the jig blocks was a piece of cake and took no time at all. I
bought some 42mm x 18mm pine lengths and began by marking off every 1"
across the width. By clamping a piece of scrap timber to the
drill press I was able to guarantee that every hole was the same
distance from the edge as I slid the length along.
||Now that I
had a stick with 2 rows of evenly spaced holes, all that was left to do
was cut the blocks. Once again I clamped a scrap piece of
wood on the mitre saw guide, 1" from the blade and with each successive
cut just flicked the block out and fed through more length.
drilled holes are a little wider then the screws allowing them to push
through easily. I didn't want to risk splitting the blocks
with tight fitting screws. Once screwed into the bench the
blocks don't move.
snapping a chalk line to get my first straight line, I set up a laser
level at one end of the workbench and marked every 18" or so along the
laser light with a black marker. The photo doesn't show how
bright the light was but I can tell you it had no problem illuminating
the 14' of the top longeron.
the blocks exactly to the lines I had marked, I knew the
freshly machined longeron was going to be perfectly
straight.........and it was.
marked on the bench where all the verticals would meet the top
longeron. I did this by hooking the tape measure at one end
and running it out the full length of the longeron. Then I
marked the distances between each vertical according to the plans.
I was very careful to add the distances properly and also
putting a "check" to the side so I knew which side of the line the
vertical was going to be placed on. After the "mark &
check" I held a set square up against the top longeron to draw the
give the lengths of only 6 verticals. Once these were cut and
in place, the bottom longeron was then held in place at the "nose" with
a block and then gently bent around the others, finishing at the tail.
According to plans, the bottom longeron goes in a straight
line to the tail. However, I have continued the smooth curve
by pushing the bottom longeron in 3/4" half way to the tail.
Again, using the laser level made this an easy task.
the verticals are measured and cut to fit between the top and
Here's a couple of tips. Set the saw to cut the mitre at
about 5 degrees and cut the end off a vertical. Do this first
and see if the cut is correct. Adjust the angle of the mitre
to shave more off until you are happy that the angle sits perfectly on
the bottom longeron. Note the angle of the mitre and write it
on the workbench so you know what angle to cut when building the second
side. Once this is done, just set the mitre saw back to 0
degrees and easily cut the top off to length.
|| To cut the
diagonals, I layed out a piece of timber making sure it was aligned to
the corners exactly as shown in the plans. Resting my "Pa's"
sliding bevel on the diagonal, I sighted the bevel to the vertical and
then marked the line to cut.
diagonal to saw! Once done, make sure the cut fits perfectly
in the upper corner and then mark the angle on the other end using the
sliding bevel. The angles on opposite ends of the diagonals
are identical, therefore you can use the same sliding bevel angle to
mark and cut.
closely at the plans, the diagonals to the front spar meet at the very
top of the capping. This makes structural sense.
The standard RAF48 spar height is 7.19" high but as I am
using the AS5048 foil at the root, the height of the spar is going to
be 8.19". Therefore I
changed the position of these diagonals to meet 1" higher.
timbers are now in place. All that is left to do is cut and
fit the rest of the gussets.
There is a very easy way to work out what angle they need to be.
how I marked on the workbench the angles I cut the bottoms of the
verticals at? First you just subtract this number from 90
degrees. eg. 90 - 5 = 85 degrees. Halve this number eg. 85/2=
42.5 degrees. This is the number you need to set on the mitre
saw. After cutting one angle, roll the timber over as in the
photo and perform the same cut again. 2 cuts of 42.5 degrees
add up to the 85 degree gusset needed.
the joints ready for the T-88 epoxy. I removed the jig block
slid the plastic underneath. It is then folded over the top
the jig block screwed back in. That way if any epoxy seeps
the joint, it won't make contact with the workbench or the block.
is what I got together to get started on gluing the fuselage.
