Building a Jetex "Tailored" Skyray

This addition to Nostalgia Corner could not have been written without the generosity of Andy Blackwell, who gave me the chance to build one of his collection of Jetex Tailored kits, produced in the 1950's and now extremely collectable. The only condition was that I wrote up the experience to share with others, which of course, I was more than happy to do. The Skyray was released by Wilmot Mansour in 1954 as part of the "Mach 1 + Series" and was designed to be flown with a Jetex 50 motor. These kits were not cheap when they were first produced, the Skyray retailing at 10/6d in 1954. As with the rest of the Tailored range, the body shells were supplied as pre-formed balsa skins to give a realistic smooth finish, better representing a metal skinned aircraft than traditional stringers and tissue. The unique construction makes it very difficult to build a replica of a tailored kit, so I jumped at the chance to build a little bit of modelling history.

So, let's put ourselves into the shoes of a keen young aeromodeller back in 1954. It's Christmas, and our parents have treated us to an exciting new kit. We examine the box first, already getting excited about the delights that await within......

You can see that this particular example was bought from Gamages for the princley sum of 11/4d.

More tempting Jetex Tailored models advertised on the back of the box.

So, here are the bits you find in the tightly packed box, plus the plan which you can see below. The original kit did not come with a Jetex 50 motor as shown here, but did come with the mount that the motor is sitting inside and the augmentor tube. The moulded parts consist of a layer of balsa backed with a layer of adhesive and then paper inside. It is a credit to the forming method that after about 55 years, the parts have kept their shape perfectly. This particular kit had obviously been well looked after, because all the wood in it looked like new. You will see there were two nose sections included when you only need one - I'm not sure if this is deliberate or not. The four flat blasa parts sheets are cleanly die cut. The canopy is very crisply vac-formed, and the decal sheet is well printed. The little envelope on the right, next to the canopy, contains the moulded access hatch catches.

The plan is clearly drawn with full size drawings and helpful sketches, with detailed instructions on the right hand side.

Taking a deep breath, it was time to start the task of getting this classic kit model in the air, where (with apologies to all you kit collectors out there) I think it really belongs. The first building task was to place the pristine, unmarked 55 year old plan over the building board and pin down the internal wing structure. The Skyray wing has a symmetrical section, and the plan shows exactly where to put 1/16" shims under the ribs to keep everything level. Nice to see such attention to detail already apparent so early in the construction.

The wing skins are die cut from nice light 1/32" sheet with the grain running exactly in the correct direction parallel to the spar. The edges have to be carefully chamfered on the inside and one skin pinned into position onto the wing frame.

The process is repeated on the other side to give a light but strong component.

The wings are finished by adding the elevons, which were really the only area where I had problems throughout the whole build. Hinges are supplied cut from aluminium sheet, and the upper and lower surfaces are glued each side of this sheet, to give a wedge section, with the aluminium sticking out at the thick end. I used balsa cement (mistake) which pulled in the wood as it dried to give a concave surface both sides. Epoxy would have worked better. However, after cutting a slot in the back of the wing to take the aluminium sheet and gluing the elevon into position, it was clear that the aluminium hinge was far too stiff - any attempt to adjust the angle just resulted in broken or crushed balsa. So, I reverted to plan B and made new elevons from light 1/8" sheet, attaching them to the wings with short lengths of soft wire (from sandwich bag ties).

Fuselage construction commenced with the pinning down of the central keel and adding the side formers and front side keel. Formers F3 and F4 have openings in them to allow air into the model, but they are quite fragile at this stage, so the die cut middles were left in place until later. Care was taken to keep the formers perpendicular to the building board.

Next the root rib R1 is added, plus the joining piece in front of this between F3 and F4. It's important that R1 is parallel to the building board - only a little adjustment was needed as the parts were very accurately cut.

The process is repeated for the other half of the model - again this is built on the board. The two completed fuselage halves are then glued together, keel to keel, around the augmentor tube. You may have spotted that the bell of the augmentor tube is not round, but oval in section to fit in the aperture in former F5. The slightly scary thing is that you have to squeeze the end of the tube yourself to match the shape which is given on the plan. I took this very slowly, a bit at a time, worried I would crack or damage the tube. In the end it did not prove too difficult, and I was impressed how accurately it fitted inside the formers.

Time to fit the first fuselage skin. These have to be cut to shape, based on embossing inside the formed sheets which show where the extents should be. Some of these were a little vague, so a certain amount of trial and arror was necessary. The lower hatch also had to be accurately cut out so it lay between F4 and F5. This view shows the paper layer on the inside of the skin.

I used aliphatic wood glue to attach the skin to the fuselage frame to give me a bit of working time and held everything in place with pins while it dried. The fit was very good.

