Crazee-BAT

1170mm Crash Resistant Sports Aerobatic Power Model for 0.20 - 0.32 cu in. Engines

Designed by Stan Yeo

Produced by PHOENIX MODEL PRODUCTS

Introduction

The Crazee-BAT is an EPP (expanded polypropylene) model designed to put the wow back into sport flying without some of the risks associated with this type of model and flying. EPP models have a reputation for being very tough and the Crazee-BAT is no exception. It will survive all but the most severe crashes with only a broken propeller and if unlucky a broken engine mount. Crazee-BAT is quick with responsive controls and good low speed handling characteristics. It will perform all manoeuvres expected of a flying wing including loops, rolls, and inverted etc. Although the finished model is unlikely to be as aesthetically pleasing as its wooden counterparts this is more than compensated for in the short build time and durability. The accessories supplied in the kit are as used in the prototypes and more than up to the job they have to do. Items not supplied in the kit include the adhesives (2 part Epoxy, thin Superglue and Spray Impact Adhesive). Radio control equipment (2 standard servos 4ch Rx and a square Rx battery), the engine (SC25/32 or MDS28 etc.), Sellotape Diamond for the Elevon hinge and coloured vinyl tape (used to protect covering from ultra violet light and decorate the model). We can supply all of these items at competitive prices so please ask if you need them.

Tools / Materials Required

A limited range of tools / equipment is required to build Crazee-BAT. These include a Scalpel with a supply of spare blades, a sharp long bladed knife, 180 grade Wet & Dry abrasive paper, a soldering iron and a drill with a selection drill bits. The long bladed knife can be made from a broken piece of hacksaw blade about 75mm long, sharpened on a grindstone (take care not to overheat the blade when grinding the teeth off as this will destroy the hardness of the steel) and honed on a whetstone or oilstone. This blade is better than commercial ones as due to its flexibility. It is very useful when trimming the EPP attached to the fuselage sides.

R/C Equipment

A 4 channel radio control set on 35mHz, with rechargeable batteries. 2 standard servos and 1 mini servo. If the transmitter does not have Elevon mixing then an airborne mixer is required. The receiver battery should be of the 'square' type rather than the 'flat' type normally supplied with the set. If you do not have a transmitter with built in control mixing then it may be more cost effective to buy a new TX rather than buy a mixer. The Futaba 6EXA comes highly recommended as it not only has the necessary control mixers but has a 6 model memory and other facilities which are very useful in setting up the Crazee-BAT.

Building the Wing

1. The wing is built upside down so that the reduction in thickness towards the tips results in a small amount of dihedral rather than anhedral.
2. Using a sharp scalpel and a 600mm straight edge widen the mainspar slots to accommodate the spars. This is necessary because the computer controlled hot wire cutter cannot cut parallel slots when cutting a tapered wing.
3. Using 2 part Epoxy (12 minute recommended) fit the top mainspars. Note these are 5mm thick. Weight down on a flat surface whilst epoxy sets.
4. Again using epoxy fit the spruce rear spars. Use masking tape to hold spars in place whilst epoxy sets.
5. Using Superglue to laminate the 2 pieces of 1.5mm ply that make up the front and rear wing spar braces (hold items together and run superglue along edges).
6. Join wing using epoxy and fit front and rear spar braces.
   
7. Angle ends of bottom mainspars to match wing root and fit. Note bottom spars are 3mm thick.
8. Shape wing tips.
9. Bevel the front of the elevons as per plan to accommodate down elevon. Cut elevons to length and shape.
10. Lay wing on flat surface the correct way up. Position a wing servo just behind the mainspar at right angles to the rear spar. Route the servo lead as per the plan and adjust servo position so that there is sufficient free lead to plug into the receiver. Mark position of servo.
11. Centre both the Elevon servos using the Tx before fitting. After centreing rotate the arm one spline to the rear to counteract Elevon differential movement due to the top hinging of the Elevons.
12. Make a rectangular cutting template, allowing for the output arm and marginally smaller than the servo. The servo needs to be a tight fit in the wing. Use the template to cut a rectangular hole through the wing.
13. Cut slots for the servo lugs and servo lead. Push servo into wing so it is flush with the top surface.
14. Turn the wing over and fill the gap between the servo and the bottom of the wing with an offcut from the rectangular block removed from the wing.
15. Repeat procedure for second wing servo.
16. Cut slot 1mm wide and 3mm deep, routed as per plan, to house servo lead. Bury servo lead in wing.Lightly sand the wing and fill in any gaps around the mainspars. Any filler can be used including epoxy loaded with micro balloons or Polyfilla.
17. Fit fuselage to wing and mark fuselage position on wing and wing position on fuselage at nose. Remove fuselage from wing.
18. Lightly spray wing with impact adhesive and cover the wing following the sequence indicated on the plan i.e. start at the rear spar and work forward overlapping each strip by 5-10mm. On the top surface of the wing DO NOT cover the previously marked fuselage area except for the first 2-3mm. Where the CW Tape goes around a compound curve the wrinkles can be reduced using a film covering iron at a suitable temperature. This will not harm the EPP providing the iron is not allowed to dwell in one spot too long.

