Final Build Update – 24in Miles M.18

Final assembly and details. Landing gear, noseplug & prop assemblies.  We’re ready to fly!


  Restoration M.18 version completed
  M.18 undercarriage details
  Forming the reed LG “stirrup”
  Trial Assembly to ensure proper fit
  M.18 prop & noseplug assembly
  Scottish Air Museum M.18 model
  Kings Cup M.18 completed
  Miles M.18 on skis
  Designer Tom Nallen’s M.18 ca 2006
  Kings Cup Miles M.18 model ready to fly

View/Purchase Miles M.18 24in Wingspan Plan


Hi all, it’s a new year.  Hope your 2021 is going well so far. 

Things slowed down a bit over the holidays, but our modelers have finished their Miles M.18 models and they’re ready to fly.  In this update, we’ll touch on details, final assembly, noseplug assembly and specifications.  This will be our last build update.

 

Details

We closed the previous update discussing the Landing Gear leg wire installation in the wing.  Now lets look at how one of our modelers fabricated the scale LG legs using 1/8in dia reed.  Short lengths of reed were split in half and soaked in a shallow basin of water overnight.  The pliant reed was then hot-bent around a soldering iron to form the unique stirrup-shaped undercarriage legs.  A .020 hole was drilled in the top center and a groove etched into one half of the inside edge to fit the music wire leg.  Before cementing the stirrup in place, short lengths of full-section reed, plastic straw and nylon brush bristles were used to fabricate the upper shock absorber portion of the LG leg.  These pieces were slid over, or slotted and fitted onto the music wire leg.  The stirrup was then fitted to the lower part of the wire LG leg and cyano’d in place.  The finished LG leg assemblies were carefully sprayed with silver Krylon before the wheels were installed.   The wing surfaces were carefully masked to keep any silver overspray off the tissue covering.  

The Kings Cup M.18 wheels were made up of 1/8in sheet balsa cores and 1/8in thick foam tray sides.  The wheel disc and rim was embossed onto the foam sides using a heated 7/16in socket with a 3in extension.  Holding the extension in the hand, the socket was heated and gently pressed/turned onto the foam sides to form the wheel and rim.  The outer edges of the wheel were shaped to a rounded section with a razor and sandpaper.  The wheels were bushed with small diameter brass tubing, the discs covered with silver tissue and the tires painted black to finish.

Both modelers added details per the plan and photos of their aircraft modeled – windscreens, exhausts, airscoops,  headrests, etc.

Final Assembly

Final assembly was straightforward with this model.   Both modelers did a trial assembly with the covered components to ensure proper fit.  Some sanding of the fuselage wing saddle was required to get a seamless fit with the wing center section.

Noseplug & Propeller Assembly

The final step before initial flight testing with most models is completing the noseblock or noseplug assembly.  This includes the thrust bushing, the propeller bushing and free wheeler.

The Kings Cup model’s noseplug was drilled with several degrees of down and side thrust and the thin-walled 1/16 O.D. brass tube used for the thrust bushing .  The round noseplug will not be keyed until after initial flight testing as it may be rotated slightly to alter the down and side thrust mix.  A modified 9.25in dia Czech P-30 prop was bushed for a Henry Struck tube-in-tube setup and a turned balsa spinner fitted.  A simple latch free wheeler was installed on the prop and the noseplug assembly was completed using a .030in dia music wire prop shaft with a “figure eight hook” and an external winding loop at the front of the spinner so the motor can be wound with the noseplug and propeller in place. 

Completed Model Specifications

Despite some significantly different approaches being taken – especially in the covering and tissue finishing areas – the models came in at essentially the same weight.  The Scottish Restoration M.18 model weighs in at 30 grams without motor, while the Kings Cup model finished out at 29.3 grams.  With 110 – 115 sq in of wing area, the wing loading is below .30 g/sq in which is very light.  Both models should have the potential for high performance. 

