TF GS P47 Build - yeah another bloody one!!
08-10-2014, 01:41 PM
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Got out again with the Astrogoh on Sunday for a few flights. Unlike previous sunday it was very busy so only got 3 flights in. There was some clown with a turbine F18 screaming around on full throttle and no regard for any other models in the circuit. Amazing there was not a head on with this idiot. Anyway . . .
More progress on the P51 repairs. Re-applying blade putty filler and then rubbing back then re-apply some more. Fixed some cracks in the fuz and laid down 6oz cloth on inside to strengthen it a bit.
Pulled the cowl apart and re-plumbed the tank correctly this time. It now pressurises correctly with the cline regulator.
Some repairs to bottom of the cowl to do yet and have to do a layup to make the bottom chin inlet - hard to explain.
Looking forward to getting it completed so I can get back to the P47.
More progress on the P51 repairs. Re-applying blade putty filler and then rubbing back then re-apply some more. Fixed some cracks in the fuz and laid down 6oz cloth on inside to strengthen it a bit.
Pulled the cowl apart and re-plumbed the tank correctly this time. It now pressurises correctly with the cline regulator.
Some repairs to bottom of the cowl to do yet and have to do a layup to make the bottom chin inlet - hard to explain.
Looking forward to getting it completed so I can get back to the P47.
08-10-2014, 03:41 PM
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Hi Pete
Well at least you are in the shop doing good things
My oldest flying buddy just broke his P-51 To slow on final and at about 3ft off the ground, tip stall hit at an angle and took out the gear, so now he has 2 in repair his yellow spitty and the 51.
my 47 is ready to go but been working on my Corsair checking things out, it has not been off the shelf for a year air system is a little sticky, so cleaning things and adding a bit of oil, maybe get out next week if all checks out, with our field what ever wind it has to be out of the south so we will see.
Cheers Bob T
Well at least you are in the shop doing good things
My oldest flying buddy just broke his P-51 To slow on final and at about 3ft off the ground, tip stall hit at an angle and took out the gear, so now he has 2 in repair his yellow spitty and the 51.my 47 is ready to go but been working on my Corsair checking things out, it has not been off the shelf for a year air system is a little sticky, so cleaning things and adding a bit of oil, maybe get out next week if all checks out, with our field what ever wind it has to be out of the south so we will see.
Cheers Bob T
08-10-2014, 03:56 PM
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Hey Pete,
Was the F-18 pretty small and grey? young driver? if so, and I think it would have been, that's Andy, excellent on the sticks. If people were concerned with colliding with him did they get out of the way for him? I've landed plenty of times at my club because of who was coming up to take off, and not normally because of the performance difference from their model, more because I didn't trust the guy behind the sticks!
if they make space in the circuit for a $100 trainer because he has a right to fly it at the club, they should make space for a $7000 Jet too... P.S. that pocket rocket was clocked at 330 Km/H on the radar!
I can see the problem with the mustang in those two pic's you've posted. I've said it before and i'll say it again... dump that stupid super tiger glow monster and replace it with a half decent gasser!!! I've seen you fly that mustang for many years now and that motor has never really been super reliable. you never have faith in it and you can see that in the way you fly the model.How many times have you repaired it because of the engine? There was that one time at tin can bay where your wheel fell off on takeoff, I remember it bouncing down the strip and shaneo and I going for a jog to go fetch it. Don't know what was funnier, the wheel coming off or me and shaneo going for a jog?
But stop breaking the Mustang and give it a decent donk!
It's eating into your P-47 building time!
Now your Vamp,
Are you working all this week? I'm on arvo's, so could pop round during the day before work.
Hate to break it to you, but I seriously doubt you'll get it off the ground on 6s. what size motor is it? guessing by the Kv alone, your going to be looking at something closer to 8s packs and maybe even 10s, but i think the motor is too hot a wind for 10s if it's HK's finest quality! for 6s to give half decent performance on that span you'll need to hit the 3.5kg ready to fly weight. for a glass fused jobbie, I think you might struggle. Have you run up your fan yet?I have an eMeter so we can check to see what it's pulling, but you might just scrape into the 6min flight time mark. depends alot on what batteries you intend on running. And you need to check to see if it needs balancing. If your not really really up to speed with electric's, you've definitely jumped into the deep end! but we can get you up and going! Still watching the German thread to see what comes out of the CoG discussions. Most people I know don't use EC5's. I use these in my 90mm setups and so do most people. HK now sell their larger packs with these connectors fitted, so you don't even have to change them out. My current 90mm pulls 104A at WOT, and they get a little warm, but no at much as the the 10AWG wire or the packs, so they are up to the task. Makes it much easier to swap out packs and try different packs if you have the same connecter as everyone else.
http://www.hobbyking.com/hobbyking/s...0pcs_set_.html
Catch ya soon!
