Radjet 800 from HobbykingName: Radjet 800
Sold by: Hobbyking Manufacturer: Air Fly Limited Category: Speedmodels Material: Epo Wingspan: 800mm Length: 590mm Weight: 430 - 600gr. Price: 35 - 60€ Link to the shop: Radjet 800 Kit With the original setup the Radjet is a funny model that goes around 100km/h aimed at the advanced beginner and everyone else who likes that. Nevertheless its a foam model, it flies like on rails and very precise. It's a powered model but to my surprise it also sails very good. When you program the ESC, you should take care that the engine brake is on, because of that the sailing characteristics improve a lot and the chance that the prop brakes during a landing will be reduced. As tuned version he gets an absolute professional toy. Speeds around 200km/h up to +250km/h and setups with 6S bring up the problem of a very bad visibility (80cm wingspan became smaller quite fast) and a higher landing speed caused by the higher weight. Beside the reflexes you need to have to pilot such a fast, small model.
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Shipping:
Everything is packed quite good and very well protected for shipping, there should be no damages. I decided to buy the kit version because the original engine would have been too weak for me, so I was able to put in my own components without any problems.
My setup:
I'm already comfortable with speed models so I wanted to have a very fast Radjet for in-between. That's why I have chossen the following components:
Engine: NTM Prop Drive 28-36-3000kV 755W
ESC: Hobbyking 60A ESC with 4A UBEC
Servos: Corona MG939 Digital
Battery for 3S: Turnigy 2200mAh 3S 25C
Battery for 4S: Zippy Compact 1600mAh 4S 35C (+10 gr.)
Prop: TGS Sport 4,75x4,75
Receiver: OrangeRx R615
Engine: NTM Prop Drive 28-36-3000kV 755W
ESC: Hobbyking 60A ESC with 4A UBEC
Servos: Corona MG939 Digital
Battery for 3S: Turnigy 2200mAh 3S 25C
Battery for 4S: Zippy Compact 1600mAh 4S 35C (+10 gr.)
Prop: TGS Sport 4,75x4,75
Receiver: OrangeRx R615
Build up:
The first step is to realse the rudders. The sticker is here speperated only with one cut and looks good, but if you move the rudder you will realize that the sticker will stick together each other and block the rudder. I don't need to say what problems this would cause during flight. At first you could think that it would be enough to push the sticker in the rudder gap, but this lasts only for 24h, after that, the sticker will come loose again. Only solution so far: Cutting the sticker along the phase of the rudder, this doesn't look the best, but it works and is safe.
The second important thing is, to put sticky tape on all leading edges. The design stickers look really good, but the doesn't stick that good, especially on the roundings. It would also be quite bad if one of these would become loose during flight.
I decided to glue everything with UHU-PU Max because I think it will be the best. Please don't use Epoxy or something similar, Epo is always moving a little bit during flight and the harder the glue is, the easier it can break. Some colleagues already have this experience, it looks like verything is holding very good but only until the first turn. Then the wing removes from the fuselage and the rest you know...
If using the Radjet with the original setup, there is no reason to strengthen something in any way, it will be fine. I want to put 900 watts inside, so I decided to put in a 0,5mmx3mm carbon strut. The work for this is not as big, you only have to push it trought the fuselage and cut a line in the wing where it will be put in. A positive effect of that is, that you don't need to fix the wing during glueing, the strut will do that for you.
If using the Radjet with the original setup, there is no reason to strengthen something in any way, it will be fine. I want to put 900 watts inside, so I decided to put in a 0,5mmx3mm carbon strut. The work for this is not as big, you only have to push it trought the fuselage and cut a line in the wing where it will be put in. A positive effect of that is, that you don't need to fix the wing during glueing, the strut will do that for you.
The engine mounting looks a little bit strange at first sight, but if you take a second look, you will recognize that it is done not that bad and you can use it without any bad feeling.
Finishing everything else should not be a problem for everyone who has ever built a model, I only did some small modifications for my strong setup. I decided to not glue the turtle deck (the cover on the upper side) down, sticky tape is enough and you can get to the components lader if needed. On the pictures you can see where to put the components to reach the correct CG without useing much extra weight.
