The Razorback construction thread

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by rtfm, Jul 11, 2008.

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  1. Dec 20, 2008 #61

    AVI

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    Thanks, Seb - My Russian is very, very rusty, but you are correct - it is a glass/balsa sandwich Berkut, like the original.
     
  2. Dec 20, 2008 #62
  3. Dec 20, 2008 #63

    Mac790

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    Balsa? where is that info coming from?
    Here is a Richard Riley (he was a member of Berkut Engineering) replay for my question about Berkut layup schedule.
    Canard Zone - View Single Post - Berkut Kit

    Sorry wrong guess. I use them from time to time for example this one PROMT - Free Online Translator and dictionary - English, German, French, Spanish, Italian, Portuguese (Brazilian) and Russian languages.
    In my opinion much better than mentioned by you babelfish and google.

    Seb
     
  4. Dec 20, 2008 #64

    AVI

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    Thanks, George.
    I used Babelfish for the Me-109 factory drawings and it did the job, but I've got to tell you, a literal translation of aviation terminology does not always work. I don't suppose I've been the only one to experience a lot of headscratching in using Bablefish as a translator for original German WW2 factory drawings.

    Hey, besides, the military spent a lot of money sending me to language school .....
     
  5. Dec 21, 2008 #65

    gschuld

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    Duncan,

    [​IMG]

    I sincerely applaud your enthusiasm, but I have to admit that I am a bit concerned. Perhaps I am missing something. Would you mind explaining the construction process you intend to use. I saw your latest pictures and I'm not entirely sure how this is supposed to work out. My background is in custom wooden boat building, including a good bit of work with strip plank over mold methods.

    Here's the thing. If you use a strip(foam core strips in your case) over mold method, you would normally need to glass over the strips, then remove it from the mold, and glass the inside. To glass over the core material, the core needs to be secured to the mold in such a way that the foam will be seemlessly bonded together and absolutely rigid in the correct intended shape. Your strips, as they show in the pictures, are "free floating" so to speak. I don't understand how you intend to either fair or glass the outer surface.

    I'd like to help here, but getting an accurate picture of what your construction methods are would be a good start.

    George
     
    Last edited: Dec 21, 2008
  6. Dec 21, 2008 #66

    rtfm

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    G'day George,
    First, thanks for the post. You are absolutely right as far as the method is concerned. Unfortunately, the pictures I have posted are of the very initial stages, and do not really indicate clearly how it will evolve.

    In short, when I have covered the entire structure with "free floating" foam planks, I will begin ensuring a close fit against the templates, and will then be bonding them together using two-pot foam. At that stage, I will be shaping the foam to its final shape. I will then be securing the foam hard against the templates with 1-inch glassfibre tape laterally. By the end, all foam plankes should be securely bonded to each other, fully shaped and tightly pressed against the templates.

    At that stage it should all look like some of the other pictures Seb has posted. I can then glass the outside, remove it from the templates and vacuum bag the inside etc.

    Within a day or two I hope to complete the initial planking (which is little more than simply cutting the foam planks to shape). Photos at that stage should reveal the full picture.

    Till then
    Duncan
     
  7. Dec 21, 2008 #67

    AVI

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    Duncan
    Wouldn't it be better to cut/shape, align and attach each individual plank not only to the frame/buck but to the plank next to it as you progress along either the top or bottom of the frame? That way, the foam would be ready for a layer of glass when you've completed the planking.
    I don't see how you can accurately shape/attach the foam when it's free-standing, the way you presently have it.
     
  8. Dec 21, 2008 #68

    Mac790

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    If we are talking about wooden strip planks, I thought someone might be interested.
    YouTube - How It's Made (Season 6 / Episode 11 / Part 2)
    YouTube - Canoe Building, Part II
    I've worked only with hand wet layup, mostly polyester resin, some epoxy and some vinylester (Derakane 470-300), but didn't have to use vacuum bags, so my question is, is it possible to vacuum bag part which isn't "supported" by a mold? I'm afraid that vacuum pressure will bend/damage unsuported structure, even if it has a glass layer on the one side. Can someone (with more experience) explain this to me?
    I was exactly talking about it, but unfortunately my "English" is sometimes hard to understand, sorry about it.

    Seb

    btw Duncan if you have any question or doubts please ask, we are all one big family so I'm sure someone will help you to find answer.
     
