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Hummel UltraCruiser
Plans # 527

S. Steve Adkins
EAA 9221

Technical Adviser: Dale Johnson
Technical Advice: Chris Bobka
EAA Technical Counselor: Ami Sela
(Plus: Peter Denny for the first inspection)
First inspection: 1/30/2010

Created: 15 January 2009
Updated: 30 March 2015

New: Site Navigation
More links coming soon.
Page down for older links and a Matrix table of links.

Google search for Many Photos on this website 

Note: Google is no longer updating this set ... sorry.

Hoping my UltraCruiser will look this nice ... good head room!
Credits: Photo from Dan Johnson 
This website is undergoing substantial reorganization.  Some temporary links:
- Log ... the start of a daily log (we'll see how long this lasts)
- Bending Side Rails ... a difficult task

Status for the New Year 2015
Building has been on hold due to large home projects, work has restarted on the Hummel UltraCruiser this winter.  Items completed:
- Both outer wing panel fully riveted, ready for installation
- One-Piece, 8-foot ailerons
- Center wing spar
- Fuselage through "boat" stage with vertical stabilizer and rudder
    (Note: gas tank purchased from Hummel Aviation
- Parts laid out on sheet aluminum (to the far right)

Status for the New Year 2014 -- "You call that a drill?  This is a drill!" ... (Apologies to Crocodile Dundee)
Two wings panels, rear fuselage, vertical stab, rudder, two one-piece ailerons and center wing spar (not shown).
(Vacuum-formed Wing Nose Skins, Vertical Stab and Dorsal Fin)

More recently, I have been placing images on the Yahoo UltraCruiser forum. 
... my Yahoo ... Photos Sets include:
Misc - Construction Images: 58 Images ... Bending Rudder Skin, E2 Bulkhead, 3M Deburring Wheel, skinning rear fuselage, Dorsal Fin Drawing
Tools - The Good, the Bad and the Ugly: 38 images to help your selection of tools

Status for the New Year 2012 -- work begins after one year off.
I've moved.  New home has a 12 by 32 foot basement shop and a 3-car garage.
Also, I have a 6-foot wide, 25-foot long carpeted hallway by the shop for unrolling 4 by 12-foot sheets of aluminum.

I just added some photos on the Yahoo UltraCruiser form:  Steve's Yahoo Photo Album 

UltraCruiser Builder Progress Table
Note: Purchased Plans January 2008
Entire spar - FINISHED
Left wing - FINISHED
Right wing - Finished through Cleco stage

- Ailerons
- Wing tips
- Center wing panel

- Ribs for outer panels were built-up, truss-style ribs
- I purchased the factory formed ribs for the center section

first wing panel and full spar passed inspection 1/30/2010

Second wing panel passed inspection

Tailcone - STARTED
Finished E-E2-D section
Finished D-C section 4-20-2012

- use .040 on E2 Bulkhead
Formed Ribs for center section
Hardware kit
Vert Stab parts only
Firewall forward:
Planned Purchases:
1/2 VW engine

Landing Gear:


Hummel Aviation 
        Note: Aircraft Spruce available
        through Hummel Aviation


New items added to this webpage:
    Sonex Wing Tip  ... worth a look for an easier wing tip to build
    Goofs ... A listing of goof and solutions complete with embarrassing photos!
Mistakes & Do Overs  ... a friends' Sonex project
    Buried Cleco ... it takes a 4-foot arm to remove ... this is old, but worth a look.

    Starter? ... Electric Drill for a starter, or are you having too much fun flipping the prop.


Hummelbird Trailer/Hangar
    - Page 1 
    - Page 2 

Charles and Rick fly two new UltraCruisers: ...  Building Ends, Flying to Begin!

In addition to the links in the table, page down for about 50 Random construction images

Navigation Matrix

Parts Finder Spreadsheet
- Sort by Sheet
- Sort by Assembly

Material Testing 

Changes Made 

... includes remedies

Mistakes & Do Overs 
... a friends' Sonex project

Damaged UC 

Wing Tip Design - Sonex 

Hummelbird Trailer/Hangar
- Page 1 
- Page 2 

Rivet Workstation
Video: 20 rivets in 4 minutes 


Cordless Drill Starter ... why flip props?
Rib Construction

Built-Up Rib Construction

Squeeze Riveting 

Nose Rib Support Fixture 
This solves a nasty problem

Wing construction

Spar - Taper Pins
- Taper Pins ... note, builder of a
British 1930 Chilton D.W.1 is using taper pins
after reviewing my webpage and checking
with expert Chris Bobka.

