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Thread: Introducing a J-4 project

  1. #121
    skywagon8a's Avatar
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    Charlie, That is a powerful looking flap. Have you been able to check the airflow pattern on a FEA computer program? Just looking at it it looks as though you will need a leading edge slat to offset the nose down pitching moment.
    N1PA

  2. #122

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    No I have not been able to check it yet. Software is ready, drawing files are ready, I got some learning to do.
    I did draw up a cusped version of this airfoil and came to the conclusion I like what I have.
    It will be interesting to see what the pitching moment will be with this though. I expect operation may have a limited flap deployment till the speed drops down a bunch. I do have a good feeling I can meet my 5:1 speed ratio I design for.
    When I do get to running the airflow analysis I have a strong curiosity as to how slats affect cruse performance. Allot of learning to do still.

  3. #123
    skywagon8a's Avatar
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    I would think that the slats would have minimum drag if they were retractable or hinged in a manner which closes the gap on the upper leading edge.
    N1PA

  4. #124

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    I had slats drawn for the thinner wing last year. I have them designed so I can swap out all the mounting/hinge hardware to develop the proper location of the pivot so the slats close down nice when the AOA comes down.
    But my head is mixed with all I read that Mr Riblett hit the LE just right so the stall characteristics quite nice.
    My intention was to build slats for the outer 8' of the wing yet have provision for hinge mounts should I want to bring them further inboard. This would be more to make the plane very tough to spin in rather than striving for ultimate performance.

    Once I do get to doing the CFD on this wing I will have a few slat shapes drawn and see what I can learn.

    Either way the wing will more than likely be built with the provision for the slat brackets. These will be a slit in the LE that a piece of sheet metal slides into with one or two fasteners through it on the inside. Will require access on the underside but may not be out of line time and complexity wise. Said sheet metal would have the drilled position for the pivot point.
    This way slats can be added after the fact or the slits in the wing remain closed over.

  5. #125

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    The other aspect I meant to mention and where the CFD will play a part, is what effect does the slat play to the flow on the underside of the wing during cruise and how much does it matter? There is allot of disturbed contour under the leading edge.
    Retractable LE are more complex than I want to undertake, I need to fly this some day.

  6. #126
    skywagon8a's Avatar
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    Backcountry has a slat which I believe is hinged and closes the gap in the upper camber automatically as the speed increases. This is not a good picture but perhaps you can get the idea. http://www.supercub.com/options/leading-edge-slats/ It looks simple enough as long as you get the hinge point in the correct location. It is my opinion that the small gap behind the closed slat on the lower camber will not disturb the airflow enough for you to notice at all providing the cuff portion of the slat does not extend very far below the lower camber of the rib. Just as the gap ahead of the flaps has little or no effect in cruise.

    Cessna closed the gap ahead of the flap on the 206 to satisfy the marketing department. The test pilot told me that the speed increased by perhaps one knot. The stall speed also increased by the same amount.

    I used to fly an airplane (DC-9) which had the slats and the flaps operated by one handle. The slats would extend first requiring some pitch trim. Then when the flaps were extended to the first position you would need to return the trim to the original setting. In other words the pitch change requirements of the two canceled each other out. The large trailing edge flaps generated a nose heavy moment. The slats helped to reduce that moment. It was possible to "split" the flap handle in order to leave the slats retracted. When that was done there was a requirement to increase the landing speed by 25 knots. I tried this once. the stick shaker activated well before touch down. The 25 knots should have been a larger number.

    Basically what I'm saying is that it looks like your flaps will be so powerful in moving the center of lift aft that you will need either slats or an extremely powerful horizontal tail trimming surface to compensate.

    I like your idea. You should be able to get out and walk beside the plane before it lands.
    N1PA

  7. #127

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    I have also read reports of those slats and a few others not closing fully at cruise, something I would not tolerate and why I have designed my mounting as I have so they can be swapped out easily during development.

    The tail surfaces on my plane, both horizontal and vertical are airfoil shaped. Picture of the templates are in a recent post with all my recently CNC cut bits. The stab has 8° travel for trim, nominally 4 up and 4 down but we have no clue where neutral is till this flying. At this time I think the horizontal needs a bit more static lift such that I will be adding more camber to the lower surface inner rib profile. The outermost horizontal rib is close to symmetrical as is the elevator.

