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Pumpkin drop event

300% FT Viggen for FliteFest 2015!!!

#1
Let me start off by saying that I always have to be building something. :D

This time it will be a 300% (not 150%.....not 200%.....but 300%) FT Viggen. I figured since I have a 100% Viggen and David's original MiniViggen (45%), it's time to build a MonsterViggen (just came up with that name). :D

The MonsterViggen will be about 9.5ft in length (that's almost two of me! yes I am short) and close to 7ft wingspan. The airframe will cost around $30 which includes 23 sheets of FliteTest/DTF foam and wood spars. It will be an EDP (electric ducted prop), which means that it will use a normal motor and propeller, but all contained inside of a duct similar to an EDF. Using an EDF at this size would be too pricey for me. I am planning to use a 3s 2200-3200mah lipo to power an NTM 35-36A 1400kv motor swinging a 8x6 or 8x8 APC prop. The 8" prop is due to the size limitation of the EDP duct; using an 8" prop will result in less than 1/2" of clearance inside the fuselage/duct.

While the name "MonsterViggen" may sound intimidating, it will actually/unfortunately not be a very fast plane at all. At first, I planned to make the airframe around 8lbs, but it was difficult (I won't say impossible, but it's pretty close) to find a motor that could produce 8lbs+ of thrust (or even half that) while only using an 8" prop. Therefore the goal became to make it as light as possible. From some rough calculations I have concluded that the (lightened version) airframe alone will weigh around 3.5lbs, so a motor that could produce 2.5lbs of thrust should at least get it in the air.

From that I can estimate the AUW including the battery to be around 4 to 4.5lbs, and with a wing area of approximately 3000 inches sq, the wing loading should be just shy of 3.5 oz/sq ft. This will make for a very slow plane, but it should still be pretty fun. :)

By the way, a canard on the MonsterViggen will be bigger than a wing on a normal sized Viggen. :eek:;)

I hope to either finish this for FliteFest 2015 or finish it at the event - let me know what you guys think about that. Any other ideas or suggestions would be welcomed as well! :)
 
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willsonman

Builder Extraordinare
Mentor
#6
You know I have the 1800Kv NTM motor and it puts out crazy power on 4S with an 8x6 prop. You may want to consider that. Also, I'm concerned that the inefficiency of the 2-blade prop inside of a duct. I would be more inclined to make it a pusher for better chance of success. Looks to be a fun project. I'll be watching for sure!
 

wilmracer

I build things that fly (sometimes)
Mentor
#8
You should call it the Biggen :)
I like that!

I've seen a few posts from a guy who did a similar build but at the moment I can't find it. I'm fascinated by the idea of large ducted propeller jets and would be excited to see how this flies.
 
#9
I salute your initiative but think you should reevaluate your power system. You will need a high kv motor if you're going to duct the prop, perhaps even think of using a 3 bladed prop. Look for a 1800-2200kv motor and you'll need at least 200W per pound because of inefficiencies in your home made system. With the size of model you are talking, it could take 2kw of power to fly well.

There are nice pusher Viggens too. It would be easier, and take less power if you just use a 6S or 8S pusher motor.
 

AkimboGlueGuns

Biplane Guy
Mentor
#10
You could always go for a 4-5 bladed prop. You might have to do some digging for one, but a 4-5 blade prop will make a lot more thrust in this application.
 

Aeronaut

Build+Crash= +more power!
#11
I actually am going to be building a 150% 90mm EDF viggen. gonna use a 12 blade fan on 6s. I think I will start to build it during the summer when I don't have to worry about finals.
Are you going to be using Retracts for this build? I happen to have a NTM 35-36A 1400kv motor using a 3s 2200mah 40c battery swinging a 9x6 or 10x6 prop, 55A esc. I have in a normal size ft spitfire. It produces a lot of thrust but not even enough for a 300% viggen. maybe two of them would be enough but i don't see how it would fit.

On RcG there is a big EDP that uses twin 6x5 props, I think its 6ft long depron build. I will find the link for it and post it here if you would like to take a look.

Here is a something similar just not as big: http://www.rcgroups.com/forums/showthread.php?t=2146322
 
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#17
Well I can't seem to quote multiple posts (quote+ button doesn't work or I am doing it wrong). Also sorry for the llate responses; I was out of town for the whole weekend.

@wilsonman: Thanks for the advice, I will consider a 4s setup. I am a little worried about the power as well. The main reason I did not want to make it a pusher is because with the motor all the way in the back, I would need a whole lot of weight in the front to balance it which means it would be heavier so I would need a bigger motor to provide more power which then requires bigger batteries to balance out etc.

@RAM: Thanks for the suggestion. Let's just do a quick poll. Who likes MonsterViggen and who likes Biggen? Or any other name suggestions? I will give credit to the creator of the name.

@wilmracer: I have seen that Mig 1.44 EDP jet (partially what inspired me to try this). It is a pretty cool plane for sure.

@Team_Monkey: True.....thanks for the advice, I will take that into consideration. The most difficult part so far has been trying to find a good motor match. Same problem with pushers as mentioned above but maybe it can be done.....we'll see. As for weight, I'm not sure. If I can make it structurally sound just using a single layer of DTF/FT Foam w/o paper and with carbon/wood reinforcements the airframe w/o electronics will weigh roughly 1500 grams. I might be crazy but I'm going to try anyways. :D (wing will for sure be at least 2 layers DTF with carbon/wood reinforcements, but everything else 1 layer)

@AkimboGlueGuns: Not sure where I would find a 4-5 blade prop.....at that point I might as well just put two motors in there with counter-rotating props (wouldn't be quite 2x the power but it would eliminate torque as well).

@Aeronaut: Yep, thanks for the suggestion about using two of the motors. I may do that. As to how it would fit, I guess I don't really understand the question? I will be using an 8x6 or 8x8 prop (if I end up making it EDP) so it should fit nicely inside of the fuselage. Also good luck on your 150% Viggen!
 
#18
Having built a rather large (10ft) cargo plane out of DTFB, I can tell you that this thing is going to come in quite heavy. The power setup you are describing is probably more appropriate for a 100% Viggen, not the MonsterViggen. I used almost exactly 25 sheets of DTFB, and my power setup is two 1400W motors swinging 18x10 props. It's underpowered.

I'd say at the very least you're looking at using something like this motor, with the appropriate prop on it. You can use eCalc to figure out what prop would be suitable (probably a 8x5). I'd recommend a 6s setup (just put your 3s' in series).
 
#19
Having built a rather large (10ft) cargo plane out of DTFB, I can tell you that this thing is going to come in quite heavy. The power setup you are describing is probably more appropriate for a 100% Viggen, not the MonsterViggen. I used almost exactly 25 sheets of DTFB, and my power setup is two 1400W motors swinging 18x10 props. It's underpowered.

I'd say at the very least you're looking at using something like this motor, with the appropriate prop on it. You can use eCalc to figure out what prop would be suitable (probably a 8x5). I'd recommend a 6s setup (just put your 3s' in series).
Did you use the DTF with the paper on or removed? Did you use hot glue or other type(s) or glue? And I have never seen your cargo plane, but I would imagine most are pretty draggy.....the Viggen also seems like it will be fairly draggy due to the large ducts on the sides and small area for the air to exit in the back. I will think about the 6s, but I think it may be easier for me to just buy two motors to get some more thrust.