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Old Mar 13, 2011, 09:02 PM
Ming's Avatar
Hong Kong
Joined Jun 2002
4,659 Posts
BEN

Please make sure the 30A ESC is OK for your masterpiece.
Kind remind that 3S battery draw 30.5A and 4S draw 35.5A.
I don't suggest to use less than 35A ESC for stock Scorpion HKII2221-8 motor.

Ming Lou
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Old Mar 13, 2011, 09:13 PM
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Rookie2008's Avatar
Southern California
Joined Mar 2010
912 Posts
Ming any Info on when I can expect the 2 wooden plates, Decals, and extensions? I am anxious I want to finished the plane.
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Old Mar 14, 2011, 02:09 AM
*** gravity sucks ***
Fotor's Avatar
Netherlands
Joined Mar 2007
400 Posts
Ben, nice job!
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Old Mar 14, 2011, 03:38 AM
Go FASST or go home...
Ben_E's Avatar
Bergen, Norway
Joined Nov 2002
3,149 Posts
Thanks guys!

Quote:
Originally Posted by Doug W View Post
Ben,

Fantastic job- it looks the part! Remind me- did you 2mil vinyl cover the aircraft or sand and paint?
Well.... both. Not a good idea though, too much weight added. I sanded and painted and covered with vinyl...


Quote:
Originally Posted by Ming View Post
BEN

Please make sure the 30A ESC is OK for your masterpiece.
Kind remind that 3S battery draw 30.5A and 4S draw 35.5A.
I don't suggest to use less than 35A ESC for stock Scorpion HKII2221-8 motor.

Ming Lou
The motors draws 45A with the Change Sun fan on 4S. I have 2 60A Escīs

Ben_E
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Old Mar 14, 2011, 07:47 AM
Go FASST or go home...
Ben_E's Avatar
Bergen, Norway
Joined Nov 2002
3,149 Posts
Ming!

You stated earlier that a flying weight of about 3 kilos is fine.

But how is that possible?

On a conservative side I made up this list (this is not my plane but a guesstimate of total flying weight, done as light as possible
  • Foam kit ex motors 1957g
  • Motors 2x81 grams 162g
  • Escs approx. 100g
  • Servos and cable 150g
  • Power cables 200g
  • 4s battery 4000mAh 950g
  • Paint and decals 200g
Total of 3719g

On some of the airliners in one of the videos one of them has 4S 10.000mAh onboard What is their flying weight?

Ben_E
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Last edited by Ben_E; Mar 14, 2011 at 07:56 AM.
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Old Mar 14, 2011, 10:15 AM
Ugly planes do not fly
_Sergey_'s Avatar
USA, GA, Alpharetta
Joined Mar 2007
1,689 Posts
Ben, this is outstanding job you've done! Congratulations! We'll be monitoring the site you provided to watch your maiden
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Old Mar 14, 2011, 10:25 AM
Ugly planes do not fly
_Sergey_'s Avatar
USA, GA, Alpharetta
Joined Mar 2007
1,689 Posts
Flap question

Quote:
Originally Posted by Doug W View Post
Thought I'd show some progress on my working wing...the only question now is slats. Hmmm.

For the flaps, I still need to mount the offset hinges so the flaps travel properly, but I daringly (and carefully) cut into Ming's beautiful wing to create flaps, without sacrificing main landing gear mount integrity. And, just for fun, I had to add spoilers too (which will be ground deployable on landing on Aux 2).

Cutting that wing is not for the faint of heart for sure...talk about measure twice and cut once.
Wow! Doug, this is very nice looking flaps! I am about to put my knife into the wings. Can you please share more details?

* How did you manage avoiding landing gear mount?
* What is the servo placement for the flaps? Is there one servo or two servos per wing? What is the actuation looks like (push rods etc)
* What is the cutting procedure?

It would be a tremendous value to see underside of the wing too.

Thank you for sharing Doug! You are the master of the high lift devices
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Old Mar 14, 2011, 10:28 AM
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Rookie2008's Avatar
Southern California
Joined Mar 2010
912 Posts
Ben, I have to say you have the Finest 737 foam plane I have seen . I love the livery. I will be looking forward to you maiden.
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Last edited by Rookie2008; Mar 14, 2011 at 10:38 AM.
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Old Mar 14, 2011, 10:31 AM
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SilentHunter's Avatar
United States, Death Valley
Joined Aug 2003
3,113 Posts
Whats the big worry about the weight? I bet this thing would be fine up to 8 or 9 pounds at least.
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Old Mar 14, 2011, 11:21 AM
Go FASST or go home...
Ben_E's Avatar
Bergen, Norway
Joined Nov 2002
3,149 Posts
Thanks guys! Really appreciate it


Quote:
Originally Posted by SilentHunter View Post
Whats the big worry about the weight? I bet this thing would be fine up to 8 or 9 pounds at least.
I hope you are right, I do think Iīm in that kind of numbers That is why I Asked Ming about the weight of the 737īs already flying...

