RottenRow

Perhaps something like this... https://www.hmgpaint.com/products/all-products/primer/26/cellulose-aps-primer Available in white (code APS2). Several sellers on ebay have it, around £27 delivered for a litre. Or try your local car paint supplier. Cellulose is still available for classic car restoration purposes, though not all suppliers have it. Brian.

Thanks for posting the pictures of the plan and instructions, they are always useful to have. Your model looks great with its new cowl. Brian.

Ha ha posted my reply at the same time as JD8. Brian.

As you mention not needing anything too fancy, and also the possibility that you will join a club, if there is one local to you perhaps it would be a good idea to make contact with that club and visit their flying site. There may well be someone there who is changing their radio system and will have one for sale. R/C equipment generally has a fairly poor resale value so you might pick up a good basic set for not much money. You'll also probably pick up some good advice. Brian.

Interesting, the box lid label states the model weight as 10 1/4 lbs (might be 10 1/2, it’s a bit unclear), and engine size .61, which was the maximum size allowed in scale competitions back when the model was designed. I think one would be doing very well to get one of these down to that weight. Brian.

Yes it’s a pity that Hangar One don’t have a UK agent, especially one that could cut the wood in the UK to reduce the transportation costs. They have some nice looking models available. Brian.

Mine has a lump of lead bolted onto the engine mount to get the C of G right, the tail is presumably built heavily. I am away at the moment so can't check where the C of G is but 100mm sounds about right. It does 'feel heavy' in the air, if that makes any sense. The elevator on mine is fine for flying but is sensitive for landings, it lands just like Roy's model. I do have some expo set up. I too would be interested to know your control throws please Martin. I never had the instructions or plan for my model so it was set up by trial and error. Brian.

Good to see the Magister in the air. Yours appears to fly a bit faster than my 120 powered one, which is about 1lb heavier than yours, probably more with fuel. I think the flexing of the u/c legs is inevitable, considering their design and construction. The only definite way to prevent it would be to fix the legs straight into the wing rather than by the torque rod arrangement as designed, but that would need a fair amount of wing surgery. On mine, I have shortened the length of the torque rod part of the u/c as much as is practical, which has helped to a degree. Larger gauge piano wire would help too. Very impressed with your scale details Roy. Brian.

Another possibility is the Chilli Wind. The plan is free to download from Outerzone. Originally it had veneered foam wings, which can be supplied by Bill Kits. There is another thread on this forum that includes a set of wing rib outlines should you prefer a built-up wing. There is also a smaller version, the Chilli Breeze, an electric version of which will be a free plan in a forthcoming RCM&E. Brian.

I’m sorry Pat but your test results prove nothing of the kind, other than that the wattmeter measures the battery voltage, which I already agreed with, and that there is some sag in the battery voltage as the current it is supplying is increasing (to be expected). I have never stated that the wattmeter reads the rms voltage being fed to the motor. What I did state, and stand firmly by, is that the power drawn from the battery, that is the reading given by the wattmeter, at any motor speed setting, equals the power supplied to the motor (plus a small amount for losses in the ESC). Luckily, as the majority of users of wattmeters will be taking their readings at full ‘throttle’ anyway the subject is somewhat academic. As this discussion is going around in circles, and I really don’t like disagreeing with people on the forum, I will bow out at this point. I concede to your better knowledge with respect to the winding arrangements (star or delta) within the small brushless motors that we use in our models, as I haven’t taken one apart for a while. Brian.

Also the tranny is probably used for more than one model, so has the capability to cause multiple carnage… Brian.

Ha ha I was just going to write exactly the same comment, almost word for word! Lovely model Roy and great to see an old model given a new lease of life. Brian.

I agree that the Maxon controllers have many more features and operate with much more precision (they are sensored for a start) than our model ESCs but I used their example as I couldn’t find one specifically for model ESCs. However they do operate on the same principle and they do not have a separate DC:DC converter, it is all done in the output MOSFETs and motor windings. The diagram you have reproduced above is an equivalent circuit and isn’t supposed to represent what is in the controller component for component. The switching sequence of the MOSFETs in a brushless motor controller is such that the applied voltage across any individual winding gets reversed during motor rotation. This, along with the voltage induced into the winding as it passes the magnets, means that the motor voltage and current waveforms are not simple or constant. This is complicated even further by the fact, as the motor windings are (usually) star connected, two windings are being powered simultaneously (in series) by the controller but a fraction of a second later one of those two is replaced by the third winding as a different MOSFET switches on. It is this that creates the rotating magnetic field that the rotor then follows. My main reason for raising this in the first place was to doubt the comments about the use of a wattmeter in the battery leads being accurate at anything other than full throttle. I still believe this statement to be untrue. DC (battery) power in must equal motor power out plus losses. Brian.

I’m sorry but I’m not wrong. I do know all about the current and voltage levels in a series circuit… Kirchoff’s laws… but a brushless motor / ESC / battery isn’t a series circuit. Certainly not a simple DC circuit to which your ‘rule’ applies. Neither am I wrong about the correctness of the readings given by a wattmeter connected in the DC side of the circuit. I’m not going to argue the point but perhaps you would like to look it up on the internet or in a reference book. Here is a good starting point… https://support.maxongroup.com/hc/en-us/articles/360016161594-Motor-controllers-Input-current-versus-Motor-current-Power-Conversion Brian.

