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Old Dec 18, 2012, 06:01 PM
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Ummm....once you see how the rest of the vehicle comes together, I dont think you'll have the same opinion.

Adjustments will be looked at as it gets finished....but I doubt I will need to shorten the buckets to maintain the correct aspect relative to the "real" thing....though if need be, it wont be that hard.
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Old Dec 18, 2012, 06:19 PM
Emress
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ahh, true.
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Old Dec 18, 2012, 06:25 PM
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Forgive the ignorance, I haven't played with balsa in 30 years, but will that wing support the bucket/motors/servo combo? Would it not be stronger starting with an alum. tube and then shrouding it for appearance and rigidity?
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Old Dec 18, 2012, 08:26 PM
cant get right !!!
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Quote:
Originally Posted by Granted View Post
Forgive the ignorance, I haven't played with balsa in 30 years, but will that wing support the bucket/motors/servo combo? Would it not be stronger starting with an alum. tube and then shrouding it for appearance and rigidity?
+1 i thought the same thing
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Old Dec 19, 2012, 07:22 PM
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Only the outer framework is balsa for the shape. Trying to shape a complicated structure like a wing out of aluminium would be way too difficult, costly, and heavy. But, I have already started reinforcing the interior of the "wings" with dense hard wood and aluminum tubing. Additionally, each wing half will be fiberglassed with two layers. The first will be 5oz cloth for stiffness and the 2nd will be 2oz cloth using finishing resin.

On top off all that, there will be support beams cantilevered from the bottom area of the fuselage to about the center of each wing half. These will be hidden by the details such as mounted "plasma cannons" etc.
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Old Dec 24, 2012, 07:12 AM
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Ran some calculations for watts vs pounds.
What Im coming up with is suggesting the 3 fan design Ive got along with the motors Im running is enough to fly the vehicle without issue even if the caft weighted 27 pounds................

HOWEVER.......that would be for a vehicle that is using wings for lift.
The base needs for most edf style power systems is 200 watts per pound, however, with a v-tol type craft that is entirely based on thrust to stay aloft.....1.5 times that should be required.

So now at 350 watts per pound, with a total 3 fan design using the rimfire .60's rated at 2200 watts burst(1700 watts constant).
So at 1700x3 gives me 5100 watts ouput total available. 5100/350 = 14.5 pounds.

14.5 pounds may seem like a lot of weight, but given the size of the vehicle, I'm concerned I may get real close to that or possibly over once everything is finished and all the goodies(lights, camera...scale exterior shape, etc).

As a result, Im adding two additional fan units instead of the previously mentioned one(both aresomewhat smaller 9" diameter size) that will be unseen "inside" the main fuse area under that louvered location pictured a few posts back.

Adding them obviously will add more weight, but not as much as the thrust they will provide. They are turnigy sk 4250-650 kv motors. Same kv as the larger rimfire 5055-650s in the main fan units...so the smaller units will use the same pitch but smaller diameter props...ie 9x7x3

Both of these motor setups are rated for 1150 watts each. So now total watt output is 7400. This gives me a maximum vehicle weight of 21.1 pounds.
I can reasonably expect the total weight to be less then that.....would still be nice to be able to keep to around 15 pounds though, but I'll settle for 17-18 pounds.

Hopefully, I can get a pic of the additonal two fan units mounted on the main fuse forward section soon.
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Old Dec 24, 2012, 07:28 AM
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Yeap, I also ended up having to go with larger motors and props. I will have to redesigned the ducts to accommodate the larger props. The Good news is, the larger props should make it a tad more efficient.
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Old Dec 24, 2012, 05:35 PM
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My limiting factor is the bucket size for the main fan units. Thats what drove the motor choice based on what size prop I could fit in it. So I cant goany bigger then the 11x7x3 prop setups already mounted up.

If for some ungodly reason that three times 11x7x3 motor/prop combos and two time 9x7x3 motor/prop combos can fly this thing, then holy crap

In that event, Id have to add in some 90mm edf units in the wing. But...id then have to account for more battery capacity as Ive already got 5 outrunners running off a pair of 6s 8000mah packs.

I think i'll be fine though...hopefully overkill on the thrust as it stands.
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Old Dec 24, 2012, 05:39 PM
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I thought you were considering using dual motors and props in each duct?
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Old Dec 26, 2012, 09:20 PM
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I was, but I think ill gain more actual lift from the two smaller fans in there own smaller buckets then I would mounting the motors as 2ndary units in the main fan housings.
I can still add a second set of motors/props in the main ducts if I still lack for adequate thrust. I doubt that will be necessary though.
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Old Dec 26, 2012, 09:43 PM
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Yea, I believe you are right. Paid a Visit to Home depot today and they had some 12" concrete forums but I did not buy it, the buckets like you presently have is 11.5-11.75", I learned how to weld plastic a while back and may use one of them adding a small segment to increase the diameter. Not sure just what I will do yet.
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Old Dec 26, 2012, 10:14 PM
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I actually made a mistake in my calculations. 1.5 times 200 watts is 300, not 350...thats what i get for posting tired.. But that's ok.....gives me a bit of overhead. At 300 watts per pound...I can get up to 25 pounds
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Old Dec 27, 2012, 08:51 PM
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Have a look at this thread: http://www.rcgroups.com/forums/showthread.php?t=1790142

Duals may not be such a bad idea with some refinements.
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Old Dec 28, 2012, 03:22 PM
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Subscribed! Good luck with it
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Old Dec 28, 2012, 04:04 PM
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Quote:
Originally Posted by rimshotcopter View Post
Have a look at this thread: http://www.rcgroups.com/forums/showthread.php?t=1790142

Duals may not be such a bad idea with some refinements.
Maybe.....but as I've already accomodated the frame structure to accept the two additional fan units hidden within the main body, I will stick with that route and only add dual motor/props in the main fan units if absolutely necessary.

So right now....I have 5 motors powering this beast with only 3 of them being seen outwardly.
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