Adrenaline Review

A Christmas present reviewed by Trevor Hewson

(Originally written in 1999 for 'Sloping Off', the Newsletter of the Christchurch and District Model Flying Club)

Present and Presentation
The first photo was taken on Christmas Day, 1998. Yes, I got an aeroplane for Christmas! As you can see from the picture, the Adrenaline, which comes from the local company, Purbeck Sailplanes, is supplied in a stout, plain and very long cardboard box. Mine was collected but, judging by the box and the packing, I have no doubt that it would withstand the rigours of the carriers.

Wing Wizardry
Inside, in its foam blanks, is the wing. This is in one piece - hence the long box - and is beautiful. 1.5mm obechi veneer is used over a good quality white foam. However the veneer hides many of the real virtues of this wing. Peer at the trailing edge and a dark stripe between the veneers shows a carbon reinforced TE - sand it as sharp as you like! The aileron hinge line is routed out from below and the ailerons are already cut free at the ends, yet still attached to the wing. This is done by the inclusion of a Kevlar insert beneath the top veneer, providing a living, gapless hinge.

Investigation of the front bolt hole shows a stout ply insert which, according to the instruction leaflet, transmits the inevitable stresses to further carbon fibre elements in the wing. No need to spoil the one-piece veneer surfaces by bandaging the joint.

With so much work already done, it seems almost surprising that the buyer has to fit the leading edges and wingtips. The LE's are square section obechi strips of good quality and the tips are cut from a balsa/ply/balsa sandwich so that they can be easily shaped whilst retaining a measure of ding resistance all round. Once the tips have been fitted, the wing will no longer fit back into that lovely box. Shame that.

Servo wells are milled out into the foam (although I did need to deepen them) and tubes for the servo leads are built into the wing. No servo covers are provided.

Fuselage Focus
The wing is a hard act to follow, but the fus is every bit as interesting. It is an epoxy glass moulding of high quality - a good finish and very stiff. There is no sign of carbon fibre or other reinforcement in the fus, so the strength seems to come entirely from the glass lay-up. The rigidity may also be helped by the fact that the wing seat is sealed, so the 'closed cylinder' structure of the fuselage is preserved.

The first thing that strikes you about the fus is that, in spite of the long box, someone has sawn the nose off! The second thing that strikes you is that there appear to be two nose sections.

It soon becomes clear that the 'extra' nose section is to be glued into the tail section, leaving the sawn off nose to form a detachable sheath. This is a very neat and practical arrangement for the finished model and also means that, before the nose section is fitted, access to the tail section for installing linkages, aerial tube and wing fixing nuts is still quite possible, in spite of the lack of a wing seat aperture.

Tail Pieces
The (all moving) tailplane and (side hinged) rudder are cut from balsa/ply/balsa laminations after the fashion of the wingtips. Again a practical approach, albeit somewhat heavy. The option of lightening holes is mentioned in the instructions and, if you want to reduce the amount of lead fitted in that fairly short nose, I recommend that you take courage and fit the biggest holes you can find. I removed some 13g of wood which saves about 39g of noseweight, resulting in a weight reduction of 52g (about 2oz). Even if you expect to fly with ballast most of the time, reducing the weight of the extremities will improve the agility of the model. The tail surfaces, after sanding to section are still very stiff, hence my recommendation to be brave with those holes.

Other Bits
All that's left in the box now is a snake (for the rudder), a dowel pushrod (for the tailplane) and the inevitable bag of bits.

Assembly
This is not an ARTF model but, with so much prefabrication of the wing and fuselage, I couldn't bring myself to describe this process as 'building'!

Order, Order!
The instruction leaflet acknowledges that "experienced builders will have their own preferences" and I would certainly advocate that you read through the suggested assembly sequence before you start, to check whether you are comfortable with it. I feel that the sequence described is chosen for ease of description rather than ease of access and so I did much more fitting out of the front and rear sections before joining them together. This does result in frequent 'offering up' for alignment checks, but does also reduce the demands on one's keyhole surgery skills. I certainly would not have fancied my chances of fitting the wing retaining nuts after the nose section was in place.

Weighty Matters
The Adrenaline has provision for two 6oz steel bars for ballast, sliding into aluminium tubes epoxied into the fus beneath the wing seat. The underside of the inner nose section is cleverly fluted to enable the weights to be inserted and also to help to secure the tubes themselves.

Radio Bits
One downside to this fluting is that the available servo depth is reduced. Although there is plenty of headroom above the servos, they do need to be mounted as low as possible to minimise the offset needed in the elevator pushrod end. It's also wise to position the servo plate as far to the rear as possible, whilst still being able to get at the mounting screws. This will maximise the space for the receiver and so reduce the risk that you will have to go out and buy a smaller one!

