"1/2 A" & "1/8 A" airplanes These are the small ones...more popular now than ever.

Need help with lightweight twin rudder linkage

Reply
Old 11-05-2011, 05:48 PM
  #1
H5487
Thread Starter
 
H5487's Avatar
 
Join Date: Dec 2005
Location: Houston, TX
Posts: 1,074
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Need help with lightweight twin rudder linkage

Howdy Guys,

I picked up a BMJR Twin Lizzie with the intention of installing a small electric motor and RC gear. The Lizzie has only a 30" span and is designed for .020-.049 power so building light is important. Because this model was originally designed for free-flight, the plans don't show how to build movable rudders. So, I've got a couple of questions for y'all...

1. Since the rudders are not on the fuselage centerline, a belcrank will be necessary. What would be the lightest setup for rudder control?

2. To save complexity and its accompanying weight, can I get by with only one moveable rudder or do I really need both?

The plane won't be built for aerobatics; just a nice little Sunday afternoon flyer.

Thanks for your help,

Harvey

Attached Thumbnails
Click image for larger version

Name:	Ki19290.jpg
Views:	49
Size:	56.7 KB
ID:	1682735  
H5487 is offline  
Reply With Quote
Old 11-06-2011, 07:47 AM
  #2
mgnostic
 
mgnostic's Avatar
 
Join Date: Jan 2003
Location: Kamay, TX
Posts: 611
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Need help with lightweight twin rudder linkage

A pull - pull system with Spiderwire fishing line would be very light. Sounds like you are looking for R/C assist so if you do just one rudder there will be a little bit of asymmetrical drag but it should fly like a plane with a small rudder and a big fin. The Twin Lizzie has been on my to do list for a long time. I have a Lulla-Bi fuse framed up and need to finish cutting wing ribs some day.
mgnostic is offline  
Reply With Quote
Old 11-06-2011, 08:54 AM
  #3
H5487
Thread Starter
 
H5487's Avatar
 
Join Date: Dec 2005
Location: Houston, TX
Posts: 1,074
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Need help with lightweight twin rudder linkage

Hi Matt, thanks for your reply. How would you route the spiderwire?

Harvey
H5487 is offline  
Reply With Quote
Old 11-06-2011, 09:09 AM
  #4
combatpigg
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Need help with lightweight twin rudder linkage

The bell cranks and control horns can be made with 1/16" plywood. I would press eyelets into the bellcrank pivot holes for durability. You could also make the bellcranks out of thin nylon or aluminum.
The bellcranks might need to be built up into 2 tiers so that the incoming thread doesn't rub against the out going thread.
Once you dive into your project and start locating the major pivot points and end points it will become obvious to you what details you need to hurdle to get there.
To take up slack in the rigging, I run the thread in a continuous loop starting at one side of the rudder horn, through both holes in the bellcrank, then terminate the thread in the opposite side of the rudder horn.
Take a T pin and wind it up on any part of the loop of thread to take up slack, then secure the pin to the thread so it can't unwind.
To keep the rudder centered, use a #2 screw and locknut to clamp the thread to the bellcrank and hit it with thin CA.
combatpigg is offline  
Reply With Quote
Old 11-06-2011, 10:29 AM
  #5
D.J.
 
Join Date: Jun 2010
Location: Warren, MB, CANADA
Posts: 60
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Need help with lightweight twin rudder linkage

This is from the airboat section of this forum . I know that this is built far heavier than you would want but the idea is there . .... D.J.
Attached Thumbnails
Click image for larger version

Name:	Rp43139.jpg
Views:	71
Size:	63.4 KB
ID:	1682894  
D.J. is offline  
Reply With Quote
Old 11-06-2011, 12:15 PM
  #6
BobHH
 
Join Date: Jan 2002
Location: Holly Springs, NC
Posts: 1,856
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Need help with lightweight twin rudder linkage

I used a torque rod setuip on my Pee Wee Pal. Worked great!

Bob Harris
Attached Thumbnails
Click image for larger version

Name:	Qn38544.jpg
Views:	55
Size:	99.7 KB
ID:	1682929   Click image for larger version

Name:	Hc93487.jpg
Views:	75
Size:	50.1 KB
ID:	1682930   Click image for larger version

Name:	Rx59961.jpg
Views:	59
Size:	55.1 KB
ID:	1682931   Click image for larger version

Name:	Ys49032.jpg
Views:	49
Size:	126.5 KB
ID:	1682932  
BobHH is offline  
Reply With Quote
Old 11-06-2011, 01:25 PM
  #7
tubebass
 
Join Date: Nov 2010
Location: Saint John, NB, CANADA
Posts: 24
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Need help with lightweight twin rudder linkage

Found this here on RCU: a way to use the elevator hinge wire to actuate twin rudders!
Attached Thumbnails
Click image for larger version

Name:	Ki19899.jpg
Views:	88
Size:	85.5 KB
ID:	1682982  
tubebass is offline  
Reply With Quote
Old 11-06-2011, 01:34 PM
  #8
H5487
Thread Starter
 
H5487's Avatar
 
Join Date: Dec 2005
Location: Houston, TX
Posts: 1,074
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Need help with lightweight twin rudder linkage

These are all interesting ideas.

Thanks!

Harvey
H5487 is offline  
Reply With Quote
Old 11-13-2011, 10:19 AM
  #9
mgnostic
 
mgnostic's Avatar
 
Join Date: Jan 2003
Location: Kamay, TX
Posts: 611
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Need help with lightweight twin rudder linkage

Hmm. with the Spiderwire one could tie the rudders together and set it up as a closed loop with horns on the outboard side of the rudder. The down side is that your linkage is all hanging out in the breeze. I find myself linking BobHH's setup. Simple and light.
mgnostic is offline  
Reply With Quote
Reply


Thread Tools
Search this Thread
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



All times are GMT -8. The time now is 12:07 PM.