Wingtips

97

On Other Pages

Sprinkler System page 2Seen At the Field pages 2 & 3Allan Laycock Reminisces page 4Featured Model of the Month page 5Pusher Propeller page 6

Wingtips is the monthly newsletter of the Belconnen Model Aero Club, this issue 15 January 2019

Your editor is away from Canberra and hasvisited a Victorian model aero club. SeeFebruary 2019 Wingtips to find out who hasthe Mustang wind sock.

Page 2

Members may have wondered about the trenches that nowcross the field. Here's the story: To finish the drainagesystem installed after recent heavy rain [see WingtipsOctober 2018], the club hired a Ditch Witch. The machine(driven by Paul Spackman who knows about these things!)was used dig a trench for a pipe that will drain rainwateraway from the clubhouse. Paul also dug three trenches forsprinkler pipes, and the pipes were then buried. Whenfinished there will be an additional four sprinklers to keepthe pits and the multi-purpose area green during dry spells.Field Officer Len Ricardo (left) is connecting the pipes.

Sprinkler System

Seen At the FieldBelow and left, the multi-coloured UltraSport owned andflown by member and frequent visitor from the South Coast,Mike Ward.

Page 3Seen At the Field, continued

Gary Grannell has yet another new model (above),this time a Fly Baby, an ARF by VQ. The engine is anRCGF 26cc and the model has a wingspan of 2.4m

Above and right, MervWright's P40 Warhawk ispowered by a 20cc petrolengine and features afibreglass fuselage.

Below, another of Merv’s, aHobbyKing Stinger Mark 264 runs on 4S.

Below is Peter Ederle's Cessna, model unknown,maybe 172, 175 or 182. It’s an ARF from an unknownmaker, a hand-me-down from Bob Raadts and others.Engine is a Turnigy 55cc turning a 20x12 three-bladedprop -- a two-bladed wouldn’t clear the ground. Itweighs 10 kg and flies nicely, when, as Peter says,bits aren't falling off. (The blind nuts for the wing strutsfell inside the wing and fuselage making theminaccessible.)

Page 4

I grew up in Canberra and old aeromodelling friendswere Ray Murray, Byam Wight, Graham Parkins andFrank Byrne. (Byam, Graham and I were at TelopeaPark High school together.) Most of the aeromodellingin the 1950s and 1960s was done by building fromredrawn and scaled-up plans from magazines such asModel Airplane News, Aeromodeller and ModelAircraft. There was also an Australian magazine calledModel News that later became Airborne. Supplies ofkits were mostly from the UK and Australia as were theengines we used. There many cheap kits for smallrubber powered models of both sport and scale designs.Such kits were of the ‘stick and tissue’ variety andalthough I tried a number of times I was neversuccessful in buildingand flying one of these.Most flying in Canberrawas control line with alittle free flight becauseyou had to knowsomeone who had a fieldin order to do that.Towards the end of the1950’s some radiocontrol was being flownbut many wereunreliable and crashed orflew away – they wereafter all only free-flightmodels interrupted byradio.

After a lay-off for anumber of years I cameback to the hobby in themid 1970’s. Later, information from US magazinesmentioned a new class of model called “Old Timers”.These were designs of models built in the 1930s and1940s of stick and tissue construction, but larger and forgas engines. Originally free flight, with the advent ofreliable radio control systems many were flown in thisway. Having not been successful with the smaller rubbermodels, and now having a radio control system, Irevisited that area and built an Old Timer for radiocontrol. The first one flew ok but suffered the dreadedDutch Roll so I built a bigger one for an OS .40.. It flewwell but I was not sure if it should climb so steeply, ataround 40 degrees. After those early successes I startedbuilding many Old Timers for many different sizedengines and started flying them in competitions inAustralia.

The Americans formed the Society of AntiqueModellers that had chapters all over the US and theworld. I formed a Chapter here in Canberra in 1991(SAM Chapter 83). Also in 1991 I flew in my first SAMChampionships in the USA.

I have now flown in 17 US SAM Champs, plus threein Europe and one in the UK. (They only fly free flightand I gained a second place trophy for my efforts.)

In 2015 I was inducted into the USA SAM Hall ofFame and in October 2018 – the 50th Anniversary SAMChamps – I was one of the Grand Champions for r/c.[See November 2018 Wingtips.]

One of the things that I enjoy about flying SAM typemodels is that you get tobuild and fly modelsthat were from youryouth, plus you join alarge fraternity of like-minded modellers fromaround the world. I haveencouraged a number ofAustralian SAMmodellers to fly in theUS, including BMACmembers. Bob Raadtshas competed with meon 7 occasions and MaxRixon on two occasions.I have friends in Italy(and might get there in2019 for the SAMEuros), and from allover the USA. I send

and receive e-mails, ideas and news including a numberof newsletters from these people on a regular basis.

