Questions over the web, such as the following caused
me to put this site together:
Hello Mr. Reinsch,
the model of the Funtana you demonstrated in Porz, impressed us all, I
was especially impressed by the very quiet and superbly running ZG 20.
Can you supply me with a few details about this model, I take it, it is
from Sebastiano Silvestri. Unfortunately I was unable to obtain such a
kit here in Germany. I only found the electric version or the considerably
larger version calling for 100 cc engines. Which model have you used
and which version?
I am very interested (so are a few of my friends) I must add, as to which
components (servos power supply etc.,) you have used to create this fantastic
Does the ZG 20 run with the accessories you recommend (e.g. stainless
steel muffler) straight out of the box as yours does, or have you a „special“
that is not obtainable by the general public.
I would like to thank you in advance, I am very impatient to read your
With best regards.
I bought the Funtana S140 in October 2006. The S140 is designed primarily for piston engines
and electric motors. It really is too bad that it is no longer produced.
In the meantime Sebastiano Silvestri has the rather smaller Katana S120
The Titan ZG 20 in my Funtana is definitely
not a special, I simply took the nearest engine off the shelf and
put it straight into the model. The ZG 20 has not been tuned with
altering transfer ports timing, polishing or specially balanced reciprocating
parts. The only modification I have made to the engine has been to reduce
the weight, and for those who will, can easily duplicate what has been
done. I will explain a little further into this article.
Running in the engine in the model.
I use Aral Ultimate petrol with BelRay H1R. The engine was never run on
the test stand, instead, as I have long known, it is best to build it
into the model, with cowl in place and fly. It took about 5 hours to really
free up and one has the feeling always that it will sooner run at 12,000
I have reworked the Menz 18x6” propeller according to my „aerodynamic
feelings“, put another way, „tuned for 3D-flying“. Due to my past studies
in Aerodynamics I have far more knowledge in this sphere than in tuning
engines. The power pulling the FuntanaS140 through the maneuvers is engine
power multiplied by the propellers efficiency, with such a superb engine
as the ZG 20, it is the better method to increase the prop efficiency
rather than put the superb engine behavior at risk.
The trailing edge is really thinned, (like
an APC prop), above all the blades, especially at the tips, have been
scraped thin (with a Stanley knife blade). The leading edge has been carefully
sanded to give a real wing section. The prop is then painted with three
coats of clear dope and sanded in between. Now it is really smooth and
turns at 8,600-8,700 which is an increase of 400 rpm. Static thrust is
now 7 kp (15.4 lb), it has increased by 0.3 kp (0.66 lb),
that‘s 5%. Time taken including balancing all the way, a good hour. This
wood prop is 62 g (2.2 oz) and this is why the engine reacts
so extremely good to the throttle. Far better than the twice as heavy
APC propeller and rather better than the Super Silence 18x8” Pro which
I first used.
In the meantime, the NC-milled FIALA wooden propellers became available. Fortunately FIALA propellers come with the perfect thin airfoil section, a sharp trailing edge and a very smooth surface right out of the box. The FIALA 18x6" prop is exactly like my reworked Menz prop - at no extra cost in time or money.
FIALA Propeller 18x6"
Naturally with such a highly developed ARF model
as is the SebArt Funtana S140, success is not automatic, when one rushes
as fast as possible, to install without thinking, any ready to hand components.
All components in the kit box of the Silvestri
Funtana including the spinner, tank, U/C tail wheel and main wheels weighed
2,680 g (94.5 oz).
Ready to fly, my Funtana S140 is now
4,650 g (164 oz) with tank empty and 4850 g (171 oz or 10.7 lb)
with the tank full, enough for 25 minutes of 3D-aerobatics.
The radio gear consists of: 2x ACT DSL8-DSQ
receivers in diversity mode, one 1180 mAh LiPo battery, Power Box Smart
Switch, 3x 7,5 V ACT-Servos XT-07TG for ailerons and rudder all with 300
Ncm (417 oz-in) pull, as well as 2x XT-05BB for the elevators with both
having 60 Ncm (212 oz-in) pull.
The ignition battery is our 3000 mAh LiPo cell order no #2025 .
