Wattflyer RC Network: RC Universe :: RCU Magazine :: RCU Forums :: RCU Classifieds :: RCU User Reviews :: RCU YouTube
Home Who's Online Calendar Today's Posts RealTime Post Spy Mark Forums Read
Go Back   WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > Scale E-Powered Aircraft
Register Members List Wattflyer Extras Articles Search Today's Posts Mark Forums Read Social Groups

Scale E-Powered Aircraft Discuss electric powered scale models here.

Thank you for your support (hide ads)
Reply
 
Thread Tools Display Modes
Old 01-17-2014, 12:49 AM   #1
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default Semi-scale B-25

Ever since my wonderful wife arranged for me to fly in a B-25 last summer (this one: http://www.champaignaviationmuseum.org/#!b25/cgmb ), I've been vaguely thinking about building a model of the plane.

Today I've started thinking about it in more detail, and started on drawing up some plans. This will be my first twin engine model, so I'm not planning on getting overly involved in scale looks, but rather just going for a basic flyer, to learn the ins and outs of doing a twin. So the fuselage and engine pods are going to be squared off foamcore structures - sort of a 3 dimension "profile" thing .

I found some 3-view drawings somewhere on line and established a scale conversion factor to lay out the plans. It's going to have a 42" wingspan and about 32" over-all length.

More as things progress!

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 01-17-2014, 02:05 AM   #2
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,171
Thanked 216 Times in 207 Posts
iTrader: (0)
Friends: (1)
Default

Slight downthrust and outboard thrust both sides even with counter-rotating props.

And don't count on electric preventing single-engine-out. I've seen planes throw the prop hubs and other strange things which electrics are not immune to.
fhhuber is offline  
  Reply With Quote
Old 01-18-2014, 12:15 AM   #3
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

OK, off we go



Got the wing halves cut. The plan is to glue in top & bottom spars, then cut the angles (the B-25 has a gull-wing - dihedral in the center, flat beyond the engine pods).

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 01-19-2014, 12:22 AM   #4
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

And here are the four wing sections, with spars glued in and the angles cut:



And here's the whole thing glued up:




Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 01-19-2014, 08:09 PM   #5
baz49exe
Super Contributor
 
baz49exe's Avatar
 
Join Date: Jun 2008
Location: Devon. England
Posts: 1,101
View baz49exe's Gallery15
Thanked 135 Times in 130 Posts
Club: East Devon Radio Control Club
Awards Showcase

Outstanding Contributor Award  Scratchbuilders Award 
iTrader: (0)
Friends: (15)
Default

Looking good:- can't wait to see this model develop!

Baz
baz49exe is offline  
  Reply With Quote
Old 01-19-2014, 11:18 PM   #6
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

Thanks!

Nothing to show today, but I did put a coat of primer on the wing and ordered motors & speed controllers. I'm going with two of these: http://www.headsuphobby.com/Emax-CF2...otor-H-445.htm with 5 x 3 three blade props. That ought to do it (I hope) and the 3 blade props will look good . I got both left and right hand rotation props.

I'm anticipating about 26 - 28 oz AUW.

I'm going to need to run both the aileron servo wires and power lines for the speed controllers out to each engine pod. Would there be any issues with interference to the servos if all those wires run in the same groove?

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 01-20-2014, 12:36 AM   #7
DHC Beaver
Member
 
DHC Beaver's Avatar
 
Join Date: Nov 2011
Location: new zealand
Posts: 226
Thanked 18 Times in 18 Posts
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (1)
Default

I have a rat's nest of wires in my FW Ente,but have no problems with interference.I did run the motor wires in a separate paper tube though.IMHO, you should think seriously about keeping the motor wires separate,as they would be the "noisiest".
Did you put any dihedral braces in the gull wing part?Look forward to developments.
DHC Beaver is offline  
  Reply With Quote
Old 01-20-2014, 03:09 AM   #8
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

Originally Posted by DHC Beaver View Post
Did you put any dihedral braces in the gull wing part?Look forward to developments.
Yes - there is an 1/8" square pine spar top & bottom, then vertical webs of 1/16" ply at the joints, glued to the pine spars. All epoxied together. Should be pretty strong, I'm thinking.

