Wednesday, 6 November 2019

F3-RES Rules - UK Translation

Here are the UK Rules for F3-RES. These are the best translation we can make of the German F3-RES rules that are used across Europe.  Hope they make sense..

English Translation/Interpretation for Class F3-RES thermal-gliders (Rudder, Elevator, spoilers)

1. General Provisions

a) “F3-RES” is a competitive class for radio-controlled gliders with a maximum of two (2) meter wingspan constructed predominantly of wood. Control is via elevator, rudder and spoiler. If used, spoiler(s) must be on the wing upper surface at least 5 cm ahead of the trailing edge. The spoiler(s) can be controlled with either one or two servos. Launches are to be done with a hi-start (see Section 6).

b) Definition of a remote-controlled glider: A model aircraft which is not provided with a drive device and whose sustained flight depends entirely on aerodynamic forces acting on its immovable surfaces. Models must be remotely controlled by the competitor on the ground.

c) In competition at least four (4) qualifying rounds shall be flown. For each qualifying round, participants shall be divided into flight groups. The results of each flight group shall be normalised to arrive at comparable scores between the flight groups. The highest score within each flight group will be assigned 1000 points and the remaining scores within that group shall be proportional to each participant’s raw flight score relative to the best raw flight score within that group. The group size in the “Fly-Off” shall be the same as the group size in the preliminary rounds. Participants flying with the highest total normalised scores from the Preliminary Round will compete in a “fly-off” (minimum 2 rounds) to determine the final classification.

d) The competitor may use a maximum of two competing models. A model may be replaced within a round only when the competitor’s prior launched model is returned to a point within a radius of 15 meters of the assigned Landing Point.

e) The participant may use up to three (3) assistants. These are to assist him in launching and retrieving the model, informing him of weather conditions and flight time and to manage the hi-start. At least one helper shall constantly ensure that the pilot’s assigned hi-start does not interfere with anyone else’s assigned hi-start. This requires that his pilot’s hi-start be immediately returned to its assigned position. In crosswind conditions the Contest Director may determine that the contestant who is farthest downwind begin with the start so that hi-starts do not interfere with each other during launching.

f) The organiser should have official scorekeeper / timekeeper available. If this is not the case, the pilot’s helper will keep time, and the organiser will regularly sample the flight times. Deviations of more than three (3) Seconds in favour of the participant shall lead to a zero score flight.

g) The landing points shall always taken by an official scorekeeper.

2. Model

2.1. A model normally consists of wings, fuselage and tail. Flying wing models that do not have a fuselage and rudder or vertical stabiliser, or none of these components are also allowed if they have a total of only two (2) control surfaces. Each of these control surfaces must be actuated by only one servo. Otherwise, the building codes for a conventional model described herein apply. The model shall be fabricated primarily from wood. This means:
  1. For the wings, GRP/CFRP/Kevlar tubes or shapes may only be used for spars, wing leading edge and joiners.
  2. The tail boom for the tail unit may consist of a GRP/CFRP/Kevlar tube or shapes. The composite tube or shape may not extend forward of the middle of the root chord of the wing.
  3. The wood parts of the fuselage may be reinforced on their surface with GRP/CFRP/Kevlar.
  4. Control rods are exempted from the CFK/GFK constraint.
2.2. The following Are Not allowed:
  1. An all-GRP/CFRP/Kevlar or other plastic fuselage or fuselage pod
  2. GRP/CRP/Kevlar monocoque construction wing or tail leading edge, also no GRP/CRP/Kevlar DBox
  3. A stabiliser or wing made of GRP/CFRP/Kevlar foam planked or other plastic construction.
  4. Fixed and retractable devices for braking the model on Landing on the ground (e.g. bolts, serrated protruding devices, etc.). Nothing may protrude from the bottom of the fuselage other than up to two Towhooks (each a maximum of 5 mm wide x 15 mm high, seen from the front). The Towhook may be adjustable, but not by remote control.
  5. External ballast.
  6. Any telemetry with the exception of radio signal strength, receiver temperature and battery voltage.
  7. Use of telecommunication systems on the airfield by competitor and their helpers (radios and phones included).
3. Contest Field Layout
  1. The competition must take place on a terrain that is flat that provides the smallest possible chance slope or wave soaring.
  2. The flying site should have a designated Starting Line. The Starting Line is perpendicular to Wind direction and has marked Starting Spots for each competitor that are at least eight (8) meters apart. The “Starting Line” and stakes fastening the hi-starts to the ground of shall be parallel lines approximately 145 meters apart (possible Exception see item 6). The attachment points for hi-starts have the same spacing as the Starting Spots.
  3. Landing Spots should be at least eight meters apart and should be at least 10 meters downwind from the Starting Spots.
  4. The Landing Spots and the Starting Spots shall always be clearly marked. The distance from the fuselage nose to the Landing Spot shall be used to determine the landing score.
  5. The Contest Director shall determine the landing boundaries. Landing outside the boundary shall result in a zero score for that flight.
4. Competition Flights
  1. The competitor is entitled to at least four (4) official flights.
  2. The competitor is entitled to an unlimited number of attempts during a Flight Window.
  3. An official attempt begins when the model leaves the hand of the competitor or his helper under the tension of the hi-start.
  4. The Flight Window is nine (9) minutes long.
  5. A normal Flight Task is six (6) minutes long unless modified in accordance with 6(d).
  6. Timing for any Flight Task begins when the model separates from the Hi-start. It ends at the EARLIER of the time the model comes to rest for its last launch during any particular Flight Window OR at the end of the Flight Window. No time shall be measured AFTER the end of the Flight Window.
  7. In the case of several attempts, the result of the last flight is the official result.
  8. The Contest Director has the right to interrupt the competition and reset the Launch Line when the wind direction deviates.. He can cancel or suspend the competition if wind of more than six (6) meters / second (13.4 mph) measured two (2) meters above the ground at the Launch Line and prevailing for a period of at least one (1) minute.
5. Re-flights

