Model Flight – Page 3 – Frédéric Zamit

New Construction Report: Thermy 4

In March 2019 I happened onto an issue of the FMT, which included the first part of the diagrams for the Thermy 4. Right away, I knew: That’s what I’ve been looking for!

Thermy 4 with its constructor, Wolfgang Werlich.

The model incorporates everything what I’ve wished for: great wingspan (4 metres), take-off weight below 5 kilograms so it’s legal to fly outside of model aerodromes, flaps and an electric motor, enough space for own, further ideas.

Now, after two years of wavering and brooding, it’s finally on. With this new construction report I will try and document my attempt to build my own, larger sailplane.

Joyrider: Maiden Flight

And up into the air she goes!

After the first Center-of-Gravity tests my expectations have been thoroughly adjusted. I have to admit, at the beginning of this project I didn’t waste a thought on a possible failure. Meanwhile, the Maiden flight has become some sort of obstacle to me.

During the last weeks I’ve tried to accomodate weather, family and interested friends while taking patience and easing my doubts. That piled up too high: now or never!

A short remark: My wife thankfully took some video footage. However my PC has quit service, so I can’t postprocess. I will hand in the videos as soon as a new PC is at hand. Meanwhile, some still images will have to do.

Joyrider: Setbacks and Corrections

After a failed center-of-gravity test.

Finishing the covering was another milestone for me and I was very confident that the maiden flight would turn out just fine.
Then the first complete assembly came along and with it some new challenges. Namely undercarriage and center of gravity.

New Project: Aerial Footage

The EasyGlider in its element.

Alright, you got me: I’m talking about more than just aerial photography, but about footage made from the ground, too. But first things first.

As I’ve already outlined, I’m an active R/C pilot again since august 2018 and I’ve started to scratch-build a biplane in 2019, too. I ‘ve managed to post about the latter over the last few months and I do hope that some readers had fun reading those posts and maybe could even learn something useful from it.

However, the flying season is about to kick off in earnest. Of course, I want to fly and at the latest after the biplane is finished, I (hopefully!) won’t spend much time in the workshop. So what to post about here?

Joyrider: Covering

The upper wing's mounting, the undercarriage's mounting and the seatback are finished.

After the details are finished I can finally focus on the covering. Some model builders seem to regard covering as an irksome work and necesarry evil, but I actually enjoy it. To me it’s like a metamorphosis: the bare framing of the aicraft, as pretty as it is, equals a caterpillar, which is yet to become a butterfly.

Nonetheless it’s a lot of work all the more if one wants to get a creases-free result. In the process, I didn’t manage to take a lot of pictures, but I’d like to give an example and point out some crucial points.

Joyrider: Last Details

Upper and lower wing are now linked with each other.

By finishing the linkage the out-fitting has come to and end an I can take care of the last details. Those cover two areas: the fuselage and the wings.

The fuselage needs a couple of maintenance hatches in order to easily gain access to the drive unit, and the tailplane’s servos and fixture. The fuselages’ belly needs to get reinforced, too. And last but not least I’d like to add some details to the nose.

The wings need an additional strutting in order to stabilize the lower wings. And it will surely add to the good looks.

Joyrider: Linkage

The ailerons' linkage is finished.

As soon as the tailplane’s servos fitting-out was done I busied myself with the linkage. To start off with, I made a few errors which had to be corrected. I will describe those errors as well as the solutions, so perhaps somebody can learn from my mistakes.

Since I’m not too sure what forces I will have to account for, I’m erring on the safe side. At any rate, I reproduced the linkage used with the Easy Glider and chose a combination of 1 mm steel rod, 2-to-1 mm and 3-to-2 mm bowden tubes.

Joyrider: Fitting the Servos

The servos are fixed in place.

Fitting the engine has sent my motivation soaring, so to speak. So I launched myself at fiting the servos.

Alas, I soon realized that my “planless” construction made my life a tad more difficult. In order to soundly fit the servos, the fuselage has to be reinforced and strutted. I had partially anticipated this and thus constructed the belly with very few slats. Nevertheless I’ve come to realize that one’s way better off if the servo mounting’s fixture is built into the fuselage from the get-go.

Joyrider: Fitting the Engine

The motor is mounted.

By assembling the tailplane the construction is finally finished, so now it’s out-fitting the model. As a matter of fact that’s already started since I fitted the aileron servos while building the upper wing.

I’m going to work my way through the fuselage from nose to tail. So today’s topic is set: the engine has to be fitted.

Joyrider: Tailplane Assembly

Construction is finished.

Finishing the vertical stabilizer only leaves the tailplane’s assembly. Here, three important objectives have to be met: the horizontal stabilizer must be in parallel to the long axis, so must the vertical stabilizer, and the vertical stabilizer has to be at right angles to the horizontal stabilizer.

The most important contribution to the right angles is provided by clean, perpendicular cuts, which I can achieve easily thanks to my table saw. In order to further stabilize this orientation, I’ve constructed two guides from balsa wood and sanded them into a streamlined shape.