TThe Weatherman was designed in 1948 by Cyril Shaw for the Mills 1.3 engine. In 2005 Dick Roberts and Brian Lever (of Peterborough Club and SAM

35) drafted rules for new classes allowing the use of engines up to 5cc, and after publicity at the Cabbage Patch Nationals celebration of 60 years Control Line fl ying, was fi rst fl own in 2006. Since that time more classes have been introduced and the format has proven very popular as an introduction to CL speed. However, in recent times

the event has become more and more competitive with very high performance engines being used. Whilst many of us enjoy the competitive challenge and going faster and faster, some feel that the spirit of the event has been rather lost. Some competitors, in particular newcomers, are being put off joining in and entering.

It is with this in mind that we are introducing a new SAM 35 class called Clubman Class Profi le Weatherman. The model is very simple and uses a standard, reasonably priced but good quality, readily

available RC engine converted for CL use. Only a standard fuel formula can be used and steps have been taken to ensure an even playing fi eld for competitors.

It is anticipated that a model built to the specifi cation below will be available for potential competitors to try at events, providing they have full BMFA insurance. Even if you are a long term modeller, please read the construction article as it is based on many years experience and covers certain details not shown on the plan.

14 AeroModeller - April 2015

Entry Level CL Speed

CLUBMAN CLASS PROFILE

WEATHERMAN

Tony Goodger, Peter Fox, David Smith et al. have sim-plifi ed this classic CL speed model to encourage more modellers to ‘Have a Go’.

First prototype ready for fl ight testing.

15

WEATHERMAN

BASIC RULES

1. MODEL

To be made with a profi le fuselage having a minimum nominal thickness of 12.7mm (1/2”) to the side profi le as shown on the standard size Weatherman plan. No cowling or fairing of the engine top half or tank is allowed.

2. WING

To be made from 9.5 mm (3/8”) minimum thickness balsa sheet to the standard plan shape with no dihedral, with a hardwood spar

which may be extended to full span to take the bellcrank. The shaped aerofoil will retain a minimum root thickness of 9.5mm. A tip weight of 14 grams (½ oz) shall be used.

3. TAIL

To be made to the standard plan shape with a minimum root thickness of 4.8mm (3/16”).

4. ENGINE

The engine to be used is the ASP S15 Club Combat fi tted with the standard silencer as supplied by Just Engines (01747 835817). No performance enhancing modifi cations are allowed to the engine, in particular enlarging

of the venturi or exhaust outlet. Pressurisation of the tank by the engine exhaust may be used.

5. SPINNER

A 45mm (1¾”) spinner is to be used.

6. UNDERCARRIAGE

To be a single 10 gauge leg fi tted with a commercial wheel having a minimum diameter of 51mm (2”) and width of 19mm (3/4”).

7. PROPELLERS

Only unmodifi ed commercially available reinforced nylon propellers shall be used. Those designed for electric use are specifi cally prohibited.

8. FUEL

Only Formula Irvine Sport 10 glow fuel can be used and this will be supplied by the organisers at each event.

9. LINES, PULL TEST AND HANDLE

Either two 0.3mm minimum diameter single strand piano wire or multi strand (laystrate, staystrate or superline) wires may be used. Line ends must be made in accordance with BMFA recommendations (Control Line, Book 1, Section 4.1.3.6). The length measured from the centre of the handle handgrip to the centre of the engine crankshaft is to be 16 meters (52’ 6”). A pull test of 11kg (25lbs) will be applied to the model, handle and lines prior to each fl ight. The use of a restraining safety strap attached to the handle is mandatory for all fl ights.

10. TIMED DISTANCE

This will be 1/2 mile standing start, i.e. 8 laps. The control handle must be on the centre of the pilot’s chest by the end of the fi rst lap without any degree of leading or whipping the model. Whipping after the 1st lap will result in disqualifi cation.

11. Competitors who have previously won the Weatherman League are not permitted to fl y in this class.

Model ConstructionThis is an acceleration event so model weight is crucial. It is therefore important to select the correct grade of suitable materials and aim for a strong, durable fi nish to reward yourself with a competitive model. There are different approaches to building a model such as this, and the following describes my approach together with some alternatives to aspects of the construction.

Wing and TailFirst of all select some good quality balsa for the wing; with this shape and thickness, the use of quarter grain is not essential. After cutting the balsa to shape, carefully cut a gap for the hardwood spar and glue

The business end.

Above: Control and tank installation.

Left: The hardwood spar needs to be a good tight fi t.

16 AeroModeller - April 2015

it in place. For durability, the leading and trailing edges need to be reinforced with hardwood, or as I do now, by the insertion of thin plywood strips. The latter method can be rather tedious as it requires cutting a narrow slot around the periphery of the wing but has the advantage of providing a guide when shaping the wing section. I use a simple tool (see photo) which make this method easy.

