3435 OCEAN PARK BOULEVARD, SUITE 206
SANTA MONICA, CALIFORNIA 90405-3311
TELEPHONE: (310) 390-8000
FACSIMILE: (310) 397-0028
Volume I Issue II October 1996
The KROnline Newsletter is intended
to serve as a conduit for information and building ideas about
the KR family of experimental aircraft. It is meant to share
the knowledge that has been hard won by those who have gone before
us. Education is the cornerstone to a quality built KR. The
article submissions each month are from KR builders and suppliers.
Opinions express are solely those of the individual authors and
not of KROnline. Any ideas or techniques discussed are to be
duplicated and used at the sole risk of the experimental aircraft
builder. KROnline does not endorse or warrant any certain outcomes.
Rand Robinson Engineering is in no way affiliated with KROnline
and as such, does not formally endorse any information published
COPPER STATE FLY IN 1996
KEN THOMAS'S KR2S
GLASS CYLINDER BAFFLES
BUILDING INSTRUMENT PANELS
Two beautifully finished flying KR2's were on display
and presented good examples of what a KR can look like. What
I mean is the airplanes have quality and detail as good as any
Lancair, Glasair or RV at the fly-in. Empty weight of each airplane
is around 650 pounds and gross over 1000. (IMHO, this demonstrates
the price you pay for a plush interior, lights, electrical system
and super shiny paint job.)
This KR2 from Utah has factory retracts and mechanical brakes. The canopy is a standard KR2 bubble. The airplane has a lot of attention to drag reduction. Even the tail wheel has a fairing, or wheel pant. One notable detail is that the cables for the tailwheel exit the fuselage below the exit for the rudder cables. They join to the rudder cables within the fuselage. This looks as if it will provide a straighter run to the tailwheel, and less aerodynamic drag. The control surfaces have very straight trailing edges and are quite smooth. (I have seen some that are pretty wavy.) The engine is a Revmaster 2100. Interior featured dual control sticks. Flaps are fitted, but I didn't notice whether it has wing tanks.
The other plane is based here in Phoenix at DVT.
It is a very smooth airplane, with a widened fuselage and Dragonfly
canopy. The interior is done up in burgundy velour. The instrument
panel, trim, and engine case are all the same shade of burgundy
paint. (I guess that answers the question of what color to paint
the engine?) It has a pearlescent topcoat on the paint! The
intake manifold and spinner appeared to be gold plated! The
airplane has what looks like Diehl fixed gear, with Matco hydraulic
brakes. No flaps or wing tanks are fitted. I have seen this
airplane fly, and it is fast! I overheard the owner telling
a spectator he didn't like the RR pre-molded parts. Since he
widened his fuselage, the RR parts would no longer fit. He sold
off the ones he had, and used glass over foam for his turtledeck.
He indicated the foam provided a more solid base for the glass.
To demonstrate, he gave his turtledeck a thump, and it did not
flex. He then pushed on his cowl, and revealed how much flex
there is in the glass by itself. This was A Very interesting
(and convincing) demonstration.
There was also a project in progress displayed.
This plane was on what appeared to be Diehl tri-gear, with fixed
windshield and a gull wing door. It was a little rough, but it
was nowhere near done, either.
The questions being asked at RR was "Do the wings come off?", " How much?", "What size engine." "How fast is it." In my short conversation with Jeanette Rand, she mentioned that the fuselage width on the KR2S was not changed from the KR2, so builders can use the KR2S canopy. You would have to fabricate your own canopy frame.
In addition to the premolded wing skins, RR also had a dual stick assembly on display. It is welded up steel and the workmanship appears to be first class. It bolts to the main spar in the same manner and position as the single stick assembly. The elevator control cables come to a horn on the assembly. It looks to have the same distance between connection points as the single stick, so control forces and sensitivity should be the same. It has a smooth, tight feel to it. I got some really funny looks because I was standing there, holding this control stick, making airplane noises ;} (Of course, my nine year old was nowhere to be found, so I couldn't blame him.)
Vendors of interest included Aircraft Spruce, Varga
Enterprises (airplane hardware and instruments), Pacific-Coast
Avionics, Avery Enterprises (tools, arr. Arr, arr!) and Renavair
(surplus hardware and stuff). I mention these vendors because
they all provide free catalogs, except for Aircraft Spruce.
Aircraft Spruce sets up a good sized and fairly well stocked display,
and if you buy something, will throw in a new catalog.
I always enjoy the ultralight area. It is amazing
what these people can do with aluminum tubing and pop rivets!
I study the control systems, in particular, and I have some ideas
that I might try in my KR2. (Yes Randy, I will submit another
article to KROnline!)
The only downer to Copperstate is the lack of low
dollar airplanes, like KR's, Volksplanes, Pietenpols, and such.
There has always been a large turnout of big buck glass slippers,
and RV's. We need to get our airplanes done and have a herd
of KR's show up! Now THAT would be really exciting! I'm
going out to work on my plane now, so I can do my part in making
that wish come true! How about the rest of you!?
Ken Thomas, of Jasper Alabama, recently completed
one of the first KR2S's in the US. Because he is well over 6
feet tall and 250 lbs, Ken moved his firewall two inches forward
for more leg room by adding one inch each to both bays forward
of the main spar. His fuselage was also stretched 6" wider.
The horizontal stabilizer was lengthened two inches on each end,
and counterbalanced. Empty weight is 750 lbs. Construction time
was 15 months averaging 3 hours per day. He has 11 hours on it
The Subaru EA82 weighs 235 lbs firewall forward,
not counting the PSRU or propeller. It is a normally aspirated
dual port unit running the stock electronic ignition. Carburetor
was a Holley 5200, but is currently being changed to dual 54mm
Bing carburetors found on many Rotax's and Sea-Dos. Ken built
the engine mount somewhat to plans, but used one size larger diameter
tubing, as well as one size thicker wall. The mounting points
are also altered to connect to the firewall at a location very
close to each of the longerons.
