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Old Jan 02, 2013, 07:10 PM
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Im thinking we are gonna try and fly it as is as long as it doesnt break 30lbs. We are going to so a bae line CG check saturday with stuff positioned approx. where it needs to go and see what we get.

I have pretty much made the decision to upgrade it to jetfan 90's on 12s fairly soon.
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Old Jan 02, 2013, 07:12 PM
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St.Catharines, Ontario
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I think that's a great decision.................not only for power, but for sound too. two of those on four packs and you should CG out pretty good.
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Old Jan 02, 2013, 07:14 PM
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A turbine version of this would sound really amazing, now if i only had about $4800 for a pair of wren 44's. lol

The way this thing is designed and constructed, you could use one set of outer wing panels and use them on two different center sections.. One EDF and another turbine
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Old Jan 02, 2013, 07:18 PM
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true enough, that would be pretty cool. you could demo it at meets as both. you'd probably sell a ton based on that alone.
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Old Jan 03, 2013, 09:46 PM
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The model is looking real good guys I predict that it will be a very good flyer. Don't worry too much about the thrust angle, I can vouch for the design flying well built per the plans. Yes, you will still need exhaust extensions, unless you have a strong desire to end your maiden flight with a pile of broken wood and fiberglass. (note the sarcasm)
As for the "excess energy consumption" mentioned in post #381, I have not noticed that. My 82" model flies just fine at about 1/4 throttle, and flight times are 15 minutes easily with throttle managment. Bear in mind most EDF power systems, in general, do tend to drain the capacity of the batteries more quickly than propeller driven systems.

Mark
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Old Jan 03, 2013, 10:58 PM
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well, really depends on watts, that thrust setup is probably leaving a little on the table with the wheel drag, and that nose gear doin that funky thing that its doing isnt helping the reading. beeing a really clean design, it will probably fly fine on that power setup, just wont have alot of vertical power. it would be safer to have more power, but i dont think youll 100% need it. might just have a long takeoff run. though, if you look at my 1/4 scale T-38 flying on 2 jetfan 90's (12s setups) it weighed about 44 lbs, and had about 20 lbs installed thrust, and was off the ground in less than 300 ft. the drag of that model is pretty intense, so it didnt have much speed. but a clean model like yours might do just fine on that power, so long as you wernt planning any loops lol.

its looking really good though guys! a nice scale nose strut would really set the model off on the ground. really neat subject, beeing a northrop employee, im a wing fan, and ive always wanted to do a yb49 and a B-2. especially having worked on the B-2.
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Old Jan 03, 2013, 11:00 PM
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Yea i think with some proper energy management and flying the airplane "scale" the 6S setups should be alright. I'm figuring we are around 1800-1900w combined and Maybe 2000w fresh off the charger, not having a watt meter doesn't help any..
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Old Jan 04, 2013, 12:45 AM
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I'd love to see a B-2 by you and your dad Brent. I guarantee it would be more scale than anyone's ever done before. LOL.
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Old Jan 04, 2013, 08:52 AM
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Corsairnut,

Pardon my question, did you say you flew an EDF T-38 in scale fashion with an 8:18 thrust to weight ratio?
That is impressive to say the least. The formula I evolved back in the 80's was 1.623# of airframe :1# of
thrust for scale flight performance. Note scale flight performance is an element of turn and bank angles...
not speed.

Impressive sir! Considering the T-38 is probably the worst case airframe to sustain flight on the aerodynamics
of the airframe... Imagine a porpoise with an EDF.

After the completion of our B-47's I am doing a Vulcan.

Thomas,

Your Flite-Metal "stainless" sections look good. Flite-Metal is more porus then typical laminates and accepts
stains and tints from tea to Rite dye to replicate whatever your documentation shows.
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Old Jan 04, 2013, 06:59 PM
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You only have 2000 watts total? I fly my little 7 lbs MIG-15 on 2500 watts. Sure you don't have 2000 watts per side? If you are serious about electric flight you need a watt meter or a DC clamp amp meter or both.
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Old Jan 04, 2013, 07:00 PM
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Its about 2000 per fan unit
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Old Jan 04, 2013, 09:17 PM
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Thomas,

I recommend you crank up your amps as that will assure clean cycles with plenty of
reserve considering you do not know how much preload the incidence is going to be.