The competitor is entitled to a re-flight when:
  1. His model collides with another flying or launching model.
  2. He is prevented from launching or relaunching as a result of his hi-start being fouled by another hi-start.
  3. When his flight is hindered or aborted by an event beyond his control.
  4. To claim a re-flight in accordance with the reasons set out above the competitor must land as soon as possible. If the competitor continues to fly it is assumed that he waived his right to a re-flight.
6. Launching
  1. Identical Hi-starts shall be furnished and set up by the organiser.
  2. Hi-starts shall consist of a 15 ± 0.5 meter rubber tubing and 100 meters nylon line with a minimum diameter of 0.7 mm with a flag attached.
  3. When extended to a length of 45 meters, the rubber tube shall not exceed a pull of 4 kilograms. The deviation between the rubber tubes shall not exceed 0.4 kilograms.
  4. At airfields that will not accommodate a total hi-start space of 145 meters, the Contest Director may shorten the nylon line and shorten the corresponding flight time. Such changes should be included in the Competition Notice.
  5. Competitors may not extend their respective Hi-starts past their assigned Starting Spots.
7. Landing
  1. Before each flight each competitor will be assigned a Landing Spot that corresponds to his assigned Starting Spot. It shall be the responsibility of the competitor to use the correct assigned Landing Spot.
  2. During the landing process only the pilot and his assistant are allowed in within 10 meters of the Landing Spot. Any other helpers and timekeepers shall remain at their assigned Starting Spot.
  3. After any landing, the pilot or helper may retrieve his models during the task Time Window if this retrieval does not interfere with other planes and pilots flying in the group. A model thus retrieved may be relaunched during the Task Window. No landing score may be recorded for a model that has been touched before scoring the landing.
  4. No landing score will be allowed for a model whose tail does not come to a rest on the ground.
8. Scoring Flight Performance and Landings

8.1 Scoring of flight performance:
  1. A nine (9) minute Task Window starts with a sound signal by the Contest Director. 
  2. The flight time starts when the model disconnects from the Hi-start.
  3. In the event of subsequent launches during a Task Window the Flight Time will start when the model disconnects from the Hi-start for its last launch during the Task Window.
  4. The Flight Task Time is six (6) minutes to be completed entirely within the nine (9) minute Task Window. The flight time is recorded in seconds without rounding. Two (2) points will be awarded every second flight time.
  5. The Flight Time ends at the earlier of:
    1. When the model stops moving after its final launch during the Task Window or:
    2. At the end of the Task Window (Nine (9) minutes after the start of the Task Window. The Contest Director will make a sound signal designating the end of the Task Window.
8.2 Scoring of the landing:

a) The landing score will be determined by the distance between the nosecone of the plane (Or the most forward point on the centre line of the plane) and the designated Landing Spot with the plane at its final resting spot. Depending on the distance the following points are awarded:

