There are commercial products
that are compatible with acrylics that can be used for removing tape
residue. Ensure that any product which touches the acrylic canopy is
compatible with acrylic. Kerosene or avgas can be used in a pinch. Do
not use alcohols, ammonia or glass cleaners as these will cause damage
to the canopy over time. Spraylat can be softened and removed easily by
applying one or two new coats, then peeling it off as directed.
18.6 - Can a Lancair 320 canopy bubble be used on the Cozy?
A few builders have opted for the Lancair 320 bubble because it is
rounder and wider in almost all dimensions when compared to the Cozy IV
bubble. You will need to make some modifications to the turtleback and
canopy frame, however. Other builders have had custom canopies made to
suit their requirements. Note: these are not an approved Cozy
modification. Check the archives for more details.
18.7 - Can I make my own side windows?
Yes. Once you have got the turtleback made, you can cut your
windows from 1/8" acrylic material, heat the windows on a cookie sheet
in the oven, and then drape-mold them over the turtleback or mold. Wear
gloves! We do not recommend performing this heating in a gas oven as the
acrylic may catch fire if it gets too close to the flames.
- Cover the turtleback with plastic tape for release and then make
a mold over it using cheese cloth and plaster of paris. Messy, but
it works. Mold should be at least 1/4" thick (6 layers of cheese
cloth minimum) 1/2" would not hurt.
- After the plaster dries, drill two small holes at opposite
diagonal corners through the turtleback and through the plaster for
future reference.
- Remove the mold and cut out the window opening in the turtle
back. Do a nice neat job finishing the inside edges.
- Take the mold, the portion of the turtleback you cut out, and get
a piece of aluminum sheet to lay the plexiglass on while it is in
the oven.
- Once the oven reaches 275 deg F, lay your plexiglass on the
aluminum sheet and insert into the oven for about 5 minutes. It will
curl up slightly and then lay back down. Remove it just before it
completely flattens again.
- Put on a pair of oven mittens and remove the plexiglass and
aluminum from the oven. Gently slide the plexiglass onto the mold
and then place the foam portion you removed from the window cut-out
over the plexiglass to hold in place while it cools. You will have a
glass/foam, plexiglass, plaster mold sandwich.
- After it cools, use the foam cutout and mark around it with a
magic marker. Use the holes in the plaster mold as a guide for
positioning it.
- Mark it again 1/2" wider than the foam cutout, trim to this line,
and voila', you have got a window!
- Trim the inside of the turtleback and remove the 1" strip of
fiberglass and foam where the window will go.
- Lay the plexiglass in the opening and mark it with a fine felt
tip marker. Use this as a final guide for placing the acrylic tape.
- Rough up the edges and place weights on the backside of the
window to hold it in place while the flox cures.
- Install the 1" strip and bid tape after the window has cured in
place.
18.8 - Any advice for locating the window placement?
The following will give you the basic outline of the windows--you
will still need to check accuracy by laying the windows over the outline
to make sure that they are about 3/4" larger then the marked outline. If
things still look good, radius the corners of the outline and recheck to
make sure that the windows will fit properly. Do not cut anything unless
you already have the windows in hand.
- Measure up along the front curve of the turtleback and place
marks at 2-3/8" and 16-1/16".
- Measure up along the back curve of the turtleback and place marks
at 5-1/4" and 12-5/8".
- Run a piece of masking tape between the two upper marks and the
two lower marks. (This just makes it easier to draw the lines.)
- Remark the above dimensions and clamp a flexible straight edge (a
6' aluminum ruler works real well) between the bottom front and
bottom rear marks using spring clamps (or whatever). Draw a line
between the two points.
- Do the same thing for the top marks. These delineate the top and
bottom of the windows.
- Hook your tape measure to the leading edge of the turtleback at
the lower mark. Measure back and place marks at 5-3/16", 18-1/4",
24-13/16" and 38-7/16".
- Move to the top mark and measure back 5-3/16", 24-15/16", 31-1/4"
and 39-1/8". (Again, run a piece of masking tape between the marks
to aide in drawing the line.)
- Use a straight edge to connect the top and bottom sets of marks.
18.9 - Is there an alternative method to hold the rear windows in
contact with the turtleback outer skin during cure?
If you cannot manage the Cleco's, another solution is to clamp a 2"
x 4" the full length of the turtleback, then insert soft foam wedges
between the 2" x 4" and windows. Be aware that the windows do not always
have the same curvature as the turtleback, so you can expect some minor
flox filling. If this is unacceptable, you can shape the windows to the
exact curvature by heating them in your kitchen oven to about 150-270
deg F until soft. (See question/answer 18.7.)
18.10 - How can I make the canopy hardware accessible and
removable?
As called for in the plans, most of the nuts and bolts holding the
canopy hardware in place becomes inaccessible once buried under with
micro. You can provide accessibility for removal later by enlarging the
recesses in the glass and foam to install nut plates. Use long rivets
(not driven, just floxed into the holes) to secure the nut plates.
18.11 - Any good ideas on how to make the canopy water/wind
tight?
Most builders are using some form of weather stripping or pliable
gasket, while others are applying a bead of silicone. For the
turtleback, some builders have built up the drip rail with micro and
have closed off the ends of the drip rails with BID to direct the water
onto the side longerons.
18.12 - What is the best way to secure the canopy hinge pins in
place?
There are three general methods:
- Drill a hole in each end of the hinges (or hinge pins) and secure
with a small cotter pin or safety wire.
- Apply silicone into each end of the hinges
- Make a small loop in one end of the hinge pin and secure in place
with safety wire or a screw.
The last idea has additional merit as a rescue feature: if the loops are
made big enough, a rescue squad could pull the pins out to release the
canopy -- although, so could thieves for that matter . . .
18.13 - What should I do if my canopy latch hardware does not
line up?
Because of the curvature in the longerons, the aluminum rods will
need to be bent slightly to align the rod ends with the threaded
fittings. Fit the straight tubing first, then determine where to place
the bends, and finally, gently bend the rod in increments over something
rounded (like the handle of a hammer) until you get the desired fit.
