The Probuild Shadow

Which Kit?
Mid way into the 2000 season and feeling a little disheartened with the flight performance of my current four stroke model, I decided to build a second model. After booking a building slot with Phil Williams of Probuild, the search was on to find a suitable kit, one which would suit my needs as a GBR/CAA Standard Class Pilot. The aircraft must be easy to fly and need very little or no trimming, have good looks and be capable of taking me through all the Classes. Above all the aircraft must be built as light as possible using modern building techniques, without sacrificing strength.

After spending quite sometime looking around at what was available, namely ZN and PL kits (I quite fancied the PL Smaragd) I felt that my ability did not warrant these high tech, very desirable aircraft. After several phone calls to Phil, I decided to go for the Probuild Shadow. The Shadow is an improved version of the Desafio-S with plug-in wings and tail; it is a well-proven design and flies very well with little or no trimming needed!
There were a number of reasons why I made this choice in view of what I could of built that was within my budget. Firstly, I was impressed with the Desafio-S. Secondly, the flying characteristics for this aircraft are by all reports very good and it needs little or no trimming. Thirdly, I could use my YS 120AC, which would allow me to use a recently purchased second hand YS 140 FZ in my existing model.
I purchased the Deluxe Kit, which included the wings and tail skinned in contest grade balsa, vac bagged with spar system fitted. Ailerons / Elevators cut out and hinged with kevlar. Retracts and servo wells cut out to suit the ZN boxes.

The Kit
On first inspection the fuselage mouldings were of good quality and all flying surfaces were well finished off in contest grade balsa. I was particularly impressed with the wings and tail plane. The Leading edges and trailing edges including wing tips have a carbon fibre layer sandwiched along these edges to protect against the inevitable knocks and dings. The rudder was pre sanded and again it was also sandwiched with carbon fibre.

I have never seen this done before and I think it is well worth the extra time and cost it takes to produce. The tail plane came fitted with the Gator spar system and the wings came with the tube holes cut in to the wing ready to accept the phenolic tubes. I had opted for a carbon fibre end grain F1 and carbon fibre/nomex panels, which are extremely light and strong. The Engine mount that was to be used is the renowned "Hyde mount". Fit and forget as it was explained to me.
Having talked to Phil Williams at great length about the equipment and options available, I decided I would use two Volz Micro Maxx servos mounted in the tail halves in place of the conventional single servo set-up. The reasoning behind this decision was two fold. Firstly, having two servos on the elevator gives some degree redundancy over the standard single servo and carbon rod set-up and by using the Volz servo's there is also a weight advantage of 20grams (3/4oz) (See tables below). Secondly there would be an advantage in having the elevator servos at the tail end; with using the 120 AC (which is 3oz heavier than the 140FZ) it would have possibly required some tail weight to balance the airframe. The only disadvantage to this set-up as far as I am aware is that it costs an extra £4.50p!!!

Single Servo with Carbon rod / MK Dual Elevator Crank
Cost
Weight
Futaba 9204 servo
£60.40
53 Grams
Carbon Rod

£3.50
30 Grams total
4-40 ends
£5.50
MK Ballraced Fittings
2 x £8.95 = £17.90
MK Dual Elevator Crank
£26.99
30 Grams
Totals
£114.29
113 Grams

Control surface Linkage is assumed to be the same cost and weight for both set-ups (MK Ballraced ends with 3/16" carbon rod/Titanium ends)

Twin Volz micro Maxx servo's in tail plane
Cost
Weight
Volz micro Maxx Servo's
2 x £55.95 = £111.90
2 x 19G = 38 Grams
1m Extension lead & "Y" lead

£3.50 + £2.95 = £6.95
25 Grams total
Servo Housings
Made from Scrap Material = £0.00
 2 x 15g = 30 Grams
Totals
£118.85
93 Grams

The Building

The Tailplane Installation
The first job to be done was the tailplane installation; the centre section of the tail had already been cut out with the phenolic tubes installed. The fitting of the incidence adjusters were all that was required before fitting into the fuz. At this stage provision was also made in the centre section for the cables to the Volz servo's, which would be fitted at a later date.

The Wing Installation
The holes for the wing tubes were pre bored out ready to receive the phenolic tubes. The fuz had pre marked out lines for the wing tube holes and wing adjusters. I found that the process of lining up the wing with the tail plane on the fuz, quite a tricky operation as you don't get a second chance with this one (no wing seat to shim if you get it wrong!). After many phone calls to Phil for help the wing was finally installed in the fuz. Looking back, it was a relatively straightforward installation, but I did have several dry runs and a few nightmares as the glue was going off.

