Paul and Group,

Thank you very much for you book, /"How to Cool Your Wankel". /It  was invaluable to me with my cooling design. You will certainly  see that I tried to apply the concepts shown in the book.

I'm writing to solicit critiques on my cooling design. I'm  building a Glass Goose...a composite, two place, pusher, seaplane  (see Glass Goose (Small).jpg). I'm installing a Mazda Renesis four  port rotary.
I'm locating the stock RX8 oil cooler five inches in front of the  engine directly behind the intake (see Oil cooler location  (Small).jpg).

Water cooling will be accomplished via two 16" x 12" x 2" heat  exchangers located inside the pylon below the engine. I've built  same dimension cardboard boxes and place them outside of the  pylons just to show you where they will be located when installed  on the inside on the pylon (see Heat exchanger location  (Small).jpg, Heat exchanger location rear view (Small).jpg, and  Heat exchanger located inside the pylon (Small).jpg).

Here is my cooling design using the principles of your book  (Engine Cooling Glass Goose.jpg). I'll be flying in Texas so since  my main objective is to not overheat I tended to design toward the  more generous side of any envelopes....intake sizes (30% of core  face), core sizes (600 to 800 ci. My design has 768 ci), etc.

And, here are my questions:

1. Have I done it right? Too much? Not enough? I'm hoping you'll  be able to tell me I can use less (the intake area (see Intake  area.jpg) is about 4 inches too wide for my cowling. However,  proper cooling in all operations in the most important issue.

2. Seems like I've read on the site that if two heat exchangers  are used they should be in series rather than parallel. Is that  correct?

3. If parallel is the answer, I would like to route water hoses to  the top of the right heat exchanger, out the bottom of the right  heat exchanger, to the bottom of the left heat exchanger, then out  the top of the left heat exchanger back to the engine. Will that  work? Does a heat exchanger care which way water runs through it?

4. One of the aerodynamic issues the Glass Goose has is  maintaining air flow down the side of the pylon. Current airplanes  use VGs and/or turning vanes to control the air down the side of  pylon. As a byproduct or advantage of this cooling design, I'm  hoping that the turbulent air coming out of the cores along the  pylon may help hold the air to the pylon. What do you think?

5. Do you think the prop may pull some air through the heat  exchangers to help cooling on the ground? Do I need a fan in this  design? Where would it go?

Do you know where I can get custom louvered grills?

Thank you very much for your consideration and comments,

Sandy McNabb


I like your drawings Sandy. Very well done.

Q2 should be in parallel.

Q4 since the top speed is  low the best idea IMHO is to position  two 19 by 16 by 3/4 inch thick cores on the outside of the pylon  and tilt them out to form scoops.  Real quick and easy to do. Use  a boundary layer splitter plate about 1 inch out from the pylon  surface.

I know this is a radical idea but it will work and has worked for  other people when mounted on the bottom of the fuselage.
Check it out in my book.

Your picture of the rads mounted on the outside triggered this  idea in my feeble brain :) We have gone around and around on  cooling the Goose and this is the best idea anybody has come up  with so far IMHO.
The drag on the aft pylon is high anyway so this will not add much  more.

Q5 yes the prop will help.

I'll send some more ideas in the next message as there is no room  in this one left.

We will discuss plumbing details when we come up with an  acceptable solution for you.

Paul Lamar

Sorry. I made a word error in my previous posting. In question #3,  it should be "If series is the answer,....."

Sandy.

No problem Sandy. Here are the best of the old ideas.
The main objection was loss of cargo room.

I'll do a 3D of the latest idea I mentioned in the message above.


Paul Lamar

Paul,
I can't remember seeing these integral oil pan engine mount designs  before.
I have been agonizing over a simple design for and integral mount  pan design
for the single and one of these will fit the bill nicely.