We have produced several custom made parts for
the Funtana S140 starting with the
The engine sits on a very light end grain
Beech wood motor mount. Beech is 3 times lighter than Aluminum. Being
end grain can withstand a lot of pressure. Beech is a lot better than
aluminum for this purpose, wood as apposed to metal damps vibration.
The engine mount is of course hollow, the Tufnol flange serves to distribute
the stress loading of the small crankcase mounting flange. I have glued
the Beech wood engine mount to the firewall, in turn epoxied the Tufnol
flange to the engine mount. This gives the required 32 mm extension and
a very rigid engine installation, with the minimum of weight being only
25 g (0.88 oz). The aluminum motor mount of the ZG 20 (weighing
28,5 g or 1.0 oz) is then not needed.
Beech end grain, Tufnol motor mount for ZG 20, 32 mm long
Item no #2093
No rubber mountings!
Anyone playing with the idea to install the ZG 20 on rubber mountings
would do well to read the following e-mail from a customer:
Re: Suggestions to supplement the engine instruction manual.
Hello Mr. Reinsch,
to your excellent engine manual for the ZG 20, I have a small supplement
for other modelers, to spare them a loss of faith in the engine. The
tickover was so bad on this engine I was about to give up, although the
engine certainly was not to blame. Up to a short time ago, try as I might
I could not get the tickover speed below 3,000 rpm. I began to lose faith
in myself with 35 years of modeling, and the engine. For the last 15
years I have always mounted my glow engines on rubber mountings, and
of course the ZG 20 with 15x8 mm / 55 Shore.
After reading the report
in the magazine "FMT" 09/07 recently about the ZG 20, the
penny dropped, I removed the rubber mountings and screwed the engine solidly
onto the firewall, then a wonder happened, the ZG 20 ran like it should
with 1,800 RPM at tickover. And my worries about the vibration, being
totally honest, they were less than with the rubber mountings. For other
users of the ZG 20, to avoid my negative experience, perhaps a small
supplementary note would save a lot of frustration.
With spar and rib breakage.
Most time taken up in building the Funtana was in developing a carbon fiber intake bend. It was only two thirds of the weight of the insulator block that is normally between the carburetor and the cylinder, but the carbon bend required time consuming and expensive making by hand.
Magnesium Intake Bend
Professionally manufactured in the lost wax process, the Magnesium intake bend is more robust and tolerates even the highest cylinder temperatures without warping. Because of the use of a very light Magnesium alloy, the intake bend, complete with insulator and gaskets, weights just 38.5 g (1.36 oz).
very flat bend, the length from middle of the engine to outside edge of
the carburettor is only 69 mm.
The Magnesium Intake Bend is supplied complete with insulator and three gaskets.
Magnesium Intake Bend for ZG 20
Using the intake bend requires the fuel fitting to be turned, otherwise
it will come against the crankcase.
To turn this fitting is not a simple operation, it is likely to be damaged
if not broken, air will then enter the fuel line directly at the carburettor.
In the photograph you can see the fine teething on the brass nipple, the
black nylon spout is injection molded over the brass nipple, any attempt
to turn the nylon spout will cause it to climb over the teething thereby
splitting it. When ordering the bend it is better to send the carburettor
with the order to us, we can turn the nipple free of charge with our special
Closing the hole in the choke flap
As the carburettor is in the fuselage and cannot be reached, I have soldered
over the hole in the choke disc. Alternatively you can use a drop of Araldite
This choke hole is a good intention on the part
of Walbro, but with a dry carburettor it takes a lot of hand energy to
get the fuel sucked into the engine. With this hole closed the start up
is so much easier. When the engine has run during the day, a single turn
on the prop is sufficient.
Light weight tuned pipe carrier made from 2
mm aircraft plywood
To enable the carrier to have a universal application,
it is machined out of a lager sheet, to reduce the size is not a difficult
CNC Tuned pipe carrier with silicon rings to
take 40 mm pipes
Item no. #2591
The green and red screws on the engine are aluminum. Aluminum
screws for the cylinder, crankcase and sensor weigh only a third of
steel screws, saving 32 g (1.13 oz) in engine weight.
But take care, use light control surfaces hook-up
and servos at the rear, and only then, when the CG position allows, use
the aluminum screws!
