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Wednesday, October 19, 2016

Will Hobby FW 190 Butcher Bird

Shown below with an Irvine 120 2 stroke installed using the radial mount which was supplied by the manufacturer. The engine is attached to the plywood and oak sandwich spacer by 3 number 10 rubber well nuts providing a measure of vibration isolation to the installation.

With the batteries still to be installed the model balances about an inch behind the recommended center of gravity location which is indicated by the line made with a black felt marking pen. At this point I am estimating that a pound or so nose weight will be required before I will attempt to fly it.
Since writing these words I this model has successfully completed its maiden flight. I took the model to the flying field yesterday together with its forty five year stable mate; another FW 190 A which incidentally is a very good flyer with many flights logged over the years. The plan was to have three or four flights on the trusted 190 then switch out the flight battery and satellite receiver and install them in the new model, then do some serious shake-down testing. It all went so well when she became airborne on a high speed taxi run and rather than abort at 10 feet altitude 
 we decided to do a few circuits of the field and land. The landing was controlled into a 12 kilometer headwind with 15 degrees of flaps, so the touchdown speed was quite low with a gentle sink rate. To my surprise the port landing gear unit separated the wing cleanly and the plane slid to a stop on one wheel. I was prepared for the eventuality that reinforcing would have to be made.  I have already filled the area with gap filling foam to help stabilize the built-up structural members; its a trick that I often perform for high stress areas and the results have usually been quite positive.
During what was to be a high speed taxi test the plane became suddenly airborne and the decision was made to do a circuit and land rather than to abort from 10 feet altitude.

The gap filling foam can be seen in the picture below as well as the pathetic glue area for securing the gear retract mounting beams.

The area was hollowed out for full depth (surface to surface) oak beams for mounting the retracts. The beams were then epoxy bonded to the foam filler that was injected and cured place. A set of servo-less electric retracts was installed on the oak beams. The retracts were drilled out to 3/16 (4.45 mm) diameter and 3/16 inch drill rods were inserted as landing legs.

 All my flying buddies are seriously into gas power for their models; they say give up on your big fuel guzzling glow engines and switch to a gasser that runs reliably on pump gas and save your money.  With these arguments in mind I decided to replace the big Irvine 20 cc glow engine with a DLE 20 gas engine. It didn't work out as easy as that for me. I discovered the hard way that this engine will not run at factory needle settings. That fact was learned after 2 years of on and off effort on my part. I must say that I got lots of free advice like: throw away the factory plug, its garbage; the spring under the plug attachment has to go too, its also garbage; you have to have two lines to the tank, get rid of the filler tee in the fuel line; your engine must be inverted it won't run upright like that. In the end none of these suggestions mattered because the engine just wouldn't run..

The one pound nose weight is shown below and the plan is to have it easily removable so that it can be removed when the engine cowl is attached (Center of Gravity location maintained).

The idle adjustment screw is shown below.
The high speed mixture adjustment screw is pointed out below.
The low speed mixture adjustment screw is pointed out below.

The quest to find the secret to good running DLE 20 engine continued for almost two years. I would try something, get frustrated, put it away, then try another approach all to no avail. In the end I decided the engine was flooding, so I set the low needle to 1/2 turn opened and ran a temporary fuel line from the Jerry can to the carburetor. Put the electric starter to the prop nut and the engine ran smoothly; all be it,  with a high rpm idle. Then it was just a matter of switching to the regular fuel line, opening the low speed needle, a degree or two at a time until the idle speed was acceptable. There was nothing wrong with my single fuel line system with the filler tee, or the engine upright configuration; it was just a matter of the low speed needle settling allowing too much fuel to be ingested by the engine and fouling the plug.

The canopy is not correct and I am looking for the least intrusive (minimum work) method to make it look right to my eye at least.

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