I used Hitec HS80 servos for rudder and elevator, but for the ailerons, I pressed into service two of the old Harry Brooks micro servos. These were very cheap and cheerful servos sold a long time ago when even a mini servo from a main brand manufacturer would have set you back £30 to £40. I acquired four of these (plus speed controller, gyro and motor) with the second hand Kyosho Concept EP electric helicopter I bought back in 1993. I damaged one of the servos fairly early on but, after 175 flights, the other three seemed as good as new and (and this was the real clincher) they are fitted with servo leads long enough not to need extending!

Since these old servos owed me nothing, I was happy to chop the mounting lugs off and stick them in with bath sealant. A few judiciously placed balsa blocks serve both to prevent any movement and also to support the servo covers of mirralite ply.

The tail end is all straightforward - if installing the pivot for an all-moving tail can ever be described as straightforward. So now it's all about...

Finishing
Regular readers will know the lengths that I will go to to avoid the use of paint. However, beautiful though the fus is, the natural beige/yellow colour of epoxy resin is far from attractive, and even I would not try to apply Profilm to a glass fus. So, paint it had to be.

First though, a quick check of the Profilm stock showed enough ex-Stearman yellow to do one half of the flying surfaces and enough blue to do the other half. Following the 'light top, dark bottom' visibility rule suggested a blue fus, so the next task was to find some blue paint to match the Profilm. I eventually chose an acrylic car paint, applying an acrylic plastic primer and a coat of filler primer before rubbing down and spraying the top coat. For once, the painting process passed off without major hitch and the end result is quite passable.

Returning to the film covering, I contemplated the colour change along the leading edge. Joins here are never a good idea. Quite apart from the problem of getting a neat straight line, there is always the risk of the film lifting in the face of the onslaught of the slipstream. Another rummage in the film stock, and a red leading edge flash was added to the colour scheme and, just to pretend that it was planned this way all along, the rudder was covered in red, too.

Covering the already hinged ailerons posed a few problems, but, once a few stripes of film had been added to the fus sideto help line up the nose cone, I took a few paces backwards and the finished product looked pleasant enough.

Balancing Act
With everything in place, 5.75oz of lead were needed to bring the balance to the recommended point.

All that remained now was to program the radio. The instructions give control surface movements for aileron, rudder and elevator and for an up-aileron spoiler function. Coupled elevator and flap is also suggested and, by the time I had arranged the option for a bit of down flap for height gain, I had re-programmed my FF7 transmitter three times.

My real problem though was that the cheapo aileron servos were having a hard time with the somewhat stiff aileron hinges. Disconnecting the linkage and vigorously exercising the hinges helped a bit, but I had to settle for less up aileron in the airbrake function in order to ensure that aileron control would not be lost when the brake was activated. I hope that the hinges will free up with use.

All Systems Go
A grey day at the picnic site was the venue for the maiden flight. Only Jim Ruffell and Barry Hawkins were present, everyone else having gone to Ringstead. Lift was reliable but unspectacular, Barry flying his Infinity Starlite and Jim his Graffiti.

After the usual checks, Jim launched the Adrenaline and it was evident from the start that this is a very well mannered aeroplane. Somehow the model inspires confidence - you know it is going to do what you tell it to. It also soon became clear that the recommended cg was, as the instructions indicated, on the safe side, so after a few minutes familiarisation, a landing was called and some lead removed.

The second flight was better, but the light conditions didn't allow the model's flight envelope to be explored, and the sea mist was closing in. I felt the model was still a bit nose heavy, but it was time to call it a day and wait for a better day. Back home, a bit more lead was removed.

Take Two
Two weeks later, on a bright, sunny and perishing cold February day at Win Green, I got the chance to try the Adrenaline again, this time in the teeth of a freezing force 5. One of the two ballast bars was inserted and, intimidated by the wild conditions, the last bit of lead removed from the nose was put back again!

The Adrenaline was fully at home in the conditions, but I have to confess that I wasn't. The lift was tremendous and, every time I found an empty piece of sky, it seemed like it would immediately be bisected by a high speed piece of plastic. Nonetheless, I managed to thread my way through the traffic for ten minutes or so and found the occasional opportunity to enjoy the smooth aerobatic behaviour of this very pilot-friendly model. I look forward to much more of the same, in somewhat clearer skies.

Wrap Up
There was a time not so long ago when, on a day like last Sunday, the sky would have been full of Phase 6's. Now there are three categories of model to be seen on such days: The all moulded F3F-derivatives, typified by the Ellipse; The EPP foamies, typified by the Wild Thing and Bullet; and the 60" aerobatic racer. In the last category I have yet to see anything to rival the Adrenaline.