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Thread: Therapy Project

  1. #401
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    Quote Originally Posted by CharlieN View Post



    Do NOT try to drill these, it might work but probably will not.

    Plastic bushings for high loads should be snug, low loads can be loose.
    Thanks Charlie. How about drilling out pillow blocks from blocks of delrin? Is it a heat issue?

    I see blocks available on ebay.

    I weighed things and it turns out the assembly above weighs 5 ounces more than if I simply use two parallel and offset torque tubes for the pedals. That works on Cessnas, my Skyranger, and I think on several RV designs. Simpler with less hazard of rust on moving parts. I think I'll use delrin pillow blocks to hold them in place. Just not sure if I want to machine them or find something premade.

  2. #402

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    Parallel tubes in Delrin is a superb way to do it. The Delrin can be drilled although an end mill or reamer will provide a nicer final cut.
    You might consider split blocks for the Delrin. This offers a way to adjust the bore a bit should that matter. You can however aim for a near zero bore clearance but consideration needs to be considered for long term corrosion control.

    Here is another option, turn an insert for the ends of the tubes that will fit inside a ball bearing. The center of the tubes can be supported in a HDPE or Delrin split block.

    The end bearing supports can be plastic or aluminum. Image for reference, these support my pedal mixer since I am utilizing full adjustable pedals on each side.

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    I am having a hard time finding some images, problem with not being in this file for awhile due to another project consuming my attention recently.
    Regards, Charlie
    Super Coupe E-AB build in process
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  3. #403
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    Quote Originally Posted by CharlieN View Post
    Parallel tubes in Delrin is a superb way to do it. The Delrin can be drilled although an end mill or reamer will provide a nicer final cut.
    You might consider split blocks for the Delrin. This offers a way to adjust the bore a bit should that matter. You can however aim for a near zero bore clearance but consideration needs to be considered for long term corrosion control.
    Thanks. I was planning on split blocks and I have a nice set of end mills. I like the option of adjusting the bore with shims if necessary.
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  4. #404
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    Been a while and I'm lazy when it comes to updates. But things have progressed.

    I went the parallel rudder tube approach with Delrin pillow blocks. I ordered a block of Delrin online to see what I could do.

    For the pedal assembly I cut little blocks from what I ordered, cut them in half and bolted them together. Then I put 3/4" holes right where they split. The first few I did with a 3/4" end mill. Then I ended up swapping out mill collet for the drill chuck to drill something. Then I wondered, "maybe a spade bit would work."

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    Yup. At 120 rpm it worked fine. Delrin is pretty neat stuff.

    I had a bunch of shavings, of course.

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    I wondered about flammability with it laying around. Grinding sparks and all.

    So, a diversion.... lightweight delrin firestarter:



    At least it works on wet tumbleweeds.

    FWIW, I swept up and vacuumed all the delrin shavings to keep me from starting fires in the shop.

    Then I went to the pillow blocks for the 1.5" torque tube, using my cheapo expanded mini-lathe. (16" bed instead of 10")

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    I'm pretty sure I need steel reinforcing of some kind. Maybe a top plate with the edges bent down? The torque tube pillow blocks specified are aluminum.

    I didn't show the rudder bar assembly being welded up, or the torque tube fabrication. It was tedious but not bad. Here is a draft layout in the fuselage:

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    Then it was back to welding on the torque tube. I was contemplating all sorts of alternatives, but ended up with going as drawn. I can spend three times as much time second-guessing myself as it would take to build something. For this I decided to go with what has been done before.

    Torque tube welding:

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    Gussets were added but I don't see pictures

    Control arm bushing holes drilled (step drills seem to drill round)

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    Then tabs put on control stick stubs

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    Put it together held with welding rod to see how it fits:

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    The sticks go back and forth with no interference on the connection rod. So far so good. Still have to weld the elevator arm.

  5. #405
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    Float fittings etc.

    So another month goes by. The new normal is not really normalized, but things plod along.

    I finished up the control stick torque tube assembly. Long ago I was thinking of simplifying it to one center stick. I got talked out of it and went with the drawing.

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    Suffice it to say it is a heavy assembly. Combined with the stick attachments, it is around 3 pounds.