I have made the control surfaces pushrods
for the elevators and ailerons from 3 mm carbon fiber rod, have bored
out the bodies from our ball joints #0350 to 3 mm and drilled an extra
1,5 mm hole at right angles. They are glued together with Araldite 2011,
the rod ends are sanded to provide a key as well as the crosswise holes.
The carbon fiber rods weigh about a fifth of the steel screwed rods but
are twice as stiff.
Light but stiff rudder horns
Supplied with the kit were the standard model aircraft
control horns that are screwed to the control surfaces. Such rickety model
aircraft methods have never ever appealed to me, so I have made a „perfecter“
set of horns, milled from Tufnol. The CNC program is in our computer,
so if anyone wishes to have such a set for the Funtana or similar, he
can order these:
Tufnol Rudder Horn Set, 3 mm thick
Item no. #5282
Funtana technical data according to the manufacturer:
Wingspan: 1990 mm (78.3 in)
Length: 1990 mm (78.3 in)
Wing area: 80 sq.dm (1240 sq.in)
All up weight: 4.6 bis 4.9 kg (162.3 to 172.9 oz)
Wing loading: 57.5 to 61.1 g/sq.dm (18.85 to 20.1 oz/sq.ft)
Engine: 20-26 cc 2-stroke, 20-30 cc 4-stroke.
I achieved an all up weight of 4650 g
(164 oz or 10.25 lb) giving a wing loading of 58,1 g/sq.dm (19 oz/sq.ft).
A very low value for such a large aerobatic model.
Apart from the tip of the spark plug cap, the ZG
20 fits completely under the cowl. I have slightly widened the cooling
air intake openings downwards. The choke wire is accessible through the
Cables all shortened to a minimum
The battery and sensor cable on the ignition have been reduced to a minimum
and soldered directly onto the switch to reduce weight.
Engine mounting, extremely light, rigid and
The Titan ZG 20 is fixed to the firewall with M4x50 mm socket head
screws, fed through from behind the firewall and into the crankcase. You
can see the carburettor nipple has to be turned otherwise it will be against
The throttle pushrod is made up from a 1 mm
thick CF rod and ball joints from the small electric helicopter „T-Rex“
glued with Araldite 2011. The complete throttle
linkage weighs 1.2 g (0.04 oz). This featherweight pushrod not only saves
weight but considerably reduces the loading on the butterfly valve shaft
due to low weight is reducing oscillations. The throttle servo is an HS
85MG. A small 5,5 V power regulator is soldered directly into the cable
to adapt the servo to the 7.4 V power supply.
The very light choke pushrod is made from Aluminum
wire (our Ali solder #0920).
Shortening the HT cable
I have shortened the CF HT cable by about half, this is relatively
easy to carry out as the cable is simply screwed onto a threaded stub.
You only have to carefully cut away the heat shrink tube, push the two
retaining rings and the screening flex towards the plug cap, then unscrew
the cable. The refitting is obvious. Please do not attempt to remove the
spark plug cap from the cable or in anyway alter the cap. To do so will
mean a new plug cap, to fit a plug cap is exceedingly difficult. This
means sending us your ignition unit!
A very important tip in laying the HT cable:
As you can see in the photo the HT cable is formed
into a 90 degree bend, this layout vibrates and flutters so much due vibration
and cooling air flowing into the cowl that the carbon fiber in the cable
is pulverized after about 15 hours flying time. This then leads to ever
increasing stuttering. As I did not at first recognize the cause, I naturally
tried a freshly charged battery and a new spark plug, that cured the problem
for just a few minutes.
The new HT cable you will see is fixed to the motor
dome with adhesive band and the problem is solved forever.
In the photo‘ you can see there is little room for the rear fixing screw.
The hexagon head screw is screwed into the engine, the rear flange hole
is filed into a slot and slid under the screw head.
The self made header is assembled from two bent tubes, because I did not
get the shape right first time. It is only available in separate pieces:
bent tubes #3872, #6688, flange #2570 and silver solder #0981.