In other words... don't reduce your full throttle end point to (say) 75% in an attempt to reduce the current, but fit a smaller prop. (smaller diameter, pitch, or both) to actually reduce the current. Brian.

This isn't correct I'm afraid. The wattmeter, connected in the battery to ESC leads, actually measures the motor power (watts) plus the power losses in the ESC (that cause it to heat up). This is true at any throttle setting. As the losses in the ESC are comparatively small, this means that the wattmeter will indicate close to the motor power or wattage. (In practice there will also be a small amount of power being fed by the ESC BEC to the receiver and servos, which the wattmeter will also include in its reading). Whilst it is true that the wattmeter is measuring the 'ingoing' battery voltage, it is also measuring the 'ingoing' current to the ESC. This means the wattmeter will read correctly. The actual current in the motor windings will be greater than the DC current flowing from the battery, especially at part throttle settings. As we can't measure the actual motor voltage or current (it's three phase for a start, and constantly varying), the best that we can do is to measure the input voltage and current. The arrangement can be considered to be an electronic transformer....ie power in = power out. For an older brushed motor and controller, it would be true that the current is the same on both sides (of the ESC), but not for a brushless motor and controller. Brian.

The Shuttleworth management (not ModelAir) have changed the pricing structure for this event. Check up on the Shuttleworth website. https://www.shuttleworth.org/product/modelairfestivalofflight2023/ If you are just going to spectate and visit the sales stands then entry is free. You can go into the restaurant but not the hangars or Swiss Gardens. If you want to go into the hangars the cost will be £15.50 (unless you are an SVAS or Old Warden MAC member). You can enter the site via either the old gates or the new (long) drive. If you are going to fly then charges apply (£9.00 for a day or £14.00 for the weekend for BMFA and LMA members, £12.00/£18.00 for non-members) and you must enter via the new (long) drive. You will be given a wrist band to allow you to access the flying areas. You will also be able to go into the hangars if you wish at no extra charge. Tickets can be bought in advance on the website, or on the gate. If you have a non-flying passenger they get in free but won't have access to the hangars, unless they pay the same charges as a flyer. Rather confusing and the reasons for the changes haven't been given. I hope to be there on both days. Brian.

Something like this perhaps... it would need longer screws of course. It's only a rough drawing, no dimensions. It might even be possible to 3D print one, depending on the temperature around that part of the engine. Brian.

I wouldn't cut the existing bracket, which would ruin it forever and you probably wouldn't find another one. Better to remove the bracket and replace it with two L-shaped pieces of aluminium (or steel, or brass) each with with two holes for the mounting bolts. Perhaps making the carb. end of the heatshrink into two tabs and trapping those under the brackets will help to retain it in position. at least to see if the idea works in the first place. The 'bump' that would be in the trumpet, caused by the back of the timing case, can't easily be changed, just make the trumpet fairly long and shallow. If the improvised trumpet does reduce the carb spitting, perhaps a more permanent solution would then be to make a combined aluminium trumpet and bracket. Brian.

Another thing to check is that the engine still has compression once it has got hot. When it is hot and won't restart, take the plug lead off and turn the engine over slowly and listen at the exhaust (and possibly the carb.) for air hissing out. The valves can gradually recede into the valve seats, this reduces the clearance until it is minimal at cold but zero once hot (due to expansion of the valves). The affected valve (usually the exhaust valve) then doesn't seal and you end up with no compression (and no depression to draw in the fuel/air mixture). One the engine cools down, the valves shorten again and the cycle is repeated. If the clearance is too small, it can apparently be reset by carefully grinding a small amount from the end of the valve stem. I believe 6 and 8 thou. are the correct clearances for inlet and exhaust respectively. Brian.

At least he hasn't put up a photo of him wearing (only) them....

Video works fine on my PC, perhaps it's down to certain versions of Windows etc. The neon in the plug lead looks like it's glowing well, but it's difficult to tell what happens first at the point the engine stops... does the spark 'go out', stopping the engine, or does the engine stop running, causing the spark to go? Perhaps you could make a similar video, after the engine has died, pulling it over with full throttle to see if it sparks then. I wonder what the metallic ratting sound is when the motor is accelerated. Pinking perhaps, which could indicate a possible problem with the electronic timing advance. It might be a silly question, but that brass fuel tap is in the vertical position marked '0'; I assume that is in the on position? Brian.

The SLEC hatch catch won't work for your hatch. The fixed plate needs to be screwed to a vertical former, which you don't have in the battery opening as that is where the battery goes. Also the SLEC catch is too big.. it's about 2" depth from the outer surface of the hatch to the bottom of the fixed plate. I've had a few of these 'in stock' for many years and have yet to find a use for one. Brian.

I would suspect the latter unfortunately. The BMFA apparently lost money on each of the Barkston Nats in recent times, and they clearly took a lot of organisation. The MoD, in refusing the continued use of Barkston for the annual Nats, probably did the BMFA a favour as it gave it the perfect excuse to discontinue them. If active MoD sites are no longer available for this purpose, then the BMFA would have to look at suitable large privately-owned venues, which would only increase the cost further. In its current situation (membership static or dwindling, which won't be improved on if further CAA restrictions are imposed upon us), I can't see the BMFA being in a position to be able to hold anything like the old-style Nats in the near future. I would very much like to be proven wrong... Brian.