The PSRU was constructed by Dave Johnson at Reductions in Manitoba, Canada, (204) 853-7998. This $1500 reduction unit utilizes a 3.5" belt and a ratio of 1.86:1. The 3 blade Warp Drive prop is 60" in diameter, and features ground adjustable pitch carbon fiber blades. Ken says it's extremely smooth and quiet.
The canopy is a Dragonfly which has been sectioned
similar to Bobby Muse's and Troy Petteway's planes. The center
section is offset a few inches from the centerline to allow for
more room for entry and exit. The canopy sits on a "false
wall" about three inches tall to allow for lots of head room.
The gasket was made by covering the door with Saran Wrap, applying
lots of clear silicone to the frame, and closing the door. The
mechanism which latches the canopy in the open position is a simple
friction lock that Ken designed from a piece of left over 1"
aluminum channel and a piece of steel rod.
The instrument panel is fiberglass, and was made by laying up several layers of glass onto a piece of blue styrofoam. It looks like aluminum, but is much easier to cut and drill. The radio stack protrudes slightly to allow more room for the fuel tank. The dual stick controls are Ken's design. The right stick is easily removable in case the passenger doesn't feel comfortable with it. The seat is a nylon sling with upholstered cushions. There is plenty of leg room in this airplane.
Diehl fixed gear mounts Cleveland brakes and wheels. A 6" x 36" .060" aluminum belly board speed brake is hinged from the aft spar and will deflect up to 40 degrees. This not only slows the plane down quickly for landing, but also pitches the nose down significantly for a better view of the runway.
Tailwheel is a Matco unit purchased from Wicks Aircraft.
Ken's installation uses the stock KR shopping cart wheel, however.
Ken made his cowling by gluing foam planks together,
sanding, glassing, then removing most of the foam and glassing
the inside. A scoop on the bottom feeds air to the 6" x
2" x 24" radiator. Oil is checked through a home-brewed
spring loaded door similar to those found on Wichita planes.
Having already built an Avid Flyer, Ken chose the
KR2S because he wanted to do more cross-country flying, at a higher
speed than the Avid Flyer was capable of. He also felt that the
KR2S offered more opportunities for stretching the cockpit to
better fit his build.
Cruise speed is only 125mph presently, due to carburetor
problems, but will improve as soon as the RPMs come up. Ken reports
that his KR2S is much less pitch sensitive than standard KR2s
that he has flown, and feels that the S model solves the problem.
Also, the heavier engine located further forward results in a
CG envelope 2 inches forward of the stock location, which Ken
feels contributes to its stability. Hands off flying is not a
problem. So far, Ken has been using 85mph on final, deploys the
belly brake which slows him to a 75mph glide, and a 65 mph touchdown.
More experience with the plane will probably yield slower landing
speeds. Stall speed is around 55mph.
Revmaster is alive and well in Hesperia California!! The reason I started off with that comment is every time I bring up Revmaster I get "are they still around??" Well the answer is yes!
Revmaster was founded in 1959 in order to produce high performance VW engines and components. In 1968 the first R2100 aviation version of the VW engine was produced. This model was well in advance of its time 28 years ago and is still being produced today. Over the years a comprehensive product support program has been available for the thousands of engines that are in service throughout the world, such as the complete overhauls, spare parts and instructional services for the persons that wish to build their own engine. All of the R2100 parts and accessories are available today.
The standard VW crankshaft used in the 1600cc four cylinder opposed, air cooled engine is made of 1050 carbon steel forging. The bearing journals are induction hardened and the crankshaft is not counterweighted. It is a three main bearing unit with a small fourth main bearing dedicated to absorbing the belt tension loads from the cooling fan and alternator. The crankshaft has a 69mm stroke with 55mm nominal bearing journals. Revmaster, as well as other firms have used these crankshafts in smaller engines, however, they have their limits.
1. It is difficult to attach a crankshaft flange to the existing crankshaft design that would safely position the propeller disc forward of the cylinder heads to any great degree. This becomes more complicated when the propeller is oil controlled or manually controlled because of the increased weight and lack of galleries. The main reason for this dilemma is the absence of a fourth bearing to support all the propeller loads.
2. The stroke of the crankshaft limits the horsepower output, also the lack of counterweights causes greater crank deflection. The thrust absorption bearing is at the wrong end of the crankshaft for aircraft use.
3. Since we do not have control over the manufacturing process we can not guarantee the quality of the crankshaft, also there are after-market crankshafts that are not forged and could be mistaken for an original.
4. The automotive crankshaft does not have sufficient
design and material strength for use in higher horsepower output
Revmaster 4340 Forged Crankshaft
Revmaster designed their own crankshaft assembly with the following features incorporated:
78mm stroke with 55mm nitrited bearing journals and counterweights
A large number 4 main bearing dedicated to accepting the dynamic loads of the propeller which has been moved well forward of the cylinder head group. The crankshaft flange is the number 4 main bearing when it is assembled to the crankshaft with a long 3 degree locking taper. This design does not require a woodruff key common in the automotive version to transmit engine torque to the propeller.
The propeller flange has a number 1 - 127A which is common on Continental and Lycoming engines
The large number 4 main bearing allows for oil control capability for the propeller. The propeller thrust is taken up at the number 3 main bearing which is next to the number 4 main at the propeller end of the engine. The bearing will accept tractor or pusher configurations.
Revmaster continues to
lead the way by being one of the only firms to offer turbocharging
as an option on their VW based powerplants. The advantages of
turbocharging has long been known in the aviation industry. Revmaster's
R2100-D Turbo produces 80 hp at 3200 rpm for 5 minutes and a maximum
continuous output of 70 hp at 3200 rpm and 32 inches HG.