T-88 epoxy and hardener, plastic cups, icy pole sticks which
cut off the rounded ends to help get the epoxy out of the bottom of the
cup. I also have a brush to apply the epoxy which turned out
be a useless applicator for the job as the epoxy has the consistency of
a thick syrup on a cold day. Applying with an icy pole stick
the way to go. Chemical resistant gloves and electronic
epoxy and hardener have to be mixed 50/50 by volume. This is
hard to judge given the viscosity of both. I chose to mix the
by weight. The epoxy is heavier than the hardener so they
be weighed at a ratio of 13:11. That is, 13 grams of epoxy to
grams of hardener. The scales are calibrated to .01 of a
So add an empty cup, zero the scales, add 13 grams of epoxy,
the scales, add 11 grams of hardener...........stir with an icy pole
||I left the
epoxy to cure for about 30 hours and then removed the nails
which had no issue with sticking to the timber or glue. After
removing some of the jig blocks I carefully lifted the fuselage from
the bench which came away like a cake from a well greased cake tin.
The protective plastic under the joints peeled off easily,
leaving a smooth film of epoxy covering the underside of the joint.
||It was a
real sense of accomplishment to finally free the fuselage from
the bench. To feel its weight and strength was a real WOW!
moment. In a few areas I used a light file to remove epoxy
had flowed onto the plastic leaving a bridge between the timbers, a bit
like webbing between your fingers.
||It was now
time for a cup of tea and to admire my handy work before
repeating the process all over again. It has taken a total of
1/2 hours to get to this point and this does not include the
construction of the bench. The fact that I will not have to
the plans, build and place jig blocks and just a better general idea of
what to expect, should decrease the build time for the second side.
second side is all glued up and now I'll let it cure for 24 hours.
It has taken a lot less time to build....under 11 hours which
includes 1 1/2 hours of machining the 5/8" x 5/8" lengths of timber.
waiting for the plywood to arrive I have decided to build a router
scarfing jig using a 3' length of pine from an old bookcase.
order to drill the holes perfectly to hold the router, I just sprinkled
sawdust on the timber, put some screws in the bottom of the router and
pushed down really hard. Sawdust stuck to the screws and left
imprints on the sawdust. Mark them with a texta and drill the
the router secured to the timber, I have added screws along the bottom
and bolts mid way up. The plan is to screw the jig to the end
the workbench and use the bolts to push it out to get the scarfing
get the 10:1 angle required for joining plywood together with a
scarfing joint, the jig needs to be angled back just shy of 6 degrees.
After screwing in the bottom of the jig, I use the sliding
set it to 96 degrees and screw the bolts through until the jig lines up
with the bevel. Screw in the rest of the screws and I am done.
gluing on the plywood, I sanded off the high spots where the glue had
gathered on the underside of the fuselage whilst drying.
plywood for the first time. Aircraft grade ply is beautiful.
It's smooth and there is not a mark on it unlike house
building ply. My local ply supplier only has 4' x 4' boards
so I need more joints than usual.
jig worked perfectly. Plenty of noise and plywood fibers.
these pieces of ply have had the scarfing done. When pushed
together, the joint is perfect on both sides.
outlining the fuselage on all 3 pieces, epoxy is applied to the ply and
the fuselage timbers as well. I then layed the fuselage on
top of the plywood and applied pressure.
want to use staples so used good weighty objects. The result
was fantastic and I don't have the hassle
of pulling staples and
filling staple holes in time.
fuselage side has these beautiful glue fillets where the timber meets
cutting the plywood initially I left a little overhang on all
sides because I knew I'd get a perfect edge using the router with a
flush trimming bit.
particular bit has a ball bearing on the very end the same width
as the cutting flutes. The ball bearing rolls along the
and the cutting flutes trim off the overhanging ply.
||I have used
the laser level to mark a straight line for the center of
the fuselage. As the widest part of the fuselage will be 40",
center line must be at least 20" and then a few from the edge of the
workbench. The tail of the fuselage must overhang the bench
allow room for fitting of the vertical stabilizer. I will
temporarily widen my workbench for the bending of the boat.
||As seems to
be common practice, I will be moving the widest part of the
fuselage in line with the shoulders when seated. This
behind the rear wing spar and slightly closer to the vertical aft of
there. This improves pilot and passenger space.
