Project

This article describes my build of the CMPro Ventus 2HX near scale glider.  Not top end of market as models go but will enable many to get into gliding either off the slopes or via aero-tow.  This glider is a 2.6 meter model with air brakes, retractable wheel and should weigh in at about 1200g  - 1300g depending on your set-up.  It can be flown using the minimum of three channels or 6 -7 depending on your build and type of use.

The first thing you notice is the finish of the fuselage which is GRP on ply formers.  Decals are pre-fitted and lay under a protective gloss coat.  Larger decals are included for the wings but are not applied.  The wings are traditional built-up balsa/ply and covered in a white film.  The wing tips are finished with plastic winglets.

In the parts bags are the undercarriage/wheel (assembled), gear doors, lots of small ply parts which when glued together become the cockpit lock mechanism.  Laying and taped down in the main box is the steel wing spar (the Discus used carbon rod) some wire rods (which will become control rods) and a bag of tiny plastics parts which include small clevises, rudder control wire & fittings, grub screws for collets etc.

The rather long box when opened revealed the fuselage and the wings supported off the box sides by cardboard cartons.  The accessories and small parts were taped securely to the box bottom.  The only thing I noticed that needed repairing was a small split in ther grp fuselage, on the bottom below the fin.  This seems common as I had to gel the CMPro Cessna too, but this was just forward of the fin at the top of the fuselage.  Other than that the packaging ensured the model travelled safely.

The manual is just a few pages of B&W A4 size booklet.  There is minimum information and what there is, is in Chinese & poor English.  However, the pictures are a little bit more helpful but I think in reality you have to assemble it the way you think fit.  Sometimes though the text and/or images can be a bit ambiguous.  My policy is to play with it first, toy with it and if it works as supposed too then that should fine.

Also before getting started you will need to acquire some servo extensions. I used three 600 mm and one 300mm.  Two required for the ailerons.  The 600 and 300 need to be joined together.  This is to connect the elevator servo lead to the receiver, running the length opf theb fuselage.  I taped my connectors together with insulating tape but some favour hardwiring (Cutting the plug and sockets off, soldering and heat shrink the joins)

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First job is prepare the wings - To fit the servos the covering has to be carefully cut above the servo area leaving a little overhanging to tuck under neatly.  The servo covers act as servo mounts too and have to be cut out from the plastic pressing.  In my case I had to create my own slots for the servo arms using a 4 mm drill at each end and then using a craft knife to cut away in between.  The manual says to stick the servos on to the plastic covers with double-sided tape (not supplied).  Surely after a few flights the aileron servo is going to move or worse, come unstuck.  To overcome this I cut some PVC right-angle profile into little brackets.  Using the servo as a guide I marked their positions against the servo body.  I then glued these angles down with plastic weld. (See Photos)  Now the servo clips in and cannot move forward or back due to the clips, is stuck down with "No More Nails" double-sided pads and when fitted into the wing cannot move away from the servo cover!  This little trick came in useful later with another servo location.

At this point I lengthened the servo's lead by adding a 600mm extension, the joint being taped securely.  Using a thin wire I pulled the lead through the wing.  Using a spare radio set and receiver I centred the servo, screwed the servo into position and marked the postion of the control horn.  With this screwed into place all that was needed now was to rummage through the small parts bags for a short threaded rod and two plastic clevises.  Adjust the aileron for neutral and thats done.  Same process for the other wing!

Now at this point the manual says it's time to fit the airbrakes.  I did not at this point because there were some considerations to take into account.

Now using the 8mm steel rod and two 4mm  anti-twist rods passed through their respective positions in the fuselage I placed the wing locking collars into the holes in the wing top surface, discovered by cutting away with a craft knife.  These collars must orientated correctly in height and axis other wise you may find it difficult to fit the wings back on again later.  So using the rods as guides I slid the wings into their positions , the two smaller rods passing through the collars.  Okay that's the dry run done!  I then gave the rods some Vaseline jelly (prevents adhesion of epoxy) and re-inserted them into the fuselage.  Putting some epoxy on to the collars bodies, placed them in position, pushing the wing fully through so that the rods would make the final resting places of the collars.  Once the epoxy had set, pulled the wings out with their rods.  That job done!  Coffee time I think...