Does anyone have some test data on the Change Sun fans? Link somwhere?
I have been searching but canīt find any...

Ben_E
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Old Mar 14, 2011, 11:58 AM
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Doug W's Avatar
United States, WA, Seattle
Joined Jul 2010
480 Posts
Quote:
Originally Posted by _Sergey_ View Post
Wow! Doug, this is very nice looking flaps! I am about to put my knife into the wings. Can you please share more details?

* How did you manage avoiding landing gear mount?
* What is the servo placement for the flaps? Is there one servo or two servos per wing? What is the actuation looks like (push rods etc)
* What is the cutting procedure?

It would be a tremendous value to see underside of the wing too.

Thank you for sharing Doug! You are the master of the high lift devices
I'll snap some pictures, notably of the underside and post them tonight. The inboard flap (near the gear) was very difficult to cut. I haven't mounted servos yet, but I will show where the locations will be. I should have servo mountings done (including the spoliers) by Friday (assuming my servos I ordered show up in time). There will be two flap servos per wing (inboard and outboard flaps) both on 6 second delay speeds, and the flaps hinges will be offset, buried in the canoes (which I hollowed out) In short, they will work exactly like the real ones.

Spoilers are held down by tiny springs in flight, and the servo that will actuate them (on Aux 2) will actually not be connected in any way by pushrod or otherwise. It will be evident when I get the pics done.

I'll post a couple pictures of my test bed aircraft to show the offset hinges, and spoiler springs I am referring to. In the 737, the only items visible will be the flap servos. Everything else is hidden neatly within the wing and canoe fairings.
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Old Mar 14, 2011, 12:07 PM
Ugly planes do not fly
_Sergey_'s Avatar
USA, GA, Alpharetta
Joined Mar 2007
1,689 Posts
Thank you Doug! Can't wait to see pictures with more details!

I think I got the spoiler and spring idea. Is it possible during the flight, air coming from down the wing above the flap will raise the spoiler? In other words do you need to lock spoilers down with more than a spring during the flight when flaps are deployed?
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Old Mar 14, 2011, 12:19 PM
Ugly planes do not fly
_Sergey_'s Avatar
USA, GA, Alpharetta
Joined Mar 2007
1,689 Posts
Quote:
Originally Posted by SilentHunter View Post
Whats the big worry about the weight? I bet this thing would be fine up to 8 or 9 pounds at least.
Stall speed, V = sqrt(W x 9.81/(1/2p x S x Cl_max)

where:
W - weight
p (rho) = air density KG/M^3
S = wing area M^2
Cl_max = Coefficient of lift at stall

Or to simplify stall speed is proportional to the square root of weight.

For example, let say when plane weights 2kg it's stall speed is 40km/h
at 3kg stall speed is 48km/h
at 4kg stall speed is 56km/h


Which means if you want to fly your plane scale (slow) weigh needs to be kept down.
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Old Mar 14, 2011, 12:31 PM
*** gravity sucks ***
Fotor's Avatar
Netherlands
Joined Mar 2007
400 Posts
BenE, what is your total weight?
Ming calculated with (I think) 3S2600, that saves quite a bit of weight. And 200 grams for power cables, isn't that a bit much?
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Old Mar 14, 2011, 12:54 PM
Go FASST or go home...
Ben_E's Avatar
Bergen, Norway
Joined Nov 2002
3,149 Posts
Quote:
Originally Posted by Fotor View Post
Ming calculated with (I think) 3S2600, that saves quite a bit of weight. And 200 grams for power cables, isn't that a bit much?
Ming recommended 2x 3s 3300mAh

My big question is the weight of the airliners we already have seen in the videos. One of them had 4s 10000mAh onboard, the other 3s 10000mAh. Even if my suggested weights might be bit off, I really can't understand how one should get down to the recommend AUW on 3 kg.


Quote:
Originally Posted by Fotor View Post
BenE, what is your total weight?
I'm at just above 4kg...

Ben_E
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