Revmaster's standard engine,
the R 2100-D 65 is rated at 65 hp at 3200 rpm continuous (full
throttle). The standard features of this engine include E4340
forged crankshaft, dual ignition, Rev-Flow carburetor with mixture
control, alternator, geared starter and lightweight flywheel,
oil cooler, oil filter system, oil sump side drain system, alternate
air source/air filter assembly. All this for .......$5185.00
(price current May 1,1996)
Revmaster R2100-D 65
For an additional $975.00 you can upgrade to the 75 hp heads. This will give you 75hp for takeoff (five minutes).
Another thing I always hear when the name Revmaster come up is "didn't they use cast cranks?" . I haven't been able to confirm this as fact or rumor but what I have been told is that ALL Revmaster engines now use the E4340 forged counterweighted crankshaft with 78mm stroke. Other things that I like about the Revmaster is the fact that they move the thrust bearing to the front of the engine where it belongs and they incorporate a huge propeller hub bearing for supporting heavier constant speed propellers. They also offer options such as engine driven fuel and vacuum pumps. You also get a real spin on oil filter system with the Revmaster engines.
All in all the Revmaster line of powerplants look
to be a good option for the KR, they are economical, reliable
and the company has been around for 28 years!! They also have
builder support now for those of you wishing to build your own.
In these days of $15,000 rebuilt Lycomings and Continentals,
$5185 for a new (not rebuilt) powerplant sounds real good to this
Oil filter, oil pump & fuel pump assemble
If any of this sounds interesting to you and you
would like more information, I suggest you write or call Revmaster
Aviation, 7146 Santa Fe Ave. East, PO Box 402077 Hesperia, CA.
92345 Phone (619) 244-3074 FAX
I am the wife of a homebuilder. My husband started
our plane in February of this year while I was out of town on
business for the week. He Emailed pictures to me of his progress
while I was away. I was confused. He did say plane didn't he,
because this thing looked like a boat? Even when I returned and
he started putting the plywood skins onto the wooden frame, I
was still thinking , "Nice canoe Honey." But now, 7
months later our plane looks like a plane with a tail and a turtle
deck. The reality of owning a plane hit when we went to Chino
Airport this summer for an EAA fly-in. We got to see not only
a couple of KRs but a few of the other homebuilt kit planes completed.
My priority, after seeing these planes, was to have a well built,
comfortable, aesthetically pleasing plane. I got some great ideas
from the planes we saw. I saw some great paint jobs and some
really nice interiors. My husband can have full control of the
craftsmanship of the plane but I decided that if this is going
to be my plane too, that I want to help decorate (just like a
house). The other thing that I look forward to is traveling on
the weekends when the plane is done.
As for my feelings about flying in a homemade plane,
let me start by saying I am not afraid to fly. My father is an
airline pilot and my husband is a former Alaskan Bush Pilot.
I flew a lot with my husband in Alaska. It really toughened me
up to fly in low visibility weather and over tall mountains in
a small plane. Turbulence was also common. The reward of the
view has always made it all worthwhile for me.
I recently got my first offer to ride along in a
homebuilt plane. The invitation came from a friend of ours who
has a Dragonfly. Even with my experience in small planes, I
was a little bit nervous. I know how skilled my husband is at
flying and I know his attention to detail in the construction
of our plane. Even though I know our friend and I like him, I
had no reason to feel confident about his flying skills or his
craftsmanship. Stepping into the plane, I was unsure of how careful
I should be placing my weight on any particular part of the plane.
Once in the plane, my next concern was whether or not I was going
to be too tall for the canopy to close. But I fit in. The seats
were comfortable and I had plenty of leg room. It was warm on
the runway without air-conditioning and I asked why the canopy
wasn't tinted out more. My pilot explained that more tint would
inhibit his visibility at dusk. (OK. But next time I wearing
a bathing suit so I can get a tan.) We took off with no problems,
climbed, visually watched for other traffic while listening to
the comm radio. It was a hazy day. The morning was cool but
by the time we went flying around 2 p.m. it was very warm. Because
of this, I did not expect a smooth ride. Sure enough I got what
I thought I would get, a bumpy ride on and off. We flew for about
20 minutes out and 20 minutes back. I felt very safe even with
the turbulence. I did worry about hitting my head on the canopy
with the sudden bumps. By tightening my straps I avoided premature
ejection from the plane. To avoid air sickness, I kept an air
vent pointed on me. This usually works pretty well. My pilot
proved to be very competent and we made it back safely. The VW
engine held up great and so did our big Dragonfly wings. I think
I will plan my next trip around the thermals and the winds. I
would gladly go again though. I have confidence in our friend
and his plane now, so I can just check out the scenery and enjoy
the ride from now on. ---Michelle Mims
(Editor's note: Eat your hearts out guys. How many
women have such an open mind to our crazy dreams? Thanks Michelle
for taking the time to share your experiences.)
Q2 - Revmaster 2100DQ - 75hp
I have recently installed glass baffles on my Q2
and found the results very satisfactory (if not TOO satisfactory).
While my engine was running within the limits I felt that the
temps I was seeing were too high. The glass baffles have been
used be several Q2 builders and by all reports have worked very
well for all who have tried them.
