AMPHIBIOUS W*R*A*M

Last year you saw just what John Doherty was capable of building when he was featured in the September issue of the"From the Workshop" series with the 4 engined Maia and the piggyback 4 engined Mercury.
John has let it be known that the Maia is yet to have its maiden flight. To begin with, it needs two very qualified pilots, and John says he isn’t one of them, not yet anyway. Meanwhile he has  been distracted by an ARF Tiger Moth and others, to give relief from the big project.
But this modeller is no shrinking violet when it comes to building first scale models! The pic on the right shows John’s very first scale effort back in the early 90’s.  It is a 79 and a bit inches Catalina, (that’s 2 metres to you young’uns).
John chose the Australian Black Cat squadron markings. The original of John’s number, was notorious for dropping a load of mines in the bay at Broome on take off during World War II.
The power for the model was provided by two OS Wankels, each about 0.30 cu inch.  As you can see, it was fitted with retractable gear. But John said the plane was just too heavy, as expecting the worst, he lathered on the resin and glass inside and out.  So for the first flight at Lake Glenbawn, near Scone, the u/c was removed and the weight came down to 10lbs.

The plane flew beautifully. John followed this project with a 104 inch, (2.6 metres) Catalina which unfortunately he put into the dirt, instead of the water! But the original Black Cat is still in one piece and hanging in the garage.

John’s wife Dorothy is also a member of the Club and is seen here with John and his 96 inch Short Sarafand hanging from the ceiling. A video of the first flights was very impressive.
I got to thinking that there must be something about two family members and first scale projects. The other Club husband and wife team, Dennis and Steffi Grech, chose for their first scale project a twin engined ME 262, which also still survives and in fact flew last on 31 January. 
So perhaps the go is to join up the missus before you get into multi’s! I guess pigs will fly before Jill Furzer joins Grant! But let’s meet the Doherty’s again. 
The next photo is of John and Dorothy seen standing behind the Tiger Moth in that very large model room that used to be the family room of their Gordon home. (One advantage of the kids leaving home!)
John started his working life as an apprentice boilermaker and after 2½ years went into the Drawing Office at Vickers Cockatoo then onto Morts Dock. His first taste of modelling was in about 1943/45 at the age of 16/17, making 1/72 scale models for the Volunteer Air Observers Corps. These were carved from hardwood when balsa was unattainable during the War.
Serious modelling did not emerge until retirement around 1988. John had proceeded to become a Professional Naval Architect (Sydney Technical College). Moving from the Drawing office, he  went into the Consulting business with a Dutch friend. The firm was Eken & Doherty. Later upon the retiring of his friend, Eken, this became MJ Doherty & Co. 
This consultancy went for 33 years starting off after the War with conversion work such as coal to oil fired boats and motorising steam tugs Later original work took in such boat types as as Island traders etc. 
John’s amphibious bent is quite apparent.  The 96inch Short Sarafand, shown hanging from the roof, flew impressively, as demonstrated in the 1999 video I viewed.   The model was scratch built from 3 view drawings in a book of the full size 6 engined aircraft. 
John has 3 OS Wankels as tractors with dummy push engines. At its first event in 1999 the aircraft took out the Pilot’s award Bob Parker Memorial Trophy at Albury/Wodonga.  This project took John 3 years.
Thanks John & Dorothy for a look at one branch of our hobby that few are exposed to.  It’s a shame we don’t have a lake close by that is legal for the ROW aficionados.