in m
Points Distance 
in m
Points Distance 
in m
0.20 100 1.80 92 9.00 60
0.40 99 2.00 91 10,00 55
0.60 98 3.00 90 11,00 50
0.80 97 4.00 85 12,00 45
1.00 96 5.00 80 13,00 40
1.20 95 6:00 75 14,00 35
1.40 94 7:00 70 15,00 30
1.60 93 8.00  65 > 15.00    0

b) Zero points for landing the participant if:
  1. The plane’s tail does not come to a rest on the ground.
  2. The model sheds any parts.
  3. The model is not airworthy after the landing.
  4. The model is still flying after the end of the Task Window.
  5. The pilot or his helper model the touches,
  6. The model is moved by the pilot or helper before a landing measurement is made.
c) Zero points for the entire task (flight and landing) are awarded if:
  1. The model comes to rest outside a Landing Boundary specified by the Contest Director.
  2. The model has not landed within 30 seconds of the end of the Task Window.
8.3 Scoring the round
  1. Each competitor’s Raw Score in a round will be the sum of the Flight plus the appropriate Landing Points.
  2. Within each Flight Group, each competitor’s Raw Score will be normalised by multiplying the proportion of his score for that round to the highest Raw Score within his group in that round multiplied by 1000.
8.4 Scoring the Qualifying Rounds
  1. Each competitor’s Raw Qualifying Score will be the sum of his Normalised Total Scores for each of the Qualifying Rounds. Each competitor’s Normalised Total score in the Qualifying Round will be restated as a percentage of the best Normalise score for the Qualifying Round. For example, if the best Normalised Total Score for the Qualifying Round is 3995 points and another competitor has a score of 3500 points, the other competitor’s score for the Qualifying Round would be: 3500/3995x100 = 87.6. Other Qualifying Round Scores will be computed the same way.
  2. The highest scoring competitors in the Qualifying Round equal to number of competitors the largest group flown will advance to the Flyoffs.
  3. The Flyoffs will consist of at least 2 Rounds flown the same way as the Qualifying Rounds, but only by the pilots determined in 8.4.b above.
9.0 Scoring the Flyoff

The winner of the flyoff will receive 3 bonus percentage points in addition to his score for the Qualifying Round. Second place in the flyoff will receive 2 bonus percentage points, third place, 1.5 bonus percentage points, fourth place, 1 bonus percentage point and fifth place, 0.5 bonus percentage points. All other competitors will receive the percentage points earned in the Qualifying Round.

10.0 Advice for Contest Notice 

Each participant is flying at your own risk and liability, has a valid insurance coverage and/or BMFA or equivalent membership. Participants agree to make no claims against the organiser.

The Contest Notice will state any expected modifications in the total length of the hi-start and/or Task Time because of space limitations.

Tuesday, 8 August 2017

FOKA 4 1/4 Scale Glider

Something different for a change.

I have always fancied a scale glider. Not necessarily a hanger queen with rivets that I need to count, but something that looks the part and can be flown without too much worry that something may fall off on landing. i.e. a decent stand off scale model.

No plans for this model are available, so working from a 3 view downloaded off the internet, I started work on the plan.

Its a case of design it then add constructional information and changes to the design as I progress, adding detail in case someone else wants to build one. However, due to some CAD issues (not my error), its unlikely that I will release this plan.

Quite a lot of work getting this far and it also helps add some motivation to get it finished

The easy bits were the fin and tailplane and these were built first while the laser cut parts were finalised before being sent to Belair for cutting.

Construction of te fin and tailplane is very traditional balsa and spruce with the balsa sheeted areas covered in light glass cloth but Eze-Kote used instead of epoxy. The elevator and rudder are covered in Solartex.

Fuselage construction is basically 4 of 6mm square spruce longerons and a mix of birch and lite ply formers. The majority of the loads are carried on the former that supports the LE and the main former that supports the wing. Where there are transitions in the longerons, the load is pass to an adjacent part of the structure so - hopefully - there are no sudden discontinuities

An almost full length deck is used to add stiffness and also ensure that the fuselage remains exactly straight.

Construction was quite straightforward except that the CAD software had miscalculated the width of the deck (not allowed for the side longerons. This meant that these had to be laminated from 2 of 6x3mm with the deck sandwiched between. Not too onerous to correct.

