Book recommendations? Structural design?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Hephaestus, Sep 29, 2019.

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  1. Sep 29, 2019 #1

    Hephaestus

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    So, after a summer of sitting around with Raymers aircraft design, and largely verifying what others had worked out by trial and error (at its heart it is a known and proven conventional design)

    I have a design on paper and mostly in CAD I'd like to start turning into a buildable aircraft.

    Plan has been to build mostly using rutan moldless method. Not the blasphemous melding of methods it currently uses.

    Curious if anyone has run across a book that walks through the engineering in a step by step manner? Break the engineering down into manageable chunks that a wrench bender like me can understand?

    Something like Raymers where I can sit with the book, notebook and calculator and have my hand held working through the calculations one by one, coming out with a general idea of a workable layup schedule I can have some faith in. I've read the stickies, I have the basic knowledge and maybe the math skills... But that step by step doesn't seem to be written anywhere.
     
  2. Sep 29, 2019 #2

    proppastie

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  3. Sep 29, 2019 #3

    Hephaestus

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  4. Sep 29, 2019 #4

    proppastie

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    Last edited: Sep 29, 2019
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  5. Sep 29, 2019 #5

    pictsidhe

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    I don't know of anything.

    Perkins + Hage, then Peery, then dig into one (or more) of the composites book is likely the usual avenue.

    Composites aren't simple to design. I don't think that there is a simple Idiot's guide type book. Too many variables and heavy maths for those who don't fully understand the topic.
     
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  6. Sep 29, 2019 #6

    Hephaestus

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  7. Sep 29, 2019 #7

    Hot Wings

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    Maybe Evans Light Plane Designers Handbook?

    It's not really a structural book but it does kind of outline the structural design process. Designing in composite is a big first project.
     
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  8. Sep 29, 2019 #8

    Hephaestus

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    Yeah, it definitely is.

    Let's file it under lifelong learning, like working through the raymers book - learned a bit as I went. Might actually make sense out of those dang engineers yet if I wrap my head around this :D

    As long as the math works, and looks ok when compared to the longez/openez/q1 plans I have... It makes for a quick sanity check and I'm not exactly trying to build a race plane, so extra insurance plies isn't going to kill me.
     
    Last edited: Sep 29, 2019
  9. Sep 29, 2019 #9

    rdj

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    With the caveat that I have never designed a composite airplane so all these books may be total junk for all I know...

    What you're looking for is roughly akin to looking for detailed design manuals, which are also scarce (unless you work for a major aerospace manufacturer and have access to the proprietary 'book' for that company). There are hundreds of books that present the same basic airplane design equations in different formats, but none I've found that walk you through a basic detail design, whether in metal, composites, or whatever.

    The closest I've found for detailed composite design for homebuilders is:
    https://www.aircraftspruce.com/catalog/bvpages/compbasics.php

    The Composite Basics book has IMO the most readable but detailed chapters on composite structures and calculating stresses and loads for various layups. If you're more the scholarly type, there's:
    https://www.amazon.com/Composite-Airframe-Structures-Michael-Chun-Yung/dp/9627128066

    Nui's book is definitely a textbook, with plenty of matrix math, and more oriented toward commercial activities.

    This book covers some detail design of composite structures, including how to attach metal fittings etc:
    https://www.caro-engineering.com/

    Scroll down to 'Composite Facts'. Sonja Englert has actually designed and built a motorglider, so she has some good practical advice and examples.

    If you're doing carbon fiber rod spars, Jim Marske's "Composite Design Manual" has a lot of calculations for that (http://www.marskeaircraft.com). Martin Hollmann's "Composite Aircraft Design" also has a chapter on design and analysis, although now out of print.

    The Zeke Smith Composite Construction books are good, with a few theory chapters, but don't cover detailed design at all. That's also true for most of the other amateur composite construction books I've come across.

