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Hi Nitro Glow Fuel

A Question For The Two-Stroke Cognoscenti.

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David Davis11/06/2018 14:20:41
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On 2nd June I participated in La Coupe Des Barons, a competition in which all of the models were an iconic French trainer dating from 1970 which has a wingspan of 1.66 metres or 65 inches. Engines were limited to 6cc two-strokes, 7cc four-strokes or 825 Watt electric motors.

Many competitors used the OS 35AX, several had tuned pipes but there was one model there, which had a tuned pipe, but which was head and shoulders above all of the others in terms of sheer speed. I kid you not, it went vertical and in the pylon race it succeeded in in passing 63 pylons. The second fastest model could only manage 52 and the third model 50, in other words the winning model was 17% faster. It was very impressive.

I can only conclude that the fuel which the model used contained a high proportion of nitro. I was under the impression that engines using high levels of nitro were difficult to adjust and very tempramental.

I've no wish to emulate this competitor but what are the advantages and disadvantages of running glow engines on very high nitro fuels?

john stones 111/06/2018 14:38:24
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Don't know what you would call high content, ran my O.S and Y.S on Coolpower 30% for long enough, never temperamental or fussy.

Denis Watkins11/06/2018 14:38:42
2906 forum posts
141 photos

Hi nitro fuel costs more

Is no more difficult to tune

Transitions better from low to high throttle

Runs the motor cooler

Does add some HP

Attracts moisture within the stored engine to produce damaging acid so clear fuel after use and use afterun oil

Nigel R11/06/2018 14:44:55
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"17% faster."

Amazing how much speed can be obtained from cleaning up the aerodynamics a bit. Did this particular model do any of that? Faired U/C wires? internal horns? "Tidier" cowling area? etc.

I always thought high nitro was easier to tune.

The engine might also be running a pump and monster carb to go with that pipe.

Was it "a little bit" high revving?

David Davis11/06/2018 15:05:43
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Well this is the model. It looks like any other Baron to me.

**LINK**

Edited By David Davis on 11/06/2018 15:09:44

Don Fry11/06/2018 15:59:32
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A proper tuned pipe can add a lot of revs. And hence a lot of power. Talk to the control line speed people.

Did it sound like the others, or higher pitched.

Another thought is that machine is simple film covered. Light and slippery. And has he replaced what he can with holed out depron, carbon fibre. Even getting 200 g off the weight, means a lower angle of attack, and more speed.

There used to be a power additive, di nitromethane, used to be used by drag racers, and illegally by pylon racers, before organisers caught on and supplied the fuel themselves. Who supplies the fuel. And before you ask David, no you can't get hold of it, legally. And don't enquire, lest Deuxème Bureaux hear and start sharpening their blackjacks.

But the proud modeller looks like a winner, evil, with a winners attitude to rules, within the rules, after a fashion, as written. Not perhaps as the judges imagined.

Big speed advantage. Doing something.

Frank Skilbeck11/06/2018 16:24:23
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the pilot might have also made a difference too.

David Davis11/06/2018 17:17:28
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Agreed Don and Frank he was a good pilot though the second place man was only 8 points behind him in the end and he was about 90 points ahead of the third man. In the limbo he tried twice to get under the rope at high speed to the chants of, "Sur le dos!" (On its back!) from his supporters, or maybe they were supporters of his rivals! Just imagine the skill required to fly a three channel trainer which would be constantly trying to right itself, inverted at high speed through a goal post! He was too high with his first pass and joined the Up Elevator Club on his second. By then he had already won the competition and the model did not seem to be too badly damaged.

Yes Don, his engine did seem to rev higher than anybody else's and you are allowed to use up to 50% nitro in the competition.

As for me, I was always brought up to be careful, some would say tight, with money and the thought of spending 154€ (about £136,) on an OS 35AX and plus the cost of some fancy pipe to use it in a light-hearted competition for three channel trainers, goes against the grain! I will be campaigning an SC32 which I picked up for peanuts on eBay. I've bought a Weston pipe for it and that's extravagant for me!

