Building Update

Discussion in 'New Member Introductions' started by pylon500, Aug 14, 2005.

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  1. Aug 14, 2005 #1

    pylon500

    pylon500

    pylon500

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    Hi Guys, I'll post here as we don't have a 'What we're building' area.
    I've just uploaded a stack of photos of my LR-2 construction to a YaHoO photo site.
    Go to;Building the LR-2
    I'll try to keep this updated when possible. :rolleyes:
    Just too many things to do, buy land, build new house, build new hangar :ban:
    Arthur.
     
  2. Aug 15, 2005 #2

    HeliDev

    HeliDev

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    Hey Mate, that looks awsome!!!!
    How long did it take to get to that stage of the build?
     
  3. Aug 15, 2005 #3

    pylon500

    pylon500

    pylon500

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    Would you believe two and a half years? :(
    Got a few more shots to put up, but still a long way to go.:wail:
    Arthur.
     
  4. Aug 15, 2005 #4

    Shrimphead

    Shrimphead

    Shrimphead

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    wings

    in the pictures, it seems to show you cutting your wing cores out of the foam by yourself. Is that an easy process? Could you explain how you did it?
     
  5. Aug 16, 2005 #5

    pylon500

    pylon500

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    OK, Busted. :p:
    when you read all the books, they say you need to mark each end profile (whether parrallel or tapered), and then using two people, count your way around the cut.
    Even though I didn't have a lot of previous experience with foam cutting, I figured I'd just eyeball it, and basically it worked.
    Yes, I did get a bit of scolloping around the leading edges, about a quarter inch across a four foot block, but as this is only to make a 'plug', i just had to use a bit more filler.
    If I was building a LongEze or similar, no this would not be acceptable. :rolleyes:
    As an overall process, counting your way around a block is probably only half the 'trick', other considerations are; ambient temperature, cutting power, frame stiffness, wire sag or tension and sometimes the quality of the foam itself!
    I ended up with about four different size cutting frames, each with it's best power needs written on it.
    I have learnt all sorts of unexpected problems in the build so far like;
    I opted to use Epoxy to glass the styrofoam instead of trying to seal it so as to use polyester.
    I then found that laying thin white glass on white styrofoam with clear epoxy, it was real hard to see where I'd whet out and where I'd missed, so I started adding a couple of drops of printer refill ink to the epoxy (mainly black, but sometimes colour) hence the odd colours of the plug.
    I then used MicroBalloon in polyester as a filling medium, which seemed to be working well until someone told me the poly doesn't like to stick to epoxy? :confused:
    After that big lumps would just fall off now and then. :mad:
    Funny what you can do if you don't know that it can't be done!! :gig:
    Another thing I learned, someone told me you could buy 'talc' in big bags for much less than the cost of Microballoon to use as a filler if weight was not a problem (it's a plug remember) what they didn't tell me was that the day after it's cured, it's like CONCRETE!
    It's OK if you are working full time on assorted bits so that, half an hour after the poly and talc has cured, you can start hand shaping it with 80 grit sticks.
    But lay up something one night during the week, then come back on the weekend and try to sand it, and you need a Jack Hammer!! :eek:
    Till next time,
    Arthur.
     
  6. Aug 16, 2005 #6

    orion

    orion

    orion

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    For future reference, as Pylon discovered MEKP catalyzed polyester resin based filler will not stick to epoxy (or anything else that's not polyester based for that matter). However, we know that fillers such as Bondo, Ultra-Light Filler, etc. will stick to many surfaces, even the epoxy. The difference is the catalyst. Commercial fillers are catalyzed with a BPO paste - if you therefore modify your polyester resin by adding a bit of the correct promoter, you will be able to catalyze with the paste as with the commercial products and thus get the home-made polyester based filler to stick, even to the epoxy.

    Polyester and Vinylester resins are promoted with two compounds. One is a very deep blue liquid that is generally refered to as CoNap or Cobalt. The other is DMA (Dimethylaniline), which is a clear liquid that has probably the worst smell you've ever come across (and is classified as a rather serious poison - so handle carefully). For the resin that I use, it takes a bit more DMA promoter in the mix to allow the resin to be catalyzed with the BPO paste. The amount of the DMA promoter should be measured carefully, preferrably in larger batches (5-gallons at a time or more) since the numbers we're talking about are very small fractions of a percent.