    All of the above books state the same caveat: Perform strength tests on your own parts! That is the only way you can be sure exactly what load they will actually carry. That's a direct quote from the Composite Basics book, and the rest all make a roughly similar statement.

    To be honest, some of the threads on HBA from the experienced composite folks are some of the most detailed explanations of composite design I've come across. It will be interesting to see what else you turn up in this thread.
     
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  10. Sep 29, 2019 #10

    BBerson

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    I don't think the Rutan moldless method is in any design book. Designers I know generally copy from their experience of plans building a Vari-Eze. Then test for deflection. Usually extra layers are needed for deflection, not strength. (fiberglass)
    I don't think Rutan ever released any carbon aircraft plans to copy.
     
  11. Sep 29, 2019 #11

    pictsidhe

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    Extra weight is never a good thing and can indeed kill you. Extra structure that isn't needed will increase stresses on more marginal parts. If you can't do a proper stress analysis, you will have a weaker plane, not a stronger one with semi random 'strengthening'. Look at the Raptor. It wasn't designed with particularly high margins and is 1344lbs overweight. That is really going to eat into those margins.

    A design needs to be balanced to work well. Ideally, in an ultimate overload, the entire aircraft reaches failure point at the same instant and explodes into a cloud of dust. Nobody is that good a designer, but it is quite common for modern megabuck aircaft to have extensive damage when severely overloaded, not just one or two critical failure points. Less common on E-ABs as we just aren't that good or have tens or hundreds of thousands of engineer design hours to put in.
     
    Last edited: Sep 29, 2019
  12. Sep 29, 2019 #12

    Hephaestus

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    Not even getting started on the spruce raptor but yes I get your point.

    Pretty much why I wanted a book to hold my hand and walk me through (that and most of the RAF spec glass and resins are gone now) wouldn't mind the switch to carbon but that'll depend on other factors - that I don't even know yet I'm sure.

    @BBerson would it not largely be treating the moldless unit as plates with an averaging of the core? Or is that just too simplistic thinking? Like a wing - calculate the mean depth, plies above plies below. Averaged out it's a plate?
     
  13. Sep 29, 2019 #13

    stanislavz

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    You can always make a fuselage in a wing with carbon rods ways - ie calculate load on tail - calculate mean depth, calculate carbon rods for holding this load, and calculate skin for buckling only.. maybe some thin strips added. Ie, in a same way as metal stressed skin calculation.
     
  14. Sep 29, 2019 #14

    plncraze

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    Look up Marske Aircraft. He has what he refers to as a composite design manual.
     
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  15. Sep 29, 2019 #15

    BBerson

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    That's too broad a question. We can only comment about one thing at a time, such as skin, or spar, after seeing your construction type.
     
  16. Sep 29, 2019 #16

    stanislavz

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    Just read this book. It have nothing about fuselage, except wing attaching points to it.
     

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  17. Sep 29, 2019 #17

    stanislavz

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  18. Sep 30, 2019 #18

    proppastie

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    autoreply has talked about "black aluminum" many places. Where you design as for aluminum except substitute CF...resulting is as strong or stronger and lighter.

    The basics for all stress analysis still apply, beams, buckling....etc.....just have to figure the allowable for the CF, which is somewhat complicated as regards fiber orientation.
     
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  19. Sep 30, 2019 #19

    Hephaestus

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    Or am I going at this from the too old perspective?

    There's the FEA modules in fusion 360, that I have limited understanding of to date... I understand they sell the Helius composite package for the purpose of composite structure design, optimization and solving...

    Is that the better way these days? Get the model right, then let the software FEA/PFA work out the particular details?
     
  20. Sep 30, 2019 #20

    stanislavz

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    And if you do wrong, you can blame that bloody piece of software. All is ok, if you know how to use it..

    This text is quite interesting on composite design : https://apps.dtic.mil/dtic/tr/fulltext/u2/a232422.pdf
     
    Last edited: Sep 30, 2019

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