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    I also welded on tabs everywhere for the floor and other attachment points. No pictures, not really difficult work, but tedious bending and twisting of my stiff body.

    Then I decided to fabricate float fittings from the Northland plans. They are stout. .090 material for the flat square, .10 for the lugs, and .125 for the tabs.

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    The fittings are heavy. 13.5-14 ounces each--not counting the milled insert that I don't have material for right now.

    But they look like the Atlee Dodge or Univair ones, and cost me some $20 in materials. I didn't count the gas I needed to get decent penetration, though. It was hot welding them. For some reason I don't have a picture of the final result, but they look like they will make very strong gussets if nothing else.

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    The angle of the tab concerned me a little, because the fuselage is wider than a super cub fuselage at this point. I sort of adjusted for that based on what I could find on line. In the end I decided that, if necessary, I could adjust them with heat.

    This was an interesting diversion. I can see why the big-name suppliers charge $500-700 for weld on fittings.

  6. #406
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    Looking for ideas: door frames

    So I shifted gears and started bending sheet metal for the door frames. I finally figured out how to do the backward bends with the things I have, but then the gnawing started....

    The plans say to weld these channels every so many inches. Right.... Weld onto bare 4130 tubing things that will collect water and dust.

    I looked at various threads on rust developing from window and door channels. Predictable results, apparently.

    I'd like to be able to put a good coat of paint on these tubes before covering them up with door frames. So far I have played with various options, including laminated douglas fir, milled plastic strips, aluminum over foam tape. All of the ideas include the notion that they could be removable for inspection without having to grind weld points.

    Before I go off the deep end, has anyone seen something like this that I could adopt/adapt?

  7. #407

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    As if by now I am not known to do things differently. My doors close against the round tube. I am not a believer in needing the added structure for the door to close against.
    I will simply let the fuselage fabric wrap the tube with it's doubled tape as normal. I intend to then apply a strip of durable polymer tape as a wear protection to reduce damage from entry and egress.
    My doors are a rectangular frame with a flange that when closed will cover, call it half the tube. Within the rectangle tube and flange will be a ¼ Rd foam seal such that it's round face will seal to the round frame tube.
    This all will be durable and has no long cavities to try and protect over the decades from the elements.
    Regards, Charlie
    Super Coupe E-AB build in process
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  8. #408
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    Quote Originally Posted by CharlieN View Post
    As if by now I am not known to do things differently. My doors close against the round tube. I am not a believer in needing the added structure for the door to close against.
    I will simply let the fuselage fabric wrap the tube with it's doubled tape as normal. I intend to then apply a strip of durable polymer tape as a wear protection to reduce damage from entry and egress.
    My doors are a rectangular frame with a flange that when closed will cover, call it half the tube. Within the rectangle tube and flange will be a ¼ Rd foam seal such that it's round face will seal to the round frame tube.
    This all will be durable and has no long cavities to try and protect over the decades from the elements.
    I like the idea. As you described this I thought about my Commonwealth doors. They overlap from the outside with a rubber seal. Simple. I don't know why I didn't consider that approach given I was just fiddling with the door latches yesterday.

    But the Commonwealth has a partial channel. I looked at the drawings I had and it specified "zinc chromate tape" between the channels and tubes. That's a new one on me.

  9. #409
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    I use weldable primer on the Super Cub u-channel in front of the D window and on the door channels on the Short Wings. Piper didn't do anything and it shows 50-75 years later. It splatters and spits as you weld over it but it has to help. I have thought about sealing between the stitch welds with that body sealant they use on car bodies now but haven't tried it.
    Steve Pierce

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  10. #410
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    How about filling the channel with linseed oil, paralketone or ??????????? Then draining the excess out the bottom through a drain hole.
    N1PA

  11. #411
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    Quote Originally Posted by skywagon8a View Post
    How about filling the channel with linseed oil, paralketone or ??????????? Then draining the excess out the bottom through a drain hole.
    I think that would be a nightmare. We had a fuselage someone filled with oil and it kept weeping out. Most people fill with oil, let it drain out and weld up the filler hole. I can't imagine trying to cover that, I would be afraid it would ooze out throughout the covering/painting process.
    Steve Pierce

