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

Rudder Only Design

Old 05-19-2015, 04:33 PM
  #1  
Cross Check
Thread Starter
 
Join Date: Jan 2005
Location: Oakville, ON, CANADA
Posts: 248
Likes: 0
Received 0 Likes on 0 Posts
Default Rudder Only Design

Hi All,

For the Design Contest, I am building an .049 R/E/T plane.
I would like to be able to set it up so I can flick the Mix switch on the Tx, which will leave me with only rudder control.

The goal is to do a Cuban 8, like they could in 1957 :
http://www.airplanesandrockets.com/r...ft-modeler.htm

From that article there is some trimming tips, but I'm looking for basic R/O design setups.

Like wing incidence, downthrust, dihedral, etc.

The design will fly R/E/T at 0 downthrust, +1 wing/0 tail incidence
I will make it so I can 'field adjust' the wing incidence and downthrust for R/O.

Any help will be appreciated.

Cheers,

Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
Old 05-19-2015, 08:31 PM
  #2  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,018
Received 7 Likes on 7 Posts
Default

Good project Dave..!
I've flown this way by accident, with a dead elevator servo.
The only advice I have is to cover it with semi-transparent iron on stuff so that you can see the 1000 piece jig saw puzzle frame work inside.
Old 05-19-2015, 09:07 PM
  #3  
Cross Check
Thread Starter
 
Join Date: Jan 2005
Location: Oakville, ON, CANADA
Posts: 248
Likes: 0
Received 0 Likes on 0 Posts
Default

Hey CP,

That 1957 article mentioned needing more power to do loops !
.35 was SMALL back then!

All sheet balsa construction, simple is Hard !

Cheers,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
Old 05-20-2015, 08:37 AM
  #4  
MJD
My Feedback: (1)
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,657
Likes: 0
Received 1 Like on 1 Post
Default

http://www.colinusher.info/Model%20A...der%20bug.html

http://www.airplanesandrockets.com/r...ft-modeler.htm (Same article??)


As a trend I'd say (without implying great insight or wisdom here!):

3-5 degrees downthrust (to prevent looping etc under power with the built in trim)
Right thrust as necessary (to keep it straight under power and prevent tightening up left turns too much I guess)
2-3 degrees decalage (smooth glide trim)
Enough dihedral for stability and rudder authority, less than pure FF

But as this article implies, the exact settings are aircraft/power specific.
Old 05-20-2015, 02:22 PM
  #5  
Cross Check
Thread Starter
 
Join Date: Jan 2005
Location: Oakville, ON, CANADA
Posts: 248
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks MJD,

I've tried it a few times with RET (Sig Kadet Jr, Randolph BeeTween and a Cox Centurion) by giving enough up trim for a steady climb.

Could 'slalom' upwind and get basic circuts OK,
But when I tried 'the spiral' for speed... there was no 'up'... (just speed!)

So I'm guessing it is a combination of decalage and downthrust. And perhaps a fwd CG for a glide with alot of decalage.

I can adjust the wing incedence with shims.
With a 'double' firewall I can make downthrust adjustable.
And easily field change engines, for more power, if the wind comes up...
(I like the part where you have to roll to get upwind !)

That reminds me...
I need to consider a RE Piped .049 looking good with downthrust !

Cheers,

Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
Old 05-21-2015, 09:38 PM
  #6  
Bipe Flyer
 
Bipe Flyer's Avatar
 
Join Date: Nov 2002
Location: Mission, BC, CANADA
Posts: 5,377
Received 4 Likes on 2 Posts
Default

Bruce has done this before and it flew really well. He'd be one to ask.

Attached Thumbnails Click image for larger version

Name:	DSCN6131.JPG
Views:	149
Size:	136.7 KB
ID:	2097571   Click image for larger version

Name:	DSCN6130.JPG
Views:	154
Size:	162.9 KB
ID:	2097572  
Old 05-22-2015, 10:11 AM
  #7  
BMatthews
 
BMatthews's Avatar
 
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,398
Likes: 0
Received 17 Likes on 15 Posts
Default

Did I ever get those picture files from you? I'll send you a PM with my email.