Thanks
dave
Was the F-18 pretty small and grey? young driver? if so, and I think it would have been, that's Andy, excellent on the sticks. If people were concerned with colliding with him did they get out of the way for him? I've landed plenty of times at my club because of who was coming up to take off, and not normally because of the performance difference from their model, more because I didn't trust the guy behind the sticks!
if they make space in the circuit for a $100 trainer because he has a right to fly it at the club, they should make space for a $7000 Jet too... P.S. that pocket rocket was clocked at 330 Km/H on the radar! I can see the problem with the mustang in those two pic's you've posted. I've said it before and i'll say it again... dump that stupid super tiger glow monster and replace it with a half decent gasser!!! I've seen you fly that mustang for many years now and that motor has never really been super reliable. you never have faith in it and you can see that in the way you fly the model.How many times have you repaired it because of the engine? There was that one time at tin can bay where your wheel fell off on takeoff, I remember it bouncing down the strip and shaneo and I going for a jog to go fetch it. Don't know what was funnier, the wheel coming off or me and shaneo going for a jog?
But stop breaking the Mustang and give it a decent donk! It's eating into your P-47 building time!Now your Vamp,
Are you working all this week? I'm on arvo's, so could pop round during the day before work.
Hate to break it to you, but I seriously doubt you'll get it off the ground on 6s. what size motor is it? guessing by the Kv alone, your going to be looking at something closer to 8s packs and maybe even 10s, but i think the motor is too hot a wind for 10s if it's HK's finest quality! for 6s to give half decent performance on that span you'll need to hit the 3.5kg ready to fly weight. for a glass fused jobbie, I think you might struggle. Have you run up your fan yet?I have an eMeter so we can check to see what it's pulling, but you might just scrape into the 6min flight time mark. depends alot on what batteries you intend on running. And you need to check to see if it needs balancing. If your not really really up to speed with electric's, you've definitely jumped into the deep end!
but we can get you up and going! Still watching the German thread to see what comes out of the CoG discussions. Most people I know don't use EC5's. I use these in my 90mm setups and so do most people. HK now sell their larger packs with these connectors fitted, so you don't even have to change them out. My current 90mm pulls 104A at WOT, and they get a little warm, but no at much as the the 10AWG wire or the packs, so they are up to the task. Makes it much easier to swap out packs and try different packs if you have the same connecter as everyone else.http://www.hobbyking.com/hobbyking/s...0pcs_set_.html
Catch ya soon!
Thanks
dave
Last edited by ticketec; 08-10-2014 at 04:08 PM.
08-10-2014, 05:00 PM
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Hi Pete
Well at least you are in the shop doing good things My oldest flying buddy just broke his P-51 To slow on final and at about 3ft off the ground, tip stall hit at an angle and took out the gear, so now he has 2 in repair his yellow spitty and the 51.
my 47 is ready to go but been working on my Corsair checking things out, it has not been off the shelf for a year air system is a little sticky, so cleaning things and adding a bit of oil, maybe get out next week if all checks out, with our field what ever wind it has to be out of the south so we will see.
Cheers Bob T
Well at least you are in the shop doing good things
My oldest flying buddy just broke his P-51 To slow on final and at about 3ft off the ground, tip stall hit at an angle and took out the gear, so now he has 2 in repair his yellow spitty and the 51.my 47 is ready to go but been working on my Corsair checking things out, it has not been off the shelf for a year air system is a little sticky, so cleaning things and adding a bit of oil, maybe get out next week if all checks out, with our field what ever wind it has to be out of the south so we will see.
Cheers Bob T
Good you are getting your birds ready for flight again. I only have my little pica spit as a warbird to fly at the moment.
08-10-2014, 05:18 PM
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I went flying my last IMAC of the year. After the festivities a scale meet broke out. A TF P-47 and a Ziroli Corsair showed up from the IMAC guys Trailers. It seems that there is a trend from the groop of guys I've been flying with for the last 4 yrs towards scale. John Boyko (I hope I didn't butcher the spelling of his name.) A well known Nationaly, Scale Competior also was there and we had some conversation about me competing with my P-47. I got a nice explanation on how scale contest work and what was needed to compete with. Just what I needed. Another thing to think about. I may have to get the 47 ready over the winter and give it a shot.