Intake noise silencer integrated in the engine
I have removed the covering film from the engine dome, stiffened the dome
cutouts with Balsa and then doped and tissued the dome. Built in the engine
dome is a intake silencer box made of 5 mm Balsa. It has a hole cut in
the back which can be seen here. The 3000 mAh LiPo ignition battery is
mounted in the dome with “Tesa Klettband” (Velcro). The 7.4 V,
1,180 mAh LiPo for the receivers and servos are kletted to the left side,
to counterbalance the engines cylinder. Unfortunately on my model
the right hand wing was rather heavier than the left, it went hard against
the grain to insert 22 g (0.78 oz) lead in the left wing tip. As
a small compensation, the model balanced out on the rearmost balance point
given in the instructions (195 mm) for “3D expert pilots only“ without
Lightweight tank ventilation-a fiddly job
I have used Festo 3 mm PP tube and Festo M3 screw on nipples for the tank
filler and air inlet thus saving 20 g (0.7 oz). These items can be bought
from any Festo dealer. The 250 cc tank is from our stock, this is enough
for 25 minutes 3D-flying. The rather unusual layout for the two airlines
on the tank ensure that the fuel is not lost in aerobatics including knife
edge flying. The Festo Nipples are not so easy to install as the nuts must
go inside the tank, these must be fixed with Loctite.
Lightweight power supply
The higher voltage power supply from two LiPo cells without a voltage
regulator allows the use of light 0,14 sq.mm section cables running to
the 7,5 V elevator servos without a noticeable drop in servo torque. The
super strong rudder servo having more than 30 kilos/cm (417 oz/in)
positioning torque, weigh a mere 67 g (2.36 oz) and because of the
higher voltage, draws less current than weaker servos do. It is the rudder
pressure alone which determines the torque required. A stronger servo
is not so highly loaded and can therefore react a lot quicker, and not
only on the ground (catalogue positioning speeds are always measured without
load) but in the air and at any airspeed..
The stainless steel tuned pipe increases static
thrust by 1 kp (2.2 lb) with only 178 g (6.3 oz) more weight
including the header, PTFE tube and spring clips.
We supply this tuned
pipe under the Item no. #2593
The tuned pipe collar is milled from 2 mm aircraft
quality plywood and weighs only 5,5 g (0.2 oz) including the silicone
I have shortened the long tuned pipe tunnel somewhat,
formed an aerodynamically improved outlet, saves a further 15 g (0.5 oz)
and looks a lot neater.
Do not fit superfluous parts
The closed loop rudder control wire has no quick links or ball joints,
screwed clevises or turnbuckles, it is directly threaded through the Tufnol
rudder horns. This is not only the lightest method, it is certainly the
most reliable and long lasting. Due to the extreme friction resistant
Tufnol there is no wear on the small loops of wire. There are no foreign
bodies (with respective mass) hanging on the wire that would cause the
wire to oscillate a lot more. I bend the wire with pointed pliers the
same thickness as the rudder horns, two times 90 degrees the bent wire
is threaded through the horns, it then stays relatively taught and remains
so for the life of the model without any need for readjustment. The correct
tension can be better achieved by first fitting the wire onto the servo
output arm, use a fine pointed felt tip pen to mark the length onto the
wire when pulled taught over the rudder horn. Slip the sleeve onto the
wire, then bend the wire 2 or 3 mm shorter with the pointed pliers, then
pull the wire up to the first bend, slide the sleeve into place and squeeze
flat with pliers, do not forget to do 3 or 4 crimps with a small pair
of pincher's as these have the cutting edges parallel as apposed to side
cutters and pliers.
Evaluate your club's landing strip realistically
To prevent irritating repairs to the U/C, I have reinforced the area over
the landing gear with CF. In the kit is a GRP UC. Our laminator made up
a "quick" mold from this UC and then a CF UC. Now you know
why the UC in the photo's is so black.
I have had to make several repairs to the wheel
spats, using CF, due to the very poor condition of our flying field. A
more reasonable type of fixing on both ends of the axles would have prevented
this damage, but now it is too late. The original 4620 g (163 oz)
all up weight has now grown to 4650 g (164 oz) after the first
few landings. It is a pity for without the lead in the wing tip, and the
spats repairs I would have just scraped under the minimum weight level
given on the box.
Maybe I‘ll be more successful with the next model...