How To - Hand Launch an X-UAV Mini Talon
© Mark Qvale - 2017
The Great CG Mystery Solved!
I get asked a lot about launching the X-UAV Mini Talon because for many, it has been a real challenge. The most common complaint is "the plane noses up and rolls left into the ground". This is commonly attributed to "Torque Roll" however this is a mis-conception. The cause is the CG is behind the CoT or center of thrust which causes a type of tip stall because there is not enough air speed for the control surfaces to be effective. The plane almost always rolls left because we almost always use a standard CCW tractor prop which does put a left torque into the airframe. So, the torque is there, just not the cause.
Starting sometime in 2016, X-UAV started sending a build sheet with the kits showing the CoG at 76mm. This is completely incorrect and X-UAV has confirmed it is an error on their part and they will "correct soon" (February 2017). Earlier Mini Talon build sheets as well as the earlier planes which came with CoG decals clearly show the CoG at either 55mm or 60mm from the leading edge at the wing root. My original MT had decals at 60mm and #2 had decals at 55mm.
Additionally, the current on-line manual (as of 18 January, 2017) from the makers of the plane, X-UAV, show the CoG to be at 55mm back from the leading edge. This makes some sense as at 55mm, the CG is a little forward where one would expect the starting CoG to be. You can see the current X-UAV manual at their link here:
To add to some of the confusion, there are many who claim putting the CoG on the servo wire exits (68mm) is the best position. I have tested this position with my 1650g MT#1 and while it does fly well, using this position did create a tendency to tip stall on launch if I did not throw it correctly, into the wind and very fast. It would also drop a wing into a recoverable spin while flying very slowly. Many others have posted they have crashed or nearly crashed on launch using this position at the servo wire exits. This is even more of an issue in dead air (no wind).
Having said all that, I strongly recommend starting first with the CoG position of 55mm to 60mm until you get everything sorted and you are well practiced at launching. Then start moving it back to where it suits your launching/flying style. Personally I like ~62mm.
As far as throwing the plane, there are many ways to do this and this short video shows my set-up and method. Remember, this is a starting point, you will need to determine the best CoG position for your particular set-up.
I have been asked quite a few times "Why not throw it up so it doesn't dip as much". The answer is simple, if you throw it straight and level it will pick up speed and get the wings & tail surfaces working MUCH faster. If you throw it at an "up" angle, it will not gain speed as quickly and almost always dip a lot more. Throwing it up also has the risk of tip stalling if it isn't thrown hard enough or powered enough and this almost always results in a crash.
18 January, 2017
Here are some images of build sheets and an email from X-UAV:
December 2015 Build Sheet
January 2017 Build Sheet
January 2017 Online Build Sheet
|From 6 February, 2017|
Facebook poster Jonathan D has found and provided another build sheet from a May 2017 purchase that has the CG 5mm farther forward than the recent online spec of 55mm! I wouldn't recommend this 50mm CG position as it will fly like a tank and be very difficult to trim-out.
Again, start at 55-60mm and adjust to your liking after you master launching.
|From May, 2017|