The controls for the rudder and elevator are internal and cannot be accessed once the fuselage has been built so the next job is to fit the fin and tailplane:

A simple foam block jig holds the fuselage steady while incidence is measured. The tailplane will be placed at +1 deg and the wing at +2.5 deg. I use a smartphone clinometer app (bubble level) to ensure that the tailplane is set correctly. Triangulated using thread to the former behind the cockpit to make sure its not twisted.

The tailplane needed a small platform from hard balsa to seat the cambered section. This meant the tailplane was lifter about 5mm higher than the scale position.

When dry, the fin was glued into place. This needed a hole drilled in the top longeron (this has 6mm spruce doublers each side to make a wide enough platform for the tailplane and fin to sit on securely).

The fin also has a 6mm dowelling peg to give it a bit more stiffness.

While all this was going on, I started work on the wing. This wing will be in 3 pieces. It will have a composite carbon/spruce/balsa main spar with a spruce rear spar.

The root cross section looks like this:

The Carbon tube tapers from 10mm (0.5mm wall thickness) at the root to 7mm at the tip in equally spaced step (10 > 8 > 7). This is supported at the root area by a soft 12mm balsa 'web' (grain vertical) epoxied to the carbon then a 12x3mm spruce top and bottom cap. This will taper to 6x3 at about 80% wingspan. The Joiner is a 9mm carbon rod. Te rear spar is 6x3 which delimits the ailerons and the spoilers with additional support in the root. The main dihedral brace is 6mm marine ply which tapers slightly to fit with the sweep forward of the main spar.

The centre section is about 600mm wide, the outer panels one piece..

The wing mounting bolt sits in a full depth birch block recessed to take a M5 steel cap bolt

Just spotted that I have lost the rear spar at the root on this diagram

Assembly is simple but slow as all the balsa blocks have to be cut and filed to shape. Drilling causes the soft balsa wood to split.

The root rib as 12mm balsa with ply sides. The wing joining block just behind the main spar is beech and is recessed to carry a M5 steel bolt

The wing centre temporarily pegged into place whil the tailplane was aligned.

More to come

Wednesday, 5 April 2017

A simple way of Calculating a Tuned Pipe Length

I managed to acquire a brand new in box OS61VR.

There is very little information on this engine on the OS archive, in fact I cant find any reference to it. I have a choice of a number of tuned pipes I can use  - one came with it, but it looked rather small compared with the other 60 sized pipes I have so it may be the wrong pipe. The supplied header also appears to have been used as a hammer - it was very badly creased so I ordered a new one from Just Engines.

They also had no information on this engine.

It  has a large inlet and exhaust port. This suggests that the engine will be rather powerful and probably very thirsty as well.

Now, forgive me if I am teaching you to suck eggs here, but I need to set the pipe length and this can be calculated using the following formula.

Pipe length (in inches) = Exhaust Timing (in degrees) * 1650 / Desired RPM.

I am hoping to get 12000 rpm on a 12x8 prop (in the absence of any other information).

The exhaust timing is calculated by placing the engine at TDC, turn the crank (in the direction of rotation) and look for the piston crown just appearing through the exhaust port (at the top). Note the angle on the timing disc. Continue to rotate through BDC until the piston crown disappears again on the compression stroke - i.e. you have timed the exhaust open window.

I made up a simple timing disk and attached a pointer using a jubilee clip as shown.


Using this technique, I measured this engine to have an exhaust open timing of 145 degrees.

Substituting the numbers above,

Pipe length = 145 * 1650 /12000 = 19.9375". The pipe length is measured from the centre of the piston crown to the baffle in the pipe where the diverging and converging cones meet.

There becomes a point where the exhaust timing becomes too long for a tuned pipe to become effective. A longer exhaust open time will give the user an easier handling engine but the benefits of the tuned pipe diminish - reducing to zero when the timing increases towards about 175 degrees.

Monday, 3 April 2017


This is a short post  that links the downloads that I have made available.

Mystic 40

Mystic 40 plan and and cut parts layout

Kwik Fli 3 for a 40

Kwik Fli 3-40 plans and cut parts layout 

Kwik Fli 4 for a 40

Glass Slipper Slope Soarer

DH87B for Indoor Scale

I have been asked to take part in the indoor Scale Nationals at the end of March 2017. Probably being rather overambitious but I have taken up the challenge and will try and build a 1/14 scale DH 87B Hornet Moth.