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    Check out what Bob Barrows did on the Patrol I believe it was. He too was tired of the bare metal rust issue under door frames etc.
    He planned it out and welded tabs as required to the door frame areas, added nut plates or clip on nuts I suppose AFTER the fuselage was primed and painted. Nowhere left to not get a primer and paint protective coating. Then they bent up the door frames out of aluminum and attached them to the tabs possibly even after the fabric was in place. Lighter, plenty strong, no rust. Sounds like a win win to me. Enough so that’s what my plan is for my build, and that’s where I am in the sequence. Do some work on the tail post and then do the door frames. That will finish my fuselage and ready for final blast and paint.


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  13. #413
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    Quote Originally Posted by OzAK View Post
    Check out what Bob Barrows did on the Patrol I believe it was. He too was tired of the bare metal rust issue under door frames etc.
    He planned it out and welded tabs as required to the door frame areas, added nut plates or clip on nuts I suppose AFTER the fuselage was primed and painted. Nowhere left to not get a primer and paint protective coating. Then they bent up the door frames out of aluminum and attached them to the tabs possibly even after the fabric was in place. Lighter, plenty strong, no rust. Sounds like a win win to me. Enough so that’s what my plan is for my build, and that’s where I am in the sequence. Do some work on the tail post and then do the door frames. That will finish my fuselage and ready for final blast and paint.


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    Thanks for that. I hadn't looked at Bearhawk.

    But this morning I looked closely at my Commonwealth SkyRanger. It does almost the same thing that you describe. Painted tabs on a painted frame; aluminum trim/frames over it that can easily be removed.

    But I'm still kicking around Charlie's minimalist idea, too.

  14. #414
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    I have done like Steve in the past with the weldable primers. On the door frame sheet metal I use a Rotabroach to put in a series of access (lightening?) holes half way between the tubing and the outside edge of all the formed sheet metal .......... there are other brands that are the same difference ........... This allows access to the interior portion of the frames. The holes are about 1 1/4" down to 5/8 or 1/2. If you have sand blasted the fuselage, make sure to get all the sand out. Tape up the holes and skip welds with most any kind of tape but leave a place to tape in a tube to pour in your favorite primer. Roll it around to ensure total coverage then drain into a pan for reuse of what's left. It can be somewhat messy but it gives you the warm and fuzzy knowing SB819 will never be an issue for that airframe.
    ......... It doesn't cost any more to go first class! You just can't stay as long.
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  15. #415
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    June Update

    I left off at the end of April having fabricated float attach brackets. I didn't have the drive to actually gather thoughts for an update until now. Things plug along in a haphazard fashion.

    I tacked on the float attach fittings. Later I welded them more securely.

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    Then I went about making rudder pedals.

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    They are pretty basic. I had all sorts of "improvements" in mind, but given my current circumstances, I've decided to pretty much follow the plans and not get derailed.

    But following the plans requires creativity, nonetheless.

    I'm still kicking around how to attach the channels under the cockpit. The drawings are vague at best. They show "channels" and mention that they should be "radiused." No specs. No pictures. You can figure offsets by looking at other measurements, but, as near as I can tell, it is sort of an improv adventure.

    My first improv:

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    I've studied pictures of various fuselages online so I think I have the gist of it, but I'm going to fall back on my boatbuilding hit and miss fairing before I weld the things on.

    I also re-did the jack-stand for the stabilizers. I don't know how these things happen, but I discovered after 8 months that the screw would run into a cross-brace. Glad I just tacked it last Fall. Rudder still lines up well, at least.

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    Part of my life these past months has been devoted to winding up my day job. I'm pretty much a stay-at-home fellow now. Which means no cash flow, so the frugality regime kicks in. I had an Acme screw from my old lathe that I didn't need when I extended the bed. It has 16 TPI square threads. I'm thinking it might do well for the jack screw. I turned it down on the shaft to fit, but I'm still weighing the pros and cons.

