RCRCM Strega User manual

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Paul
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RCRCM Strega
Manual
by Paul Vesely

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Contents of the Strega Manual
Introduction......................................................................................................................................................... 2
Materials needed................................................................................................................................................. 3
Strega-Kit......................................................................................................................................................... 3
Additional materials required......................................................................................................................... 3
A few added and some replaced parts............................................................................................................4
Preparations and assembly of parts:................................................................................................................... 4
Sanding the sealing lips................................................................................................................................... 4
Installation of control horns in the wings....................................................................................................... 5
Installation of the wing servos........................................................................................................................ 7
(Making and) mounting the servo board...................................................................................................... 16
V-Tail linkage................................................................................................................................................. 18
Ballast tube....................................................................................................................................................19
Setup of the plane.............................................................................................................................................. 21
Flying Strega...................................................................................................................................................... 23
Introduction
The RC glider Strega from RCRCM is a full on F3F/F3B sports model. It is ideal for the ambitioned RC
amateur pilot who wants a high end all-round glider that features excellent thermal flying- but also
speed flying- capabilities. In addition, the Strega cuts through hard transitions smoothly and will also
promptly follow your commands through basic aerobatic maneuvers.
I prepared this assembly guide for the medium experienced craftsman. Therefore, I have
described all assembly steps that I deem critical for proper function of the plane. Knowledge of
standard techniques such as use of epoxy resin, soldering cables and plugs, as well as
preparation/choice of batteries and RC equipment, is required. In a few cases I used materials that
are not supplied with the kit. There, more detailed explanations- as well as the reasons for the
changes- are given. I actually really enjoyed the building process of the Strega and, I wish you a lot of
fun building it yourself! At the end of this guide there will also be a section on the RC-setup of the
plane and on flying it.

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Materials needed
Strega-Kit
You can order the kit via https://www.rcrcm.com. Once the kit arrives you should have a good work
bench covered with cloth (for plane surface protection) at hand. First lay out all parts. Here is what
you should find, see figure 1.
Figure 1. List of Strega kit parts: (a)Wings; (b)accessories [see insert on the upper left; 16 clevises, 8
threaded rods, 4 control horns]; (c)wing servo mounts; (d)wing servo-bay covers; (e)ballast tube; (f)fuselage
servo tray; (g)carbon push-rods; (h)tail piece; (i)fuselage; (j)V-tail joiners; (k)two piece V-tail; (l)wing joiner;
(m)canopy.
Additional materials required
Servos: I used two DS215MG V3 in the fuselage and four DS225MG as wing servos.
Receiver: I used a R6208SB from Futaba, but many different ones will do just fine.
Battery: You can use many types of NiMH or lithium technology based batteries, which are readily
available in several RC shops. There is no need to go for high discharge C. Just make sure the voltage
fits your RC system and you have at least 2Ah capacity, offering a good amount of flying time. My
personal choice were two Samsung ICR18650 LiIo cells, 2850 mAh capacity, 2C discharge capability
connected in series and with self soldered balancer and connector cable system. LiIo cells are
probably one of the cheapest & best systems in terms of space requirements, weight, performance
and price.
a
m
i
h
f
k
e
l
j
c
d
g
b
b

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Ballast: It is best to order the Strega ballast set together with the kit via https://www.rcrcm.com. For
the fixed mounted nose ballast I suggest to use lead shots, widely available in RC stores. Get at least
150g.
Wiring Harness: Probably available at RCRCM in future. Even so, mine is self soldered. To do this, get
about 4m three pole 0,34 qmm servo cable, 2 green multiplex plugs for wing connection and about
10 connector plugs for the RC system of your choice.
Miscellaneous: You will need a good toolset, soldering equipment, UHU Endfest epoxy (which will
harden to “bullet proof quality” over night), 5 min Epoxy, super glue (cyan acrylate based, extra fast
hardening glue), shrinking tubes of various sizes, e.t.c. e.t.c…. in other words a normally equipped RC
assembly work area.
A few added and some replaced parts
You can assemble Strega nicely using only materials mentioned above here. For personal preference
and for best performance however, I added a few things and I choose to replace some original parts.
Ballast tube mount: I desigend a rib for the fuselage and cut it from plywood, see figure 18.
Clevises (Fork heads): The original clevises were substituted by conventional ones (widely available
in RC stores) for better performance and zero tolerance assembly.
Carbon rods: The ones seen in figure 17 (upper left), were used instead of the supplied metal
threaded rods. Again carbon rods are widely available in most RC shops, probably stiffer but sure
lighter and better for tolerance free fork head mounting, than the original metal rods.
Servo tray: To gain a little space in the fuselage I cut a newly designed servo tray for parallel servo
mounting from 3mm plywood and reinforced it on top and bottom with one layer glass fiber
laminate, see figure 16.
Preparations and assembly of parts:
Before you start, spread a fleece blanket over your work bench and apply masking tape onto the
critical parts of your plane, to protect the delicate high gloss surface.
Sanding the sealing lips
The sealing lips of all control surfaces need to be bevelled to ensure that they won’t “catch wing”.
This is most important for the flaperons(flaps) due to their great deflection level during use as
airbrakes. See figure 2.

