1/3 Scale T21 by Jilles Smits

Let us all watch your new project progress.
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Peter Balcombe
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1/3 Scale T21 by Jilles Smits

Post by Peter Balcombe » 25 Jan 2016, 12:59

Just started the test build of this large woodie from Jilles Smits.
As for the Bocian built last year, the laser cut short kit has been provided by Cliff Evans, with many ply parts which appear to slot together very nicely.
As workbench space is currently a bit limited, owing to a few jobs still to finish on my current Olympia (VV401) build, I am starting with the tail feathers. Having said that, the tailplane spans 1.2m!!

First shot shows the tailplane and both elevator spar assemblies which comprise ply parts either side of 4mm balsa. The next shot shows the first elevator assembly once the ribs & T/E have been added, with the 2nd elevator partially assembled.
Attachments
Tail spars.JPG
Tail spar assemblies
Elevator Framework.JPG
Elevator framework

Jilles
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Re: 1/3 Scale T21 by Jilles Smits

Post by Jilles » 27 Jan 2016, 01:03

Those laminated spars from balsa with plywood liners are a weight saving effort.
I learnt this form my early Goevier model built from somebody else's drawings where even the fuse formers are made like that.
It take a bit more building time but is worth the effort on a short nosed design like the T21
every extra gram at the tail is 6 gram more lead in the nose.

spike spencer
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Re: 1/3 Scale T21 by Jilles Smits

Post by spike spencer » 27 Jan 2016, 06:33

Nice one, Peter. That is going to be an enormous thermal-sniffer - but, if its performance is Scale, don't be tempted to get too far downwind !!

Ply/Balsa/Ply sandwich is a great material. I have used it several times on models of all sizes. The joy is that you can make any thickness you want and it responds well to all cutting methods (especially the laser). 0.4mm/3mm/0.4mm for small electric models to 1.5mm/6mm/1.5mm or even larger. The easiest way I have found to produce it has been to make up sheets of 6" wide balsa by the usual tape and glue method, then after that glue has cured and the joint sanded to clear any nibs, spread glue over the whole area and pop the lot into a vacuum bag for a couple of hours. This ensures intimate contact across the whole sheet while curing.

I have used both aliphatic and PU glues for these wide sheets, both easy to spread and will cure quite quickly. Neither type has yet failed on me. I keep finding and using old offcuts from my scrap box. :)
Spike S.

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Cliff Evans
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Re: 1/3 Scale T21 by Jilles Smits

Post by Cliff Evans » 27 Jan 2016, 08:54

I have had three T21's over the years, two 1/4 scale, and one 1/3.5 scale, both from Chris Williams plan. both have been excellent models. I asked Jilles to design this for me @ 1/3 scale because I think it will be even better again. Yes it is big, but I cannot wait to fly her and i am very lucky that one of the best builders I know is building it for me!

Jilles
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Re: 1/3 Scale T21 by Jilles Smits

Post by Jilles » 27 Jan 2016, 21:59

Your are lucky to get 6" wide balsa sheets these days here in Australia
I was informed by my supplier that because balsa is now all plantation grown they do not wait until the trees are big enough to cut 6" wide sheets.
However with the ply/balsa/ply construction it does not matter if you have a (glued) butt joined in the balsa

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Peter Balcombe
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Re: 1/3 Scale T21 by Jilles Smits

Post by Peter Balcombe » 29 Jan 2016, 14:33

Rudder framework assembled (3 diagonal ribs still to be fitted).
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image.jpeg
Rudder framework less diagonals

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Peter Balcombe
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Re: 1/3 Scale T21 by Jilles Smits

Post by Peter Balcombe » 30 Jan 2016, 14:56

Tailplane centre section assembly built and servos fitted.
Photo shows underside of the assembly with the 2 Turnigy 225MG elevator servos used in place of Jilles' suggested A55H types.
The large circular hole is where the fuselage mating connector goes.
This assembly will now be glued onto the front of the previously built spar assembly prior to adding ribs & false L/E pieces.
Attachments
image.jpeg
Tailplane centre assembly

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Peter Balcombe
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Re: 1/3 Scale T21 by Jilles Smits

Post by Peter Balcombe » 31 Jan 2016, 08:10

Tailplane structure now completed.
The parts are going together really quickly.
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image.jpg

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Jason Griffiths
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Re: 1/3 Scale T21 by Jilles Smits

Post by Jason Griffiths » 31 Jan 2016, 13:30

Looking very nice Peter, looks like you are doing a excellent job as always :D
Thanks JG

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Cliff Evans
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Re: 1/3 Scale T21 by Jilles Smits

Post by Cliff Evans » 31 Jan 2016, 14:05

Have ordered the hinges Peter.

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