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    A side project was to see if I could make aluminum pulleys. Apparently I can:


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    I am thinking about increasing the bore and using some of my left over delrin for bushings. If nothing else, it is fun to try.
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  16. #416
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    I made aluminum pulleys and pressed in rollerblade ball bearings from VXB.com. They seem to work well.
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  17. #417
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    Quote Originally Posted by jimboflying View Post
    I made aluminum pulleys and pressed in rollerblade ball bearings from VXB.com. They seem to work well.
    I like that!
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  18. #418
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    Quote Originally Posted by RVBottomly View Post
    I tacked on the float attach fittings. Later I welded them more securely.

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    Do you have a particular make and model of floats in mind? I ask because the flat tab wire pull which you have "hard" welded MUST align with the cross wires when they are tightened. This angle varies from float model to float model. When these tabs are "fixed" as yours are, it is usually because the angle has been calculated for a particular float. You may need to bend this tab while installing whatever model floats you use.

    An alternative welded on fitting would resemble the fitting you have for the strut attachment. This would create a flexible cross wire fitting for a natural self aligning connection.

    These fittings are normally supplied by the float manufacturers for a particular installation. Unless you are duplicating the angles for this particular model of float on this particular model of airplane you may or may not have the correct angle.

    I agree with Jimbo, use a ball bearing in your pulleys. They make for nice smooth low resistance controls which absorb the extra friction caused by tightening the cables to a proper tension.
    N1PA

  19. #419
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    Quote Originally Posted by skywagon8a View Post
    Do you have a particular make and model of floats in mind? I ask because the flat tab wire pull which you have "hard" welded MUST align with the cross wires when they are tightened. This angle varies from float model to float model. When these tabs are "fixed" as yours are, it is usually because the angle has been calculated for a particular float. You may need to bend this tab while installing whatever model floats you use.

    An alternative welded on fitting would resemble the fitting you have for the strut attachment. This would create a flexible cross wire fitting for a natural self aligning connection.

    These fittings are normally supplied by the float manufacturers for a particular installation. Unless you are duplicating the angles for this particular model of float on this particular model of airplane you may or may not have the correct.
    Montana Floats Series 2200 amphibious . It may never happen, but that’s the target.


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  20. #420
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    Quote Originally Posted by RVBottomly View Post
    Montana Floats Series 2200 amphibious . It may never happen, but that’s the target.
    In that case, you may be wise to inquire of Montana as to what that angle should be. Now would be the time to make any corrections if needed, since you are not yet covered.

    Perhaps Jimboflying could help with those angles as his airplane is on those floats? Your installation would be similar.
    N1PA

  21. #421
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    That could be helpful. I took a drawing of the floats and did some basic trig to set the angle, but double checking doesn’t hurt.

    BTW, it was from one of your comments on a different thread that made me look for the measurements.


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  22. #422

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    Quote Originally Posted by jimboflying View Post
    I made aluminum pulleys and pressed in rollerblade ball bearings from VXB.com. They seem to work well.
    Same. 608 bearings work great:

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  23. #423
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    Bottom Channels

    This was sort of tedious and the drawings were little help. The drawings showed "channel" under the fuselage in the front cockpit area. It also said, "radius all channels" with little arrows. No reference as to how much. I'm guessing that when the plans were drafted this sort of question was part of the common knowledge base for your typical scratch builder.

    BTW, no dimensions were given for the channel, either. But based on what I could discern from a photo on the Wag Aero website, it looks like standard 3/8 channel.

    I'll mention something that has bothered me about the Wag Aero plans from the start. In most places, the plans follow what I call the "propagation of error" method. That is, they show measurements from some other joint or intersection instead of from a datum reference.

    No big deal if you mark out your own references--extra work and double checking, though. When I did that, sometimes the dimensions did not add up, so you end up choosing what looks right.

    So the channel locations followed the same format, except some measurements were left out. I got the feeling that it was more of an eyeball the thing and make it work sort of process.

    Oh, and the fuselage profile showing the channels did not match the dimensions for the fuselage layout. I spent a few hours looking at various pictures of 2+2 Sportsmen and saw that there were subtle variations with how the boot cowl was shaped. I decided to try to avoid the bulge I saw on some of them, double checking for clearance of the elevator arm on the torque tube.

