Nostalgic for the Falcon 120? Is "Serpent" for those who love to build!

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Do you remember the legendary Falcon 120, the jet that started out as a propulsion engine and was later adapted to a turbine? It was an economical model (the first kits cost around £200) and flew reasonably well. It wasn't beautiful and didn't have many frills, but it was affordable for many beginners in the world of turbines. It's a shame that it's no longer on the market (I searched the entire web for days), except for a few rare boxes from private sellers asking exorbitant prices.
Well, while surfing the net, I came across a British website offering a kit similar to the Falcon 120, but with a wingspan of 195 cm and a length of 192 cm (excellent!). It is called “Serpent” and is made by Iad Model Design (https://www.iadmodeldesigns.co.uk/serpent.php) , owned by Iain Nicol, a very helpful person.
It is a well-made CNC/laser-cut wood/balsa kit, derived from a design from a few years ago, but completely revised and updated. The recommended motorisation ranges from a 45N to an 85N turbine, for an estimated model weight of between 5 and 6 kg. The kit (unusually) includes all the wood needed for assembly, including spars, strips, leading and trailing edges, balsa sheets for covering, reinforcements, etc. For the fuselage, the kit provides a single vacuum-formed laminated piece (very light), for which all the reinforcement frames, bases, landing gear supports, bayonet holder and carbon bayonet are provided, ready and cut to size for gluing. Retractable landing gear is not provided, but is available as an option with wheels and brakes; I installed a set from JP Hobby complete with legs and wheels with brakes.

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Well, I couldn't resist and ordered a kit, which was delivered to me after about ten days. The packaging is excellent and protects the contents well, despite being a medium-sized box. Opening the package and checking the wooden sheets, I immediately noticed the quality of the cut and the ease with which the various components come apart. I was surprised by the presence of all the necessary pieces already cut, including the balsa boards for the rudder covers, the moving parts, the servo compartments, etc. Iad also supplies the canopy, also moulded in epoxy. For those who want it, Iad also has complete landing gear and servo controls in its catalogue. In short, it is a decent kit that sells for £540, equivalent to about €620. It is a pity that this kit does not come with drawings or assembly instructions. This is not the first time I have built balsa kits, but I must admit that it was tiring having to spend a lot of time checking a series of images on the group dedicated to this jet. Furthermore, the photos are roughly grouped by assembly sections and in “random” order, but you need to pay attention and look carefully before gluing. I pointed this out to Nicol, but he couldn't give me an explanation. In my opinion, it wouldn't have been difficult to provide a printout of the drawing, even if not to scale, to avoid so many inconveniences. In any case, I recommend (but those who are already experts know this) assembling the various sections first and only gluing them when you are sure they are correct.
(To be continued)

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The assembly of this kit is aimed at model makers who have a minimum of experience in building pre-cut wooden kits, but I must say that, being only on my third experience, I realised that this kit is particularly accurate in the precision of the joints and the cutting of the pieces. To assemble everything, you need a few tools such as a sander, a mini drill, etc., as well as spirit levels and 90° squares for checking. In my workshop, I have a wide range of Proxxon accessories that I use for my work, and I must say that they have never caused me any problems. The great thing about these tools is that they come with a huge range of accessories of all kinds, perfect for building wooden/balsa wood kits. I have tried alternatives, but then I went back to buying Proxxon. This may sound like an advertisement, but since I now have a lot of tools at home, I can only emphasise their quality. Then again, everyone has their own preferences...

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The first thing to do is to divide the parts of the kit according to the various sections of the aircraft: tail, wings, central section, moving parts, fuselage and steering supports. And this is where the first problem arises: the laser-cut sheets are not divided into sections, but may contain parts for the wing, servo supports or spars with ribs of moving parts, as is the case with some sheets. This would not be a problem if all the parts were labelled with the name of the part they are going to build, but this is not the case. Others are printed with sequential numbers to be followed when assembling the wing or elevator, etc. Unfortunately, this kit does not even contain a drawing of the model with the various parts to be assembled, and I pointed this problem out to the manufacturer, Iad, but I received no response other than the advice to look at the photos on the Facebook group (https://www.facebook.com/groups/1350973201704574/). There are indeed many photos, but they are not enough to overcome some minor obstacles that may be encountered when assembling certain parts. A diagram is definitely essential for this kit, or at least it would be advisable to mark all the cut pieces with specific codes.
However, with a little care and by browsing through the hundreds of photos available, you can overcome any difficulties. Those who have already built similar kits will have an advantage, while novices will have to work harder. For assembling the various parts of the kit, I generally used Pattex vinyl glue and aliphatic glue, while for structural gluing I used two-component epoxy glue.
The fuselage of the kit is a single piece moulded in epoxy resin and fibreglass, and feels a little light to the touch. Before assembling the model, I reinforced the attachment points of the landing gear and wing with 160 g/m² carbon fabric to give it greater strength. The internal stringers and the front landing gear tower fit perfectly, while the hole in the fuselage for the landing gear to exit must be cut by the model maker; a plywood template is provided for this purpose, as for the wing landing gear bays. The front of the fuselage has a removable cone that allows access to a solid plywood base locked in place with the last fuselage frame, which will be used to house the batteries. All very functional. The central part of the wing is locked into the fuselage by means of a front joint on a frame and two nylon screws that lock onto a support glued into the fuselage.

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This flu is causing me a lot of problems, but we're slowly moving forward.

This kit has been designed and manufactured with the aim of ensuring ease of transport and speed of assembly in the field. The solution adopted by Nicol Iad was to create a central part of the wing that houses the landing gear and remains attached to the fuselage. At the ends of this part are the two spars, to which the two vertical rudders are glued, which support the horizontal stabiliser at the top. The fuselage, the central part of the wing and the rear part with the vertical and horizontal rudders remain permanently assembled; in the field, however, the two wing halves must be assembled, which are attached to the central section with carbon bayonets and reference pins. This allows the entire model to be transported in a car with reduced bulk and easily assembled in the field. However, in my opinion, attaching the two wing halves remains awkward, as it is done using a through bolt on each wing half, supported in the wing structure by a block of plywood locked into the spars and ribs at that point. To attach the wing halves, everything is assembled, the bayonet and bayonet holder are drilled at the same time, and the through bolt or screw is inserted. No problem, except that it is clear that once the bayonet has been removed and the wing taken off, the next time we assemble the wing halves, we will have to match the two holes by rotating the bayonet, which is not easy. Everyone here can find the solution they prefer.

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The rest of the assembly and finishing poses no problems (even the canopy, also made of fibreglass and epoxy resin, fits well to the fuselage, and the finish of the kit is a matter of personal taste. However, the simplest solution remains heat-shrink covering, which is quick and durable. It depends on your taste. The Serpent kit offers ample opportunities for customisation in both construction and electronics setup, but I must say that once assembled, it is a beautiful jet. Its flight characteristics should be good, thanks to a moderate wing loading, generous surface area and a good wing profile. The price of the kit is in the mid-range, but it is penalised somewhat by the fact that, at least in Italy, customs duties are applied to shipping, although these vary from country to country.
Now let's take a quick look at the electronics and motorization section. As mentioned at the beginning, this jet will be powered by a Kingtech K65 turbine, which is lightweight and provides sufficient (but not excessive) thrust to get the model airborne. Those who fly on grass runways may be penalized by the fact that, with a motor at its limit, they will need more takeoff space, but in flight they will still have sufficient thrust. I don't have an 80N at home, so I will install the K65.
Given the particular nature of the space available for the electronic and power supply components, I had the idea of printing a custom-made tank at home with my 3D printer that could be adapted to the space, with a capacity of about 2 liters, to which I coupled a 250cc Uat. While I was at it, I also printed the covers for the wing landing gear compartments so as not to leave any open spaces under the wings where the landing gear retracts.
For electronics, I have relied on Powerbox for many years now, and in recent years I have appreciated the particularly small and lightweight “Pioneer” control units, with dual power supply and dual Rx and complete telemetry for the voltage of the paired batteries. It has only one limitation, which is that it cannot regulate the output voltage for the servos because this control unit returns the same output voltage as the input voltage. It is obviously a more economical control unit, designed for those who do not need too many functions but simply want a reliable, easy-to-configure, lightweight, and small device.

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Two final thoughts to conclude this review. I found this kit particularly interesting in terms of the precision of the CNC cuts and the perfect fit of the joints; the kit is absolutely complete and requires no additional purchases, except for accessories such as hinges, connectors, components, etc. I have never seen such a complete kit. On the other hand, I cannot help but point out once again how, nowadays, it is possible to sell a jet kit without a single drawing and without even dividing (at least this much!) the parts that correspond to the same section of the model. It is really hard work to track everything down. And it is better to check three times before gluing!
The last question that naturally arises in a hobby sector such as model aircraft, where manufacturers compete to sell increasingly “ready to fly” models, is the following: is it worth going crazy to make something you can buy ready-made (and at little extra cost...)? My answer is yes, it's worth it if you are a model maker who loves to build, who has learned the art of model making from parents or grandparents who, 40 years ago, laboriously cut balsa wood and plywood by hand to make all the parts of the aircraft, which they then covered with paper and homemade paper stretchers made with trichloroethylene and polystyrene (...!).
So if you have this passion and want to spend this winter in the workshop building and are looking for a generously sized jet trainer, I think this model could be right for you. I repeat, you need patience because you have to proceed in small steps and without rushing. Use a good vinyl or aliphatic glue and give it time to harden well, savoring your progress little by little. You could also use cyanoacrylate to speed things up, but I don't recommend it (except for some non-structural parts) because it makes the joints rigid. But that's also the beauty of this hobby: you can achieve excellent results with different solutions.