This is a relatively simple model that shouldn't present any difficulties
to a person who has built a kit or two.
fuselage consists of four laser cut balsa pieces that make two sides to be
laminated together. Hardwood motor mounts fit into pre-cut areas.
A plywood doubler is glued on to each side and that's it for the fuselage
construction other than sanding and drilling holes for the gear, engine and
As I mentioned, I was concerned about the model being tail-heavy so I
sanded as much wood from the back end as possible. I also sanded the
fins as thin as I felt I could get away with.
The kit also includes two aluminum plates to space the engine and prevent
the bottom of the engine from bottoming against the plywood doubler.
These must be drilled to match the engine mounting holes.
The wing is the same
diagonal rib construction as all other DoodleBugs. It is simple to
build, light and very rigid. The ribs have a 1/8" square cut-out in
the leading edge. The plans indicate that a 1/8" sheet is glued into
these notches and then a stick is glued on the top and bottom to create the
full leading edge.
The kit goes the more conventional route of just having a single stick
for the leading edge. The notches aren't utilized. I placed a
1/8" carbon fiber tube in the notches to help me keep the wing straight
while I was building it. I removed the tube before gluing the leading
edge in place.
The only "problem" with building this wing is when sanding the leading
edge of the ribs flat for the leading edge to be glued on. The ribs
pointed away from the direction I sanded tend to deflect instead of being
sanded. The ribs pointed against the direction I sanded tended to
Some of the ribs meet at the leading edge so I glued them to minimize
this tendency. I also attempted something I've never done before.
I added cap strips to the ribs before the leading edge was glued in place
thinking they would stiffen the ribs somewhat to make sanding the leading
edge of the ribs more effective. While it worked regarding the
sanding, it was also more difficult to glue down the cap strips than it
would have been to sand the rib leading edges.
After gluing on the first couple caps, I decided to just sand a couple
ribs at a time using an up and down motion rather than a spanwise motion.
You don't have to sand the leading edge of the ribs at all, but the plane
will look better if you do and it will give more gluing surface to hold the
leading edge on.
The plans indicate that a tip weight box is built between the last two
ribs of the right wing panel. No drawings or instructions are provided
so you're on your own here. Do yourself a favor and build the box
before you glue on the cap strips. It will be much easier that way.
John indicted to me that the model needs at least 1-1/2 ounces of tip weight
so I epoxied that amount of lead shot into the box while I was building.
The box I built could easily hold another 6 ounces of lead which is tons
more than will actually be needed. the plywood cover is held in place
with four #1 sheet metal screws and washers.
The wing tips are three layers laminated together. Each layer is
two pieces that can either be joined before they are laminated or at the
same time as they are laminated.
There are blocks added to the wing tip at the leading edge but they don't
quite come up to the outline of the rib so I added a piece of scrap to
finish them off.
The trailing edge sheeting is wider than the tip at the trailing edge so
I trimmed the sheeting to match the tip. I thought it made the wing
look better and it's more than strong enough, so losing a little sheeting
didn't hurt anything.
shear webs between the trailing edge sheeting in the areas where there
is the least rib support. I went ahead and added webs for the full
One thing that concerned me was the lack of support for the wing tips
between the leading and trailing edge. My experience with the last
DoodleBug that I built was that I really had to pull hard on the covering to
get it to conform to the thick wing tips. The same was true for this
wing, but the tips didn't bow in like I thought they would.
As I mentioned, the
control system installed in this model is not what comes in the kit.
It is a system made by Tom's Building Service consisting of U-shaped wires
having brass bearings and steel horns brazed on. The pushrods are
carbon fiber with 4-40 rod ends and 4-40 helicopter style ball links.
The carbon fiber rods are wrapped with what looks like Kevlar thread and
coated with glue. They are very nicely done.
The bellcrank is phenolic. Overall it's a monster system that
should survive anything short of a nuclear blast. I still managed to
find a way to foul it up though.
By not consulting the plan before installing the system, I installed it
on the wrong side of the model. When I started hinging the flaps, I
realized the flap horn had been brazed backwards. After freaking out
for a suitable period of time I realized the horn was fine
— it was me that was backwards.
The nice bellcrank
mounts I built had to be hacked up so that I could move the bellcrank to the
left side of the plane (as indicated on the plan).
For reasons I can't remember now, I had to change the way the bellcrank
mounted when I moved it over. I had originally cut spacers from an
aluminum bushing I had. When I moved the bellcrank I used bearings
from the inside of a Zip disk instead. I played around with it for a
while before installing it and was very pleased with how it worked.
The Zip disk bearings have a coating on them which allows the bellcranks
to rotate smoothly. The bearings are large in diameter and completely
prevent the bellcrank from rocking.
Note that no materials for mounting the bellcrank are included in the
kit. All you need is a small amount of 1/8" aircraft plywood.
Learning from my mistakes, here's what I suggest you do. Cut four
platforms the shape shown on the plan. Measure the distance between
the spars. Measure the distance top to bottom of your bellcrank.
Subtract 1/4" (the thickness of two plywood plates) and divide the number
you have left by two. That's how thick the balsa spacers between the
spars and the mounting plates should be.
Assemble the whole
thing outside the model and then insert it into the wing. Adjust as
necessary before gluing it all in place. I strongly suggest that you
Loctite on the bolt for the bellcrank when you install it for the last
time (which must be before you add the last piece of wing center sheeting.
And don't forget to hook up the lead outs.
You'll probably have to cut away some of the plywood platforms to get
full movement without interference. I also had to open up the cut-outs
in the ribs to allow free movement of the lead outs. In fact, there is
no reason for the rib cut-outs to be so narrow. A lot more balsa can
be removed from all the ribs which is what I plan to do when I build mine.
Also note that there is a left and right flap. The elevator pushrod
is connected to the flap pushrod. The left flap has a cut-out to clear
the elevator pushrod.
I used five Dubro medium
hinges to hinge each flap. Notches are laser cut into the flaps
where the hinges go.
The flap horn and elevator horn have brass bushings on them which I cut away carefully using
an emery wheel in a
Stabilizer and Elevator
These two pieces are huge! The balsa included in the kit was nicely
selected having appropriate grain and weight. Both pieces were about
as flat as a sheet this size is going to be. They weren't bowed,
cupped or warped.
About all you have to do is hinge them and install the control horn.
I inset the wire joiner and used ten Great Planes hinge points which are
larger than the Robart small hinge points (having plastic hinge pins) and
the standard Robart hinge points which would have been too large. The
Great Planes hinge points have a metal hinge pin.
I sanded the elevator and stabilizer for a very long time to remove as
much weight as possible. I left just enough thickness so the hinges
had a little material on top and bottom and wouldn't break through.
The only other work necessary is sanding the edges straight and rounding
over the leading edges.
I don't think it would be a bad idea to taper the elevator. This
model did come in tail heavy so removing that much more material would be