With per plans baffling on a 60-70F degree day I
would indicate the following:
CHT OIL SPEED RPM
CLIMB 390-410 180-190 100mph 3000
CRUISE (cowl flap open, mixture rich) 340-350 180-190 0-140mph 3000
CRUISE (cowl flap closed, mixture leaned) 360-370
180-190 145mph 3100
After making and installing the glass baffles I indicate the following (yes, they are in degrees F and have been double
CHT OIL SPEED RPM
CLIMB 200-225 190 100mph 3000
CRUISE (cowl flap open, mixture rich) 175-200 190 140mph 3000
CRUISE (cowl flap closed, mixture leaned) 175-200
190-200 145mph 3100
Glass baffle installation:
Remove everything from the top of your engine and
seal the intake and spark plug holes.
Wrap top of cylinders and heads with duct tape, shrink
wrap plastic, or whatever. You are just trying to keep the expanding
foam out of the cooling fins.
Squirt expanding foam (I used the stuff from the
hardware store in the can) on top of the heads and cylinders (after
they are covered with tape or something!). There are two directions
you may go here. Either make two individual plenums with each
covering only one side of the engine (like I did) or make one
plenum that covers both banks of cylinders and the top of the
After the foam dries carve/sand/cut a functional
shape out of the foam. The goal is to have a plenum box over
the cylinders. I sanded/cut/carved and then would trial fit the
intake runner and cowl until nothing touched leaving enough room
for the fiberglass. The foam needs to be such that when you layup
glass on it the end result will be a glass box that fits snugly
against the sides of the cylinders and around the heads but doesn't
touch the intake or cowl. Once the foam is the way you want it
put duct tape all over the foam to act as a mold release. The
goal isn't perfectly smooth glass work so you don't have to be
real particular here about the smoothness of the mold.
Layup about 3-5 ply of 10oz BID over the whole works.
When cured pop the box off the foam, trim, and shape. You can
effectively shape the box by heating it with a hot air gun and
then bending with pliers. With a little work you can achieve
a very snug fit over the cylinders and heads.
Drill holes in the box over the spark plugs to allow
your spark plug socket to fit in. Cut four round pieces of baffling
material to fit over the plug and up against the plenum box to
seal around the plugs.
The inlet tends to be a little more work. There
probably isn't a single best way to do this. I decided to use
one 3" diameter tube for each plenum box. This tube goes
straight from the forward face of the plenum thru the cowl and
into the air. It is glassed into the cowl and I used baffling
material riveted to the aft end to form a seal up against the
plenum. I think Ron Whetson used the per plans intake and made
a glass runner from it to the plenum. Phil Haxton made a single
plenum and feeds air from the top center of the cowl into his
plenum. My installation has two intakes, the 3" diameter
tubes, each with 7 square inches of area, total 14 square inches.
This has proven to be to much. My bottom of my intakes enter
the cowl about one inch above the split line. The front of the
intakes are cut perpendicular to the airstream. I have experimented
with trimming the intakes even with the cowl. This doesn't work.
It appeared that I was getting zero cooling air. I am now experimenting
with reduced intake diameter sizes.
1) I trimmed my plenum to stop at about half way
down the cylinder barrel then wrapped a piece of tin over the
outside of each cylinder barrel and safety wired them together.
This forces the air to flow through the fins to the bottom of
the cylinders but still allows easy removal of the plenum box.
I suggest using Great Plains cool tin for the bottom of the cylinders.
2) Ron Whetson suggested placing the CHT probes on
the bottom of the cylinders to pick up the temp on the warmest
part of the cylinders.
3) This setup forces you to do something different
with the oil cooler. I made a small tin baffle to the lower cowl
and cut a 1"x 10" slit horizontally to allow air into
the cooler. I am considering doing away with the stock exhaust
so that I have more room up front and can make a nice glass plenum
type box for the oil cooler.
4) The whole process took me a couple of long days.
It really isn't that much work for the much cooler temps you
end up with.
(Editor's note: Nigel has been kind enough to allow
the following information to be included in KROnline. While the
topic information is more auto engine specific, the processes
are most interesting and applicable to other areas of aircraft
The stock manifold on the EA-81 has many drawbacks.
It is restrictive to flow, and is heated by the coolant which
reduces available normally aspirated power. It is heavy at 7
lbs, bulky, and has an awkward physical carburetor interface.
A much improved manifold can be easily constructed from carbon
fiber by the average builder. This article will attempt to describe
how this may be accomplished. Carbon is used for its high modulus
and low weight to give an acoustically solid structure. You will
first make the head interface flanges from steel, and then design
and construct the manifold itself. Although not complicated,
construction is a multi-step process completed as a series of
small evening tasks.
CYLINDER HEAD INTERFACE
The first parts to make are the cylinder head manifold
and cooling interface adapter flanges. No these are not carbon
and they are the toughest parts, but still easy for a homebuilder.
There are a number of design options available. The simplest method
requires basic tools but some brazing or welding is required which
unfortunately is unavoidable.
The adapter plates will provide 1.5 in diameter stub
tubes to couple with the carbon manifold. As the head ports are
slightly smaller than this, the ports will require some slight
enlargement. Using a 1 inch sanding drum on a drill gently open
the head ports by grinding away aluminum on the inside face keeping
the hole round. Try not to remove too much on the coolant passage
side to leave as much clearance as possible for the coolant tubes
to be added later. Check constantly with a piece of 1.5 inch
stainless exhaust pipe until the ports are the correct size and
match the pipe. Transition any ridges inside to make a smooth
opening. There is a cast ridge running vertically into the port
that will interfere with this process so grind it away at the
opening area only and transition into the port. I'm not sure
exactly what it does but all the experts say leave it in.
