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(From CP35, Page 6, January, 1983)
Canopy frame construction - VariEze and Long-EZ.
The following optional method includes several revisions to
the plans procedure that make the canopy frame easier to build:
Cut out and locate the Plexiglas canopy onto the fuselage per the plans. Using gray "duct tape" as a release, protect the fuselage longerons full length from the F28 to the firewall. The F28 bulkhead and firewall bulkhead should also be protected with gray tape.
Now working with 2" thick urethane foam scraps about 12" long, fit them all around the canopy per plans. They should be a reasonable fit to the canopy and to each other. Do not use micro to "glue" these blocks to each other and to the Plexiglas, rather use Liquid X 40, foam-in-place (or an equivalent 2 lb/ft3 "pour-in-place" foam). Mix up small quantities and paint the liquid Into the gaps and joints until the frame is securely bonded to itself and to the Plexiglas canopy. Within an hour you can carve the frame to the required shape per the plans. The "pour foam" joints will carve and sand almost as easily as the urethane and a whole lot easier than micro joints. Glass the "frame" per Long-EZ plans:
1st ply - BID at 45º overall (F28 to firewall)
2nd ply - BID at 45º overall
3rd ply - UND lengthwise, sides only
4th ply - BID at 45º front and rear only
5th ply - UND lengthwise, sides only;
UND side strips should lap 3" onto the front and rear BID.
Allow this lay-up to cure for 48 hours, then Bondo lumber
stiffeners to the canopy frame per plans and remove the entire thing from F28 to the
firewall. Turn it upside down and support it well on two saw horses. (Use Bondo to hold it
firmly). Carve the Inside (including all hard points per plans) and lay-up the same glass
schedule as used on the outside, full length from F28 to the firewall. Allow this to cure
48 hours, then you can cut the front and rear covers off per plans. These edges can be
treated in a variety of ways, flox corners and ply of BID is fine. Several builders have
made lapped or joggled edges using dry micro for a more weather proof joint.
Mike recently installed a "drip tray around the front cover to canopy joint, which really does a job on keeping moisture out of the avionics, even in driving rain.
This is tough to install as a retrofit but can be done easily at the time of the original construction.
Canard Construction - VariEze and LongEZ
Builder support on canards has been quite heavy, particularly
in regards to getting the leading edge foam core bonded to the shear web, on the two
inboard cores, in the correct position, vertically. If this is bonded on too low (relative
to the airplane) the result will be a hollow lower spar cap and a bump in the top spar
cap. This bump in the top cap is a problem, since It cannot be corrected. If yours is this
way, our experience has shown that a small error here can usually be accepted provided a
good job of filling with dry micro and fairing is done. The worst of this problem will be
buried within the fuselage under the canard fairing block and usually will not extend much
more than 10" to 15" outboard of the fuselage sides. A bump of up to 1/16"
at the fuselage side, tapering to nothing at B.L. 25 each side, has not been detrimental
to flying qualities.
A method we have used to eliminate this problem is as follows: Hot wire cut 4 canard cores. Before cutting the leading edge off the two Inboard cores, obtain 6 pieces of wood dowel 1/4" diameter, 6 1/2" long, sharpen one end to a point just as you would sharpen a pencil.
Insert these dowels, equally spaced, into the trailing edge of
the two inboard cores as shown. Push them into the foam, twisting them with your fingers.
They should protrude beyond the shear web cut line by about 1 1/2". Now pull the
dowels out and hot wire cut the leading edge foam cores at the shear web.
Jig the inboard cores, and lay-up the shear web per plans. After this lay-up cures, drill 1/4" holes through the shear web in 6 places where the dowels will go through (use a flashlight to locate the holes). Now bond the leading edge foam cores to the shear web per plans, using micro. Paint micro onto the dowels and push all 6 of them in, until they are flush with the aft face of the canard. Complete the canard per plans. The dowels will guarantee that the leading edge foam cores are perfectly aligned and your spar troughs will be correct top and bottom. We recently built a canard using this method and ended up with a really nice contour, top and bottom, with no bump or hollow place in the spar cap area. Try it, youll like itl
Spark Plugs - The new Champion REM37BY plugs are approved or both Lycoming 0-235 and Continental 0-200. On the 0-235 L2C they are highly desirable due to the excessive lead fouling in these engines. For VariEze builders with close tolerances between cowling and spark plugs, the REM37BY plugs are 3/8 shorter than the standard REM4OE plugs, which can mean the difference between having to install blisters on the cowl or not.
VariEze and Long-EZ CHT - On these airplanes, with updraft cooling, when we measure CHT at the spark plug base, if we install the temperature probe (washer type) on the bottom plugs, which is usual, we are measuring over 40º less than the temperature on the top plug. So keep in mind that if you have a marginally high CHT and are measuring at the bottom plugs, you may even be over the red line. For the record, Lycoming does not measure CHT at the spark plug base. All published data on Lycoming CHTs are taken at the threaded hole on the bottom of each cylinder head. When possible, this is the preferred pick off point.