Remember: this is an iterative process and it requires patience to get
all the latch fingers to catch and secure the canopy equally.
18.14 - Is there an emergency egress system to unlatch the canopy
from the rear seats?
Many years ago a supplement was issued to the Long-EZ plans which
showed details of an alternate latching system with an emergency release
cable running to the rear seat. The supplements may still available from
Debbie Iwatate. Alternatively, consider that the turtleback bulkhead and
the head rests are wide enough for a small-to-average-sized adult to
wiggle through to access the canopy latch.
18.15 - What canopy gas strut do I need?
The archives mention lots of struts that will work and as many
methods and locations for mounting. Here is one set of part available
from NAPA (an automotive parts store):
OLD:
Description |
Manu. P/N |
NAPA P/N |
Gas spring |
SPD-5150-40 |
819-5587 |
Ball stud |
SPD-1005 |
735-1591 |
Bracket |
SPD-1010 |
735-1592 |
NEW:
Description |
Manu. P/N |
NAPA P/N |
Gas spring |
SPD-5150-40 |
819-5587 |
Ball stud |
SPD-1005 |
735-1896 |
Bracket |
SPD-1010 |
735-1897 |
18.16 - What is the preferred geometry for mounting the canopy
gas strut?
Again, beyond the plans dimensions, it is a builder's prerogative.
Keep these guidelines in mind:
- The gas strut puts pressure on the structure. So do not select a
strut that applies so much force that it breaks the structure.
Conversely, beef up the structure so that the strut will not cause a
failure.
- In the closed position, the strut should be pushing the bulkhead
away from the shell of the turtleback and away from the hinge.
- Lowering the head-rest pivot point reduces the force needed to
open the canopy, but lowering it too much means moving the canopy
mounting point further outboard to maintain the opening angle on the
canopy.
18.17 - How do I make a one-piece cover for the instrument panel?
A lot of the builders are making the fuselage top as one piece
between F28 and the instrument panel. This allows complete
access to the instrument without removing the canard. Here is the
process:
- Chapter 18, step 15:
- Do not use the 1/8" spacer as shown in Figure 63. Just place a
piece of tape instead.
- Chapter 18, step 16:
- Do not apply box sealing tape to F28. Apply it to
fuselage top instead. This makes the 4-ply angle piece permanently
attached to F28. You then have the option of installing
the 5 screws through the fuselage top instead of through F28.
Some people have chosen to eliminate most or all of the 5 fasteners.
- Chapter 18, step 17:
- Forget all the tabs on instrument cover. Just permanently attach
cover to fuse top.
Chapter 19 - Wings, Ailerons, & Wing Attach [as of: 10
oct 99]
[distiller: John Slade]
Comments and Tips
- Use a laser pointer to align the wing jigs. One builder offers
the following procedure: Use a 12 ft long straight board. Put lag
screws through each two feet along both edges and use them as
leveling screws. Bondo the screws to the floor. By adjusting the
height of the nuts you will be able to get the board exactly level.
Bondo the forms to this board and align with the laser pointer.
- Use a long tube with color water (a water level) for leveling
things. A hose pipe with fittings and a clear tube at each end works
well.
- A piece of shower curtain rod cover tubing from Walmart or K-mart
works nicely for electrical conduit in the wing.
- If you want flush rudder belhorns, get plans for the Cozy MKIV
from AeroCad or for the Long-EZ by
sending $10 to:
Rutan Aircraft Factory
1654 Flightline
Mojave, California 93501
(THESE ARE NO LONGER AVAILABLE - RAF HAS SHUT DOWN!!!)
- Read the chapter 20 section of the FAQ
before starting this chapter.
- Sand a joggle in the wing foam to avoid a bump when adding the
winglets.
Left in the Archives
- Drilling holes in completed wings
- Wing washout history
- What to do with a melted wing
- How to remove and install your wings by yourself (see message from
Bill Theeringer dated Tuesday, 23 June 1998)
- Lots of different tips and tricks for aligning and attaching
wings.
- Aileron end ribs
- Oxidation of A13
- Wing root shield
19.1 - Are the wing airfoils standard Eppler 1230?
No. They are modified.
19.2 - Is there a difference between the Cozy IV and Cozy III
wings?
Yes. The buttline locations are different and the Cozy IV wings are
4" longer.
19.3 - What material should I use to build the wing jigs?
Build the wing forms out of 5/8" or larger plywood. Anything less
is too weak.
19.4 - Why is there a kink in my trailing edge at BL 67.5?
Do not worry. It is supposed to be there. Simplest thing to do is
leave it there. Some say it is cosmetic only, is a carry over from the
Long-EZ cowling shape and is not necessary on the MkIV. AeroCad
have removed this kink in their prefab cores and wings. It would be
quite hard to remove it manually by redesigning the jigs. If you do
remove this kink and make a straight trailing edge, then your cowling
wont fit properly unless you get it from AeroCad. AeroCad cowlings fit
either wing type.
19.5 - What shape should my wingtips be?
The area where the strobe and position lights attach obviously has
to be flat because the base of the light fixture is flat. The area of
the wing tip forward of the light fixture is aesthetic. Any shape
(within reason) will do. It is up to individual taste.
19.6 - Is the sheer web cut supposed to be 90 degrees to the
waterline?
Yes.
19.7 - What is the technique for cutting out the spar caps?
Yes. When cutting the wing cores, use mixing sticks (with 2 nail
holes) to temporarily continue straight over the spar cap troughs. Then
remove the sticks and cut out the troughs as a separate operation.
Presto no wire lag problems, nice neat corners.
19.8 - Is my chord length going to be wrong when I glue the
leading edges back on?
No. Plans dimensions allow for this.
19.9 - What about covers for the wing attach bolt access holes?
Before glassing the wings, sand a slight depression around the
attach holes to accommodate a 5 BID cap with a shoulder. Make two caps
for each wing and cure in place. Drill [not through the spar cap] a hole
between the two holes and use a soda straw to allow moisture to drain.