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Figure 2. Taper the control surface sealing lips: First cover your working table with a soft cloth, such as a
fleece blanket to protect the wing surfaces. Next, apply masking tape onto the respective wing and control
surface (left panel). Now, use a sanding block to bevel the sealing lips carefully. Be careful to keep the “angle
of attack” constant over the whole length of the sealing lip, as seen in the middle panel. This will help to
generate a pointed leading edge (see right panel, red box) that won’t catch the wing surface, even after
coming back in from maximum deflection.
Installation of control horns in the wings
This is an especially important task because it will critically determine the function of the control
surfaces. Here, I describe the use of a “classic” cross-wise linkage system for ailerons (ails) and flaps.
Therefore, drill holes through the wing back shear web, the flap- and ail- shear webs. See figure 3.
Figure 3. Drill holes for control horn installation: You can use a round file to file a whole into the wing back
shear web exactly below the pushrod exit hoods (left panel). Alternatively, you can also use a small electric
drill with a rotary bit (middle panel). In this case however, be careful not to break through the wingskin. If
you place one finger underneath it you will feel the vibrations once you get critically close to the surface.
The flap and ail shear webs have to be treated the same way. In the end they should all look like in the right
panel.
Before you can glue the control horns into the holes of the flap and ail shear webs, they have to be
properly prepared. First, using a drill, you will need to carefully adjust them so that the clevises will
perfectly fit in the respective holes. Next, impregnate them with UHU endfest. See figure 4.

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Figure 4. Prepare the control horns for flaps and ails. Measure the diameter of the little perpendicular rod
inside the clevises. Now choose a drill with a diameter slightly smaller than what you just measured and
carefully drill through the clevis-attachement hole of each control horn (upper left). Now the clevises can be
attached (upper right). Closing the clevises should not go easily, and once closed, it is totally fine if it is hard
to move each control horn within the respective clevis. This way tolerance will be at a minimum and the
movement capacity will be fine, eventually. Now you want to mix UHU endfest and distribute a medium
thick film of it on each of the control horns (lower panels). Be careful not to add resin onto the clevises.
However, if that happens you will still be able to break it later (before the resin is fully cured).
Subsequently glue the readily prepared control horns into the holes that were previously prepared
in the the flaps’ and the ails’ shear webs. The flaps will need 70-80˚ downward/and only a few mm
upward travel, whereas the ails will need over 10 mm upward and a little less than that downward
travel. Therefore, the positioning for flap and ail control horns is different. I have prepared a scheme
and one should exactly follow the scheme when fixing the horns with the slow curing extra strong
UHU endfest. See figure 5.

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Figure 5. Mount the control horns: it is best to fix the control surfaces in a 90˚ angle to the wing using
masking tape, first. Now have a look at the upper panel. This describes exactly how to fix the control horns
respective to the hinge of each control surface. Note the different positioning for flaps and ails. To glue the
horns in you can use the same epoxy resin that was prepared for impregnating them. Just add some cotton
flakes or microballoons for higher viscosity. Let the thickened resin drop into the holes (that you prepared)
in the flaps’ and ails’ shear webs (lower left panel). Subsequently insert the control horns exactly as
described (in the upper panel) using a caliper for measuring their positions. Essentially you can stick the
control horn into the embedded epoxy, adjust it and fix it with tape (lower right panel). However, and this is
very important, come back about 2-4 hours later, when the epoxy is sticky but not hard, and re-adjust the
position to a perfect fit. The slow curing type of epoxy will allow for enough time (several hours) for
adjustment. Eventually, after over night curing you can remove the positioning tape and the clevises.
Installation of the wing servos
The cross-wise linkage system demands that the servo control horns are as short as possible.
Therefore, extra holes have to be drilled in the horns and the clevises need to be tuned. Figure 6 will
guide you through the preparation of servo horns and clevises for the wing servos.

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Figure 6. Prepare the servo horns and clevises for the wing servos. First drill a hole through the servo horns
(for choice of drill see figure 4) 2,5mm outside the servo horn base (upper panels). The clevises will need to
be milled on the bottom side to allow for full movement respective to the servo horn shaft (middle panel
and lower left panel). Once that is done the clevis allows for full movement when mounted on the servo
horn (lower right).
Once the servo horns and clevises are readily prepared the servo frames need to be adjusted for
perfic fit and test fitted in the servo bays. See, figure 7.

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Figure 7. Prepare the servo frames: Mill down the servo horn side of each of the four servo frames (left
panel) to allow for full movement of the servo horns (middle). Check if full range of motion is allowed for
(middle). Test fit the servos in the servo bays (right). The front edge of the servo should be aligned with the
front edge of the servo bay. Fiddle in the pushrods through the holes in the shear webs and connect them to
the servo control horns in upright position. The servo should now be straight aligned and the pushrods need
to move freely while pointing exactly towards the wing control horns. If that is given mark the servo position
(right).
Next, you want to fix the wing servo frames in the marked positions using slow curing UHU endfest
epoxy. It is best to do this with the servos attached to the frames to find the exact positions.
Importantly, you will need to protect the servos from the epoxy to ensure that they are not getting
stuck for good in the wings. See figure 8.

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Figure 8. Fix the servo frames in the wings: First, wrap each servo with saran wrap (upper left). Next, briefly
sand servo bays and bottom of servo frames and push each (saran wrapped) servo into its respective servo
frame (upper right). Now mix the endfest epoxy, add some cotton flakes (or microballoons) for
thixotrophing it and smear it into the fine sanded servo bays and onto the bottom of the servo frames. Bring
the frames with the servos into the marked position in the wings (lower left). A nice trick for tight
attachment of the frames is to put water filled plastic bags on top of them (lower right). This ensures even
weight distribution and is simple. Putting metal weights on top of servos however, is good too.
As soon as the servo frames are fixed in the respective wing servo bays you can mount the linkage
systems for flaps and ails. Be aware that the flaps will need about 80˚ negative throw and only a little
positive throw; while the ails need roughly the same positve- and negative- deflections. Figure 9 will
describe how to achieve these settings.