INTRODUCTION

Mach 2 is a fast sports delta for 3 channel radio control.

I have always loved delta winged aircraft and I have built and flown quite a few different designs over the years but they all had one of two problems. If we put the engine on the front we invariably have to add lead to the back to make it balance, or if we put the engine on the back then we have problems with the prop hitting the ground during rotation at take off.

About 15 years ago a guy named Laddie Mikulasko designed a delta with the engine mounted in the centre of the wing, with the prop spinning in a slot in the wing.

This was the answer to all my problems Laddie Mikulasko was a genius. I immediately designed a new delta using this principal and it was a great success and has been flying for the last 14 years.

Chris Mounkley was kind enough to bring his timing gear down to the flying field one day and set it up for me. After several practice runs the delta went through the traps at 115.2 m.p.h., that's 185 k.p.h. Not bad for a prop driven sports delta running on straight fuel.

Mach 2 is a modernised version of my original design using the same wing, but has a new shaped fuselage and fins.

DESIGN FEATURES

Mach 2 is designed for conventional 3 channel radio control using normal elevator, aileron and throttle controls, and does not need complicated sliding servos or computer radios for elevons. Rudders are ineffective on most deltas and are not needed. Nose wheel steering is directly off the aileron servo, or you can add a fourth servo just to steer the nose wheel if you wish. This is what my brother Barry did, but I preferred to keep it light and steer on the ground with my right thumb.

A quick glance at the plans will show the C.G. directly over the fuel tank. This means that the elevator never needs to be retrimed as the fuel tank empties, which is the case with a lot of front engined models.

This model has been designed for .45 to .61 size two stroke engines and because it is a pusher, you will need a pusher prop, unless you have an engine with a removable front housing, in which case you can simply rotate the front housing 90° to the left which reverses the timing and lets the engine run in reverse. Now you can use standard props, put on backwards of course. I use an old O.S. .60 FSR which has the removable front housing.

This gives me the ability to try a full range of conventional props and I have settled on an 11 x 7 for best performance.

The later models O.S. engines do not have a removable front housing but there are still a few brands produced with this feature.

Mufflers? Two other deltas were built in my club and these used standard mufflers pointing directly into the wind. This did not appear to make any difference to the performance of their engines, but you can modify yours simply by installing a commercial flexible muffler extension and trimming the outlet hole so that it does not face into the wind. See photos.

My brother Barry Sherburn built the model featured in this article and all photos are of his model. My original model is now 14 years old and it is too beaten up to photograph, even though it is still flying like a dream.

CONSTRUCTION

Begin by cutting out all ribs, formers, fins, fuselage sides and doublers etc. and number them as you go.

Cover your plan with grease proof lunch wrap or something similar to protect it and start building the wing directly over the plan.

Lay out the two bottom main spars, add all the ribs, and glue the two top spars, the trailing edge and the two leading edge spars.

Now glue in W1 and W2 and the W3 doublers and fit the undercarriage blocks. Also glue in the W4 main spar joiners and the F3A bulkhead.

It is now time to fit the elevator and aileron pushrod tubes and also the tube for the receiver aerial. Next cover the top of the wing with 1.5mm balsa sheet, making sure the grain goes in the direction shown on the plan. I glued all the balsa sheets together first with balsa cement, and then glued the whole thing on to the wing, but my brother Barry glued his wing sheeting on to the wing one at a time. Both methods proved successful, even though we did argue about it.

Now cut out the slots for the fins and add the fin supports under the sheet covering. Chamfer the bottom of the fins as per the plan and make sure they are a nice fit but don't glue the fins in at this stage.

Now you can cover the bottom of the wing.

Next build the fuselage over the plan in the usual way and install the throttle pushrod tube, and then glue the fuselage on to the wing. Make sure you use 24 hour Araldite to join the engine mount former F5 to the fuselage sides and to the wing joiner W1.

With a sharp knife remove the 1.5mm sheet wing top covering from inside the fuselage, including the wing leading edge spar and a small part of the wing bottom covering, back to where it meets the fuselage bottom. You now have plenty of room to fit your tank and radio gear.

Cut out the five pieces of 12.5mm sheet that makes up the fuselage top and shape them so that they fit neatly, and glue the front and back pieces onto the fuselage. Place a sheet of lunch wrap on top of the fuselage and glue the three remaining pieces together on top of the fuselage, holding them down with rubber bands or tape. When this is dry make or buy a hatch release and fit it to the fuselage top. Before fitting the canopy, install a pilot and paint the inside with matt black.

After glueing on the nose block you can round off the fuselage by carving and sanding all the edges and corners. The 6.5mm triangle stock in the corners of the fuselage adds strength as well as allowing the removal of plenty of balsa along the edge, making a nice rounded fuselage. I find this job to be very satisfying.

Install the radial engine mount and place the engine on the mount to mark the bolt holes so that the prop spins in the centre of the slot.

Fit the nose gear by bolting it onto former F3A. Bend and fit the main undercarriage legs, making sure that the model sits perfectly horizontal on the ground.

Sand the elevator and ailerons to shape and install them as per plan.

Install the radio gear, fit the inner pushrods and connect them at each end and adjust so that the elevator and ailerons are level. Now you can play with them for a while. I find that this is also very satisfying.

It is now time to glue in the fins using the fin angle template shown on the plan.

Sand the model all over until it is ready for painting or covering.

Place the model in the centre of the dining room table and stare at it while you decide what colour it should be. Make sure the bottom colour is in contract to the top for easy identification in the air.

BEFORE YOU FLY

It is very important to set the prop so that it stops vertically in the event of a deadstick landing. (i.e. propeller stops against engine compression). I originally set my prop horizontally and found that it blankets the elevator and make deadstick landings very mushy. Set it so that it stops vertically and you will have full control in a glide.

Starting the engine is by your electric starter. I have found there just isn't enough room between the fins to swing a prop by hand. Having said that, I suppose someone will do it, just to prove me wrong.

Remember if your engine is running in reverse you must connect the electric starter leads in reverse to start your engine backwards.

FLYING

Take off and flying Mach 2 is very similar to any low wing sports model except that its a bit faster. Crosswind take offs are a breeze, (pun intended) and pose no problems.

Remember, if you have the nose leg steering attached to the aileron servo, steering on the ground is by your right thumb.

Throttle back a bit for the first few flights until you get the feel of it.

Landing is sheer joy. Like most deltas Mach 2 can be slowed right down and landed nose high, just like the full size ones. I love doing touch and goes without letting the nose wheel touch the ground.

Mach 2 will not tip stall if slowed down too much, but will start to drop the nose. This can be rectified instantly by the addition of a little power.

The prop spinning in the slot makes a beautiful humming sound that turns spectators heads, especially when you put Mach 2 into a dive.

Well that's Mach 2. I hope you enjoy it as much as Barry and I have.