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Holding Your Nose

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Dai Fledermaus12/07/2018 15:33:23
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982 forum posts
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I've often seen it done, but never really understood why it's done, perhaps someone can explain. Having started the engine, the main needle adjusted for max revs albeit slightly rich, the model is then picked up and it's nose pointed to the sky and the main needle is again adjusted based on how the engine reacts.

If the fuel tank is pressurised, what difference does holding the nose up make?

Denis Watkins12/07/2018 15:36:19
2963 forum posts
141 photos

Makes no difference

And risks an unwanted haircut Dai

Gary Manuel12/07/2018 16:14:22
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I've heard it said that it makes no difference, but it does.

I've seen it for myself many times.

Engine tuned to perfection - Nose lifted - Engine cuts.

I'm assuming that it's because the engine is at the verge of being too lean and that lifting the nose up reduces the pressure of the fuel at the carburettor, causing the mixture to lean out to the point where it cuts. The same effect can be had by pinching the fuel pipe a little.

Jon - Laser Engines12/07/2018 16:21:03
3950 forum posts
153 photos

Its a pointless test that dates back to the early days. With modern engines that have considerably better fuel draw and/or are pressurised its really redundant.

Unless prop hanging its totally unrepresentative of conditions the model will see in flight. The engine will naturally go rich in flight due to unloading so its all good.

Just tune the engine for max revs and go fly.

The only time a nose up test is on any use is with a petrol engine as a nose up at idle can reveal an issue with the pump. That said, poor idle/starting and erratic running are symptoms more likely to catch the attention.

Gary Manuel12/07/2018 17:08:33
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As I said earlier, "I've heard it said that it makes no difference". I suspected that someone would come along and say it again.

How do you explain that I've seen it many times with my own eyes Jon? The last time I saw it was last weekend.

With regard to unloading in flight, there are plenty of aerobatic manoeuvres that require nose up, plenty of throttle and low airspeed - including climbing from take off. I've seen plenty of dead-sticks right after take off too.

Edited By Gary Manuel on 12/07/2018 17:10:57

ken anderson.12/07/2018 17:16:35
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8094 forum posts
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I've been a member of the nose up club for 30 years...……………….. told to do so when I first started flying IC and have done it ever since.dont know if the same applies to electric when we get to a third of the battery used? ...some one will come along no doubt and explain...wink 2 ...

ken anderson..... ne...1...nose up dept.

john stones 112/07/2018 17:31:52
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9816 forum posts
1462 photos

Ey up, another fed up thread, told you it wouldn't take long. face 1

C'mon you nose holder uppers.

Ron Gray12/07/2018 17:43:24
966 forum posts
255 photos

If the fuel tank is in the correct position and plumbed correctly and the engine has been correctly tuned then nose up is unnecessary.

Nigel R12/07/2018 17:46:18
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1538 forum posts
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It makes a few inches of difference to pressure at the needle.

I'm a shameless nose holderer upperer, when flying glow.

edit: unless its a fancy schmancy pumped engine. Then it is pointless.

Edited By Nigel R on 12/07/2018 17:47:20

Robin Colbourne12/07/2018 17:48:33
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390 forum posts
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Posted by Ron Gray on 12/07/2018 17:43:24:

If the fuel tank is in the correct position and plumbed correctly and the engine has been correctly tuned then nose up is unnecessary.

Surely that is the whole point of doing it ; to see if the engine is correctly tuned?

James Green212/07/2018 17:52:09
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37 forum posts
14 photos

I hold my nose up and down and give it a shake. I must be mad.

Denis Watkins12/07/2018 18:22:38
2963 forum posts
141 photos

Brilliant James, show it who is boss

No matter which way up we tune, on the ground, we are tuning a stalled prop.

At speed, and in the air, the prop starts to work and fly and unloads the motor somewhat.

Some clever people have a servo controlling the needle, but as has been said

Us sport flyers just need good plumbing, a good plug, and good fuel, and tune for max

That max is ground max, and becomes solid in flight

For as many nose ups that result in a stop that you see

You will also see nose up tuning deadstick at take off

My belief is that tickover has just gone on long enough to have excess fuel in the crankcase, making a puddle for the big end to bash into at throttle up.