TOO MUCH TOO LATE!
A basic problem of most students might be described as  too much too late .  That is, not realising quickly enough what the machine is doing, and then overcorrecting on the controls.  Furthermore, it is as important to know when to take out a control deflection as when to put it in. For those brave souls who aspire to the model helicopter, this soon becomes even more painfully obvious than in the case of a fixed wing model.
Note that it was emphasised earlier that with ailerons especially, the aircraft continues to roll as long as the ailerons are deflected.  So in maintaining the wings level for straight flight, the ailerons must be allowed to centralise as soon as the wings are level.  Likewise, when you roll out of a turn to the wings level position.
When you roll into a turn, failure to reduce aileron deflection when the wings are at the desired angle of bank will allow the bank to increase and the nose to drop as described earlier.  This is the start of a  spiral dive , and it is important to understand that pulling the stick back under these conditions will only  tighten the turn , not make the aircraft climb.  Hence the injunction to get the wings level first.
The spiral dive should not be confused with the spin.  A spin occurs when one wing stalls before the other.  The aircraft begins to rotate about an axis somewhere between all the normal axes, with the wing on the outside of the spin continuing to lift, while the inner wing remains stalled. In this condition ailerons are ineffective in raising the low wing, and to stop the spin it is necessary to apply opposite rudder to reverse the inside/outside effect and stop the spin.
Since most trainers have to be forced to spin in the first place, and some may not even be capable of spinning, this is not usually of much concern to the student in the early stages, but try to find someone to show you what a spin looks like. Most models recover from a spin by themselves if the controls are allowed to centralise, and it is then a simple matter to pull out of the ensuing dive. This is not the case with the spiral dive, where the wings must be rolled level with aileron recovery.

This improved map, as well as a map of the walking tracks in the vicinity of the Flying Field is our "centerfold" this month for you to keep. You can also find/download & print further copies of this improved map from our web-site at www.wrcs.org.au and click on the link "MAP OF THE AREA SURROUNDING THE FLYING FIELD".

GPS Notes 
My “Magellan Map 330” setup gives co-ordinates in degrees & minutes, with minutes expressed as ‘m.mmm’ ie. minutes to 3 decimal places. The last digit could thus be called a milli-minute, say “mmin” (= one thousandth of a minute). Allowing for daily satellite variations etc, typical GPS accuracy these days seems to be about +/- 2 mmin, equivalent to +/- 4 metres. To closely relate mmin to metres, just compare the side-by-side Longitude and metre scales along the top (north) side of our Belrose-Field map. 
During any bush-bashing, my GPS screen clearly displays the desired Goto-track as a solid straight line. Then my actual walks appear as thin dotted “ant trails” meandering near the Goto-line. Guided by these 2 clear features, its quite easy to plan & carry out a GPS-based grid-search (without the old-fashioned urge to mark chunks of searched bush with lengths of string etc.), see discussion following.
Model-recovery by GPS 
Points on the Belrose map were plotted as my best-estimates to the nearest 1 mmin (about 2 metres). Thus in theory a 1st-pass walk along a good GPS goto-line will always lead you close enough to spot your crashed plane. (A “good” goto-line’s bearing is within 1 degree of the crash-site).
However if your bearing input was a few degrees off, and you find nought on your first-pass, don’t dispair. Just commence a grid-search by using a GPS ant-trail to steer you back about 10 meters to one side of the GPS goto-line that you’ve just walked as the1st-pass. 
In Nov-03 my downed Ultra-Sport 60 was found after 5 minutes on such a 2nd-pass. 
Of course the process could be continued to cover an ever-widening belt of bush on both sides of the original goto-line. But with careful Visual-noting & GPS-entering of your crash-site bearing, an extended seach should seldom if ever be necessary.
Getting a good GPS-bearing on the crash-site (K) 
The method below (all in degrees-True) worked well for me : 
— At crash-time, note a nearby direction marker (M) that’s directly in-line with K.(eg. M may conveniently be a tree or rock on the far-edge of the field). 
— Then walk a straight-line to M and note your GPS heading (H). 
— Into your GPS, fix or ‘mark’ M as waypoint M. 
— Return to your initial pilot area (P) and mark this as waypoint P. 
— Enter ‘Goto M’ and the GPS gives bearing ‘B’ = direction of M from P. 
— Do a quick check that B = H to confirm that B is a good GPS bearing. 
— Move the GPS map cursor to point ‘X’ , some100 m. beyond the K-area. 
— Manoeuvre the cursor so that X (like M) is on bearing B from P 
— While you’re still at P, enter ‘Goto X’ to create the vital good ‘Goto-line’. 
— Start walking the Goto-line to find your aircraft.

