RCRCM Strega Build
The plan is to put in details here with the building / assembly of the RCRCM Strega just received.
Joiner = 108 gram
Right wing = 585 grams
Left wing = 589 grams
Left V-tail = 47 grams
Right V-tail = 49 grams
Fuselage = 227 grams
Modified Ballast tube = 41 grams
Modified Servo tray = 25 grams
Total weight of not assembled glider = 1671 grams
This is pretty light after my standards, and yes, this a glass, carbon re-inforced model.
The hope is that this model should come out at 2,1Kg, not more than 2,2Kg.
I see at other Strega threads that Cg is around 113mm, but I understand these are folks
that like an aft Cg. I am pointing out to land the ballast tube at 110mm to be safe, and that I do
not like the behaviour of too aft CG on models. In my head, I envision that the "new, dynamic"
flying style in F3F, do not especially suit well with a too aft CG. But I am more than happy to receive feedback
concerning CG for the Strega.
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First a custom made ballast tube was prepared, see thread "Ballast tube 101".
The 17mm diameter and 36 cm long supplied ballast tube would only permit approx. 900 grams of lead ballast.
The one made have 22mm inside diameter and an efficient ballast chamber of 48,5 centimeters.
22mm dia. slugs 6,05cm long, does give 250 grams for each slug, lead moulded inside this dimensions brass
tubes, giving a total of 2 kilograms of ballast with 8 slugs, that should be more than sufficient for this model.
To allow this ballast tube, a custom made servo-tray had to be prepared, firstly to allow side by side servo-
mount, and also that the servo tray needs to be used to secure the ballast. A cover over the back end, secures
the ballast, 4mm machine screw in front, and two 3mm ply-wood plates in the back end of the slug opening.
A opening in the front of the servo-tray allow the 2/3A 4,8V battery package to slip in, as well as the Futaba R617FS receiver
to fit in the battery opening with the servo-cable connectors being put inside under the servo tray.
The long servo-tray glued into the ballast tube, as shown in the connetion surface in servo-tray picture 8, as well as the whole ballast tube
will be glued with epoxy, mixed with micro (0,2mm) glassfiber cuts in the floor of the fuselage, should add strength to the fuse.
Pictures show the detail what have been tried explained in words......
To be continued......
Very cool paint job ! Subscribed
The vipers had to be worked on for two reasons:
To allow desired up aileron travel to 17mm, to prevent binding in flaps
especially when returning control surface to neutral.
What I used, 80 grit sandpaper, finish with 240 grit paper, placed on an old
credit card, plastic card, to allow sanding straight lines, both in viper and end
of the wing skin separating control surface and wingskin (cutout).
You definitely don't want vipers in your plane....
Snakes in a Plane :eek:?!
Flap servos mounting
The servos for flaps were glued in today with 6min epoxy, to get things moving.
I used servo frames suitable for Futaba S3150 which is a reliable servo I have good experience with.
Food plastic was put between the servo and frame before glued in, and removed after. Now a broken gear in the servo is no problem later.
I used 3mm threaded steel for linkage, and 3mm dubro link, these are being zapped, I know some solder it, but zap works for me.
Servos were glued in based on both linkages 5,8mm long, and got the right angle in the servos. I was happy with the flap deflection that came out of this.
I assume / hope 80+ degrees.
Aileron servos mouting
Wings all done, just missing servo covers.Both wings weighed, they came out at 670 grams.
Same procedure as mouting the flap servos, food plastic between servo and servo frame.
The ailerons easily gives 15mm up deflection... :) I want all this travel, the servo should maybe
give max 12mm up in high rate, but I also want turn response when butterfly deployed, that means
to add some more to the 12mm......
Ballast tube mounting
The ballast tube was glued in today with RG moulding epoxy mixed with 0,2mm
glassfiber cut to achieve maximum strength.
First the ballast tube was used as a foundation sanding the bottom of the fuselage. To pce. of 80 grit paper was taped around the middle of the tube and in the end towards the tail. Rubbing some in the bottom of the fuse to make sure the epoxy have as good binding in the glue joint as possible.
Then after the bottom of the ballast tube was sanded with the same paper.
Epoxy was applied to the bottom of the ballast tube. Doing it this way, a tip is
to recon were the glue hits the canopy opening when putting ballast tube inside.
Leave 4-5cm of that area without glue, and slip the ballast tube inside, and apply glue on the missing spot thereafter.
A long piece of tape were applied around the slug opening, allowing to "fish up" the upside down ballast tube, to put it in it's place, turn it around, and press down to the fuselage at the correct choosen spot.
The spot which I choose were at a CG a tad in front of 112mm.
Then 7 slugs of ballast were put inside the tube, to make sure it is pressed down to the fuselage while the epoxy dry and harden. Next step in the evening, may be to install the servo tray and fuselage wiring...........
Servo tray mounting
A 66 gram piece of lead moulded in a modeler putty box from the children with aluminim foil where glued in the nose based on the mould by pushing the nose of plane with foil into the modeler putty. The servo tray was glued in with RG moulding epoxy. First after inserting the fuselage wiring harness, a thin layer of epoxy were applied with a brush inside the fuselage where at the edges of were the tray will meet the fuselage.