Just take a second to hold the tail and throttle up any excess fuel, then go

Bob Cotsford13/07/2018 12:09:37
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7399 forum posts
419 photos

I used to do it going back before exhaust pressure became the norm. I carried on through habit, and all I can say is that I still got occassional sick runs with a new setup or a change. I even did it with a piped motor that had to be run really rich on the ground to come on the pipe in the air. If I didn't a helpful club member was bound to run up and point out that I hadn't gone through the ritual. Anything for an easy life, it was just easier to stick my nose in the air myself.

Jon - Laser Engines13/07/2018 12:39:58
3950 forum posts
153 photos
Posted by Gary Manuel on 12/07/2018 17:08:33:

As I said earlier, "I've heard it said that it makes no difference". I suspected that someone would come along and say it again.

How do you explain that I've seen it many times with my own eyes Jon? The last time I saw it was last weekend.

With regard to unloading in flight, there are plenty of aerobatic manoeuvres that require nose up, plenty of throttle and low airspeed - including climbing from take off. I've seen plenty of dead-sticks right after take off too.

Edited By Gary Manuel on 12/07/2018 17:10:57

Im not getting drawn into another long debate about it as i have explained it many times in the past. The test is pointless, it does not show if the tuning of the engine is incorrect and there is no changing that fact. Sure the engine you saw at the weekend stopped, why wouldnt it? the conditions it saw were beyond what it could cope with and certainly beyond what it would see in flight. Not many models sit stationary with their nose held high while screaming flat out. I am sure that most of my engines would stop if i did a nose up test with them, but in flight they are no problem and im sure that if your example took flight it would not stop.

Simply put, anyone who thinks this test will prove incorrect tuning is wrong, irrespective of how many anecdotes are thrown around, the fact remains it will not show poor tuning. If you are lucky it will give an indication of poor tank position, but even then there are better ways to find that out.

Gary, apologies if you take offence to this post. it is not my intention to offend anyone, but at the same time i work with glow engines every day and am quite well versed in their operation. If i had any doubts about this topic i wouldnt say a word.

Ian Jones13/07/2018 12:52:52
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3196 forum posts
1392 photos

Not perfect I agree but it does give the nearest indication we can get of what might happen on climb out after leaving the ground. The object being to try and avoid an Engine Failure After Take Off.

Gary Manuel13/07/2018 13:00:56
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1738 forum posts
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No offence taken Jon. You are entitled to your opinion even if it goes against what I've seen with my own eyes.

Chris Walby13/07/2018 13:08:24
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592 forum posts
114 photos

Tin hat on, but as a new boy

If its necessary to nose up at which point with the size of model do you stop doing it? I am sure the LMS guys don't node up their models, do they?

From a safety perspective I am not too keen on doing full throttle adjustments with it tethered especially if other people are about (on the start line) and holding onto my 70 size at full chat would be a challenge.

I would be even less keen nose upping my twin 70 model and would question being anywhere near someone trying to hold on to a 60cc at full tilt.

On the basis of safety the most damaging items would be the prop or spinner should there be a failure. The debris line would normally be in front of the model or at 90 degrees to the crankshaft. My point is that when doing nose up the prop arc goes behind the start line (all be it at height) assuming you are holding it straight.

Finishing thought, the most likely time for a catastrophic failure is when its most highly stressed, do you really want to be holding on to at the time?

oh it is Friday the 13th what could possibly go wrong wink

Andy Meade13/07/2018 13:15:53
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2409 forum posts
630 photos

Always have done a final tune with nose up to get a properly sorted engine. Can't see a reason to stop doing it now yes

Nigel R13/07/2018 13:16:01
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1538 forum posts
335 photos

I think this entire thread could be replaced with the phrase "your mileage may vary".

Jon - Laser Engines13/07/2018 14:03:35
3950 forum posts
153 photos
Posted by Gary Manuel on 13/07/2018 13:00:56:

No offence taken Jon. You are entitled to your opinion even if it goes against what I've seen with my own eyes.

Pleased to hear it Gary but please dont mistake the facts i present here as opinion.

All you guys still claiming it will give indications of XYZ im telling you it simply will not do that.

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