    Interesting bit with the DC9 lift devices. I am not sure just how the automatic action of the slats used on planes like the Cub would assist with trim with flap deployment since applying flaps when at a constant speed will lower the AOA which would close the slats.
    Since properly rigged slats deploy with increase of AOA I would expect large flaps such as I am building will greatly delay the opening of slats till rather low speeds.
    The slats would still be there for instances of say a moose turn if the flaps were not at least partially deployed which I expect this plane would need at least at higher loaded weights.

  8. #128
    skywagon8a's Avatar
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    Good point about not closing fully at cruise and not opening except at a high angle of attack. Perhaps a simple mechanical linkage tied to the flaps would be the answer? Or even a separate slat control for selective use?

    Once you are able to determine the amount of change in the center of lift with the flaps deployed you will have a better idea of the amount of trim authority that will be needed. My only concern is that you do not want to be able to run out of nose up trim capability combined with inadequate up elevator authority. The total tail down force must exceed the flap pitching moment authority.
    N1PA

  9. #129

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    I do not know if I will see any blanketing of the horizontal as well. I do not truly expect this but must investigate the possibility. With luck this maybe something the flow analysis will show.

    I have considered retracting slats mounted on tracks but truly do not want the time and complexity to build them. I will soon have a good CNC mill at hand which has been a limitation for me up till now machining complex curved or contoured parts. This resource might change my mind a bit.

    If the CFD session shows me a great value in slats it will open my mind some.

    I just measured my flap travel that I have since I was questioning the retracted position of the actuator arm, turns out when I was adding some last little parts I got the temporary links too short and the main flap is traveling 75° rather than the 80° I have designed. Time to pull a few rod ends out of the bin and make some proper links and get both flaps flipping.
    Those links are the only parts that were not simplified draws from the actual design. Interesting that both the long main flap link and the short fore flap link came out ¾" short.
    If that is the only mistake I find I will be plenty happy and is why I like to make these paper dolls.

  10. #130
    skywagon8a's Avatar
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    One thing which you could consider if you find that your pitch control is compromised is to increase the aspect ratio of the horizontal tail surfaces. Look at the Helio for example. Also be sure to use balanced elevators as this will reduce the control forces as well as giving more pitch control surface area.
    N1PA
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  11. #131

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    All the tail feathers are considerably larger in all dimensions. They utilize airfoil sections and a full 35° travel. The moving surfaces are balanced design as well as will be counterweighted.
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  12. #132
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    I just finished the annual on an H-295 Currier... The horizontal is a one piece surface hinged on two bearings with trim tabs... Same style as PA-28 Cherokee... the leading edge slats are two per side, air operated... They run on tubes that are interconnected inside the wing with a couple of bell-cranks and torque tubes... It also has roll spoilers forward of the outboard flaps just behind the slats... Flaps are push-pull tubes connected to ACME thread rods and operated by an overhead crank handle... Ailerons are short wide cord and fabric covered..

    It’s an interesting Aircraft with a lot of stuff going on... BUT, once you study the system it really is quite simple and elegantly done...

    Brian


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  13. #133

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    Thank you Brian.
    Are the slats interconnected side to side or just rely on the air for operation? Curious if they needed an interconnect for cert. I have worked on Pliatus Porters but not on Helios. Different animal and most important bit I did on the Porter was replace the lift strut brackets to comply and allow the plane to be ferried back to Switzerland for conversion to turbine.

    I have considered a flying tail but decided to stay more conventional. Early drawings had beefier hinges allowing me to convert.
    I have spoilers in the design, details are not finished on them.

  14. #134
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    Quote Originally Posted by CharlieN View Post
    Thank you Brian.
    Are the slats interconnected side to side or just rely on the air for operation?
    There is no interconnect.. they simply work on airspeed and attitude... if the airplane is still at the hanger next week I’ll try and get a couple pictures...

    Brian


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  15. #135
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    I have a little TigerMoth time and the slats just bang on and off independily to satisfy each wings need, or lock them is for a crispers break










    Glenn
    Last edited by cubdriver2; 03-26-2018 at 09:25 AM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  16. #136

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    Quote Originally Posted by Steve's Aircraft (Brian) View Post
    There is no interconnect.. they simply work on airspeed and attitude... if the airplane is still at the hanger next week I’ll try and get a couple pictures...