Detecting fuel tank leaks Most leaks can usually
be detected by the tried and tested soapy water method. Occasionally however, a persistant
small leak may exist that simply will not show up with soapy water. These leaks are
probably located in the forward face of the centersection spar, or on the fuselage side. A
sure fire method to locate these leaks is to use a "Freon Gas Sniffer". These
expensive gadgets can usually be borrowed from your local friendly auto air conditioning
repair man. Simply spray a little Freon into the offending tank, pressurize it by raising
the altimeter no more than 1500 feet. The Freon sniffer will quickly locate the leak. If
the leak is inside the center section spar, you may have to cut through a CS5, CS6, CS7 or
CS8 bulkhead. Cut a plug no bigger than you have to, to get your hand through. Cut the
plug out at an angle so the plug can-easily be floxed back in place.
Repair with two plies BID laping at least 1" onto the
remaining panel. Now that you have the exact location of the leak, you can suck a 1500 ft.
lower than ambient vacuum. Paint warm epoxy over the leak area, working it in with a brush
or rag. Do this for a couple of minutes. Then open the tank to ambient pressure. This is
most important, since the epoxy that was drawn into the leak, would continue to be drawn
in until the leak was once again there. You want the epoxy to cure in the leak area.
Incidentally if you intend to install position lights/strobes and/or antennas in the wingtips, you will need holes in the CS5, CS6,CS7 and CS8 bulkheads to run the wiring and coax through from the wings to the fuselage. A maximum of a 2" dia. hole may be cut through the center of each bulkhead.
Engine Vibration - Occasionally a builder/flyer will call with a mysterious engine vibration. Our own experience in this area has Included, prop balance (never assume even a new prop will be in perfect balance), spinner not running true, baffling touching the cowl (the aluminum, not the neoprene asbestos, which obviously must lap onto the cowl), exhaust system touching the cowl, and one more we had not seen before which Nat Puffer sent in, the hose clamp around the intake manifold rubber sleeve (Lycoming 0-235) was touching against one of the lower dynafocal engine mount donuts. This was not apparent at rest, nor did it occur at run up. Once the engine was turning up a high power, the torque was twisting the engine enough to touch at this point. The result was a high frequency vibration, that was extremely annoying, even worrying.
Cutting Glass Cloth
Marc Boram sent in this hint for easy cutting of glass cloth,
both UND and BID. Marc uses a regular utility knife which is sharpened on emery paper
before and during each use. The key to success is a large piece of sheet rock as a backing
board for the fiberglass. The knife is pulled across the glass at a very shallow 5°
angle, with just enough pressure to cut slightly into the surface of the sheet rock board.
A straight edge is useful for holding the glass in place for straight cuts, but is not absolutely necessary. For curved cuts, lay out the patterns on the cloth with a felt tip pen, then cut them out with the utility knife. Good conservation of cloth and extremely rapid cuts are the result. Sharpen the knife blade often, and remember you can use both sides of the sheet rock.
Caution: Small strips of the cutting surface may contaminate your cloth, so inspect carefully and change your cutting surface often. Glass cloth must be kept absolutely clean. If it is ever exposed to water it should be discarded.
We are still using-recommending the Sterling Primer filler.
While a few builders have reported experiencing problems, our own use of the material has
worked well. The two-part material should be thoroughly mixed at a 50:50 ratio. Do NOT
wait. You have only about 30 minutes of pot life. Either paint it on with a brush or spray
it on. Do not leave it in your spray equipment for too long. This is a urethane material
and if it sets up in your spray gun, that will probably be the end of your gun! One of the
problems we have seen with Sterling has been pinholes. Dick Kriedel sent the following
suggestion - do not use a cheap suction spray gun, these seem to produce many pinholes
using the Sterling. Use a good quality spray gun such as a Devilbiss JGA502 with a
pressure pot. Use fluid tip and needle FF with a 1704 air cap. This is a very large
orifice on the fluid tip and the #704 air cap provides a 12" 14" fan. The
advantages of using a large fluid tip is that you need very little air atomization
pressure to move a lot of paint. The best combination is 15 to 20 PSI on the pressure pot
and 25 to 30 PSI on the air atomization. A big advantage of low air atomization is that
the over-spray is almost non-existent. Most of the paint stays on the work. We were able
to spray Sterling. mixed with up to 25% by volume with micro balloons.
Sterling can usually be sanded within an hour, compared to over 6 hours when using feather fill.
Epoxy Ratio Pumps The manufacturer of the ratio pumps,
has asked us to pass on the following information regarding regular maintenance.
The check ball on the hardener side should be cleaned every 6 to 12 months. It is located just behind the brass fitting on the front of the pump body. The hardener tends to plate onto the ball, which causes it not to seat perfectly. This allows hardener to drain slowly back and it may not flow on the first stroke of the pump at the next use. Simply take the fitting off, clean the ball and seat with solvent or newspaper, and replace the ball, spring and fitting. Another option is to "coin" the seat by putting the ball in place and striking it gently with a brass punch and hammer. This will assure a perfect seal. Be careful that the spring does not get caught in the threads when reassembling pre-1981 models.
Remember to subtract the weight of your containers before calculating the ratio, when checking your pump ratio.