Flight characteristics:
The Radjet is an easy to fly model that don't brings any big surprises, but there are three things you should consider:
The CG in the instructions is totaly wrong, a CG of 400mm from the nose seems to be the best.
The CG in the instructions is totaly wrong, a CG of 400mm from the nose seems to be the best.
Take-off can be a little bit tricky, depending on your engine and prop he needs more throttle then you would maybe think. If I fly with 3S he needs at least 3/4 throttle, if flying with 4S then 1/2 throttle. If you use too less throttle, he sags down to earth faster then he can accelerate. The result looks like this:
Finaly the third thing you should take care is the death spiral. If the Radjet gets a stall, he immediately starts to spin and won't get out of it. The rudder won't have anymore effects, you only can reduce the spinning a little bit. That's where it first time happend to me:
You only have one chance to get out of this deatch spiral: Rudder to neutral and full throttle. If the Radjet has enough thrust, he will go straight out from spinning in the direction he pointed at that moment. However, while spinning nd with this "trick" he looses lots of height, so you should not do that for fun.
Beside that things, the Radjet really flys superb. I was impressed how exact and like on rails he is flying. As usual with a delta you will need less expo on the elevator and more on the ailerons. Also the aileron differential needs to be tested on your own. The whole plane is built quite stable and beside the carbon strut 250km/h can be achieved without problems.
Oh, 250km/h, so we got to his propose...
The Radjet flys with the 3S after a downturn 200km/h and with 4S just not 250km/h. Should be eough for a 80cm wingspan. With 4S it is a challenge to control him fast enough, but landing is still very stressless.
With 3S the battery lasts with full throttle something about 3:30, with 4S it goes down to 1:25. The current is on 3S around 36A, but with 4S it will go up to 60A.
With 3S the Radjet is a fun machine that can be always with you, but with 4S he transforms to a hell raising thing that needs 110% concentration. You also should not fly permanently with 4S, the engine, the ESC and als the battery will be very hot after 1:25 and will not do that for over 100 flights...
Addition Jannuary 2014:
I did it! I got the Radjet over 250km/h!
Equipped with a 4S battery and an APC 5x5 he was able to do 252,7km/h out of a downturn. This is the average value out of some meassurements.
I also need to advise you to not do that on your own, the battery and also the ESC are definitely on their absolute limits and even after the landing they are very hot, also the battery lasts only for less then a minute.
Beside that, here is a Video with the 4,75² where you can see how fast the 4S version is going, the speed was meassured with the doppler effect:
Beside that things, the Radjet really flys superb. I was impressed how exact and like on rails he is flying. As usual with a delta you will need less expo on the elevator and more on the ailerons. Also the aileron differential needs to be tested on your own. The whole plane is built quite stable and beside the carbon strut 250km/h can be achieved without problems.
Oh, 250km/h, so we got to his propose...
The Radjet flys with the 3S after a downturn 200km/h and with 4S just not 250km/h. Should be eough for a 80cm wingspan. With 4S it is a challenge to control him fast enough, but landing is still very stressless.
With 3S the battery lasts with full throttle something about 3:30, with 4S it goes down to 1:25. The current is on 3S around 36A, but with 4S it will go up to 60A.
With 3S the Radjet is a fun machine that can be always with you, but with 4S he transforms to a hell raising thing that needs 110% concentration. You also should not fly permanently with 4S, the engine, the ESC and als the battery will be very hot after 1:25 and will not do that for over 100 flights...
Addition Jannuary 2014:
I did it! I got the Radjet over 250km/h!
Equipped with a 4S battery and an APC 5x5 he was able to do 252,7km/h out of a downturn. This is the average value out of some meassurements.
I also need to advise you to not do that on your own, the battery and also the ESC are definitely on their absolute limits and even after the landing they are very hot, also the battery lasts only for less then a minute.
Beside that, here is a Video with the 4,75² where you can see how fast the 4S version is going, the speed was meassured with the doppler effect:
Conclusion:
Target group: Advanced pilots and speedjunkies
Finishing: Easy
Flight characteristics: Good
Price / performance ratio: Perfect
Definitely a recommendation to buy, nowhere else you will get more speed and fun for less money!
Finishing: Easy
Flight characteristics: Good
Price / performance ratio: Perfect
Definitely a recommendation to buy, nowhere else you will get more speed and fun for less money!