    To get the necessary formulations, it is best to get a promoting and catalyzing schedule from your distributor, since each resin will have slightly different requirements.

    To stick to the epoxy, it would be beneficial to use peel-ply on the last layer of the laminate so that the surface is prepped and ready for the filler (after you take the peel-ply off of course). If you don't use peel-ply, then you'll have to sand the epoxy surface a bit to aid the adhesion. Depending on application, and if the laminate is not structural, it is sometimes best to sand far enough down to just barely expose the fibers of the underlying laminate fabric. Then the polyester has something physical to hold onto, above and beyond just the basic molecular attachment achieved in chemical bonding.
     
  7. Aug 16, 2005 #7

    dustind

    dustind

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    I love the airplane pylon500.

    How do you make your canopies? What do you use to determine the hole size in your oven, and how do you get the canopies to fit the right way when you are done?
     
  8. Aug 18, 2005 #8

    pylon500

    pylon500

    pylon500

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    Canopies 101?

    OK, working on the principle that most things have been done before, you generally find that you don't invent something, rather, adapt to your need.
    I may have mentioned that I once worked for a company that built Sadler Vampires under lisence in Australia. :rolleyes:
    Some parts where sent to us from the US, including the canopy bubbles.
    These were made from polycarbonate (tinted) and simply blown as a dome.
    Being flexible even after blowing, we would just wrap the bubble around the frame to make a canopy.
    Recently a club member built himself a nice little all composite, single seat, low wing tail dragger (shades of the AR-5) and had most of the structure formed when he decided to make his canopy.
    This put him in the position of having to make the canopy suit the shape of the fuselarge, which required the use of a shaped 'contact' mould (ie a male plug) covered with a soft material, over which he had to drape and pull a piece of semi- molten acrylic perspex.
    This required a high temp oven, half a dozen people, three attempt pieces, and a lot of cut and polishing afterwards.
    My idea is to leave the openning area of the cockpit until I can produce a consistent shaped bubble, then mould a canopy frame to suit it. :roll:
    My box/oven is actually sized to suit some timber I already had, the circle cutout was as big as I could make it, and I formed my first bubble (the shallow one).
    To make my bubbles fit, I just pull them in on the sides, this tends to straighten the top curve, so the next one I blew (sucked actually :whistle: ) I made deeper.
    This gave a nice profile, but the sides tended to stick out, not so noticable at the front, but fairly prominent at the back, so I cut a new top that is more tear dropped at the back (you can see the removed piece leaning against the shed).
    As with all aircraft design, you have an idea, then compromise your way to the finished article
    The materials available to make canopies are basically; Perspex, Lexan and now P.E.T (the stuff coke bottles are made from)
    Each has it's pros and cons, but I'm opting for the PET for it's ease of moulding, low cost, fuel resistance and reasonable optics.
    Arthur.
     
  9. Aug 18, 2005 #9

    StRaNgEdAyS

    StRaNgEdAyS

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    It's looking nice Arthur!
    :D
     
  10. Jun 24, 2008 #10

    pylon500

    pylon500

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    Hi Guy's n Gal's,
    Hey it's been a while but I've finally made all the move and now have a new house with a HANGAR that opens to a grass strip and a sealed strip at the far end. :ban:
    I've kept a photo diary and uploaded the lot to My Picasa Website.
    The LR-2 is back under way and I'm hoping for around Christmas? :roll:
    Arthur.

    ps, 6 months in a caravan, then another two months in the house, all without the internet. :speechles
     
  11. Jun 24, 2008 #11

    rtfm

    rtfm

    rtfm

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    Pylon,
    Hi. Your web site (well, photo album) is an inspiration. I have been looking for something like this for a long time. I am building a two-seater and have been worrying for ages now about many of the things you show in the gallery. For the first time I now have some idea about how to proceed.

    I'm in the very early stages of building my plug. It is a lot harder to do than one might imagine. But slowly does it...

    Thanks for sharing your building experience with us.