The rudder is hinged using two round CA Mylar type hinges.  This job is simple enough although need to look at picture for location vertically.  The bottom edge should be in line or slightly above the bottom of the fuselage.  This will ensure that the elevator control rod and elevator don't foul the rudder in flight.  Checking that both hinges can slide in at least halfway with no resistance.  When sure the fit is okay, using CA Thin the hinges into the Rudder first.  Once secure slid rudder into the fin and bending the rudder each way dropped some CA in to hinges fin-side.

Now for some more customisation.  Fitting the elevator servo.  If there is two items in flight which must go wrong are loss of ailerons or elevators!  Again the manual states stick servo on to the servo's plastric mounting plate.  As previously seen earlier in this article with regards to wing servos, I used a similar trick again.  But this time the servo needed to have it's chances of movement stricter- this time in all axis's. (See Photos)  Using small angles of PVC profile I again glued two pieces to the servo panel to hold each side of the servo body.  in addition another piece was located so that the servo bottom was held too.  Now the servo which needs to be pushed firmly between the "brackets" is also held down by "No More Nails" double sided tape.  With the servo centralised and the arm at 90 degrees screwed in to place the mounting drilling four 1 mm holes in each corner of mounting and also the fin.   Installed into the fin the servo cannot moved in any direction!  next I made up another control rod from threaded rods and two clevises.  Fitting this rod on to the servo arm ensuring that when the servo is fully operated across its range the arm doesn't touchl the slot ends.

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Next job is to fit and align the "T" tail stabiliser.  This is secured using two socket headed screws that wind into two nuts that have been "glassed" into the fin top.  This has to be located at right angles to fin but also in alignment with  main wings.  Using a flat surface I inserted the main wing rod through the fuslage.  I then placed the rods ends onto two identical height blocks.  This is ensures that the aircraft is level.  Now locating the stab we can check that it is near true to right angles to the fin but also parallel to main wings.  In my case the stabiliser tips were different by 18mm from the flat surface.  Some double-sided tape stuck to one side of the top of the fin cured this problem.  Firmly wound down the socket head screws to secure.

All that was left here to do was align a control horn with the servo arm and linkage, after re-centreing, and fit into position.  There should be between 10mm and 6mm of elevator movement each way.  I think I have just got that with the supplied fittings.

Fitting the servos, I am using HS81's, in their respective places in the fuselage.  The servo tray is pre-cut for the retract, gear, rudder and tow-release servo.  The Hitecs fitted easily but I had to CA Thin the screw holes to ensure the screws don't work loose.  The tray is very thin ply too!

Using the supplied pre-cut ply plate the retract mechanism was installed.  One end slides in to a slot and the the cockpit end is locked down in place by the ply-plate which is epoxied into postion. 

The gear doors were dry fitted to the fuselage and then epoxied into place.  Take note of the orientation too.  There are some small slots in the fuse to assist this.  The door opening/closing mechanism should be towards the front of the model.

First off in the servo area was to install the Spoiler servo (see photos).  The servo's control rod is threaded on end for the clevis which attaches to the air-brake mechanism.  The rod is passed through a coupler (ensure that the securing nut is CA'd in place) attached to the servo arm.  With the servo pushed to it's end point I then dropped the arm on to the servo shaft.  Lightly tightened the 3mm grub screw in the coupler and then operated the servo in the opposite direction.  If the throw is full then the screw can be removed, thread locked and tightened down.  Snip off the excess rod.

Next to the spoiler servo is the retact servo which is orientated crossways.  Similar to the spoiler servo the servo arm requires the fitting of a coupler.  Again a threaded rod with a clevis screwed on ten turns is connected to the retract actuating arm. Sliding the servo arm coupler on to the rod and then dropping the arm on to the servo shaft, ensuring that the servo is at it's full end of travel.

Verify servo direction befdore securing the rod using the 3mm grub screw and thread lock.  Trim off the excess rod leaving about 10mm spare for micro-adjustments if needed.  operating the gear servo we now check that the gear goes down fully and locks and the servo can pull the wheel back up and lock with no strain on the servo (buzzing).

