Review of the Durafly Dynamic S Performance Glider

Review of the Durafly Dynamic S V-tailed powered glider

Two of us, Ultramicrobe (Patrick) and Chadrat (Chad) recently bought a pair of Durafly Dynamic S and decided to give it a formal review. 

Below you can find the stock specs, suggested upgrades, and also a review of flight characteristics and two flight videos. The first video is Chad doing some awesome slope soaring at Arthur’s Seat outside Edinburgh. The second video has both Patrick and Chad flying together at a flat field, and includes on board and from the ground movies, as well as great footage of a massive, full-speed, mid-air collision that ended our review. Check out the movie to see who won: Patrick or Chad?

Video 1, Awesome movie Chad made of sloping in Scotland on Boxing Day, with great low passes

Video 2, on-board cameras with massive mid-air crach

When we were looking into this, Chad pointed out that the Dynamic is a knockoff of a Multiplex Blizzard, and during the writing of this review, we also discovered that David Windestål wrote a review of the Blizzard on his RC Explorer site (http://rcexplorer.se/blog/2009/05/multiplex-blizzard-review/). His review is very similar to our experience with the Dynamic, suggesting the planes are very closely matched. This makes sense since Multiplex planes tend to be amazingly well designed. The Dynamic seems to fly a lot like the Blizzard, but is much simpler to assemble and get in the air. Whether it is as durable is hard to say, but the Dynamic is certainly tough enough. 

 
First the specs. 

The out of the box specs for the PNP version are as follows:

Wingspan: 1560mm
Length: 1010mm
Wing Area: 21dm2
Wing Load: 42.9g/dm2
Flying Weight: 900g
Servo: 9g x 4
ESC: 30A w/BEC
Motor: 35mm 920kv Brushless Outrunner
Prop: 12x6.5 Folding

Price: US $118.00

Suggested Battery: 3S 2200mAh

Ease of Build.

Unlike the Blizzard, The Dynamic S is quite a simple build. The motor, prop, and electronics are pre-installed and the ESC and battery compartment is easy to access. The build is all bolts and no glue. The 2-servo V-tail and wings bolt into place with plastic covers and are removable for storage - it could go back in the box if need be. It lacks the Blizzards integrated servo connections on the wings, so you need to hook them all up before putting the wing on (they are inaccessible without removing the wing (although you can pull the receiver out through the battery hatch, it is just doable). Overall, the build took about 30 minutes without modifications.

Plastic bolt-on wing mount. The wings are removable and separate into two pieces connected by square CF tube.

Plastic bolt-on tail mount - hold the V-tail in shape and servos in place.  

Essential modifications and reinforcements. 

The performance of this plane out of the box is excellent, so there are no essential upgrades. Chad’s prop was broken out of the box, so he flies with a carbon fiber folding prop and an Aluminum spinner, and replaced the ESC with a 45A. Patrick’s is stock. 

We do, however, recommend some essential but simple reinforcements. The spinner is plastic and therefore liable to crack (this plane lands hot), so either replace it or keep a spare handy (the spinner and prop together is $6). Most importantly, we found the fuselage was weak directly in front of and behind the wing (see pictures). Both our planes have a solid skin of extreme packing tape from the nose right back to at least 2cm behind the trailing edge of the wing. Patrick’s also has chopsticks glued into the inside of the fuselage (which means the battery slides in sideways and is a tight fit). Speaking of tight fit, be careful the wires do not get pushed into the motor, since it can strip the insulation off as it spins. Also, to give the tail boom added stiffness, it is totally covered in regular packing tape. The top and bottom of the leading edge of the wings also have a single strip of packing tape (very useful for high speed collisions, as you will see).

Typical break - from Boxing Day, Scotland

Best to reinforce the fuselage around the wings really well. 

Skewers or chop sticks in the fuselage is also not a bad idea. 

Coloured tape on the wings to distinguish bottom and top is also very important - this plane goes fast, so we find very distinct patterns are important. Patrick’s has bold black stripes on the bottom and red tips on the top. Chads has purple. Both work well. The stock stickers were binned. 

Big Black Stripes - wing bottom tape really helps keep an eye on it because this plane has a slim profile. 

Take off.

Take off with high throttle and a solid throw with some up. It is so powerful but so steady it takes off easily and does not torque much. 

Flight characteristics. 

The manual shows the COG, and this is spot on. With our modifications, this is achieved by pushing a 2200 mAh battery as far back in the compartment as possible (it is a tight fit). A small camera (e.g. mobius) at the COG makes no notable difference to the way it flies.

This plane likes to go fast. it climbs vertical on full throttle, and flies perfectly well under throttle. The transition to gliding is surprisingly easy, even sudden transitions from full throttle to gliding - no sudden stalls or nose-dives as long as you level off before killing the throttle. The gliding characteristics are quite forgiving. Low speed turns can lead to tip-stalls (as with the Blizzard), and recovery is kind of slow, so be careful near the ground at low speed. 

Obviously this plane is great for slope soaring. Flying without a slope is also quite a lot of fun. You can run the whole range from easy gliding in slow circuits to hair-raising high-speed dives (see the movie for some of the latter). Recovery from dives is also fun, with a bit of speed you can do nice loops and rolls and basic aerobatics. Its wind penetration is amazing, although you might also expect this with such a profile. On windy days it is a great choice since it barely changes the flight characteristics. 

We noted that at really high speeds the ailerons can lock up - we think they are flexing rather than moving the whole control surface, despite the fact they have stock carbon reinforcements. In this event, simply pull up as the V-tail does not lock at any speed we have experienced. As soon as you pull back you regain control.  

Flight times with a 2200 3S are about 15 minutes when using a lot of throttle to climb frequently and dive, and very long if you are getting any real lift. 

Landing.

The Dynamic needs a bit of space to land because it cuts through the air so well it takes a bit of time to slow it down. We programmed flapperons in both ours, and it made no detectible difference. Have not tried spoilerons, but that is the next logical step. So to land give yourself lots of space, do some slow turns and come in for a nice long straight glide with lots of down elevator to keep a gradual descent into the grass, expect a little bump of lift just off the ground, and keep the wingtips up. 

Crashing. 

As noted above, the fuselage around the wings can be a weak point, but the EPO is pretty tough. In normal use it holds up well, even to pretty bad landings. We saw a couple exceptionally bad crashes and so can comment on them as well. In a sloping incident that had Chad crashing into a rock wall (see the slope movie). In the mid-air collision (see the other movie), Patrick’s glider was in a pretty steep dive and going really fast and hit Chad obliquely from above. It ran across the wing and chopped the tail boom right off, leading to a catastrophic failure. The fuse broke into three in the air and the main piece came down hard, with the nose ultimately getting buried about 5cm into the soil. This force split the wing joints, but the front end held up well and the wings were reparable. The fuse was a right off but only because of the in-air damage. 

Chad vs. Patrick - VOTE for who you think won in the comments section!

Overall - Two thumbs up 

The Dynamic S is a really exciting plane to fly. It is well designed (which is to say the Blizzard is well designed and this is true to that design), easy to build, tough, relatively easy to fix. It is surprisingly versatile, great for windy days, but needs some space to fly and especially land safely.