    Brian
    Sent from my iPhone using Tapatalk
    Brian
    Ahh. My mind mis-read "air operated" as being an internal pneumatic system rather than the standard free to move with the outside air. Seems to always try to over complicate things.

    Glenn, I expect I have worked on that Tiger Moth some 30+ years ago, wish I was better with names since he had an interesting collection at his airport at the time.
    Seems the cows from next door found the fabric on many of his planes tasty. The cure for the cows getting over to the runway to graze makes a great story for later.

  17. #137
    cubdriver2's Avatar
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    Quote Originally Posted by CharlieN View Post
    Brian
    Ahh. My mind mis-read "air operated" as being an internal pneumatic system rather than the standard free to move with the outside air. Seems to always try to over complicate things.

    Glenn, I expect I have worked on that Tiger Moth some 30+ years ago, wish I was better with names since he had an interesting collection at his airport at the time.
    Seems the cows from next door found the fabric on many of his planes tasty. The cure for the cows getting over to the runway to graze makes a great story for later.
    Which Moth? I've played with 5 in 3 different countries and 2 hemispheres Even got a ride in a Jackeroo once and sat in the only other one.

    Jerry Swahms, Bill Weiss?

    Glennj
    Last edited by cubdriver2; 03-26-2018 at 08:13 AM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  18. #138

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    Western CT, private grass strip, one of our elders whom passed many years back. Nether of those names. Damn I can remember many technical details about allot of things but not many names, never could remember names either.

  19. #139

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    I have a few pics from my phone when working on the router cutting out the templates that I have been finding to be very useful.
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  20. #140
    Steve's Aircraft (Brian)'s Avatar
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    Hellio Pictures... not the best off my IPhone



    Left wing slats... Tied back with a rope...



    Outboard slat deployed...



    Different view that shows it better..



    Inside the wing, the interconnect bell crank is between the ribs.. the torque tube is going to the right...



    Sat tube and rollers...The rubber part is a stop...



    Another view... the other bell crank in there is the wing flap bell crank and push pull tubes... The cable is for the aileron with an autopilot clamped to it.

    I took a short video of the system operating by do not know how to upload that through Tapatalk on my phone..

    Brian


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    Last edited by Steve's Aircraft (Brian); 03-26-2018 at 03:22 PM.
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  21. #141

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    Good info, I like the way those slats nest during flight giving no effect to cruise performance.

    The flap/ aileron system I intend to use is kind of interesting. I am as with a few of the planes I designed in the '80s will be using flaperons, this time with a twist. The ailerons will slide back on tracks 4" as a Fowler flap. Not doing to droop allot, 20° at this time but these look like they will offer a fair bit of performance gain with little added work or weight. There are roll spoilers in the design, details not finished yet.

    I am considering the section of upper wing skin aft of the spars and forward of the flaps might become hinged and utilized as a lift dump/ drag spoiler. Might be easier to build than a fixed skin in that area.

  22. #142
    Cub junkie's Avatar
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    Hope I don't drift your thread too much. My dad leased a Helio from 1967 to 1970. Our strip in Kansas was 60 miles from the factory in Pittsburg,KS. On our first demo the factory test pilot, Larry Montgomery filled up the airplane on our ramp and took off across the runway. He tossed the airplane into about a 75 degree left bank while climbing and those left slats made a very distinct pop as they extended abruptly. As he rolled out they started slowly retracting. That was my view as an 11 year old sitting in the porthole seat. Amazing aircraft. My dad used it to replace a Hughes 269.
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  23. #143

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    I have not ridden in a Helio nor seen one up close flown through it's paces. Read about them a bit. Now that I can machine more complex curved parts my mind is opening to the style of slat they run.
    Since I happen to be drawing the outlines to make my tooling to press form ribs, this is a good time to draw and make a few more parts.

  24. #144
    Steve's Aircraft (Brian)'s Avatar
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    I can see a similar setup utilizing full length Slats and having the torque tubes extended enough to mount a short bell crank that could be connected to the main flap system or set up to be operated individually... It could be made really light using carbon fiber components...

    Brian

  25. #145

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    I think I would want automatic operation to leave the pilot out of the equation as far as low speed flight errors should one be made.

