Piers Bowlan

I bought a set of foam wings for a CB so I too would be interested to hear why your C of G has turned out too far aft before I start on building my fuz. Will a larger LiPo not move it sufficiently forward?

The MP Jet .040 PB Classic diesel is considered a good alternative to the Mills .75cc I believe. In fact I bought one of these at a show some years ago for a Tomboy but never got around to building one! There is one for sale here. However, I agree with Phil, if I was building one today it would be electric.

Great project Simon, following with interest. A pity the XF-5U became bogged down with engineering problems with no less than six gearboxes plus the two huge P & W radial engines buried within the wing. The decision to make the huge propellers have cyclic control like a helicopter added considerably to the delays. Might have made a great close air support aircraft on the basis of it’s projected wide speed range and performance. However, it lacked the simplicity and low wing loading of the V173, which flew so well. Lindbergh was enthusiastic about the V173 despite suffering an engine failure and having to land on a beach!

Amazing that an engine so small can make so much noise -and be loads of fun. Some people are like that! 🤩

Peter is spot on with his ‘rule of thumb’. As for some airliners having as much as 110 degrees flap deflection, this seems unlikely although I am always happy to be proved wrong. 😑 The B744 had flap 25 or 30 landing flap positions on the flap quadrant selector although the third segment of it’s triple slotted TE flaps appeared to have a far greater deflection when deployed. All I can say is they worked very well! How much landing flap an aircraft has available depends on what the designers are trying to achieve. Large deflections facilitate a steeper approach and therefore terrain clearance. Also they will usually improve the pilot’s view over the nose of the aircraft (think Spitfire) or if trying to land a jet on a carrier deck (😬). Shorter, slower landings on a limited or contaminated runway are other benefits but not really relevant to our models. However large flap deflections introduce complicated structures with a weight penalty. They also reduce lateral stability and while enabling slower flight, increase the tendency to ‘tip stall’ near the point of stall. Not good if near the ground 😱.

The main point I would add is that not all brown paper was born equal, use good quality paper that has a grain. Some is made from recycled paper and tends to fall apart when wet, especially if you try and stretch it. Also, personally I dilute the PVA aboutt 20% or when it has the consistency of single cream but it depend on the PVA. Economy PVA is very thin (rubbish) and I wouldn’t use it on anything let alone dilute it! I give the brown paper treatment to reinforced polystyrene (EPS) wings. I wet th brown paper under the tap then apply glue with a brush on a pasting table. If there is an air bubble I push it to the edge with a sponge. I ensure the edges of the paper is stuck down which sometimes might require a little more glue. Ensure both sides are covered before placing in the airing cupboard to dry overnight. I apply another coat of PVA to seal it. which gives a very good surface to take paint when dry.

I emailed Manny Williamson last week regarding this point and Ron is correct. ‘The flight line will be supervised so models below 7.5kg can be flown without an ‘A’ cert.’ It follows that above 7.5kg you do. I will try and get along to the event but it is quite a hike from Dorset.

If the objective is to make the approach and landing into a small field easier then personally I would do as Martin suggested earlier, reflex both the ailerons upwards for landing. You could use a three position flap switch on your Tx if it has the mixing feature. The T 31M has very large ailerons and I think this would be highly effective for killing lift and steepening the approach. I have used this to good effect on my gliders in the past. PatMc’s suggestion is also a good one, I must try it sometime. Spoilers might give you scale fidelity but are a lot of work/complication when with just a bit of transmitter programming you can achieve much the same flying characteristics. Just my 2p worth!

Balsa is a very satisfying and versatile material to work with as we all know so well, pity it has become so pricy. I have fairly recently rediscovered the joys of hot wire cutting EPP foam sheet. With a little carbon strip (or balsa or ply) reinforcement and covered with brown paper/PVA, it is very light, torsionally stiff and surprisingly tough. Best of all it is very cheap too! You can quickly knock out several models from one sheet of 2.4x1.2m foam for under £20 from B & Q. It doesn’t require too much effort to make up a cutting bow and source a suitable power supply from eBay.