If you click twice on the left-hand side of the picture you can go back two pictures and see the model in flight. At least I can do that from my PC. I don't know anything about anyone else's.blush

Martin McIntosh11/06/2018 22:15:22
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Loads of pics on that link. Great stuff. Why can we not get such enthusiasm for an event like that in this country?

David Davis12/06/2018 05:57:23
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I have suggested on another thread that you could do the same thing in the UK with WOT 4s. You could restrict engine sizes as in La Coupe or go with a Formula Libre. Most flyers probably have a WOT 4 at home and you can buy an ARTF too. They are not too expensive and like La Coupe it could be quite a colourful event but you'd need to put big numbers on them as many would be finished in a classic white with Chris Foss decals colour scheme! If you used the same four tests as La Coupe: breaking balsa wood sticks; a pylon race; trying to cut a paper streamer and the limbo it could be quite a spectacle.

Having said that there is quite a bit of organisation to do. Assuming you fly in groups of ten you need ten judges to stand behind the pilots to keep score. You need a Contest Director with a first-rate public address system who can direct the time keeper to stop the clock if a potentially dangerous situation occurs. For example there was an incident when two models touched and one continued to fly with a good chunk of the tail plane missing; a dark blue model in the attached pictures. The CD felt that the model was a safety risk and ordered it to land. There being no shortage of broken pieces of 1/4" square balsa by this stage of the competition, the model was repaired and the repair was covered in gaffer tape! There is a picture of the repaired model in flight in the link.

You need a time-keeper. You need a couple of fast runners to go out to retrieve downed models which have landed in potentially dangerous positions according to the CD. In that situation the CD stopped the clock and directed the remaining competitors to cruise about at a high altitude. You may need permission from the authorities to hold the event. You need three trainers with pilots to tow the crepe paper ribbons and you need someone who is highly computer literate with a good lap top to keep score. You need a team to go out and put up notices in the surrounding countryside to direct contestants to the venue. You need a qualified first aider. You need a team of guys to erect the pylons and limbo goalpost. On the day, one of the pylons had already been installed and remained in place all day long. The second pylon was simply moved after the last pylon round had been flown and was installed as the second goalpost of for the limbo event.

Finally, bear in mind that La Coupe is an all-day event. You'd need a big club and a big venue to hold something like this. Parking, catering, there would be quite a bit to do.

Well done Vol Libre, your organisation was superb! I got talking to one of the other contestants who had competed in all fourteen Coupes. He told me that in the early Coupes quite a few people were still using FM radios and it was necessary to ensure that there were no frequency clashes. Imagine that!

Best of luck! It was a great day out.

Levanter12/06/2018 08:48:05
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Hi David

Fabulous photos, great flying site and enormous fun. Aeromodelling at its best I think.

Levanter

Engine Doctor12/06/2018 11:23:44
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Posted by David Davis on 11/06/2018 17:17:28

As for me, I was always brought up to be careful, some would say tight, with money and the thought of spending 154€ (about £136,) on an OS 35AX and plus the cost of some fancy pipe to use it in a light-hearted competition for three channel trainers, goes against the grain! I will be campaigning an SC32 which I picked up for peanuts on eBay. I've bought a Weston pipe for it and that's extravagant for me!

Hi David . The SC 32 with a Weston pipe is a really good combination and the 36 is even better.. SC 32 is virtually identical inside and out to the OS 32 at a fraction of the cost and you don't have the problem of the chrome plating shedding from the cylinder liner , a known issue with OS engines inc the AX range ! I ran my OS 32 SX set up for years and they really went well. They went even better if oil content in fuel is reduced . I had my fuel mixed to 17% synthetic oil and 20% nitro. If you use Westons Pro-Synth 2000 fuel it will really howl and will run a lot cleaner.

David Davis12/06/2018 11:34:15
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Thanks for the advice ED. I am a long way from the nearest Westons Pro-Synth supplier but I have some Southern Model Craft 85/15 straight. Guess I could add some nitro to that!

Engine Doctor14/06/2018 10:51:06
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Posted by David Davis on 12/06/2018 11:34:15:

Thanks for the advice ED. I am a long way from the nearest Westons Pro-Synth supplier but I have some Southern Model Craft 85/15 straight. Guess I could add some nitro to that!

