Wednesday, 1 June 2016

Mystic 40

This is Hanno Prettner's 1993 World Championship model - scaled down for a piped 40 or possibly a 60 sized 4 stroke,

It results in a model of about 56" span and hopefully quite light.

 The design was actually pulled together using DevFus for the Fuselage and Profili for the wing. This enabled me to get the shape of the formers exactly right without needing to guess or manually interpolate.

A very slender fuselage and surprisingly deep. Its not really obvious from the until the size of the fin and wing is considered.

A detailed build blog exists on the Model Flying Forum  which covers many of the constructional aspects of this model and will not be repeat here

The output from Profili and DevFus were combined into a single file and edited using DraftSight. The parts were transferred to DXF and sent Dylan at LaserCraft for laser cutting - Liteply and Birch Ply wing ribs and fuselage formers

So rather than repeat the build blog, just a few progress photos here:

Tailplane construction is quite simple, the trick is to select good quality light wood. Elevator hinges using Kevlar cloth which is what I tend to do nowadays

The fuel tank area and Firewall are assembled as a crutch and the fuselage built up around it

Fuselage construction is quite straightforward

Upper decking is 1/16" balsa sheet

Wing construction is traditional. Building tabs used to make sure the wing stays flat

Retracts are HK copies of e-Flite and a cheap MG996 servo used as the retract servo.

And a video of them working

Leading edge sheeting added and a dry fit of the model - looking OK :)

Next bits were the tuned pipe tunnel, ailerons wing tips and rudder

 Wing tips hollowed using a dremel and sanding drum after the external shaped had been roughly carved and sanded to shape. A lot more wood than that came out.

The lower fuselage was crafted using lite ply formers and soft balsa sides

 Rudder laminated from 3mm balsa. The fin cap has a 3mm lite ply base to help keep it nice and straight and importantly, add a lot of strength. Balsa on its own is just too fragile

Ailerons laminated from 5mm balsa sheet over the Kevlar hinge. The ends are capped with 3mm lite ply to maintain nice crisp edges

 The Canopy came from an old defunct model that lost its life when an aileron linkage broke..

And so far, it looks like this.

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