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Old Aug 28, 2004, 09:01 PM
Cyberman is offline
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Mad Max meets the Thinker
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Ho XVIII (Horten 18 Amerika Bomber) - Design/Build Thread


I've decided to go with something
  1. Hard to fly
  2. Interesting to build (see fun to build)
  3. Should look great ( if it flies )
  4. Something I like (most important)

My Initial design will be 1/19th scale. The original wing span a 'paltry' 40m, a wing root of 6.5m, sweep angle of 24.3 degrees, and a wing area of 150m^2.

This plane is not small by any means at 1/19th scale
83" wing span or 210cm
644 sq inch area (.415m^2)

The original plane was powered by (six weak) JUMO004b engines with 2000lbs thrust each. Since this is going to be electric and very light wing loading. My choice of fans will be GWS EF40H's, with six it should have adquate power (should). The high voltage motors were choosen to keep current below 20A (it would be more than 30A otherwise) this also keeps my weight down. Current is roughly 15.5A to 18A depending on battery choice etc.

Problems: do these fans need heat sinks? I can't find the GW/EHS-12 heat sink weight anywhere (whine whine). I'll be running them above 12V (to get the power level somewhat closer to the lower voltage fans) nothing is given on motor data. This wise/unwise, or does it really matter? (grin).

Motor controller Castle Creations 25A controller. A UBEC will likely be used not the on board one to the controler (see voltage on the border of too high). This will be run with 12/13 Cells nimh batteries or 2 2S LiPo packs (that can handle the current). At least that's the plan

Since pictures are worth a thousand words though so you have an idea what it looks like (I had to look real hard to find GOOD drawings of this plane), and why I like it:
Last edited by Cyberman; Aug 28, 2004 at 09:08 PM. Reason: Fixing Typo's
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Old Aug 28, 2004, 09:09 PM
spiro is offline
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Strange Planes INC.
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Bravo!

Now this is a project near and dear to my hart. Best wishes, I will be reading closely. Will this be in the design contest?

Spiro
Old Aug 29, 2004, 07:52 AM
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Whats it called?
Old Aug 29, 2004, 11:17 AM
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EDF rules... :)
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Cool, good luck...

Eric B.
Old Aug 29, 2004, 11:27 AM
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I think 12 V is going to cook those little motors http://www.buygws.com/edfperformance.htm

You might be better off buying WeMoTec Microfans (2") and installing some high RPM brushed motors, the GWS fans will be lucky to produce 18oz. of thrust, and I don't know if thats enough to fly a 7 Ft. wing

Best of Luck, I'll be watching with interest

Tom
Old Aug 29, 2004, 12:17 PM
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Quote:
Originally Posted by RCParkflyer
You might be better off buying WeMoTec Microfans (2") and installing some high RPM brushed motors, the GWS fans will be lucky to produce 18oz. of thrust, and I don't know if thats enough to fly a 7 Ft. wing.
18 x 6 = 108 / 16 oz = 6.75 lbs. of thrust. At 30% T/W ratio, this would fly a 20 lb. model. At 50% T/W ration would be a 13.5 lb. model. Very doable, if the thrust figures are accurate.

Also keep in mind that with multies, the total of the thrust is more than the simple sum of it's numbers. This is because of the efficiency mulitple power systems offer.

Daren
Last edited by Daren; Aug 29, 2004 at 12:22 PM.
Old Aug 29, 2004, 12:28 PM
WillowPtarmigan is offline
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Go for it! Interesting airplane. Was the Horten 18 ever used in World War II?
Old Aug 29, 2004, 12:47 PM
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EDF rules... :)
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18 ounces of thrust per GWS EDF 40 man I gotta get one...