CC the way I set up the model in the pictures was to put the balance point a little ahead of what is normally done. Then I shimmed to set up for what looked like a good glide. But if you use your elevator you can use that as a trimming device instead.

As it happens the model shown is all together and sitting out so I was able to quickly check the CG location. It's 2 inches back on a 7 inch chord. So that's 28%. Then the model was test glided over the proverbial tall grass to set the shimming of the wing and tail to get a reasonable glide. Here again since you'll have "carried along shims" courtesy of the elevator you can set the balance then just trim once flying for the right climb under power and glide when the engine is off.

The trim that results from this balance point climbs fairly strongly under full power. In the case of the model you see it has roughly a 5 degree nose up climb at a fair flight speed which gets the model up to around 250 feet in about 30 to 35 seconds. From there I use the rudder to stunt up a storm of different loops and rolls. I can even manage a pretty decent Cuban 8 when flying it regularly by just rolling it back upright just a hair after the top of a loop.

You'll find that it requires a heap of downthrust to hold the nose down. Mine has a good 5 to maybe as much as 6 degrees relative to the center line of the wing airfoil. You won't get away with much less than that.

As it happened I found that the glide trim turned out to have a slight and slow stall bobble. I thought I'd want to trim that out but in fact I found that I was able to use this to allow shallow bank turns without the model diving. So I'd suggest you try the same glide trim and see how it works out.

Here again when I was on my game I could make my landing approach such that I'd level out from the last downwind leg turn with the model about a foot high just as the wings leveled. And the extra speed from the turn would be just enough to flare the nose up without actually climbing and the drag that came with the stall would slow and lower the model onto it's wheels before the break to a dive. When done well, which I was able to manage about 1 in 5 you'd swear that I had an elevator. When I'd nail it I made sure to hide my excitement and try to make it seem normal and regular....

The dihedral on the model shown isn't that much. But I suspect I'm getting some additional help from the beveled wing tip shape you can see in the second picture.
Old 05-23-2015, 04:13 AM
  #8  
Cross Check
Thread Starter
 
Join Date: Jan 2005
Location: Oakville, ON, CANADA
Posts: 248
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks Bipe and Bruce !,

This helps allot for me not 're-inventing the wheel' as far as R/O goes !

I'll have the elevator to 'bail out' with, if need be.

I am considering an HS81MG for firewall downthrust adjustment, rather than a throttle !

I think I am close to the ballpark. (pun intended !) Design wise.

Making room for the gear I have, with options for lighter stuff.

Snagged some nice 1/8th balsa from a LHS...

Project well on its way...

Just have to simplicate, and add lightness !

Cheers,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team

P.S. Several of the old school designs have swept back rudder hinge lines. Asthetic, or practical?
Old 05-23-2015, 07:05 AM
  #9  
Bipe Flyer
 
Bipe Flyer's Avatar
 
Join Date: Nov 2002
Location: Mission, BC, CANADA
Posts: 5,377
Received 4 Likes on 2 Posts
Default

I've always wondered how much a swept rudder effects AOA. Does it create enough down pressure to do anything?
Old 05-23-2015, 10:39 AM
  #10  
MJD
My Feedback: (1)
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,657
Likes: 0
Received 1 Like on 1 Post
Default

I read somewhere ages ago that you could achieve the effect of flattening out turns with about 30 degrees sweepback on the rudder.
Old 05-23-2015, 11:10 AM
  #11  
Cross Check
Thread Starter
 
Join Date: Jan 2005
Location: Oakville, ON, CANADA
Posts: 248
Likes: 0
Received 0 Likes on 0 Posts
Default

Hi Bipe,

I don't know...yet!,,, about the rudder hingeline...
I'm going for the 'looks cool' effect.

The further away, I get from an LST...
Makes this project :
A- Stupid
B-Possible
C-Might work
D-Don't worry
E- Will beat the pants off anyone else entering...

Answer, All of the Above !

Cheers,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team

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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.