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 01-20-2014, 03:33 AM   #9
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,171
Thanked 216 Times in 207 Posts
iTrader: (0)
Friends: (1)
Default

Depends on expected weight and style of flying if that will be adequate. A butt-joint of a spar may as well be silly putty if it doesn't have a good doubler.

The glassing may or may not be enough... You can get away with a lot with a smaller model such as yours. The same techniques with larger model I'd expect the wings to fail.
fhhuber is offline  
  Reply With Quote
Old 01-22-2014, 12:11 AM   #10
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

And the wing is pretty much done:



It's covered in packing tape (which doesn't do compound curves) so we've got a lot of dark triangles where the tape is doubled up . But I think once the fuselage, engine pods and invasion stripes are in place the dark spots will be much less noticeable.

Originally Posted by fhhuber View Post
Depends on expected weight and style of flying if that will be adequate. A butt-joint of a spar may as well be silly putty if it doesn't have a good doubler.
Apparently I did not describe the wing joints adequately. The two (top & bottom) spars are joined in lap joints with a plywood gusset with the angle of the wing cut into it, and extending an inch each way into the joint. The foam is a butt joint, but not the structural stuff. I'm sure the joints are considerably stronger the the straight sections.

On to the fuselage!

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 01-22-2014, 01:14 AM   #11
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,171
Thanked 216 Times in 207 Posts
iTrader: (0)
Friends: (1)
Default

OK... looking good so far.

You can use heat with some of the packing tapes to get them to do compound curves Works well for getting out wrinkles too.
Test on tape applied to scrap foam. Sometimes the foam deforms before the tape shrinks or stretches.
fhhuber is offline  
  Reply With Quote
Old 01-24-2014, 10:44 PM   #12
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

I like the stripes :



The white is "Duck Tape", the black is electrical tape. I cut the white to size by placing it on wax paper and cutting with a razor blade.

On to the front landing gear. On the real B-25 the front wheel is just a caster - it is not steered directly. Ground handling is done with the rudders, brakes, and differential thrust. On my model I'm skipping the rudders and making the front wheel steerable through the rudder channel. So I need to make a nice sturdy pivot point, and I'm going to mount it in rubber to adsorb some shock & hopefully protect the wire strut.

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 01-28-2014, 12:14 AM   #13
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

And starting on the fuselage:



That wooden thing is the mount for the above-mentioned front wheel pivot.

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 01-28-2014, 11:49 PM   #14
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

And it's kinda taking shape:



I've run a couple of 1/8" sq spruce strips from the nose wheel structure back to the tail (sort of visible in the picture).

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 01-29-2014, 07:55 AM   #15
baz49exe
Super Contributor
 
baz49exe's Avatar
 
Join Date: Jun 2008
Location: Devon. England
Posts: 1,101
View baz49exe's Gallery15
Thanked 135 Times in 130 Posts
Club: East Devon Radio Control Club
Awards Showcase

Outstanding Contributor Award  Scratchbuilders Award 
iTrader: (0)
Friends: (15)
Default

"Looking good" Dave.
I still use spruce for spars and fuselage keels and it works very well for me too!

Baz
baz49exe is offline  
  Reply With Quote
Old 02-02-2014, 12:55 AM   #16
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

A little more work on the fuselage, and the engine pods roughed out:




Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 02-02-2014, 01:45 AM   #17
DavidR8
Member
 
Join Date: Sep 2013
Location: Victoria, BC
Posts: 234
Thanked 2 Times in 2 Posts
iTrader: (0)
Friends: (1)
Default

Nice work...looking forward to seeing the progress

Flying more, crashing less. Feels great!

