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Airfoils, Ordinates, Fat Wings, Harry Riblett and other musings…

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  • NCLSA183
    commented on 's reply
    Regardless of how carefully words may be chosen, there is always room for personal interpretation. A reader should not hesitate to question any statement that may seem vague, misleading or differ significantly from generally accepted norms. I hope, as well, that arriving at an unintentional conclusion was not the case in this conversation.

    I respectfully suggest that a bit less vagueness from the designer would be greatly appreciated by those who wish to understand the reasons and rational behind mid-design modifications and especially in regards to drawings that don't factually represent the designers published specifications. This has been somewhat problematic for years without resolution. Unless, of course, one was sufficiently openminded and receptive to data from sources other than the designer.(wink)

    Thanks for allowing this topic. Ironically, and in reference to my original post, it is I that wishes for a refund of his time...
    Mitch

  • NCLSA183
    commented on 's reply
    Thank you Dave. I enjoyed the read.

    Mitch

  • NCLSA183
    commented on 's reply
    rv8bldr. Mark, thank you for adding your 2 cents. I’m glad this conversation got you up from that very comfortable looking chair with the beautiful trees in the background.

    As someone who has endured some very long coding sessions over the years, I submit that your eyes may likely have been glazed over long before you starting reading this topic. (wink)

    I certainly agree with you in regard to the inconsistency of the hammered ribs. But that is an area where we have a bit of control without adding very much to the build time. The airfoil mylar drawing represents the size and shape of the completed wing, cross section. Allowing for rib flange and skin thickness when making the rib form blocks would result in a completed wing that would better match the mylar and, therefore, more likely have the flight characteristics that were originally intended by the designer. And remember, we don’t know the intentions of the Dwg 4 modification.

    Based upon the analysis by nborer, a few line widths don’t appear to make any truly noticeable difference, but yet, Bob considered it important enough to make that small change to the Riblett 30-613.5 airfoil without any flight testing to quantify the design or verify and compare the results. A very talented, current builder of a large wing Bearhawk recently told me that his completed wing came in at 0.210 inch thicker than the mylar drawing. Will this person be just as happy flying around with that extra weight, drag and likely loss of performance or will he be wondering “what if” as he questions whether or not to load that trophy moose into the aircraft? To borrow a slogan from the Army, my little LSA wants to “be all you can be” so I’ll be making every effort to assure that. Due to the reasons I wrote in some other posts, I will now be using LSA Dwg 4 as the profile for my build.

    Mitch

  • NCLSA183
    commented on 's reply
    Thank you, v.x, for your comment. You succeeded in getting an answer to a question some of us have asked but failed to obtain. It does confirm my thoughts from an earlier post.

    Discrepancy, like beauty, appears to be in the eyes of the beholder. It doesn’t seem that the designer or the kit manufacturer consider it to be a discrepancy, or at least one worth noting. Possibly because it ##doesn’t affect the safety## of this aircraft. By definition, the differences that I have outlined in this conversation are, indeed, discrepancies. Subjectively speaking, the last place that I want to find discrepancies would be in the plans for an airplane that I was building and/or flying, regardless of its proven flight record. And, any unexplained and undocumented discrepancy, as is in the LSA plans, would, in my opinion, be problematic enough to warrant the questions that I have presented in this topic. NOT problematic in regard to any safety reasons. I have never said or meant to imply such. But rather, problematic, as defined in being “difficult to solve or decide”. My reasons are outlined throughout this conversation.

  • NCLSA183
    commented on 's reply
    stinger. You are wrapping “duck” tape, nborer is getting attacked by “duck” shoes while I’m having trouble keeping my “ducks” in a row… Maybe we need a new topic. LOL Nice performance numbers on your LSA. I truly enjoyed following your progress. Congrats!!

  • NCLSA183
    commented on 's reply
    About 10% of my work over the years has been the design, prototyping and building of custom electronic projects for clients’ niche applications. I would design the hardware and code the software and/or firmware and not once have I ever thrown a shoe, of any kind, at my alter ego. You guys should grow up and stop clowning around before someone loses an eye!! Just learn to get along and play nice!! LOL

    Mitch

  • NCLSA183
    commented on 's reply
    Nick, so sorry for being AWOL for a few weeks! My dang ducks would not stay in a neat row as I had instructed them. A couple of them just had to get out-of-line and take up most of my free time the past few weeks. I am, of course, referring to clients. My plan was to take down my shingle at years end but that date might slip a bit. As may my LSA start date. But I still have hope.

    I suspect, that after you read my post #22, you likely saw the writing on my wall. In the beginning, I either stated, or alluded to, the fact that I had no intentions of attempting to redesign, reengineer or otherwise modify the design of the LSA. I couldn’t if I wanted. I only wanted it to be a true Riblett 30-613.5, as the plans partially were and as it was advertised. So, when I discovered that I had not verified the aileron dimensions on Dwg 10, and subsequently learned that it matched with Dwg 4 instead of Dwg’s 3, 5 & 9, then my quest to build a true Riblett 30-613.5 wing was over. Even if I could, I had/have no desire to try designing and building a new aileron that would complement the 30-613.5 wing. Case closed…

    What have I learned from all this? Well, quite frankly, some things that I am greatly disappointed with. Was this only an exercise in futility? Depends on one’s outlook. Was it avoidable? Yes. But I don’t regret the time and knowledge that I gained. And, I truly enjoyed the interaction with the members of this forum. What a great bunch of generous and knowledgeable people. Thanks to you all.