    Once I got into it, though, it was not so hard. I used battens and stiff paper to make sure that there was a conical projection from the firewall template, and did the same for the middle set of arches. Tedious, but I have it all tacked.

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    I did not have a metal shrinker or formers, so I used the needle-nosed plier approach to bend the curves. Once it was all tacked and braced, they seemed plenty rigid.

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    For kicks I unrolled some aluminum flashing to see sort of how it looked.

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    The plans, as far as I can tell, are silent on how to fasten the lower cowling. I think nutplates? I saw someone mention a clever way to seat them with epoxy instead of rivets. One picture showed them pop-riveted....More things to figure out.
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  24. #424

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    Screws into the channel has been done as well
    Regards, Charlie
    Super Coupe E-AB build in process
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  25. #425
    RVBottomly's Avatar
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    Quote Originally Posted by CharlieN View Post
    Screws into the channel has been done as well
    Of course, LOL! I'm showing how little experience I have at these things.

    Just a few months ago I put back in a bunch of screws in my Commonwealth. You'd think that would have told me something.

  26. #426

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    My opinion they would tell you to weld on tabs and use nut plates of some form that will remain durable long after we no longer care.
    If time and cost were a concern the PK screws are the way.
    Regards, Charlie
    Super Coupe E-AB build in process
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  27. #427
    wireweinie's Avatar
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    PKs are a horrible way to go. The screws chew up the channel and wallow out the holes until the channel cracks and breaks. I've seen many aircraft with nutplates riveted into the channel but that means three holes for each screw instead of one. Some have said that they used adhesive to hold the nutplates in. My trick for these is to use 1/4" square nuts for #6 screws. These will just fit inside of the channel. Glue them into the channel with pro-seal so that you can dig them out if needed. Then you can attach the boot cowl or panels with #6 machines crews with nylon washers.

    Web
    Life's tough . . . wear a cup.

  28. #428
    RaisedByWolves's Avatar
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    Nut plates during the rebuild and use the original sheet metal hole as the middle


    Sent from my iPhone using Tapatalk
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  29. #429
    RVBottomly's Avatar
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    Quote Originally Posted by wireweinie View Post
    My trick for these is to use 1/4" square nuts for #6 screws. These will just fit inside of the channel. Glue them into the channel with pro-seal so that you can dig them out if needed. Then you can attach the boot cowl or panels with #6 machines crews with nylon washers.

    Web
    Thanks for that! I'd been kicking around some sort of homemade nut plate idea--this is right what I was looking for. I even have a little box full of those nuts and I always wondered if I'd ever use them.

  30. #430
    RVBottomly's Avatar
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    Pressing on, kind of slow, but I wanted to pop up to show I'm not totally derailed. Lots of life things accumulate and slow down progress. Plus, my four herniated discs in my back decided to flare up again, so I stagger around the shop and sit a lot and think. Or so I say....

    But I did have to ponder things because I am working on the bird cage and stringers. The plans are pretty vague, at least to me. As I mentioned before, the plans showing channel work don't match the profile of the tube structure. I decided to quit trying to figure it out and go for flow.

    First, I used some clear fir for bottom stringers. Had to scarf them.

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    Welded more tabs and discovered that 102F in the shop is not so bad after our 118F heat wave.

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    Side stringers (just a mock-up--I'll use better wood eventually)

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    Then I cobbled together a channel-bender because everyone else has one. It is homely and clunky, but worked pretty well for the channels above the cockpit.

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    You put it into a vise and fine tune the bend angle with a large set of channel-locks. Then push/pull the channel through. It doesn't take much to make too much of a bend. This shot was using scrap:

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    Looking at the photo I see the washer could bind, but I didn't notice when I used it. Some improvement can be made there. And the tube/bushing on the right really ought to be another roller, but I was out of stock. It did the job.

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    For some reason I don't have pictures, but I set the curve using wing ribs aligned on the wing attachment points and then tried to account for plexiglass width. Now I just need to add cross members and additional bracing.