widest part to the aft edge of the wing instead of the middle also
improves aerodynamic drag over the upper surface of the wing.
the first two blocks exactly where I want the fuselage to be
and the one down near the tail is about mid way to where the tail will
eventually be bent to.
|| Here you
get a better idea of how far I need to bend the tail around.
|| Slowly and
gradually I bend the fuselage so as to get the tail end over the jig
block. No "snap" noises here.
bending I secured the bottom (top longeron really) to the
workbench with a few blocks as it wanted to lift itself up and over the
jigs. The top of the tail wanted to bend outwards, so I used
tent guide rope to pull it over to vertical, securing it to a screw in
the workbench. I'll bend the rear of the fuselages around bit
bit over the next week to give the timber time to take up the curved
form gradually. Hopefully this will avoid stressing the
too much, too quickly which can lead to snapping.
||Like I have
said before, space in a single car garage is a premium so I added the
workbench "wing" at this stage for the setting out and gluing of the
boat. Its construction is covered in the Bench section. Once
completed, I will remove the "wing". The second fuselage side
has been set out identically to the first.
||It's been a
couple of days and not much to show but a more bent fuselage. I did
however machine more timber for the next stage. Gradually
it has taken its final shape. I am widening the
to 40" at the shoulders and after much thought and input from the KRNet
guys, I have decided to keep the same "narrowed in" shape as the plans
and widen the top and bottom of the boat the same number of inches,
except the firewall which remains the same dimensions as standard.
The other option was to make the fuselage perfectly vertical.
finalize the bending of the rear of the fuselage, I have used
trigonometry to calculate the cutting angles for the cross members.
Remembering the fuselage is upside down on the workbench, the
bottom of the fuselage is narrowed in which means the cross members
need to be cut at angles to match the angle of inward tilt of the
fuselage. The formula for this is TANě = 62
which equals 7.01o. You can use the
formula if you like or use an online
triangle calculator like I did.
My maths isn't what it used to be.
||So I have
calculated the cross member angle cuts for the narrowing in at the
bottom of the fuselage, but it also narrows in towards the
firewall which means I now have to calculate that angle too.
Use the online triangle calculator again, or if you want to
to your friends the formula is SINě
= 47 ¸ 1200, which equals 2.24o.
angles I have calculated, I can now set the compound mitre saw to cut
both at the same time. Like the picture shows, I rotate the
mitre to 7o, and tilt
the compound over to 2╝o
is perfect. As the bottom and top longerons together are
straight from the firewall the to forward spar, these cutting angles do
not change even though the cross members get longer. I
will use the same method for the straight section from just
aft of the rear spar to the tail. In between, I'll have to
take a few individual measurements. Using the calculator and
a compound mitre saw removes the "hit and miss" approach to cutting
these difficult angles. It's easier and quicker than I have
made it sound here so give it a go.
cutting all the bottom cross members I marked each one with a line at
exactly center and secured them in place with sash clamps.
to see how straight the boat was, I lined up the laser level along the
center line marked on the workbench and to my surprise it didn't need
too much straightening. 3/8" out at the front and 1/4 out of
at the tail.
||I used my
trusty tent guide ropes to "tweak" the fuselage into alignment and then
went on to cut the necessary gussets.
decided to use the icy pole sticks and clamps to apply pressure to the
gussets while the epoxy cured. This method was very
the epoxy had dried, I removed the clamps and the icy pole sticks flew
all over the place like released springs. I did re-glue one
member near the tail as the gusset had slipped over night and wasn't
making good contact. After cutting the offending
the cross member and sanding the joints back to timber, I epoxied it
all back together. Now I am happy with the joint.
the sides of my fuselage are tilted in as per the plans, the bottom
longerons meet the flat bottom of the fuselage at a slight angle as can
be seen when using a straight edge. So that the plywood when
glued can remain flat right to the edge, the slight angle
be removed from the longerons.
electric plane made the job very easy. I set it to a depth of
.4mm and gradually planed the longerons, checking them for flatness
with the straight edge as I went.
fitting the plywood skin, the bottom engine mount rail and compression
brace need to be cut and epoxied into place. After clamping a
piece of freshly machined 3 1/2" x 5/8" hoop pine into position, I
scribe with a pen on both ends where the cuts need to be made.