Now using a cut up file jacket, make a template of
the bell shaped interface at the head port to include the 3 mounting
bolt holes and surrounding flat gasket face area. Using the
template fabricate two plates from .125 minimum stainless or 4130
steel. Drill the three mounting holes to 1/4 inch to later take
1/4 X 28 cap screws. Cut out the induction hole using a series
of closely spaced drill holes and then a 1/4 round file unless
you have access to a lathe, then turn them. Fit snugly to 1.5
by .035 inch stainless exhaust pipe. Mark and cut out the curved
coolant slot using a drill and file. Fabricate two 1 inch long
induction stub tubes from the 1.5 in pipe and temporarily fit
them into the induction holes in the flange. Next make coolant
outflow tubes from 3/4 in 4130 or stainless about 4 inches long
but whatever will best fit your installation. Cut these tubes
at about a 30 degree angle up from the horizontal to fit over
the coolant holes in the flange. Now trial fit everything on the
head ensuring all holes and ports properly align and the coolant
tubes clear the bolt holes. When satisfied mark the locations
and then braze or weld the pieces together. If you don't have
OA welding equipment try a friend, or farm it out. You may try
silver solder with a spitfire propane torch and Mapp gas but this
has not been proved so be careful. The welding will probably
warp the plate slightly so using an inverted belt sander, hold
the plate nice and square against the belt and grind it flat.
Rotate it occasionally to avoid uneven grinding. To prevent hose
blow off, make a raised end on the coolant tubes by wrapping 2
turns of solid copper wire about 22 gauge near the end and solder.
Now etch and paint with your favorite epoxy paint or enamel.
The heads are metric so get some old bolts of the right thread
and cut off ½ inch lengths of thread and screw these into
the six mounting holes until flush or just slightly recessed with
the head gasket face. First cut small slots in one end so you
can turn then in with a screwdriver. Install these with JB Weld
high temp epoxy available at any auto parts store. After cure
drill and tap to 1/4 X 28. Purchase some 1/4 X 28 X 3/4 Allen
head cap screws for mounting. Fabricate two gaskets from good
quality gasket material to match your new adapter plates and bolt
them on using Permatex gasket compound. The black rubber impregnated
compressed paper stuff works best. Do not use cork or any other
very soft material as it will squish out and leak when you torque
the plates down. OK that was the worst part now on to the composite
You will make the inner core and fit it to the engine, then complete the various layups of carbon, then dissolve out the core, then fit attach tabs and the carb mountings, and finally finish the outside of your manifold. You first need to have the heads on with head gaskets and at least two bolts per side snugged up. This will a ensure proper fit of the manifold.
The core is made from fine grained builders insulation
Styrofoam SM in three pieces, the plenum and two runners. Do
not use the expanded bead popcorn foam as it is too rough. The
design and shape of the plenum depends on your particular application
and carburetor installation but basically it is a cavity which
feeds the two runners. It serves as a capacitor or storage tank
if you like, to help even the flow through the carb caused by
the vacuum pulses. Mine is a down draft 2 barrel mounted on
top of a 7 X 4.5 X 2 in plenum. For low profile applications
a side draft carb could be used so design your plenum accordingly.
Try hard to keep it symmetrical and watch out for the steering
effect of the throttle plate(s) which tend to direct raw fuel
to one side at part throttle. This will cause uneven mixture
and all the associated headaches of roughness, burnt valves ad
nauseam. My throttle plates open fore and aft so it remains symmetrical.
Throttle plate symmetry is very important.
Cut your plenum core with a band saw or hack saw.
Sit it on top of your engine in exactly the position you want
it. Shim it up underneath to give at least 3/8 inch clearance
from the block to allow for its eventual thickness and some running
clearance. Now plan your runner shapes to provide a gentle curve
from the plenum though a 90 degree down turn to mate with the
top of the stub tubes on your head adapters. Make them by cutting
foam out in two dimensions with a slightly tapered square cross
section. In other words they are bigger at the plenum than at
the heads. This keeps the velocity lower in the middle but provides
more mass to help push the new charge in. Now trial fit the runners
to the plenum and adjust as needed until you are happy. Use a
sanding block to trim fit everything. Glue the runners to the
plenum with a dob of 5 min epoxy or hot glue in the center of
the joint not the edges because its hard to sand. Then re fit
everything and push the runners gently onto the stub tubes to
leave a slight impression sanding mark. Now start to shape the
core by sanding the corners to a nice radius and working your
way down the runners. Leave them basically square at the plenum
and transition to perfectly round at the ends where they meet
the stubs. They should be the same the inner diameter of the
stubs seen by the impression marks that you made earlier. Foam
seems to sand easier in one direction only. Use light pressure,
take your time and trial fit regularly to check progress. The
core will be a little rough due to the grain of the foam, this
is OK. Any chunks that get torn out need to be filled with wax
or something that wont stick to epoxy. It will not take long
however to get a perfect Styrofoam core matched exactly to your
The manifold is made of three plies of 282 2.7 oz bi-directional carbon reinforced with extra plies at the plenum. The preferred laminating resin is PTMW Aeropoxy or Epolite 2184 and 2410 hardener these have good high temperature properties and excellent peel strength. Any good laminating resin will probably do however but I would avoid 2427 as it has some nasty tendencies not to bond to itself even when properly sanded. I cant understand why people build high stress aeroplane joints with this stuff, its bad news and there are many better products available. To avoid a mess and bumpy overlaps the layups pretty much have to be done in stages with a cure in between. Start with the plenum top or bottom and lay on 2 plies of carbon with the weave at 45 degrees to the long axis. Lap about 1 inch onto the base of the runners and fully up the sides of the plenum flush with the other side. Use gloves and conform it with your hands. Carbon is very stiff initially and takes about 1 to 2 minutes for the resin to soften it, then it conforms just fine. Now do the runners with 1 ply and overlap onto the plenum by ½ to 1 inch. Wrap the small ends around the core best you can and allow an overhang which will be trimmed later. While your all sticky layup some mount tab construction material on saran or plastic sheet about 4 inches square 2 or 3 plies of carbon or glass. After cure transition the edges with a hard block and 40 grit sanding belt cut up or paper ensuring you don't damage the exposed core. Then do the same layup above to the other side overlapping the first layup on the sides of the plenum and runners. Use wet resin rich layups, shiny bit not dripping pin holes will leak air. When cured it will be much easier to handle so transition sand all the edges and do it all over again trying to move your overlaps slightly to avoid a big bump. When you are finished you should have 3 plies on the runners overlapped on their sides to 6 plies and 6 plies on the top, bottom and sides of the plenum. If you are mounting your carb to the plenum add a 3 or 4 ply pad over the mount point for added strength and to allow for sanding flat. When cured have a last look and if you are satisfied then place in your oven pre heated to 150 deg F and let soak for 30 min then gently raise the oven to 180 F and soak for another 30 minutes. This will raise the creep temp of the epoxy to about 250F.