As mentioned earlier, the Kings Cup model is fitted with a large 9.25in dia prop.  It should fly with a 2 loops of 1/8in Tan rubber motor about 30in long before braiding.  A shorter motor will be used for initial flight tests.  

The Restoration M.18 model is fitted with a 7in Peck propeller and inital flight testing will be done with an 18in loop of 3/16 Tan rubber.  One reason for the smaller prop is that this modeler has fitted his M.18 with skis and intends to fly it ROS (rise off snow).  Wow, can’t wait to see that!

Closing the M.18 Build

Well, it’s been a lot of fun following these builds over the last couple of months.  We hope the different approaches and techniques shared were helpful as well as the pattern downloads made available.

To close, we’ve dug up a photo of designer Tom Nallen 1’s original model from 2006.  It’s a beauty, and yet another illustration of how each modeler inevitably makes his or her model their own.  One of the true joys of scale modeling.

Build Update #3 – 24in Miles M.18

Tissue covering & markings, Cowling and Landing Gear installation – we’re closing in on finishing this model!

 


Preshrinking tissue
Markings applied to chalked tissue panels  (view video)
Covering with CoverGrip
Covering wing undersurface
Sheet balsa cowl side panels
Vellum cowl fitting & installed
Installing LG wires with plywood doublers
Tyvek alternative; a vertical gusset at the back of LGM to rib W2 is yet to be added
Tissue covered M.18 fuselage with markings applied

Well, it’s been about a month since we’ve started building our 24inch wingspan Miles M.18 rubber powered flying scale models.  Already, we’ve got a couple of ships nearly ready for that first test glide.

Our modelers continue to improvise a bit as they go, and as always it’s interesting to watch this play out. 

Preparation & Covering

Proper preparation is the secret to covering any framework.  There is a sequence that leads to a good looking and flying model at the end.  Sanding the framework and scalloping formers between stringers to smooth raised spots that will cause wrinkles in the covering later on is important.  Pre-shrinking tissue, applying color and markings are part of the preparation process too.  

Right off, our modelers chose different color schemes, methods and techniques.  One modeler chalked his tissue light cream color (video) for the Kings Cup scheme specified on the construction plan, while another used white tissue to replicate the restored M.18 displayed at the Scotland Museum of Flight.

Both elected to pre-shrink their tissue covering to reduce flying surface warps – one shrunk the tissue on a traditional wooden frame and the other used a common window screen. 

Their paths really diverged when it came to adhering the tissue to the framework.  One chose a more traditional thinned white glue (70/30 water – Elmers mix) applied to the frame with a brush, while the other used Deluxe Materials Cover Grip (thinned 50/50 with water) applied with a covering iron.   Both used cut tissue markings, applied with either spray cement or thinned Cover Grip.  The Kings Cup markings were chalked to deepen the color and applied to tissue panels before the tissue was applied to the framework.  A final finish coat of Krylon Satin #1323 was used on the Kings Cup model, while Deluxe Materials EZE Dope (thinned 80/20 water – EZE Dope) was used  on the Museum of Flight M.18 model.

Cowling Installation

The Miles M.18 construction plan doesn’t specify a 3D cowling, but both modelers added cowl panel detail to make the model more realistic.  One modeler used light sheet balsa side panels shaped to contour, while the other used a tissue over vellum approach. In the sidebar photo, note the effective use of hairclips as clamps to secure the sheet balsa to the fuselage framework while the cement cured.

The drafting vellum cowl uses 1/16 square balsa doublers at the first two fuselage uprights  which, once sanded to shape as formers, provide support for the wraparound cowl.  Once the cut vellum cowl was fitted to the fuselage nose, cream chalked tissue was adhered to the vellum with a spray cement.  The fuselage framework was covered and then the tissue covered vellum cowl attached to the nose formers with Sobo Craft Glue.  A trim iron set to low heat was useful to cure the Sobo when installing the vellum cowl.  This approach eliminated the need for the lower cowl balsa block, but a former  is required at the crosspiece just aft of the noseblock.  Rough patterns for this former, the vellum cowl panel, and the cockpit sheeting are provided in the download at the end of this post.