Building the Fuselage

1. Lightly sand fuselage sides with 180 grade Wet & Dry (use dry) to remove any traces of ply release agent.
2. Using plan and downthrust distance piece mark position of engine bulkhead on fuselage sides.
3. Drill holes for engine mount in engine bulkhead. Please note the mount is offset to allow for engine sidethrust (see plan). Mark the engine bulkhead front and back and fit the 4BA pronged 'T' nuts to back of bulkhead.
4. Fit 6mm triangular strip to fuselage sides using Superglue ensuring there is a Left and Right hand side!
5. Superglue balsa downthrust block and fuel tank distance piece in place ensuring that the fuselage is square (use a fitters square / set square).
6. Superglue engine bulkhead in place then join fuselage at the rear ensuring that fuselage is straight.
7. Fit 1.5mm ply fuselage top, front and rear. To encourage the ply to bend to the curvature of the fuselage sides wet the top surface.
8. Using rubber bands locate the ply fuselage bottom. Fit fuselage to wing and mark length of fuselage bottom. Cut fuselage bottom to length and glue in position.
9. Trim excess ply from top and bottom sheeting.
10. Superglue 8mm triangular strip to base of Fin. Mark centre of fuselage at front and back of Fin and fit Fin ensuring that it is vertical. If after gluing Fin is not vertical then slice triangular strip on inside of bend and pack out with thin card and Superglue in place.
11. Fuelproof the engine compartment and front of fuel tank bay with thin Superglue. Do this outside or in a well ventilated area as the fumes carry a hazard warning. Alternatively use varnish or a proprietary fuelproofer.
12. Using spray impact adhesive fit EPP sheet to one side of the fuselage. Spray both surfaces and allow a few seconds for solvent to evaporate before making the joint. Do not worry about getting impact adhesive on the Correx fin as it can be easily removed using white spirit. Using a long bladed sharp knife trim the off the excess EPP. Keep the cutting angle as low as possible to avoid tearing the foam. As mentioned previously the best tool for this task is the sharpened hacksaw blade described in the Tools / Materials section. Lubricate the knife with white spirit.
13. Fit EPP to other side of fuselage and trim to shape as before.
14. Fit EPP to base of fin. Note EPP will have to be relieved to accommodate triangular strip at base of fin. Fill in gap at front of fin with scrap EPP.
15. Fit EPP to front of hatch and bottom of fuselage at rear (this piece is slightly thicker than sides and top).
16. Manufacture hatch. Use spare ply to for hatch locating tongue.Cover Fuselage. Lightly sand and fill any gaps as before.
17. Check fuselage fit to wing and adjust as necessary.
18. Spray fuselage with impact adhesive and cover fuselage with CW Tape starting with the sides. Do not cover the fuselage where it is overlapped by the wing except for the first 2-3mm. Use iron as before to remove any wrinkles.
19. Fit fuselage to wing using 2 part epoxy. Using short 25mm wide strips of CW Tape seal wing to fuselage joint.
20. Cover the model with either coloured vinyl tape (recommended) or an heatshrink film to decorate the model and protect the base covering (CW Tape) from the effects of ultra violet light, including the inside of the engine bay. If using coloured vinyl tape use iron as before to shrink tape around compound curves.
21. It is recommended that the ailerons are covered in a heat shrink film such as Easycoat in ONE piece (seam on inside of hinge i.e. elevon leading edge). This avoids having exposed edges that can peel back.
22. Hinge the elevons using Sellotape Diamond as per plan.
23. Drills holes for control horns. After drilling reiforce hole with runny superglue.
24. Before fitting the Elevon servos centre the servo / output arm. After centreing rotate the arm one spline to the rear to counteract Elevon differential movement due to the top hinging of the Elevons.
25. Connect up elevon controls.
26. Install fuel tank with fuel tubing and fit engine.
27. Fit throttle servo and throttle pushrod. Adjust length for correct operation throttle. Install remainder of radio equipment.