Now trim the head ends of the runners flush with
the foam core. Locate and cut out your carb inlet hole(s) with
a dremel and dental burr or hole saw. Take a chisel and dig out
much foam as you can reach from all openings. Dissolve out the
rest with MEK or lacquer thinner. Gasoline is not recommended
it turns the foam into a thick goo which won't completely dissolve
and makes a real mess. Pour it full of boiling water with a little
dish soap to remove any wax if you used it. Now slosh the inside
with epoxy thinned out with a little MEK or alcohol, let drain
and cure. This should make the inside nice and smooth. Repeat
if necessary but a slightly rough plenum area helps vaporize and
mix the fuel. The runner ends at the heads need to be very smooth
this is the point of highest velocity, so sand the inside curves
best you can with small strips of paper on your finger.
Mounting tabs(s) are next. Mount your nearly finished
work of art on the engine and locate where you wish to secure
it. Mine has one tab only on the rear which ties into the inner
of two bolts on the cover plate on the former oil filler neck
which is long gone. I fill my oil through a small fitting I made
on a rocker cover breather pipe. Use the construction piece you
laid up earlier and cut it into a tab about 1.5 inch at the junction
of the plenum and tapered to about 3/4 inch at the bolt. Tack
it in place with a dob of 5 min. When set make a flox fillet
both sides at the junction and layup 2 plies carbon both sides
overlapping onto the plenum. Cure, trim and drill out the bolt
Block sand the carb mount pad until flat then drill the holes to mount your carb. Install AN-3 bolts from the inside up through the holes to make studs. Rough up the inside of the bolt heads and coat them with JB Weld to hold them in. If your carb has big mount holes mine does make some spacers from aluminum pipe or whatever to make a nice fit to the AN-3s. Add a vacuum port if you like made from small pipe Drill a corresponding hole somewhere in the plenum and secure it with JB Weld epoxy. OK almost done.
To make your new manifold a true work of art it needs
a nice finish. Final wet sand all bumps until presentable, then
paint on a thinned coat of epoxy and let cure for a few hours
until a firm tacky then bake at 180F until cured. This will fill
most of the weave and look pretty good, but for a really nice
look, wet sand it again and apply another epoxy coat as before.
I took mine one step further and sanded it with 320 then sprayed
on a clear coat of Dupont Centarus clear coat. It looks like
a mirror but this wont give you any more power.
The transition to the stubs is made with a 2 inch
length of 1.5 in ID rad hose and worm clamps, just like Lycont
do it. The carbon should just touch the top of the stubs so there
is no heat transfer and the manifold will run much colder than
ambient due to the latent heat of vaporization of the gas. The
worst case is after a 5 minute shutdown and re-start where the
manifold gets heat soaked from the engine, but it wont get soft
or collapse and once running will rapidly cool. Good luck and
I finally got around to getting enough photos digitized that I could produce an article for KRONLINE. Here Goes.
I decided to build my own "top end" that is all of the structure above the "boat" was built up from scratch. One of the problems I had early on was deciding how everything would fit together. I wanted the forward deck to be removable, but this meant much more work than just glassing the deck in place. To be sure I came up with a good attachment scheme, I decided I needed to have my instrument panel done to look at various attachment methods.
STEP 1 POSTERBOARD
I actually had fabricated everything out of cardboard prior to doing any foam and glass work, so I began by taking some sheets of white poster board from K-mart, and cutting them into a shape that would approximate the layout of both the forward and aft decks.
Then I would sit in the boat, with a cardboard mockup of the cowling and try to make the best tradeoff between panel space, and over the nose view. I used some other KR photos and looked closely at the KR-2 video I had to see what types of range in panel size I had.
Mine came out approximately in the midrange as far as height.
I cut out several instrument squares using a students compass and ruler. The Aircraft Spruce catalog has all the instrument panel dimensions, and I used these for a guide. By placing a series of vertical and horizontal guidelines on the poster board, I could mix and match instruments and get a good layout before going to the next step.
I used masking tape on the back of the instrument cutouts so I could move them around and try different placements. I also cut out some 2"x 7" and 2"x 8" radio stack cut outs as well.
To insure symmetry, you can fold the posterboard
along the horizontal centerline, and trim it with scissors if
you have to re-size it.
STEP 2 MASONITE
A local hardware store sold masonite in 2'x4' pre cut sizes, which worked out well as I had sold my truck. I was able to fit these into the back seat of the car. The posterboard was used as a template, and the rough outline was cut. Then it was easy to sit in the boat and check things out for size.
I trimmed the masonite down twice as during the cockpit
trials, I found that the louder I made the airplane noises, the
larger the panel looked. After cutting the masonite, I then went
pack to the posterboard to re-shuffle the instruments in the panel.
