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recapen(at)earthlink.net
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 Posted: Wed Mar 23, 2011 8:48 am Post subject: Optimal cowl intake and outlet areas for engine cooling air |
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Considering the work that was done to develop the SamJames cowl and plenum...and how well they work - I think they're a great starting place.
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robin(at)PaintTheWeb.com
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| Posted: Wed Mar 23, 2011 9:40 am Post subject: Optimal cowl intake and outlet areas for engine cooling air |
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Ahhhh.. as one of the first -10 James cowl flying owners with lots of negative experiences associated with that cowl & plenum I strongly suggest that is about the worst starting place possible. As usual the factory design while not as sexy is functional and proven. I think it’s been established that the openings on the James cowl are just too small to properly cool the Lycoming 540 engine. There has been some success (I am not totally up to date) by increasing the inlet ring size from 4.5” to 6” but that is a lot of work. Imagine taking a new cowl and cutting the inlets back to then manually make transitions to new 6” inlets. Then modify the Plenum to match. Plan on significant R&D right when you want to be flying your plane. I don’t even want to go into the James Plenum that is misaligned from the factory as if they had NOOOO idea how wide their cowl inlets would be to mate to the plenum. The plenum doesn’t even comply with known design principals of smooth but ever increasing volume as the cooling air moves aft. Having owned 4 RV’s, 2 with stock cowls & baffles & 2 with plenums & James cowls I find the plenums to be a large pain in the ass. Extra weight & complexity. Reduced access with limited definable benefit.
Additionally forget about flying LOP out of the box with the James set up. While the stock cowl seems to not be an issue the James owners have a difficult time seeming to straddle a razors edge of LOP vs. poor engine performance even after exhaustive injector balancing and adding an expensive (and heavy) turbo rails & fuel injector shrouds.
Showplanes is making a valiant effort with a new cowl for the -10 that is great looking. Unfortunately it’s still a little early to that party as they do not have a production unit available for sale.
I personally will be removing my James cowl or making additional major modifications to the unit within the next 12 months. If you are building to fly head my warning.
Robin Marks
RV-4 Sold
RV-6A Sold
RV-10 220 Hours
RV-8A 4 Hours
From: owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com) [mailto:owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com)] On Behalf Of Ralph E. Capen
Sent: Wednesday, March 23, 2011 9:27 AM
To: rv10-list(at)matronics.com (rv10-list(at)matronics.com)
Subject: Re: Optimal cowl intake and outlet areas for engine cooling air
--> RV10-List message posted by: "Ralph E. Capen" <recapen(at)earthlink.net (recapen(at)earthlink.net)>
Considering the work that was done to develop the SamJames cowl and plenum...and how well they work - I think they're a great starting place.
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klwerner(at)comcast.net
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| Posted: Wed Mar 23, 2011 10:09 am Post subject: Optimal cowl intake and outlet areas for engine cooling air |
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Dear Rodger,
I has been a few years, but if I recall correctly, then the factor is
right around 1.5 (I think?) for the hot expanding air to exhaust
properly, when compared to the denser cold air coming in.
I agree with Ralph, as Sam James's cowling and plenum systems are very
efficient in that respect, by tightly controlling the cooling airflow
and not wasting any air molecules for unnecessary drag.
Konrad
On Mar 23, 2011, at 10:27 AM, Ralph E. Capen wrote:
[quote]
>
Considering the work that was done to develop the SamJames cowl and
plenum...and how well they work - I think they're a great starting
place.
--
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rj_todd(at)yahoo.co.uk
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| Posted: Wed Mar 23, 2011 9:25 pm Post subject: Optimal cowl intake and outlet areas for engine cooling air |
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Thanks Konrad,
That was the information I was seeking. Incidentally, do you know the source?