It could be severe enough to take you down rather rapidly, compared to a more clean
configuration where the plane is simply penetrating and not in constant state of shovel.
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Old Jan 05, 2013, 09:29 PM
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Not a whole lot of gettin stuff done today, I think Tom and I both are starting to get the burn-out setting in. My work trip will be nice just to kind of get away for 2 weeks and get my mind clear of some things (not to mention make some money!).

Anyways, We replaced the wire nose strut for a 3/8" diameter offset Robo-strut. This fixed the lame duck nose gear, but with all the weight needed to get this thing to balance, its fully compressed. The plus, is we still have a bit of a positive AoA, so we are going with this setup for the initial flights. No pictures though.

We also did another CG check. We put everything in its respective positions and balanced it at the CG point (around 19" from the nose). We ended up with: two- 6s5000 lipo's, four- 4s4000 Lipo's, one- 3s2300, one-2s2300 A123, a 4cell 1500mah nicad, a 4cell 3300mah nimh, and a 9 channel Receiver. This is what it took to to get it to roughly the correct CG.. The total weight of all this stuff.. 31.XX pounds. So I suspect the flying weight to be 32-33lbs when all is painted and done.

With 4000watts available and 33lbs, that is 121 watts/pound. It may still fly with this ,but we are definitely doing a 12S jetfan 90 setup in the near future.

This also brings up a good point. We made up a CG doohicky (basically some pointed dowels mounted in a 2x4 that the center section can teeter on. The problem is, when you get it close to being balanced at the CG, depending on which end is lower (nose or tail) dictates if it shows as nose or tail heavy. For instance, without changing the position of anything, we can level the center section and it will sit there for a bit. But if when we are leveling it, the nose is slight to low, it will show as nose heavy, and vice versa if the tail is low. This is without moving the position of Anything!

We really need a more reliable and accurate method of balancing this thing! I have a feeling that the Weight on wheels CG method is going to be the only way to accurately and reliably determine the CG within 1/16" accuracy. For those who don't know the W.o.w. method, it involves some measuring and weighting the weight at each axle, its essentially identical to how they balance full-size airplanes and VERY accurate.


So back to the work:
We got the upper strut door linkages built it. It involves some brass straps, 2-56 ball-links, clevis' threaded rod and a modified small control horn. Like I have said before, simplicity is the name of the game for these gear doors.





Then we did the closing and opening mechanism for the inner doors. The doors are pulled close via a piano-wire "lever" that is epoxied and glassed to the inner doors. The wires are visible under the center section when the gear is down, but the fact they are so simple to close and keep closed makes it worthwhile to me! To open the doors, we took some small piano wire and bent a torsion rod style setup. This is bolted the gear door spine and then the bends were modified so the doors would close completely, open completely and so that if one gear went up and closed the door before the other side, the other door would still close. It took about 30-45mins of fiddling with, but worked out great in the end.



And a little youtube video:
1/5.3 Horten HO-229 (6 min 31 sec)
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Old Jan 06, 2013, 01:11 AM
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Stonewall, MB, Can
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I did a 10' flying wing at 85 watts per pound and it flew great at 1/2 throttle. The hardest part was taking off from grass - that needed all the power I could muster. I don't think the comparisons to normal fuselage airplanes are entirely accurate with an efficient design like this.

I think your power will be very sufficient.
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Old Jan 06, 2013, 04:35 AM
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Colchester UK
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Hi Thomas

I have had the same problem you have had for checking the CG of large and heavy models. I first mark the wing root centre line, then mark the range of CG positions and draw it on the rib marked clearly. Then I make a thin plate that I can sandwich between the centre section and the wings. The plate I have made in a variety of materials depending on the weight of the plane. On the Arado I used thin steel sheet, on the Horten I used thin ply. The plate was secured by the wing tube joiner and the anti rotation pin. Its weight is insignificant in relation to the weight of the model. The Arado came out at over 31 KG. The Boulton Paul at 20.9Kg and the Horten at 19 Kg.

The positions of the CG range are transferred to the plate and holes drilled for the range. I made some simple hangars to fit round a spare piece of wood and managed to lift the Arado on my own. It is accurate and simple.

John
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