I don't have any photos of the forward deck build-up
process so that will be left for another article. Suffice it
to say that between steps 3 and 129 the panel size has become
fixed and it is time to cut holes to check the clearance for the
STEP 130 CUTTING MASONITE
This is a good practice step, as you find out if you have spaced everything correctly. I used a flycutter to cut holes in the masonite. Cut the holes small, then you can file them out to the appropriate size. I happened to have several junk instruments I purchased and have been given which allowed trial fits of just about everything except avionics.
If you are going to build your own fuel tank, make
sure to leave room for avionics and if you ever plan to get an
artificial horizon, the mil-surplus old stuff I have is deep.
STEP 131 CUTTING ALUMINUM
I had considered making my panel from wood, but my
father who does a lot of woodworking suggested veneers, when I
was having trouble finding hardwood in the correct dimensions
for my panel. So I decided to cut the basic panel out of Aluminum.
Although I was able to find a local supplier for
my firewall stainless steel, I decided to buy my aluminum panel
material from Wicks. I have enough to do 1 and ½ more panels,
so if anyone wants to make me a deal. Let me know.
Figure 1 Shows the posterboard, the masonite & the finished panel. Note that the oak veneer does not have all the holes cut at this time.
Flycutting the instrument holes was an experience.
Not as bad as I expected. I have a small benchtop drill press
which has paid for itself many times over during the project.
I shelled out megabucks for a Unibit drill to do the intermediate
holes for fuses etc. I wonder if I will ever get my money out
STEP 132 DRESSING UP THE PANEL
You can dress up the aluminum panel, paint it, or
do like I did, choose a veneer. The veneer I wanted was a beautiful
burled Walnut, but at $380 for the veneer, I decided to go with
something I could obtain locally. I purchased some Oak veneer
for $20-30 and I also have some remaining if someone is interested.
I attached the veneer to the aluminum using Hexel
structural adhesive. This stuff glues tools to particleboard,
so I figured it would work equally as well on two items wanted
to stick together. So far it hasn't let me down.
KRNET: Well, as most
of you know, our beloved KRNET has a new parent and a new home.
Ross Youngblood has agreed to take over the nurturing duties.
We all owe a huge thank you to Mike Graves for fathering KRNET.
When Mike first started looking at KRs, he was looking for an
alternative to the RV family. He liked RVs, just not the price
to complete one. The KR caught his eye. He then starting seeking
information on the KRs. As you all know, there was little to
be found. Thus the creation of KRNET. Mikes persistence paid
off. We now have a fine forum for real time communication that
allows builders to find answers to their questions AND find questions
they didn't know they even had! Thank you Mike. We wish you
well with building your new home and your new marriage.
Ross has agreed to assume the duties and operations
of KRNET. I asked Ross to tell us about himself. He sent the
"I started my KR project in 1988 as diversion
therapy from work. It was effective, but I changed jobs anyway,
and got so busy that the project slowed in 1989. I picked up
a few years ago, and it now looks like I may actually finish.
My inspiration for newsletter submissions was Monte Miller,
I liked his articles so much in the old newsletter that I decided
to contribute some of my own.
There are several areas in the KR-2 plans set where
we are left to "fill in" the blanks so to speak. I
find that photographs of others projects help a lot to provide
an anchor for these items that have several possible solutions.
Hopefully I can help out by revealing both my good and bad decisions
in my construction phase."
Ross failed to mention he likes people. This is
a needed side of character if he hopes to keep what hair he has
left. We KRNETters can be brutal at time. We all extend a warm
welcome to Ross. He is doing the grunt work, toiling behind the
scenes to help keep the system running. Thank you so much Ross.
Regarding the majordomo krnet mailing list, Ross
1) It's free.
2) Here's how to join:
To subscribe to the KRNET mailing list send an
email to: firstname.lastname@example.org with the following CONTENTS:
"Please include your full name and email address
after the end line. Working with Mike, we found that krnet-l
has to be lower case. If you don't send your full name, I will
email you back asking for it, this is extra work for me."
If you have tried to become a member, and have had
problems, drop me a line email@example.com, and I will fix it
(its my new job).
Your messages to krnet-l will not be posted to the
list unless you are a member.
KR VIDEO: Video Bob is working hard on the editing duties as this is written. The Video should be ready before long. We will review it in KROnline as soon as it is done. Given the fact that Bob spent all of his time over two days behind his video camera, I know there will be a tremendous amount of good footage. I don't envy his task of trying to pare it down to a reasonable length video. Stay tuned
We are looking to create some KR Construction videos. Anyone
interested in helping should Email me direct.
BEARING HELP: KROnline
needs a volunteer to write an article about Oilite bearings.
They were a topic of conversation recently on KRNET, however,
I don't feel the issue was covered as well as it should be. I
have some ideas, but don't have the time to write it and put the
newsletter together. If one of you fine readers would be so kind
as to help me, I'll share with you what little I know that should
get you started. Email me direct.
Yes, KROnline needs a volunteer to write an article on their
experiences in regards to insuring the KR. Email me direct.
ELECTRICAL SYSTEM: At first glance, this gadget may appear expensive but look closer. A truly compact and complete electrical system for your airplane. For sure it cost less than the sum of the elements it replaces.
You can download all of the data about it by going
Price is listed at $249. The information on their web site is very complete. Be sure to take a look. This is a neat solution to a problem most of us face.
TAIL WHEEL SPRING(S): Mike Stearns wrote a note in regards to tail wheel springs:
"I used a standard RR tail wheel...BUT...based on
Roy Marsh's recommendation, I doubled up the tail
wheel spring. This should help compensate for the
longer tail moment of the 2S and the greater potential
resulting downward force on the tail wheel when my
landings are less than greasers.
NEW VW BOARD: There is
a new VW Engine board that has just stated up this month. Still
very new with only about 40-50 people on it, but I suspect it
will grow as it is discovered. Ron Kimball has taken on the task
of running this board. Postings so far have been good.