Glider Day

It didn’t look like an ideal day first thing in the morning – solid cloud, cool air and no wind – where was the lift going to come from? Nine people registered for the glider section, eight flew and six survived.
By the traditional late start things had changed, the sun was coming out, a gentle breeze came from the sea and Garry Welsh proved there was lift in the very first flight of the comp producing a very respectable 4:52 (against a  target of 5 minutes) and landed close enough to the spot to pick up an extra points for the landing (maximum 30 points). Mike Minty followed him up flying his Aquilla that has sat in his workshop for the past 4 years and proved that there was sink as well as lift with a glorious 49 second flight through a tree! 
Tom Sparkes did a little better with a 1:40 and  from his trusty Stepp 3 and was followed by David Foster with his sort of Gentle Lady and 3:08 and a maximum landing bonus. David Sindel was next up and put in a respectable first flight. 
Col Simpson did even better than Mike M, he managed 55 seconds before plonking his shiny new yellow Stepp 3 into the top of a tall tree and Luke Swinkels volunteered to climb up and retrieve it! It wasn’t badly damaged but could not continue in the event. 
John Channon was next and in trouble from the minute he let go of the plane. It veered left, kept on going left and eventually peeled off the bungee and  vanished into the trees followed by a very loud CRUNCH! (See Col 9.9 for more on this). Chris Mort finished round 1 with a happy flight.
The second round saw general improvements in performance with Tom Sparkes doing exactly 5:00 but missing out on the landing points. Not bad considering he had the unnerving experience of being joined by an eagle at some height. Judging by the drawn in wings and the extended claws it wasn’t feeling in a friendly mood and, having been brought down by an eagle before, Tom took rapid evasion action! At the end of the round David had taken over the lead from Garry but only by 7 points. The third round saw a mix of fortunes including Garry joining the tree explorers and Tom putting in an excellent flight for the highest score that round.
The second event, the Electric with five entrants, saw John Channon again checking out the foliage at the end of the field. Having landed in it, he even tried to power his way out but had to resort to tree shaking and some pole help from Garry & David in the end. 
Col Simpson, determined to do better this time, made a very presentable 5:05 and lots of spot landing points. 
Interestingly 4 of the 5 flew over the 5 minutes in the first round just showing how useful those whirry things on the front can be in keeping the plane up. There was an interesting comparison between Col's sophisticated and powerful and Luke Swinkels little foam jobby, in truth little more than a “toy aeroplane” that had been assembled a few minutes before the comp. Both did a few seconds over the 5 minutes but Col only used 26 seconds of motor whereas Luke needed 1:22  thus suffering a large penalty as motor run seconds are deducted from duration seconds.
John Channon was the only person to achieve exactly 5:00 AND a perfect spot landing though it has to said that the spot needed a degree of enthusiasm and energy that left half the tailplane hanging off! 
David Foster demonstrated his method of removing kinetic energy as he approached the landing at a speed that would clearly take him a 100m past it – he hit the ground about 50m in front of the spot at a fair old speed throwing up a cloud of earth and then floated in to an almost perfect landing. The plane was unharmed much to more than one spectators surprise!
So in the end the results were:

GLIDER 1st David Foster 2nd Garry Welsh 3rd Tom Sparkes 4th David Sindel Also competed (in alphabetical order): John Channon  Mike Minty Chris Mort   Col Simpson   Al Zuger

ELECTRIC 1st Col Simpson 2nd David Foster 3rd Tom Sparkes Also competed (in alphabetical order): John Channon  Luke Swinkels

Special thanks go to Kerry Smith for acting as Contest Director and Chris Hebbard for handing out the prizes. A very pleasant (and peaceful!) way to start the annual competition season.

