May 27, 2009
Adding some photos due to some email questions that I've received. The tubing shown on the outside of the fuselage on the last two photos were there to measure air pressures in the cooling ducts. The tubes connected to a magnehelic gauge in the cockpit.February 2, 2009
A very late update. I resolved the heat in the cockpit problem. It was due to inadequate sealing of the ducts to the fuselage skin. A few screws/nutplates and problem solved. Also, I have recently been asked about the dimensions of the VW Rabbit radiator. It is 21.5" x 12.5" x 1.25" thick. Please understand that I do not consider the duct inlet/outlet dimensions optimal and that no science was put into their design. I have been told by several folks "in the know" that the inlet should be about half of it's current size. Currently, the inlet is 10" x 2" and the outlet is 10" x 2.5".May 25, 2008
I haven't updated this page in awhile since my cooling system is just working! The only "problems" to date has been that the radiator in the tailcone generates quite a bit of heat which ends up in the cockpit. This is kinda nice in the cold months, not so nice in the hot months. I am in the process of adding a couple of cool air inlet scoops and outlets that are for just the tailcone. My hope is that this will cool things down back there and in the cockpit.
I am now flying with a P-51 style belly scoop with the radiator mounted in the tail. See the Cooling System Design Page for design details.December 19, 2005
I didn't get any super warm weather flying in this past year. However; the flying that I have done has presented zero problems for the in-tail cooling system. The temperature gauge never moves off of 195-200 degrees (thermostat temp - no matter whether sitting on the ground or climbing hard). The only negative is that I am getting some heat in the cockpit. I think a smaller radiator inlet (less inlet air) and some better sealing on the ducts would solve this problem.August 15, 2004
It seems to work! I flew for about 30 minutes today and the water temp stayed right about thermostat temperature, never more than 200 degrees. The only negative was that it got pretty warm in the cockpit. Obviously, there is some sealing work to be done on the ducts!August 14, 2004
Here is a shot with the new cooling ducts installed on the plane. It works great on the ground - I'm unable to get the engine over thermostat temperature.July 17, 2004
I had to make two S-bends out of 1" aluminum tubing to route the coolant lines from under the fuselage into the tail section. I tried a number of different things but am happy with this approach. This was built from two U bends from Burns Stainless. These were cut roughly in half and welded back together as an S bend. A small square plate of 6061 was fabricated to hold the tubes and to attach to the fuselage.June 20, 2004
Painted and heading back to the airport. Like most of my work, it looks really good from about 20 feet!! :-)June 13, 2004
Mostly done now. The rudder cable has been redirected up the side of the fuselage. Two pulleys turn it back to the center of the fuselage forward of the cooling ducts. The pulleys look a little off kilter in these photos. They are that way for proper alignment with the cable. A new NAV antenna has been glassed into place. The external duct is complete except for a coat of paint. In this photo it is still primer gray.
April 9, 2004
I have formed and glassed the external scoop/bump. I made this thing as small and as light as possible. The inlet is approx. 2x10 inches. After several additional glassing steps to incorporate the internal ductwork, the scoop will be glassed to the tailcone.
The inlet/outlet holes shown here are just the beginning cuts. Obviously a fair amount of "finishing" is required.February 20, 2004
It has been a long and cold winter but I am slowly making progress. Currently trying to figure out how to make the outside flange on that aft duct!! :-)December 7, 2003
Ducts have been glassed and most of the mold remnants removed (still have some cleanup to do). Generally, the ducts have come out fitting pretty well and are quite light.December 2, 2003
More time on the internal radiator ducts. Foam molds were shaped, covered in sheet rock joint compound and sanded til smooth (repeat over and over several times). Then a few coats of Kilz paint sealer followed by a thick coat of old enamel spray paint. Along with a good coat of wax, the spray paint helps to act as a release when the molds are glassed.
Here they are with the enamel spray paint.November 23, 2003
Spent a bunch of time this weekend on the internal radiator ducts. Here are two photos of the work in progress. The first shows the forward duct that leads the air into the radiator. The second is the duct from the aft bulkhead to the exit. There will be a third duct which guides the air from the radiator to the aft duct.August 1, 2003
A variety of changes have been made to the cooling system during ground runs and initial flights.
During initial testing I was experiencing high coolant temps. I tried a little bit of everything but couldn't get them down. After much sluthing I realized that the coolant wasn't even getting full circulation OR when it did, it was at much too high of a temp. After much time/energy I realized that I had installed the stock Subaru coolant temp sensor and hooked it to my aftermarket gauge. Big WHOOPS! I changed the sensor and all of my cooling problems went away!!!
One of the changes that I made during the above excercise was to add a 1/2" coolant bypass from the below the swirl pot to the thermostat bypass inlet. This is in addition to the 3/16" coolant bypass line that runs thru the Air-Bypass and Throttle Body.
I still have the VW radiator just hung on the belly (very draggy) but it is working. During my last flight, the coolant temp sat at about 210 degrees and oil temp at about 220 degrees.July 22, 2002
I machined a new thermostat housing to solve two problems. First, I needed to reduce the hose size from 1.75" to 1". Second, I needed the flow to go straight down and not out at 90 degree's. I'm a machinst "wannabe", so be kind!!June 1, 2002
Due to the tight space constraints that I have, I am unable to use the stock upper coolant manifold. Instead, I have constructed a swirl pot and mounted it to the forward, left side of the engine. The left and right cylinder banks feed into this swirl pot using 3/4" hose. The clear tubing you see in these photos is for testing purposes only, I won't be flying with it. Also, difficult to see but the throttle body is mounted upside-down (from stock installation) to provide better throttle cable location.
The left coolant manifold feeds into the swirl pot and also provides hot coolant for the air-bypass solenoid and throttle body.