Then applied epoxy mixed with 0,2mm glassfiber cut where the tray has connection with the ballast tube.
And then brushed the edges of tray from top with epoxy. Another layer of glassfiber mixed epoxy will be applied to make sure all edges are glued to the fuselage. Given the lenght of the servotray, a grill spear/flower stick where used to apply epoxy at narrow sections inside the fuselage and in the front of the nose.
Then finally when epoxy beginning the hardening process, the epoxy where used to glue / secure the MPX connectors into the fuselage.
The weight of fuselage with V-tails, receiver, battery and uncut too long carbon pushrods is now 660grams, so estimated weight by now is 2110 grams for the whole assembly.
The Strega was completed today. Servo covers were fitted and linkage in fuselage for the V-tail were prepared.
Since I choose a side by side servo mount, I needed to do some solution for the
elevated servors. Two 3mm threaded steel rods were glued upon eachother, and then glued on top of the carbon rod linkage, and secured with carbon rowing.
The whole assembly, after needing to add 89 grams in nose to achieve CG at 110 mm, were a total of 2160 grams. A little more than I hoped for, but still within my specification when purchasing the plane.
A youtube video will come when flown.
After an intense installation / assembly period of the new Strega, I had the opportunity to fly it the day after the last hand was laid on the work.
The model felt comfortable from the first stick movement, and it is the first time I have really liked a model once it is in the air.
Maybe I was fortunate with the conditions, and that settings was perfect from the start, but I actually believe that this model has "something" for this price segment, compared to other more expensive models .
The only trimming that was needed was some up adjustment of the elevator, besides this, it flew straight.
I've never flown a 3-meter model that has so good handling and response, including both ailerons and elevator. Another thing I felt was that it held the line very well.
Only thing I can point out as "negative", was when using some rudder, it had a tendency to be unstable at that axis, "vagging its tail," but once coming accustomed to it, I'm sure this can be controlled.
I would like to credit James Hammond for a well designed F3F glider, and at least a good handling plane for fun, that is for sure.
And can't wait if there should turn up a new F3F ship with the latest airfoils like present on the new Schwing 88".
Time will show if I am able to fly faster F3F with this Strega, I do think it has the potential.
Initial Strega settings
The settings I flew the Strega first time, may be subject to some changes after more testing. But they seemed very OK, but may be adjusted:
Ailerons - 12mm up, 6mm down highrate, 10mm up, 5mm down in lowrate
Flaps with aileron - 6mm up, 3mm down in highrate, 4mm up, 2mm down lowrate.
Ailerons measured at tip, flaps measured at root.
Elevator - 10mm up, 7mm down highrate for landing, 8mm up, 5,5mm down normal flight
Butterfly settings for landing - ailerons 8mm up, flaps as much as possible, I have 72mm, elevator 6mm down at full butterfly, adjusted on a nearly linear curve. With this the plane comes down in a nice angle, an no whopping up or down when applying the butterfly.
Snapflap 7mm at root at flaps at maximum, ailerons flushed to align flaps.
The mix have been set to turn knob on the radio, so the throw of the snap flap can be adjusted in air, I settled down at appox. 5mm down at full elevator, mixed with a curve, where the snapflap sets in at 1/3 stick movement at the elevator, and then the snapflap comes in a rather steep curve, giving much from thereon.
Aileron to rudder mix was set to 0,5mm, also assigned to a turn knob on the radio, so it may be adjusted to my liking, just a tad movement of the rudder make the model making the turns much nicer, too much not so good.
Flight phases, speed, normal and thermal.
Speed - 0,5mm up at aileron at tip, 1,5mm up at root or aligned with the aileron
Thermal - 4mm down at flaps, aileron aligned with flap , 1,5mm down compensation for elevator.
Centre of gravity at 110mm, needed 89 grams of lead in nose.
I agree with your findings the Strega does hold a line very well indeed, while I had mine it was always a go-to model when the conditions were knarly.
I find with many models like this having small rudder throws is the way to go. Similar amounts to the elevator, and just allow it a little time to react rather than trying to do hard "power" style rudder manoeuvres.
I find that this makes for a much sweeter model.
Strega baptism of fire on the F3F slope
In the first F3F runs the Strega was driven to the limits.
In 14-18 m/s and with all 1950 grams of ballast the Strega was
capable of good times after my measure. Had my personal best
of 37.56 with it. In more capable hands this model is good for much more.
In these wind gusts, the Strega has it limit with so much wind and ballast.
The wings were bending disturbingly when stressed with negative G force
while trying to catch up missing signal in turns.
The bending were not so disturbingly in a normal turn.
Let it be said that the Strega were never designed to be flown at 18m/s
with 2kgs of ballast.
This is a fully capable F3F glider for average guys wanting to attend to the local contests, not having
ambitions to be world champions at Rugen......
A little footage of the fun day at Hodne with my PB ever set with the Strega:
I was "unfortunate" to have a little incident in some of the hard turbulent landings seen in the sequence, but just a minor repair required...
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