Source: 2020 Q4 Beartracks, Karl Clifford
My son, Jeffrey, purchased a four-place Bearhawk Quick Build Kit #82 in 2009. The Kit had originally been purchased in 2007 from AviPro Aircraft, (now Bearhawk Aircraft) by someone else, who had not even uncrated the kit. I have been Jeff’s helper in building the plane over the last ten years. The airworthiness certificate was finally issued on July 2, 2020. N976JC flies great. The engine is a new Lycoming YO-540-A4D5 rated at 250HP. Propeller is a constant speed two-bladed Hartzell carbon fiber. It has a Vetterman exhaust, a JPI EDM-900 engine monitor, and a Garmin G-5 electronic flight instrument. Empty weight came in at 1480 pounds. Very simple.
The only meaningful changes from the original design are a large skylight, a 2 inch extension of the fiberglass nose bowl to accommodate the very long neck on the Hartzell prop hub, and rigging the flaps so they can go negative about 4 degrees to achieve a slightly faster cruise speed.


We have flown it about 50 hours. The performance is unbelievable. While we have not fully mastered its STOL capabilities, we have gotten takeoffs and landings down to around 300 feet, with room for improvement I believe.
Jeff and I are both fairly tall guys, and with the seat all the way back we could not reach the flap handle without loosening our shoulder harness and leaning way forward and down. Not something we wanted to be doing when flying low and slow. So we made a short T-shaped grab handle that swings back from the flap handle that allows us to easily get the first notch of flaps without leaning way down. We can then easily reach the flap handle itself for subsequent notches. We also modified all flap notches so that the top button does not have to be pushed to pull flaps. The top button is pushed only to lower flaps. We like both of these changes.
The only real “problem” we encountered was high CHTs. We went thought a number of changes to the baffling before we finally arrived at what seems to work best. I would like to briefly describe what we ended up with so that subsequent builders might benefit from our experience. I suspect a fair portion of our problem was due to trying to break-in a new engine in the hot summer temperatures of West Texas. While we were flying mostly in the early morning hours, the OATs were still in the 80s and low 90s mostly.
During the engine installation we had very carefully installed the Van’s baffling kit for the 0-540 per Van’s instructions. It is a quality kit, well worth the money. We had very tight baffling.
Initially the CHT on takeoff for #2 cylinder (left front) and #5 (right rear) would go way over 400º F on takeoff with only a very short climb out. The CHTs on the other cylinders were also high, but not like #2 and #5. We would be pulling back the throttle to about 50% power very soon after takeoff to keep CHTs down. Of course, the Bearhawk still climbs out nicely even at only 50% power. We understand that the very rich fuel flow with full throttle helps cool the cylinders, hence the reason for normally taking off and climbing out with full throttle. But that was just not working for us.
The first thing we did was to increase the size of the opening at the bottom rear of the engine cowling to hopefully increase airflow over the engine. That helped a lot. Mark Goldberg had told me back during the building process to make that opening “plenty big”. Wish I had really taken that to heart. Make it PLENTY BIG. But that was not enough to totally solve the problem.

The next thing we did was to round out the bottom edge of the firewall with a rolled piece of aluminum sheet. The photo to the left shows the enlarged opening and the rolled sheet exit. I had read that the Van’s RV builders do this a lot. I was surprised how much this helped. Funny how moving air does not like sharp corners. But that was still not enough to solve the problem. I would mention that I later saw a similar rounded edge on the bottom of the firewall of a recent model Husky. So I guess the experts also think this helps.
Next we fabricated and added little inter-cylinder baffles on both sides of the barrels of the middle cylinders. These inter-cylinder baffles did not come with the Van’s baffle kit. A lot of air flow was being lost through these openings between the cylinders. Closing these openings helped. At this point the CHTs on all cylinders except for #2 and #5 were down in an acceptable range.
Next we looked at the #2 cylinder (left front) more closely, We theorized that the upward moving prop on the left side was pushing air up and back over the top of the #2 cylinder, mostly missing it. There is a lot of extra room inside the cowling above the #2 cylinder. Using aluminum sheet we added a simple “ceiling” in the tunnel running from the opening in the nose bowl back to just above the #2 cylinder. The ceiling begins just above the top of the opening in the nose bowl and extends straight back with a downward lip at its rear to force air down toward the #2 cylinder. This largely solved the CHT problem for the #2 cylinder. Our theory that the CHT problem with the #2 cylinder was being caused by the upward moving prop pushing air up and back over the top of the #2 cylinder seems to have been correct. That theory seems to be further supported by the fact there was not a similar problem with the #1 cylinder (right front). The downward moving prop on the right side pushes the air down and back directly into the #1 cylinder, not over it. So the right side seems to function fine without a ceiling in the tunnel. I would mention that a part of the problem with the high CHT on #2 cylinder is that it has the hottest EGT at all throttle and rpm settings. Nothing we can do about that. We did check for an intake manifold air leak, with none found. This hottest EGT is just due to the way the air/fuel mixture is distributed in the intake manifold among the cylinders. It does make the need for adequate air cooling for the #2 cylinder that much more important.

Next we looked more closely at the #5 cylinder (right rear). The location on the engine case of the #5 cylinder is staggered forward somewhat and the rear baffle behind it is set back several inches from the cylinder so as to be in line with the rear baffle for the left side of the engine. We theorized that the air was to some extent flowing over the top of the #5 cylinder and missing it, and that something was needed to force all the air down toward the cylinder. So we added a new “false” rear baffle located just behind the #5 cylinder that curves upward and forward to catch and force all the air down toward the cylinder. That new false rear baffle extends up all the way to the top of the engine cowling and has a gap seal at its top. We did leave a fairly small opening at the far right side of the false baffle to allow some air to flow on back to the 4” scat tube opening in the right rear baffle that leads to the oil cooler located behind the right rear baffle. This false rear baffle solved the CHT problem for the #5 cylinder. We had some initial concerns that it might create problems for the oil cooler. But we’ve noticed no increase in oil temps. The oil cooler continues to work great, with oil temps rarely going over 200º F.

We managed to get all of these changes made before OATs cooled off too much in the fall. With 90º F OAT we can now takeoff and climb out without any CHT going over 380º F if we don’t extend the climb out too long. Even with a more extended climb out all CHTs stay well under 400º F. At cruise all CHTs are down below 375º F and the spread among all cylinders is only about 20º F. On a cooler day CHTs are much lower. In cruise we can now lean the hottest EGT to over 1300º F. Before these changes we could not lean at all. Some of the improvement is undoubtedly due to the break-in of the new engine, so we cannot give total credit to the baffling additions.
It would have been much easier, and made for a much cleaner installation, if we had made these baffling additions during the original construction process, rather than adding them piecemeal as we ended up doing. So, I’d recommend to anyone currently building that he or she consider incorporating these additions to the baffling initially. Feel free to contact me if you have any questions or comments. Karl Clifford, Lubbock, Texas.
806-470-1480 4636c@att.net