When talking to the editor of this mag one day,
in passing I asked what plans that he had that
needed to be built and tested. John went through
a list of about half a dozen and the last on the
list was the Lightning, probably thinking that
I wouldn't pick that one. My ears pricked
up and after a few more details about it, the answer
was yes for the Lightning! I explained to John
that it would probably take me a year or so to
get it completed, because the reviews I also do
for airborne had to take a front row seat and the
Lightning would have to fit in around them. Well
it actually ended up taking two years, but I think
the wait was worth it!
The plan arrived and on opening the separate sheets
it revealed that it was the early P model, which
had the smaller swept back engine cowls. The plan
showed side mounted 46 two-stroke engines that
would stick out the right hand side of each cowl.
After a bit of thinking and knowing that I was
going to use the small for their size, Magnum AR
61 FS's, the answer was to mount them inverted,
but again they would stick out the front of the
swept back cowls. Now the only problem was that
they would stick out even further that the 46's.
After a few phone calls to John, he gave in and
let me change it to the later ' L ' model,
which had a larger frontal engine area, which would
completely enclose the motors. Having run these
Magnum engines inverted in most of the review planes,
I had no reservations about their reliability mounted
up side down.
The plane that I have copied is the Lightning that
was flown by the American Ace, Major Ted McGuire
Jr. He was killed in combat in the Pacific theatre,
trying to protect his wingman involved in a dogfight
with a Zero. McGuire banked his Lightning too steeply
and stalled the top wing and went into an unrecoverable
spin and was killed on impact. He had the second
highest amount of kills of all the P38 pilots,
with 38 kills to his name, before his untimely
death. The nose art on the plane is the nickname
that he had for his wife. Pudgy 5 (bet his wife
liked that!) was the last P38 that he flew.
Getting Started
Well let's get started on the building!
It is advisable to kit up your parts before you
start, so the photocopier ran hot to make up ironing
templates to transfer the images onto the balsa
and ply pieces. For those not familiar with this
technique, photo copy all the various parts of
the plan that need to be cut out of balsa or ply.
These photo copies can then be cut out and then
laid face down onto the wood and a domestic iron
run over the photo copy. The image on the paper
is then transferred onto the wood much the same
as one of those temporary tattoos we had from the
lolly shop when we were kids.
There is a fair amount of cutting involved and
on Fathers Day a nice little band saw arrived,
so it got a very good test out! The ribs were cut
in pairs, as was anything that had to be duplicated.
A few hours had me covered in balsa dust and the
parts ready for some building.
The centre section of the wing needs to be built
first and then the two booms and tail are built
over it using the jigs made from the plan. Each
boom and the centre pod, are built flat on the
plan over the wing and then once completed, turned
over and then the bottom sections are glued on
to complete the rounded shape. The horizontal stab
was built up and covered with 1.5mm balsa. This
sits in a pair of jigs that holds it at 0 degrees
to the datum line, while the wing needs to be packed
to 1 1/2 degrees of positive incidence. You will
need to get yourself a good incidence meter to
allow you to get everything lined up perfectly,
otherwise you just might create a dog of a machine!
Take your time with this part of the job, and double
check everything several times before committing
glue to the wood. I tended to use PVA for a lot
of this work, as it gave me a bit of jiggling time.
The balsa formers and spruce stringers then just
join up the tail and the wing, making sure to keep
them square over the plan. I completed each boom
before moving on tho the centre pod.
I had brought a set of spring-air retracts and
fitted them without too much effort. They were
all set up as firewall mounted units and this didn't
suit the boom installation. So I made up an aluminium
plate to bolt them to and then bolted the assembly
to the mounting plate. A bit of mucking around,
but the end result worked a treat. Once the retracts
were in the booms (under the wings), they could
be sheeted and the centre pod built over the wing
in the same manner as the booms. This is built
up using the building board surface with formers
and some spruce stringers, just like the booms,
whereas the booms are just sheeted with 3mm balsa,
the pod is tapered in all directions and needs
to be covered using the planking method. A bit
time consuming, but the end result is worth the
effort. The booms require the 3mm balsa to be wetted
out with liquid ammonia to allow it to follow the
tight curves at the tail end of the boom. I fitted
it in place and used thin cyano to hold it there,
before applying some PVA glue to permanently fix
them in place. I placed the sheet joins along the
stringers to help support them. A lot of time was
spent thinking out the best way to tackle things
as I went along. But better to waste a bit of time
than stuff the job up!