    Regards,
    Duncan
    (Auckland, NZ)
     
  12. Jun 24, 2008 #12

    Mac790

    Mac790

    Mac790

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    Actually it isn't so hard if you first design it in your pc with proper software but without it that can be painful, I agree with you. I've built in my life about 10-15 plugs and molds for my car. I was "using old school method" and I said myself no more, first design and after that build otherwise it's waste of time and health from stress (because left side is slightly bigger then right side, personally when I see difference like 2-3mm on big part between sides I'm going mad).
    I did short sample for other page some time ago "how to design molds from 2D drawings".

    You can check it here.
    http://www.canardzone.com/forum/showpost.php?p=18537&postcount=166
     
    Last edited: Jun 24, 2008
  13. Jun 25, 2008 #13

    rtfm

    rtfm

    rtfm

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    Hi,
    I followed your link, but it seems you did it all on CAD. I can't do this. I have 2-D drawings of the profile and the top view. Other than that, nothing. My problem is (currently) how to translate these 2-D drawings into 3-D reality.

    I have read and re-read Raymer's explanations about lofting, and I have to confess it is WAY beyond me. I just wish there were some magical way to take the two views I have and to press a button and get the computer to magically have all the bulkheads (eg every 100mm) printed out. Wouldn't THAT be great. As it is, I have tried (unsuccessfully) on six previous occasions to do this my eye. All ended in failure. I'm now on attempt #7, and it is heavy and slow going. I look at Pylon500's photos, and your CAD screens and drool. I could be FLYING already if I could just get past this hurdle... :)

    Talk about the long haul...

    Regards,
    Duncan
     
    Last edited: Jun 25, 2008
  14. Jun 25, 2008 #14

    orion

    orion

    orion

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    One possible source of good drafting technique that you might gain is from basic mechanical drawing or architectural design texts. Before I did anything in CAD I was a designer/engineer/draftsman, working the old fashioned way: Ink on Mylar. I've attached one of the early projects I did for Litton Industries (it never turned to hardware due to changing budgetary priorities) - in the upper right hand corner are several cross sections generated in order to show certain volumetric details. Sorry about the bad trim job - I don't know if I have the original on this computer or not.

    But a basic text in mechanical drafting should be able to show and teach you how to generate and calculate cross sectional shapes, even of more complex shapes like airplane bodies, blends, etc.
     

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  15. Jun 26, 2008 #15

    pylon500

    pylon500

    pylon500

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    Orion's going to hate me for this but, when I started to make the fuselage plug, I was actually just playing around with the sheet styrene making a rough profile to get an idea of real size from the scale drawings I had.

    With the profile standing on the bench I then thought, 'How egg shaped would the bulkhead at the back of the cockpit be?', so I grabbed another bit of foam and roughed out a shape and stuck it on with hot glue.:gig:
    Profile.

    One thing led to another and by the end of the night I had most of the profiles in place, no sections were ever drawn to or from a PLAN !:shock:
    Picture 2.

    This gave me a lot of latitude to change shapes as I could see them developing.
    The only complexity that came from this was the fact that all the profiles were to the outer shape, but instead of trying to figure out how much to cut off the profiles for the external sheeting, I just glued blocks in between the profiles leaving enough to trim off.
    The whole fuselage plug was shaped by eye. ;)
    Shaping.

    When it got to complex shapes like wing fillets, I just layered the area with 'Expanda-foam', and carved away....
    Fillets.

    I should point out that I've had a fair bit to do in the drafting and drawing world before getting into computers, but, I still can't drive the 3-D section of the cad package I use, VectorWorks (I'm on a Mac), and probably only use 20% of the 2-D sections capabilities, so fear not.
    Just start carving!

    One of these days I must actually try to measure the fuselage, then go back and amend the computer version of the shapes.
    Arthur.
     
  16. Jun 26, 2008 #16

    orion

    orion

    orion

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    There's nothing wrong in your approach - it's just that for some people doing things by trial and error, little cut here, little cut there, can become somewhat of a chore in that the process may become something akin to a bad haircut. And if that works for you, great! But having things drawn out, complete with cross sections, will give you a good overview of what you have and what you're still missing, without making a mess.
     

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