    Last edited: Dec 21, 2008
  9. Dec 21, 2008 #69

    AVI

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  10. Dec 21, 2008 #70

    rtfm

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    Laying the foam planks

    Hi guys,
    First, thank you for your interest, and for taking the time to contribute to this discussion. It really does make it seem like this is a joint venture.

    However, I don't share your concerns over whether or not I
    In the end it doesn't matter. Your way would be "neater" while mine is a bit messy. But as soon as I apply the foam "glue" the results will be identical. And one benefit of placing all the planks "loose" like I'm doing is that at the point where I am ready to cement them all together, I can make sure that all the lines are smooth, that there are no anomalies and that generally speaking everything lines up perfectly. Committing oneself to each plank does allow the possibility of making an error early on which has to be revisited.

    In any case, I'll be past this initial phase in a few days.

    I am, however, uncertain about how to do the tail. I am currently considering building the tail out of solid blue foam and attaching it to the final bulkhead. Then I will fair the tail into the rear fuse. Problem is, the fuse will be 1/2" foam, and the tail will be solid foam. Shaping (and glassing) the outside will be easy, but what do I do on the inside?

    And do I shape the tail/rudder in its entirety, and then cut the rudder section off before I glass it? Or do I glass the entire tail/rudder, and cut the rudder section off afterwards?

    Regards,
    Duncan
     
  11. Dec 21, 2008 #71

    AVI

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    Re: Laying the foam planks

     
  12. Dec 21, 2008 #72

    Topaz

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    Re: Laying the foam planks

    Hi Duncan,

    I've been away for several months, but it's great to see you here and making so much progress on your design.

    I guess I'm a little confused. When last I was here, you were going to mock up the airplane so you could get a better idea of what you were working with - much like the aerospace manufacturers used to do.

    Is that what you're doing now? What you're describing sounds awfully 'final', but some very basic aspects (such as the vertical tail/rudder construction you're describing above) don't seem to be worked out yet, especially if this is a final 'real' structure.
     
  13. Dec 21, 2008 #73

    rtfm

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    Re: Laying the foam planks

    Thanks Topaz. Yes, it is pretty exsciting.

    Yes, this is the actual plane. And yes, some basic aspects of how to physically construct it are evolving as I build it. If I were to wait till I had answered all my own questions, I would never get this plane built. So I am proceding with caution, making decisions as I go. Not that I have no idea of where I'm headed. I have a number of plans in the hangar from which I am gleaning ideas on how to put this lot together. It is more a question of which ones do I choose, and which methods seem most appropriate for my purposes.

    This sort of approach makes some folk nervous, I can see - but I'm asking and getting good answers to my questions both from this forum and from local builders when I need them, and I'm comfortable with how this is progressing. Nothing I'm doing is new - it has all been done a hundred times before. It is just a matter of choosing which build options to use.

    Regards,
    Duncan
     
  14. Dec 21, 2008 #74

    Topaz

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    Re: Laying the foam planks

    Well, congrats then on getting into the build. I'm so looking forward to that time, myself! :gig:

    Just please tell me that you've actually sized your structure with some sort of analysis to determine that it will take the loads your actual design will put upon it. Did I just miss that work in the last few months that I was gone?
     
    Last edited: Dec 21, 2008
  15. Dec 21, 2008 #75

    gschuld

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    Duncan,

    Again, I am very impressed with your positive attitude and determination to build the plane of your dreams. But pal, this is worrying me. I will not pretend to be the most experienced person out there regarding the construction of foam core composite structures, but I do have plenty of professional hands on experience. I would, for example, be much less concerned if you were building a boat. If it does not work out, something goes wrong, you can swim. Not too much to loose. But we're talking about sitting in a craft built totally by your own hands, zooming to 10,000ft or more above the earth. If anything significant goes wrong up there...
    What you are doing is extremely ambitious, to say the least. Designing an entire plane from scratch, designing the entire construction process from scratch(as you go), with very little experience with either process is a tough combination.

    It's big picture time. I'm curious as to what inspires you to design and build an airplane.
    -Is it because you want to fly and find building your own plane to be the most economically viable means to that end?
    -Are you most interested in building the most cost effective plane that you can to satisfy your preferred performance in the air?
    -Are you designing your own plane because there is nothing else out there that suits you?
    -Are you designing a plane because you want to find an easier way to build a plane?
    -Would you build an existing plane design if it fit into your desired end result.
    -Are you dsigning and building simply because you enjoy the challenge of the project?