G-AELO is the target aircraft that I am going to try and replicate,

(image Wikipedia)

I started work on the plans in 2015 - it was originally intended as a Free Flight Scale model at 1/12 scale (31" span) - something I may attempt to start and complete again in the future.

I have simply scaled down the original CAD drawing I produced and I am using this as the primary source for the airframe structural layout. As the CAD drawing is currently incomplete, it is likely that I will have to rework substantial parts of the model. Hopefully not too much rework though.

G-AELO is also one of the featured aircraft in the book "De Havilland Moths in Detail" by Stuart McKay.

This will simplify getting the supporting documentation needed for the competition. By the way, the book is an excellent read, a great deal of information provided in a manner that is very interesting with some superb photography to support the text.  Makes you feel part of the story. Highly recommended.

This is the plan that I am currently working to. It's traditional Stick and Tissue construction but with micro RC gear fitted. The Scale Maestro Danny Fenton is also giving me lots of guidance and for that I am exceedingly grateful.

The plan was tile printed from PDF and the A4 sheets taped up then trimmed. A very low cost way of producing a plan

There is not much actual build information on the plan, its really just a parts placement plan so ideas will be tried (and many rejected) as the model is being built. I'll also be trying out some new ideas as well

A couple of evenings in the shed and one side is almost completed. The cling film is to protect the airframe - not the plan.

The second side is built directly on top of this side (separated by cling film) and then joined together using cross members with measurements taken directly from the plan. That curved top elevation will be fun to achieve.

The fuselage sideas are jigged upright and then a few selected spacers added. The whole lot is then weighed down carefully and the glue allowed to dry thoroughly. The taper behind the wing is straight and very simple to achieve. The taper in front of the wing is curved and different top and bottom and far more challenging.

Very fragile in this state, I cant imagine how many spacers I have to secure. Glue is weight and is kept to a minimum, sometimes a little more is required.

The front fuselage spacers added and work started on the fin.

I used a laser dye transfer method. I am trying to get the appearance of a scale structure. The method is quite simple, laser print the shape with ribs etc. Flip the print face down on the balsa with the grain running in the correct direction and then rub a little cellulose thinners through and the image is magically transferred onto the wood.

This has a 1/32 balsa core hollowed out around the 1/32 doublers in the fin area then a significant amount of wood is removed from the rudder, leaving mainly an outline and the 1/32 square ribs. The whole lot is then sanded down to a streamline.

It sits in the top of the fuselage with the small tongue located in a slot in a 1/32 fill sheet. Weight of the fin and rudder is 1.44gms

The nose block was manufactured from 1/2" very light sheet balsa. A suitable sized washer - the same diameter as the spinner was tacked into place and gave me something to sand to.

Its not quite the correct shape yet, but its not a million miles out either

And this is what it looks like. The 3 curved upper front deck formers are slightly too high and need to be reduced by a couple of mm.

The cockpit was fabricated and installed before the fuselage could be covered.

I was really quite pleased with that console as a first attempt

Cant claim any credit for the pilot. He is actually slightly too small in scale and I did have to provide legs and paint him (now known as Cedric).

And installed..

Wing construction is fairly traditional for indoor models, comprising of wing ribs created by wrapping a preformed (sliced strip) for the top and bottom over internal spars. I a not entirely happy with this method of construction. While it is undoubtedly very light (the wing panels weighed 8 grams each), I found it rather too fragile for my ham fistedness.

Ailerons were built with the wing then separated when ready for covering then hinging

A sort of bare bones shot.

The flight radio gear was procured from Micron UK, comprising of a micro Rx and servos and a park-fly motor, gearbox and prop.

Carbon push-rods used for the aileron linkages out to traditional bell-cranks. Horns fabricated from 1/32 plywood.

I found covering very difficult. Any construction errors were magnified by the resulting creases and it took many attempts to get it to a state that I was half happy with.

 The model was covered in red and silver Esaki Jap tissue. The orange roof panels were from Orange cellophane from a brand of Jaffa Cakes.

Windows frames cut from a very thin baking tray and glazing from the base of a cake tray.

Tailplane and rudder

Interplane struts are located using a bent pin through a small loop in the correct place

Lettering and logos were produced in Photoshop then transferred back into CAD to make sure that the size was correct then printed onto transfer paper then finally sprayed with car lacquer to make them waterproof, before they ere placed in water to separate them from the backing

When finally finished, it looked like this

A very interesting project. I am not entirely happy with the wings as they have bowed slightly and may redo them but I think its not a bad representation of the original.