Next was the rudder servo which operates the rudder using a pull pull system.  First off, I can tell you that the supplied arm's clevis holes are too wide for the rudder operation.  I found this out the hard way when I stripped two servo's gears out.  Secondly, it is also too thick for the mini clevis to stay closed.  Tut! Tut!  CMPro.  More custom work then?

Using the supplied closed loop ends I epoxied these into 2mm rod extenders.  Now I can use decent Dubro metal 2mm clevises screwed on to the extenders.  This method gives some adjustment too!  With the rudder control horns screwed into postion, these are lined up by the hinge line and the control wire exits in the fuselage.  Measuring the distance between the rudder horn holes (I opted for the centre holes) I transferred this measurement to the ally servo arm adaptor.  Drilled the holes out at 2mm.  Using the supplied closed loop ends , these were wound into the clevises and then connected to the rudder horns (middle hole).

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Using a pull-through to get the wires through the fuselage.  The other ends of the wire were threaded through the loop ends and brass wire crimps. With the rudder held neutral (centred) pulled the wires until most of the slack was taken up.  Crimped the brass tubes to lock the wire.  With the rudder servo centred the aluminum arm was bolted to the servos original arm with 2 x 12mm nuts and bolts.  Postioning the arm on the servo shaft as near as right-angles to the fuselage centre line.  Now I was able to screw the 2mm clevises in and out until their pivot pins just lined up with the 2mm holes drilled into the arm earlier.  The final fiddly job was to get a very light tension on the wires with undo strain on the servo at full rudder left and right and returns to centre (neutral) each time.

Now I was dreading this - making up the link for the retract to gear door.  You are supposed to use a small double ended threaded rod of 1.5mm dia or something (supplied like the elevator link) and two tiny clevises.  The manual states that you should make the length between clevis pins as 28mm.  No chance at all.  Because not only is this connecting job one hell of a pain in the ass and fiddly to boot you then find out that the link is too long.  In reality the link is shorter than that.  But even with clevises wound near on full together you still won't get the required length!

All I had to hand was some 2mm threaded rod.  Drilled out the tiny clevises to 1.5 mm and then forced, wound the clevises on to the rod which was only 15mm in length.  With the rod evenly wound into the clevises and about 6 mm of rod showing between the clevises's ends the clevis pins were now 28mm apart.  Now came the longest, cussing 15 minutes of time that I can remember for a while - Connecting the link to the gear door and the retract.  Believe me, this is a most annoying fiddly job you could ever wish for.  Be aware!

Time for something less annoying to do!  The cockpit and fittings.  The tinted plastic requires trimming, also the cockpit base.  There are lines to follow but these are just a guide.  You need to get both items trimmed nicely so they fit together perfectly.

In a small plastic bag came some laser cut ply parts, some slotted and some shaped.  Following the manual, well a sort of sketch on how it should look like, you have stack these ply parts along with the canopy locking pin in to something that resembles a locking mechanism.  Be careful not to get epoxy into the sliding lock pin!  There is two other ply items, one slotted and one plain about 25mm x 18mm square.  Along with a piece of 2mm x 25mm rod these when epoxied together become the front canopy securing pin.  Again, only a sketch is given so you have to assemble according to common sense!  However, once the cockpit is assembled, a self-adhesive decal for the instruments is supplied but no "Idiot"

Remember, that locking mechanism you glued a while ago?  Well it's time to epoxy this little item in to the top of the fuselage - a slot has already been cut for the finger pull.  Here you are on your own because the manual gives no guidance or tips on fitting.  I found that after ensuring the lock pin protrudes enough and gluing that some dremelling of the GRP was required too.

In my case I could not find any ply items resembling a backing plate for the cockpit plastic that the lock pin could engage into.  Again iIhad to create one of my own from 3mm ply.  Even then this a rather a fiddly, time consuming job to get the canopy to fit neatly and stay secure.

Airbrakes - Spoilers.  Earlier in the article I said I would leave this till later during the build.  The reason was that I wasn't keen on the way they were operated and trying to fit the wings and the control rods on a hillside in windy conditions did not feel very appealing.  I was trying to source some electric "Graupner style" spoilers from Germany.  But in the end decided to try what came in the kit first.  No point in spending more money in to the project before it's even completed.