I would normally build models and take them overseaswith me but this time my friends in Chicago (SAMChapter 117 “the Chicago Buzzards”, aka “the ElectricMafia”) loaned me 8 models to fly and I competed in 11events with them in order to win. I was very sorry tolose a borrowed one in the cornfield that surrounds theAMA flying site but the others survived myministrations and will be able to fly another day.

Continuing from November 2018 Wingtips,Allan Laycock reminisces about Old Timers

Page 5

The Dornier Do 335 Pfeil ('Arrow') was a GermanWW2 twin-engine heavy fighter, which was thatcountry's fastest piston-engined aircraft, beingcapable of 763 km/h. Tandem engines meant lessdrag than planes with engines on the wings.Because of Hitler's refusal, until late in the war, tohave defence aircraft rather than just concentratingon those for attack, the plane was never fullydeveloped and failed to see significant action. There

was an unsolved problem with cooling for the rearengine, which led to failures. Turning to the modelDo 335s, an i.c. engine in the rear is alsoproblematic. (A member recently told me that his Do335 crashed due to an overheated rear engine.)

My model, being electric, doesn't have thatproblem, although there are other issues.

It is a Black Horse ARF of balsa and plywoodconstruction that has a wingspan of 1724mm and aweight of over 6kg. Flaps are fitted, but the ARFdoesn't include retracts -- some from HobbyKing fitperfectly. To locate the centre of gravity far enoughforward, both batteries (4S 4000mAh) must be justaft of the front motor.

Without wind, the take-off run uses the length of therunway, even with the flaps half down. Because ofthe length of the undercarriage struts, the lower fintouches the ground all too easily. (See the take-offphoto, left) Landing is interesting. Full flap worksvery well and changes the trim only slightly, but, with6kg plus of weight, landing speed is faster than I'mused to ... but I'm learning.

Brian Oakes

Featured Model of theMonth – Dornier Do 335

In the absence of another candidate, thismonth’s featured model is one of your editor’s.

Photos: David Green

To see a short video of the Dornier flying, and some shots of the only remaining Do 335, click on the link:https://youtu.be/YnynfkKiO0c

Page 6

The Pusher PropellerFrom a discussion about my Dornier 335 at the field

recently, it appears that there's some confusion aboutpusher props. (With the advent of electric motors formodel planes, pushers can be used to pull, and you don'tneed a pusher to push!)

What is a pusher prop?Obviously it's for those occasions when the motor or

engine is at the back of the aeroplane, pushing it (belowleft, note the ‘P’), rather than pulling from the front (called

'tractor', above right) but there's a bit more to it than that.

Internal combustion enginesIn aeromodelling, the internal combustion engine runs

best (or only at all) when turning anti-clockwise. Whenusing an i.c. engine at the back of the model as a pusher,the engine has to face backwards. This creates a problem –with a normal prop as the thrust will drive the planebackwards. The solution is a prop with the blade anglesreversed, a ‘pusher’ or ‘clockwise’ prop. The engine canstill run anti-clockwise, but the slipstream will go backaway from the plane.

This is bad for an air-cooled engine which can overheatif the model is stopped on the ground for too long as theengine isn’t in the slipstream. Cowling for the planewould be totally out of the question. The history of full-size aviation provides many examples of pusher enginesoverheating. (See both the Cessna and Dornier that wereFeatured Models in this month's and last month'sWingtips.)

Electric motorsThe arrival of electric power for

model aircraft solved some problems,but also brought confusion.

An electric motor will run happilyin either direction, so you don't needa pusher prop for a rear-enginedplane, you just alter the direction ofrotation. Also, electric motors don'tneed as much cooling as i.c., so canbe cowled when used at the back.

Another advantage is that a twin-electric model can havecontra-rotating propellers, meaning that the ‘P’ factor ortorque from either motor cancels out the torque from theother. When you open the throttle the model won't pull tothe left, as with a single. For example, my Amiot 143M isset up this way. The port motor turns anti-clockwise(below left) and drives a normal (tractor) prop. Thestarboard motor turns clockwise (below right) and has a

‘pusher’ prop. (Incidentally, the full-size Amiot was thesame: the port and starboard engines were manufacturedto turn in opposite directions and the props weredifferent.)

(Something to ponder: what props and motor directiondid I have to use so that my Dornier doesn't suffer from "P"factor?)

A Popular MistakeIf the motor is behind the fuselage, there's an easy

mistake to be made. Whatever prop you're using, witheither electric or i.c. power, front motor or rear, the curvedside of the propeller blade must face the front of themodel! The propeller blades are like a wing and, as we allknow, the aerofoil gives most lift when the curved side isfacing up.

I made this mistake on the maiden flight of my DH-2,which has a pusher prop. I'd mounted the prop in theusual way, that is, with the label (the curved side) facingme when I installed it. At full throttle the poor DH-2barely left the ground and, still at full throttle, only justmade it back to the strip. There was also more prop noisethan usual. With the label facing the front, and theconcave side facing the back (photo below) power is morethan adequate.

Brian Oakes