    What I'm getting at is why design from scratch if you can build something that is a already proven both in design and construction? Take a KR-2s for example:

    [​IMG]

    Not a bad looking plane if done well and has nearly identical function and purpose as your resulting design. The design is well proven, and has shown time and again to be easily constructed by the fairly inexperienced. And it is very affordable. The Sonex, in aluminum, is in the same category.

    You appear to be reinventing the wheel in every aspect of your project. Is this really necessary? Hope this does not come off the wrong way, I am really trying to be constructive.

    George
     
  16. Dec 21, 2008 #76

    rtfm

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    Re: Laying the foam planks

    Hi Topaz,
    Yes, I have sized my structures. I've completed the spars, wing skins and fuse. I have not yet done the landing gear, engine mount or all-flying horisontal tail attachment. Nor the fowler flap geometry. But I figure it is going to take me a long long while before I get to the point where I will need to have these numbers. If I wait till I have everything sorted, I'll never begin. What I have already is going to keep me going for well over a year, I think.

    Regards,
    Duncan
     
  17. Dec 21, 2008 #77

    rtfm

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    Hi,
    Basically for two reasons. One: I couldn't find anything which actually suited me. Two: I enjoy the challenge of the project

    I have a full set of Sonex plans, KR2 plans and Polliwagen plans. Between the three of them, I have all the drawings I need for the internal bits (linkages, controls, etc). All three sets of plans detail construction techniques, and even though the materials are different, there are tons of tips and ideas of how to put basic componentry together.

    As I mentioned to Topaz, I've calculated the stresses for the spars, wing skins and the fuse itself. I'm still working on the rest. But I figure I have plenty of time to complete the rest of the calculations - and in the meantime, I can progress the parts I have already completed the analyses for.

    Cheers,
    Duncan
     
  18. Dec 21, 2008 #78

    Topaz

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    Re: Laying the foam planks

    Okay, thanks for clearing that up for me. You know how it's been here sometimes - when I was here before we'd occasionally get someone who just thought that they could 'eyeball' it all, and they can't be talked out of it.

    I didn't think you were one of those since you've been great about asking questions on things that you don't know, but I'd missed everything where you were talking about structures. All of a sudden you're building and wondering how to put certain parts together. I was concerned that maybe you'd become impatient and had started building before you were really ready.

    Is there a post or thread somewhere that you show the new configuration of the airplane? Last I was here, it was still a parasol wing, I believe, although you may have already gotten away from the idea of doing a Controlwing-like system. Looking at your avatar, it seems that much has changed.

    (EDIT: Never mind. I just went to your profile and saw the photo album there. Mighty sexy little beast you've got there, Duncan! If she flies as good as she looks, you'll definitely have a winner!)
     
    Last edited: Dec 21, 2008
  19. Dec 21, 2008 #79

    PTAirco

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    For those of us designing our own, there is a simple answer as to "why?" Because we want to. For most homebuiders their 'mission requirements' can easily be met by existing designs, whether kit or plans built. Whatever purpose you have in mind, there is a design out there that will probably fulfill that purpose.

    To my mind, building somebody else's design was never even a consideration. I never deluded myself into thinking I can do something significantly better than another designer - in fact there are so few ways of making anything in aviation significantly better that almost any homebuilt desing is a case of re-inventing the wheel. But it will be MY wheel!

    It is also a way of tailoring your structure and materials and methods to something you are personally comfortable with, and to try out new ones.

    And I have to echo Duncan's sentiment that if you wait until you have every last nut and bolt accounted for and drawings for every single item in the airplane - you will never get started. But I would not dream of cutting metal/wood/plastic until the basic structure has been finalized and a basic stress analysis done. And even then you will need to have a pretty good idea of how the details fit into all that all that or you will end up with a mess of ad-hoc modifications. And Duncan, even if this attempt ends up scrapped, youwill have learned something. My friend David made three plugs and five mold halves before he was happy with the final result, but he is flying his very own design airplane now.
     
  20. Dec 21, 2008 #80

    Mac790

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    So true when I was building my car (attachment) I made 3 nosecones, 2 or 3 bonnets, 2 rears and 2 extra doors, before I was happy with the result. I didnt use paint it's gelcoat (besides front "wings" made of carbon), that's why I was unhappy. It probably cost me more than kit price:gig:, But I gained EXPERIENCE (nobody can't take it away from me, it's mine), which is priceless. We are all human, we make mistakes it's normal, but it's important to learn from mistakes. Other way it's pointless.

    Seb
     

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