Click to return to Steen Aero Lab Homepage  
 
For the resolute and determined there is time and opportunity.
(Ralph Waldo Emerson)
 
Go to printable version 
 
  Our Aircraft:
 
    Steen Skybolt
Pitts Model 14
Pitts S1
Knight Twister

 
  Products:  
    ONLINE STORE

Products Home
Bruntons Brace Wires
     About Bruntons
MT Props
Hoffmann Props
     Request Prop Quote
Vendenyev M14 Engines
Laminated Wing Spars
Laminated Leading Edges
Canopies
Motor Mounts
Wing Kits & Wing Jigs
Three-Section Wings
Piloti Shoes
VedaloHD Sunglasses
     Styles
     FAA Report on Sunglasses

 
  Builders:  
    Builder F.A.Q.
Construction
   Photos

Articles
Project Gallery
Submit Photos
Project Logs

 
  Resources:  
  News
Event Reports
Email List
Testimonials
Non-US Distributors
Links
Scale Models
Biplane Lore
About This Site
Website Updates
About Us
Contact / Visit Us

 
   

 
Project Log
Aircraft Construction - Pitts 14 Prototype

Fuselage Side Panels, Wing Rigging, Engine Arrives
Pitts 14 Prototype
Created: 06/28/2004
Updated: 10/27/2004
Link(s): N/A
 
Article by Mike Whaley
 
Curtis paid us a visit at the beginning of March. Work continued on the side panels, mostly, finishing touches. The inner panels which protect the wing root area and provide for a more aesthetically-pleasing appearance in the cockpit area came out well.

We continued to make a lot of progress on the wings, finishing the major structural components. The construction style will be familiar to those who are familiar with the Skybolt or Pitts Special construction methods, though there are some neat features embedded into the design. Obviously, our goal is to make the construction process as easy as possible and we have developed a few things to facilitate this along the way.

On March 16th, we received a present... the 400hp M-14PF engine arrived, courtesy of our friend George Coy. Upon opening the box, we found that the engine had leaked about a gallon of oil into the bottom of the packaging materials... well, at least we know it's well lubricated! The engine comes with seals, spark plugs, and even a tool kit with some rather unusual-looking tools. Our engine is an electric start model. Ours even had the original Soviet Union-era nameplate still attached (these engines are generally made in Russia or the Soviet Union, and are refurbished in Romania before being exported.)

Some folks like the air start version, but we feel that it would probably be a bit more practical to have the electric-start version. If you are at any airport in the US and get caught with a dead battery, you can almost certainly find DC power. You may have a bit more difficulty in finding a bottle of compressed air equipped with a connector you can use. (Some of the guys with air-start M14's carry a whole kit of various adapters for this purpose.) Of course, if you fly in Eastern Europe or Russia, it's entirely possible that it's easier to find compressed air at your airport than DC electrical power! We expect to see both flavors of starting systems used successfully on the Model 14.

We reached an exciting milestone on March 25 when we mounted all of the wings to the airplane. For the first time, all the major components were connected and it looked like a whole airplane! The impression it gives is a tall, stout, beefy biplane. The plane has a sort of "presence" all its own. Curtis sure looked like a proud papa watching his latest plane come together in a recognizable form.

Rigging the wings was an interesting process. First, a long digital level was used to get the fuselage square, both fore-aft and left-right (pitch and roll axes.) Then the lower wings were connected, and supported by wooden stands. Then the cabanes were attached, followed by the center section. The center section required a sheet of plywood to be clamped to it for support, since it wasn't yet finished to the point where it would be fully dimensionally stable. To help with the alignment, plumb lines were attached to the mounting screws at the top of the cabanes. There are several alignment issues going on at once... the structure can sway left-right, fore-aft, or any combination. In addition, if it moves one way, it will be skewed and misaligned in another direction. Since the cabanes aren't a parallelogram, if the center section moves left or right, then one side ends up higher than the other. This is one place a digital level is vital! In essence, we had to figure out where each part should be, adjust it to get there, and then re-adjust everything else to get them back where they were supposed to be. As the wires were installed and tightenened up, it got progressively easier until we reached the point that the center section was secured into the proper place all around.