Eric B.
Old Aug 29, 2004, 12:59 PM
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You guys kill me LOL

EDF1630x6 2.61 oz. of thrust Per Motor @ 12 V.
Old Aug 29, 2004, 01:51 PM
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The Dogs of War (Horten 18)


Spiro: Yes it's a contest entry
Dogzilla: Horten XVIII, code named 'Amerika Bomber'
RCParkflyer: How so? at 12V you are only putting 25W into them tops EDF40H which is below the EDF40 is where to look. It has higher efficiency and I want to stay on the curve. The EDF40 is pushed to 40 watts and that is likely too cook the motor. However I'm only pushing these to 25 to 30 watts.
WillowPtarmigan: No it was not, they had the steel tube airframe constructed and were begining to make the wood/composite wings for it when the Allies invaded germany. It was scheduled for testing in November of 1945.
AirX: It could be from the use of phlogistom wiring possibly. Yes 18 oz thrust would be.. yeah.. interesting

All: The plane weight is set for 825 to 1200 grams or 29 to 42 oz with 4.4 square feet of wing area that's about 9 1/2 oz per square foot at worst case. As I said a VERY VERY light plane. 6 motors at 30 watts is 180 watts for propulsion. Not a lot but it has about 16 oz or more thrust in total. The thrust tubes are to be scalish (LOL) and I'm planing on 100% FSA all the way. Worse comes to worse I can scale up to 1/16 and use GWS55-300H 5 1/2oz thrust (ea) or ~32oz thrust with 8cells (but running at around 36A) wing area jumps to 6 or more square ft (900 square inches) weight .. who knows (but we are now talking 360w not 150-180W)

Cyb/Stephen
Old Aug 29, 2004, 02:22 PM
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Quote:
Originally Posted by AirX
18 ounces of thrust per GWS EDF 40 man I gotta get one...
Eric B.
Hi Eric

for that sort of thrust level you would need at least 250W - is that feasable?

Klaus
Old Aug 29, 2004, 08:54 PM
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Quote:
Originally Posted by winmodels
Hi Eric

for that sort of thrust level you would need at least 250W - is that feasable?

Klaus
Well best case scenario I can get is probably 200W in 6 fans. Wishful thinking won't make a functional plane so I'm just going to make it extremely light and if I can keep it under 1000 grams (2 1/4 pounds), It should be able to fly though it's not going to be easy. The scaling is a bit difficult to get the fan size too scale thus the FSA is probably a little small however I am not going to worry about it. The first plane seldom flys the way one expects or hopes

Cyb
Old Aug 29, 2004, 09:02 PM
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EDF rules... :)
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I dont think so Klaus, if it were possidble everyone would be using it. The little 40 stock is as Cyberman stated 2-2.5oz thrust @50watts...

Eric B.
Old Aug 30, 2004, 02:24 AM
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Cyb,

Extremely cool, but I'm going to have to look up phlogistom in my Funk & Wagnall. Another neat design to follow. Drive on, and make it kitable. Very cool.

Tim
Old Aug 30, 2004, 01:21 PM
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Quote:
Originally Posted by 777Fan
Cyb,

Extremely cool, but I'm going to have to look up phlogistom in my Funk & Wagnall. Another neat design to follow. Drive on, and make it kitable. Very cool.

Tim
Phlogistom was a mythical element that had negative mass , that scientists had been using to explain how iron was being manufactured. They had not yet discovered oxygen and carbon reactions, so they created/made up phlogistom. It's fun to throw in because now we know this notion is absurd, poor guys then had no way of explaining how iron was being extracted using limestone and coke with iron ore. As Bore hadn't begun his atomic table of elements and they didn't understand chemical bonds and bond strength.

On Subject
My Brain melted my computer had a freak acident and I lost some data (sniff) so I'll get around to posting initial 3 views later in the week instead! The ones on Luft46 are inadquate HOWEVER I did find the attached (and shrunk) which gives part of the Horten 7 design! It's almost identical to the Ho 18, thus it's a good starting basis. It would be nice to have the original drawings personally but beggars can't be choosers.

Cyb


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