Ripmax Mustang P51D EP

This article focuses on the build of the Ripmax Mustang P51D ARF as a "Winter Build" to stave off boredom due to inclement weather.   An addition to their range started with the classic Spitfire a few years ago and now includes the ME109.

 All these models come in at a bargain price of less than £99 GBP and the Spitfire has been seen around for £72 GBP.  Designed for electric flight, light weight and can be kept in the back of the average car for those quick flights.

 

Update: As of November 2012 on offer at around £60.00GBP.  Model is now discontinued...

With the need for just three mini servos, an ESC, choice of Inrunner 600 can or Outrunner( Modification Req) with battery power of just 11.1v volts (3S 1P 25C) an economical scale look model that looks the part in the air.

This build was inspired by WMAC member, John Bainbridge's Ripmax Spitfire. (Now Discontinued)  along with the Me109.

Read on.....

It comes in a large long box, 49 inches (1250cm) to accommodate the assembled main wing and in the one used here, well packed and items covered in plastic bags. The instruction manual is a dream, obviously written by an Englishman rather than translated Chinese!  With colour photos to assist the final assembly.

 

 

The model has a wing span of 47 inches and covered in silver film with invasion stripes.  Constructed of ply formers and balsa with reasonable detail lines in covering which appears to be good for a cheapy.  Being extremely light I did consider using it as a sloper but possibly not strong enough to take the knocks of hillside landings.

Total all up flying weight is about 3 & half lbs.  Strange though that Ripmax still kept the design for power by 600 can motors in the nose, maybe okay when the Spitfire was released a few years ago but things have moved on since with falling prices of light and powerful Outrunners.  Still, modifying for outrunner was no problem as you will learn later.

Mainly through habit I tend to view all the parts first and imagine how it goes together.  This maybe because of those unfollowable MFI furniture flatpacks instructions, I don't know!

For this build I opted for:

  • E-Max BL2820 920Kv 400watt outrunner    (A .32 - 2 stroke equivalent)  GiantShark RC  £16.95
  • 60amp ESC Hobbywing (all I had to hand)  GiantShark RC  £33.47
  • 3 cell 1pack Lipo 25C-30C (11.1v) LoongMax 2250    GiantShark RC  £23.55
  • 3 x HiTec HS81HB's  GiantShark RC  £43.00
  • Spektrum AR500 2.4Ghz RX  Channel Four Models  £36.77
  • Ripmax 2.25 inch Spinner  Channel Four Models  £1.55
  • APC-E Prop 11x7  Channel Four Models  £4.49

Total Value = £258.78

Note: Some items I already had to hand

Othe requirements were CA thin, 4 minute epoxy.

Main Wing Assembly

The ailerons are pre-fitted but don't let it fool you, they are NOT glued.  The manual says therr are four for each side but in fact there is only three but this adequate. They are those CA  plasticky hinges which are more than adequate for this model.  The first aileron I pulled fully out to glue the hinges in but regretted that.  Trying to get all three back again was a nightmare.  I had to open up the slots a little more, get the hinges engaged and then working very quickly applied CA thin and push them in leave a 1mm gap.  a small amout of epoxy was applied to the torque rod at the same time.  On the second aileron I pulled the hinges nearly out, applied CA and located them real quick!  Success.  Very handy having a micro dropper too for accuracy!

Cup of tea time to let adhesive set somewhat!  Next job was to glue the ply servo cutout to wing slot.  Even withthe mini servo I still had to chip away some wing material to get the servo to miss the bottom.  Also dig out a tiny slot to get the servo cable out again. (Chinese always forget that!)

The torque rods already have the clevis links installed but I found that some balsa needed to be chiselled away to allow full movement of aierons.  With the servo installed and centred, it was just a matter of screwing on the "metal clevis", place a 90 degree bend in the other end and secure using the plastic clips supplied.  Wing completed!

The Fuselage

The stabilser and fin are separate items wrapped individually in plastic bags.  They need to be installed and glued in the correct sequence.  The stabiliser slides through a pre-cut slot but the elevator needs to be passed through FIRST before final install!

Note: If you forget the above sequence then don't panic.  You will have to carefully continue the slot right to the back of the fuselage.  This will enable you to install elevator.  You may chooose to fill the extended slot with a piece of spare balsa and cover with some spare film or just leave it.  I have built three of these models and I too, forgot the sequence of install and I just left the slot open - it's not very obvious anyway!

Sliding the stab through verify correct location and mark position with pencil.  Pull out and carefully cut away film to expose wood.  With the elevator loosely installed slide the stab back through and glue with CA Thin.  Simple enough.  However the trouble I found was getting the elevator hinges to line up, not enough room in the slot for manoeuvrebility.  In my case I had to carefully cut the fuselage slot right out to the rear to retreive the elevator.  Once this was done it was easy to glue and fix in position.  Fixing the fin was next. Again slide into position mark film and peel away.  Install using CA Thin.   Pre-glued hinges on rudder side only.  The rudder is hinged in three places, two in the fin and one in fuselage tail.  Again had to open the slots just a little to get the hinges to slide in equally.  The manual recommends running CA Thin or Medium glue along the joint between fuse, fin  and stabiliser.

 

 

 

Hardware Install

The kit supplies two snakes for rudder and elevator.  The guides are pre-installed.  Threaded 2mm studs are supplied to screw into the snake ends once the lengths has been determined.  Again metal clevis's are used to connect to the control horns and servo arms.