Champ, Super Cub, Fun Cub
DavidR8 is offline  
  Reply With Quote
Old 02-02-2014, 03:38 AM   #18
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,171
Thanked 216 Times in 207 Posts
iTrader: (0)
Friends: (1)
Default

Watching... planning to scale up and build one "a bit" larger...
fhhuber is offline  
  Reply With Quote
Old 02-02-2014, 05:19 PM   #19
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

I'm getting close to needing to run the wiring out to the engine pods. Here's the plan:

In each pod will be an ESC for the motor and a servo for the adjacent aileron. I'll have a separate UEBC in the center fuselage. So as I understand it, I'll need to run a + and a - wire at battery voltage to power the ESC, then a + and a - wire at servo voltage, and two signal wires (one for the servo, one for the ESC). So a total of 6 conductors, two of heavier gauge.

Does that sound right?

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 02-02-2014, 08:59 PM   #20
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,171
Thanked 216 Times in 207 Posts
iTrader: (0)
Friends: (1)
Default

The amount of wires sounds right.
fhhuber is offline  
  Reply With Quote
Old 02-02-2014, 09:31 PM   #21
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

Originally Posted by fhhuber View Post
The amount of wires sounds right.
Thanks

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 02-02-2014, 10:10 PM   #22
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

It's starting to look like something:



I put in 1/8" plywood plates for the rear landing gear, gorilla glued directly to the foam of the wing. (Inside the engine pods) Hope that's strong enough .

I think it is...

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Old 02-03-2014, 12:23 AM   #23
pmullen503
Member
 
Join Date: Mar 2011
Posts: 850
Thanked 71 Times in 70 Posts
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (3)
Default

Don't forget to disconnect the red (+) wires from your ESCs if you use a separate UBEC. Though at this size, it might easier to run ESC's with built in switching BEC's and just disconnect one of the ESC's red wires.

It's never too late to have a happy childhood.
pmullen503 is online now  
  Reply With Quote
Old 02-03-2014, 12:38 AM   #24
CHELLIE
Super Contributor
 
CHELLIE's Avatar
 
Join Date: Oct 2006
Location: Hesperia, So. Calif
Posts: 18,606
View CHELLIE's Gallery13
Thanked 2,162 Times in 2,070 Posts
Club: Chino Renegades RC Flying Club
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Ambassador Award  100mph Speed Demon 
iTrader: (4)
Friends: (311)
Default

Looking Good Subscribed

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
CHELLIE is offline  
  Reply With Quote
Old 02-05-2014, 12:20 AM   #25
dgjessing
Member
 
Join Date: Jul 2012
Location: Columbus, OH USA
Posts: 540
Thanked 12 Times in 12 Posts
Club: Westerville Model Aeronautics Assoc.
iTrader: (0)
Friends: (0)
Default

Here's one of the rear landing gear legs in place:



Most of the work was in making a stamping tool to form those hold-down straps. I've since slathered epoxy over the straps and screws to hold them in place, as there is not going to be any easy access once things are buttoned up.

The motors and ESCs and stuff arrived today! (They were in postal limbo since being ordered the 19th of last month )

After piling everything I could think of on the scale, it looks like it may hit the high end of my estimated AUW of ~28 oz. We'll see .

Dave
AMA #56519
dgjessing is offline  
  Reply With Quote
Reply

  WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > Scale E-Powered Aircraft

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Scale A10 from Wowplanes - Big Bird awrightbrother Scratch and Kit Built Aircraft 9 12-19-2011 11:27 PM
Scale Fishbonez Beginners 7 10-29-2011 10:17 PM
EFlite Beaver with Scale Floats velyter Seaplanes E-Powered 8 07-26-2011 03:18 PM
Roy Vaillancourt 1/5 scale L-19 Bird Dog electric conversion tenacious101010 Warbird Electrics 13 06-23-2011 12:03 AM
For Sale Pilot-1 PA-12 1/8 Scale ARF SOLD 1987tc Airplanes - Electric For Sale & WTB 3 01-07-2011 10:00 PM


All times are GMT +1. The time now is 04:16 AM.


Powered by: vBulletin
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

Charities we support Select: Yorkie Rescue  ::  Crohn's & Colitis Foundation



Page generated in 0.63146 seconds with 69 queries