Using the angles calculated earlier, I was able to make
cuts with the compound mitre saw.
and clamped into position, the plywood skin will be ready for fitting
in 24 hours. But only after lightly planing the bottom edge
the engine mount rail to match the curvature of the longeron as you can
see in the photo above.
plywood has been cut to size with a 1/4" overhang on the sides which
the router will cut to a crisp edge when dry. I nailed the
where it had to go and then crawled into the fuselage, layed on my back
and marked with a pen around the cross members and along the longerons.
This tells me where to apply the epoxy on the plywood.
epoxy has been applied, I secure with weights and 1 1/2 mm nails at
strategic points and let cure for 24 hours.
big moment has arrived where I get to flip the fuselage over and view
it the right way up. Before removing the jig blocks, I
scrap timber between the top longerons to avoid any flexing movement.
I have to say it's lighter than I thought and quite stiff.
on the bench, I was able to closely inspect every joint and piece of
timber from the inside. Both top longerons have cracks in
them at the widest part of the fuselage. I am in two
as to how to go about the repair. The damaged section of
will need to be replaced and a new section will have to be scarfed in
with the joints over verticals. That is a given.
have already started bending a new piece of 5/8" timber but am giving
thought to bending 2 x 5/16" lengths and laminating them together.
I'll give it some thought over the next couple of days.
have decided to laminate the hoop pine to replace the cracked longeron
sections but before cutting them out, I need to jig the top of the
fuselage like it was when inverted on the workbench. This is
it will hold shape when the cracked sections are removed.
have used the 4' x 4' x 1/4" plywood intended for the firewall and also
some bookcase shelves. The timber props inside the fuselage
the sides from bending in.
the plunge router with a straight cut bit and the adjustable guide, I
shaved off a little timber at a time until I was sure I could sand the
remaining area smooth back to the plywood. I'll route the
scarfed and hand sanded longerons are now perfect and ready to accept
the laminated sections.
ripped the new longeron sections, all that was left to do was machine
them to the required 5/16".
gluing, I clamped in the new sections just to make sure they didn't
crack again. Satisfied they were OK, I added epoxy and many
clamps to be sure they held perfect form and contact with the plywood.
I have only epoxied in one lamination on each side to avoid
stressing the plywood. The second lamination will be added
laminations later and the clamps removed, all I have to do is trim the
over hanging ends with the router.
set the router at a depth of 5/8" and set the adjustable guide along
the outside of the fuselage. With the router bit sitting on
inside and at a width that only just contacts the existing longeron, I
was able to slide it along removing the excess lamination.
has been outstanding with no deviation in the curvature from firewall
top engine mount consists of 2 pieces of 3 1/2" x 5/8" timber which
epoxied back to back, however they differ in that the aft mount extends
only to the edge of the longeron.
forward engine mount extends all the way to the edge of the fuselage.
These mounts took me hours to get right as I had to take into
account the angles of fuselage, the top longeron and doubler (not
epoxied in yet) and the checked out portions of the mounts.
I cut out the cracked longeron sections, I let the fuselage decided for
itself the best curvature in that area. The new curve spread
over a longer area while still maintaining the 40" cabin width.
This has meant I have been able to use the planned 5/8" x
doubler instead of building one from 2 laminations as I thought I'd
have to do at the time the longerons had cracked. Here they
have left the longerons and doublers at the angle they have been
epoxied together for maximum strength in the engine mount
As I chose to not plane them horizontal, the plywood
horizontal support had to be notched so it would sit flat.
two firewall/fuselage ply braces are now in place as is the lower 1/4"
ply shelf. The trick to getting it into position
was to flex
it downwards in the middle while sliding the edge up the verticals
until it popped into place.
