Several weeks back, I requested comments from the list on the canard root farings. See the results at http://www.corvairq.info/Canard%20fairing.htm

Thanks again for your comments.

Joseph Snow

Joseph,

Your new fairing looks A LOT better. Interesting how, if you keep at it,
the better look emerges.

I have to say I'm not crazy about your fairing around the exhaust. It looks
like you are making it a kind of engine cooling augmenter. I am just
concerned that you may be inducing more drag. Anything that sticks out is
bad. Cogitate on a better way.

Sam



_____

From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Joseph Snow
Sent: Sunday, October 29, 2006 12:53 PM
To: Q-Performance@...; Q-LIST@...
Subject: [Q-LIST] Canard Root Faring



Several weeks back, I requested comments from the list on the canard root
farings. See the results at http://www.corvairq
<http://www.corvairq.info/Canard%20fairing.htm> .info/Canard%20fairing.htm

Thanks again for your comments.

Joseph Snow

Sam,

You are right; it is a cooling augmentor. I don't like it either. So, I have been cogitating. I have to figure a way to route my exhaust stack around the engine mount. Maybe a ball joint will alow me to tuck the pipes close to the bottom of the cowl (inside) into troughs shaped like a reverse NACA vent for each side. I would like the flow to avoid the belly board. I saw an example of this done by a KR builder,
http://home.hiwaay.net/~langford/nacaducts/index.html

If I can do something like this, it would take care of the cooling and get rid of the "lumps on the bottom of the cowl.

Joseph

Hmmm, wasn't it Sky Dog who mentioned the other day that NACA ducts
don't work in reverse? Or did I mis-interpret that?
Larry Hamm

Joseph Snow wrote:

I do remember someone saying that. However, the web page cited shows them or something that looks like them. And, the airplane has 250+ hours without engine cooling problems.

Joseph

Yes the NACA needs to allow the airstream to expand to reduce pressure as it
enters the shape. The pics show the reverse ie the exhaust stream is being
contracted and pressure increased.

Peter



_____

From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Larry Hamm
Sent: Wednesday, 1 November 2006 8:02 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Canard Root Faring



Hmmm, wasn't it Sky Dog who mentioned the other day that NACA ducts
don't work in reverse? Or did I mis-interpret that?
Larry Hamm

Joseph Snow wrote:

Maybe a ball joint will alow
me to tuck the pipes close to the bottom of the cowl (inside) into
troughs shaped like a reverse NACA vent for each side. I would like
the flow to avoid the belly board. I saw an example of this done by
a KR builder, http://home.

<http://home.hiwaay.net/~langford/nacaducts/index.html>
hiwaay.net/~langford/nacaducts/index.html

Peter,

Thanks for your comment.

So, if I started with a 1 in. trough on the inside of the cowl that expanded to 3-4" x 1.5 " as it exited under the firewall into a trough which expanded to about 6 inches as it became shallower until it faired with the belly, the decreasing pressure would accelerate the engine cooling air out of the cowl? If I also included the engine exhaust in this trough, the exhaust pulses would help to accelerate the cooling air from the cowl, somewhat like the augmenters on the Piper Apache Twin.? What do you think? Also, what effect will the relatively high pressure air under the canard/belly have on cooling airflow?

Joseph

Joseph,

I think that would work. I don't know the Apache twin augmenters but a very
effective air pump or exhaust ejector pump (sometimes called a venturi pump)
can be made by messing with the ends of the exhaust pipe so as to cause
turbulence. Eg a circular ring of say 1/16" projecting into the exhaust
stream. Then if this modified tail pipe is projected at least 3" into a
larger diam tube with a nicely flared opening facing the engine compartment
then the turbulent exhaust gasses will draw engine cowl air through the
larger tube. I had a properly designed venture pump with the Norton
installation which pulled 28" water gauge. That is some sucker. Ideally it
could be designed to provide some small amount of thrust. But it is possible
to get a bit carried away with schemes like this, simplest is usually best.
Ram air forced through ducts around the fins will do a good job in cooling
the Q if it is fitted with a generous adjustable cowl flap under the cowl
and my cowl flap also has some effect as an air brake.

Peter



_____

From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Joseph Snow
Sent: Wednesday, 1 November 2006 3:05 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Canard Root Faring



Peter,

Thanks for your comment.

So, if I started with a 1 in. trough on the inside of the cowl that expanded
to 3-4" x 1.5 " as it exited under the firewall into a trough which expanded
to about 6 inches as it became shallower until it faired with the belly, the
decreasing pressure would accelerate the engine cooling air out of the cowl?
If I also included the engine exhaust in this trough, the exhaust pulses
would help to accelerate the cooling air from the cowl, somewhat like the
augmenters on the Piper Apache Twin.? What do you think? Also, what effect
will the relatively high pressure air under the canard/belly have on cooling
airflow?

Joseph

Peter,
Except for the 1/16" venturi ring, your description of the augmenter setup sounds like my current setup. The 1/16" ring generates the turbulence? If it worked, I would be happy to keep it as is. However, I do think the parts outside of my cowl will be draggy. How do you get the 1/16" ring?...perhaps lay a weld bead on the inside end of the pipe?

Joseph

Joseph a weld bead would do the job best if you can get a sharp edge facing
the exhaust stream. The Norton extractor was made with the end of the
tailpipe crushed and shaped like a rectangular cross. It would be possible
to enclose the whole thing inside the lower cowl?

Peter



_____

From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Joseph Snow
Sent: Thursday, 2 November 2006 10:19 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Canard Root Faring



Peter,
Except for the 1/16" venturi ring, your description of the augmenter setup
sounds like my current setup. The 1/16" ring generates the turbulence? If it
worked, I would be happy to keep it as is. However, I do think the parts
outside of my cowl will be draggy. How do you get the 1/16" ring?...perhaps
lay a weld bead on the inside end of the pipe?

Joseph