Xplorer 2 F5J Review

I am a big fan of the Xplorer from Nan Models so I was more than interested when I heard that Acemodel had taken delivery of their latest creation.  Fortunately for me, I had just sold some unused models to raise cash for another project ( which I quickly binned), and after some negotiations with Austin at Acemodel, I got me one of the first (maybe the first) of this new breed

This model is especially made for F5j and is VERY light !  It is delivered with label warning not to attempt winch launching with it.

Wingspan is 3.8mtrs with the latest X2 airfoil, and the fus. is cross tail with an all moving tailplane.

It is all moulded. Wings and tail are glass rather than carbon spread tow, which keep’s the weight down. The fus, looks like a new design, as it has not got the characteristic F3j ‘droop nose’, and is moulded in Kevlar with carbon reinforcement

For a model of this weight, the finish of white on top, blue on the underside, and the fit of parts is the best I have seen. It also has a snazzy new logo

The total airframe weight including joiners and the usual pack of bits is 1130g 

At the moment I am deciding what equipment to put in it, and I will update this post as I get the various bits installed.

I hope to end up with a model flying weight of about 1500/1600g, which if I have made the calculation correctly will result in a wing loading of around 19g/dm2 which in old money is 6.2oz.sq.ft 

One area that helps in keeping weight down is the size of wing joiners.

Xplorer F3j wing joiners are pretty substantial but amazingly light for their size.

As there is no need for the same F3j spar in this model and the wing joiners can be that much smaller.

Here are both side by side for comparison

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Now getting ready to put the model together. My servos have arrived so I made a start with the wings.

I am sure everyone has their own preferred wing servo installation technique, and I have tried many different ways. Until a year or so ago I always used to wrap servo’s in heatshrink, after first cutting off the mounting lugs, and then epoxy them into the wing. Very quick and easy to do, and I only ever had one failure. But it was always a pain to change or repair anything, and if you suffered a failure at a comp it would be the end of your day.

Learning from others and stealing their ideas, I changed to proper servo mounts and this is what I do now. I have found it to be a most secure and very light method.

I use the light ply servo mounts available from several suppliers. I glue a .5mm ply backing to each mount and make up a few alloy retaining plates for the servos which do not have a side mounting lug.

Each finished mount weighs 3.6g and gives a massive glue area when epoxied into the wing. This  helps to stop any distortion to the wing skin.

Here are a few pics showing what I do.

Servo’s for flaps and ailerons now installed.

The pics I hope give an idea of the process with Xplorers.

The first job is to make sure that the threads in the horn mounting points are clear. I do this with an M3 tap. If you don’t do this it can be difficult to screw the supplied horns in. Also it is more than likely that if there is any epoxy in the threads, it will get pushed down the mounting point eventually damaging the undersurface of the flap or aileron. Even doing this, I still had to cut down the thread length of the aileron horns by 2mm to avoid them damaging the under surface.The flap horns fitted perfectly, no adjustment needed..

Once the horns are screwed in, it is a fairly simple matter of cutting out a slot in the balsa trailing edge subspar and then enlarging the already marked slots in the top surface to clear your clevis.

The carbon patch gluing area inside the wing needs to be cleaned and rubbed down before the servos are glued in

I always find it a bit of a fiddle to set up the servo and its linkage geometry. Repeated dry fitting of everything to get the amount of surface deflection you need for me is the only way to get it right.

I always use masking tape to keep the wing surface free from epoxy marks, and a heavy steel block to hold the servo in position whilst the 30min epoxy cures.

Made up my wing wire loom today  .

I like to make up my own plugs but harnesses can be purchased from Acemodel.co.uk

Servo wire was a bit of a problem as I much prefer the actual wire to be of the very fine ‘copper ‘type.It is more flexible and possibly a better conductor than the more usual ‘steel’ type which seems to be pretty much universal now.  I could not find a UK supplier of the very light weight wire I normally use,  so had no alternative but to go back to the supplier Nessel who I bought from  the last time I went to the Sinsheim exhibition in Germany. It’s excellent stuff .

This new Xplorer came with a very neat carbon fibre moulding in which to mount the ‘D’plug. The moulding is glued into the wing and the plug screw fixed into it. It adds virtually no extra weight to the centre panel and must make it possible for the wing moulding to be lighter.

My motor arrived so on to the next stage.

There must be as many ways of gluing your motor in as there are for mounting servos. Once again I have developed my own way, which is not original.