top cross members are now cut with all their tricky angles and clamped
until the epoxy dries. According to the builders manual, the
member for the seat back should be 6-8" aft of the rear spar at the top
longeron position. I have set it at 6" aft to assist
keeping the C of G forward. I am 5' 11" and should have no
problems with the more upright seating position.
forgot to read the electric planner safety instructions that state it's
not wise to catch the plane falling off the workbench while it is
winding down. Pretty lucky really as it could have been a lot
I have planed the top longerons and doublers flat aft of the engine
mount area, they are a little thinner on the inside. Where
top cross members meet the sides, they now slightly under hang which
means I have to cut the gusset blocks and then remove a check so they
also support the under hanging portion.
filler block needed too be leveled but the electric plane would just
gouge it as the area is too small to support the length of the base.
To get the job done I used a wood rasp to remove the bulk,
metal file to remove the rasp marks and then sandpaper to get the nice
that need dried epoxy removed to expose the underlaying timber
I can epoxy plywood or timber to that area, get scraped with my
penknife then filed with the metal file and then sandpapered smooth.
This has all taken quite a long time but I need to know my
are going to be as strong as possible.
main spar plywood webbing has been cut and just placed into position.
I am still deciding on my sound proofing options before
them in and leaving a triangular void behind.
managed to use f-clamps for the firewall gusset blocks and stopped them
from sliding down by using supporting clamps.
the epoxy is wet and I apply pressure to the tip of the "v brace" with
the black spring clamp, the timbers want to spread out. This
turn bends the cross member. So I have chocked the cross
which keeps it straight and thus stops the "v brace" spreading apart.
To stop the new timbers from sliding down, I have used the
clamps to hold them level with the already epoxied cross members.
it or not, I have spent a total of 19 hours sanding joints, cutting "v
braces, cutting and epoxying the internal gusset blocks and placing
urethane behind the main spar plywood webbing. The fuselage
its side so I can add weight to the webbing while it sets. I
weighed the fuselage today and it came in at 22 kg or 48 lbs including
2 temporary timber braces. But it is without tail
spars and some plywood down near the tail.
I am using the NACA 63005 airfoil for my vertical stabilizer, the tail
post needs to be cut to accommodate it. The whiteboard shows
stock KR2, KR2S and NACA tail post dimensions. All three have
similarities in that they start tapering from 12" from the bottom to
their tops and the lower ply ribs are all 5" above the top longeron.
The plans state that the KR tail post is 40" long
KR2S 43". I couldn't find the length for the NACA tail post
saw that the top ply rib was 34" above the top longeron which makes the
tail post 45" long. The lower ply rib sits 5" above
longeron where the tail post has to have tapered to 1.52" wide.
The top ply rib width on the tail post is .85" (27/32") wide.
From these figures, I have calculated that the bottom 12"
be 1 5/8" wide. Download the NACA plans from Mark Langford's
site and it should make sense.
the calculated dimensions, I have accurately drawn the tailpost onto
the timber leaving some extra length at both ends. A longer
of timber is used as a straight edge which I am about to line up along
the taper line. Once in position, I use wood screws
through the straight edge and into the tailpost extra length
||I then turn
over the timbers making the tailpost the top piece. The table
saw blade is adjusted to 2.4o as per the
plans and gradually reduced to 0o
by the time it has ripped to the end as per the plans for the top ply
rib. I used the same procedure for the other side of the
tailpost. A light sanding finishes it off.
a photo of the finished tailpost with the 1/4" plywood in place.
Ever wonder what NACA 63005 meant? NACA stands for
Advisory Committee for Aeronautics which was founded in 1915 and was
absorbed into NASA in 1958. Now for the 63005. The
multiplied by .15, gives the section lift coefficient = 0.9.