Landing Gear Wire Installation

The M.18 model has wing mounted landing gear wires which must be installed securely to withstand the strain of hard landings.  Here our modelers followed the construction plan, cutting the mounts LGM-R and L from medium-hard 1/16 sheet balsa.  A 1/32 sheet balsa doubler was found to be helpful on the underside of LGM which when sanded faired nicely with the wing Leading Edge.  The .020 music wire legs (right and left) were carefully bent per the plan.  After the wing underside was tissue covered, the wire LG legs were threaded through the hole in LGM and cemented in place with cyanoacrylate glue.  For additional strength, one modeler CYA’d a 1/64 plywood plate on top of the wire set into LGM, while the other used a simple Tyvek patch.  A vertical gusset at the back of LGM to rib W2 was also installed to add strength.   The wing upper surface was covered after the LG leg wires were installed.    

Closing Build Update #3

Ok, lets close this third M.18 build update.  We’ve got several Miles M.18 models coming into the final assembly stage.  In the next update we’ll show the assembled models, discuss some specifics such as weights, flying surface setup, and prop/rubber combinations.   One of our modelers has even fitted skis. 

Until then, download the pattern sheet below, post any questions or comments and most of all keep those balsa chips flying!

 

Download:

24in Miles M.18 FULL SIZE PATTERNS

Build Update #2 – 24in Miles M.18

Wing construction, Fuselage construction Part 2 and the first Trial Assembly

 


 

Wing layout with pre-shaped Trailing Edges

 

Wing pre-assembly – Ribs and Trailing Edge
Fuselage side construction techniques
M.18 cockpit sheeting: template, mold, install
Fuselage and nose detail
M.18 trial assembly – looking good!
Completed M.18 wing with dihedral added to outer panels

Another two weeks have passed (4 weeks total) and the builders are making good progress.  All three are experienced modelers and are making minor modifications from the plan as they proceed.  Such is the attraction of scratch building – the builder has the freedom to inject their own preferences into the build.

Wing Construction

For “plank” wings like the M.18’s, our West Coast modeler likes to make a plywood template to cut identical ribs.  He then glues those blanks together with a glue stick, sanding the resulting block of ribs to make them all identical.  Then he cuts the spar notches and bird’s mouth for the Leading Edge with a blade or file. Soaking the block in rubbing alcohol dissolves the glue stick, and once the alcohol dries off, a stack of perfectly identical ribs is the result.  The slight taper of the Miles wing does require altering the ribs slightly for the outboard panels, but this is easily done keying off the main spar notches to keep everything true. 

Fuselage Construction – Part 2

Our West Coast modeler took a slightly different path in constructing the fuselage box.    He built the fuselage sides directly atop each other, at the same time, with no saran wrap in between. He’s careful with glue (CyA) and slides a single edge razor between the constructed sides to separate them.  He also used small dryer sheet pieces to reinforce the wing saddle joints and installed 1/64 plywood rear motor peg doublers.

Cockpit & Nose area

Ah, this is a tricky part – and one where builders take different approaches.  The M.18 plan shows full sheeting in the cockpit area from the top longeron up.  One modeler used a creative technique to mold, cut and fit this sheeting using a vellum template.  Another used a similar light paper template technique, but sheeted only from the lowest stringer up.  Interestingly, both modelers chose to install the M.18 cowl side panels not shown on the plan.   One modeled this using sheet balsa while another used a vellum panel approach.  Both techniques look great at this point.

Closing Build Update #2

Ok, we’re going to close this second M.18 build update here.  These modelers are already progressing into the tissue covering and final assembly stages so it won’t be too long before the next update.  Stay tuned!

