Building Lasers

[Gray E Fowler]

Tom

Your plumb line is hanging the wrong direction! I think....



Gray Fowler
Principal Chemical Engineer
Composites Engineering




"Koenig, Tom" <Tom.Koenig at actewagl.com.au>
Sent by: discussion-request at nsrca.org
10/25/2004 04:43 PM
Please respond to discussion

 
        To:     <discussion at nsrca.org>
        cc: 
        Subject:        RE: Building Lasers


I use the same...plumb line from the ceiling for the fin.........then use 
a simple dumpy level to level out wings and stabs. I fill the plastic tube 
with Manometer fluid, but water with a bit of food dye will do the same.
 
Tom
-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On Behalf Of Fletcher, Richard
Sent: Tuesday, 26 October 2004 4:59 AM
To: 'discussion at nsrca.org'
Subject: RE: Building Lasers

The best way I have seen to line up a rudder post is to use a plumb line 
hanging from the ceiling.
 
 
 
Rich
 
 
-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On Behalf Of Wayne Galligan
Sent: Monday, October 25, 2004 2:55 PM
To: discussion at nsrca.org
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 
To: 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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