Drill a small drain hole in the lower cover. Glass a small aluminum
plate with a nut plate attached to the top cover. Connect the two covers
and hold them in place with a long bolt from the lower cap to the upper
cap. An alternative to the bolt is a spring in a tube which attaches to
hooks on inside face of each cover. Use micro to form a smooth
transition from the wing surface to the cover.
19.10 - How do I ensure a straight trailing edge when adding the
top skin?
Use a long aluminum extrusion to keep the trailing edge straight.
Home Depot sell these for screen enclosures. AeroCad
supplies an aluminum T-bar with their wing cores for this purpose. Mask
most of the extrusion with plastic shipping tape and leave a strip of
aluminum exposed. Glue this strip to the bottom skin trailing edge. Use
weights and clamps to get the trailing edge straight against the
extrusion. Once the top skin is cured, use a very thin putty knife to
pop the extrusion from the bottom of the wing.
19.11 - Is there an easy way to get the 1-inch wide peel ply
strip off?
Use a razor knife to score the foam at the forward edge of the peel
ply. This way, when you pull up the peel ply, the foam will break off
evenly. Use pliers to pull up the peel ply. Do not leave it on for more
than a few weeks.
19.12 - Why is the aileron cut-out parallel to the center line?
KISS. It is much simpler to make it that way and it looks fine when
finished. Some builders have changed this, and the cuts end up being
canted. However, if you do not get it just right, you will restrict and
/ or bind the ailerons.
19.13 - How do I ensure straight cuts when cutting the ailerons
out?
Bondo a straight edge to guide the cut, then use a strong razor
knife or hacksaw blade held almost level with the surface.
19.14 - Should I make my Ailerons longer than plans?
Apparently Dick Rutan and the Berkut both extended the standard
ailerons as well as AeroCad whose
ailerons are 6 inches longer than the Cozy. Jeff Russell says that this
results in a noticeably faster roll rate. Longer ailerons are NOT
recommended by Co-Z Development. It is your choice. If you do extend the
ailerons, and also plan to install hidden belhorns, be aware that the
rudder conduit goes very close to the tip of the aileron.
19.15 - How can I remove epoxy that snuck into my hinges?
Try using a soldering iron on the offending hinge. You should get
enough heat to burn the epoxy around the pin without damaging the
surrounding structure.
19.16 - Does it matter that my cores are not completely straight
along the aileron and rudder hinge lines?
Yes. If the hinge line is bent the hinges will bind. Fix this
before skinning the core.
19.17 - Do the plans hinges wear too much?
Some think they do, especially if your hinge lines are not
perfectly straight. Get the teflon hinge kit by sending $27 ($32
overseas) to
Gary Hall
851 S.W. 63rd. Ave
North Lauderdale, FL 33068
or Email gary.chris@comcast.net.
19.18 - Should I worry about the clearance on the ailerons?
Absolutely. Be very careful about this. The October 1999 Central
States Newsletter carries a story about an EZ driver who had his
ailerons lock up with full deflection during high speed maneuvers. G
forces cleared the problem. On landing, marks were seen which indicated
that the aileron had caught on under the bottom wing skin. The aileron
clearance is critical full span.
19.19 - Does anyone have a neat way to attach the aileron hinges?
Yes. Everyone does. The plans do not tell you how to make the
aileron side of the hinge come into contact with the aileron while the
bondo cures. Everyone seems to have a different trick for this. The
favorite seems to be wedging something under the hinge. Stiff earplugs
or foam are suggested. One builder said that he used bondo on the
visible / accessible edge of the aileron side of the hinge and it held
just fine.
19.20 - Does it matter if the clearances between the aileron and
the wing are different for the left and right sides?
Yes. This can produce a roll tendency. Builders have used gap
sealing tape to demonstrate this.
19.21 - What should I do about the wing root area?
Carve out the root area a little deeper then you think necessary in
the area around the aileron torque tube (the plans call for depressions
but it is unclear how deep to make them). Test the hardware in the area
before laying up the glass.
19.22 - Is there a better alternative to the plans phenolic
bearing in the wing root?
Yes. Many builders are using a spherical teflon, UHMW (ultra-high
molecular weight polyethylene) or Delrin bearing here. Typical solutions
include a kit from Infinity
Aerospace, and another from AeroCad.
Numerous bearing manufacturers are suggested by builders in the archives
including a Spherical Bearing part no. COM-10 made by
FK Bearings Inc.
11 DePaola Dr.
Southington CT 06489
phone: (800) 662-06489. One builder got his from a local distributor:
Allied Bearings & Supply at (615) 255-1204. Cost was ~$10 each.
19.23 - How important is the weight of the aileron?
Very! Stay within plans guidelines for weight and balance of
ailerons. Do not increase the weight of the mass balance rod to
compensate. If your ailerons will not balance per plans, scrap them and
build new ones. Use minimal filler and primer on the ailerons during
finishing.
19.24 - How should I fill my spar caps to match the contour?
Use additional roving threads as needed. Use strips of UNI to fill
any dips. Do NOT fill with micro because you need a glass to glass bond
between the spar cap and the skin.
19.25 - What if I cannot get the last layer of material in the
spar cap?
This is typically ok, as long as you double checked your spar cap
depths before starting. Use the tolerances given in the plans.
19.26 - Can I use micro to bring the spar cap up to contour?
Absolutely not, NO. The cap to skin bond is fundamental to the wing
design.
19.27 - Why does my spar cap dip at BL 67.5?
It is supposed to be there. (See FAQ 19.3.)
19.28 - What is the best method for drilling the wing attach
holes?
The archives are full of discussion on this issue. Consensus is
that the plans recommended spot face tool is not adequate for the job.