Flight Preparation

With the controls and balance point correctly setup the Crazee-BAT is both easy to launch and a dream to fly but if insufficient care has been taken during the setting up process then beware! Below are a few notes on preparing the model for flying.

Control Movements:

• Ailerons: +/- 13mm
• Elevator: +/- 11mm
• Balance Point: 60mm - 65mm (from front of engine bulkhead)

1. Check flying surfaces for warps (twisting). Warps can be removed in the wings by twisting the wing in the opposite direction and re-smoothing the covering using a warm iron.
2. Check the balance point is 60 - 65mm back from the front of the engine bulkhead. Adjust as necessary by adding weight to the tail or screwing weights to the front of the engine bulkhead beneath the engine mount tank. Tape hexagonal pencil to balance point in centre of wing to assist in balancing the model.
3. It is most important that the controls the controls are working symmetrically i.e. full up or down elevator movements are equal and likewise for the ailerons. Asymmetric movement of the elevator will result in 'corkscrew' loops.
4. Use the template on the plan to set the reflex (up elevator) on the elevons for neutral elevator.
5. Check you have the specified downthrust and RIGHT sidethrust. The right thrust is extremely important. If it is wrong then the model will veer off violently to the left or right when launched due to lack of flying speed.
6. Fit the propeller in the 10 - 4 clock position so that when the engine cuts it will come to rest in the horizontal position and not shed a blade on landing.
7. Before flying do a full range check of the radio equipment. This should be a comparison check against a model where the equipment is known to be working satisfactorily.
8. If the engine is new run a couple of tanks of fuel through it before attempting to fly. Run the engine slightly rich in the beginning and do not attempt to adjust the slow running needle valve until the engine is run in. We would also advise that the idle RPM is set slightly higher again until the engine is run in. We would also suggest the model is flown at a safe height should the engine cut prematurely.
9. Always allow the engine to reach its operating temperature by running at full throttle for a few seconds before launching the model.
10. Charge the batteries!

Flying

The following notes are not designed to be comprehensive as pilots of the Crazee-BAT should be relatively experienced. Due to noise and other problems etc. that the hobby is experiencing please think of others when you are flying. It is strongly recommended that you do not attempt to fly without third party insurance. The British Model Flying Association (BMFA) Tel. No. 0116 244028 will be able to provide you with third party insurance at nominal cost and also give you details of your local club.

1. If the above procedures have been completed successfully then the model should fly straight of the board as they say with the minimum of trimming.
2. Check all controls operate in the correct sense i.e. the Elevator goes down when the control stick is pushed towards the top of the case, the right Aileron goes UP when the control stick is moved to the right and the engine shuts own when the throttle stick is pulled towards the bottom of the TX case.
3. Crazee-BAT is launched underarm at full throttle, in a slightly nose-up attitude with a small amount of up-trim to counteract the 'dip' after launching due to lack of flying speed. Once flying speed has been achieved then the trim can be returned to neutral.
4. Adjust aileron and elevator trims as required until the model will fly hands off in a shallow climb at full throttle.
5. To check for correct sidethrust carry out a fast low pass, into wind and put Crazee-BAT into steep climb. It the model veers to the left or right as the flying speed drops off this would indicate the sidethrust needs adjusting.
6. On going quickly to full throttle from idle the model will 'dip' slightly until it reaches full flying speed.
7. Model dives in a turn. Most likely cause not enough up elevator applied in the turn.
8. When flying inverted the model will require a small amount of down elevator. If it requires an excessive amount this could indicate the balance point is too far forward, if very little then it could be either too far back or too much downthrust. A 'twitchy' elevator or a tendency to spin would indicate the balance point is too far back.
9. When flying inverted be aware that when turning, particularly when close to the ground, that some elevator movement is lost with the input of aileron control. It is not a problem when the model is the correct way up due to the type of wing section used.
10. Carry out a series of loops into wind. If the model screws out of the loop consistently in one direction this could indicate asymmetric elevator movement. Check elevator throws.
11. When the engine cuts there should be a negligible trim change from power on to a shallow but moderately fast glide.
12. If after a bit of a thump on the nose the engine starts to play up then it is a possible that the clunk is tucked under the tubes at the front of the tank. Take the hatch off and check.

Finally should you require further assistance or advice please contact us either by letter, telephone, email or visit our website (http://www.phoenixmp.com) where you can find lots useful information and our full catalogue.

Happy flying

Stan Yeo

Crazee-BAT 040215