Simon Chaddock
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Everything posted by Simon Chaddock
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Yes you must keep the engine in its rev range so that limits what you can do with the prop. You can go slightly bigger with a finer pitch but too fine and the thrust will fall off badly in flight. The answer of course to a scale diameter prop and pitch is to gear the motor down - just like all the big piston engines did. It needs a bit of good engineering to do well but it looks fantastic.
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Carburettor icing does indeed occur in the UK , see the number of air accident reports attributed to it on the AIB monthly reports! It occurs when both the humidity and air temperature reach a critical level, actually not that uncommon in the UK, but not neccessarily at or below freezing. The Met reports for aircraft always include warnings if icing conditions are likely. To maintain maximum engine performance light aircraft only use "carb" heat when required (or when the pilot remembers!). Icing occurs when the pressure/ velocity of the air changes thus wings can ice up as well. The problem is that if icing does occur it will just go on building up unless you can change the airflow or weather conditions - not that easy when in flight. I remember that in 1952 the prototype Bristol Britannia crashed just after take off due to icing in the inlet ducts of all 4 Proteus turboprop engines! Model engine carb icing is certainly possible but it does require a specific set of weather conditions so a repeated engine fault on different days or even between morning to afternoon is much, much more likely to be something else!
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DH-02 Drone information
Simon Chaddock replied to Torben Kristiansen's topic in All Things Model Flying
There was a nice article in the RAF Flying Review magazine (1960?) called "Dial S for Spin" describing how a DH Queen Bee drone defied the full might of the Royal Navy's anti-aircraft fire on a pre war exercise. After several passes over the ships a senior officer saved the day by instructing the pilot to "dial S for spin". The resulting crash into the sea was duly recorded by the newsreel as a triumph for the senior service! -
The original Fiesler Storch had FIXED slats all along the wing leading edge. This did limit the top speed (only 106kts on 240hp!) so retractable slats were prototyped but never not adopted. With drooping ailerons, vast flaps and a high energy u/c the Storch was probably the most advanced STOL light aircraft of its time. The radial engine version was built in France after the war.
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Hi You should not need a particularly strong sevo for wing warping if you have built a true scale wing. The Eindecker (like most aircraft of that era) used a very thin section that relied entirely on the wire bracing for strength and rigidity, so if you move the bracing wires appropriately and the wing warps! Compared to ailerons the deflection required is small, just a few degrees at the tip. This limited movement and the thin wing section means that the covering material should not wrinkle but remember you are moving the whole wing in the airflow so if there is any play in the system and you end up with serious and destructive wing flutter!
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The early Heyfords were fitted with 2 blade props but all marks were later refitted with 4 blade ones which better absorbed the power of the Kestrel engine. So you could correctly have either but NOT 3 blades! Better watch out for the very high thrust line on take off. Simon
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In search of the correct battery for my petrol ignition
Simon Chaddock replied to Clive Moore's topic in Scale Matters
Hi Chris Marshall is correct. It is ALL to do with the ability of the battery to supply a high pulse current, which is in direct relation to the cells internal resistance rather than their absolute capacity. NiCd are better in this respect than NiMH or Lipo. For a high pulse current the bigger the cell the better. Of course Lead/Acid cells (an even lower internal resistance) are better still! Just a point but small petrol power tools use no batteries on their ignition circuit, why don't model flyers? -
Hi Early rotory engines were relatively large in diameter so quite a bit of the prop was always blanketed, but as these engine rotated relatively slowly for their power they turned a huge diameter prop. In any case as about 90% of the thrust comes from the outer third of the blade the loss of thrust is not great, however the bluff shape of the engine does add considerable airframe drag so top speed was limited. On the Bristol they hoped the big spinner would improve things abit. The best answer to the issue of a scale spinner is of course - use a scale diam prop! Remember that if you have the engine torque to turn it, apply the power gently at slow air speed. True scale tends to have scale flying characterisitics! Simon
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Hi Here are some pictures my Triplane - basking in the sun! There are a few warps beginning to set in, but it is 39 years old! The wings have been recoverd once. The undercarriage elastic cotton "bungees" have to be replaced every couple of years! The Oberursel, cowling (spun 0.1mm aluminium), balsa prop (stained), washer & retaining clip. There a is gear inside the hollow engine crankcase which engages the motor pinion. At full power there is nearly 2 ounces of thrust which as it only weighs 2 1/2, gives it quite spritely performance. The slot car motor mounted on sheet acetate bearers with the bell crank fixed on top. The front bearer is removable with two 10BA screws to allow motor removal. Note the scale fuselage structure painted grey to simulate steel tubing. Simon
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Hi Yes it is spectacular what can be done with micro radio gear and modern batteries but it still requires quite a big hall. There are also some truly amazing videos on You Tube of indoor flying - hovering on the prop and then calmly catching the model - saves landing! I did fly a peanut RTP. It only needed 4 foot lines! I will add a picture to my album. Simon
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Hi I have now added some pictures of the triplane (and some others) in the gallery!
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Hi I am a new member but an old flyer. Along time ago I started experimenting with electric RTP. The object was to fly a small model in the available space, i.e. my bedroom, and that meant 4 ft lines with a 15" span model. To cut a long story short I did eventually achieve it - just - and that was in the early 1960s. Improved "scalextic" type motors gave more power and reliability and with a geared propeller allowed me to indulge my passion for building lightweight models. In the course of my experiments I discovered the advantages of CONTROL LINE RTP - the motor needs two wires so why not use them! The centre pylon is a bit more complicated but with throttle AND elevator very delicate models can be flown safely. So what was going to me give substantial wing area within a compact overall airframe - the Fokker Triplane. Now a scalextric motor weighs about 1 ounce so my task was to build a scale airframe (16" span) for about the same. I just failed, the final model weighs 2 1/4 ounces but that did include working 'bungee' suspension, a spun aluminium cowl and a scale Oberursel rotary that goes round with the prop! Now that is real scale. It also flies well and it did, at the 1969 Model Engineering Exhibition and many, many times since. Just to complete the picture I still have it 39 years later! A rather specialised form of aeromodelling but at least I can fly in my own house come rain or shine! Simon
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