It takes a Loooong time, gets very hot, and dulls quickly. In addition,
the excess heat can damage the structure. Various cooling methods are
offered including water. One builder even went through a couple of
spotfacers before trying a different method. Many suggest using a hole
boring tool such as the Morse #TAIO-5/8" high speed hole saw. Use a 1/4"
pilot hole and a long 1/4" pilot bit. Be careful to ensure the hole is
concentric with the pilot hole. If the holes come out a little large (as
much as 0.007" over) RAF say its ok to fill them with flox and cure
while the wing is bolted to the spar. Nat does not like this approach. A
popular method is to grind or use light taps with a hammer to make the
hole cutting tool bore the correct (smaller) size. Another option is to
manufacture LWA9 bushings which will fit the hole resulting
from your boring tool. Others bore undersize and ream the hole to fit
the bushings. One solution was to drill a pilot hole, then expand the
hole with a drill bit on slow speed, then finish off with the spotface
tool just before the drill bit breaks through.
19.29 - What if I drilled my pilot hole in the wrong place?
Plug the hole with flox and drill a new pilot hole. If the final
5/8" hole encompasses the plug then you are fine. If it does not you are
talking with Nat.
19.30 - Does the spacing between the wing incidence bolts matter?
Yes. DO NOT DECREASE this spacing from that specified in the plans.
19.31 - What is the most critical part of wing attachment?
Getting the relative incidence between wings and canard correct.
19.32 - Can I avoid routing the antenna coax along the foam
surface?
Yes. One builder describes how to drill the winglet about 1 inch
from the leading edge, then feed the coax through the hole. A second
hole is drilled from the balun area to intersect the first hole and the
coax is snagged with stiff steel wire. In the case of a NAV antenna in
the wing a hole is drilled from the balun to the electrical conduit.
19.33 - Should I add a fourth attachment bolt to eliminate wing
float?
Wing float (movement of the wing relative to the strake during
flight) occurs. It is part of Burt's (and Nat's) design. Do not worry
about it and do not add an additional bolt. (See 21.3
for more discussion.)
19.34 - Can I make rudder belhorns which do not stick out?
Yes. This is the "internal rudder belhorn" modification. See comments
and tips section of this chapter.
19.35 - What are the "V"-shaped layups over the wing attach
points for?
The "V"-shaped layup over the wing attach points are reinforcements
to help collect the load and transfer it to the center spar. In Chap.
19, p.6, Fig. 32 the 2" wide layup across the corner is at a point of
stress concentration, and your paint might crack there if you leave it
out. The 12" layup in the valley is where the maximum bending and drag
(pushing backwards) loads are. The drag loads are compressive loads
which tend to buckle the skin. A little extra skin thickness at this
point provides an extra safety factor when exceeding Vne.
19.36 - Can I make my position lights flush?
Yes, provided you do not cut into the UNI and BID cloth that
attaches the winglet to the wing. JD at Infinity
Aerospace may be able to put you in touch with a builder who makes
airfoil shaped lens that covers the entire nav-strobe-tail light
combination.
19.37 - How can I construct wing tiedowns?
One builder used small hole/tubes behind the wing spar about 16"
inboard of the winglets. He inserts I-bolts, washers and nuts that go
through the tube and then reach a standard width tiedown. Also carry
rope and "twist-in" tiedowns. Robin du Bois produced some drawings for a
simple tiedown which are available from http://www.cozybuilders.org/.
19.38 - What is the best way to store my wings so they will not
warp?
Out of the sun and away from heat. Support them leading edge down
with pads or straps. Others make an airfoil shaped jig lined with carpet
and store the wings vertically, leading edge down. Keep them away from
high temperatures and temperature fluctuations. You will need less space
if you do not attach the winglets. Webbing used to repair lawn chairs
seems to be a popular material for supporting the leading edges.
Chapter 20 - Winglets and Rudders [as of: 29 mar 2010]
[distiller: John Slade]
Comments and Tips
- When positioning the lower winglet: attach the lower winglet to
the upper winglet prior to mounting. Notch-out the lower piece and,
after the upper winglet is mounted, reattached the lower piece that
was cut out. This creates a perfect alignment of the upper and lower
winglets.
- In order to make the winglet tips, some builders cut the winglet
cores overlength, then sand the styrofoam rather than adding the
urethane tip later.
Left in the Archives
- 1/8 inch rudder cables
- Rudder cables of Canadian Cozy's Eppler 1230 Airfoil
20.1 - Can I leave the lower winglets off?
No, absolutely not. In the aft CG / deep stall testing that Nat
performed, it was discovered that the lower winglets add considerably to
stability; and he strongly cautioned builders to retain them.
20.2 - Can I do the rudder cutouts before attaching the winglets?
No. The rudder includes part of the lower winglet. You need the
winglets attached to get the correct cut.
20.3 - Why is there not a mass balance on the rudder?
Rudder mass balance is not needed if your return springs and
stops are properly installed.
20.4 - How long should I make my COM antenna cable from the
winglet?
Most builders run the cable to be a few more feet longer than the
wing. Then they use a BNC splice within the fuselage and add cable as
necessary to reach the radio stack.
20.5 - Could someone explain how the 8.5" by 3.5" cutout applies
in Chapter 20?
The upper right hand corner of chapter 20, page 1 shows the foam
block cores for both the "Upper" and "Lower" winglets. The lower part of
the pictures is showing the "Lower" winglet. The 8.5" dimension is the
height of the lower winglet. The 3.5" dimensions is showing you how to
cut the blocks so that you get the "aft" sweep of the lower winglet as
you go from WL 18.4 downward, i.e., the lower winglet sweeps back as it
goes down. Remember the upper and lower winglets are cut out separately
and microed together later.
20.6 - Is there an error in the plans winglet templates?
On the Winglet BOTTOM Tip Template (shown on drawing M-20), the label has left and right reversed. The note should be changed to “This side for RT. Transfer numbers to other side for LT”.
All other notes are correct. Nevertheless, the templates can be confusing. The following is an alternate description of the correct winglet template orientation:
- Upper winglet tip (top): flat side OUTBOARD / curved side INBOARD
- Upper winglet root: flat side OUTBOARD / curved side INBOARD
- Lower winglet root: flat side OUTBOARD / curved side INBOARD
- Lower winglet tip (bottom): flat side INBOARD / curved side OUTBOARD (!)
