SLINGSBY T31 TANDEM TUTOR 5th SCALE

[chris williams]

The wing is held flat whilst the first of the web plates are added. Once they are fitted, the sub spars can be added in front of them. (Main spar only)
Now the lower sheeting can be added to the D section, and then the wing placed upon its jigging supports and weighed down while the top sheeting is glued in place...

[Philkiteflyer]

After finalising the lower sheeting, attention moves to the nose. Big mistake here, as the lead screwed to F1 was entirely unnecessary, rendering the model nose- heavy later in the build process!

Now this is a subject that has always had me wondering . . pre-installed lead. Especially on a prototype.
Do you do any calculations of material weights and distribution before building to work out how much 'church roof' is needed to balance a glider while its still being built? ?
From your comments above I am guessing it is 'trial and error' and then edit the plan afterwards for the next guy/girl.

I would be interested to know what others do?

Cheers
Phillip C
New Zealand
(Sitting in my home office listening to the constant rain . . )

[chris williams]

Previous experience usually does the trick for me, but not this time....!

[chris williams]

Due to parsimonious nature of the D section, the T31 wing need extra diagonal supports to preserve the wing's rigidity... These are best added whilst the wing is held straight on the jigging supports

[chris williams]

2 lots of struts each side, so 2 lots of wing brackets...
Note: it's always important to leave the incidence peg for the second wing open until the wings can be properly lined up against each other before finalising...

[chris williams]

The struts are from 5mm carbon tube with 3mm threaded inserts at each end. Inverting the airframe and packing up the centre section 46mm allows for getting the correct length measurements . 3mm metal clevises at each end allows for plenty of adjustment to the dihedral as necessary...

[chris williams]

Plastic Bowden tube guide the rudder cables part way up the fuselage. The wings are retained at the centre with rubber bands and a strip of insulating tape on the upper surface only.
Then, it's time for the covering process...

[chris williams]

HK film used throughout, the only variation being Solartex over the centre section struts, which themselves were faired in with TE stock balsa. These struts, and any other areas, where film might peel off were instead rendered black with a marker pen.
i.e. wheel box, skids etc... (Spraygun not required)
Note lead under the tailplane to rehabilitate the cg....!
The servo hatches are covered with film patches

[chris williams]

Airframe completed, maiden-ready... (and a quick look at the full-size)

[chris williams]

My low expectations of the T31's performance were blown away once Aviation took place. Completely vice-free, and a delight to land, this model is also a complete tart in front of the camera...!

There is no formal plan, but I have tidied up the working drawings and can make them available to any interested parties...