Why they are supplied in red plastic one wonders when the wing covering is white!  The spoilers are operated by a pull rod hooked into the spoiler slide, the other end is secured, on fitting the wings, into the fuselage's mechanism and locked using 4mm grub screw.  What really needs checking here is that the spoilers deploy without binding at all and fully close up.  The manual displays a picture of how to bend the control rod at the spoiler end.  No different really than right-angle bends into servo arms and similar.  Getting the right length though is CRITICAL.  Once the spoilers have been epoxied into the wings and the wings temporarily fitted the rods should just pass through the couplings in the fuselage with rod fully pulled in and the spoilers closed.  (See photos)  Imagine what could happen if just one spoiler lifted slightly.  You would be fighting the glider down to land with difficulty.

With the spoilers closed there is still some 6mm of slack still left in the linkage and this must be accounted for when trimming the rods.  (Any slack left in the spoiler system could cause the air flow over the wings to suck the spoilers out a little andmake the craft very difficult to fly)  Also they must not have too much out the other side of the coupler other wise binding will occur with the pivot arm mechanism and possibly strip the servo gears.

I could use the ailerons as brakes (flaperons) and may just do that if the spoilers cause problems.  The surface area of the spoilers are about the same as the area of aileron!  Or could just retro fit some big flaps inboard and servos!  Albiet the model then wouildn't be scale which defeats the object of the exercise.

There is no guidance to where the receiver should be located but the battery pack will need to be up in the nose area to help with ballast and CG.  I am using the popular AR500 from Spektrum which is small and light.  A full range 2.4Ghz receiver compatible with my JR DSX 9.  I had thought about locating it in the to Tow-Release servo position but decided against this in case I wish to install a tow-release at a later date.  Or an outrunner motor and folding prop!  I have opted for the unused space alongside the retract servo.  I glued a piece of ply over most of the spare hole leaving just enough room to pull leads through if required.  Then located the receiver using Velcro.  With the servo wiring connected and secured down with small cable ties it will look neat and tidy.

To get the starting C of G right it needed 400 gms hard up into the nose cone to balance out the long tail.  The battery pack is only 113 gms so the rest was made up of metal weights.  Even with a tow-line servo of say 45 gms that still leaves about 242 gms of ballast to make up
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Now waiting on favourable weather for a maiden up on the slopes.  This will also confirm if the "not so quick" method of fitting the wings on the hillside is proved.

Update:  3rd May 2010 with a reasonable but cold north-easterly the ventus was maidened.  With only a little rudder trim needed and 8 ozs of ballast in the nose she flew wonderfully.  Spoilers worked great too, our test pilot Mike had only to use half deployed brakes to gently her drop to the grass.  Removed some 3.5 ozs of ballast and re-launched.  A lot more responsive now but at this balance only a experienced pilot should fly.  Wonderful scale glider to see flying.  Fitting of the wings and spoiler connectors wasn't too bad after all but a little patience still needed and a pair of long nose pliers to push the brakes rods fully out before locking the grub screws.

Conclusion

Flying this scale model does need some good experience of glider fliying as can be very quick and will need carefgul us eof control surfaces

Pros:

• GRP fuselage with decals sealed under gloss coating.  Smooth finish
• Traditional balsa/ply wings covered in a heavy duty film.
• Retractable wheel
• Nice cockpit and canopy
  Cons:
• Many of the small plastic parts leave a lot to be desired.  Best use your own branded parts.
• Gear Door a little flimsy and a swine to get working correctly with the retract.
• Odd sized threaded rod.
• Spoilers to be glued in?  Better screwed then easily replaced.
• A lot more finishing work required for an ARF than meets the eye.
• Assembly manual typical CM Pro.  Minimal and ambiguous.

 

Value for Money? Fairly good.  I paid £116.50 for mine but with the weak pound against the Chinese currency now hovering around £118,95 and upwards.  An upmarket scale model could set you back three time this price!

Construction Level? Intermediate modelling skills.  You will need some fair experience and patience.  Good supply of your own little parts, clevises, threaded rod, etc



Not Recommended



















*** The conclusion is the opinion of the author and not necessarily of WMAC or  it's members

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