 33, Issue 47
>> *****************************************
>>
>
> _______________________________________________
> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>
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>
--
Dave Philipsen
Velocity STD-FG
N83DP
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