I too have the Sam James Cowl and plenum, in fact I was the second customer. It is therefore quite disturbing to hear that the intake area is probably too small. Increasing it to 6" will actually increase the airflow by a factor 5 (proportional to the 4th power of the radius). However my understanding is that the system works by having the intake very close to the propeller trailing edge and therefore having relatively high energy air entering the plenum. The expansion area of the plenum causes the air to slow down and hence be more available for efficient cooling whilst the intake provides the pressure that drives the flow. It's not a simple system and hence I was looking for an engineer's opinion.
I received an update to the cowl some time ago and now I am getting ready to install it. It appears that the air outlet was too small and Sam sent me a new outlet to replace the original. This part will have to be glassed in and as I am also using a non standard exhaust system which is larger than the Vetterman I wanted to design the replacement outlet so that I only have one amendment to make to the cowl.
I was aware of the LOP problem and was lucky enough to be able to see the solution (pressurised injectors) on Deems' aircraft last May.
Many thanks to all,
Rodger
--- On Wed, 23/3/11, Konrad/Conny <klwerner(at)comcast.net> wrote:
[quote] From: Konrad/Conny <klwerner(at)comcast.net>
Subject: Re: Optimal cowl intake and outlet areas for engine cooling air
To: rv10-list(at)matronics.com
Date: Wednesday, 23 March, 2011, 19:06
Konrad/Conny <klwerner(at)comcast.net>
Dear Rodger,
I has been a few years, but if I recall correctly, then the
factor is right around 1.5 (I think?) for the hot expanding
air to exhaust properly, when compared to the denser cold
air coming in.
I agree with Ralph, as Sam James's cowling and plenum
systems are very efficient in that respect, by tightly
controlling the cooling airflow and not wasting any air
molecules for unnecessary drag.
Konrad
On Mar 23, 2011, at 10:27 AM, Ralph E. Capen wrote:
>
<recapen(at)earthlink.net>
>
> Considering the work that was done to develop the
SamJames cowl and plenum...and how well they work - I think
they're a great starting place.
>
>
> --
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klwerner(at)comcast.net
Guest
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| Posted: Wed Mar 23, 2011 11:16 pm Post subject: Optimal cowl intake and outlet areas for engine cooling air |
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Dear Rodger,
I don't remember the original source, as it has been years since I
last thought about the subject matter.
The main thought is to create the proper pressure differential between
the "properly sealed" upper and lower cowling chambers to actually -
suck- a sufficient amount of cooling air through the cylinders...
notice that I didn't say -blow- through  I would actually rig up a
measuring system to see what the actual pressure differential is in
various cowling-/cylinder locations before I would start hacking on
the fiberglass at either intake or exhaust locations. A somewhat
pilot adjustable cowl flap sure would be my choice of heat control
(i.e. exhaust suction control), depending on climb, cruise, or top
speed operation...
The Racers at Reno are a mighty fine example of how little air flow
one can get away with, if their cooling system is really maximized for
proper performance with a minimum of cooling drag. I know Sam James
in person, and he sure is one interesting guy to talk to. I am not an
engineer by any means, but I do listen to smarter people then I am, so
I can learn from them. If I were you, then I would have a long talk
with Sam to discuss all options to improve cooling, if need be... Like
I said earlier, I personally would experiment with it all first, as to
come up with some accurate data to know where the actual problem may
lie to begin with.
Just my two cents, Konrad
On Mar 23, 2011, at 11:21 PM, Rodger Todd wrote:
[quote]
Thanks Konrad,
That was the information I was seeking. Incidentally, do you know
the source?
I too have the Sam James Cowl and plenum, in fact I was the second
customer. It is therefore quite disturbing to hear that the intake
area is probably too small. Increasing it to 6" will actually
increase the airflow by a factor 5 (proportional to the 4th power of
the radius). However my understanding is that the system works by
having the intake very close to the propeller trailing edge and
therefore having relatively high energy air entering the plenum.
The expansion area of the plenum causes the air to slow down and
hence be more available for efficient cooling whilst the intake
provides the pressure that drives the flow. It's not a simple system
and hence I was looking for an engineer's opinion.
