From: "Eric Westland" Subject: COZY: Cooling issues and VG's Date: Wed, 18 Jul 2001 09:54:21 -0700 I too have been working on cooling and while my setup may be different, I thought I would share what I have learned hoping it might help. To better understand what was going on inside my engine compartment, I placed probes for CHT on all 4 top spark plug locations and installed an additional probe in the bayonet position on my hottest cylinder, #2. What I found surprised me, as the tops would read up to 130 degrees F hotter than the bottom. Had I just located probes on the bottom of my updraft cooling IO-360 cylinders, I would have never known that the tops were not getting enough cooling air. My Cozy Mark IV has the plans-built NACA inlet, but since the cowling was built for a parallel-valve engine and mine is the fuel injected angle-valve, I had to enlarge the bottom of the cowling which had the net effect of lowering/enlarging the cooling inlet 2". This made the opening larger to accommodate the fuel servo and air filter box. I never liked it, but at the time it was the only way I could get it all to fit. Looking to improve the spread of cooling temps from the bottom of the heads to the tops, I dove into all the CSA articles I could find and consulted with some very knowledgeable Canardians. I worked on baffling, ramps, eliminating sharp edges - all with no noticeable improvement. I had a relatively huge inlet, so it was inconceivable to me that I wasn't getting enough air, but it needed to be checked out, so I hooked up an extra airspeed indicator and ran lines from it to the high and low pressure sides of the cowling. I probably should have done this much sooner because what I discovered was the high pressure side was not very high. It was time to move the servo/airbox out of the way so more cooling air could get in freely. Moving the servo was a much bigger job than I thought, but I knew this would help, so I did not mind all the work. Once completed, the opening for cooling air looked huge and unobstructed in any way - this had to help and I was excited to fly it to find out how much it helped - unfortunately, it didn't help a bit. It was then time to coat the bottom of my plane with dirty oil and go flying. I did so and when I landed, I had my good friend who is an aero engineering genius look at the patterns and he basically told me the inlet was too large, the air was separating well ahead of the opening and that it was basically going around instead of inside the cowling. So, he suggested installing a couple of temporary pieces of sheet metal to the sides of the inlet to extend it's vertical sides (the thought being to capture more air before it got the chance to "get away"), but this made no difference either. So, we slept on it and the next day he asked me to rig a second pitot tube pointing directly into the air stream and located in the center of the cooling inlet. Off I went flying and when my panel airspeed indicator was reading 160 mph, the one measuring the inlet airspeed was only reading 50 mph! He then had me move the probe 2" lower and go flying again. This time it read whatever speed I was flying at. So, it was time to clean up the air going into the cowling. My good friend deserves the credit for what follows and I believe that while my specific installation will differ from yours, this is so easy to do that it would be worth trying if you were looking to improve your cooling. He didn't want me to have to start chopping on my cowling, so he suggested applying what he does best and installing a couple of vortex generators on the bottom of the fuselage to help add some energy to the cooling air to help more of it get into the inlet. So, I made up (2) 1" x 4" angles of aluminum sheet metal and installed them at a 20 degree angle relative to the fuselage center line with carpet tape. The VG's need some distance from the opening to work, so we placed them on the front portion of the landing brake about 6" apart from each other. The test flight now showed 100 mph air entering the inlet in the center probe position when I was flying at 160 mph, but there was a vibration created somewhere (maybe the brake rumbling or disturbed air hitting the cowling), but the bigger issue was that I could not open my landing brake on final without a huge pull. So, we tried making them 1-1/2" x 6" and installing them in front of the brake, but still had the same results as the first try, although I could now operate the landing brake as before. Next we tried installing them just aft of the landing brake, went back to the 1" x 4" VG's and I went flying again. When I looked at the second airspeed indicator, I could not believe my eyes as it was now reading whatever speed I was flying at and when I checked my CHT's they were reading 30 to 50 degrees cooler on the tops! The vibration went away as well. If there was a negative effect on my top-end speed, I don't think it was much. I have not done any experimenting since we completed this just a couple of weeks ago and for now, I'm just enjoying flying it. I'd love to hear if someone else finds success with this idea as it may help he fine tune what I have now. Plans for this next winter include reworking the cowling to it's original size, although I'm tempted to leave what I have as it's working better than before and if I've learned one thing, it's this - cooling air paths are very unpredictable, unintuitive and humbling. Eric _________________________________________ Eric Westland Cozy Mark IV N325PD http://home1.gte.net/res08ahw/index.htm From: "Eric Westland" Subject: COZY: Re: [c-a] Cooling issues and VG's Date: Wed, 18 Jul 2001 21:27:31 -0700 I have received some questions seeking additional information and/or clarification of what I discovered, so I thought I would just answer them here as best as I could since others may want to know. BTW, thanks to those that sent kind words. > Are you saying, using your VG's modification (as described), you can use > the plans-built NACA inlet? I don't know. Mine is not standard as I dropped the opening of the inlet 2 additional inches to accomidate my engine installation. I'm hoping someone can tell me what they got for results with the plans-sized opening as I would like to make mine smaller just so it looks better. > The VG's sound like a great idea here. Were yours on the fuselage adjacent > to the ramp of the naca scoop? In terms of location were they 25% of the > distance back along the naca scoop? Were they diverging as the air moved aft > or converging? I'd like to try something like this also...so more details > please... and... > This may be obvious to some Canardians, but I'm curious. How were the tips > of your VG's pointed relative to the centerline of your bird, in or out? I'm sorry I don't have any pictures, although there is not much to show. If you promise not to laugh out loud at the quality, I did cobble together a quick drawing showing their approximate location and posted it at http://home1.gte.net/res08ahw/vg.htm. I have not experimented beyond what I have desribed and I'm sure there may be better locations for the VG's or better sizes. This is easy for anyone to try, I'm hoping some folks find success and share thier results. Regards, Eric _________________________________________ Eric Westland Cozy Mark IV N325PD http://home1.gte.net/res08ahw/index.htm From: "Bob Misterka" Subject: COZY: Re: Cooling issues and VG's Date: Thu, 19 Jul 2001 15:53:05 -0400 Robert Irving wrote:" Why does it seem that we are always "re-inventing the wheel" with cooling?" Just my opinion here. Look at what we're dealing with. On a tractor design the cooling is brute force. It shouldn't be too hard to force air through the fins when you know it's hitting them at 100-200 knots, straight on no interference. In our pusher type design we need to smoothly flow the air over the entire length of the fuselage , make sure it enters a submerged, low drag inlet, have it take a 90 degree turn and then flow smoothly up to and through the cylinder fins. There's a whole lot more variables when dealing with our design. Add to it that the NACA submerged inlet is what I call (from my radio engineering days) FM which stands for F....ing Magic. These things operate in ways not understood by many (if any). So yes, it's not unusual to have to invent the wheel every time it's dealt with here. But that's part of the game, I guess :) Bob Misterka _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp