Almost completed Mythos (missing wheel spats, undercarriage fairings and decals)
I recently built a SebArt Mythos 30E pattern trainer from the ARTF kit. Here are my observations about the kit. It’s been a long time (about 30 years) since I last built balsa aircraft (I used to scratch build control line models), so please take this as the experience of a new builder. I’m sure that someone with more experience than me might have a different opinion.
Packaging – 5/5
The ARTF kit is supplied in a very attractive yet sturdy box, with all components protectively wrapped and well secured inside the box. Provided this display box is shipped inside a larger box with some polystyrene or similar packing material, it should withstand the rigors of transport.
Design – 8/10
I love the looks, and the yellow/black/red colour scheme should give good visibility and distinction between normal and inverted flight.
For the most part there is a good balance between strength and weight. The undercarriage appears sturdy and the area at the bottom of the fuselage where it is attached is fully sheeted and should withstand less-than-perfect landings.
I couldn’t achieve the recommended ±45° rudder deflection because the angled cutouts on the elevators that are intended to allow space for the rudder start too late – even with the horizontal stabiliser mounted as far forward as it can go and minial elevator hinge gap, the elevator still prevents the rudder from moving more than about ±30°. This should be fine for pattern type flying, but may be an issue for 3D.
I would have liked the servo pockets should be slightly larger to fit the 17g servos specified in the manual for the aircraft – the Savox SH-0255s that I used were about 1mm or so too long for the pre-cut pockets, so I had to file them out. Also, the fuselage at the rear of the rudder servo is not very strong, so be very careful not to apply any force to this area when seating the servos (don’t ask me how I know). Some hardwood reinforcement in this area would not go amiss.
I like the canopy attachment and latching system. However I do feel that the front tongue of the canopy, where it hooks onto the firewall, could be made of a stronger material. Even a slight deflection of the canopy before it’s fully disengaged can crack it.
Other than this, and a few manufacturing issues noted below, the model went together quite easily. It was the first balsa model I’ve built in quite a while, so I took my time and it ended up taking me two full days to complete.
Instructions – 4/5
The supplied instructions are very good, much better than I have seen with most ARTF kits. However in some places additional information would have been useful – for example, which fasteners to use for some stages.
The instructions specify that two 400mm servo extension cables are required for the rudder and elevator servos, but I found that, even with the receiver mounted right at the back of the accessible compartment under the canopy, 400mm extensions were insufficient and 600mm extensions were required. I also needed two 150mm extensions that are not mentioned in the instructions for the servo leads from the ailerons.
The list of required tools is also not perfect. For example, it specifies super-thin CA, normal CA and 5-minute epoxy adhesives, but the only adhesives shown in the step by step instructions are super-thin CA and silicon glue, which is not listed! I alternated between normal and thin CA depending on the application, but never did figure out where I was supposed to use the 5-minute epoxy! Rubbing alcohol also is listed, but I haven’t figured out yet what to do with it.
And while the instructions specify that either 2500 or 3300 3S batteries can be used, I found that even with a 3300 3S, the battery has to be mounted as far forward as it can go (only about 5mm behind the motor) in order to get the Centre of Gravity to the recommended position for general aerobatic flying, 130mm behind the leading edge. I doubt whether it would be possible to balance the aircraft with a 2500 3S pack, except by adding weight to the nose (in which case one might as well add it to the battery and get longer flight times in return). Admittedly, I was using a non-standard motor and ESC, which might have affected the C of G somewhat. However the total weight of my motor and ESC is so close to the recommended components (234g compared to 231g for the recommended Hacker parts) that I don’t see this being a significant factor.
Kit Quality – 7/10
I’ve actually built two examples, and while there were some problems (detailed below) with the first one, the second was much better (except for the tabs on the undercarriage fairings). The first was 6/10 the second 8/10 so I’ll average it at 7/10.
In general the quality is good, and the covering is well applied. However, I found the following manufacturing issues in my kit:-
- Slots for the CA hinges were not cut to the correct depth and had to be re-cut using a craft knife.
- In some cases, the slots did not line up correctly between the control surface and the fixed surface to which it was attached, necessitating more serious surgery.
- One of the collars used to mount the rear wheel was missing. I made up a substitute using a piece of stand-off and some heat-shrink tubing.
- The slot in the fuselage where the horizontal stabilizer fits was a bit too narrow in places, and not profiled exactly the same as the stabilizer, making it difficult to get the stabilizer seated properly.
- The tabs on the undercarriage fairings were out of alignments with the slots in the fuselage that they are supposed to hook into. I had to cut a few mm off each tab to allow them to engage when the fairings were aligned with the undercarriage.
- The fairing at the back of the wings was about 10mm shorter than on the other wing see picture below). This is purely decorative, and should not affect flight performance. However it is quite noticable when the model is assembled since the short fairing reveals an uncovered portion of the fuselage where the wing attaches. The faulty fairing is neatly covered with Oracover, so this is a manufacturing defect, not transit damage.
The rear fairing on one wing was shorter than on the other
Support – 3/10
I’ve sent two queries to SebArt – one before I purchased, requesting some additional information which was promptly answered. I sent the other ten days ago to report the missing collar for the tail wheel and the short wing fairing but have not yet received any response. I’ve sent another email and will update this rating depending on whether (and when) I receive a response, and how helpful it is!
I’ve received no response from SebArt despite sending a reminder.
Flight – 10/10
I’m not qualified to judge the flying characteristics of a Pattern aircraft, so you’ll have to take this one with a pinch of salt. However two club instructors, both of whom are experienced F3A/IMAC pilots, have flown it and agree that it flies “just like a pattern ship”. From my side I can say that she’s very direct, goes where you point her, and doesn’t seem to have any vices. There’s no wing drop on stall, and only a touch of forward pressure is required to maintain inverted flight. She slows down nicely on landing (some camber flap helps), but still lands faster than a trainer. No complaints!
Overall – 74%
It’s a well thought out and packaged ARTF kit for a lovely aircraft, marred by inconsistent manufacturing quality and inadequate support. The instructions are generally excellent but do have some errors that should be corrected.
Build Tips
- Install the elevator and rudder servos and cabling before you install the horizontal stabiliser. This makes it much easier to adjust the servo cutout size if required (because you can support the inside of the fuselage while working) and to route the servo extension cables (because you can get at them from both sides). I also recommend installing the landing gear legs (although not necessarily the wheels and spats) before the horizontal stabiliser. That way the fuselage can support itself upright while you are rigging the stabiliser.
- To cut the vent holes on the bottom of the fuselage, turn the aircraft upside-down in a darkened room and put a head torch inside the fuselage shining upwards below the area of the vent holes. This will allow you to see the partial cuts that have been made at the factory through the oracover. Cut around the outline through the bottom of the fuselage.