08-10-2014, 05:25 PM
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Hi old Tom
Did the completion thingy aloooong time ago was fun, So I say go for it.
But now I just like to watch and do my own thing might be the ageing thingy
Cheers Bob T
Did the completion thingy aloooong time ago was fun, So I say go for it.
But now I just like to watch and do my own thing might be the ageing thingy
Cheers Bob T
08-10-2014, 05:28 PM
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Old Tom:
Hey, can you e-mail me at [email protected] I am about to build a redwing SBACH and I read your build thread from 2010. I would like to ask you some questions.
Thanks
Glenn
Oz:
What is left to do on the P-51 and what do you have to do to finish the P-47? Wishing you well
Hey, can you e-mail me at [email protected] I am about to build a redwing SBACH and I read your build thread from 2010. I would like to ask you some questions.
Thanks
Glenn
Oz:
What is left to do on the P-51 and what do you have to do to finish the P-47? Wishing you well
08-10-2014, 08:57 PM
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Dave,
see below.
Jet:
No idea who he was though somebody said Lee. Yes it was a smallish grey jobbie. It was exceptionally fast and he had no regard for any other models trying to fly a circuit. As soon as I heard him start up I landed as did another aircraft. He was flying through models flying in circuit. Damn dangerous.
P51:
I hear you however the model is set up with the ST2500 and I can’t afford another donk. The motor is fine, just needs to have the regular maintenace and checks done. As I have been so unstable in my personal life it gets neglected then I decide to trot it out and things go wrong. I had replumbed it a few weeks ago after a fuel line split (old fuel tube) and I hooked the lines back to front to the cline regulator. I should have done a ground run first which would have picked it up. I had trouble starting it on the day and the tank would not pressurise, when I finally got it running I had trouble tuning it. I should have relaised what was wrong and left it on the ground but insisted on trying to fly and crashed. My fault not the engine.
As for that wheel I remember that, too funny especially you blokes running after it. Again not the engines fault.
So again because I have been out of touch with my models I am overlook basic things that a few years ago would not have been overlooked. I am now out at the field most Sundays and in the shed a lot so getting back on top of all of this again.
Vampire:
Features:
• High voltage 100A ESC included
• 12 Blade Dr. Mad Thrust Alloy 90mm EDF Unit with 1550Kv motor pre-installed
• Flying Weight: 3600g
Motor: B4074 1550kv Brushless Motor
ESC: High Voltage 100A Opto with 5A UBEC
All new to me this side. I bought 6S, 5000mA, 40C packs. The model is very light so should be able to hit projected AUP. If I can do something with inlet ducts it can only help the equation.
Havent done a thing on it yet. I have to purchase some EC5 connectors still, I’m not using the supplied ones as they have exposed copper and too dangerous. Till then the lipos are safely stored in a 7.62mm sealed steel ammo box outside the shed and well away from the edge of it. I’m a bit paranoid about them.
I’d be happy for a flight of 5 to 6 mins. That was about all I was planning for it. Is there a thread on these in Germany? Got a link to it?
I’m normally home by 4 to 4.30 but till I get the EC5 connectors and sort out something for the inlet ducts I won’t be doing much.
cheers
Peter
see below.
Jet:
No idea who he was though somebody said Lee. Yes it was a smallish grey jobbie. It was exceptionally fast and he had no regard for any other models trying to fly a circuit. As soon as I heard him start up I landed as did another aircraft. He was flying through models flying in circuit. Damn dangerous.
P51:
I hear you however the model is set up with the ST2500 and I can’t afford another donk. The motor is fine, just needs to have the regular maintenace and checks done. As I have been so unstable in my personal life it gets neglected then I decide to trot it out and things go wrong. I had replumbed it a few weeks ago after a fuel line split (old fuel tube) and I hooked the lines back to front to the cline regulator. I should have done a ground run first which would have picked it up. I had trouble starting it on the day and the tank would not pressurise, when I finally got it running I had trouble tuning it. I should have relaised what was wrong and left it on the ground but insisted on trying to fly and crashed. My fault not the engine.
As for that wheel I remember that, too funny especially you blokes running after it. Again not the engines fault.