Hi Worth trying SMC fuel first I reckon ,it might be fine on it.

Weston do post fuel via courier . Might be worth a call for cost ?

Southern model craft is a good fuel . I use that with reduced oil 17% synthetic and 10 or 20% nitro depending which engine/ model I'm using . I wont use any fuel with castor oil in it unless its a diesel or vintage engine with iron piston/cylinder.

Jon - Laser Engines14/06/2018 11:00:58
3916 forum posts
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leeds models and a few others will ship fuel too. The techpower range from model technics is good if you want higher nitro.

Im in full agreement with ED about castor. Its day is done in modern engines and with a decent synthetic 10% oil is likely to be more than enough. My 21 size nitro car engine runs 16% nitro and 10% oil. Its doing nearly 40,000rpm flat out so if 10% oil is enough for that its enough for anything!

David Davis14/06/2018 11:20:42
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Thank you for the information gentlemen, but it does raise two further points.

  1. I already have considerable stocks of Southern Modelcraft fuel, at least 50 litres, so adding nitro to straight fuel would seem to be the most cost-efficient opotion.
  2. If I choose to by fuel from any of the shops mentioned above, will any of these firms ship fuel to France which is where I live nowadays?
Martin Harris14/06/2018 11:21:18
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Posted by David Davis on 12/06/2018 11:34:15:

Thanks for the advice ED. I am a long way from the nearest Westons Pro-Synth supplier but I have some Southern Model Craft 85/15 straight. Guess I could add some nitro to that!

Do you have a source for obtaining nitromethane - if France is adhering to the same euro ruling, we now need a licence to hold it - or any fuel with nitro content from 30% by weight (25% by volume in typical fuel) upwards...

David Davis14/06/2018 14:45:31
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Posted by Martin Harris on 14/06/2018 11:21:18:
Posted by David Davis on 12/06/2018 11:34:15:

Thanks for the advice ED. I am a long way from the nearest Westons Pro-Synth supplier but I have some Southern Model Craft 85/15 straight. Guess I could add some nitro to that!

Do you have a source for obtaining nitromethane - if France is adhering to the same euro ruling, we now need a licence to hold it - or any fuel with nitro content from 30% by weight (25% by volume in typical fuel) upwards...

Our Club President seems to be able to get hold of it.

Edited By David Davis on 14/06/2018 14:45:49

Don Fry14/06/2018 15:02:25
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Hey ho, don't suppose either of you want to make explosives. But it's illegal.

Regulation (EU) No 98/2013 of the European Parliament and of the Council of 15 January 2013 on the marketing and use of explosives precursors

Edited By Don Fry on 14/06/2018 15:03:27

John Duncker24/06/2018 00:58:46
12 forum posts
7 photos
Posted by Jon - Laser Engines on 14/06/2018 11:00:58:

l

Im in full agreement with ED about castor. Its day is done in modern engines and with a decent synthetic 10% oil is likely to be more than enough. My 21 size nitro car engine runs 16% nitro and 10% oil. Its doing nearly 40,000rpm flat out so if 10% oil is enough for that its enough for anything!

I would disagree with 10% being sufficient for aero use. It is OK in cars because they never run at full throttle for more than a second or two.

15 % was my SWAG for minimum and as I was nostalgic about the smell of caster added 2% for luck and also in the belief that it might provide some last ditch lube in case of a lean run.

I used to run a OS 15 CVA on 25% nitro straight out of the box for 12th scale combat.

I also used the MVVS 20 with the mini pipe. These would not run out of the box on 25% requiring a head shim to lower the compression ratio.

I never went beyond 35% nitro but was told that beyond 40 % you needed to add 2 to 3 % of nitrobenzene to get the nitromethane to mix. NB I was also told that there were considerable health risks associated with nitrobenzene.

This mix came from Bill Wisniewski who knew a thing or two about going fast.

The fuel I have been using is as follows: 15% castor oil, 5% polyoxide oil (which is available from outboard boat racing shops), 10% nitro-benzine, 55% nitro-methane, 15% methanol. This should be mixed at least one week before using and stored in dark bottles.

It worked really well in a Eta 29 in a class B team racer.

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