* In the correct orientation, all “INBOARD” label arrows will point toward the wing, and all fishtails will be on the same side (also toward the wing).
20.7 - Should I make my rudders wider or full span?
One builder says yes, the rest say no--definitely not.
20.8 - Where should I put the drain holes in my winglets?
Drill a small (1/16" to 1/8") hole on the inside bottom winglet at
the lowest point when the airplane is parked nose down. This is to keep
water out of the pocket you made for the belhorn. Also drill similar
holes in the nose on each side of NG-30 so if water gets in
the nose it will also drain.
20.9 - What if my rudder has a kink in it?
This is expected. Nat says,
because of the airfoils and the different chord lengths, you
cannot have both the outside surfaces in the same plane and the
trailing edge straight.
When asked which way is preferred, a bent TE or a canted winglet, the
answer given was, "bent trailing edge."
20.10 - Is there an error on the trailing edge dimensions on Page
1, Figure 1?
Yes. The foam block layout diagram shows 47" for the trailing edge,
but the larger detailed drawing on the same page gives 48" for the same
dimension (40" rudder, plus 9" above rudder, minus 1" urethane foam
cap). To correct it, one can change the 47" to 48" on the foam block
layout, or change 40" to 39" on the rudder. According to the mailing
list archives, Nat Puffer felt that the 1" error made no practical
difference.
Chapter 21 - Strakes [as of: 15 sep 01]
[distiller: Wayne Hicks]
Comments and Tips
- If at all possible, attach the wings when building the strakes to
assure a perfect match. If space will not allow it, cut out a
quarter-inch plywood panel in the shape of the wing's profile and
bondo or glue it onto the outboard end of the spar.
- The top and bottom strake skins are identical except that the top
is 0.2 inches longer along the R33 and R57
ribs. Use one to make the other.
- Make sure the landing gear and jig tables are blocked off to give
the strakes a solid foundation.
- Install release tape along the aft edge and fuselage side of the
table before bondoing the table in place.
- Reference lines drawn onto the jig table are a tremendous help
when installing the R33 and R57 ribs. The BL33
and BL55 stations can best be determined by extending a
straight-edge across the longerons at the instrument panel and
measuring outward 33 and 57 inches respectively.
- At a minimum, peel-ply all inside skins for 2 inches on either
side (4 inches total) of where the ribs and bulkheads will contact
the skins. This will significantly reduce the amount of prep sanding
required for subsequent BID taping. It is a very good idea to
judiciously peel ply the entire inner strake surfaces with each
epoxy coating. This will eliminate pin holes and significantly
reduce chances of leaks.
- The BL dimensions are to the Inside face of the
bulkhead. Carve the outside (farthest from the fuselage) to get the
contours of the bulkheads to match the sweep of the strake. Do not
carve the inside edges.
- Run a string from the 17.4-inch water mark on the wing (or spar
template) to the 17.4-inch mark at the FS60 location on
the fuselage side. Use as a guide to set the leading edge bulkheads
straight and level.
- The 1-inch spacing is fine for scoring the bottom foam to bend
around the bulkheads. One-half inch cuts are better for scoring the
top foam. The smaller spacing minimizes the flat spots that occur on
the top of the curved part of the strake between the two bulkheads.
- Small, 5-inch kitchen colander strainers make ideal screens for
the holes to the fuel sumps. Buy these colanders from any kitchen
store. Simply cut off the handle and flox the rim into place.
- Fully trim the fuselage strake openings before putting the top on
permanently so that you can repeatedly match up the top skin to the
same place on the fuselage.
- The rib flange or "T-hat" method of attaching the top strake skin
to the ribs is highly recommended. (Description of process is
provided below.)
- It is a ton of work to tape all inside edges after floxing the top
skin to the bulkheads. But try to do all taping in the same session
to save yourself from having to prep sand while upside down in the
back of your airplane.
- Process for Constructing Rib Flanges (a.k.a, the "T-Hat Method")
This process involves installing BID flanges onto the top of the
ribs and bulkheads. Although there are no reported issues with the
plans method, builders feel this process increases the surface
contact area for adhering the top strake skins to the ribs, and it
also reduces the chances for leaks. Be forewarned, this method
does add several cure cycles and several days to the strake
construction process.
- Make sure all ribs and bulkheads are trimmed to closely match
the inside strake skins.
- Place the top skin on the strake. Use a felt marker to draw a
line where the ribs and bulkheads contact the upper skin.
- Apply 2 pieces of 2-inch wide duct tape along each side of the
mark on the inside skin.
- Make up some 2-inch wide, 2-ply BID tapes and peel-ply one
side of the BID tapes. (Some builders prefer 1-ply BID tapes.)
Apply the tapes onto the top inside strake skin, centered on the
line with the peel-plied side touching the inside strake skin.
You only need to do this for the interior fuel tank edges. Do
not extend the flanges into the storage area since you will be
taping these areas like normal.
- Do not put any peel ply between the BID tapes
and where those tapes will contact the ribs and bulkheads!
- Apply micro to the top of each rib. (Yes, the plans say
"flox", but that comes later. In this step, the micro is used
like foam to merely fill in any gaps between the top strake skin
and the ribs/bulkheads.)
- Install the upper strake skin in place, weight it down, and
let it cure. The BID tapes will permanently bond to the ribs and
bulkheads in an exact fit to the strake skins.
- After cure, pop the top strake skin off. Remove the excess
micro from under the "T-Hats"(flanges) tape at the top of the
rib. Radius the micro and prep sand the underside of the tape
and the top of the rib sides.
- Tape the flanges to the ribs and bulkheads by applying a 1-ply
BID tape (2 inches wide) on the underside of the flange onto the
top sides of each rib and bulkhead. Let cure.