The next step was to fit the lower hatch into the aperture and set up the fiddly little red catches. The hatch is preshaped and has a slot cut into it to take the finger grip which gives you something to hold onto when launching the model. I decided to omit this and filled the slot with scrap sheet.

I confess I had to read and reread the instruction leaflet that came with the clips several times before I understood how they worked. They were not easy to fit, but I got there eventually. Some distortion had crept into the plastic clips over the years, but a bit of gentle bending in hot water sorted that out. Looking from underneath, the clips are moved outwards in their slots to release the hatch.

The kit contains this aluminium motor mount which encloses the whole motor body, doubtless to protect the internal structure of the model from the heat of the motor casing. There is also no danger of the motor coming adrift mid flight or on landing. The mount comes attached to a piece of ply which needs to be glued to the top of the hatch.

With the hatch in position, the motor had to be carefully positioned centrally in the mouth of the augmenter tube before the glue set.

The upper fuselage skin could now be fitted, again using aliphatic wood glue, held in place using pins while the glue dried. When dry the edges were carefully trimmed at the wing roots and air intakes.

Here you can see how the rear of the augmenter tube is located between the trimmed fuselage shells.

Asbstos paper (remember that?) is supplied in the kit to line the interior of the fuselage round the motor and protect it from the heat. With a careless disregard for my own safety I cut pieces to fit and glued them in place using aliphatic glue again (on the basis that balsa cement might be a tad flammable).

The nose is formed from two moulded sides which come together on one sheet of laminated balsa. This photo shows the inner paper layer with moulded steps showing where to separate the parts.

Here is one of the nose halves cut out and ready for fitting. The forming process could not quite cope with the extreme tip, but this doesn't matter as it will be cut off and replaced with a block.

The right hand nose piece was fitted after careful trimming to fit neatly inside the intake.

The second nose piece is fitted by simply overlapping the first, which saves having to trim it accurately to the centreline.

Once sanded the joins top and bottom clean up very well.

Here the nose block has been added, shaped and sanded and the additional strips glued to the front of the air intakes. The right hand intake has already been shaped.

Time to glue the wings to the completed fuselage. The fit was pretty good, though the wings came out slightly thicker than the wing roots leading to a small step.

I could have left the step but decided to try to make a smooth transition by gluing in a shaped piece of 1/32" sheet.

After sanding, the result was a nicely blended wing to fuselage joint.

The fin is made up of four laminations of 1/16" sheet and has to be carved and sanded to shape - so tapered towards the tip with a streamlined section.

Once the fin has been shaped it has to be fitted into the upper fuselage skin. The procedure is to cut a slit on the centreline and peel the skin back both sides to insert the fin. The skin edges are glued to the sides of the fin, then sanded to blend them in when dry. This didn't sound a very promising method to get a neat result, but in practice it worked quite well.

I decided not to cover the model in tissue to save weight - just gave the whole thing two coats of sanding sealer, sanded between coats. If any grain shows through the final paint job, then so be it.

The vac-formed canopy was trimmed to fit the fuselage then held in position while a line was drawn round it using a thin marker pen. This allowed me to paint the area under the canopy black without getting too much ouside the apropriate region. You can also see a few dabs of white lightweight filler in this photo used to blend in a few small steps.

When the black paint was dry the canopy was fixed in position using Formula 560 Canopy Glue.

Here she is ready for test glides. The model is very tactile, by which I mean it is a nice object to handle and feel - quite different from a tissue covered model. The balsa skinning alows a much better reproduction of a metal skinned aircraft, without any ribs or stringers showing through the tissue. I decided to leave the model unpainted for test flights to keep the weight to a minimum.

My old stick and tissue Douglas skyray is a similar size to the Jetex kit, so I thought it would be interesting to compare the two models.

My design has a wingspan of 10.25 inches and weighs 19 grams empty, increasing to 26.5 grams when a new Rapier L2 is fitted.

The Jetex Skyray had a slightly smaller wingspan of 9.5 inches and weighs 25 grams with the motor mount removed. If you put the hatch and motor mount back this goes up to 30 grams, and 35.5 grams with an empty Jetex 50 motor. So, you do pay a price for the all balsa construction - 9 grams plus the fuel pellets for the Jetex motor, and that's with slightly less wing area.

We had a go at flying the Skyray at a rather windy Old Warden late in 2011, but didn't manage a complete flight. Some clay needed to be added to the nose, and the elevons adjusted to get a straight glide. It is a very tricky model to launch, and I wonder now if it was a mistake to leave off the launching tab under the hatch. The old Red Spot fuel Andy Blackwell donated seemed to have enough power but the windy conditions meant it was just too difficult to work out what trimming adjustments were necessary to get it going. We'll try again when we get a better flying day and let you know the results.

I really enjoyed making this model, and was really impressed with the quality of the kit contents and the obvious care that went into the design. Huge thanks to Andy Blackwell for giving me the chance to build a little bit of modelling history.

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