Building Lasers

[Ken Thompson III]

Hi Matt,
I originally started my first post with" Unless somebody builds on a surface plate, how would it be possible to measure incidence that accurate?", however I changed the wording thinking, nobody needs that close of a tolerence.
You doing your set-up on plate glass is as accurate as you can get other than a surface plate situation, even slab marble isn't ground to tolerences that close.

I am very new to the pattern world, as next year will be my first full season of competition.  This year I only hit about half of the available contests in my district.  I see that I have a lot to learn.

My plane already flies better than I do, however I am going to take care of that next season.

Thanks for a few hints for my next set-up.

Ken
  ----- Original Message ----- 
  From: Rcmaster199 at aol.com 
  To: discussion at nsrca.org 
  Sent: Sunday, October 24, 2004 3:32 PM
  Subject: Re: Building Lasers


  Ken, pattern models need that kind of accuracy, and more, there's no doubt about that. Bob has probably found that the lazer's accuracy of 0.1 degrees is adequate for flying. If wings were off compared to one another by 1/32" (0.1 deg), I believe that you would be able to see a difference in roll. But if overall incidence (bothe panels compared to stab) was off by 1/32", you would probably trim and keep on flying.

  The Robart incidence meter is okay as a broad reference device, but high accuracy is not obtainable by this meter. It isn't made precisely enough for our purposes; the variation in the plastic components is the killer. The concept is not a bad one however; the blocks would need to be machined precisely from block aluminum.

  Also, consider that any scribe mark you could place anywhere on a model as the refernce mark to measure from, is at least about 10 thou thick. So the best you could do in reality is to measure accuracy to within 10 thou or so, based on your scribe marks' thickness, no matter the meter you use. 

  For this reason, I prefer a simple height gauge with a carbide scribe pointer. The scriber edge is approximately 1/2 thou thick so I can dissect the 10 thou thick reference marks I placed on my wings, stabs or fuselage. Then I am completely at the mercy of my  building surface. I use plate glass for set-up and check it often for trueness when I am building. Believe it or not even plate glass with take a set, so I rotate the surface periodically

  regards

  MattK



  Honestly Bob,

    I don't believe even the most precise fliers could tell if their wing was off that little bit, or that most incedence meters can read it that close.
    Unless you are doing your building off a surface plate, your chances of getting your fuse's thrust line "perfectly" level, so as to make your incedence's "that" close, are very slim indeed.  They will only be as close as the accuracy of your incedence meter.
    I would like to have the manufacturer and part number of the incedence meter that is that good, I just don't think my Robart is that close.

    Ken 
      ----- Original Message ----- 
      From: Bob Pastorello 
      To: discussion at nsrca.org 
      Sent: Sunday, October 24, 2004 8:35 AM
      Subject: Re: Building Lasers


      .1 degree is also just a shade over 1/32" difference EACH at the leading and trailing edges.  Understand that we need those kind of accuracies for best, but I believe most folks do NOT resolve incidence to 1/32"....but I understand the need to state precisely.

      Bob Pastorello
      rcaerobob at cox.net
      www.rcaerobats.net


        ----- Original Message ----- 
        From: Karl G. Mueller 
        To: discussion at nsrca.org 
        Sent: Saturday, October 23, 2004 10:06 PM
        Subject: Re: Building Lasers


        Bob,

        A tolerance of .1degrees is not very close to set the incidence.
        Over a wing root of 20" it works out to be .035 inch. This is the max.
        positive incidence I use on the wing when setting up a pattern plane 
        with the stab being set to zero.  A  .1 degree tolerance could give me 
        a setting between 0 and .070 positive when setting up a wing with 
        a 20" root.

        Karl G. Mueller
        kgamueller at rogers.com


          ----- Original Message ----- 
          From: Bob Pastorello 
          To: discussion at nsrca.org 
          Sent: Saturday, October 23, 2004 9:23 PM
          Subject: Re: Building Lasers


          The purpose of the ones I have is not to check incidence, but to verify alignment "square", and "parallel"...currently, a lot of folks use different methods, some height gauges, some fixtures.  When building a plane, I have always struggled with getting the stab square to the fin, and then the wing parallel to the stab...and these differences sure do make a difference in how a bird trims out.

          Incidence is checked with our electronic digital levels, at .1 degree accuracy :-)

          Bob Pastorello
          rcaerobob at cox.net
          www.rcaerobats.net
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