So again because I have been out of touch with my models I am overlook basic things that a few years ago would not have been overlooked. I am now out at the field most Sundays and in the shed a lot so getting back on top of all of this again.
Vampire:
Features:
• High voltage 100A ESC included
• 12 Blade Dr. Mad Thrust Alloy 90mm EDF Unit with 1550Kv motor pre-installed
• Flying Weight: 3600g
Motor: B4074 1550kv Brushless Motor
ESC: High Voltage 100A Opto with 5A UBEC
All new to me this side. I bought 6S, 5000mA, 40C packs. The model is very light so should be able to hit projected AUP. If I can do something with inlet ducts it can only help the equation.
Havent done a thing on it yet. I have to purchase some EC5 connectors still, I’m not using the supplied ones as they have exposed copper and too dangerous. Till then the lipos are safely stored in a 7.62mm sealed steel ammo box outside the shed and well away from the edge of it. I’m a bit paranoid about them.
I’d be happy for a flight of 5 to 6 mins. That was about all I was planning for it. Is there a thread on these in Germany? Got a link to it?
I’m normally home by 4 to 4.30 but till I get the EC5 connectors and sort out something for the inlet ducts I won’t be doing much.
cheers
Peter
08-10-2014, 09:04 PM
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Tom,
yes mate get into it, get some documentation together and enjoy!
Glenn,
P51 still has some minor repairs to be done to the cown chin with new layup with it goes over the curved area and a split in it. Not a biggie.
some work in the cockpit where some of the scale fitting came loose, again not a biggie.
Wing is repaired, just have to finish the filling and sand back then shoot some primer, do panel lines on repaired area, small amount of rivets then top colour and touch up the stars/bars under the wing.
P47 needs some reinforcing of the retract rails with CF and epoxy, might even make an alloy doubler. not sure yet.
Then dummy antenna mounting point.
Cowl mounts to be completed.
small amount of filling and primer to hanger rash areas.
Paint the cammo scheme, stars/bars and nomecleature, systems fit out and test runs prior to test flight. Has been at this stage for about 2 1/2 years
cheers
P
yes mate get into it, get some documentation together and enjoy!
Glenn,
P51 still has some minor repairs to be done to the cown chin with new layup with it goes over the curved area and a split in it. Not a biggie.
some work in the cockpit where some of the scale fitting came loose, again not a biggie.
Wing is repaired, just have to finish the filling and sand back then shoot some primer, do panel lines on repaired area, small amount of rivets then top colour and touch up the stars/bars under the wing.
P47 needs some reinforcing of the retract rails with CF and epoxy, might even make an alloy doubler. not sure yet.
Then dummy antenna mounting point.
Cowl mounts to be completed.
small amount of filling and primer to hanger rash areas.
Paint the cammo scheme, stars/bars and nomecleature, systems fit out and test runs prior to test flight. Has been at this stage for about 2 1/2 years
cheers
P
08-11-2014, 04:26 PM
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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
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.
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.
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.
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.
cheers
Peter
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
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.
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.
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.
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.
cheers
Peter
Last edited by Peter_OZ; 08-11-2014 at 05:08 PM.
08-11-2014, 06:15 PM
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Pete
Way Back when I worked in/for engine test cells (privet contractor0 at Kelly AFB on the big fan engines The shape of the inlet just aft of the nose ring, the curve was critical to get the correct air flow In/thru the fans, don't have a clue if it will make any difference on a model, but being a ducted fan it might, so just a heads up
Cheers Bob T
Way Back when I worked in/for engine test cells (privet contractor0 at Kelly AFB on the big fan engines The shape of the inlet just aft of the nose ring, the curve was critical to get the correct air flow In/thru the fans, don't have a clue if it will make any difference on a model, but being a ducted fan it might, so just a heads up
Cheers Bob T
08-11-2014, 07:09 PM
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oh yes mate you are correct, NACA ruled inlet ducts do have a huge impact but on this thing even if I just add ducts to the wing root area will suffice, its not overly critical.
Hopefully HK will do the right thing and supply the missing ducts.
Hopefully HK will do the right thing and supply the missing ducts.
08-11-2014, 07:53 PM
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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
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
Having shot all that down, from reports, it is actually a nice flier and does do ok on 6s. performance will not be stellar at all, most 6s 90mm models just fly around doing circuits and not really perform like a jet model should. you normally need to be somehwere around the 3+kw to get good (not awesome) jet like performance in this size model, so 8s to 10s. I think you will find that you will need to work a fair bit to do a loop etc, but that doesn't make the model not enjoyable. My foamie 70mm version is the same, and I've left it like that because it's more scale, just have to be more on top of it when flying because you wont have "model" levels of power to get you out of trouble!
