Building Lasers

[Rcmaster199 at aol.com]

Gee whiz, Bobby, I thought I was the only one.
 
Wayne, take your square and add its mirror image. You will have a right  
isosceles triangle with the base being the hypotenuse and the vertical center  
line bissecting the triangle. Draw several parallel lines to  the hypotenuse and 
they will all be at right angles to the vertical  bissector. These serve to 
line up the stab at the same time the fin post is  being aligned. Essentially it 
becomes an inverted T
 
I made mine from a 1/8" piece of plexiglas. It is fairly large right  
triangle with a hypotenuse some 28" long. It is a super tool for locating the  stab 
and fin exactly at 90 degress to each other. With a little more ingenuity,  it 
serves as a fixture to hold things lined up while the glue cures
 
Matt
 

ANYONE who has looked at my stuff knows full well  that I mark things with a 
Magic Marker, then cut with a Chain Saw....my lasers  are just to make me feel 
better before hacking.

Bob Pastorello
_rcaerobob at cox.net_ (mailto:rcaerobob at cox.net) 
_www.rcaerobats.net_ (http://www.rcaerobats.net/) 
 
 

----- Original Message ----- 
From:  _Wayne Galligan_ (mailto:wgalligan at goodsonacura.com)  
To: _discussion at nsrca.org_ (mailto:discussion at nsrca.org)  
Sent: Monday, October 25, 2004 1:55  PM
Subject: Re: Building Lasers


Keith,
 
On the square for lining up the rudder  post.   
If you have perpendicular lines layed out on  your table you just lay the 
square on the line that is perpendicular to the  fuse.  This way you can tilt the 
square forward or back(in the case of  a canted rudder post) and still have a 
square post.  Of course a  scribed line in the center of he post is needed.  
I use the Great  Plains center scribe for this as it will make a center line 
that will  conform to a tapering hinge area.
 
Wayne G.

----- Original Message ----- 
From:  _Keith Black_ (mailto:tkeithb at comcast.net)  
To: _discussion at nsrca.org_ (mailto:discussion at nsrca.org)  
Sent: Monday, October 25, 2004 1:24  PM
Subject: Re: Building Lasers


think lasers are hugely helpful in some  cases. I find them particularly 
helpful when trying to draw a straight  line on an unlevel surface, or a 
particularly large area such as a line  across an entire room. An example of an unlevel 
surface for modeling would  be drawing a straight line right down the center 
top of a fuselage from  the top of the fin to the front of the nose, or when 
drawing a line down  the side of the plane. In both of these cases you're 
working with a curved  surface and the laser will follow the contour (be sure it's 
lined up  correctly).  

The down side to lasers I've found are: One,  the laser I have has a 
relatively thick beam as compared to the accuracies  we need, between 1/16th" and 
1/8th" depending on distance. It's harder to  be exact that you would think. 
Second is that you can sometimes be misled  when the beam goes across surfaces that 
curve further away or closer to  the source of the beam. This will distort 
the beam unless  it's exactly even with the location you wish to draw the  line. 
 
After messing with lasers in the past to try  and do alignment I feel the 
best way to align the stab is to have a level  table, put a scribe line on the 
rudder post and use a square to make sure  the fin is perfectly perpendicular to 
the table. Then when mounting the  stab use a height gage to make sure the 
stab is exactly the same height  from the table at all points (front corners, 
back corners, center fronts,  center backs). This will yield a perfectly aligned 
stab, height wise at  least. You also need to make sure the stab tips are 
aligned equal  distance from some center point in the front of the plane (I won't 
go into  this, the best bet is to buy Bob Noll's tapes).
 
What I sometimes find difficult in this  process is eyeballing the square and 
the rudder post to make sure indeed  the fin is exactly 90 degrees to the 
table. In some cases you can butt the  square right up to the rudder post, but in 
other cases you can't do this,  or the rudder post is at an angle. This is 
when my eyes play tricks with  me since the square isn't up against the scribe 
line. In this case a laser  may be useful, however remember that the laser must 
be perfectly lined up  behind the rudder post (side to side) or the angle of 
the laser  combined with an angled rudder post will cause the line not to be  
true.
 
For the alignment of the main wing it's  necessary to use some type of 
measuring gadget, like Bob Noll describes,  to make sure the wing tips are equal 
distance from the stab tips, but when  it comes to the wing tips being lined up 
height wise to the stab tips I  think this can be done more accurately using 
the eyeball than with any  measuring tool (at least the tools I have). If you 
stand ten of fifteen  feet in front of the plane and position yourself exactly 
in the middle of  the fuse you can raise and lower your head and see if the 
wings are even  with the stab. Also do this from behind the plane. This can be 
done with  incredibly accuracy. In fact, I've done it using measuring tools and  
afterwards found that my tools couldn't get it as accurate as my eyeball.  
And since you've made sure the stab is correct it's a good measure for the  
primary wing (I set my stab first). 
 
I've used the a laser to confirm my eyeball  measurements for the wings being 
level with the stab, but due to the  thickness of the beam, and the fuzziness 
around the edge of the beam, it's  tough to get it to the accuracy of my eyes.
 
BTW, I didn't pioneer these methods. It's  thanks to other modelers that have 
shared their approaches to doing things  that I know this. Out of all the 
different methods that have been  suggested to me these are the ones that I find 
work the best.
 
For anyone who's new to building, or just  wants more tools for their 
building arsenal, I strongly recommend Bob  Noll's tapes. The one for alignment is 
called "Perfect Airframe  Alignment". You can order them at 610-746-0106. He has 
a set of four tapes  that go through many of the difficult parts of building 
a pattern  plane.
 
Keith  Black






 
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