Dillon Francis Oberholzer dillonfrancisoberholzer1970@gmail.com

Initially,

Starting as an apprentice with Atlas Aircraft out side Johannesburg in South Africa, I was trained in fabric stretching. The laminating of structural members came next and finally I went on to riveting.

This training and experience opened my eyes to foil design and the flex tolerances of different materials. Although, at the time, composite forming was a new and evolving industry. Much of the knowledge and research articles on infusion techniques were still written in German and had been developed during WWII.  The concept of infusion had been shelved by the world for 30 years.

By 1996 Vacuum forming had been privately researched and using negative pressure to create a positive form had captured the imagination of many builders in different industries. The Aeronautical and marine industries were the first to apply this technology on a commercial scale as limited as it was then.

Leaps and bounds have since been made in the last 30 years.

Much of my work and experience has been in the marine industry, however, I have dabbled in some wing design and fabrication projects keeping up to date with some of the latest production techniques.

Dillon Francis Oberholzer.


Composite Laminate Wing Structure - Wood Frame 

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Leading edge and foil rib structure

  • Epoxy and glass laminating with lots of sanding.

  • Trailing edges are finished with aluminium. 

  • All lateral cross members are riveted. 

  • Epoxy is post-cured at 80 degrees F.

  • Fuel Tanks are inset prior to final wing covering. 

  • Airlerons are fabricated and attached with control bars and wires inside the wing. 

  • Airleron surfaces are all fabric.


Aluminium Framed wing Construction

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Aluminium Lay-Up

  • All structural elements are cold formed and pressed into shape over a mold prior to layup. These parts can be ordered, however, these we made with just 3 tools (molds).

  • Alignment and wing lay-up requires a jig to make over a pattern to hold the parts together prior to clamping and riveting. 

  • Holes are press formed and cut to add strength and reduce weight.

  • Flaps on leading edge allow for riveting of leading edge to bulkhead. 


Aluminium and Fabric Ultralight Wing Design

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Aluminum Welding 

  • These foil sections were cut using CAD designs and a water jet.

  • Patterns were supplied by the designer  in Cad format.

  • Laser interface allowed for precision cutting with less than 0.5 mm spacial tolerance.

  • This is required for the tubes to fit as the cold rolled aluminium tubes are never exactly equal in diameter along the length of any one stick. 


Aluminium & Carbon Composite Fabrication

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TRICKY WORK

  • This requires fine attention to detail. 
  • Where you join aluminium and carbon surfaces the edges need to be roughed for maximum mechanical adhesion . 
  • After the laminating has cured you have, (depending on your epoxy supplier), up to 30 days to post cure.
  • This process has to bring all parts up to a level 100 degrees for around 6 hours for the epoxy parts to equalize and not pull each other apart over time. This process of post curing is vital to the strength and adhesion, not to mention the expansion and contraction of parts formed at different initial curing temperatures. Something I learned from Boeing employees I hired in Seattle.

Aluminium & Wood with Composite SkinCold form Laminating 

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Cold form Laminating

  • This is a simple process once the foil ribs are molded.
  • The skin here is pre-vacuum infused  on a flat-stock table. 
  • The ribs are then placed with tube form strut - bulkheads as a framework on top of lower skin prior to laminating.

 TOOLING - Vacuum Forming - Molding 

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Composite Part Fabrication

  • Regardless of how the positive plug is fabricated the process of vacuum forming is the same whether you are working with poly-carbonate or pre-pregnated and refrigerated laminates. 
  • Temperature control per material requirements and attention to detail in the process is critical.
  • Preparation.  Preparation.  Preparation. 

 


Carbon & Honeycomb

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Ultralight Wing forms

  • The simplest designs require the ultimate attention to detail. 

  • Losing structural elements (simplification of design), reduces the limits of error.

  • This foil design attaches to the fuselage with careful laminating and requires pre-stitched laminates templated over a mold to create the form prior to vacuum bagging. 

  • If you look closely at the top of the wing surface all structural elements are incorporated into the foil prior to machining.


Dillon Francis Oberholzer

Custom Design - Manufacturing - Management

Initially, starting as an apprentice with Atlas Aircraft out side Johannesburg in South Africa, I was trained in fabric stretching. The laminating of structural members came next and finally I went on to riveting.

This training and experience opened my eyes to foil design and the flex tolerances of different materials. Although, at the time, composite forming  was a new and evolving industry, much of the knowledge was still written in German and had been developed during WWII.  The concept of infusion had been shelved by the world for 30 years.

By 1996 Vacuum forming had been privately researched and using negative pressure to create a positive form had captured the imagination of many builders in different industries. The Aeronautical and marine industries were the first to apply this technology on a commercial scale as limited as it was then.

Leaps and bounds have been made in the last 30 years. Much of my work and experience has been in the marine industry, however, I have dabbled in some wing design and fabrication projects keeping up to date with some of the latest production techniques.

Dillon Francis Oberholzer.