Establishing Wing Dihedral
- Wing Spar Drilling Jig  by Charles' and Rick's
  (from - UltraCruiser Blog ... Charles Snyder)

Vacuum Forming
-  My Nose Skins
   ... includes vacuum forming images

- YouTube vacuum forming demo
     ... if the above is missing try:
     -  My Video of vacuum forming
     -  Very slow to load ... large
     -  You can download this video

-  Charles Snyder - Horiz Stab
      Page down 2/3rds
      Video and still images
-   Charles - Video Only

Wing Panel Assembly
- Fixture Supports Nose Ribs 
- Bottom Skins 
- Wing Stand

Removing Dimples in Skin
This process proved to be almost worthless
- The problem  
- Tools  
- Removal Process  

-  Aileron Mock up 

Final Riveting
- Completed left wing panel
      (including all riveting (except end rib)

When I started this project ...
Email Contact: [   ]

   S. Steve Adkins ...     

The original Hummel Bird was designed for:
        5-foot, 7-inch pilot weighing 160 pounds.  

The UltraCruiser is designed for 
        6 foot, 4-inch pilot weighing 225 pounds.        
A few years later ...


Parts Finder Spreadsheet
While on a month trip to So. California, I used spare time review the UltraCruiser plans.  During this time, I created a spreadsheet listing every part contained on the 19 sheets.

-  There are about 660 parts
-  About 1/3 are unique or only two like parts
-  The rest are duplicate parts such as rib parts
WARNING: Do not rely on this list.  Use your Official drawings to determine the parts and correct materials required to build your aircraft.

Website Editorial Policy & Copyright Notice
These pages are presented here are for the use, education and enjoyment of those interested in homebuilding.   No claim is made for the accuracy of materials presented. Content and/or policy opinions expressed within these pages are solely those of the author. They DO NOT necessarily reflect the position of any other person nor organization. Responsibility for accuracy in referred and hyperlinked materials rests entirely with the applicable author and no remuneration is made.
Copyright 2008, by S. Steve Adkins, all rights reserved. 
Links to Spreadsheet
- Sort by Sheet
- Sort by Assembly

... Left-click on most photos for full-size and more-complete image ...


Click on Photo for larger and complete photo
 Taper Pins

... note, builder of a
British 1930 Chilton D.W.1 is using taper pins
after reviewing this webpage and checking
with expert Chris Bobka.

Progress: 7 July 2009
Skins were formed using vacuum technique described by Charles Snyder.  
Page down for photos and movie.  
Charles suggests using a 2-inch pipe.  I used 1-7/8ths inch plastic drain pipe from my scrap pile.  
I will add a webpage showing my process.  Vacuum forming was the easiest and most satisfying task so far.
See my vacuum forming process.

Also, be sure to visit my webpage: Nose Rib Support Fixture which solves a pesky problem.

Progress: 22 June 2009
I delayed riveting the second upper skin until the D-Cell is complete.

Larger Image:   med   large


Status: 2/15/2009 - Outer Wing Panel - 5 ribs complete, 2 to go


Current Status: 2-19-2009 all ribs in place except for one nose rib
(Viewers with sharp eyes will notice that one rib is a formed rib and not a truss built-up rib.)
This rib is what you get from Hummel Aviation ... isn't it a beauty!  Notice the largest lightening hole is "squared" at the bottom front..
I purchased this rib for comparison and review with EAA Chapter 25.  
I have been building using precise hole location ... as a result, I was able to mount the factory rib as the pre-drilled holes matched mine!