Once the center section was secured, then the upper wing panels were attached and supported on wooden stands. The landing wires were added first, which supported the lower wings, and then the I-struts were added which in turn held up the upper wings. For many of these we used some spare steel tie rods we had in the shop, which is why not all the linkages in the photos are the shiny stainless Bruntons wires which we will ultimately install on the finished plane. (Yes, we have to buy the wires from the factory too, so we wanted to work the dimensions out first!) At this point, it was a matter of just adjusting things until everything worked out.

In addition to refining the plans and parts as we go along in order to smooth the construction process, we have been developing a few tools and fixtures to aid with the more difficult tasks. In the photos you can see two such tools. The first is an alignment jig used to drill the critical I-strut attachment holes. Obviously, drilling quarter-inch holes vertically through your precious wing spars can be a bit nerve-wracking, but with a good fixture it can be made a lot less stressful.

This jig is actually very simple in concept and operation. The correct location of the top and bottom of each hole is marked on the top and bottom surface of the spar. The jig, which is essentially just a tube with a cutout for the spar and some structure to hold it in alignment, is clamped onto the spar with C-clamps (using scrap wood blocks to protect the spar from the clamps, of course.) Then you sight down the tube to align the top and bottom exactly with your marks, and tighten the clamps to hold it firmly in place. We used folded paper shims for the fine adjustments. When it is just right, you can drill your hole with confidence. This was a 2 or 3 person operation, in part just because you want to be sure that someone is holding onto the heavy steel jig while you're looking up at it from the bottom, lest it slip and smash your head as it falls to the ground. Having this happen will cost you many brownie points with the spouse, as it could easily send you to the emergency room and deplete your airplane building budget!

We also developed a jig to solve an age-old question: how do you align the holes for the drag and anti-drag wires inside the wings? Many folks have used the TLAR method (That Looks About Right) with varying degrees of success... you can find many planes with wallowed-out holes or slightly-bent wires as a result of this method. Obviously, this isn't up to Steen's high standards. Our solution involves a universal drilling jig (it will work on almost any simlar airplane) that is extensible lengthwise, with two drill alignment guides at each end. Each end also has an adjustment screw to precisely set the height of the drill guide tube at each end. (Essentially, the jig is just a mechanism whereby two tubes - the drill guides - are held precisely in-line with each other regardless of their distance apart, with provisions made to help hold them in place against the airframe. This ensures that the drill bit will always point exactly at the far hole.) To use it, you just mark where the holes should be (on the maple wire blocks) and place each end of the jig where the ends of the wire will go. You then lock in the length of the jig to match, and then make fine adjustments to the hole's vertical placement on the maple block. One person holds one end in place, while the other one drills the hole on the opposite side. In places where the wire will connect to a tab on the interior of the wing, you just have to hold that end of the jig against the tab.

The results obtained with this wire-drilling jig were excellent! In roughly one hour, we had made all the holes for the drag wires! One thing you have to remember is that the wires have to be staggered vertically so that they can cross each other in the middle, ideally they will just barely touch (if they touch at all.)

Sun 'N Fun preparations started to really pick up during March, but so did the energy level. We were very motivated to get the plane ready to show, knowing that we had a large audience waiting to see it. While we had it assembled, we even tested out the best way to fit it into the tent.


