Mini Morph Marathon Part II: Mini-Trainer

by webbhm | November 23, 2014 | (6) Posted in Projects


Part I laid out the basic design principle of taking a basic fuselage (the Mini-Scount), a basic tail (Mini-Speedster) and a basic wing (Mini-Scout with simplification) and then adjusting the wing position by moving it up and down relative to the fuselage.  The Mini-Scout is a mid-wing, with my morphs being in other positions.  The Mini-Bip was an example of moving the wing down.  The Mini-Trainer is an example of moving the wing up.


It takes a bit of drawing-board work to find the wing position for the Mini-Trainer, basically copying the wing position and 'sliding' the position up till a line extending the rear wing angle intersects with the root of the tail.  After drawing in the wing and back line, I dropped a 45 degree line from the front of the wing to intersect with the front of the fuselage. This fuselage takes a bit more cutting than the simple 2.5 inch strip, but is not that far different. 

Warning: this drawing has a 'spoiler' of a future article.  It shows how the wing placement can 'slide' up and down for different placement.  The top pattern is the one used for the Mini-Trainer.

The fuselage parts were put together as a box construction.  Same basic shape as the Mini-Scout, but without the advantage of tabs and folds.  I only covered the back portion of the fuselage top, and the front; leaving open the area where the wing will be mounted.  In larger planes the wing would be attached with rubber bands, but being this small the wing is glued in place.

All further construction follows the basics explained in Part I and the Mini-Scount build.  The wing was made of two simple 6x11 rectangles, with my standard wing tip.  After bending and gluing the wing halves (using the Mini-Scout wedges to get the correct angle), I ran the middle edges of the wing over a piece of sandpaper about a dozen times to create the dihedral.  The halves were then glued together, again using the Mini-Scouts dihedral gauge.

There is plenty of room to put the battery inside the fuselage, but with my big fingers I find it easier to just stick it to the underside.

The wheels were something 'quick and dirty' so I could get flying.  In the future I plan to put some standard wheels on the plane, but the order for plane parts may take a while.  These wheels are simply slices of 'pool noodle' with a quarter section stuck in the hole and glued (be sure to use the 'cool' setting on the glue gun if you don't want them to melt).  They may not last very long, but the will last long enough for my test flights.


Looking at this wing and fuselage, a lot of other planes follow a similar pattern (ie Old Fogey).

The side profile of the Mini-Trainer is a bit big, making it more subject to wind (if you are flying outside).  One modification is to reduce the side profile by slicing off a portion of the bottom.  Another modification is to adjust the angle of attack (lowering the front edge).

Flight Characteristics

I was not certain about this design.  My initial flights tended to be crashes.  Adding throttle tended to nose up, stall then wing over and dive in.  I smashed a prop, but the plane showed little effects.  After I finally got it up and flying I killed the throttle to check the glide slope - rather than gliding it wanted to float down.  It was becoming evident that the CG was off, too tail heavy.  I moved the battery (.500ma 2 cell) forward about an inch and the CG was located almost exactly at the high point of the wing (about 2 inches back from the leading edge).  It was almost like a new plane, at half throttle it would slowly circle within the space of a ball diamond (the soccer field was busy, and though smaller, this was the only space I could fly).  I want to make a few more adjustements to CG and control surfaces, but it is shaping up into a nice little plane.


BabyBrit_FPV on November 27, 2014
I'm thrilled to see this post, Ive been working on a design for a Mini Cub and this article is now making me redesign the tail and elevator to be more scale to the original. Thank you so much for sharing and checkout my post on the forum for the MM jacCub!
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Mini Morph Marathon Part II: Mini-Trainer