The "30" when divided by 2 gives the distance of maximum
from the leading edge (as per cent of the chord) = 15%. The
gives the maximum thickness of the airfoil (as per cent of the chord) =
5%. So now you know.
tailpost has to be angled aft 7o
have cut that angle through a piece of pine and will use it as an
aligning tool. By holding the tailpost against it I am able
see exactly where to make the angled cuts on the top and bottom
||Have a look
at what I have done with the bench
. I have leveled both the fuselage on the "loft" and the
level on the workbench. Shooting a vertical line down the
fuselage, I have made sure that it touches the cross members at the
centers which were marked earlier for aligning the boat. As
laser exits the rear of the fuselage, it tells me exactly where to
position the tailpost for vertical.
stop the tailpost from sliding while the epoxy dries, I have
pre-drilled 4 small holes and gently driven thin nails through the rear
of the tailpost and into the ends of the longerons. These
get removed afterwards.
KR2S is starting to look more like an aircraft now with the horizontal
stabilizer resting in place and the front main spar in position.
main spar is not completed yet, I decided to cut the holes in the
fuselage and slide it into position anyway.
laying the plywood floor in the cockpit, I have cut and epoxied the
three blocks that will support the rudder pedals. What I have
also done is add square blocks to the open areas where the plywood will
span bottom cross members. This will reduce sagging pressure
standing on the floor and possibly any drumming. Urethane
offcuts have been added as sound proofing.
taped together two pieces of light cardboard and then layed it on the
cockpit floor to create a template for the plywood. After
around the the timbers it was just a matter of tracing the outline on
the plywood. My first officer is always keen to help
imagine what it will feel like in the sky.
long clamps can be changed around to expand which came in handy when
applying pressure to the main spar supports whilst the epoxy set.
the rear brace that holds the horizontal stabilizer to the fuselage is
being aligned with a straight piece of timber. It has to be
aligned with the bottom longeron as it kind of sits out in the
breeze until the outer plywood skin is fitted. The plywood in
this photo is only there to keep the two verticals aligned with each
other until they dry. At that time, 1/4" plywood webbing will
fixed to the forward side and up to make contact with the rear HS spar.
the hanging verticals line up perfectly with each other and the bottom
elevator needs to have freedom of movement 20o down and 30o up.
Upward movement poses no problem however to allow for the
downward movement, an area has to be removed from the top longerons so
as the elevator spar doesn't touch them. I initially cut away
curved area with a jigsaw and then finished it off by wrapping
sandpaper around a tube. This time it was my prospecting
Then I went to work sanding.
time has come to epoxy the horizontal stabilizer to the fuselage
permanently. The fuselage is taken out of the garage and
on the concrete driveway. Timber wedges are used
to bring everything up to level. The side to side measurement
easy to take as anywhere you place the level across the fuselage it
should read the same.
and aft is another story as the fuselage has a "banana" shape.
The level reference point for fore and aft is taken between
front and rear spars on the top longeron. My digital level
this area perfectly. All future wing and stabilizer angle of
incidences will be adjusted with reference to this point.
finalizing the job with epoxy, I do a complete dry
run of the
finished settings. This means getting equal amounts of HS
out either side of the fuselage, shooting the diagonals from the tips
to the very center of the firewall, making sure both tips are
vertically identical. Finally I set the - 0.75o angle
of incidence using the the templates which as stuck on the outside of
the HS/elevator tips. When I see that it is possible to get
these right I know I can epoxy with confidence.
enough room to lift the HS from the webbing and move it back so I can
apply epoxy to all the webbing and spar surfaces.
applied, I move the HS back between the webbing and apply a few clamps
but only lightly as I need to go through the whole procedure of
measuring, leveling and incidence setting all over again. I
a lot of time tweaking here and there to get everything perfect before
adding the rest of the clamps and enough pressure to hold it in place
until the epoxy cures.
the passage of time I have found that the cockpit floor is becoming
dirty and a little stained so I have decided to sand is clean.
||To make it
easier to clean in the future I apply a coat of clear satin flooring
I was happy with the results of the cockpit floor I decided to varnish
the whole fusleage. I sanded with 80 grit sandpaper then 120
grit. I then vacuumed the fuselage out and applied the first
of varnish. I let it dry over night and then did a light sand
using 240 grit non clog paper the following morning. Like
I vacuumed but I then I wiped down all the surfaces with a damp cloth
to remove every last trace of dust. A final coat was applied
allowed to fully dry. After a total of 17 hours of work, the
result is outstanding.