Click to view full image
Curtis and Barrett discuss the Model 14.  
Click to view full image
The interior panels really clean up the cockpit area.  
Click to view full image
The panels and fairings really help smooth out the lines of the plane.  
Click to view full image
This gives an idea of the excellent access the side panels will permit.  
Click to view full image
The wing is coming along nicely.  
Click to view full image
This is the crate the engine arrived in.  
Click to view full image
A genuine Soviet -made aircraft engine tool!  
Click to view full image
Once upon a time, the American aerobatic team flew Pitts Specials and completely embarassed the Soviet aerospace giants in competition. Now, the Russian engines are powering the latest Pitts.  
Click to view full image
Just like a radial should, it leaked oil into the crate. It was just practicing for the real thing!  
Click to view full image
What a beautiful sight!  
Click to view full image
They even give you a set of tools to keep handy... very practical.  
Click to view full image
Curtis supervises the initial rigging of the center section.  
Click to view full image
We used plumb lines from the mounting bolts to help align everything. This was a tedious, yet enjoyable, process.  
Click to view full image
The attach points for the cabanes are quite beefy.  
Click to view full image
Our waterjet cutter produces some beautiful hardware!  
Click to view full image
This is where the left foremost cabane attaches to the fuselage.  
Click to view full image
Finally... we have a real live biplane! This was an exciting moment for us all.  
Click to view full image
The landing wires supported the lower wing while the rest of the rigging was installed.  
Click to view full image
The upper wing joint.  
Click to view full image
This is the simple jig we created to align and drill the I-strut attach holes which go vertically through the spar.  
Click to view full image
Here's the I-strut drilling jig in use. You have to use shims and wiggle it around a bit until it's lined up just right.  
Click to view full image
The view down the drill tube.  
Click to view full image
Paul checks alignment before drilling.  
Click to view full image
This is a spare Skybolt canopy... it gives an idea of the canopy setup, though the Model 14 setup will be a different shape and setup.  
Click to view full image
While we had it together, we worked on how we would fit it under the tent at Sun 'N Fun.  
Click to view full image
The drag/anti-drag wire drilling fixture. It's adjustable in length. The drill tubes remain aligned regardless of other adjustments.  
Click to view full image
Here is a closeup of the end, showing the adjustable standoff used to brace it against the wire blocks.  
Click to view full image
If you're connecting one end to a tab inside the wing, just hold that end up to the tab.  
Click to view full image
Paul drills a hole in a wire block while John holds the far end firmly onto the wire attach tab.  
Click to view full image
Let the sawdust fly!  
Click to view full image
It's important to remember to stagger the wires vertically so they will pass each other. It really doesn't matter which one is high or low, but be consistent.  
Click to view full image
Paul measures in order to drill a hole in a compression rib. This took a little bit of eyeballing, but it worked out OK.  
Click to view full image
Paul drills the hole through the compression rib.  
Click to view full image
And again on the other side...  
Click to view full image
Perfect!  
Click to view full image
The other side shows how neat the holes come out.  
Click to view full image
As you can see, the jig makes for very accurate alignment without wallowed-out, ugly holes.  
Click to view full image
The installation is tidy on the inside as well.  
Click to view full image
The bigger your washers, the better. We use a 4130 steel plate over the whole face of the block to spread out the loads as much as possible.  
Click to view full image
All these wires took less than a single afternoon to install, not counting the time it took to build the alignment jig and the flat hardware (mostly just tabs and crush plates.)  

Other entries in this series:
     Construction Begins    May 2003
     Fuselage Basic Structure    June 2003
     Fuselage Basic Structure Completed, Engine Arrives, Steve Culp Helps Out    July 2003
     Pitts Model 14 Introduced at Oshkosh    4th week of July 2003
     Curtis Visits to Continue the Design, Wing Construction Begins    August 2003
     Wing Construction Underway    September 2003
     Lower Wing Basic Construction    October 2003
     Lower Wing Details and First Fuselage Formers    November 2003
     Fuselage Formers, Skin and Wing Details    December 2003
     Fuselage Side Panels and Upper Wing Construction    January 2004
     Wing-Root Fairings, Fuselage Skin Panels, and Upper Wing    February 2004
      » Fuselage Side Panels, Wing Rigging, Engine Arrives    March 2004
     Sun N 'Fun 2004    April 2004
     Summer 2004 Status Update    May 2004
     Aluminum Turtledeck    1st week of June 2004
     Sheet Metal Work, AirVenture    4th week of June 2004
     Adjustable Seats, Part 1    August 2004
     Adjustable Seats, Part 2    December 2004
     Wings    December 2004
     Throttle Quadrant    December 2004
     Spring 2005    March 2005

If you have any additions or corrections to this item, please let us know.

Go to Project Log archives

 
  Steen Aero Lab      1451 Clearmont Street NE   Palm Bay, FL 32905 USA     
Phone: (321) 725-4160      Fax: (321) 725-3058      Contact Us