- Remove any peel-ply from the tops of the flanges and prep
sand. Remove all duct tape from the inside strake skin and
prep-sand. Apply a heavy coat of epoxy to the inside strake skin
and wait for the epoxy to reach the slightly tacky state.
- Apply wet flox to the tops of the flanges, put the upper skin
in place, and weight it down heavily to ensure a good flox
squeeze. Scrape away excess flox from accessible areas.
Left in the Archives
21.1 - Do I need to treat the exposed foam in the cut-outs
through the bulkheads?
Technically, no. The bulkhead foam is impervious to aviation fuel
and does not allow the fuel to permeate through the foam. Some builders
suggest smearing a thin layer of micro or flox to keep any foam flecks
for getting into your fuel strainer and system.
21.2 - Why can I not use the area between the TTE bulkhead and
the spar for fuel instead of pour-foam?
At 6 lbs/gallon, the fuel weight in that area would greatly limit
the aft CG envelope for the plane, possibly resulting in main wing
stall. A Velocity pilot did not follow this advise and ended his flying
career in with an inverted flat spin. If you think you ever need more
fuel for longer range, install an auxiliary tank in the back seat.
21.3 - Do I need a 4th Wing Attachment point between the strake
and wing leading edge?
No! There is no technical or structural reason for doing this. The
center spar/strake combination results in a structure so stiff that the
wings do not twist at flight loads. As for the history of this question,
some German aviation authorities made a political decision to require
Long EZ builders to put a 4th attachment point where the wing leading
edge meets the strake. Burt Rutan adamantly objected to the change. Cozy
Classics built in Germany had to adopt the 4th attachment point too.
(See 19.33 for more discussion.)
21.4 - What will I need to do differently if I am using the
Featherlite Leading Edge Kit?
The kit's leading edges eliminate the need for the leading edge
baffles (TLE and BLE). They also wrap several
inches back onto the R33 and R57 ribs, so you
will need to modify the noses of your ribs slightly and shorten the top
and bottom strake skins per the kit's installation instructions. If you
plan to use the leading edge kit, order them and have them delivered
before starting on the strakes.
21.5 - What epoxy is best for sealing the fuel strakes?
Safe-T-Poxy is generally considered the best to use, but in
general, all of the approved laminating epoxies are okay to use too. Do
not use commercially-available sealing agents as some are not compatible
with some epoxies and can flake off and clog your fuel system with
disastrous results.
21.6 - How do I get a good seal inside the strakes and ensure
coverage of pin holes?
Follow the plans and use generous amounts of epoxy. What you are
shooting for is a tank with a nice, clear, pure epoxy lining. Work the
epoxy with a squeegee or brush focusing on getting good coverage along
all joints, fuselage sides, center section spar, end rib, vents drains,
and caps. Some builders wait for the epoxy to become tacky before
applying the next coat. Cover with peel ply or plastic, and verify no
air bubbles exist.
21.7 - What are the pros and cons of installing strake windows?
Opinions vary. General consensus is strake windows are nice for
backseat passengers, but useless for frontseaters. The windows tend to
get scratched up too over time from items stored in the strakes. If you
choose to use strake windows, do not make then too large. You must
maintain the structural integrity of the bottom strake skin. See
archives for suggested window dimensions.
21.8 - How does one get remarkably straight and narrow seams
between the wings and strake junctions?
The general procedure is the glass over the existing joint with a
2-BID tape. After cure, bondo a straight-edge lined up with the center
of the joint, then use a razor saw or hacksaw blade to cut the joint
back open.
21.9 - Why is the fuel valve on the seatback?
The Cozy's seatback location eliminates some of the fuel lines
running through the cabin but retains the ability for the pilot to place
the hand directly on the valve, see the position, and feel the detents.
Earlier Vari-EZ's and Long-EZ's have reported problems with
remotely-located valves operated by cables or torque tubes. Rutan
Aircraft Factory eventually issued a change order to instruct builders
to place the valve within eyeball's reach.
21.10 - Which fuel valve should I buy?
There are many choices, but whatever you buy stay away from an
Imperial valve!! The Imperial valve has a brass body and a tapered plug
that eventually sticks and jams. Not good! The Cozy plans recommend the
Weatherhead valve, which has a delrin spool inside a brass body that
eliminated the sticking problems.
21.11 - If I am installing a fuel injected engine, do I need a
fuel return line and a two-channel fuel valve?
Most Lycoming IO-360's and converted O-360's do not require a
return line for returning high pressure fuel back to the fuel tanks.
Check with your authorized Lycoming representative to be sure. Some
builders are installing fuel recirculation systems to avoid problems
with hot-starting. These systems consist of a fuel relief valve and
return line. Prior to starting, the pilot opens the relief valve
upstream of the fuel distribution spider, turns on the electric fuel
pump, and pushes cool fuel through the fuel system and back to the tank,
thereby purging any hot or vaporized fuel.
21.12 - Do I really need to run the fuel vent lines to the top of
the firewall and then back down underneath the strakes?
Yes! This greatly reduces the risk of fuel draining out if the
plane tips over in a crash. It also reduces the risk of the lines
picking up rain and freezing in flight.
21.13 - Why do I hear double vent lines mentioned occasionally
and why should I install them in my strakes?
Although there has never been an official change to the plans, most
builders are installing two vent lines per strake. The purpose of the
second vent line is to provide venting at the highest strake position
when the plane in parked on its nose, and for redundancy should the
other vent become clogged. The first is installed as per plans and the
second is installed against the fuselage just forward of the spar. Both
lines exit the strakes in the plans location and are run to the top of
the firewall and back below the strakes.
21.14 - Do I really need fuel probes and gages in addition to the
site glasses?
It is builder preference. Some pilots do not like having to look
over their shoulders at the site glasses. Also, the site glasses can be
obscured when luggage is piled into the rear seats. Some pilots find
that fuel gages on the panel help remind them to stay vigilant about
fuel management.
21.15 - What fuel caps should I buy?
