Tom's Model Guide

The Mick Reeves Cheetah by Tom Laird. 29/12/99

Notes on buying a Cheetah

It was time to move on from my high-wing trainer so to force the issue, I sold it. That was it! I had to get a low wing model. The A.R.T.F.'s did not look too appealing at the time (although a couple of nice looking ones appeared in the local shop a few weeks later). I had heard good reports about the Gangster series and had decided on the 63 inch version, when I read a review of the new Cheetah in R/C Model World. It was a bit smaller at 52" wingspan but I thought I could cope.

Notes on building a Cheetah.

The R/C Model World article mentioned that this was not a model for first time builders - how right it was. The instructions are 4 A4 pages of CAD sketches with basic guidance instructions. Simply not good enough in my view, so to help anyone thinking of building one, here is a supplementary set. I would also try and get the August 1999 R/C Model World article.

Section A. The first instruction shows the wing bracket being attached to F3. Thanks to RCMW for pointing out that IT MUST go to the top of F3 otherwise it will foul against the aileron servo later on. Click on any of the small pictures for a larger version.

Before you join F2 to the sides, I recommend you open up one of the holes for you throttle cable. I didn't and had trouble getting a hole drilled for a Sulivan snake.

Section B. Before you join the 2 halves of the fuselage together, I recommend you cut 2 slots parallel to the tail recess, and 10mm below it. This is required to allow the elevator "Y" push rod to exit in section K.

Section C. Just a couple of formers. Nothing that a fuselage jig won't cure.

Section D. Remember to put the "V" on the leading edges of the ailerons, elevators and rudder. You might also want to cover them before glueing them in place.

Don't use cyno to stick the hinges in - it eats the foam. Use a toothpick and poke some 60 minute epoxy in instead.

When you add the joint covers over the wing halves, leave space for the servo slot. Mount the servo bearers inside the hole you cut and use a low profile servo. I discovered the hard way that standard ones will foul when you put the wing in place.

Section E. Sand a "flat" on the outside of the joint before trying to add the joint cover. Don't get too carried away though.

Section H. I found this difficult to get right. I hope you have more luck.

Section I. Remember to put the "V" on the leading edge of the elevators where the hinges are. You might also want to cover them before glueing them in place. I would also fit the 2 extra mounting strips (item 28) which are called for in Section L of the instructions.

Section J. The screw will burst the firewall, so I suggest you cut a recess, and glue in a piece of hardwood to take the screw. 15mm x 10mm x 5mm should do. Make sure you can get to the screw when the nose wheel leg is in place since the spring can get in the way. You might also want to cut a slot for the throttle cable while you are at it. The 3mm dowels to hold the tank cover are not / were not in the kit so I used 3mm brass tube instead.

Section K. This bit of the instructions leaves a lot to be desired. First of all do not glue the hardwood bearers in place until you have done a dummy assembly using blu-tack or similar. Do not glue the bearers all the way across (as I did) or the battery will not sit far enough down.

Use a 1400mAh battery and not one of the new 2000mAh ones or the aileron rods from the servo will foul. I held mine in place with a pocket of balsa, then a strap across the top to stop it falling out (see photo).

I swapped the rudder and elevator servo i.e.I put the elevator servo in the centre so that both elevators get an equal amount of rod. I made up a "Y" rod as recommended in RCMW. I held the pushrods onto the wooden strengtheners with a small plastic tie-wrap then put on a fillet of epoxy. This was done after the metal pushrods were in place (hence the slots mentioned in section B).

I used Sullivan snakes for both rudder and throttle and glued them to anything they touched. (See photos).

I used velcro to hold the receiver in place. Nothing difficult here. As suggested I ran the aerial down the inside of the fuselage and out through a hole at the exhaust.

Section L. Run the aerial wire before you stick the bottom on. DO NOT CUT THE BOTTOM SHEET BEFORE YOU GLUE IT IN PLACE as the fuselage side is not a straight line.

Section M. Nothing to go wrong here, except I fitted Apache Aviation engine vibration eliminator mounts so I had to cut a false firewall. Remember to fuel-proof it before fitting the engine. I had to trim the flange of the inside washers to get them to fit properly but that was pretty easy and worth the extra 5 minutes.

Section N. Remember to fuel proof the firewall and fuel tank bay.

The cowl is in 2 halves. I'm still trying to figure out how to join the 2 halves. If you find out, please let me know please.

Section O. Again, nothing much to say here except I shot the pilot for being an imposter, and replaced him with 2 from the local model shop. I filled in the hole in the top deck and painted the bottom of the dashboard with the same colour as the inside of the cockpit. Note the red paint on the switch to indicate the "on" position.

Section P. Paint the inside of the canopy, not the outside. That way the paint doesn't get scratched when it hits the runway.

Section Q. The dummy air intakes. A bit of patience with a scalpel and sandpaper on a flat surface should see you okay. Use epoxy, not cyno to stick them on.

Sections R and S. In my kit the under carridge legs were too long as they went into the wing. A heavy landing and they might have burst through the top surface. These are 3mm piano wire and just laugh at a hacksaw so you need access to a grinder to shorten them a bit.

Section T. As you can see from the pictures, I did mine up as a T45 Goshawk of the US navy. I made the decals from transparent vinyl purchased from ABC Stickers (01678-780069). For the white in the centre of the star on the wing, I put down a bit of white Solar Trim first. All the decals were done with Coral Draw (any drawing package should do). Do not use a paint package or you will get jagged curves (bit-map pictures vs. vector drawings). The decals were sprayed with clear Holts car lacquer.

Take time to set the throws as recommended. They will still be brutal so set your transmitter rates to 50% because you will need it. Use a ruler or straight edge to make sure that the top surface of the elevator is in line with the top surface of the tail plane.

 
Notes on flying the Cheetah

The first flight was the scariest I have ever had. There was absolutely no wind, and with the Thunder Tiger 42 and the 10x6 APC prop the approach was ballistic. Even on the lowest trim setting it was too fast. However, I eventually got it down. The sacrificial bolt was sacrificed as the wing stopped and the body kept going. The wing's trailing edge is slightly recessed to make it flush with the bottom of the fuselage and it splintered the bottom sheet when it parted company. If this is your first low wing model I would make sure the wing can slide out without hitting anything i.e don't recess it unless it is going to affect the incidence angle. It does not look as nice but you can always recess it later when you have things under control. I had set the C of G to about 75mm and found it to be nose heavy, requiring a lot of "up" to be held in. I reset the elevators so that the top surface of the elevator was in line with the top surface of the tail plane and it flew a lot better. I have replaced the prop with a weaker one and have started to practice fast landings on the simulator.

Verdict on the Cheetah

This is a nice looking model, let down by pretty poor assembly instructions. Personally, I think the 63 inch wingspan version of the Gangster would have been a better size, especially for someone like myself who is just transferring to a low wing model.

The model has attracted favourable comments about its looks and I am looking forward to flying it.

The Cheetah sitting on the runway at West Calder

Ongoing Assessment

I have had 7 flights so far with 2 hard landings where the shear bolt did not break. The rear bulkhead was pulled out and caused considerable damage to the internal horizontal platform when it was seperated from the fuselage sides. Either the mounting bolt is too strong (4mm), the threaded securing bush is too far inside the fuselage or it was just bad luck.

Do not use a 1-piece bottom sheet as per the instructions. Instead, use multiple pieces with the grain running across the way.

If your transmitter has the facility, I would use expodential on the ailerons. Currently, my full rates are set to 100% and the low rates are set to 50% for elevator and 65% with 35% expodential on ailerons.

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