Friday, 31 January 2014

Flying the Merlin

Been really frustrating not been able to get much stick time to work as closely on the Merlin setup as I would normally like with a glider, but after the first couple of outings not on the greatest of slope this is what I have found so far.

The Merlin has got very benign characteristics and so far hasn't shown any bad habits. One of the first things I always do with a model is to try and find its limits and to get the Merlin out of shape isn't easy. The wing tips are quite a thick cord which is probably one of the main factors in its very stable flight characteristics.

It was very settled flying reversals but equally comfortable and very easy to fly EM and maintained or increased speed during each leg when conditions were consistent.

The Merlin as standard with the current supplied fuzz ballast tube can take 1.2kg ballast. There is certainly room to fit a larger diameter tube to gain more weight, but the other option I am currently looking into is adding ballast boxes to the wings.

I flew the model in 10 - 12m\s and it took full ballast comfortably. With the wing area it has room for plenty more for the bigger conditions.

Overall so far I would say the model is an excellent beginner to intermediate fliers model that could be used confidently for racing or sport flying. Although the wing tips have a thicker cord than I would personally like, I have already stated this provides a great stable model. It still maintains a good straight line speed combined with great turning ability retaining its energy, which are two main factors for racing.

The setup I have 3 modes configured as follows:

CoG 100mm

All measurements are taken between the Aileron and flap.

Normal Mode: 2mm camber

Measurements in degrees

Aileron Up: 17.5
Aileron Down: 10
Elevator Up: 6
Elevator down: 6

Rudder all modes 7.5

Pump Mode: 1mm Camber

Aileron Up: 17.5
Aileron Down: 12.5
Flap Up: 10
Flap down: 7.5
Elevator Up: 6
Elevator down: 6

Speed Mode: Aileron level with wing tip and align flaps (flap should be level with fuzz fairing)

Aileron Up: 15
Aileron Down: 12.5
Flap Up: 5
Flap Down: 5
Elevator Up: 5
Elevator Down 6
Snap: 5 set on a curve at 75% 2.5

I also have Camber set on a switch for Normal and Pump which is only used for launch 3 degrees and 5 degrees. 5 degrees is rarely used if ever. when going into speed mode these setting along with butterfly/crow are disabled.

Butterfly / Crow:

Aileron up: 12.5
flaps down: 55
elevator down: 11

Merlin Build

Finally the Merlin build is finished and I have managed to find sometime to fly the glider. Before I get onto the flying characteristics I will run through some of the key points in the build, which was very straight forward.

For the servo tray to make it easy to fix in place I formed a mold as part of the tray to hold the ballast tube. Once the tray was secured in the correct position it was easy to glue the ballast tube in the correct position in the fuzz at the correct CoG point.

Once I completed the Tray and Ballast tube I moved onto the tail area. I made a simple jig to bend the brass tubing to the correct lengths and angles in prep to secure into the tails as per the pictures. Make sure you run some tape along the hinge line to protect it from the epoxy :

Once the brass tubing was in place I cut it to length and soldered the ball joints in place:

And finally the tray fitted out:

Important Note:

On the ailerons and flaps makes sure you lay some fiberglass mat over the brass linkages for extra strength.