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Showing posts from February, 2017

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 !




Some very interresting new products from www.servorahmen.de

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Servorahmen.de has been the first company to introduce on the market servo frames years ago, covering almost all model of wings servo, but not only.
It is nice to see that they are following the LDS trend and adapting their products to customer needs.  Here are few new products I received from Florian:

- MKS HV6130 servo IDS frame: The pocket includes a new specialized frame for the recent and great servo HV6130 from MKS. The frame features an external counter bearing, and 2 fixing position. I noticed that this frame can host the HBL6625mini or the DS6125mini. The frame is provided with a set of 4 servo head, with different axis distance covering the various needs (ailerons, flaps, etc ...). Then a very interresting set of plastic arms with different length from 48mm to 81mm so you can solve easily any installation whatever the position of the servo from the control surface. The material used for the control arms includes carbon (Carbon fiber reinforced polymer), so are very rigid.
- …

First flight of 2017 !

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I finally exited from hibernation and had did my first flight of 2017. Past weeks were very cold with no wind so it was nearly impossible to fly. This time, on a slope near my home place, I had good weather, some south wind and 10°.

I flew my Stribog with 900gr of ballast. After 3 months without touching gimbal sticks, I'm happy to see that I still know how to pilot. Finally it is like bike, once learned you never forget :) ! This afternoon, I though also I could see the "death star" , but it was only the moon ;)