It is best to use a semi-symmetrical lifting section with a 1/3 / 2/3 split (typically as used on team racers) and the wing may be tapered towards the tip. I leave the centre section square for insertion in the fuselage as I fi nd it easier to line up, but some prefer to sand the wing section prior to insertion and jigsaw the fuselage hole accordingly. An alternative method used by some, is to laminate the wing from different thickness

sheets with a ply centre. Tip weight needs to be added to prevent turning-in on take off, and we specify 14g (1/2 oz) with this model.

The tailplane/elevator may be made in a similar way with a lifting section to improve the fl ying characteristics in windy conditions. Hinging can be by several methods, but I now use mylar strips, 10mm wide x 0.02mm thick, epoxied and pinned in slots in the tailplane and elevator. This seems more durable

Entry Level CL Speed

Cutting slots in the wing leading edge for plywood inserts. Set a Dremel type cutting disc at the correct height above the fl at bed of a pillar drill to make the cut. Do beware of cutting your fi ngers!

The wing section is worked to this profi le before glass/epoxy skinning.

Take care to align the engine mounting plates.

The Profi le Weatherman is slotted together to check wing and tail incidences prior to fi nishing.

17

than other methods I have used which can become brittle with painting, and as the mylar material is ‘springy’, it gives a degree of self centering. Other methods are nylon fabric strips or a fi gure of eight cord. When assembling ensure that both wing and tail are set at zero incidence to the engine bearers.

The leadout guide can take a lot of wear. 3mm plywood is a satisfactory material, but the holes must be bushed with brass tube or eyelets. I always incorporate a series of holes to allow adjustment before fl ying. Add tip skids if you wish to protect the wing and tail tips from damage using blobs of epoxy or drawing pins.

FuselageThe fuselage is made from sheet balsa/plywood. On my prototype I used just 12.7mm (1/2”) balsa, but as additional strength is needed in the tail area it was decided to laminate the fuselage on our second model as shown on the plan. The

wood needs to be selected carefully as heavy wood will lead to a rearwards centre of gravity and diffi cult fl ying characteristics.

Start by cutting the bearers to length and drilling holes for the engine bolts. I always mount the engine on steel plates screwed and epoxied to the bearers using the engine bolts. This is an old team race trick to spread the load and improve performance. Bolt the engine to the bearers with the mounting plates in place and use this as a template to cut the bearer positions and subsequently glue in place. If the Under Carriage leg is mounted on the engine side, ensure the plates do not foul the saddle clamp. The ASP logo on the engine crankcase is quite proud so I found it necessary to fi le some of this away to ease fi tting.

As the rudder is often used as a steady prior to release, it needs to be strong - hence the need for a plywood core. Balsa can be laminated either side of the fi n to blend in with the fuselage. There is no need to incorporate any rudder offset, and a piano wire tail skid needs to be added. The drawing shows a tapered section to the rear of the fuselage which is done to minimise weight and maximise aerodynamic effi ciency in this ‘speed’ class. This thinning

will slightly reduce the gluing area at the tail joint so if the builder wishes, this thinning can be kept to a minimum.

AssemblyWhen gluing the components together, it is imperative to ensure that they are all aligned with no positive or negative incidences. This will ensure that the model has good fl ying characteristics with the minimum drag. The wing/fuselage joint needs reinforcing with two dowels as shown. I always like to fi llet the wing and tail joints as this gives added strength and improves the appearance and aerodynamics.

FinishingThe original Weatherman models would have been fi nished with tissue and dope. For competition use I prefer to use a modern epoxy glass fi nish over the entire model. Properly applied this will give an immense increase in strength and durability for very little weight gain. If you have not used this system before, it

is worth practising beforehand and researching techniques. The centre of gravity (CG) is best between 10mm and 20mm back from the leading edge. Aim for a fl ying weight of 400-450 gms (14-16 ozs).

Fuel TankThe ASP 15 proved to be quite thirsty in testing, so in order to get the required laps with some to spare, a capacity of 20cc is required. As no suitable commercial tanks are available a simple front feed unifl ow tank was designed for the model.

Start construction by cutting a tinplate blank of overall dimensions 54 x 73mm. Carefully drill the 2 x 3mm mounting holes (on hardwood to prevent tearing) 2mm from the outer edge and then fold the two sides in. Then cut the second tinplate blank to 80mm long by a nominal 25mm (to fi t inside the fi rst folded section) and carefully drill the 2 fuel tube holes to be tight fi t on the brass tube and fold.