Height from table: Adkins Truss -Style Built-Up Rib on left and Hummel Aviation Formed Rib on the right
(Tilt of spar on table adds 1/16 inch measurement which should be 9 and 22/32nds or 11/16ths)

I will be starting a spreadsheet with the actual
weight of parts as they are built.
To date:
Nose rib and mid rib =  6 ounces
(and they transfer 100 pounds of lift to the spar at 4.5 Gs)
Spar with fittings   =  6 pounds approximate (no bolts yet)
Lightening holes in spar web saved = 7.4 ounces both spars

Jim T. , Yahoo! Groups Sponsor reports:
A truss-built rib (nose and mid rib) at 5.94 ounces, or 8.395lbs for a set

Mike, Hummel Aviation, reports a set of formed rib at  9 pounds, 2 ounces
So the updated truss ribs are about 13 ounces lighter than the laser-cut formed ribs.

100 Years of progress
My first two ribs: UltraCruiser and 1903 Wright Flyer
(The Wright Flyer was funded by the State of Minnesota)

Better view of the rib with flanging die
Circle hole flanging die "turned" by Dale Johnson 
Modified nose rib per suggestion by
Peter Denny (Sonex builder).
Bill Batzloff also came to the same conclusion.
An additional change was made to the rivet pattern ... see below.

Built-up Nose Rib for the WWII Spitfire!

These two photos are from the March 2008
issue of Air & Space 

Note: For comparison, I have included photos of a built-up rib for the WWII Spitfire shown in the March 2008 issue of Air & Space magazine.   Compare the Spitfire photos to the photos below.

Spitfire Mid-Rib and wing structure
If formed ribs are so great, why aren't they used here? I know why.
(By the way, I understand that Hummel makes a great set of formed ribs.)

     Back Issues/Reprint Policy 

Rivet Station ... rivet squeezer clamped in vice
Note: see below for a new holding fixture.  

Reaching a difficult rivet
Rail section holds angle brace while allowing total freedom for placement

Improved squeeze rivet work station ... shown with nose rib.
Two tubes hold the squeezer vs. clamping in the vise.
This allows rotation of the squeezer.  
The left or right tube is selected
based on required
space for your hand during the squeeze operation.
Note: Mounting board is from a busted Ice Boat plank.
Huge aircraft bolt replaces railroad track.

Squeeze rivet work station - close view
Vice, squeezer, yoke and support angle can all be positioned to reach
difficult locations while ensuring that the squeezer is perpendicular.
Here the change to the rivet pattern can be seen.  The
lower flange is made longer to allow the rivets to be longitudinal
rather than perpendicular.  Also, the formed piece has a 
simplified corner at the lower and upper -rear corners
allowing for a straight cut with your tin snips.

Squeezer shown with a mid-rib

A "no space" plans desk ... workbench to the right (not shown).
Fast and inexpensive to build ... light weight, easy to move.

Insert sides filed flat for tight riveting ...
Note: if the squeezer inserts lean against
the assembly,
 the rivet will be driven crooked (bad) and may split (worse) .
(both top insert and bottom insert have flat sides cut and polished)

.020 aluminum sheet (4x8 foot) ready for cutting ... no that isn't a mirror

Cutting guide is clamped (not absolutely necessary)

Inexpensive cutter ... make 20 strokes, bend and brake off piece./

As the groove gets deep enough, the cutting stroke makes a different sound.

Spar web, cap and fittings ... temporary assembly.
Note: Basement assembly workshop. Hopefully, I'll
lose 20 pounds running up and down stairs between
the basement workshop and the garage.


The wing shown here is the right-outer wing panel.

The total wing consists of a center section and two outer wing panels.

Each outer panel is a little about 9 feet.

The center section is a little about 7 feet.

Total wings span is 25 feet.

End view of fittings
Fittings machined by Dale Johnson

Three-quarter view of end fittings
End Polishing, more hole drilling and deburring remain to be done

Top view of first trial assembly mating rib to spar.

Photo by Dan Johnson

Review of wing assembly
Note: circle-hole flanging dies "turned" by Dale Johnson.

Too much effort vs. using a flanging hand tool?
(Not when some one else volunteers to make them!)

Front view ... note ribs for 1903 Wright Flyer on wall above
100 years and a significant change in technology!

