Dave,
doing some basic calcs using good old ohms law and ignoring things such as resistence losses va the cable and connectors, we will assume they are 0 ohms. We also assume it is running at max power consumption.
Motor specs: rpm/v 1550 kv
Motor voltage: 22v
motor power consumption at max rating: 2400W
That's the max continuous the motor is rated to, not the max it will draw, this can sometimes be a fair bit more. it depends a lot on the fan.
P=IE
Therefore;
I=P/E
I=2400/22
I=109A
The ESC that comes with the kit is 100AQ but assume some efficiency losses in cables, motor etc of around 10% hence the 100A supplied ESC is just within parameters.
Again, this a presumption that the motor will only draw a max of 2.4kw. With strong packs this can go up a fair bit if they can deliver the goods. Also, as with most HK items, ESC included, they might rate them for one thing, but whether they can handle it continuously is another. I have found with most of their ESC's running them around the 80% of rated current is a safe barrier. Having said that I have run some of their sentillon range at 100-110% of their rated max (for takeoffs) with good success. The YEP range they now carry are awesome!
Lipos are 5000mA/h 6S 40C.
so . . . 5000mA/h x 40C = 200 mA/h discharge rate, Therefore 200mA/h / 1000 = 200A constant dischrage rate at max.
Calculating flight time and assume average of say 50% throttle setting throughout the flight....
(5000mA/h / 1000) / 50A=0.1
0.1 x 60 = 6 mins flight time @ 50%.
So will need to keep my throttle settings moderate so as to a) not run out of battery; and b) not burn out the ESC!!
Appling the 80% rule will give a 5 min flight which should be ample.
Lots of assumptions here..... Firstly, that the Li-pos will deliver their rated current in a linear fashion for their entire capacity. never the case. Although the 40c rating sounds like it should be more than enough, the is significant variance between brands and I have found extensions of my flight time with same capacity/cell packs but of a differenet brand. A lot of the cheaper packs voltages will sag under load, so you don;t get the same performance even they they are rated the same. Second is that you will not need more than 50% thrust to keep flying. My hawk is about that, but most of my other EDF have needed more throttle to look and feel right in the circuit. you won't know this for sure until you've flown it and can then make the call for yourself. Firstly you need to get off the ground and up on step into the circuit. that will require WOT for a period of time. My hawk draws 104A at WOT, but comes down to about 60A at 50% throttle. Then you might need to do a go around which will require WOT again for another burst. I normally calculate my flight times based on experience with the model and not paper based calc's. Ie, I fly my first flights short, 3mins or so, and then monitor how much current I put back into the packs. you can then average this out and calculate how long in real world flying terms you can expect to fly the model for safely. They you must also bank of the fact that you will not get the full pack performance for the entire capacity, and then also you should't run them down too much further past the 80% for longevity.
EDF's are very harsh on their packs. I use 70c rated packs and the cheaper ones still sag under load, so even though they state on the label that they are able to handle a 40c load and not be damaged, that does not tell you how well they will hold the voltage under that load. as your voltage sag's, you need to apply more throttle to get the same RPM (therefore performance) so you work your packs harder which makes them hotter, and so begins the downward spiral.
QED
Now as for thrust and flying weight. Let's assume the model comes in at correct AUP of 3.6kg, or 8 lbs. From the research I have found the fan unit fitted should develop about 3.45kg of thrust. Or 7.6 lbs.
Its HK, your dreaming that the AUW will be correct!
They have got one of these flying at 3.5kg with all the landing gear removed so add at least another 450g to that. They also mod'd the internals to get the packs into the best possible position. I would bank on more like 4.2 to 4.4kg. which isn't bad for this size of model, and not really concern really. Second problem is that the rate thrust of 3.45kg is often done not in a model (ducting losses, which will equate to something around 0.5kg-1kg of thrust depending on length of ducts inlet and exhaust, smoothness, etc...) and also powered by a power supply that will maintain a constant voltage and deliver as much current as it wants. Installed in a model things are a little different..... For installed thrust, I would plan on something more like 2.8-3kg thrust.
That is a thrust to weight ratio of 1:0.96 - almost 1:1 so should really get up and get going. Of course the crappy inlets are going to restrict that. If I can get around 1:0.75 I'd be quite happy. I'll fabricate some sort of ductings and open up the inlets to help with that inlet flow.
Refer above, these calcs will be out, which then also means that flying at 50% assumption further up is also compromised... Inlet make a more noticeable difference in the amount of dynamic thrust, static thrust is not majorly affected by inlet ducts!! rt3232 is right, a smooth radius inlet lip on the fan is far more important if it's not installed into ducting..
cheers
Peter