The usual recommendation for soldering is to use ‘killed spirits’ (zinc chloride solution, Bakers fl uid), but I fi nd that a modern water soluble plumbing fl ux to be far superior to use. An example is Frys Powerfl o which is also less corrosive as the fl ux ingredients are

only active at soldering temperatures.Commence fabrication by soldering the

fuel feed pipe in place leaving a solder fi llet both sides of the tin plate. Repeat this process with the vent pipe but also solder it in place at the end of the bend. The 2 halves of the tank can then be soldered together, the dimensions allowing for a 1mm soft solder fi llet all round.

Finally fi ll the vent tube end with solder with a modelling pin inserted down the tube, then pull out. This leaves a small vent hole which will minimise fuel siphoning back through the exhaust connection during starting.

Flush the tank with fuel or alcohol, then pressure test it under hot water and repair any leaks. The tank is fi lled from the fuel feed pipe while holding the model vertically until fuel is seen to overfl ow from the exhaust. The tank is attached to the fuselage side using 3mm screws. If necessary the holes can be reinforced by removing the screws and dropping in some thin cyano ‘super glue’.

HardwareThe elevator horn shown is a standard RC item and is operated by a 1.6mm (16swg) piano wire pushrod. If you do not have a ‘Z’ bending tool, use swing keepers for the ends. The bellcrank needs to be securely fi xed to the spar with a through bolt.

The undercarriage is formed from 3.2mm (10swg) piano wire secured with a top bend of about 12mm long inserted into a matching hole in the top bearer and a saddle clamp screwed to the lower bearer. On the fi rst

Glass and epoxy fi nishing the fuselage and fi n.

The fuselage after trimming the excess glass cloth.

prototype the undercarriage was mounted on the inboard side of the bearers with the wheel is offset to the inside. This was found to give improved ground handling. However with the longer cowl it is more sensible to have the leg on the inside which requires angling the piano wire inboard at about 10°. Wheels need to be fi tted securely and I always use a soldered washer on the inside and a collet with Loctite on the outside.

The best spinner to use is that manufactured by Irvine because of having an aluminium backplate and being more resistant to scuffi ng by starter rubbers. The engine can have the

needle valve pointing downwards but while protected against breakage, it is very diffi cult to adjust. By twisting the needle valve assembly when uppermost so that the feed tube points towards the engine mounting lugs, it can be angled backwards thus making adjustment easier although prone to damage if the model turns over.

Leadouts can be made from 20g piano wire or heavy duty stranded wire. Don’t be tempted to use fl ying wire through the bellcrank holes these have been known to fail.

To make things easier for you, we’ve lined up some UK suppliers to help source components. So in addition to Just Engines, Belair Kits (01362 668658) are going to produce a set of laser cut wood parts. Den Saxcoburg of Dens Model Supplies (01983 294182) has kindly agreed to have all the required hardware available, including engine plates and a tank kit.

FlyingThis model is particularly easy to fl y and very stable, even in wind, providing it is built accurately and has the CG in the recommended position. This is a speed model so only limited elevator movement is required. The best performance will probably be obtained using APC propellers. Start with an 8 x 6 to get the feel of fl ying the model, then try a 7 x 6. Always whip on takeoff to prevent turn in and try to land with some speed otherwise you risk stalling and a consequent hard impact.

We look forward to seeing you at future Clubman Class Profi le Weatherman events which will be publicised in the AeroModeller and on the BMFA and SAM 35 web sites.

18 AeroModeller - April 2015

Hardware Requirements 2” bellcrank Elevator hinge material Elevator horn 16g pushrod 2 Swing Keepers Brass ferrules or 4mm eyelets 10g piano wire leg 10g saddle clamp 10g collet 2” R/C type wheel 45mm spinner Engine plates, mounting bolts, washers

and nuts Fuel tank and fuel tube Line connectors Lines and reel Handle

Useful References and SuppliersThe following references and suppliers will be of use when building and fl ying the model:

Faster Phantoms parts 1 and 2, AeroModeller July & August 1996Turtle FAI team racer AeroModeller November 1973Control line fuel tanks AeroModeller Annual 1967-68

Engines and accessories:www.justengines.co.uk

Hardware for model:www.densmodelsupplies.co.uk

Laser cut parts and kits:www.belairkits.com

SAM35 for the latest on Weatherman Speed:www.sam35.org

PAW staystrate wire:www.eiffl ander.com

Control line accessories:www.clubtamaran.com

Epoxy glass materials:www.bucks-composites.com

Competition propellers:www.apcprop.com

Single strand fl ying wire:www.heckscher.co.uk

Epoxy fi nishing paint:www.fl yingaces.co.uk

Entry Level CL Speed

Completed tank

Position of Needle valve

Keen Weatherman fl yer Dick Roberts with the smart looking

Profi le Weatherman.