The Titan ZG 20 in a 2 Meter SebArt FuntanaS140

Video Zenoah G20EI in SebArt FuntanaS140
Before you read this dialogue, please take a look at the video of my Funtana with the ZG 20 and Christian Wagener on the transmitter.

I have intentionally chosen the SebArt Funtana S140 for the ZG 20, I am completely convinced that ambitious 3D aerobatics, - and above all, a load of fun is to be had - not only with expensive 3 meter models. It is in fact possible with much reduced expenditure. One must only get everything right. Top quality 3D aerobatics are not achieved solely with motor performance!

Decisive is, apart from the pilot, the very low all up weight, combined with the low wing loading, and the absolutely reliable engine, the thrust / weight ratio of 1.4:1 is exactly right. We are not out to make racing machines, in that we do not require the model to fly vertically out of sight in 3 seconds.

Zenoah G20EI installation in SebArt FuntanaS140

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 model.
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 answer.

With best regards.
C.E.

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 in production.

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 rpm ...

Propeller tuning
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"    See current price in the TC webshop

 

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
Motor mount:

Zenoah G20EI very light end grain Beech wood motor mount. Beech is 3 times lighter than Aluminium.

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             
See current price in the TC webshop

 

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.
A. S.

 

Carbon-Intake Bend

Carbon-Intake Bend for Zenoah G20EI


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).

Magnesium Ansaugbogen am Titan ZG 20 montiert

With the very flat bend, the length from middle of the engine to outside edge of the carburettor is only 69 mm.

Magnesium Intake Bend Zenoah G20EI - closeupThe Magnesium Intake Bend as supplied complete with insulator and three gaskets.The Magnesium Intake Bend is supplied complete with insulator and three gaskets.

Magnesium Intake Bend for ZG 20
Item #2095                    
See current price in the TC webshop


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.

Walbro Carb fuel fitting

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 tool.

 

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 2011.

Close the hole in the choke flap of the Zenoah G20EI for faster and better priming.
Detail view of the closed hole in the choke flap of the Zenoah G20EI Walbro Carb.

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

CNC milled tuned pipe carrier with silicon rings to take 40 mm pipes. 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 job.

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 job.

CNC milled tuned pipe carrier with silicon rings to take 40 mm pipes

CNC Tuned pipe carrier with silicon rings to take 40 mm pipes
Item no. #2591             
See current price in the TC webshop


Aluminum screws
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.

Aluminum screws for the cylinder, crankcase and sensor weigh only a third of the steel screws, saving 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!

 

CF-Pushrods
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.

Pushrods for elevators and ailerons made from 3 mm carbon fibre rod weigh about a fifth of the steel screwed rods but are twice as stiff

The carbon fiber rods weigh about a fifth of the steel screwed rods but are twice as stiff.

 

Light but stiff rudder horns

Set of horns, CNC milled from Tufnol for SebArt FuntanaS140 and similar models
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
           
See current price in the TC webshop

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 of the SebArt Funtana S140

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 intake opening. Zenoah G20 istallation of ignition and ignition switch in the SebArt FuntanaS140

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.
Zenoah G20 Engine mount, extremely light, rigid and neat

Engine mounting, extremely light, rigid and neat
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 crankcase.
Zenoah G20 0.04 oz throttle linkage made up from a 1 mm thick CF rod and ball joints from the small electric helicopter „T-Rex“ glued with Araldite 2011

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. Zenoah G20 very light choke pushrod made from Toni Clark Aluminum solder rod #0920

The very light choke pushrod is made from Aluminum wire (our Ali solder #0920). Shortening the HT cable on Zenoah G20 to reduce weight and bulk

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. Zenoah G20 HT cable fixed to the motor dome with adhesive band to prevent vibration induced fatigue failure.

The new HT cable you will see is fixed to the motor dome with adhesive band and the problem is solved forever.

Header
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.
Zenoah G20 self made header assembled from two bent tubes #3872 and flange #2570 with silver solder #0981

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. Zenoah G20EI intake noise silencer made of 5 mm Balsa integrated in the engine dome of the SebArt Funtana S140

Intake noise silencer integrated in the engine dome
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 any lead.
Zenoah G20EI lightweight tank ventilation in SebArt Funtana S140

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.
Rudder servo installation in SebArt Funtana S140

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 #2593 increasees static thrust on the Zenoah G20EI by 2.2 lb with only 6.3 oz more weight including the header, PTFE tube and spring clips.

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  See current price in the TC webshop
Zenoah G20EI tuned pipe collar milled from 2 mm aircraft quality plywood, weighs only 0.2 oz including the silicone buffer tubes.

The tuned pipe collar is milled from 2 mm aircraft quality plywood and weighs only 5,5 g (0.2 oz) including the silicone buffer tubes. Shortened tuned pipe tunnel with aerodynamically improved outlet in SebArt FuntanaS140 powered by a Zenoah G20EI

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.

The closed loop rudder control wire on the SebArt FuntanaS140 is directly threaded through the Tufnol rudder horns, it has no quick links or ball joints, screwed clevises or turnbuckles. This is the lightest and the most reliable and long lasting method.

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.
To prevent irritating repairs to the U/C, I have reinforced the area over the landing gear of the SebArt FuntanaS140 with Carbon fiber and epoxy.

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...

Gerhard Reinsch


Installation in Katana UL
Installation in Showtime 4D
ZG 20 Description
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