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Dave Smith Models Merlin Kit Review

By: Paul Oliver

This review is intended as a personal review by a modeller that may be of interest to fellow modellers, and therefore comments made are the opinions of the reviewer only.

I was first drawn to this aircraft when I saw it on Dave Smith Models stand At Sandown in 1999. It drew my attention because it was a fun fly model that differed from the run of the mill type in that it was a low wing - not a high wing model. I immediately liked the looks of this aircraft, and what with it's low show price resulted in me taking an additional kit box home with me from the show.

The model as mentioned earlier is a low wing fun fly model suitable for 0.25 - 0.40 cu in size engines. I had decided that I would fit either an MDS 28 or an OS40FS, as I had both available on the shelf in my modeller's den begging to be fitted to a model.


The Kit

So what do you get for your money? Well you get a box containing a substantially completed fuselage requiring only some construction work to complete, some polystyrene wing ribs and balsa/hardwood for constructing the wing and tail. You also get an ABS cowl, a clear canopy, and the wire for an undercarriage, and several sheets of A4 with the instructions, and no plan. Hang about! No plan that one normally expects is needed. You only need to construct a rudder, tailplane and elevators, and ailerons. The plan for these is printed on the A4 sheets, which you tape up as necessary, all parts were supplied well packaged to prevent risk of damage. I should mention at this stage that you can also get the kit with foam wings, but I felt that the weight might affect the performance. This is just a personal preference.

What other items are required to complete the kit, apart from covering material? A four channel radio control system with five servos. A pair of wheels, snakes or pushrods, engine and mount to suit.


Construction

Well to those people who are used to building their models nearly half the work is done for you. So that you don't think this is an ARTF kit I will start with the wing construction. This is of fairly conventional construction - except for the wing ribs. I have to admit that while familiar with the technique employed, it was the first time I had tried it. Essentially, polystyrene wing ribs are bonded to the main spars, and as construction progresses in the normal manner for a built up wing balsa capping strips are applied which impart a lot of strength to the rib. There was one other thing that you might not be used to. There is no plan used to construct the wing. It is all down to checking that everything is square! My only gripe with the wing was the quality of the wood for the wing sheeting. To my mind the wood was a little bit harder than I would personally have selected for use, but this might be to add strength to the wing. Whatever the reason, I was left with a strong but lightweight wing.

The ailerons were constructed from strip wood in much the same manner as most fun fly models, hinged and fitted temporarily to the wing.

At the same time as I built the ailerons, I also constructed the tailplane and elevators. These were built up from strip wood again in a fairly conventional manner, hinged and fitted temporarily.

On to the fuselage. There is not much to say about this as quite a bit of the work has already been done for you. You get a partially completed fuselage with the kit. The fuselage is made up of sheet sides with balsa covered foam top deckings. The front former needs to be marked up for your engine mount and hole drilled for the throttle snake, before the former is glued to the front of fuselage. At this stage I decided to fit the OS40FS. Strip longerons are glued to the inside of the fuselage sides along the bottom and the bottom is sheeted. I opted to fit a snake for the elevator control and closed loop system for the rudder and I installed the necessary hardware before sheeting the underside. The tail feathers were added and the wire undercarriage was bound together and soldered.


Covering and Finishing

The model was now ready for finishing. This is simply a job of applying some Solarfilm which I opted to use rather than Profilm, only to keep the weight down, though frankly Profilm would have been fine.

Radio installation is fairly straightforward. In my case I opted to use Futaba S3001 Servos for the rudder, elevator, and each aileron. A Futaba S148 Servo was used for the throttle, a Futaba 7 Channel PPM Receiver, and an Overlander 600mAh Sanyo nicad pack were also fitted. I found that to obtain the right C of G the nicad pack was situated immediately in front of the rudder and elevator servos (situated behind the cockpit, with the receiver in front of that, with the throttle servo in front of the receiver. The engine and undercarriage was fitted. Finally, the cowl and canopy were trimmed to size and fitted. I have to admit to opting to fit a free castering tail wheel and a pilot for the cockpit, along with a 6oz SLEC fuel tank. The completed model was extremely light. Performance could be interesting!


Flying

The finished model looked very nice and I have to admit to being eager to fly it. Come the day, and having conducted all the necessary pre flight checks, the model was fueled up and the engine started. I love the sound of a four stroke so was eager to get the model in the air. Having checked the mixture setting the model was eager to roll, even on a slow idle. The model was taxied to check that it tracked true, and to see what ground handling properties were like. This completed, the model faced into wind and the throttle opened up. After approximately twice the fuselage length, the Merlin leapt into the air and started climbing away nicely - sedately and not like a rocket ship. Somehow this seemed right. Having climbed to a safe height, I found that the model tracked true except that some down trim was required on the elevator. The model performed loops and rolls quite beautifully. Bunts were also easy. In fact the model was an absolute joy to fly and admire in flight. Inverted flight is as easy as normal flight, and hovering a joy.

The only criticism I had was that I felt that the rudder was not particularly authorative. The model would not hold knife edge for long, and the rudder did not appear to be too effective when entering and holding spins, though fine for stall turns. A slightly more rearward C of G should help cure this. Part of the problem might also be due to the reduced airspeed from using the four stroke.

After all of this fun it was time to land. You can really slow this model up so that a three pointer is possible from almost a hover. You could take off and land this model from an ironing board! The light weight really helps. Somehow, while the model lacked the top end speed of a two stroke powered model, the torque from a four stroke really made for a pleasant handling, very aerobatic model.


Summary

In case you have not already gathered I like this model very much. My first impressions of the kit were that there was nothing particularly outstanding to say "build me". Once completed the model's appearance imparts a yearning to admire and fly this model. Dave Smith's experience in model design is evident in designing a model that performs well. I cannot get enough of flying it.

I have let other members of my club fly this model, and all like the Merlin's flying characteristics. I was slightly sceptical about some of the choice of wood used, but these concerns come to nothing when the model takes to the air. Well done Dave Smith Models for producing such a nice model. I have had many flights with it now, and the model still appeals to me as much as when I first flew it.

Likes:
  • Flying performance.
  • Light weight of the model through good design.
  • The fact that this is not a typical runs of the mill fun fly model.
  • Partially built fuselage that is clearly nice and true.
  • Kit parts were well packaged to protect from damage - a nice touch.
Dislikes:
  • I am slightly sceptical of some of the wood selected for the wing and fuselage, though this is not borne out by the end result.
  • The instructions/'plan' are what one would usually expect of a cottage industry kit of ten years ago, and not necessarily expected in a modern kit today, but only in terms of presentation. The instructions themselves were quite adequate.

I feel that this model could make a good second model, particularly if flown with reduced throws. It makes for a good Sunday morning, afternoon, or evening model. It will provide many hours of enjoyment, and also be competitive at club competitions. If you want a fun fly model that is different to the usual high wing jobs, then I would recommend the Merlin. I think I had better put the gear back on charge now ready for yet another session - this after two years of flying!

Paul Oliver