I had a catapult launched EE Lightening that flew great and was just as dangerous! Until that is, it disappeared into the soft sand on the beach I was flying from, never to be seen again. 😢 They don’t make fun toys like that anymore, wonder why?!! 🤣

Airliners like commercial shipping (and fishing boats) don’t pay UK VAT on their fuel. It’s a global market so if they did there wouldn’t be any UK airlines, or jobs. If you think the fuel should be taxed globally, tell that to ICAO. However, ‘holidaymakers that fly half way round the world for a week in the sun’ are taxed here in the UK. Air Passenger Duty raked in £4500 billion to the UK treasury last year. If air travel is to be greener then airlines need to buy more efficient aircraft, geared turbofans as one example, which is an expensive long term commitment. More taxes is just a disincentive to do that and won’t make the world a greener place. Finally, making comparisons with your diesel car is a bit fatuous for obvious reasons.

Reading the Outerzone reviews it looks like it will be an excellent model. Good luck with the build Nigel. 👍

I’ll try and make the weekend but not ‘Seven days’ (Craig David).

Why don’t you pop them an email Stuart, telling them to send you the correct sized plan and a couple of the missing formers while they are at it? They will probably be pleased to hear from you as no doubt all the kits in the recent product run are like it. I don’t believe they did it on purpose and it won’t do their reputation any good.

You showed us the air scoop you fitted Bonzo but where is the exit for the cooling air? The opening for the exit should be larger than the intake to ensure a cooling flow of air to the ESC and battery. I think most modellers use an ESC rated at least 25% more than the measured current draw (by a watt meter). I guess it doesn’t matter too much with a light-weight cheap foamy.

Miss Lizzy at 51in span is a good size, me thinks. It has been on my build list for an electric conversion since Sep 2005 when the plan came out! A glaring omission by Sarik not to offer a parts set. Still, no biggy cutting out a set of parts oneself. Perhaps RCM&E should republish the plan in a future issue with a leccy conversion? Get well soon Peter, the modelling world is waiting for your next design. 😊

Why did you put your plug in the oven? I heated my plastic sheet held in its frame in the oven until it sagged (wife was out!) I switched on the vacuum cleaner and smartly pulled the frame holding the plastic over the plug. The plastic cooled very quickly once formed on the cold plug, so didn’t have time to damage the dope finish.

I made a plug for my Blackburn Firebrand out of balsa laminations as it is quick and easy to shape but not cheap 😢. I gave it several coats of dope which gave a good smooth finish after sanding. I mounted it on a balsa spacer for the vac- forming.

The wooden block is end-grain which doesn’t glue particularly well. The front screw is countersunk, so more likely to pull through liteply. Also, a bigger doubler that extends to the top will help those who havn’t started yet. I will try a roundhead screw and large washer as well. I appreciate the rear screw needs to be countersunk because of the hatch. This non-issue doesn’t seem unresolvable, it’s just engineering.🤔

Hi Mike, I expect you have checked already but as these engines seem to like plenty of oil (22%) - particularly castor, is the crankcase vent clear of fuel gunk. Also checking the pressure line from the muffler is clear, could be worthwhile. Hope you get it sorted 👍

I agree PatMc, I got that wrong way round. Doh!

Fair enough 🙂

Published thrust values for motors are usually just a guide to what the maximum thrust might be. The number of cells used (voltage) and the load (Amps) prop size (diameter and pitch) will both massively affect the power of the motor (Watts). The prop efficiency will be a factor too, which brand of prop- Master Airscrew or APC for instance. Then, what thrust are you talking about as static thrust will tend to be less than dynamic thrust, when the motor unwinds in the air, as it won’t be partially stalled as it is on the ground. The limiting factor for a motor is at what point does it become inefficient and start turning more power into heat which ultimately will end up burning out the windings? In short, the right motor choice for a model is not always clear cut!

‘Vertical flight with an airspeed above stall is still low alpha, or pre stall.’ If an aircraft is in vertical flight it may have zero alpha (no angle of attack) as the wing won’t be producing lift it won’t be stalled, the aircraft hanging on the prop (vectored thrust). So not too sure what you are driving at here or what you are trying to achieve? Why the interest in a model’s stalling speed and its relevance to power requirement? As I understand it, you want to know what the minimum power requirement is for your trainer?