  26. #146

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    Charlie, im not trying to interupt your thread, just a few years back i always found this video interesting.https://www.youtube.com/watch?v=H0YDyflDb-4
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  27. #147
    RVBottomly's Avatar
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    Quote Originally Posted by CharlieN View Post
    I got a little more done today, one important part that I neglected to get a shot of was to weld the square tubes that follow the top skin of the wing aft from the rear spar. this has the hard point for the flap torque arm in it and the location falls right in with where it is intended to be.
    From there I cleaned the edges on some more of my "paper dolls" this set allows me to swing the flaps though their full motion and I truly like what I see. I also set the upper longerons in place and can now mark the front of them for fitment to the forward fuselage.
    So here is a template showing the outline of the flaps in the full down position. Interesting thing I find is the trailing edge of the main flap is only 11" above the lower longeron.
    Attachment 35897 Attachment 35898
    I've been sidetracked lately by a surge of case assignments, so I'm behind on my following, but this stuff is really neat.

    I also have been staring at what looked to me like pterodactyl wing bones, imaging in my mind the radii of travel for those split flaps. I've been messing with something similar in cardboard, but I'll hide those hand-drawn cutouts for now. I'm impressed with your CAD/CNC setup. Light-years beyond what I can attempt.

    Still, I'm having difficulty seeing how everything pivots. Are the flap templates fixed at this point for showing the deployed position? Otherwise, I stumble at what look like fixed triangles.

    BTW, I followed your suggestion and located (and devoured) Albert and Doenhoff. Plus I found some other aerodynamics texts. I think I'm getting an empirical handle on the forces involved. I really appreciate the direction there.

    Quote Originally Posted by CharlieN View Post
    Software is ready, drawing files are ready, I got some learning to do.
    I did draw up a cusped version of this airfoil and came to the conclusion I like what I have.
    It will be interesting to see what the pitching moment will be with this though. I expect operation may have a limited flap deployment till the speed drops down a bunch. I do have a good feeling I can meet my 5:1 speed ratio I design for.
    When I do get to running the airflow analysis I have a strong curiosity as to how slats affect cruse performance. Allot of learning to do still.
    So that's got me wondering--software for airflow analysis? I'm barely conceptualizing the ballpark lift curves. I've yet to see good data for how the gaps between the split flaps influence airflow.

    So, I'm still watching your thread closely. It shows some real nice work and creative thinking.

  28. #148

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    The Bones,

    This is kind of like, here hold my coffee, lets get these bones moving
    What else does one get you wife to help you with an hour before sunrise. But this is what we make the paper dolls for.


    I probably should not have named this vid after the dinosaur since all the likes will be, well odd.
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  29. #149

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    I still find the Albert and Doenhoff book to have allot of information in it, sure wish all the information was explained better.

    For me I have allot of other documents dating back to collage courses as well as the documents from some very technical seminars at Oshkosh from the days people actually designed there own planes rather than assemble kits. It is hard trying to get a grasp on the technical side of aircraft when there has not been any fresh documents produced in 30 years and the few of us that still do this stuff forgot how we learned it, not to mention are just trying to get back what we used to know.
    I get the impression the few people willing to reach out and pioneer anything today have grey hair. We have done this in the past and for me I am stale and trying to get what I used to know back in my mind.
    I do have to say I like sending my drawings directly to a machine and parts get cut out. One of the hardest aspects from the past was getting accurate tools and templates. There are so many plans in print with pretty major errors as recently discussed with some of the ongoing builds on this forum.
    I was frustrated years back with scrapped parts such as foam cores for composite work due to templates being wrong. I am really looking forward to cutting some of the foam tooling I will be using in the Gerber router. Getting all the contours right from my drawings rather than trusting what a hotwire is doing in a block of foam, not to mention I will not be making all straight cuts for the molds I will be making. This should be interesting.

  30. #150

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    Fresh off the router,
    Late yesterday I did another session on the Gerber router. The first parts I made was a template for a Handley Page style LE slat as used on the Helio and a few other planes.
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    These will let me start understanding the fitment into my project.

    I also made tooling to build up the Dee window frames. These will be mounted to framework to hold the curvature on each side of the fuselage.
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    On the lower right of that shot are replacements for the flap system that I had entered the wrong lengths into the drawings for the original parts I made.

