Page 37 - MFWDec 2023
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to my knowledge, the Enya 41-4CD and the Enya 36-4CD
     V        intage                                          Far  more  common  are  glow  plug  4-strokes  running  on
                                                              - if you can find them. They are rare and expensive.


                     SIG                                      methanol.  The good news is that these can be converted
                                                              to spark ignition and petrol. Saito even make a petrol 4
                                                              stroke ready to go.

                                                              Razvan Rocus in the MAMS club has an excellent article
    2024 Nationals.                                           on  his  conversion  of  an  ASP61AR  here  for  those
    We are trialling a new approach for the 2024 National that   interested. This engine ran beautifully in his scale
    will be much more like a Rally.  The main reason for this is   Tiger  Moth.......................................................................
    so  that  fliers  can  enter  more  events  by  avoiding  event   https://www.mams.org.nz/aircraft_petrolconversion.html
    clashes and overloaded days. It is also intended that the
    new format will better serve those who are unable to attend   Bryan Treloar has been very successful in Open Texaco
    for the whole Nationals period.                           events using an old OS61FS converted to spark. Here are
                                                              Bryan’s  comments  on  his  experiences  with  his  spark-
                                                              converted 4-stroke for Open Texaco.
    With the Vintage RC events, you will be able to fly them on
    any of the four competition days, not just a specific day as
    in the past. In Vintage FF there are four events that can be   “I have explored the versatility of spark ignition to venture
    fitted  into  your  schedule  on  whichever  day  is  most   into  the  Open  Texaco  class  as  I  felt  a  suitable  spark
    convenient to you. This allows flexibility when planning a   converted four stroke engine would be a very fuel efficient
    Nationals visit and gives the chance to see and participate   combination.  I  read  about  Otto  Bernhardt  in  USA  who
    in other events that might have otherwise conflicted with a   specialised in converting two and four stroke engines to
    fixed schedule. You will even have the opportunity to pick   spark ignition using a cam and points operated system
    the weather that suits you and your event the best.       rather than the more common CDI or Hall Effect ignition
                                                              found in modern conversions.
    A side effect of the rally format is that we are now able to
    offer  almost  all  events,  both  RC  and  FF,  with  fliers   I had the good luck to find a converted OS 61 four stroke
    choosing to fly what they want, when they want. However,   on Ebay and I bid on it and won the auction. When I got the
    note that you must have entered and paid before you come   engine, I set it up on the test bench and experimented with
    to the field to fly. It is recommended to do this early, on line,   propellers and fuels to get a set-up that worked well.
    to avoid the frustration of not catching the Nationals office
    when it’s open and staffed.

    The other good news is that the first six entries in either FF
    and RC vintage are all you need pay for (12 total). Extra
    events have to be officially entered but don’t pay for these.
    We would like to see as wide and numerous entries as
    possible, so bring everything you have.


    What is the best Power source for Vintage Open
    Texaco?
    Despite  being  the  most  challenging  of  our  IC  classes,
    Vintage Open Texaco is very popular. The event calls for a
    limited volume of fuel to achieve 15-minute flights. Those
    who fly this class look for the most economical engine,
    whether it be glow or diesel, 2-stroke or 4-stroke, spark or
    glow ignition.


    A look at fuels suggests that more energy, for the same
    volume,  is  available  from  diesel  and  petrol  than  from
    methanol. As for motor types, diesels are usually more
    economical  than  petrol,  and  4-strokes  are  more
    economical  than  2-strokes.  Diesels  run  higher
    compressions  so  have  better  efficiency  as  a  result;  4-
    strokes scavenge burnt gasses from the cylinders more
    efficiently  than  2-strokes  so  have  more  complete  and
                                                              Bryan  Treloar ’s  spark-
    efficient combustion. These generalisations are supported   converted  OS61FS  bought
    by experience and experiment.                             off  E-Bay.  It  uses  points
                                                              rather  than  the  newer  Hall
                                                              effect  system,  presumably
    So,  what  would  be  best  for  Texaco  events  where  fuel   because  spark  ignition
    economy is the key to a long engine run? Logic says a four   engines  may  have  only
                                                              points-operated  ignition  for
    stroke diesel, but there are just a couple of these available   SAM USA.
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