First the motor nose disk.

As can be seen in the pic, I file a few ‘notches’ on the edge of the disk. I have found this to be important as these make voids which allows the epoxy used to fix the mount in the nose of the fus.to form hard keys. This helps the joint to cope with any sudden shocks as caused by motor torque on start up or when stopping.

Having tried a number of different epoxies I have found that Loctite Hysol is about the best for this job. Trouble is it takes a good 24hr to cure and it’s a bit ‘liquid’ when first mixed. Being liquid it’s not easy to get it to stay in the right place, or avoid getting everywhere you don’t want it!

The motor disk fit inside the Xplorer nose is perfect so there is no problem with alignment etc, but the nose is narrow and if you are installing an out runner type motor, the motor wires will press on the fus. and this can cause the motor to move while the epoxy is curing. To get round this, I first wrap the motor in heatshrink before I screw it on to the motor disk.

The outer nose of the model is also covered with masking tape and the epoxy is applied. I put a thin coat inside around the nose and then a thick layer on the rear face of the motor mount.

The unit is then quickly inserted into the nose and held in position whilst the nose spinner is fixed onto the motor shaft which holds the motor unit in place. Once this is done and everything is lined up, I suspend the fus. vertically, nose down and gravity takes over. The thick layer of epoxy gradually flows and finds its own level, around the gearbox and filling any voids on and round the disk .

Once the epoxy is cured the motor is removed from the fus, the heatshrink cut off the motor, and the masking tape stripped of the nose.

Job done. 

Last few jobs now.

With the motor in place it is time to sort out the balance of the model.  As this plane is a prototype I was a bit concerned about the balance point for best safety on first launch. As it is virtually the same in all respects (other than in strength and weight) to the F3j model, I took the recommended 120mm back from the leading edge. To achieve this, my esc and a 1300mAh 3s lipo were placed side by side about 25mm behind the motor. Immediately aft of these the servos were placed, and then my Multiplex DR9 rx a further 25mm behind them.

The servos are mounted in a carbon fibre moulding which is shaped to fit inside the fus. This was found to be just a bit under width for my installation, but cyano-ing a strip of thin scrap carbon sheet to either side of the moulding made a perfect fit.

As can be seen, with all the equipment installed, it does look a bit busy. But in fact there is plenty of room, nothing is a tight fit and with the lipo held in place with Velcro it can be moved approx 25mm either way if needed to adjust balance.

So ready to go the final flying weight is 1650g 

In the good old Imperial  measures I can relate to, this results in a wing loading of just over 6oz.sq.ft which is lower than that of my last ‘light weight’ AVA. 

Flight test soon. Can’t wait.

First flights completed.

Before I attempted to get the model in the air, I thought it worth making extra sure that the tailplane angle was as near to correct as I could get it. Eyeballing, it looked OK, but not wanting to take any chances I used my old and trusty Graupner incidence checker to make sure.

With the wing held onto a flat level surface the gauge showed that the centre line through the wing airfoil was +2deg. It was just as well that I did check because my tailplane was set at -2.5deg. I adjusted the servo clevis to get to a setting of -0.5deg as I thought this would be nearer to what was needed.

So Saturday at the field, range check completed, all controls going the correct way, nothing else to worry about.

Club mate Jason offered to launch for me, and I was very pleased to accept his help. I don’t usually worry much about self launching a new model, but this time I was as it was  windier than I had hoped for.

First clime away was no problem at all,  elevator setting seemed good and I levelled off before the limiter cut the motor run and  into  the glide. The model flew extremely well but it did seem a bit tail heavy. Jason tried to take some in flight shots for me, but as the wind got up I was more nervous of soaring closer to the ground so he had a difficult task.

The model was also reacting to any turn command slowly, (which made me unhappy about getting close for inflight shots) and I thought this was something I would need to get used so decided to land to get the balance moved forward.

Landing was easy and controlled in the now blustery conditions. I moved the lipo forward 10mm and checked controls before a re launch. This was when I noticed  I had managed to reverse my aileron differential with 3 times as much down throw as up. 

No wonder it was a bit slow reacting to a turn!

Once this was corrected the model showed that it is very agile despite it’s low weight and large wing span.

I planned to use the model mostly for those occasions  when the air is full of ‘clag’ with little or no lift, or the even rarer no wind days.

But the way it flew in the wind, gives me confidence that I will be able to fly it more often 

You can purchase this model here

Peter Mitchell.