Pic's of the one that has just flown in Germany.
Thanks
Dave
Last edited by ticketec; 08-11-2014 at 08:04 PM.
08-11-2014, 08:17 PM
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yes well my very first go at electric and EDF and I did state the assumptions used. I'm on the learning curve so don't shoot me down too soon.
All theoretical calculations based on what I think will happen. As with any engineering scenario one has to state the parameters that are used as basis of canculation.
i.e flying at an average of say 50% but realistically bank on say 80% throttle average.
I did also point out that I expect inlet losses to bring throust to weight ratio down to about 1:0.75.
Tend to agree that the weak link is the ESC and that the lipos will supply more then ESC can handle and that the fan motor is like to exceed it rated power consumption.
Have to start somewhere and see how it performs, or doesn't. 3 mins then land and charge the pack to see how much it take to charge back up is a good approach. I have one of the revelex chargers which i can hook up to my 12v flight box battery.
cheers
P
All theoretical calculations based on what I think will happen. As with any engineering scenario one has to state the parameters that are used as basis of canculation.
i.e flying at an average of say 50% but realistically bank on say 80% throttle average.
I did also point out that I expect inlet losses to bring throust to weight ratio down to about 1:0.75.
Tend to agree that the weak link is the ESC and that the lipos will supply more then ESC can handle and that the fan motor is like to exceed it rated power consumption.
Have to start somewhere and see how it performs, or doesn't. 3 mins then land and charge the pack to see how much it take to charge back up is a good approach. I have one of the revelex chargers which i can hook up to my 12v flight box battery.
cheers
P
08-12-2014, 04:16 AM
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We the guys I fly with are using the little Hi-tech meter to check batt's after flight, and have found DON'T draw down below 28 % 3S to !0S makes the packs last a lot longer, but I am only running 3S packs. Don't know if this means much but just some info from our side.
Cheers Bob T
Cheers Bob T
08-13-2014, 02:16 PM
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Bob,
will have to get myself some sort of watt meter, will pick Dave, aka tictec brain on that as he has been flying sparkies for a long time and this is my first venture into the dark side, odd given my professional background!
We had a day off here in brisbane for ekka show holiday, you septcs will need top gogle it, probably equates to your state fair.
anyway got quite a bit done on the mustang, shot some primer, applied a bit more red filler here and there and fitted a new dummy ident light (red) under the wing. Started doing the repairs to the cowl area too.
Top of wing has been panel lined and have to do a few rivets on an access panel.
Bit of rubbing down on bottom of wing i na small area tonight then will quirt a bit of primer on that sat morning.
Will be pleased when it is all completed.
then back to P47.
cheers
P
some piccies to keep Bob happy
will have to get myself some sort of watt meter, will pick Dave, aka tictec brain on that as he has been flying sparkies for a long time and this is my first venture into the dark side, odd given my professional background!
We had a day off here in brisbane for ekka show holiday, you septcs will need top gogle it, probably equates to your state fair.
anyway got quite a bit done on the mustang, shot some primer, applied a bit more red filler here and there and fitted a new dummy ident light (red) under the wing. Started doing the repairs to the cowl area too.
Top of wing has been panel lined and have to do a few rivets on an access panel.
Bit of rubbing down on bottom of wing i na small area tonight then will quirt a bit of primer on that sat morning.
Will be pleased when it is all completed.
then back to P47.
cheers
P
some piccies to keep Bob happy
Last edited by Peter_OZ; 08-13-2014 at 02:21 PM.
08-14-2014, 02:39 AM
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Sorry I didn't make it yesterday, we were down the coast to get my tax done (for the last two years
) and then out for lunch/diner with friend so it went a lot longer than I had thought it would.Shell is out nearly all of Saturday and it's going to be crap weather wise so that might be a go?? It would be much easier if you bring it here were I have all the equip and options
, but I can head down to your otherwise. Just text me your details cos i can't keep up with were your living these daysYou can have a gander at my latest hawk if you pop round.... Haven't decided if i'm going to use an electron or kero hairdryer for this one yet!
Thanks
dave
P.S. the grey/black 100 series hawk is my current 90mm EDF flyer..