I received an update to the cowl some time ago and now I am getting
ready to install it. It appears that the air outlet was too small
and Sam sent me a new outlet to replace the original. This part
will have to be glassed in and as I am also using a non standard
exhaust system which is larger than the Vetterman I wanted to design
the replacement outlet so that I only have one amendment to make to
the cowl.
I was aware of the LOP problem and was lucky enough to be able to
see the solution (pressurised injectors) on Deems' aircraft last May.
Many thanks to all,
Rodger
--- On Wed, 23/3/11, Konrad/Conny <klwerner(at)comcast.net> wrote:
> From: Konrad/Conny <klwerner(at)comcast.net>
> Subject: Re: Optimal cowl intake and outlet areas for
> engine cooling air
> To: rv10-list(at)matronics.com
> Date: Wednesday, 23 March, 2011, 19:06
>
> Konrad/Conny <klwerner(at)comcast.net>
>
> Dear Rodger,
>
> I has been a few years, but if I recall correctly, then the
> factor is right around 1.5 (I think?) for the hot expanding
> air to exhaust properly, when compared to the denser cold
> air coming in.
>
> I agree with Ralph, as Sam James's cowling and plenum
> systems are very efficient in that respect, by tightly
> controlling the cooling airflow and not wasting any air
> molecules for unnecessary drag.
>
> Konrad
> On Mar 23, 2011, at 10:27 AM, Ralph E. Capen wrote:
>
>>
> <recapen(at)earthlink.net>
>>
>> Considering the work that was done to develop the
> SamJames cowl and plenum...and how well they work - I think
> they're a great starting place.
>>
>>
>> --
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
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rj_todd(at)yahoo.co.uk
Guest
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| Posted: Thu Mar 24, 2011 1:09 am Post subject: Optimal cowl intake and outlet areas for engine cooling air |
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Thanks Konrad for your sage advice; I may be able to go to Florida in August and I will try to call on Sam.
THanks very much,
Rodger
PS Do I have stack space for a GTN750?
--- On Thu, 24/3/11, Konrad/Conny <klwerner(at)comcast.net> wrote:
[quote] From: Konrad/Conny <klwerner(at)comcast.net>
Subject: Re: Optimal cowl intake and outlet areas for engine cooling air
To: rv10-list(at)matronics.com
Date: Thursday, 24 March, 2011, 8:11
Konrad/Conny <klwerner(at)comcast.net>
Dear Rodger,
I don't remember the original source, as it has been years
since I last thought about the subject matter.
The main thought is to create the proper pressure
differential between the "properly sealed" upper and lower
cowling chambers to actually -suck- a sufficient amount of
cooling air through the cylinders... notice that I didn't
say -blow- through I would actually rig up a
measuring system to see what the actual pressure
differential is in various cowling-/cylinder locations
before I would start hacking on the fiberglass at either
intake or exhaust locations. A somewhat pilot
adjustable cowl flap sure would be my choice of heat control
(i.e. exhaust suction control), depending on climb,
cruise, or top speed operation...
The Racers at Reno are a mighty fine example of how little
air flow one can get away with, if their cooling system is
really maximized for proper performance with a minimum of
cooling drag. I know Sam James in person, and he sure
is one interesting guy to talk to. I am not an
engineer by any means, but I do listen to smarter people
then I am, so I can learn from them. If I were you,
then I would have a long talk with Sam to discuss all
options to improve cooling, if need be... Like I said
earlier, I personally would experiment with it all first, as
to come up with some accurate data to know where the actual
problem may lie to begin with.
Just my two cents, Konrad
On Mar 23, 2011, at 11:21 PM, Rodger Todd wrote:
>
>
> Thanks Konrad,
>
> That was the information I was seeking.
Incidentally, do you know the source?
>
> I too have the Sam James Cowl and plenum, in fact I
was the second customer. It is therefore quite
disturbing to hear that the intake area is probably too
small. Increasing it to 6" will actually increase the
airflow by a factor 5 (proportional to the 4th power of the
radius). However my understanding is that the system
works by having the intake very close to the propeller
trailing edge and therefore having relatively high energy
air entering the plenum. The expansion area of the
plenum causes the air to slow down and hence be more
available for efficient cooling whilst the intake provides
the pressure that drives the flow. It's not a simple system
and hence I was looking for an engineer's opinion.