Installation of the HiTec HS81HB's was simple into the servo tray.

The engine mounting in designed for 600 class Can motor.  Yuk!  To get round this I made up two wooden blocks (see last photo in first gallery) and leaving a 6mm gap between them fitted the outrunner's supplied aluminium mounting to the blocks to get a sliding fit on the models engine mounting.  Then I fitted the motor and prop adaptor and temporaliy slid the lovely fibre-glass pre-painted cowl into its position to get an idea where the block needed to locate. Also ensured I followed the line of right and downthrust built into original mounting.  Once happy with the fitting, secured with epoxy resin.

With the amount of torque and belly landing likely to be applied I made up some triangular motor mount fillets to help spread the loading across a larger surface..  I made up some bigger versions and added these on top to spread loading more across the firewall.  Lots of epoxy here too!

My ESC had quite short leads so the controller had to sit in the space just behind the motor and above but at least it sits in a good airflow for cooling. (The manual shows the ESC in battery bay.  Um!  Not standard I would say - probably leads have been extended)

The battery bay is accessed by a top hatch which is held in place with pre-installed magnets which only allow you to put back the right way round!  The bay is spacious allowing for NiMh packs and as well as high capacity LiPo's up to four cells.  This long battery bay is a very helpful in allowing for CG balance point to set by moving battery forward and back.

The cockpit bubble is clear plastic and is secured by three self tapping screws.  The interior of the cockpit is painted black and if your picky a pilot bust would finish off nicely - I didn't have one at that scale to hand!

Final Stages

Before final fitting of cowl time for run-up test.  Recommended prop sizes were from 10x7 to 12x6 for motor.  At half throttle with 10inch prop current draw was about 12 amps and at WOT 23 amps showing around 258 watts.  The pull from the prop in my opinion wasn't strong enough.  It may have been okay decided on a the middle ground - 11 x 7 APC-E.

Wow, what a difference!  Half throttle the model was really pulling against me and at WOT gave me around 348 watts at 36 amps.  The roar from the prop sounded good too!  It was jusr fighting to get away.  So, 350 watts at 100 watts per pound quite adequate.  I haven't tried the 12 x 6 at this time, a maiden is required first.  Although feasible this size prop would pull 420 to 440 watts and would need good throttle management.  Plus flight time would be greatly reduced unless using 4000maH batteries which I haven't got!  So, for now stick with middle ground - 11 x 7.

The beautifully painted GRP cowl is secured with four small self tappers.  The spinner is something else!  Awful and rubbish.  Wooden backplate and uncut plastic nose cone.  Found Ripmax do a backplate type and CH4 promptly ordered these in, in RED to match cowling front.  (See Photo)

Modifications

The Spitfire belly lands nicely due to its fuselage shape plus missing radiators but in the Mustang's case there is a problem - the oil cooler air scoop.  When the model is sitting on the ground it is tipped nose down due to this protrusion.  Prop might dig in too and break.  Um!

My answer to this minor detail was to glue a wooden block on to the bottom of the firewall and made up from a spare wire under-carriage a sort of nos eleg that isn't too obvious but will keep the nose up on landing.  The wire is 4mm steel with a nice rounded bend at bottom to enable easy sliding on grass. (See Photo)

Note: A lovely lady mascot decal does not come in the box or it didn't in mine anyway.  Not a problem, I do have some printable vinyl and suppose I can create my own mascot.  Download an image from the net and edit/print or maybe one of the wife in bra, silky pants and  suspenders - Ouch!  I was only joking darling.  (No I wasn't!)

The Mustang was maidened on Sunday 14th February 2010 on a cloudy, part sunny day with light winds from north across the field.  Test flown by Dave Bright who reported very little trims needed.  That's good - mechanically the control surfaces where well aligned.

Not fast but scale speed but a dream to watch fly by.  Very stable with ample power.  Dave took it through rolls and half-loops and loops and later tried to get it to knife-edge but not quite so successful there - possibly more rudder movement needed if required.  He loved it and said he would recommend it although you do need to be "with-it",  ie; doesn't fly itself but this the characteristic of warbirds.

Update: 10th April 2010.  I have since flown it and found it very comfortable to fly as a fairly new pilot, predictable characteristics and with an adjustment to rudder horn will now knife edge. Rolls can be made fast and slow and landing is long glide in.  Flys well too in breezy conditions albiet using more throttle more often to keep authority!

Conclusion

  • Value  8-10
  • Build Quality  7-10
  • Ease of Assembly  6-10
  • Covering  7-10
  • Eye Candy  9-10

Skill Levels:
Build Level  -  Novice builders under supervision and upwards experience.
Flight Level  -  Intermediate Skill

Read Me -  Update: January 2013

The later ARF models now have a modified motor mounting, a box section designed to only accomodate 600 can motors.  At first glance I would suggest the box is completely removed and a new one created from ply to take the X mount for the brushless motor.  The X plate need to be mounted 1 7/8ths inches (48mm) from firewall.  When I get round to the mod in early 2013 I will update this article.

Update: November 2014

I am using the Emax 2812/07 running on a 4 cell using a 11x7 APC-E prop. Power output approx 680 watts.  Had to adjust the down thrust a little (wanted to climb when opening throttle like a helicopter).  Flies like it's on rails, not ballistic but like a powerful warbird should do.  Half throttle most of the time and much extended flying times too.