Until then, keep those balsa chips flying!   Don’t forget to post your constructive comments or questions (none are too basic).

 

 

Build Update #1 – 24in Miles M.18

3 modelers are building the 24in wingspan Miles M.18 free flight rubber scale model.  Join in on the build and/or share positive thoughts via the Comment Forum.

 


Stripping 1/16 sq sticks from sheet balsa. Note “tiled”stab plan print
Tail construction underway. Cling wrap used to prevent frame sticking to plan.
2nd fuselage side constructed atop the first side. Cling wrap is folded over and same pin holes are used.
Fuselage box constructed upside down on top view plan. Magnets hold and align top longerons to metal building board.
Another approach is to use Machinist Blocks and weights to hold down and align the box as crosspieces are installed.
Completed M.18 fuselage box lifted from the building board. Nose former 1 has been installed.
Stay tuned for more in Miles M.18 Build Update #2!
24in Miles M.18 under construction. Get plan here

It’s been two weeks since we announced this online build and we’ve got 3 folks building the 24in wingspan Miles M.18 Mk2 free flight rubber scale model.  Two modelers are on the East Coast and one in the Pacific Northwest.  All have completed the tail framework, one has constructed the wing and two have made solid progress on fuselage construction.  We’ll share some to-date pics along with some of the techniques employed so far.

Initial Laydown

Two builders “tiled” the PDF plan and printed the appropriate sections on their home printer and dove right into the build.  One got the PDF file printed at Arch D size at the local print shop and cut the plan into sections for the build.

Wing

While one modeler has constructed the wing, we’re going to hold off on coverage there until the next update when all builders should be well into that phase.  Let’s move on to discuss M.18 fuselage construction, where two builders have been progressing more or less in lockstep.  It’s interesting to see their similar, but slightly different approaches.

Fuselage Build

Both builders constructed the fuselage side frames first in the conventional manner over the plan side view.  One builder constructed the second fuse side over the first which is a technique to help ensure the second side frame is a duplicate of the first fuselage side frame.  This helps achieve a straight and square fuselage box later.  With this technique, the plastic cling wrap that the first fuse side is built on is folded over that constructed first frame to prevent the second frame built ontop from cementing to the first one underneath.

Building a square balsa stick box is a challenging task and here’s where it’s interesting to compare the approach the builders took.  Both builders built the M.18 fuselage box upside down with the straight upper longeron held flat to the building board.  Both modelers used tools to hold the side frames to the board and keep them square while cementing the fuselage crosspieces in place.  While not specified on the plan, both modelers built the fuselage box with 1/16 sq balsa crosspieces installed along the top longeron.  These crosspieces will be cut away for rubber motor clearance after fuselage formers, stringers and cockpit decking have been added. One builder used pins to hold the fuselage side frames to a conventional balsa building board, while the other used strong magnets to hold his side frames firmly to a flat metal desktop “building board”.  Both used 90deg square blocks to check and maintain alignment as crosspieces were added top and bottom at the side frame upright positions to construct a square fuselage box.  One used magnetic squares. while the other used heavy machinists blocks (see My Favorite Tools #2 video).  Both modelers drew in the top and bottom longerons at the nose using Former 1 to provide rigidity and lock the box together at the nose.  Former 1 was the first fuselage former to be installed after the fuselage box – with all crosspieces installed – was lifted from the building board.

Closing Build Update #1

This is a good place to close this first M.18 build update.  The tail has been constructed and two modelers have the fuselage box completed and are adding formers, stringers and cockpit decking (more on that in Update #2).  One modeler has the wing constructed and is moving into the fuselage build.  More on the wing build will be provided in the next M.18 build update so stay tuned.

Until then, keep those balsa chips flying!   Don’t forget to post your constructive comments or questions (none are too basic).

Additional info:

My Favorite Tools #2 – Machinists Blocks ; youtube