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Thread: Therapy Project

  1. #121
    RVBottomly's Avatar
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    Quote Originally Posted by Cub junkie View Post
    You planning on the "H" or "X" brace in the bay in front of the tail post?
    I'm still trying to figure out what the differences are. I'll use one of them, probably. X intuitively seems better, but I need to read up on them more.

    Another place that looks like it could use bracing is at the stabilizer attachment on the upper longeron. It sits mid span. I've seen references to the longeron being bent there.

  2. #122
    Cub junkie's Avatar
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    I like the X. Easy to do.
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  3. #123

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    I would build the X simply because it is structurally better.
    And I would brace the stab mount area as well, does not need much, maybe a 5/8x.028 or .035 on each side.
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  4. #124
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    Up for air after a couple of weeks. I reached something of a milestone, now having the main fuselage mostly tacked together. There are still a few tubes to put in, but the shape is there. It measures square and pretty close to the numbers on the drawing.

    I weighed the assembly using a moment arm technique I worked up for boat building. No pictures, but the basic idea is to find the center of balance, and then put a fulcrum 10 inches one way or the other from the center of balance. Then go to the up end and add weights at a certain distance. Then calculate the moments. I did it both ends and came up with 54.4 pounds each way.

    Seeing it was pretty light, I hung it from a rafter and weighed it with a fish scale. It came out to 54.7 with that method, but that included the ropes tied to the frame to hang it from.



    Then I rolled the jig table outside.





    The main point to all this moving was to get the assembly lower for work on the superstructure. I hope to build a rotisserie from scraps in the near future.
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  5. #125
    Lowrider
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    Looks like progress to me!!

    I used 2 V-8 engine stands for the fuselage turn around thingy and they worked really well for welding and painting...just a thought.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!
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  6. #126
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    Quote Originally Posted by Lowrider View Post
    Looks like progress to me!!

    I used 2 V-8 engine stands for the fuselage turn around thingy and they worked really well for welding and painting...just a thought.
    I've seen something like that, but I don't have any engine stands.

    But what I do have is an extra 22' piece of 7/8" tubing. Seems like that would make fairly decent axle spit with some homemade bushings from leftover 1" tubing.

  7. #127

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    The rotisserie is easy enough to make from wood. A dolly for the base, say 2X3', a braced vertical 2X4 tall enough to allow full swing of the finished structure. At the firewall, it is nice if the pivot point can be changed as the balance of the structure changes such that a piece of plywood bolted to the engine mounts might be right, but just a board across the upper two and the lower two engine mount point with a vertical board with the pivot points drilled in.
    Tail post end can be hose clamped to a bit of angle that has the pivot tube welded to it.

    An issue with most engine stands is their pivot tubes are not level to the ground, they are always twisting about when spinning the structure. This does not allow for stability which is our safety. There is no way I want something to start rolling over when I am half inside the structure leaning on it as I weld.

    I do have a heavy duty rotisserie that I built decades ago for building cars and boats, this is a recent BMW build on the spit.
    IMG_9786.JPG

    And a different one getting the interior painted last summer,
    IMG_0639.JPG

    Rolling a ton of car is a one man task when balanced right and a 100# fuselage can be safe and simple.
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  8. #128
    Cub junkie's Avatar
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    I use ho' made U joints at each end. I was going to use old car U joints but they are bulky and usually greasy. I made up a couple of U joints from floor sweepings. You can cobble anything in framework to work off old saw horses etc. or some type of similar stands. The Harbor Freight cheap auto engine stands with the ubiquitous 20% off coupon are affordable and I never feel guilty chopping on HF stuff, it usually needs it anyway.
    Attached Images Attached Images

  9. #129
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    Wow, three weeks since last update. That's mainly because I had little to show. But I spent a fair amount of time with a tape measure, plumb bob, homemade trammels, etc., tracking down annoying discrepancies.

    I was working on the superstructure and I had the hardest time getting things square. I built a scaffold and measured everything against the datum line. Tacked up some tubes in a perfect square (according to the template), only to find it out of square when I mounted it on the scaffold.

    Heh. CharleyN and Marty said there'd be days like this. I had about 6 (partial) of them--tacking and then going back and grinding away tacks--measuring, fitting, rejecting, re-profiling, clamping, measuring, etc. On and on. Finally it came together. The only way I could really line things up was to fasten a swiveling wire on the tail post and measure everything from there.

