SETTING UP THE GREAT PLANES VIPER

 Andy Luckett

I have compiled this information after two seasons of running and maintaining the four Cowra Team Vipers.  There are probably things I haven’t discovered yet and better ways to do stuff.  A lot of the info here has come to me via the generosity of other competitors.  All of what is offered here is tried and tested and known to work.  I am passing on this information so that you may be more competitive in Sport Pylon racing.

  • Set wing incidence.  Use Robart or some such incidence meter.  To do ‘v’ tail use a flat piece of board about 150mm square.  A 6” wall tile works well as it has enough weight to sit still.  Place it in the ‘v’ of the tail and it will give the incidence. Just use the meter as if the tile was a wing.  Incidence should be zero - zero.  Trim the wing mount in fuse if it needs altering.
  • The ‘v’ tail unit doesn’t have much glue holding it together.  Strip off a bit of covering and epoxy it in place.  Use the screws to hold it till the glue sets.  Get incidence correct.  Hint don’t loose the wing mount screws, they are some weird thread and you won’t get replacement ones.  Keep the ones from dead Vipers.
  • Servo, Hitech 225BB or similar mini servo with at least 3kg of torque.  Don’t be tempted to use micro servos such as the Hitech HS 81 on anything other than throttle.  They don’t have the torque and also the nylon gears will fail.  For the RX use JR 600/700 or Hitech 555 or some other small receiver.  Battery, small - Master Instrument 4/HR-AAAU which is a 650 maH AAA NiMh.  Try not to use the little 270 maH ni-cad packs as their charge needs to be constantly monitored.  It is best to use a switch with external charge socket so you can charge up during a meet without removing the wing.
  • Check and beef up glue joints around wing mount plates in fuse as the front one in particular can come loose.  Also keep an eye on the fuse beneath the front wing mount as it can crack after extended use.  Good idea also to use bit of ¼” balsa to make wing seat wider or it cuts into wing.  Be sure the rear servo, RX, battery mount is glued in well.  You might also consider beefing it up as it has been known to move/crack where the larger servo slots are cut in.  If it fails in any way the elevator starts to act strangely.
  • Some blokes drill and install dowels (bamboo skewers) to anchor through the fuse sides into the firewall as it can come loose at the most inadvertent moment.  It took a while but I had to do it eventually after wondering why my engine wouldn’t reach max revs and I blew two rounds.  Another option is to saw in horizontally and epoxy triangle bits of 1.5mm ply in the corner of the fuse firewall joint.  Two per side.
  • After half dozen flights when wing mount screws have bedded in run thin CA into the countersink in the wing to stop the hard point continuing to crush.
  • Always use sticky tape over the wing screws.  They have a bad habit of backing out in flight.  In fact use sticky tape on all the hatches instead of screws. Streamlining you see!
  • The supplied wheels look great but come off the brass boss in flight.  There is some way to glue them on, but I don’t know the details.  Better go to http://www.darrolcady.com/ and order a set of streamline wheels and axels to suit.  Also get the spinner nut to suit the TT Pro 46.  In fact get two of everything and do a bit of online shopping while you’re there.  Spend some money.  It is a fun site.  You can be modern and use your Paypal account at Darrol’s shop.
  • While on web go to http://www.nswpylon.org/  .  It is the NSW Pylon Racing web site.
  • The TT Pro engine.  Run it in leaned out.  Well just backed off a tad, just so it won’t sag nose up.  Not rich at all.  Remember it’s ABC and needs to be run in at full revs and full operating temp.  Once it is tuned run it in flat out in the air.  One tank on the ground is probably too much.  Caution is don’t over lean it.  If to lean it will sag in a full pylon turn.  In fact the way to tune the motor (unless you have S.J. Barber as your pit crew) is to set it so it just doesn’t go lean and sag in a snap pylon turn with half a tank of fuel.  These donks are durable and will run hard for a long time if treated right.  Because they run on castor fuel they will carbon up over time and it needs to be removed somewhere down the track.  I’m not going to detail how to do it as it is a delicate operation and anyway there is too much bullshit around about maintaining the internals of a model aircraft engine. 
  • The fuel is 20% castor 80% methanol.  Use this in the donk from day one and nothing else.  You can by it ready mixed.  Both the major Aussie fuel makers do it.  Or make your own using Hot Stuff castor which is supposed to be de-gummed, whatever that means.  The plugs to use are Enya #3 or OS #8.
  • The muffler is the Achilles heel of the TT Pro.  The thru bolt snaps, it falls apart in the air, you loose all the bits spread up the field and a new one costs $38.  The tricks are:  a) Safety wire the whole unit together so when the bolt breaks you don’t loose the bits.  b)  Use JB weld (from Kellett’s) to glue the whole muffler together.  c)  Replace the thru bolt with a length of 4mm stainless threaded rod, lock nuts and spring washer.  This is probably the best option.  You can get the rod from a good nut and bolt place such as Lee Bros in Nth Parramatta. d)  Use all of the preceding.  e)  Have the muffler TIG welded together.   NB. Whatever you do you must leave the baffle in as its part of the rules.  You must also leave the head gasket in as its part of the rules.  It’s basically an honour system, but nobody bothers to cheat, as that’s not the spirit of the event.
  • The fuel tank may blow out on the odd occasion.  Thunder Tiger make a 4oz tank that will fit.  Kellett’s the event sponsors can supply them.  They also have the RAM 10x6 prop which everyone likes.
  • Above all remember that your model must be safe to fly as there is great risk of damage to people and property in pylon racing.  Take care to do the maintenance and you will be rewarded.

 

That’s it.  Happy Vipering.

ANDY

If you would like to contact me e-mail luckett@westserv.net.au and I will happily respond.