Trainer 40

Started by GuyOReilly, April 27, 2024, 02:38:00 PM

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Just started construction of a Trainer 40.
Downloaded the instruction manual from OuterZone :
This should be a fun and quick build.  ;D
There is no electric conversion instructions, so I will just wing-it. 
The plans include a top hatch already and a fuel tank bottom that will serve as the battery floor.
As for power, I was thinking a Eflite 25, but that may be a bit marginal, so probably will go for a 45.


I think a 25 or a 32 on 4S would be more than adequate.


Section A, steps 1 through 9 completed, the tail section is ready for covering.
The wing construction starts soon, but first I need to enlarge the holes in the ribs to fit servo leads and extensions.
@Michael I agree that a 25 or 30 size motor might be adequate on 3 cells.


Dry fitting the ribs.
The quality of this kit is impressive.
The spars and leading and the trailing edges are notched for a tight fit.
Only complaint so far is the inconsistent balsa density ranging from ultra light and flimsy (the trailing edge spar) to super hard and heavy (one sire of the elevator).
Enjoying the build process.


Wings well underway; however, they will be completed end of May.


I am impressed with the labelling of this Great Plane kit.
So easy to identify the parts.


Back from my European Vacation and jet lagged.
I decided to tackle the firewall and engine mount today.
Spent 2.5 hours looking for screws and drilling-out the retaining T-Nuts.
Happy with the results, need epoxy to dry before gluing to the fuselage side(s).
When the motor will be available, I will drill the engine mount accordingly.



Starting to look like an airplane.
I am still not happy about the wing centre section. 
I feel it needs a spar joiner, not only having both halves butt glued.

Frank v B


The butt glued wing is a feature of that vintage Great Planes Models kits.  The Kaos 40 pattern plane and the SuperSportster 40 had the same wing joints. 

When I built the SuperSportster 40 (low wing tail dragger) I did not like it either, cut a hole through the bottom of the wing and spliced in a piece of shaped 1x2 pine to catch wing ribs between the landing gear placements.  It became the landing gear mount as well. The buzz at the time was that the landing gear ripped out on a tough landing (my standard landing ;D).

See post 14 on the Polestar wing build thread when I added the 1x2 to the center section.

The fibreglass they use in the kit is significant weight and covers the entire center section.

If I were you, I would cut a slot behind or ahead of the main spar and slip in a piece of 1/8"(or thicker) plywood to span at least 2 ribs on each side of the center rib, glue it to the top and bottom spar and fibreglass it per plan. 

Great Planes kits were the best (flying and strength) in the late '80's and worked well as built per plan. The Sig kits were lighter (better balsa) but were more "builder's kits".

Belt and suspenders.
The choice is yours.


"Never trade luck for skill"


First spar reinforcement epoxied in place.
Should be dry in a day or two.


The supplied ailerons are 26" X 1" X 1/4".
These are not tapered, not anything like aileron stock; nor do I have the patience to shape these.
The plan is to replace the supplied sticks with 2" aileron stock.
Larger ailerons should provide added roll control authority.


Well, the ailerons are now 2 inches wide, this is much better IMHO.  ;)
Now should these be tapered or left square?!?
Pros and Cons:
  • Looks better if tapered.
  • More sturdy if square, less prone to breakage of the trailing edge.
  • More sanding and risk of being uneven if tapered.
  • Risk of flutter at high speed?? (it is a trainer)

Any expert opinion on the matter before I decide?   :-\

PS: the aileron tips will be rounded to match the contour of the wingtip.


Covering finished.
US markings are unusual for me, but I had these on hand.
Next on the agenda:
 - Servo mounting and adjustments
 - Motor installation (on order)
 - ESC installation (to be purchased when motor arrives)
 - Wheels - to be attached.
 - Control horns to be screwed-in.
 - Maiden Flight!