Brushless Mud Bug


Mud Bug flying

Mud Bug flying

I maiden’d my new plane, the Mud Bug, last weekend!  I was a ton of fun.  Now, I’ll tell you all about building it, and converting it to use brushless motors.

laser cut precision

Laser cut parts are a joy to use

All the parts in the kit are laser cut, and fit perfectly.  The design of the plane is such that the shape of the wing is created almost exclusively by bending the wing’s top skin into shape.  There are only a few ribs, and no bottom skin at all.  It’s remarkably light.

Motor stick mount

Motor stick mount

The kit calls for a stick-mount geared, brushed motor.  These are getting pretty out-dated, and aren’t very efficient.  I really like working with brushless motors, so I had to devise a way to mount it.  I chose the E-flight park 250 motor because it was pretty inexpensive and only a few dollars and grams more than the park 180.  It’s possible to mount it inside of a carbon fiber tube (using glue), but you need to use their tube, and it wasn’t in stock.  I just decided to use the cross-mount adapter and make a plywood plate that mounts on the stick.  Where the stick mounts, I added another, smaller, piece of ply to help support it.  It ended up working perfectly.

Front scab plate

I cut a pair of sheets of 1/64″ ply to use as scab plates on the balsa firewall and fuselage parts.  I had read online that those pieces of the original kit were somewhat weak.

back scab plate

back scab plate

This is the scab plate on the back of the fuselage portion of the motor mounting.  These are only there to spread out the loads transmitted from the stick to these parts.

Park 250 mounted

Park 250 mounted

The motor mounting process went beautifully.  At first everything fit so tightly that I didn’t need any glue.  Half way through the first flight it had vibrated enough to polish the wood parts that they could slip.  I just put a few drops of thin CA, and it was fine.

In flight

In flight

The flights went great.  That park 250 has waaaaay more power than you need with a 7×6 APC Slo-fly prop  (which is the only prop I’ve tried).  The plane flies easily at 1/4 throttle.  At full throttle it gets very small very fast.  When flying slowly, it’s also very agile.  It’s possible to complete an entire circuit in 1/3 the length of the runway.

first landing

first landing

Even though it sports GIANT tires, it’s still easy to nose-over during landing in even short grass.  Given that it has almost no mass, no damage was sustained.

I give it 2 thumbs up!

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  1. #1 by Keith on June 12, 2011 - 9:26 am

    I love the “Park 250 mounted” photo — the lines resemble those of an old radial airplane engine. Very cool.

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