HOW TO CUT AN ENGINE COWL
Submitted by Cecil ColumnWhen I first started building model airplanes I was terrified of cutting a cowl for the cylinder head and other necessary openings. I can't relate how many ideas I tried with very limited success at doing this task in a satisfactory manner but after a few hundred attempts, I found a method that WORKS!
I will attempt to explain this method, for which I can make no claim of originality. I don't know where, when or who introduced me to it but I owe that person a big thank you. His method makes life much easier for those of us who attempt to fabricate replicas of various aircraft and we end with a creditable looking cowl. This method can be adapted to other uses, I'm sure. Don't hesitate to use it, it works.
We will be working on a .60 size CAP 232 that I rescued from the trash can about six years ago. It was crashed at an IMAAC practice round but the owner had intended to fly it in the competition. The engine is a K&B .61 two-stroke with a Perry carburetor. Photo #1 shows an engine box built to move the thrust washer far enough forward to mount the cowl.
Once your plane is ready to mount the cowl, you can determine it's approximate location on the fuselage by measuring from the back of the thrust washer or spinner backplate to the firewall. Deduct 1/8" from that measurement so that the cowl doesn't rub the backplate. Now lay the cowl open end down on your workbench and measure the overall length to the propellor opening. Subtract one from the other and that will tell you approximately how much the cowl will lap onto the front of the fuselage. This will be so close that you will probably not have to move it when permanently installing it.
Next, cut strips of light cardboard about two inches wide and long enough to enable you to tape it to the fuselage BEHIND the farthermost position the cowl may reach and to reach the glow plug, needle valves, etc. These strips must be bent behind the tape so they will be out of the way when the cowl is installed. (See photo # 2)
Once you have the strips bent and taped to the fuselage, bend them down ONTO the object for which you need the opening in the cowl. In the case of a cylinder head, I normally mark the electrode on the glow plug IF it is centered on the head. Not all are, so in that case one needs to mark around the cylinder itself.
Do the same for all the openings then cut any hole needed in the strips WITHOUT REMOVING THEM FROM THE FUSELAGE! The strips MUST stay taped to the fuselage. If the glow plug is centered or close to center in the engine head, I will drill a small hole in the cardboard strip as a locator (See photo #3).
Editor's Note:
Last month I sent an email to all club members explaining
that I would need to cut the newsletter short because I was finding it difficult to find something about
which to write. Several members, and a few others as well, have contributed articles since that email.
Cecil Column has offered an excellent "How To" article on the cutting of cowls, which allows us to "do
it right the first time", and Charlie Bell has contributed an equally excellent article entitled "Vertigo",
which deals with full scale pilots.
Thanks one and all for those articles. Temporarily, at least, things will continue as before.
Landing
Have you noticed that some pilots seem to have absolutely no trouble landing in the center of the runway,
right in front of them? And they do it repeatedly!
To gain this landing proficiency, always fly a "downwind" leg, a "crosswind" leg and an "approach" leg.
It is done this way:
STEP ONE: Fly the downwind leg offset from the runway about 100 to 150 feet (but parallel to it) and
at about 100 feet altitude and aproximately 1/2 throttle. Fly past the "threshold end" of the runway about
100 to 150 Feet then reduce throttle to about 1/3 and make a gentle 90 degree turn toward the runway. ONLY A 90
DEGREE TURN!
STEP TWO: (Your aircraft will be descending due to the reduction in throttle you have just made.) Fly
this 90 degree (crosswind) leg until you cross an imaginary line that would be an extension of the line formed by
the far side of the runway and make another 90 degree turn toward the runway.
This will put you on the "approach" leg. With a little practice you can get it right so that when you
roll out to wings level on the approach you will be centered over the runway and at about 20 to 25 feet high.
STEP THREE: You may still need to fly some distance to the threshold or you may not - it depends on when
you began the turn to crosswind and how gentle your two 90 degree turns were. If you need to stretch the
landing just add a slight bit of throttle (again - no elevator yet) or if you are over the runway reduce throttle
to "idle". The plane should descend smoothly but still well above stall speed. Just about one foot
or so above the ground gently pull back the stick (this is the only time to use elevator during landings except
for emergencies) SLIGHTLY -- not too much -- to flare the plane. The plane will want to hold off the runway
due to "ground effect" but just wait -- it will settle down to a smooth touchdown and rollout. Then, if you
are flying a "tail dragger" pull full up elevator to keep the tail planted and increase throttle to taxi speed
and steer with rudder.
REMEMBER!! Taxi only off the runway then kill the engine and carry or roll the plane into the pits.
NEVER TAXI THE PLANE ALL THE WAY INTO THE PIT AREA AS THIS VIOLATES SAFETY RULES!
Editor's Note:
Last month I sent an email to all club members explaining that I would need to cut the newsletter short because I was finding it difficult to find something about which to write. Several members, and a few others as well, have contributed articles since that email.
Cecil Column has offered an excellent "How To" article on the cutting of cowls, which allows us to "do it right the first time", and Charlie Bell has contributed an equally excellent article entitled "Vertigo", which deals with full scale pilots.
Thanks one and all for those articles. Temporarily, at least, things will continue as before.
Landing
Have you noticed that some pilots seem to have absolutely no trouble landing in the center of the runway, right in front of them? And they do it repeatedly!
To gain this landing proficiency, always fly a "downwind" leg, a "crosswind" leg and an "approach" leg. It is done this way:
STEP ONE: Fly the downwind leg offset from the runway about 100 to 150 feet (but parallel to it) and at about 100 feet altitude and aproximately 1/2 throttle. Fly past the "threshold end" of the runway about 100 to 150 Feet then reduce throttle to about 1/3 and make a gentle 90 degree turn toward the runway. ONLY A 90 DEGREE TURN!
STEP TWO: (Your aircraft will be descending due to the reduction in throttle you have just made.) Fly this 90 degree (crosswind) leg until you cross an imaginary line that would be an extension of the line formed by the far side of the runway and make another 90 degree turn toward the runway.
This will put you on the "approach" leg. With a little practice you can get it right so that when you roll out to wings level on the approach you will be centered over the runway and at about 20 to 25 feet high.
STEP THREE: You may still need to fly some distance to the threshold or you may not - it depends on when you began the turn to crosswind and how gentle your two 90 degree turns were. If you need to stretch the landing just add a slight bit of throttle (again - no elevator yet) or if you are over the runway reduce throttle to "idle". The plane should descend smoothly but still well above stall speed. Just about one foot or so above the ground gently pull back the stick (this is the only time to use elevator during landings except for emergencies) SLIGHTLY -- not too much -- to flare the plane. The plane will want to hold off the runway due to "ground effect" but just wait -- it will settle down to a smooth touchdown and rollout. Then, if you are flying a "tail dragger" pull full up elevator to keep the tail planted and increase throttle to taxi speed and steer with rudder.
REMEMBER!! Taxi only off the runway then kill the engine and carry or roll the plane into the pits. NEVER TAXI THE PLANE ALL THE WAY INTO THE PIT AREA AS THIS VIOLATES SAFETY RULES!