Archive for April, 2014
Posted by PeterVRC |
Apr 18, 2014 @ 07:48 AM | 9,254 Views
I will finish this more later.....
It has finally come to light how there is a big issue with being tail heavy!
Not the usual 'It will be hard to control', 'It will be over-sensitive', though they are still true also..... but the 'Stuck in a hover" potential, which will leave a plane with no ability to exit from that!!
I must have been a bit slow to co-relate the data (!!), but via an F-35, F-22 and F-4, all encountering that BIG issue, it finally all makes sense!
If you are tail heavy beyond "Point X" - and that does not mean a "ton", it could be just 10mm more rearwards CofG, or whatever, per a given plane - once the plane pivots into an AoA greater than "Angle Y", it will reach an equilibrium of factors that KEEP it there!
High AoA... like 70deg or more... which then causes huge drag.... needs max power just to stop it falling out of the sky.... has no 'proper' airflow over control surfaces, so they become TOTALLY inefficient and have no authority at all then.
So it is then STUCK in this state, because nothing you have control over can achieve anything - except reducing/cutting power which will make it descend if you do that correctly... or totally stall out and fall out of the sky if you do not!
And I mean it is STUCK there..... it is not going to slowly come out of it... because the equilibrium of all factors is just right to sustain it, and as mentioned there are no controls YOU have to alter that.
A gust of wind might be...Continue Reading
It has finally come to light how there is a big issue with being tail heavy!
Not the usual 'It will be hard to control', 'It will be over-sensitive', though they are still true also..... but the 'Stuck in a hover" potential, which will leave a plane with no ability to exit from that!!
I must have been a bit slow to co-relate the data (!!), but via an F-35, F-22 and F-4, all encountering that BIG issue, it finally all makes sense!
If you are tail heavy beyond "Point X" - and that does not mean a "ton", it could be just 10mm more rearwards CofG, or whatever, per a given plane - once the plane pivots into an AoA greater than "Angle Y", it will reach an equilibrium of factors that KEEP it there!
High AoA... like 70deg or more... which then causes huge drag.... needs max power just to stop it falling out of the sky.... has no 'proper' airflow over control surfaces, so they become TOTALLY inefficient and have no authority at all then.
So it is then STUCK in this state, because nothing you have control over can achieve anything - except reducing/cutting power which will make it descend if you do that correctly... or totally stall out and fall out of the sky if you do not!
And I mean it is STUCK there..... it is not going to slowly come out of it... because the equilibrium of all factors is just right to sustain it, and as mentioned there are no controls YOU have to alter that.
A gust of wind might be...Continue Reading
Comments (0)
Posted by PeterVRC |
Apr 11, 2014 @ 11:42 PM | 19,495 Views
Seeing I have a few 7S powered aircraft now, SPARKING when you connect a battery up is a notable issue. Connectors get charred... their tips/edges eaten away by the fusing... and it can't be good for ESC's really.
This issue really begins at about 5S, and by 6S it really is a problem that should be dealt with. Then 7S upwards... DEFINITELY needs attention!
An Anti-Spark system is just a method of making a Battery to ESC connection WITH RESISTANCE in-line so that the ESC Capacitors do not charge up in "An instant" and thus draw a huge amount of current at that instant - that "Instant' being the split second your connectors first touch each other the slightest bit! And that is what causes that "Arc Welding" spark!
Theoretically, a Capacitor connected to a Voltage source, with zero resistance in-line, will charge INSTANTLY.... and the 'opposite side" of that is that the current level will be INFINITE for that micron in time! Of course the battery can only supply X Amps.... but at 6S levels that could be 200 Amps+ !! Luckily it is only for the micro second!
You can buy some nice connectors these days that have the Anti-Spark Resistor system built into them. So for $8 to $10 or so you can have a very easy solution.
For now I am using a home-made system... outlined below. It costs under $1 per plane....
This issue really begins at about 5S, and by 6S it really is a problem that should be dealt with. Then 7S upwards... DEFINITELY needs attention!
An Anti-Spark system is just a method of making a Battery to ESC connection WITH RESISTANCE in-line so that the ESC Capacitors do not charge up in "An instant" and thus draw a huge amount of current at that instant - that "Instant' being the split second your connectors first touch each other the slightest bit! And that is what causes that "Arc Welding" spark!
Theoretically, a Capacitor connected to a Voltage source, with zero resistance in-line, will charge INSTANTLY.... and the 'opposite side" of that is that the current level will be INFINITE for that micron in time! Of course the battery can only supply X Amps.... but at 6S levels that could be 200 Amps+ !! Luckily it is only for the micro second!
You can buy some nice connectors these days that have the Anti-Spark Resistor system built into them. So for $8 to $10 or so you can have a very easy solution.
For now I am using a home-made system... outlined below. It costs under $1 per plane....
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