Aircraft Spruce and Wicks both stock good fuel caps, including some
very fine lockable fuel caps made by Newton (an English company). The
Brock caps have a reputation of leaking fuel while flying and leaking
water when parked.
21.16 - Do I need to secure my fuel caps so that they never go
through the propeller?
The fuel cap location of the Cozy IV is outside of the prop arc, so
no changes are necessary. Still, it is a good idea to use an anchor
chain to keep from losing the cap if it inadvertently opens in flight.
21.17 - Any tricks for installing the fuel caps?
The easiest way is to install the filler spouts before putting the
top strake skins on. This is out of sequence with the plans and it might
complicate leak checking, but it certainly minimizes debris into the
tank. Alternately, some builders flip the plane over (top side down),
carefully cut away the outside skin and scrape away the foam on the top
strake, pressurize the tanks slightly, then drill the hole for the
filler spouts. Some builders avoid creating debris by cutting through
the top skin with a heated knife.
21.18 - What is the best way to vacuum debris out of the strakes?
Most tank contamination occurs when drilling the holes in the top
strake skins for the filler caps. If you just poke your shop vacuum hose
in the tank, the air that gets sucked out gets replaced by air rushing
into the tank. The air rushing into the tank will disperse the debris
away from the vacuum hose and deposit it throughout the tank, leaving
you with the mistaken impression that the debris has been vacuumed up.
This is why the plans say to duct tape a small diameter hose (vinyl
tubing) to the end of the shop vac to reduce the quantity of air and the
resultant small tornado inside the tank. Do not put a
rag around the vacuum hose to seal off the tank opening---implosion is
just as lethal to your tank as explosion.
21.19 - How do I troubleshoot leaks?
The first and foremost trouble-shooting step is to check that your
testing equipment, hoses, and connections are not leaking! After trying
the plans methods, try spraying soapy water on the joins. Leaks will
make bubbles. Next try filling the tanks with water. If you still cannot
find the leaks, get your friendly neighborhood air conditioning repair
man to fill the tanks with freon or halogen, then use his sniff detector
to pin-point the leaks (no pun intended). When s/he finds the leaks for
you, mark the spots, attach an altimeter to the tank, pull 1500' of
vacuum on the tank, and dab on drops of pure epoxy on the spots
identified as leakers. You can actually see the epoxy get sucked into
the holes. Whatever you do, do not inflate the tanks
more than a few psi as recommended in the plans. A ruptured tank will
ruin your whole day. It is also a good idea to leak check your tanks
again after 40 hours, certainly by 100 hours, and
during annuals to see if anything has changed.
21.20 - What are the pros and cons of connecting tanks and sumps?
Folks loyal to separate fuel tanks proclaim advantages in isolating
one tank from the other in case of a lost fuel cap, tank rupture, or
contamination. Folks loyal to common fuel systems proclaim ease of fuel
management. Common sumps do introduce more fuel into the cockpit and can
complicate fuel plumbing. Of course, the separate fuel system is the
only approach recommended by the Designer. If you are partial to common
fuel systems, Vance Atkinson's common fuel sump plans are presented in
the January 1993 edition of the Central States Association newsletter.
(See http://www.ez.org/csa/csa_newsletter.php
or contact Terry Schubert <jschuber@juno.com>
for more information about the Central
States Association.)
21.21 - What are the issues with fueling, static electricity, and
grounding the airframe?
The issue is with build-up of static electricity on the strake skin
surfaces which subsequently discharges and ignites fuel vapors. Static
charge is generated at the filler neck by the movement of the fuel
through the nozzle into the tank, just like rubbing your shoes on a
carpet in low humidity. On a metal airplane this charge is dissipated by
the frame to the grounding clamp. Our plastic planes are non-conductive,
so the charge has nowhere to go. Fuel is non-conductive too, so dangling
a chain or wire into the fuel will not help. Best procedures seem to be
to wipe the strakes with a damp towel to dissipate static build-up,
touch the fueling nozzle to the fuel cap before removing the cap,
provide some method of grounding the fueling receptacle, and never
refuel from a plastic container. Sport Aviation addresses this subject
in the December 1998 issue, page 55. Reference NFPA 407, Standard for
Aircraft Fuel Servicing, for more detailed discussions.
21.22 - Should I seal the AN fittings?
The late, great Tony Bingelis, author of such notable homebuilder
bibles as "Firewall Forward" and "Engines", cautions against
using Teflon tape. Teflon tape has the chance of flaking off into small
pieces, which is not good for the fuel system. Wicks and others sell a
product call Fuelube for this purpose. The stuff is expensive and comes
in very large quantities. You might check with your local EAA chapter or
FBO to get the small quantity actually needed.
Topic - Hotwiring [as of: 10 oct 99]
[distiller: John Slade]
Comments and Tips
Left in the Archives
- [only material from chapters 19 and 20 were used]
HW.1 - Can / should I borrow someone else's templates?
Some builders have cut metal templates using great precision and
are prepared to lend them out for the cost of shipping. Ask in the mail
list. Beware when borrowing other people's templates. Before using them,
compare them to the plans looking for shrinkage and correct alignment of
level lines.
HW.2 - What material should I use to make the templates?
Formica or Aluminum. Aluminum is best but Formica is easier to
shape and smooth. Be sure to remove all irregularities along the
template edge. Even the smallest bump can hang the wire and give you a
nasty jiggle in the foam. Cut all the templates at once. It is boring
work, but in the long run it will minimize effort.
HW.3 - Can I photocopy the templates?
Yes. But be very careful to ensure that you get accurate copies.
Many copies will give you significant error over the width of a large
template. Use tick marks in the corners to verify overall dimensions
before using copies.
HW.4 - Why are my templates a different size to someone else's?
Paper shrinks and expands according to moisture content. Thus you
can cause distortion if you use the wrong adhesive such as a water-based
contact adhesive. Most people use 3M spray-on contact adhesive (#77).
HW.5 - How accurate do I need to be when cutting my templates?