The wing end sections are made to be removable
to allow for easy cartage of the plane. These were
built over the wing plan and I put 2 degrees of
washout in each tip. This required the rear of
the tips to be packed up by 5mm, tapering back
to zero at the root. This will help prevent the
dreaded tip stall, both at high speed and on the
all important landings. The wing joiners on the
plan are just 3mm x 15mm bar iron and I replaced
them with high tensile 6006 aluminium bar of the
same size. These have worked fine, with no sign
of them bending in loops and rolls. I could see
this plane becoming too heavy if some weight saving
measures weren't taken. I did also cut sections
out of the ply motor mounting boxes and hollow
out a few ribs towards the wing tips. Trial fit
everything, and check it with the incidence meter
as you go along. This will save you from depression
after it rolls into the ground on its maiden flight.
While the wing ends were still pinned down, I sheeted
to top surface with 1.5mm balsa and made sure the
washout was still there as the glue dried. The
rudders were built up over the plan and sheeted
like the rest, with 1.5 mm balsa. A rough sand
had them close to the right profile for a final
finishing sand after they are attached to the plane.
SERVOS
With a total of 13 servos needed on the original
plan, I just had to see if I could bring the
number down without compromising the safety of
the plane. Originally it had 2-aileron servos,
4 flap, 2 rudder,1 elevator, 2 throttle, 1 retract
and 1 for a steerable nose wheel. I was able
to make up a piano wire linkage that would go
from the inside flap, through the boom and connect
into the outside edge of the outer flap. That
got rid of two! The rudder was just a matter
of fitting a pair of bell-cranks each side of
the rear edge of the horizontal stab and running
a wire across to connect them up together. Then
a pair of linkage arms made the rudders move
in unison with each other. Sweet! That had it
back to 10 servos. I was able to get a great
deal on some Hitec 225BB mini servos and they
have more than enough power to operate all surfaces
with authority. Now where to put them all?
I had my suspicions that the plane would turn out
on the tail- heavy side, but I fitted the elevator
and rudder servos mid-way down the right boom where
the dummy radiator covers would go. This was where
the plan had them! They stayed there until I was
about to fit the covers in place (more on that
later). The wing servos were screwed onto ply plates
and hatches cut out for them to fit into. The throttle
servos went underneath the fuel tanks and had to
be built in, so the throttle travel was checked
before the balsa covered them up. The retract servo
to operate the air retracts went as far forward
as I could get it in the nose pod and the nose
wheel servo was placed just in front of F2. Let's
get back to some more building now.
Cowls
The plan shows carved block balsa cowls and radiator
covers. Because there are two cowls and four
covers, I decided to head in the fibreglass direction.
A foam plug was made for each item and they were
covered with 2 layers of 6oz cloth and then wet
out with epoxy resin. They were then covered
with a mix of Q-cells and epoxy to fill and imperfections
in the surface. Once cured they were sanded back
with various grades of wet and dry sandpaper.
Now we had two plugs that some moulds could be
made from. I think these will be available as
a set with the plan and canopy in the not too
distant future. Even though it took a bit of
time, I still think that I would be still sanding
all those awkward curves if they were balsa.
Engine Mounts
The engine mounts went on the firewall with blind
nuts and high tensile bolts. The plastic mounts
required a section cut from them to allow the
carby to rest next to the firewall. This was
necessary to keep the proper length of the cowls.
I marked on the plan the position needed for
the firewall when using a four-stroke motor.
With the retracts in and operational, I had to
decide whether to put some doors on to hide them.
Last year a gentleman by the name of Rod Mitchell
attended the big Hamilton fun fly and swap meet
on the last weekend in November( free plug!)
Rod brought along his 'YippeeÓ P38
Lightning and thrilled the crowd with some precision
flying. I was able to have a good long talk with
him and he showed me his simple door actuating
system, using just fishing line and a few torque
rods to open them. Thanks Rod, because I really
had no idea how I was going to get them working.
Another option is to use a Robarts sequencing
valve which will control all three doors and
will save heaps of time and headaches.
Next issue we'll finish off the Lightning
then get to what most of us really like, flying.
Just as a teaser I'll let you into a secret,
it flies just great.
Go to Part
2 of construction article >>>