To my mind the integral approach if far better than the 2 piece  approach, in
that it would be easier to fit.
Thanks
George (down under)


Sandy, The problem using the front cowl scoop is there is not  enough room
along side the engine when the exhaust system, motor mounts and  alternator
are mounted to get the cooling air down and back to the internally  mounted
rads. Make sure you mock up the exhaust system, motor mounts and  alternator
before you cast the installation in concrete.

I am still working on the new Goose 3D.

Paul Lamar

Here are the 3D's.
IMHO this is the easiest and most likely to work.
You can tilt the rads in and out to increase or decrease cooling.

BTW the area behind the engine in the pylon is ideal for an exhaust  ejector
(AKA augmenter). Given the prop will chop up the noise I think you  can get
away without a muffler. You will have to line the pylon with fiber  frax and
thin SS.

Paul Lamar



Paul,

I'm very excited about the cooling prospects you've presented me.  I've got
to admit my first reaction was, "Wow! That'll be butt ugly to put  those rads
on the outside of the pylon!" However, after a little study, I  think can
give the design some nice esthetics by building streamlining  fiberglass
shrouds around the rads and even include turning vanes in the  design which
have proven to be very beneficial for the Glass Goose's airflow  down the
side of the pylon. I could also make the leading edge of the  turning vanes
variable which would control the intake area for the rads...kind of a
reverse cowl flap. That maybe overdoing since the max speed for the  Glass
Goose is advertise at only 140 knots. I agree the design would be  very easy
to build and would seem to have very efficient cooling.  I have two
concerns: The affect of this design on the air flow down the side  of the
pylon. Seems like the rads on the outside of the pylon may  interrupt airflow
to the prop....then again the turbulent air it might improve it.  Secondly,
your recommendation for 19" x 16" x 3/4" core only yields 228 ci of
cooling....times two rads give 456 ci of cooling which is  substantially less
that the 600 to 800 ci you say is necessary for a rotary in your  book. What
do you think?

I'll be out on an airline trip for the next four days, so it might  be a
little while before I can get back with you.

Thanks for your help,

Sandy

Great Sandy that is the right attitude. We have been around and  around with a couple of Goose builders on this problem. It is not  easy squeezing in a cooling system. The best thing to do is bring  the curved intake duct with the boundary layer bypass duct forward  around the corner so to speak and keep the aft sides of the pylon  flat. That will move the rads in at the back. The prop will do  wonders to suck air through the rads, the boundary layer bypass  duct as well as the exhaust ejector. The air from the oil rad will  go over the engine cooling the engine and out the exhaust ejector  and cool the exhaust system it self. A couple of Dodge Neon rads  will work. The header tanks will have to be TIG welded up as the  stock ones are plastic. I'll do a little more work on the 3D's. I  think Jerry Hey may be able to do the rad work. I have not heard  from Scott Gettings for awhile so he may be interested in this  system as well. The RX8 alternator is pretty tricky to side mount  as well we had to come up with some sort idler pulley as I recall.

Where are you? Scott is on the space coast in Florida.

Paul Lamar

-- 

Hey Paul,

I'm still around -- I'm very embarrassed to say that I've been so
busy with my job that my project has been sitting on the shelf for
quite a while.  I've been in touch with Sandy during this time.
Sandy has actually been to my shop, and he's seen all my mockups.  We
have discussed your visit and the various options.  Sandy has done a
great job on his plane to date.

I really like this latest concept, where the radiators still function
as turning vanes.  It seems to be an evolution of what you last
recommended, but using the water radiators in the back instead of the
oil coolers.   The only downside I see to this approach is the water
pump is up front and the oil lines are in the rear -- so the plumbing
would be pretty extensive.

In this version, should the rear of the radiators be left open, or
ducted back to the prop?

Scott Gettings

They seem to work well left open to the ambient low pressure in all the
airplanes where they have been used so far. The most recent was
an LSA Hornet powered by a Rotamax rotary. This rad is real thick because that is what they had lying around and it was a last minute test. A quick and dirty
ugly installation :) The last pict is without the rad taken at Sun n Fun

Paul Lamar