Some builders ask whether to trim to the OUTSIDE or INSIDE of the
line. Others complain about the lines not meeting correctly when joining
parts of the template. The answer is to be as accurate as you can be.
Try to leave some of the line showing to confirm your accuracy. If the
lines do not match, average the error. Be sure the level lines are
straight. If you consider all the various lay-ups and filler that will
later be applied then the thickness of the line is negligible. Just be
consistent.
HW.6 - Should I make or use a set of oversize templates?
The consensus seems to be about 50 - 50. Many builders swear by
this method, especially for the winglets where the template sizes are so
different. They hot wire anywhere from 1/16" to 3/16" oversize, then
spline sand to contour using the plans-size templates to guide a long
sanding block. This gets rid of any wire burn caused when the wire has
to go fast at one end and slow at the other. Spline sanding alone is
difficult. Use two people and use the talking numbers on the templates
while sanding. Those preferring the plans method argue that the oversize
method is less accurate, especially when "sanding to the numbers". If
the part moves or bends while you are sanding you will have valleys. Nay
sayers also claim that the majority of planes are built using the plans
method, they all fly fine and perfect cores, even if attainable, are not
going to change flying characteristics.
HW.7 - Can I plot the airfoil shapes digitally and produce a
perfect set of templates.
You probably can, but provided your work is reasonably accurate
using the plans methods will not create an airplane which "corkscrews
through the air". The majority of airplanes built with care fly
straight. It depends on how much of a perfectionist you are and how much
you want to get finished. You may be able to find CAD drawings on the
unofficial Cozy web site.
HW.8 - Should I cut my cores myself, or buy precut cores?
There are pages of discussion on this issue in the archives, much
of which predated formal approval of many AeroCad
prefab parts by Co-Z Development. Some builders say that hot wiring is
easy and fun, others are concerned that the results by a first time
builder are often less than perfect. Consensus seems to be that expertly
prefabricated parts are well worth the cost and will save you a lot of
time. Options such as molded spars and pre-skinned parts are available
and are highly recommended by those who have used them.
HW.9 - How do I get perfect cores?
It is not possible, and you do not have to. Just be as accurate as
you can and gently spline sand the wings before glassing. Small errors
will be hidden by the micro and glass added later. Most seem to manage
fine, but you CAN buy professionally precut cores from Featherlite or AeroCad
if you are really concerned about you are hot wiring abilities.
HW.10 - Does it matter how I pile the blocks?
Follow the plans. Be extra careful about the dimensions used to set
the planform angles. Try to keep any seams as far away from the edges as
possible and at right angles to the cut.
HW.11 - Should I sand the cores?
Yes. Gently sand the wing smooth before laying up the glass. This
will save significant time in finishing.
HW.12 - How much should I worry about the accuracy of my cores?
Do not stop "fussing" with them until they appear perfect. Most of
the bumps and dips can be avoided by not rushing this step. After all
the cores are assembled and out of the forms, sight down the span with a
flashlight (turn out the lights in the shop). You will see the shadows
(low spots) and you can gently sand the bare foam down with a 5 ft.
sanding block 4 inches wide to get near perfect contours before you
lay-up the glass. If the bare foam is straight and true so that the
entire part, when glassed, will be straight. The extra time on the front
end will save a lot of time during the finishing process.
Topic - Epoxy / Solvent Safety Issues [as of: 02 jan 09]
[distiller: Rob Nachtreib]
Comments and Tips
Left in the Archives
- [many discussions of gloves, respirators, allergy sensitivities]
CS.1 - Are epoxies and solvents dangerous?
In general, yes. Each material has a Material Safety Data Sheet
(MSDS) which rates the Health hazard, flamability hazard, and reactivity
hazard. Many MSDS have been collected at:
http://www.cozybuilders.org/ref_info/
Hazard ratings are summarized here, on a scale of 0-4, defined as
Severe (4), Serious (3), moderate (2), slight (1), minimal (0).
Hazard Hardner Resin MEK Denatured Alcohol
------------ ------- ----- --- -----------------
Health 3-4 1 2 1
Flamability 1-2 1 3 3
Reactivity 0 0 1 0
You should read the MSDS for your particular hardener, resin, and
solvent.
Maybe. Allergic reactions are unique to each individual. For a given
person, development of an allergic reaction seems to be a function of
cumulative exposure (critical dose). There's no way to predict the
critical dose to become sensitized But, once you sensitized, you are
forever.
Two people can have very different critical dose, up to and
including practically unlimited exposure (i.e. - bare skin touching
EZ-Poxy).
Your reaction to one allergen has little value in predicting your
reaction (if any) to another.
To be sure, limit your exposure to <particular>.
Severely limit your exposure to <particular>. That means gloves
and respiratory protection. If an alternative to <particular>
exists, you might try that, but you should probably limit your exposure
to the alternative, too.
It depends on what material you're working with. Check the MSDS.
The MSDS usually say something to the effect "wear gloves impervious
to this material." Some MSDS actually say what glove material is
impervious. The MSDS for MGS 335 Hardener says Butyl or Nitrile. The
MSDS for Aeropoxy Hardener says neoprene or "rubber". An MSDS for MEK
(there are several) says butyl gloves.
You might need multiple kinds of gloves.
Don't just buy any old gloves from the paint department at Home
Depot and think you'll be safe. MEK can dissolve some disposable vinyl
gloves.
It depends on what material you're working with, and the concentration.
Check the MSDS.
The MSDS usually say something to the effect, "use only with
adequate ventilation, avoid breathing of vapor or spray mist." Many
MSDS will give air concentration limits.
The MSDS for EZ-Poxy hardener says "if airborne concentrations of
MDA is less than or equal to 10 times the [personal exposure limit],
wear a half-mask respirator with a combination organic vapor/HEPA
cartridge."
An MSDS for MEK (there are several) says that "for occasional use,
where engineered air control is not feasible, use properly maintained
and properly fitted NIOSH approved respirator for organic solvent
vapors. A dust mask does not provide protection against vapors."
%% end of cozy-faq %%
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