So long, Cessna

As part of my effort to raise capital for for my forthcoming laser scanner upgrade, I’ve decided to reluctantly part ways with my trusty and extremely clean 1969 Cessna 172K.  I’ll be very sad to see it go, but if I have to choose between an airplane and a laser scanner, I choose the laser scanner.  I’ve listed it for sale on Barnstormers.com, so if you know anyone looking for a very nice full IFR Cessna 172, send them my way!

Comments
3 Responses to “So long, Cessna”
  1. Bill Dodson says:

    Sorry to see your plane go, I know what it’s like. I’m putting my sailplane up for sale soon (gone back to hang gliding) and considering a cnc router purchase as well as some hang gliding gear. Toys… Best of luck selling your plane.

    What are you looking at it the way of a laser scanner? My work got the last generation FARO laser scanner and the output is close to useless on even the most basic shapes. A rapidform xor salesman was able to do quite a bit with the data, but its another 10-20K on the 100K scanner. The included software cannot even register the scans accurately, which XOR does handily from the original data… I end up with a mess of fuzzy points about 2mm deep on flat surfaces (might be OK for scanning a building; certainly not a car). Would like to find other users of the same to find out if anyone has made it work for them. I was not around when it was bought. Be really sure you can use what you are getting YOURSELF, in YOUR shop on YOUR parts. Salesmen’s parts usually scan perfectly, but 90% of them fall on their face when you hand them something off your bench to input. We looked at a bunch of units the last place I worked and none of them really did what we needed all that well. Started taking critical items to a service using a faro touch probe arm.

    Anyhow, I enjoyed your site and am very grateful for your technique explanations, as I too want to use t-splines to draw airplanes. I’m an aero engineer, structures and flutter analyst, Rhino driver and CNC programmer/machinist, with background in sailplanes and composites.

  2. Bill –

    Thanks so much for your thoughtful comments! Don’t feel too bad for me, I’m going to be buying a 1/2 share of a VariEze from a local friend of mine, which I’m actually thrilled about.

    Well I was going to keep it a secret, but I may as well let the cat out of the bag and let you know I’m getting an EXAscan by Creaform. I will go into the “why” of this once I have the unit in my hands this week, but suffice to say I think this unit completely blows the FARO products out of the water, for the work that I do. My gripe with FARO is that since so much of their business is inspection based, they don’t seem to understand the whole class a surface reverse engineering aspect of things. At least, I would not say that’s their core competency.

    That being said, there is no substitute in my book for rebuild the scanned data into a T-Splines or NURBS surface. Even with the Creaform unit, to really get the type of surface you or I would find acceptable to machine, you have to rebuild it. I can’t say right now how I will be converting those surface meshes into T-Splines/NURBS, because the way I will be doing it has not yet been publicly announced by the software mfg, but suffice to say I think it’s going to really blow your mind. I should be able to post about it in roughly one month, when the company makes the information public. What I can say is that this new method is far superior to the rapidform type approach, and at a fraction of the cost.

    -Sky

    • Bill Dodson says:

      I am very interested in and look forward to seeing what you and the hardware/software vendor come up with. I trust you have run through the scan to end product (surfaces) process from start to finish a few times and verified its technical and economic adequacy before considering such an investment. My present employer blew $100K on a scanner based on the word of a salesman to an uninformed professional buyer with no verification of fitness for purpose whatsoever. I hope I can salvage some value from this mess but so far I have only hit dead ends. I don’t know if there is much hope for this scanner for anything beyond architectural work (in all fairness, it would probably be great for architecture). I was involved with with the laser scan of a B-52 years ago and the first vendor who tried could not do it. mainly due to failure to obtain decent registration between scanned patches. Another one did the scan in several days using dozens of targets, but took three months for a full time staff to deliver surfaces.

      An engineer friend has been doing reliable scans with a white light projector and two digital cameras on a beam for a reasonable investment. Lots of small patches and huge quantities of data (= slow processing) due to the necessity for lots of overlap, however. He also needs to keep a square steel tube (painted white/black every couple of inches) in the scan to remove optically induce curvature across the length of a vehicle which he gets if he just registers the patches to each other. He is getting the job done but taking days to scan and surface a car. He recently ran in to another guy with a service doing full aircraft scans with a very high end $250K German white light scanner, who can scan and deliver a high quality finished car model (SLA triangles, I believe) in a single day by comparison. Most of the scan data processing is automated once the scanning is complete. Very practical. Outside of this guy I have not seen a practical setup in fifteen years of looking, just tons of promises that turn out to be pure BS, but I am still a believer.

      I got started in the field working for a concept/movie car studio with a Tarus touch probe digitizer/clay mill that could scan or cut a 5′ cube and be indexed fore/aft on rails on either side of a car sized model. We’d do sections every couple of inches and fair curves through the points, then surface the curves (all on a 66 Mhz pentium with AutoSURF/AutoMILL). We could sculpt one side of a concept car by hand until we got the right look, scan it and cut the opposite half in a fraction of the time of traditional methods, with complete symmetry and deliver a CAD model with it. The digital file allowed us to build chassis to fit the shape and design tools and bucks for the body molds. Scanned and surfaced a ton of one company’s models for competing car design studios. Did this for a couple of years in a very fast paced environment day in day out, and we made it work mainly due to the genius of the owner figuring how to make it all work together and teaching me (he was good at it, but had a company to run). Once I felt I had learned what I could and realized the inherent limitations involved I returned to aerospace and a real salary. It worked decently for the day but was brutally labor intensive. They now used very high end white light scanners and megabuck software to do the same, but have struggled to make a business out of it considering the equipment cost. Got to see a lot of traditional tool and moldmaking there and elsewhere, which was very valuable exposure.

      Regards,

      Bill Dodson

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