CARBURETTORS  - HOW TO SET THEM
The carburettors used on model aircraft are of three different types.  The first is a diaphragm or butterfly carburettor and this is the type most commonly found on the large engines, particularly the convert type engines.  Examples of these are Walbro and Dellorto.  (This section, which may only have a small readership, could be reproduced in a later article if there is general interest and members with or thinking of using this carbie would like the BW low down. Please let me know)

AIR BLEED CARBURETTOR.
The next carby is the air bleed type as is found on Enya and some OS as an example.  The sketch shows the hole in the body of the carburettor and in the Enya, a spring loaded screw at the top, and in the side for the OS.  The hole and the screw serve one purpose only and that is to adjust the amount of air available to the engine at idle rpm.
As the spring loaded screw is wound IN so that it partially blocks the hole it, obviously, impedes the flow of air.  Winding IN gives a RICH mixture and OUT gives a LEAN mixture.  The richness and leanness of a fuel mixture relates to the amount of liquid fuel supplied to the engine.
A lean mix is a mixture with too little fuel/too much air and a rich mix is too much fuel/too little air. The fuel comes from the main jet but the rotor of the carby is closed in the idle position so the air has to be supplied by the hole. 
When tuning, the control, run the engine until well warm and correctly adjust the main mixture  needle.  Close (pull back) the throttle until the engine is idling close to the desired speed, generally around 2,800 to 3,000 rpm.  Very carefully adjust the air bleed screw in small amounts and listen to the engine.  If the rpm increases and the engine stops then the mix is too lean - wind the screw in a little.
If the engine slowly loses rpm and stops then the mixture is too rich - wind the screw out.  Adjust the (main mixture) needle until you have the highest rpm the engine can retain without stopping, then wind (the screw) in about 45 degrees [1/8th of a turn] to give a very slightly rich mixture.
Except in the most extreme circumstances, this is a set and forget area as it is very tolerant of prop loads, plug changes and extremes of weather.
(Air bleed) is a very simple and reliable mixture control so why isn’t it used on more carbies?
It has two drawbacks!  To choke the engine for starting the throttle must be open otherwise air  is drawn through the hole and it drastically reduces the suction on the fuel supply.
The other problem is that it controls the fuel mix for a very small amount of throttle movement, so that the engine is slobbery rich in the mid range.
The method of overcoming this to some extent is to fit a carby with a small venturi and this is the case with the Enya and OS and this has a side benefit in that the suction from the tank is greater so tank position is not so critical with most of the engines fitted with these carbies.
Before we move too far away, on both these carbies you can see another spring loaded screw, in both cases, on top of the carby.  This is the rotor retention and idle speed screw.
Serving a double purpose it retains the rotor in the carby body and can also be adjusted to set the speed of the idle.  In most carbies, if this screw comes out, the rotor follows quite rapidly so keep an eye on it occasionally.

THE MAIN NEEDLE.
The main mix for these carbies is the same as most others and that is a tapered needle in a stepped hole tube commonly called the needle valve. The end of this tube is exposed to the air flowing through the venturi section - the main hole through the carby into the engine, - and there it does the job of a fuel jet or spray bar. 
The needle valve is drilled to a diameter that is a neat fit on the needle and, close to the jet end, the diameter of the hole is reduced.
As the needle is wound in, the pointed end enters the stepped down hole and gauges the flow of the fuel.  Further in, less fuel and vice-versa.
Adjusting this mixture is common practice gained by experience and the experienced modeller knows well to tune a little on the rich side as the engine unloads in the air and a fully tuned engine on the ground is a lean engine in the air.

THROTTLE ARM ADJUSTMENT.
The other adjustment on the carby is the throttle arm and this is the most neglected adjustment of all in most cases.  I am certain you know well the methods of setting differential aileron travel, for example, by using a disc on the servo and connecting the aileron rods behind the centre of the disc. 
Also, when installing a control horn on a surface such as elevator or rudder, the importance of having the connection pivot in line with the hinge line to obtain equal travel.
The same problems crop up with throttle connections where we need a Set your engine servo also in the halfway position and then make the connections between the two.  Now you will find there is no "ganging up" of the throttle movement and the changes will be reasonably even as you move the stick on the Tx. 
The big benefit is that you will have very nice control at low throttle which, as any scale flier knows, is extremely important when coming in for a landing talking of which, it is about time for me to come to the final leg.

.......and that final leg, twin needle or fuel metering carbies, will be reproduced in our next issue