I built it per your instructions, 6 cell 110 mah NIMH battery, etc. The finished weight was 3-ounces.

From : Don Stackhouse

3 ounces is OK, but getting into the "slightly chunky" category when flying with only 6 cells. It should fly OK at that weight, but lighter would definitely be better.

The one thing we can suggest that will make a HUGE difference is going to a 7-cell pack. We've found that although a well built and well flown model can do OK on six cells, the extra power of a 7-cell pack makes the whole situation much more forgiving.

Also, do an RPM check to make sure your batteries are delivering enough power. With a full charge, you should get at least 5000 to 5100 prop RPM, and about halfway through the run you should get about 4900 to 5000 RPM. If not, then probably your batteries are either worn out, damaged from improper charging, or were no good to begin with. We've found one particular brand of 110 NiMH cells that perform better by a large margin than anything else we've tested, and that's the brand that we sell. If you're using those, you should be OK, but it's still possible to have thise not deliver if they've been charged at too high a rate (we find that the Sirius 200 charger at 200 milliamps works great, but if you start pumping 500 milliamps charging current or more into these little cells, you could damage them).

I had mixed results flying your model airplane for the first few flights. I do not have a place to fly it indoors so I do not get a chance to fly it often outdoors.

I have made some changes that made your model kit much easier to fly. First I left off the wooden spinner, I needed all the power that I could get, and it still looks good flying.

The spinner doesn't really have a measurable effect on performance in our tests, but it is sensitive to getting damaged easily. Leaving it off for flight certainly won't hurt performance, and will keep the spinner looking nice for display.

Later I removed the landing gear, this gave the model better wind penetration.

That can definitely make a difference. The other thing to check for is loose wires, etc., from the radio gear hanging out in the breeze. Keep all that loose stuff taped neatly up against the underside of the wing, out of the freestream airflow as much as possible.

The model still did not handle very well in the air so I removed the linkage to the rudder. With a fixed rudder I had very good results. Now my BF 109 flies very well.

Interesting. Our experience with no rudder has been poor, lots of problems with adverse yaw. The Me109 does have a relatively long tail moment arm, which helps that situation somewhat. You might also have too much control throw, resulting in overcontrolling and a big increase in drag form that. The loss of control authority from locking the rudder could help that, even though it hurts in other ways. Try setting up dual rates on your transmitter with about half as much travel and see if that helps.

The long-nosed models, particularly the Me109 and the Mustang, are especially sensitive to the drag that comes from excessive control inputs. The long noses hurt the yaw stability, and the resulting yaw creates massive amounts of fuselage drag. If you don't have the rudder set just right, the plane is flying yawed to one side all the time, which is another big performance killer. With the rudder functional, try turns to both the left and the right. They should be identical. If the nose looks like it's yawing to the outside of the turn when turning one particular direction, then you need to adjust the rudder in the other direction until turns are equal both ways (i.e.: if the nose yaws to the right while making a left turn, you need to adjust in some left rudder at the shrink tubing sleeve on the rudder pushrod, leaving the aileron settings unchanged).

Don Stackhouse
DJ Aerotech