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This page includes a list of the support
FAQ's (Frequently Asked Questions) for each of the Murphy products.
Some are quite limited in scope, but by sending questions that you feel
may apply, you can help to build this resource. To submit a question,
send e-mail to murtech@murphyair.com
Q. Installing leading edge skins on the
wings.
A. The leading edge skins are first cleco'd in the top hole on the
leading edge rib with the skin hanging down over the table. You pull
the skin down and drill the next hole and cleco. You continue doing
this until one side is finished. You then remove all the clecos and
turn the wing over and repeat the process on the opposite side. Once
finished you can remove the clecos and starting at the top of the rib
work your way down to the bottom clecoing as you go.
Q. How to deal with proseal?
A. We have found that if you keep your work area clean and uncluttered
while working with Proseal eliminates 90% of the common complaints.
Small throw away brushes with the bristles cut back to 3/8" work well
for applying the sealant. One brush will do about 40" of rivet line
before it becomes unusable. Clean excess sealant from visible surfaces
before it sets.
Q. Where should I install my air speed
indicator static source
A. A perfect spot to get the ambient pressure for the ASI has proved to
be the forward cabin side skin (just ahead of the door) on both sides
of the aircraft.
Q. What are some common bolt torque
values?
A. Quite a few of our builders have been over tightening their bolts.
The common bolts are AN3, AN4, AN5 and AN6. The following are torque
values in INCH POUNDS using standard fiber nuts. AN3 20-25 AN4 50-70
AN5 100-140 AN6 160-190
Q. How should I deal with areas of the
skins were the called out rivet seems to be to short?
A. In our aircraft kits we try to call out the rivet lengths in all the
areas of the aircraft. Sometimes, due to varying thickness of material
and use of chromate or proseal the rivet length used in the adjacent
area may be too short. This is common in the wing area where there are
many thickness of material in the spar. If you feel that a certain
rivet is too short to be pulled go to the next size rivet.
Q. What is the best way to run the trim
tab electrical cables through the elevator.
A. The best way is to run the wires straight up from the trim tab,
through a 3/8" hole drilled in the web of the elevator spar and back
along the leading edge side of the spar to the center of the elevator
and exit out at the center. Also, leave a fair amount of excess cable
where the cable exits the elevator or use a quick connect in order to
facilitate easier removal and installation of the elevator.
Q. When the floats are installed, the
maximum gross weight of the aircraft increases by 5 %, is this correct?
A. Yes, we have made provisions in our design to accept the increase in
gross weight. One should note that with floats installed, a natural
decrease in performance of the overall airframe/engine combination
should be expected.
Q. Where is the best location for the
brake reservoir?
A. At the top of the firewall, engine side of the firewall.
Q. Where is the best location to ground
the battery to?
A. The best location would be to ground the battery to the nearest
bulkhead.
Q. Can I add lubrication to the delrin
bearing?
A. No, the Delrin is a self lubricating type material. Any lubrication
such as WD-40 can dry out the delrin.
Q. I am fighting cooling problems with
the engine, what can be done?
A. Increase the cowl exit area. A typical rule of thumb is exit are is
1.5 times the inlet area. If cooling still is difficult sometimes the
addition of a lip (flange) about 1 1/2" down on the back of the lower
side of the cowling can help create a low pressure area which will
improve the scavenging of the hot air out of the cowling. This will
draw more air through the engine compartment. Also, the baffle should
be place tight against the rear cylinder, this will force the air to
travel through the cylinders. Also, you may wish to check the size of
your oil fittings on your cooler. Some of the earlier kits were fitted
with 3/8" fittings and adapters, these could be increased in size to
1/2".
Q. Can an amateur cover the aircraft?
A. Many builders tend to worry when it comes to covering with fabric.
This is an extremely simple process. If you follow the instructions
carefully you will end up with a professionally looking covering job.
The modern materials available today are designed for ease of use and
long life. The most important part of covering is for the builder to
have patience, the work, although not complicated, is repetitive.
What about fabric covering for the wing?
A. There is no section in the manual in regard to fabric covering of
the wing. The fabric covering method is described in the aileron
section. With the wing, Poly-Fiber recommends that the owner use 1 1/2
inch rivet spacing for fabric rivets, if the 3M weather-strip tape
(polybond) is not being used. If an owner is using the 3M tape, then a
3 in spacing or less could be used. Also, acid etch prime the metal
surface for better adhesion of the polytack.
From Murphy Aircraft Manufacturing, Ltd.
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