    So, finally a step forward:





    It's still pleasant therapy for me, despite the back-eddies. My great plans at freeing more time got derailed by a bunch of new cases assigned to me. On the upside, it looks like I'll hit my court-mandated limit in August instead of next January. Maybe that will free up some time.
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  10. #130

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    I am happy I bench made my cabin top since it is square. I have since welded too it and it has yet to move and with the X brace it may well have some pent up loads in it but it remains accurate.
    With it being square this reduces your workload when getting it in place on the rest of the fuselage.
    Basically you are not trying to keep it square as well as level and lined up all at the same time.

  11. #131
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    Another installment. I need to add up my hours in my handwritten log.

    I opted for simplicity regarding a rotisserie. A couple of 2X4s clamping the front tubes with bolts, and a 1/2 carriage bolt running through a 1X4 triangle.

    The tail region rests on a fairly sturdy platform. I can rotate the fuselage easily by lifting the tail section and twisting. Because of a notch in the rear platform, I have 8 positions of rotation without even trying.

    I still need a few more tubes tacked in, but today I was rotating, checking, and refitting a few joints that didn't line up well on my first go. At least the shape still seems straight.






    But, of course, life has other draws, too. There was the call of fishing on the Snake River to attend to as well:


  12. #132
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    2 weeks go by and you'd think nothing happened. And, as far as apparent progress goes, you'd be right.

    But a lot of wheel spinning went on.

    I decided to really check every dimension one last time before starting the finish welds. I leveled up the horizontal reference line and started trying to level the fuselage on its long axis. I was alarmed to find the next to last aft station was not level with all the other points. Plus, the tail post was off from vertical by a degree.

    I thought about denial. What's a degree here or there? So what if the center of the next to last station is off by 1/4"?

    So the therapy project opened up a new line of inquiry: what kind of builder do I plan to be? A night passed, and then out came the grinder, homemade clamps, triple-checking of connections, and spatial visualization near the edge of my capacity. I also laid out and leveled some 4X4s on the uneven concrete shop floor for reference points. In the end, now I can say that every tacked joint and station is plumb and straight. The wing attach points are on spec within 1/32" (which is as good as I can read on my tape measure).

    And I'm back to where I thought I was 2 weeks ago. I also finally added up my shop time on the log: 133 hours since mid November 2017. I hope I can step up the pace this summer.
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  13. #133
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    Good for you. Do the very best that you can or in the end you will not be satisfied. I once had a carpenter doing some work for me who had an expression which he kept repeating "Good enough for this shack". Well as you may expect, that was the quality of his work. Certainly nowhere near aircraft tolerances. If you don't strive to do the best, you will never achieve the objective.
    N1PA
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  14. #134

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    Quality Control is the most important part when striving to achieve good quality. One Rutan designed plane I built with a partner back in the early 80s had a larger pile of scrap foam and glass than what is in the finished plane. In the end the quality was superb but getting there was wasteful.
    A few days ago the treasurer for my chapter was over, he commented on all the incomplete weld joints on my plane, hard to explain why it is way too early to finish weld the joints. But as you found, one does not want to weld everything too early.
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  15. #135
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    I haven't posted much here lately, because the picture doesn't obviously change. But still plugging away at welding the frame.

    I straightened some slight twists that showed up.



    When the boat was still out after a July 4 fishing trip, I got a better view of the fuselage:



    And the whole point of a major project is to have an excuse to buy tools. I ordered a modest 750 pound mill drill.
    The freight company promised me a week's notice. So I got a call today just before some hearings that the guy would be in town at 3PM. We arranged drop off at a local depot and I picked it up there.

    I wasn't ready for it, but improvised with a sturdy work bench, some pipes, and a come-a-long:







    So now I have another diversion, but I'm looking forward to what this RF-30 knockoff can do.
    Last edited by RVBottomly; 07-11-2018 at 07:10 AM. Reason: corrected typo
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  16. #136

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    That should be a handy tool.

  17. #137
    www.SkupTech.com mike mcs repair's Avatar
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    I like that All thread push tool. Will have to remember that. Would be good for taking on ferry jobs.


    Sent from my iPhone using SuperCub.Org

  18. #138
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    Quote Originally Posted by mike mcs repair View Post
    I like that All thread push tool. Will have to remember that. Would be good for taking on ferry jobs.

    Yeah. It took more time finding a couple of washers than it did putting it together. I've got 1/2 inch and 3/8 inch models.

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