Merlin Build

Some Build notes
Why?
With both the Willow and Merlin now available it’s about time that I posted some notes on the Merlin build as well as the Willow.
  My Thanks to Martin for his pictures.  The Willow and Merlin builds cross over quite considerably and so does their description. 
Wiring
  First things first and it’s time to get the Wiring loom made up.  This is very very standard stuff, 4 * 1m servo extensions and a couple of 6 pin multiplex connectors do the job nicely.  T9 now has a purpose built Merlin loom available.
  Slots are already cut in the fuselage and wing to mount the connectors.  My preference is to open the hole up in the wing root a little and leave the wing connector loose.  I also tend to leave just 2-3mm of the connector poking out of the fuselage.  This is for no better reason than in case it comes loose while connecting things I have a better chance of rescuing the connector from being lost inside the fuselage
  One thing to remember is that when you are assembling your model your servo tray and ballast tube may get in the way of the leads, so they won’t have a direct route to the receiver- a little extra length solves this one.
Fuselage
  The fuselage on the Merlin is a canopy design and this helps to make it a simple build.
  The servo tray adds to the fuselage’s strength as well as holding the radio gear and ballast tube.  I like to make my Servo tray stretch from level with the wing joiner to near the front of the canopy- leaving just enough room to slide in your battery pack but also nose weight.  This is more than is necessary but makes a very strong structure.

 
Cut out  the slot for the ballast tube, servos and receiver before fitting the tray.  The CG of 98mm means the ballast tube will end under the canopy and allow easy access.


  There is plenty of room for a range of servos within the fuselage.

Incidence pins.
  The Merlin is unusual in that the incidence pins are in the fuselage rather than Wing.  Carbon rods are supplied.  These should be fitted in the fuselage and cut so that each pin extends 10mm from the fuselage.
 Tail-
Merlin/Willow
  Although the Merlin has a lower set tail that the Willow the fitting it the same.

  I have left the Willow pictures in here as they do and excellent job.

  First job is to cut the joiners to length and glue them into the fuselage. The Joiners need cutting to an angle in order to fit smoothly to the side of the fuselage.



The tails will slide on very easily and butt up to the fuselage.



Rather than fitting through the bottom of the tail (as with the 1 piece tail) the horns fit into the ends of the elevators. 
The easiest way I have found of doing this is to glue the ball link into a brass tube with a 2mm internal diameter, I find pieces of 60mm long are about right.  Put the tube in a vice and bend it at the correct angle.

For the Merlin this is 10mm from the ball link.  The tail is set at 105deg so around 35 to 40deg bend works well.  A couple of trial fits will show you if you have enough elevator movement.



  The once you are happy with the position of the horn bend the last 12mm for that it points towards the trailing edge of the tail.  You may need to drill a hole in the elevator sub spar to accommodate the end.  Fix in place with epoxy on micro balloons.
 
 Once set the tails can be fitted onto the fuselage and the ball links connected.
Wing
  This last bit is certainly the easiest part of the build.  With horns fitted it really is a just a case of gluing/fitting in the wing servos.  A number of pilots have added to teh epoxy and mircoballoon mix which holds the flap and aileron horns in place.  This is a simple job to do with epoxy and microfibres or a length of glass colth at the start of the wing build.  

  My photography isn't up to showing this but I have now started to bridge the top and bottom skins with blue foam blocks at the side of the servo hatch.  This is very easy to do and reduces any wing skin flex in high winds- so I tell myself any way.

  Although you can use HS85’s there is enough space for a whole range of servos.

  It's a shame to go to all the effort and expence of good servos for the linkages to allow for slop in the controls.  A small dab of cyano and then kicker will fill any gaps on the horn/clevis connection.  Move the controls with the servo turned off and after a 'crack' you'll find a slop free connection.
Ballast and flying

  Ballasting a model is largely dependent on the conditions and type of flying you do.  I have 380mm of ballast cut into 10 equal pieces.  The ballast is made from 19mm B&Q chrome shower rail, cut up with a plumber's cutter.
  After sitting the sections of tube on a tile/heat proof surface, I fill the pieces with lead.  Usually twice to fill the bit of reduction from the lead cooling.  This is an easy job but it's probably best not to let the missus see you doing it on the new Hob or letting your 4 year old pour the lead (trust me I know).
  I have a page of example settings as a start point but please contact me with yours.  The Willow's settings can be changed around to experiment with little fear of being 'bitten'.  Have a go and get a set up you like.

Flying and Set- up

    The Merlin has a very low incidence setting, on a first launch you'll see the model simply heading in the shallow dive that we're all told to launch at.  A touch of up elevator from your thumb and she will go straight and level.  In setting up your Merlin the simple rule that the model will fly straight with out any thumb in-put is a guide.

  Settings are a very personal thing but a CG at 100mm
 Elevator settings of 9mm each way (measured at the root)
Aileron throws of 22mm up, 15 down and around 3mm of snap flap. 40% of the up throw in crow
Flaps of 5mm up 3mm down and as much CROW as you can get

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