Retracts and Aileron Servo's
Holes for the retracts and aileron servo's were ready cut out, all that is needed is to fit the mounts. Built in to the wing there are two light ply ribs that are used to support the phenolic tubes for the wing spar. These ribs have a dual purpose of also giving the retract mounts extra support by spreading the forces of landing across the wing. I used the standard Supra DX 60's retracts using the ZN boxes that just slot in-between the ribs built into the wing, a very neat light system that is very easy to fit, but more importantly makes a very strong fixing. Again on the aileron servo's, I used the ZN boxes for the Futaba 9102 servos. (The cost of these boxes makes it is hardly worth spending the time making your own)

The Engine Installation
The F1 was made from 6mm-end grain balsa covered with carbon fibre; the holes for the Hyde mount came predrilled. When fitted in the fuz with the engine attached, gave the correct side thrust and down thrust for the model. I found that this was the most straight forward of all to install, there was very little to go wrong, as the F1, Hyde mount and engine were more or less self-aligning when assembled.


Spraying
All imperfections on the fuz were filled using epoxy and micro balloons as filler then rubbed down with 1500 grade to a smooth flat finish, the better the finish the less paint needed. The fuz was finished using standard auto 2-pack paint mixed to match the covering material. A note on the safety aspect first, this paint if you don't already know contains Isocyanates, which are a bit nasty to say the least. Great care should be taken when handling these paints, full-face mask fed with breathing air should be used and avoid skin contact. Bearing this in mind, I did all my spraying outside in the garden. At this point things started to go wrong; I have discovered that when spraying the white and yellow colours (it only seams to be those colours) every insect in the street was attracted to my freshly painted fuz! All I could do was watch in horror and wait until the paint dried then cut it back where the insects had landed. This was not the end of my troubles, whilst spraying the blue, a gust of wind blew the fuz off it's stand and on to the grass before the paint had dried. This disaster had to be cut back and resprayed, but in the course of cutting back the paint I rubbed the red paint back to the gel coat I had sprayed previously. By this time I had just about lost all patience with the model and it stood in the garage for a couple of weeks. The end result was worth it though; overall including primer the paint job weighed 2 1/2 oz. I did not follow the current trend of spraying a lacquer coat as I considered it would add too much weight for no benefit.

Covering
Covering was straightforward, I used Profilm, It's a bit heavier than Solafilm, but it seems to produce a better finish and it's easier to iron on. The colour scheme was cut out and ironed as one layer to save weight.


Installing the equipment
After installing the retracts, aileron/elevator/rudder servos the final position for the fuel tank, receiver and battery were left until the model had been covered, the idea being that I was left with plenty of scope to position the battery to adjust the CG. I eventually decided to use a single 1200mha battery on a heavy-duty Futaba switch. In the event the model came out tail heavy and needed the battery forward and it still required 3oz of lead in the nose. While on the subject of weight, my target all up dry weight I was building to of 9lb 12oz didn't quite work out, including the 3oz of lead the overall weight came out at 10lb 4oz. But this is still 1lb lighter than my current model!
At this stage it is worth mentioning that although I used better quality servos for the flying surfaces you could equally use Futaba/JR budget servos on this model to keep the costs down, without sacrificing control accuracy. At my standard of flying I don't think I could notice the difference anyway.

Conclusions
This is the first composite glass fibre kit I have built and looking back there were no real problems I could not overcome. The help and advice I received from Phil Williams of Probuild was excellent to say the least, no matter what time of day I rang him for help, Phil always had time to help me with advice. 10/10 Phil

I probably spent more time building than most, but I enjoy building and testing my practical skills, (a bit like flying aerobatics) with the end result of creating something to be proud of. (Job satisfaction!)
I am looking forward to flying the Shadow and from all the reports I am hearing about this model it will be excellent to fly. I have even heard it flies better than some of the ZN and PL models! (Not bad for a British kit!)

This model is a great introduction to flying aerobatics and to four stroke engines. Although the profile looks a bit dated, it is a well-balanced design that requires little or no trimming and is competitive in all the classes with the right power plant installed. I intend to fly mine in standard and senior class with a second hand YS 120AC next year. If you fitted a second hand 140FZ or L it would be more than capable of handling the Masters Schedule too.

Value for Money Rating 10/10

 

Many thanks to Martyn Uttley for the review.