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[Essai] Weasel TREK de Dream-Flight, l'aile volante ultime ?

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Introduction  Après une très longue attente suite à l'arrêt soudain de la fabrication de la Weasel EVO, essayée dans ces colonnes en 2009, la version revisitée est arrivée finalement début 2016. J'étais très excité d'essayer cette nouvelle Weasel TREK car j'avais vraiment craqué sur la première version. J'ai d'abord eu la Weasel EVO, puis plus récemment une Weasel Black Édition, ce qui me permettra de comparer. Et puis si les améliorations sont du même niveau que pour l'Alula TREK, alors cela promet ! C'est parti pour un essai de cette nouvelle  aile "Made in Californie" ! Aperçu du Kit  La Weasel TREK arrive dans un joli carton rectangulaire qui s'avère bien plus pratique pour ranger et transporter l'aile. La forme de la Weasel ne change pas beaucoup et reste certes moins élégante que l'Alula, plus massive, certaines mauvaises langues diront une esthétique de fer à repasser, mais si vous vous arrêtez là, alors vous passez à côté …

Digitech Angle & Throw Meter

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I continue my migration to digital tools !  I just received my Angle &Throw meter from digitech in Netherland, and designed by Daniel Maiorano. This device allows to mesure angle and travel in mm, as you can enter the chord of the surface, very smart !  It comes without user manual or mount. After thinking a bit, I finally just double taped a epoxy plate behind the case, and which stay on it, then I paper tape it. the case is 3D printed, and it features a small OLED screen, very crisp and with excellent contrast.
The use is very intuitive. First you fix it on the surface, then you power on with a 4.8 to 14V battery. Before to start calibration, you need to set the chord, by clicking on the +  or -. When ready you click on the "F" button, there is a 3 seconds countdown before to enter calibration and set the Zero position.  You can start measuring ! Overall, this is a nice device that allow to replicate settings with precision, I just regret that the chord has to be re-e…

Flying session in fresh air !

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Some fresh air and a nice flying session near Grenoble. No F3F as the slope was not suitable for it, but few nice aerobatics and overall relaxing flights in a beautiful scenery.

The photo album can be seen here

Towing

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Small visit to a local aeromodelling field where club members were doing towing in this nice and cool afternoon with a temperature around 13°. The opportunity to see nice flying machines up to 8 meters.

The photo album can be seen here: Photo Album

[Hints and Tips] Wiper dents and missing parts repair

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I found this epoxy sealant from UHU at Lidl for a very low price and it appears to be perfect to repair damages of wipers on the wings.

It looks like gray modeling clay. You mix it during few seconds before to apply it. then it cures in 10 minutes. It can be drilled, sanded, painted. Really convenient and with a very good result.
Approved :) !

[HOW TO] Calculate the CoG from the weight

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Given the number of questions I still receive :) , I see that the concept of measuring the CoG location by measuring the weight at the leading edge and X mm behind is not fully understood, so let's explain again with a real case, my Stribog CoG:

2 kitchen scales measure the weight of the plane, separated in my case by 293 mm. The first scale measure the weight at the vertical of the leading edge, the second one 293mm behind, so behind the trailing edge.
The sum of the 2 weight measured give the weight of the model. Now we apply the formula of a barycenter of a barrel that says: a x p = b x p'.


In other words, the if I measure p and p' , and also that I know the distance a+b (293mm in my case), so that b = 293 - a, I can easily calculate the CoG location.
So now, let's do it for real. My Stribog is placed on the device: I measure 1475gr at the leading edge, and 834gr at 293mm of the leadging edge. After entering the formula in Excel, it gives me a CoG located at 105.83…

CoG Machine

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I finally found the time last week-end to assemble my CoG Machine, made from 2 kitchen scales, some aluminium and 3D printed parts. The 2 scales are glued on a wood place using some cartridge sealant. Prior to that, I did a trapdoor below to access the batteries. The 3D printed support is also sealed on the scale plates so everything is fixed together.

Just as a reminder, as lots of people asked me how it works, just look at the drawing ont he right and extrapolate to obtain the formula giving the location of the CoG from the leading edge, knowing waht the scale measure at the vertical of the leading edge and what the second scale measure X cm behind.
The advantage of this method compared to the usual CG balance is the repeatability of the measure.


I know that, since my first post on Facebook, some CoG machines are in construction here and there ;) ! This is good to know !