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LSA Quickbuild First Flight

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  • #31
    Even with an oil cooler, I was having a bit of problem with oil temps as the weather warmed up. On sustained climbs at full throttle and 80 mph indicated, the oil temp would go above 200 pretty quickly an I had to level off and reduce power to avoid exceeding 225. CHT's stayed very normal though. We decided to increase the size of the scat tube feeding high pressure air to the cooler from 2 inches to 3 and that seems to have corrected the problem. Logical as the flow capacity of the 3 inch should be more than twice that of the 2 inch.

    The O-200 temp probe picks up the oil temp before it goes through the cooler, so I don't really know what the actual oil temp is going into the engine. Rusty tells me that Lycomings are different and the oil temp is taken after the oil passes the cooler. Since small continentals did not have oil coolers, I'm wondering what my red line should really be as the airplanes they were used in typically had a way to blast air on the kidney tank cooling the oil before it went to the temp pickup point. Thoughts? Bob


    • #32
      The DAR told me if I had too high oil temps to consider changing out my Tempest oil filter with a Champion. He had that problem and it dropped his temps by 20 degrees. I said, thanks for the info, I just bought a case of Tempest. Donna


      • #33
        Bob, I think many are missing the knowledge passed on from the past. I have the cooling passage baffle on my engine and a Venturi lip on the fire wall. Both have been used to aid cooling by directing and extracting air flow . Stinger
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        • #34
          Very nice, Stinger. Based upon Rusty's recommendation, we extended the cowl below the bottom of the fuselage a couple of inches instead of opening the bottom of the cowl at the tunnel and using a lip. Clearly that has worked well for us as the CHT's have been kept quite low. I talked to Bob Barrows and he said he did not think that technique increased drag significantly. I really don't want to introduce air into the low pressure area below the engine because that would reduce the pressure differential and cause reduced air flow from top to bottom across the cylinders, possibly resulting in a CHT problem that I don't have now.

          My point really was that by picking up the oil temp at a point upstream of the oil cooler, I'm really measuring the temperature of the oil coming out of the engine instead of the temp of the oil going in. The old way of cooling the oil by directing air to cool the oil tank and using no oil cooler results in measuring the temp of the cooled oil. Of course I'm measuring at the same place but without cooling the tank so if I then get a 30 degree drop with the cooler, I don't have a problem at all, and never really did, it seems to me. I need to figure out how to measure the oil temp downstream of the cooler to be sure, though. More to come. Bob


          • #35
            Because of meetings and weather I did not get to fly until Friday of last week, but Rusty was kind enough to modify the air passage to the oil cooler for 3 inch scat tube instead of the 2 inch. He test flew it, and I flew it Friday and Saturday. We did not have any really warm weather, but I really think the problem is solved. Yesterday, I did a full performance climb to 9,000 and the oil temp never went above 185. Thankfully, the CHT's stayed in the green, also. Bob


            • #36

              I finally got 40 hours on my airplane and moved it to its permanent home at the Tuscaloosa, AL airport. I'm very appreciative of Bob Barrows for a great design, and Mark for a great kit. Most of all though, I'm greatful to my friend, Rusty (pilot, A&P, Tech Advisor), for all his help in getting to this point.

              My plan now is to continue testing while enjoying flying the airplane. I want to determine the rear CG limit for my airplane through actual testing. I have discussed methodology with Bob Barrows and I am satisfied that I have a sound plan. I will report results periodically as I progress.

              I would be be remiss if I did not mention how helpful this forum has been to me in making decisions about what I wanted, so thanks to all. I hope that anyone passing through the Tuscaloosa area will contact me and visit.

              Bob Way


              • #37

                Congratulations on completing your Phase I hours... Could you share (at least in general terms) what you and Bob Barrows discussed about how to explore the aft CG limit testing? It's something that I've had a lot of questions about, and haven't found many "answers". Not that I need the information right away - I'm still a long ways from flying, darn it!
                Jim Parker
                Farmersville, TX (NE of Dallas)
                RANS S-6ES (E-LSA) with Rotax 912ULS (100 HP)


                • #38
                  For AFT testing, I'm going to put sand bags in a military duffle bag that I can strap in the back seat. I'll increase weight 50 lb at a time until I can feel I'm approaching the limit, then use 10 lb at a time increases. At each step, I will check stability in all phases of flight, so this may take a bit of time. Bob


                  • #39
                    Originally posted by bway View Post
                    For AFT testing, I'm going to put sand bags in a military duffle bag that I can strap in the back seat. I'll increase weight 50 lb at a time until I can feel I'm approaching the limit, then use 10 lb at a time increases. At each step, I will check stability in all phases of flight, so this may take a bit of time. Bob
                    That's pretty much how I did in it the 4-place I flew except I used water jugs. Make sure you secure the sand bags really REALLY well. I thought I had the water jugs secured well but when I found my aft limit and things got pitchy a jug came lose making things a bit more exciting. I ended up having to make a new baggage floorboard because it got bent so bad.

                    I'd suggest sneaking up on the aft limit a tenth of an inch at a time.
                    Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.


                    • bway
                      bway commented
                      Editing a comment
                      I thought about using water, but I thought the duffle bag could be strapped in better with sand bags in it. Thx, Bob