>
> I received an update to the cowl some time ago and now
I am getting ready to install it. It appears that the
air outlet was too small and Sam sent me a new outlet to
replace the original. This part will have to be
glassed in and as I am also using a non standard exhaust
system which is larger than the Vetterman I wanted to design
the replacement outlet so that I only have one amendment to
make to the cowl.
>
> I was aware of the LOP problem and was lucky enough to
be able to see the solution (pressurised injectors) on
Deems' aircraft last May.
>
> Many thanks to all,
>
> Rodger
>
> --- On Wed, 23/3/11, Konrad/Conny <klwerner(at)comcast.net>
wrote:
>
>> From: Konrad/Conny <klwerner(at)comcast.net>
>> Subject: Re: Optimal cowl intake and
outlet areas for engine cooling air
>> To: rv10-list(at)matronics.com
>> Date: Wednesday, 23 March, 2011, 19:06
>>
>> Konrad/Conny <klwerner(at)comcast.net>
>>
>> Dear Rodger,
>>
>> I has been a few years, but if I recall correctly,
then the
>> factor is right around 1.5 (I think?) for the hot
expanding
>> air to exhaust properly, when compared to the
denser cold
>> air coming in.
>>
>> I agree with Ralph, as Sam James's cowling and
plenum
>> systems are very efficient in that respect, by
tightly
>> controlling the cooling airflow and not wasting
any air
>> molecules for unnecessary drag.
>>
>> Konrad
>>
>>
>> On Mar 23, 2011, at 10:27 AM, Ralph E. Capen
wrote:
>>
>>>
Capen"
>> <recapen(at)earthlink.net>
>>>
>>> Considering the work that was done to develop
the
>> SamJames cowl and plenum...and how well they work
- I think
>> they're a great starting place.
>>>
>>>
>>> --
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robin(at)PaintTheWeb.com
Guest
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| Posted: Thu Mar 24, 2011 8:06 am Post subject: Optimal cowl intake and outlet areas for engine cooling air |
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Re: Optimal cowl intake and outlet areas for engine cooling air
Ralph,
It’s OK… After all my horrific experiences with the -10 James
cowl (and it has cost me a boat load so far) I still put a James cowl on my
8A because they are more proven. Knowing what I know now I would not even
consider a James cowl for the -10 as it’s deficiencies are just too great
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
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Rhonda(at)bpaengines.com
Guest
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| Posted: Thu Mar 24, 2011 11:02 am Post subject: Optimal cowl intake and outlet areas for engine cooling air |
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I have recently heard that there is a modified cowl from James with improved cooling.
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Robin Marks
Sent: Thursday, March 24, 2011 10:59 AM
To: rv10-list(at)matronics.com
Subject: RE: Optimal cowl intake and outlet areas for engine cooling air
Ralph,
Its OK After all my horrific experiences with the -10 James cowl (and it has cost me a boat load so far) I still put a James cowl on my 8A because they are more proven. Knowing what I know now I would not even consider a James cowl for the -10 as its deficiencies are just too great.
No heat given we are all just learning & sharing our info.
Robin
Do Not Archive
From: owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com) [mailto:owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com)] On Behalf Of Ralph E. Capen
Sent: Thursday, March 24, 2011 3:53 AM
To: rv10-list(at)matronics.com (rv10-list(at)matronics.com)
Subject: Re: Optimal cowl intake and outlet areas for engine cooling air
--> RV10-List message posted by: "Ralph E. Capen" <recapen(at)earthlink.net (recapen(at)earthlink.net)>
Yup - I took an earlier post as an educational point - my experience is with my 6A - which I'm happy with.
Like I said before they should have done the same level of research and testing on the -10 cowl......
Takin the heat - fessin I'm wrong....
--
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