    Nick, again, thank you for your patience, expertise and, most of all, your time. I can’t say that I’m surprised by the results of your comparisons but it’s really nice to see it confirmed by your analysis and calculation’s. And, of course, I always knew that you were biased, from the git-go. LOL Who wouldn’t be! You also understood where I was coming from with my questions and curiosity and, instead of writing me off, you made extreme efforts to help me understand and to answer my questions. You are, mi amigo, a great asset to this forum and will always have my sincere appreciation and respect.

    Sincere regards,
    Mitch

  • stinger
    commented on 's reply
    I did not cut my nose ribs , I wrapped Duck tape around the tip two layers . I think it turned out well. Yes wing ribs may be different however my LAS fly's quite good .I have 21" tires, Cont. 0200 with a top speed of 135 mph at red line of 2750 rpm. Cruise 2450 rpm around 110mph. Stinger

  • rv8bldr
    commented on 's reply
    And it was taken in jest, Nick :-) No worries....

  • nborer
    commented on 's reply
    Said in jest, of course. My brother is a software engineer, so we've been trading barbs for the last several decades.

  • rv8bldr
    replied
    Originally posted by nborer View Post

    Stuff deleted....

    But seriously, a software guy? That's where all the problems originate! (*Ducks shoe thrown in my general direction.*)

    Nick
    At one time them would have been fightin' words.... However, I'm less than 2 years from pulling the plug on working for a living so I find that aspersions don't stick anymore.

    Leave a comment:


  • nborer
    replied
    Originally posted by rv8bldr View Post
    What Jared said...

    While this discussion has been educational, we aren't building an SR-71 or an F-104. In fact, our VNE is lower than the stall speed of both of those :-)

    Also, keep in mind that many of us are scratch building and are hammering our ribs out over a wooden template: there is no way in, well.... you know, that all of our ribs are *exactly* the same as the kit ribs. I would argue that not all of the ribs in a wing are *exactly* the same, although you probably can't tell that by eye. The kit ribs, however, are as close to perfection as you can get WRT the plans/mylar template.

    There are many Bearhawks happily speeding and STOLing around and they couldn't care less about a line width on the plans here or there. The airplanes are wonderful to fly, have great performance, and have no nasty gotchas.

    By all means, carry on with the academic discussions (I'll admit my eyes glazed over a bit after a while...I'm a software guy...) but for those that are concerned/confused, don't be. Bob knows what he is doing and designing. The proof is in the flying (both scratch and kit built) and there is a LOT of proof out there....

    My $0.02
    Hear, hear. I do NOT want to steer anyone away from the plans. I was about to start forming my aileron spar web prior to my inadvertent shop "closure," and the plans very clearly say "check for fit with rib" right next to the dimensioned spar height. In order to fit my aileron ribs (without joggling - another religious argument that I won't dive into), my aileron spar web needs to be about 0.1" taller than the dimension showed in the plans. Lack of joggling will only account for half of that variation. Yet, when I lay my ribs on my formblock and compare to the Mylar, they look pretty darn close to me. I guess I went a little more to the outside of the line. I'm not sweating it. When my build comes in heavy, this will be one of the 1000 reasons.

    But seriously, a software guy? That's where all the problems originate! (*Ducks shoe thrown in my general direction.*)

    Nick

    Leave a comment:


  • rv8bldr
    commented on 's reply
    Sorry, Frank, I can't answer that question as I am scratch building 4pl A model. I don't think I've even seen an LSA is the flesh. I'm sure someone will be able to answer it for you. The point I was trying to make was to not get all wrapped around the axle about the minor differences between the "book" and the plans on these type of aircraft. Unless you are Bob Hoover or some other highly qualified and experienced test pilot you aren't going to be able to tell the difference. And even then....

  • Frank
    commented on 's reply
    Factory nose ribs (LSA) are different from scratch built ribs in an important way. The former have a flange all the way around the nose while the latter do not. In fact, scratch noses get trimmed (LSA) while factory noses do not - or am I wrong?

  • rv8bldr
    replied
    What Jared said...

    While this discussion has been educational, we aren't building an SR-71 or an F-104. In fact, our VNE is lower than the stall speed of both of those :-)

    Also, keep in mind that many of us are scratch building and are hammering our ribs out over a wooden template: there is no way in, well.... you know, that all of our ribs are *exactly* the same as the kit ribs. I would argue that not all of the ribs in a wing are *exactly* the same, although you probably can't tell that by eye. The kit ribs, however, are as close to perfection as you can get WRT the plans/mylar template.

    There are many Bearhawks happily speeding and STOLing around and they couldn't care less about a line width on the plans here or there. The airplanes are wonderful to fly, have great performance, and have no nasty gotchas.

    By all means, carry on with the academic discussions (I'll admit my eyes glazed over a bit after a while...I'm a software guy...) but for those that are concerned/confused, don't be. Bob knows what he is doing and designing. The proof is in the flying (both scratch and kit built) and there is a LOT of proof out there....

    My $0.02

    Leave a comment:

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