Last edited by ticketec; 08-14-2014 at 02:46 AM.
08-14-2014, 01:53 PM
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hey maaate,
all good and yes I know you were born with a battery pack as a dummy to suck!
Have to head out to minderville to get my tax done too, hop I get a nice one back.
I still dont have the EC5 connectors and nothing is done to the vampire yet, it is just sitting in the box. Come over for a sticky nose if you want. You need to see the new workshop anyway. I'll text you the addy.
go the kero burner mate!! Electrons don't smell nearly as nice as Jet A-1
Nice hawks mate.
cheers
me
all good and yes I know you were born with a battery pack as a dummy to suck!
Have to head out to minderville to get my tax done too, hop I get a nice one back.
I still dont have the EC5 connectors and nothing is done to the vampire yet, it is just sitting in the box. Come over for a sticky nose if you want. You need to see the new workshop anyway. I'll text you the addy.
go the kero burner mate!! Electrons don't smell nearly as nice as Jet A-1
Nice hawks mate.
cheers
me
08-17-2014, 02:09 PM
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no progress on anything last weekend. Spent most of it snoozing on couch as I have not been that well.
No flying as it was windy.
Hope to do a few things tonight after work.
No flying as it was windy.
Hope to do a few things tonight after work.
08-18-2014, 03:01 PM
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nothing to report, it is blowing a gale here and was cold alst night so by time I got home from work, bought some groceries the couch and TV won out.
Have lodged a couple of disputes over the HK vampire I purchased from them. Seriously not sure why I even thought it would be a good purchase.
Have lodged a couple of disputes over the HK vampire I purchased from them. Seriously not sure why I even thought it would be a good purchase.
08-18-2014, 03:28 PM
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Hi Pete
Hope you are feeling better.
Our weather has turned for the best a bit windy up to bout 10mph will try to get out on next day off. battery for my portable air pump went belly up so having to waight for a pay day. The HK thingy has been all over RCU with problems if product had to be shipped from China but if from the warehouse hear in the states some good result's, Do to the stories I will never give them my money as I only buy from proven shops and suppliers.
Cheers Bob T
Hope you are feeling better.
Our weather has turned for the best a bit windy up to bout 10mph will try to get out on next day off. battery for my portable air pump went belly up so having to waight for a pay day. The HK thingy has been all over RCU with problems if product had to be shipped from China but if from the warehouse hear in the states some good result's, Do to the stories I will never give them my money as I only buy from proven shops and suppliers.
Cheers Bob T
08-18-2014, 05:29 PM
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well hope the wind settles for you mate or have you been munching on too many onions?? Pffftttttttttttttttttttt
Bloody windy here as well and its a coldish wind at that.
Yeah they have a nice range of things but trying to get support from them is a nightmare. anyway have lodged formal complaint now with Office Of Fair Trading which is our goventment consumer affiars watchdog so that might force them into action. all they have to do is ship me the damn inlet ducts.
Bloody windy here as well and its a coldish wind at that.
Yeah they have a nice range of things but trying to get support from them is a nightmare. anyway have lodged formal complaint now with Office Of Fair Trading which is our goventment consumer affiars watchdog so that might force them into action. all they have to do is ship me the damn inlet ducts.
08-24-2014, 03:25 PM
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Lazy weekend, Sat wet and blustery, Sun grey and came up windy so no flying. Spent all day Sunday watching movies!
Sat though I got some work done on the P51. Wing has had final primer coat applied to the repaired sections, panel lines and reviets done. Just need some fine weather so I can spray the top colour on.
Been doing some repairs to the chin inlet cowl section and epoxied some carbon tape on reverse side of where the screw hold it on. Cracks in it reinforced with a couple of layers of 6oz cloth. Have to lay up the lip section that goes over the curve part just behind the spinner and epoxy it to the bottom cowl section.
Once all of that is done just a few things to glue back into the cockpit and it is done.
P47 then . . .
Sat though I got some work done on the P51. Wing has had final primer coat applied to the repaired sections, panel lines and reviets done. Just need some fine weather so I can spray the top colour on.
Been doing some repairs to the chin inlet cowl section and epoxied some carbon tape on reverse side of where the screw hold it on. Cracks in it reinforced with a couple of layers of 6oz cloth. Have to lay up the lip section that goes over the curve part just behind the spinner and epoxy it to the bottom cowl section.
Once all of that is done just a few things to glue back into the cockpit and it is done.
P47 then . . .
