Prop Shop: Craig Catto's laser scanning station has rails to slide the propellers along and a framework that helps create alignment points for his scans.

Prop Shop: Craig Catto's laser scanning station has rails to slide the propellers along and a framework that helps create alignment points for his scans.

FEB 08, 2011,   

 My customers are people who fly homebuilt airplanes, and they tend to have distinct individual personalities. What they need by way of aircraft performance is specific and distinct as well. Our company, Catto Propellers, is in the business of design, analysis and manufacturing of composite propellers for the Long Eze, Lancair and RV series of aircraft, along with many design specific military projects . Several world speed and altitude records have been set with Catto Propellers and still stand—an achievement we take pride in.  One NASA project had Catto Propellers that flew in excess of 82,000 feet.  Just two months ago, the world records were set with Catto Propellers.

For years I endeavored to become a preferred source of custom propellers and build a viable company. I realized not long ago that Catto Propellers had succeeded in part of that but failed in another part. We had clients and revenue and profits, but no assets. All of the 1,000-plus design-and-build jobs in our files were of the “one-off” variety.

That’s what got me thinking about 3D digital scanning, so for a couple of years I asked all the smart people I knew in aerospace and other tech fields what they knew about the subject. Surprisingly, none of them had any direct experience with it. I wasn’t trained in engineering but I have a pretty persistent mind when I’m looking for technology to do my work better, so I kept at it.

The first scanner company I talked to had a unit that was priced well under the 3D Digital eScan but they wanted to charge me $60 an hour for training. I asked them if I flew to you with one of my propellers, could you show me how your scanner would work for me? They proceeded to tell me they would charge me $100 a scan!  I didn’t like that idea so I kept looking. When I first talked to Satish at 3D Digital Corp. he said I could fly from California out to Connecticut and get trained in person for no charge. So I did that, bringing along a sample propeller. I had a lot of questions about the effectiveness of the process and Satish just kept giving me the right answers. When I watched him scan it and create the digital file of its complete surface contour I felt like someone had robbed me. It was shocking to think that all that custom individual work could be captured so quickly and accurately. Obviously, that was the missing piece of my entire production process.  I now had the catalyst to make my company fully digital for CNC manufacturing. Now I take a product I’ve already built, scan it and reverse-engineer the resulting file with the tweaks I want to add.

Sometimes that’s a reduction in span, or a thinning or thickening of portions of the blade, or a change to the “pitch” (the twist profile of a prop blade). Then off it goes to the CNC. The propellers start as a laminated maple blank, then bias plies of fiberglass are laminated over the wood core.  Up to 36 plies are used on the three bladed propellers.  On the blade itself, the laminates of fiberglass build up to .080 inch thick from root to tip.  The fiberglass is more than a protective shell, it is the structural member of the blade.  In most cases now we also use Carbon Fiber for increased structural stiffness.

Before I even ordered my eScan3D™ scanner, Satish suggested that he set the focal length more specific to my type of work than the standard length. I’ve done some of my own customizing to the scanner workstation, setting up parallel rails for the scanner to ride along as it captures the prop surface. Because carbon fiber is black and not easy for the laser to “see,” and also because prop blades are so lacking in surface variation, I created a “contextual frame” to help the alignment software. They are stealth-looking triangles that float in mid-air.  Connected to flexible copper rods clamped onto the work table, they can be easily placed for triangulation so the files will mesh beautifully.

The amount of scanning I do now is pretty intense. I’m loading my archive prop by prop, and of course using existing stock to help me easily create the next order. Repeat customers and volume orders are now easily produced. Years from now I may not be scanning my existing propeller stock, because the files will all be loaded. But I am sure I will always be scanning every new blade I produce. Then finally there will be established asset value to my company for the future.