    I'm at a decision point whether to go with a swept-back curve like the PA-18A design or to go as designed. I put up the arches as designed, but I sort of like the ag profile better. More things to sit and think about.
    Last edited by RVBottomly; 08-09-2021 at 11:57 PM. Reason: typo
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  31. #431
    Southern Aero's Avatar
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    I try to do everything that's practical to stay away from PK or any sheet metal screw...... I even tap my spars for 4-40 rib mounting screws so as to not use the PKs. I found these "weld nuts" years ago and have been using them ever since. Inexpensive alternative to use in secondary structures.............. You can spot weld them in, form flanges or trim and bond like in Piper Channel that we all use. The square nuts DO work well too in the Piper Channel and have used them a lot before finding the weld nuts. I think I have them in #4 thru #10. They have them in several shapes too like for corners, but they are a little thicker like the ones on the left of the box.

    Good to hear from you again Vic

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    ......... It doesn't cost any more to go first class! You just can't stay as long.
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  32. #432
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    Fun with pulleys

    I'm never going to make it as a content provider. I'm too slow these days.

    But I've been working on where to attach pulleys for control cables.

    Others may have no issues with this, but I have to confess the Wag Aero plans were very sparse on details for pulley location. Basically a line drawing showing the rough location of cables. No specs on pulley size, although they do provide pulley bracket details.

    But I just couldn't get the pulley brackets, as designed, to line up well with the center of the torque tube.

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    Note, the pulleys shown are too small, I changed that. I also tried flipping the brackets the other way, but that resulted in interference with upper frame tubes.

    While I was messing with this, I researched pulleys and aircraft cable. That was a mistake (not really, just an eye opener).

    1/8 inch, 7X19, cable, of course, is specified. As I read more, I discovered that the minimum recommended pulley size, for aircraft application, for this cable is 5 inches! I ran across lots of charts and ponderous references supporting that.

    Well, that threw me a bit. Plus, some folks recommend using coated cable if you go with aluminum pulleys.

    Hmm. That didn't seem right, especially in the world of cub-like aircraft.

    So I decided to look at my Commonwealth to see what they did. 2" aluminum pulley at the wing root and from the torque tube. Best I could tell, the cub drawings have 1 3/4" pulleys. I decided to make some 2" pulleys and press on.

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    I'll clean them up and bore them for ball bearings sometime later.

    Finally, after trial, error, fiddling with various temporary brackets to hold in place, I think I have located where they go. By the way, the plans call for a fairlead near the door, but that bend is more than 13 degrees. I put a pulley there too.

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    For me, the critical thing was to have the cable aligned in planes for each pulley, that is, making sure the cable enters and leaves each pulley square to the axle. It took a lot of fiddling and tongue holding, but I think the other side will go quicker. They are tacked in place for now, waiting for final welding once I finish the other wing.

  33. #433
    skywagon8a's Avatar
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    Quote Originally Posted by RVBottomly View Post
    1/8 inch, 7X19, cable, of course, is specified. As I read more, I discovered that the minimum recommended pulley size, for aircraft application, for this cable is 5 inches! I ran across lots of charts and ponderous references supporting that.
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    This one "looks" to be a bit small. High load near the control stick turning nearly 90 degrees. The cable may tend to fray/break individual wires due to bending. Larger pully diameters minimize the concentration of the bending loads on each individual wire.

    I'm reminded of the pulley next to the rudder pedals on a Taylorcraft. They are very small, the cable turns nearly 90 degrees and they wear out quickly.
    N1PA

  34. #434
    RVBottomly's Avatar
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    Quote Originally Posted by skywagon8a View Post
    This one "looks" to be a bit small. High load near the control stick turning nearly 90 degrees. The cable may tend to fray/break individual wires due to bending. Larger pully diameters minimize the concentration of the bending loads on each individual wire.

    I'm reminded of the pulley next to the rudder pedals on a Taylorcraft. They are very small, the cable turns nearly 90 degrees and they wear out quickly.
    I was thinking the same thing. Piper has an 80421 pulley, which is 1 3/4" phenolic. The Backcountry build manual shows the same size in aluminum. Mine is 2".

    I could probably fit a 3" pulley there.
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  35. #435

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    I would pay attention to pulley size and amount of wrap. More bend or heavier load I run larger diameter pulleys.
    Regards, Charlie
    Super Coupe E-AB build in process
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