 Take a look at Mr. Fujita's wing with formed ribs:
 His complete gallery at the Hummel website:

Edge view ... note spar web vertical stiffeners

Another edge view

3M polishing wheel ... source Avery Tools (SKU 3753)
Available from several aviation suppliers.
This is the wheel recommended for RV builders.

Photo on left show the grove created to smooth edges on aluminum
This is totally SUPERIOR  to any other method of deburring an edge.

More on this later ... see preliminary discussion to the right ----->

<------ Hole drilling guide or Index Bar                                                  

I have tried a number of methods to create an accurate hole guide.

In matched hole tooling, it doesn't matter if the guide is imperfect
.... as long as it is placed correctly on matching parts.
But, I wanted a guide that was perfect so that it can be flipped and flopped and still drill a matching pattern.

In my scrap pile, I discovered an aluminum bar bought at a Control Data employee sale
over 30 years ago.  Aluminum was being sold at scrap prices.  This bar is from a super computer chassis.  It is straight, relatively thick and had accurately drilled holes at  one-half inch intervals.  The holes were tapped for 6-32 machine screws.  These threads nicely capture the silver or the small Cleco which fits a #41 or 3/32nd drill bit.

The holes are #35 drill in size.  I have drilled out every over hole and inserted
brass tubing which is then press fitted by pounding an awl into the tubing
followed by pounding on the end of the tube with an 1/8 inch drift punch.  This produces a hole that fits the smaller #41 drill for 3/32nd rivets.  I may drill out the other holes to fit a #31 drill.

Work bench, plans table, shelving and tool stands.  
Table saw and compound cross-cut saw under work bench.

Plans table allows extends over wife' car.
(See Goofs as to why this is a bad idea)

Small belt sander to the left, bench drill press  (center left) and band saw (far right)
Shelving holds drill accessories, battery chargers, hand drill stand, misc tools.

I hope to buy a house with a three-car garage and walkout basement workshop.
You haven't built an airplane until the project has been moved at least once!
I moved ... 3-car garage and huge shop in basement.

January 2008:
Bought plans and some tools during December.  Started building January 2008.  
Have built one full rib (nose and mid rib) using the built-up design ... total weight = 6 ounces

January 16, 2009
Primary effort has been purchase of aviation metal-working tools and changing basement and garage shops over to metal working shops.  Also, investigating material sources and purchasing enough material to build one wing panel.  Also, considerable effort building jigs for the nose-rib and mid-rib.  A form block and drilling guide was made for the formed nose piece (yes, the built-up ribs have a formed piece).  Several hole drilling guides have been built.  Much effort here and many discards (you know the drill).

February 2009
Built second spar web.  Five ribs are finished, two to go ... then I start skinning the wing panel.  Charles Snyder also recommends completing the total spar web at this time working on a flat table with bend that matches the dihedral and the drill press mounted at work table height.

August 2010 through April 2011
Bought a house, repairs to old house, repairs to new home (sat empty for 3.5 years), partial move, staged old house, put house on market, sold house ... final move.

Due to shop size limitations, I drilled the main spar attachment holes one set at a time.

Shared Technology:
Truss-Style Built-up Nose and Mid-Ribs ... WWII Spitfire! (Air & Space Smithsonian, March 2008))
Rudder bar ... Grumman Navy G-44 Widgeon amphibian (right side seat only - AOPA Pilot, March 2000)
 Photo: Dan Johnson  

Do you need to sell a home in the Twin Cities ... here is the man that sold my home during the worst real estate market in my life; plus, it was winter!

Rich Hansen ... Realtor
Virtual Tour  Property Information  ... this virtual tour was so great, my grown up kids wanted to move back home!

Note: I am not receiving any form of compensation for this notice.

[ End ]

Address of this Webpage:

Copyright 2008, by S. Steve Adkins, all rights reserved. 

Disclaimer: Website Editorial Policy & Copyright Notice
These pages are presented here are for the use, education and enjoyment of those interested in the world aircraft homebuilding.   No claim is made for the accuracy of materials presented. Content and/or policy opinions expressed within these pages are solely those of the author. They DO NOT necessarily reflect the position of any other person nor organization. Responsibility for accuracy in referred and hyperlinked materials rests entirely with the applicable author and no remuneration is made.