MD-3 (oz16085)

About this Plan

MD-3. Radio control sport delta model, for electric power. Pusher layout. Wingspan 26-1/2 in, wing area 288 sq in. Uses foam construction.

Quote: "Build the MD-3, by Al Clark.

A Delta Wing Indoor Flyer. I have a fondness for delta winged aircraft, both full scale and models. I have built and flown quite a few RC deltas with speeds ranging from extremely fast to fairly slow. I got into indoor RC flying in 2008, and have recently had a good time flying micro sized deltas which I designed.

My first design was a small all-balsa model which used the radio and motor from an E-Flite Vapor. It flew OK but was a bit underpowered. My second design was made from Depron foam and used a brushless outrunner motor. It had plenty of power but proved to be faster than I desired for indoor flying.

The MD-3 is my 3rd Micro Delta design for indoor flying, and with it I finally achieved the flight characteristics I wanted.

Lessons learned from my first two designs led me to use in a much larger wing (288 square inches area) on the MD-3 which resulted in the ability to fly quite slowly at low throttle, and yet to fly quite fast at full throttle.

On my second delta design I had incorporated rudder control in hopes of doing flat spins, but that didn’t pan out – application of full rudder merely produced a tight spiral. So I did not use rudder control on the MD-3, resulting in a weight savings.

The all-up weight of the MD-3 is 3.3 ounces, giving a 1.65 ounce per square foot wing loading, and a 1.17 ounce per cubic foot wing cube loading.

Using a Turnigy 1811-2000 10 gram outrunner motor with a GWS EP-5030 prop on a 2S LiPo battery provides 4.5 ounces static thrust, allowing much of the indoor flying to be done at around half throttle.

As with all delta wing configurations, the drag rises rapidly at higher angles of attack, so the extra power is needed for tight turns, small loops, and high angle of attack slow flight.

The MD-3 is quite easy to fly. It is very maneuverable, and the throttle is varied pretty much continuously according to what you are doing and how slow or fast you want to fly. Very small radius turns can be accomplished, allowing the MD-3 to be flown in compact spaces.

At slow speeds you will notice a bit of adverse yaw with turn commands, but it is not enough to be an issue. Differential can be added to the ailerons to correct the adverse yaw, but then roll performance suffers, so I fly my MD-3 with no differential.

The skids on the underside of the wing allow for ROG takeoffs and landings on a smooth surface, and hand launching at half throttle is also easy.

Our indoor flying site has numerous hanging lights and obstructions resulting in a low ceiling height, but the MD-3 nonetheless has no trouble performing loops and rolls. It also flies inverted well with only slight down elevator required.

Here is a link to a short video of the MD-3 at our indoor flying site: https://youtu.be/3G273eK7pF4

In addition to indoor flying you will find the MD-3 is also a lot of fun outdoors in calm conditions. Outdoors you can go full throttle and really let ‘er rip, performing loops, rolls, and inverted flight at higher speeds than indoors.

Construction: The MD-3 is built entirely from 6mm Depron foam, with a bit of 1/64 and 1/32 plywood, and a small piece of balsa. It is very easy to build using odorless CA and CA+ glue. I started construction of mine after lunch, and by supper time it was ready to fly. So grab the materials and let’s get started!

I like to cut all the parts to size and make up a 'kit' before I begin construction. That way I don’t have to stop at every stage to make a part. The 6mm Depron cuts well with a fresh #11 XActo blade.

The previous photo shows all the parts (except for the balsa nose piece and short pieces of 1/32 plywood, which I decided to add after I had already started building). Don’t forget to cut the 45 degree bevel on the front of the two elevens, and shorten the ends slightly for clearance with the wing and tip fins.

Start construction by gluing the 1/64 plywood strips to the bottom of each skid using odorless CA+ glue. This glue cures more slowly than regular CA+ glue, so you will have to hold the strip in place for a minute or so while the glue kicks off. Here are the two skids with the plywood strips installed..."

Direct submission to Outerzone.

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