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  1. #21
    Hi Ivan:

    Lost my thread post, so here goes. I reviewed Raymers textbook against his homebuilders book and I'm definitely going to recommend his homebuilders book to you since he addresses questions you've raised (like wing placement) in ways not covered in his bigger book:

    https://www.eaa.org/en/eaa-shop/medi...r-homebuilders

    I also like Chris Heintz's book (Zenith aircraft founder/designer) - good stuff about structures and stability:

    https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

    I also like Snori Gudmansson's (gotta love that Scandinavian name - takes me back to my time in Sweden book on GA aircraft design:

    https://smile.amazon.com/General-Avi...oding=UTF8&me=

    I really like Gudmansson's book for all the design process. I primarily bought these books as a way to help me evaluate homebuilt designs. Snori's book (he's not boring - check for his youtube videos) was especially good. I found out a design issue (I think a pretty big one) in a plane that was being hawked at Oshkosh. You should have seen the look of worry on the hawker's face when he saw me noticing the cludgy features of the plane's wing. I kept my mouth shut - Caveat Emptor, his potential customers should buy the books too. The hype sales approach should have been their first warning though (mine too). I recently referred to the Gudmansson book about issues I saw on powered paragliders with front castoring wheels. I wanted to see what he said about geometry and shimmy. If you read the reviews on Amazon, they laud the fact that he has the derivations of the formulas too. His language is straight forward like Raymer, and he covers a ton of issues around small aircraft design. I've actually got both an electronic version and a hard cover version since the diagrams in the hard cover version are only in black and white. It also gives me the opportunity to do detailed searches electronically. The physical book is huge, like a reference should be.

    Do you know of any online forums for using Raymer's programs/spreadsheets? I don't know if you want to keep yours propriatary (in case you develop a plan set, for example), but maybe we could cross check each other's work. PM if you want to.

    Enjoying watching the evolution of your design,

    Michael

  2. #22
    and please keep in mind that I'm a mathematician and scientific programmer and not an engineer...

  3. #23
    Jeez - hard copies of Gudmundsson's book were hard to find:

    https://www.biblio.com/book/general-...SABEgKIwfD_BwE

    In addition to the Kindle electronic version, it's available on Google Play for the same price as Kindle ($120).

  4. #24

    Join Date
    Aug 2017
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    Quote Originally Posted by Michael Miles View Post
    Jeez - hard copies of Gudmundsson's book were hard to find:

    https://www.biblio.com/book/general-...SABEgKIwfD_BwE

    In addition to the Kindle electronic version, it's available on Google Play for the same price as Kindle ($120).
    Same with Airframe Structural Design by Niu. Pricey.

    Anything with stress concentration factors (Like Peterson's) is highly expensive as well.

    My Raymer book was about $300 from what I recall...

    Sent from my XT1585 using Tapatalk

  5. #25
    Raymer's text book with the student software is $160 on amazon (so a bit cheaper than your school):

    https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

    I've got both, but prefer his spreadsheet for my project. If I go light sport, I'll probably try using the RDS software. I've heard it has some display issues in Win 10.

  6. #26
    EAA membership qualifies us for a free version of Solidworks, but I'm not sure if it does FEA. There's an online FEA,CFD simulation software at https://www.simscale.com/ - its use is free if your design is posted for open use on the website.

  7. #27

    Join Date
    Aug 2017
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    Quote Originally Posted by Michael Miles View Post
    EAA membership qualifies us for a free version of Solidworks, but I'm not sure if it does FEA. There's an online FEA,CFD simulation software at https://www.simscale.com/ - its use is free if your design is posted for open use on the website.
    I have all the tools I need for that. I can do a fair amount of hand calcs to preserve the months long headache of FEA and get pretty close yet stay conservative. When the time comes, I will break out the advanced mechanics of materials book and refamiliarize my self with Castigliano and work-energy methods.

    CFD isn't particularly important unless you're looking for world class drag estimates or designing a very specific airfoil. I can use XFLR5 for a decent estimate of airfoil qualities. Stability and control can be done in AVM with some work. Both of those are capable and free. Drag estimates are usually handled through historically based estimates and refined with some basic aero-theory. Also free.

    As for CAD, I am very familiar and proficient with CATIA. I used to be a research assistant at NIAR during school and took nearly every one of the classes. I can take another class, which work will pay for, and get a temporary license through it when the time comes.

    Being that I am a fledgling engineer (I started school at 35) and still paying back an inordinate amount of student loans while raising three boys as a single father, this project must necessarily be low cost.

    I appreciate your suggestions and will look into the website you mentioned. However I would be wary of posting an aircraft design on open source due to possible liability issues...?

    Sent from my XT1585 using Tapatalk

  8. #28
    Hi Ivan:

    Thanks for the additional resources - I'll check them out. I appreciate the budget approach, and I suspect ultralight folks mostly share that in common. In fact, I think that's probably a driver for most homebuilders. It certainly is for me. Didn't think of the liability issue, but I'm not an engineer. Curious to see how you design the fuselage - not sure how you're going to avoid making it out of aluminum foil given FAR 103.

    Michael

  9. #29

    Join Date
    Aug 2017
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    Quote Originally Posted by Michael Miles View Post
    Hi Ivan:

    Thanks for the additional resources - I'll check them out. I appreciate the budget approach, and I suspect ultralight folks mostly share that in common. In fact, I think that's probably a driver for most homebuilders. It certainly is for me. Didn't think of the liability issue, but I'm not an engineer. Curious to see how you design the fuselage - not sure how you're going to avoid making it out of aluminum foil given FAR 103.

    Michael
    Well, if you've heard the phrase "Boeing builds 'em better", you probably have a good idea how that will work.

    The 737 fuselage has skin panels as thin as 0.040" thick and that holds pressure and contributes to the structural make up of the fuselage. Inside are stringers and frames attached to the skin with tension clips and shear ties.

    Methinks if 0.040" thick aluminum works for a 189,000 gross weight craft, probably some 2024-T3 clad foil will do the trick. Most likely 0.016" thick or there about. I will also, more than likely, use some aluminum angle or U channel about 0.050" thick or there about for stringers. I suspect I will end up figuring out how to form some frames with a home made rubber box or bladder press and a pressure washer. My initial thoughts are 0.050" thick on that as well.

    Amazingly, it appears most 103 aircraft look like they are "sized for stiffness" and not built optimally for weight. Analysis and trade studies will tell the tale soon enough.

    I don't think I will get into sizing for 20,000 flight cycles, except on the critical baseline structure that is difficult to access and repair. I am guessing that, If I can use a semi monocoque design, inspection will be easy and any cracking will be readily apparent so I won't have to do a lot of damage tolerance analysis. Especially if I can design for inherent damage tolerance.

    I am open to any good sources of indestructium alloy if anyone has any. Also need plans for a turbo encabulator...the one with twin spurving bearings.

    Sent from my XT1585 using Tapatalk

  10. #30
    Quite a few trouble shooting issues with the Quicksilvers related to hard landings:

    http://www.ultralightnews.com/quicks...g-reports.html

    I think Ultralights tend to be floaty due to their light weight, and susceptible to even light gusts on landing. It's one of the reasons I'm building a quad rather than a trike after seeing too many wobbly paraglider trike landings. Good aileron authority at stall should help, but light is still easy to blow around. Structural consideration around the landing gear might be important - I'm agonizing over it myself.

    You mention inspection. I saw a youtube video about using an inspection camera for aircraft:

    https://www.youtube.com/watch?v=VEHJLXdHSLo

    If you build with this in mind, you may gain access to all of your internal areas for inspection.

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