To get on the board mailing list, Email to: firstname.lastname@example.org
Text should say:
If you have problems, Email Ron direct at: email@example.com
ELECTRIC ELEVATOR TRIM:
Mike Stearns recently wrote:
A couple of you asked about the MAC trim. I paid $159 for the whole works which included the wiring, an electric panel switch and a position guage. Mine is mounted in the elevator itself
against the spar. It only weighs a couple of ounces and should
not effect elevator balance (which is unbalanced anyway). The base of the unit itself became its own inspection plate. The rod
is about 4" long, beefy, and has absolutely
no slop in it.
TURTLE DECK CONSTRUCTION UPDATE:
If you haven't in a while, I would recommend a visit to Mike
Mims web page: http://pw2.netcom.com/~mimsmand/photos.html He
posted good photos and a drawing to explain how he built his turtle
decks. Good food for thought. A refined version of his article
in the September issue of KROnline.
BENDABLE FOAM?: This
was recently the net in relation to Dragon Fly builders. Thought
it would be of interest to KR builders:
The polyurethane foam that we have used for years manufactured by Clark is no longer available, since Clark has closed their doors. The General Plastics Manufacturing Company has purchased much of the Clark line and offers the foam products that we use. The sheet foam for the fuselage is a last-a-foam FR-6700 rigid polyurethane . The wrinkle that we have run into is that the scoring machine that General Plastics acquired from Clark needed some major work at some expense to be operational again. GP elected not to get the machine operational again. There is a bright spot in all of this and that is that GP offers a foam product that can be used in the compound curve areas . The product is last-a-foam FR-4300 thermoplastic foam. The foam is flexible enough to form cold, but with the addition of heat tighter bends can be made and the foam will hold its shape. Short of scoring your own foam the
FR-4300 is the product that we are recommending.
We will be working with Wicks and Aircraft Spruce to supply this product.
GENERAL PLASTICS MFG. CO. P.O. BOX 9097, TACOMA,
WA. 98409 PHONE 206-473-5000
ANOTHER CHOICE IS A FOAM CALLED ESTER CORE MANUFACTURED
BY DIVINICELL LOCATED IN DE SOTO, TEXAS. PHONE NUMBER 214-228-7600.
ONE OF OUR BUILDERS IN FLORIDA HAS USED THIS PRODUCT FOR HIS
FUSELAGE, SAID IT WORKED GREAT AT HALF THE COST.
Aeropoxy PR-2032 laminating resin is an approved
substitute for Hexel Safe-T-Poxy. This product is available at
Wicks Aircraft 1-800-221-9425 and Aircraft Spruce and Speciality
VW ENGINE ASSEMBLE TIP:
If you put anything on your case mating surfaces, it has been
suggested that Yamabond 4 semi-drying liquid gasket. Get it
at your local motorcycle dealer, about $6 for a squeeze tube.
If it works for pressurized 2-cycle cases, it's gotta work for
us, and it does. Bruce Patten smeared some on his C-85 when
he put it back together. The engine leaks everywhere else, but
not around the case halves!
KR FLIGHT NOTE: Ed Janssen
sent in the following on a friend, Dave Davis:
"Dave enjoys buying, doing minor repairs to
an aircraft, fly them for a bit, and sell them in favor of another
project. He has followed this same procedure with a Vari-EZE,
a Taylor Monoplane and now the KR-2 and already has his eye on
a Dragonfly if he sells the KR-2. I failed to mention that the
Vdub is a Type IV, 19?? cc. He reports that it flys much greater
than anticipated (he never flew a KR before, but the Monoplane
experience helped, I'm sure). It was a beautiful evening and
he said that after a little trimming, it easily flew hands off
in the calm air. He's learning to fly it slower on approach (about
65 indicated) which is giving him better landings. He teased
at a stall but didn't get it to break - airspeed showed 45mph.
He only has about 5 hours and 5 landings on it since its cosmetic
work. Forgot to ask him about TT. I'll try to get him to write
LOW COST TOOLS: Ricky
Pitman recently forwarded this information:
I am a builder of a KR-2. I don't know if anyone
has mentioned this before, but there is a source of tools that
are priced right. First I want to say that I have no financial
interest in the company and that depending on the particular tools
you purchase and the price that you pay you will either be pleased
or displeased. The name of the company is Harbor Freight. They
will send you a free catalog if you call them at 1-800-423-2567.
If your order is over $50.00 they will ship for free in the 48
states. (After you have spent two or three hundred dollars with
them they will send coupons for free shipping on any item). I
purchased a band saw for $ 99.00, a table top 1" x 30"
belt sander for $ 49.00, a 2-hp table saw for $ 89.00, a 5 speed
drill press for $ 49.00, a 3.5 hp 12 gallon air compressor for
$ 199.00, and an air stapler/bread driver kit for $ 89.00. The
list goes on. These are not commercial grade pieces of equipment
as the price reflects. But so far everything has worked well
for me. I have completely outfitted my shop with their equipment
for the cost of a good commercial grade air compressor and band
saw. Working the wood with the proper tools is really a pleasure.
This is not meant to be a commercial for their company, but maybe
a way to cut the cost of constructing your aircraft, get it built
right (the first time), and have more time working on the aircraft.
Call the number, get the catalog, and be your own judge. Many
items are covered by a lifetime warranty, and all are covered
by a 90 day warranty.
Before you buy, be aware that the prices seem to
change from catalog to catalog. If you buy something today, you
will get a catalog the next week with the same item for ten dollars
less ( or more sometimes ).
TIDBIT SUBMISSIONS: We
welcome all tidbits and any suggested threads we can follow to
bring more information to the KR builders family. We will credit
you for any ideas submitted. Email KROnline direct with your
discoveries and/or ideas.