    From those parts made in Masonite I then changed over to 1" MDF and cut out the first tooling to press form the ribs for the wings.
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    There are two different nose rib tools for inboard ribs that will not have a slat in front of them and the clipped shape for the slatted area. This also provides the option if I decide for no slats or full length slats.
    next parts will be the tooling for building the elevators and rudder. This will be one tool routed in the MDF that will take the 3 different parts, one at a time. Due to complexity in this drawing setting the tool paths at different depths it would be best to redraw this tool.

  31. #151

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    Drats,

    Looking at the nose rib tools I had started to notice something not looking right last night. Turns out the tool path on the full rib was set wrong resulting in wall art.
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    I started to notice the error during cleanup last night but that was not the time to figure the issue out. The tool path can be selected for inside or outside a line and with a 1/4 cutting bit this makes quite a difference.
    At this time the router setup and operations are hosted by a new member of the EAA chapter I run, I am in training for this tool such that I am not "set free" yet. I might have caught this error had I sat down and reviewed the cut path before we hit the start button.
    Oh well, I sure prefer scrapping parts that all the time was in the drawing and not in the cutting and finishing of tooling as was done in years past. I do hope there is some room on the 4X8 sheet of OSB to fit new parts once the tailfeathers are ready to cut.

  32. #152

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    Here is the Handley & Page LE slat in place, well at least the paper doll concept of one.

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  33. #153

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    And two pics of the slat design.

    I want to than Brian of Steve's aircraft for spending allot of time with me describing details of how these slats are implemented in the Helio Courier.

    Click image for larger version. 

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    I will shoot more pics when the light condition is more favorable.
    With the slat in the deployed position you can see a pen line depicting where the LE of the wing will be.

    For a slat system I do like what I am seeing here.
    Last edited by CharlieN; 04-02-2018 at 07:56 PM.
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  34. #154

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    Can see allot better when the sun is not blinding through the window as it reflects off the snow.
    Clean wing shape.
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    All down,
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    And a clearer shot of the slat retracted,
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    And out,
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  35. #155

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    Last night we cut out the tool to build the elevators and rudder on. These are cut into 1" MDF as the other parts have been. Unfortunately one section turned out bad, these were a complex drawing with 3 separate drawings overlaid and combined. The cuts in the material were done in 3 different depths, shallow around the perimeter for the trailing edges, these routed well. There were a few through holes such as where the control horns will be. There a central groove where the 7/8 spar tube for each will be. This drawing had two open spots from the hours of editing when producing the drawing, we found them easy enough but there was one .032 overlap in the 73" tall drawing. The issue with this was the toolpath reverted to cut outside the lines which is easy to detect and indicates a drawing error, but went undetected before sending to the router. I am glad I was vacuuming up the swarth as the cut was proceeding and noticed the nearly 1½wide path for the 7/8 tube such this did not totally trash the tool. I took the time and found the tiny overlap and this time inspected the toolpath myself to make sure it was right. Other than needing shims to locate the spar in each part which might actually make the removal of the weldments easier, that could be a plus.

    Pictures and more later, the MDF is still on the rack on my truck in the garage since it was still snowing here on my drive home and now raining this morning. Dang that thick MDF is heavy.

  36. #156

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    Here are a few pics on the router,
    Click image for larger version. 

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    Finished cut in my storage building
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    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Likes Balsa, stknrddr liked this post

  37. #157

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    Following this build very cool.
    Thanks CharlieN thanked for this post

  38. #158

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    A few fresh screenshots with the slats installed and in the down position. I like them. I do have some clearance issues to work out near the lift strut area of the front spar since this it where the mixer is for the drooping ailerons. Everything will fit together fine but changes do need to be made. These images are with the outer wing extensions in place.

    Click image for larger version. 

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  39. #159
    Southern Aero's Avatar
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    Quote Originally Posted by Cub junkie View Post
    Hope I don't drift your thread too much. My dad leased a Helio from 1967 to 1970. Our strip in Kansas was 60 miles from the factory in Pittsburg,KS. On our first demo the factory test pilot, Larry Montgomery filled up the airplane on our ramp and took off across the runway. He tossed the airplane into about a 75 degree left bank while climbing and those left slats made a very distinct pop as they extended abruptly. As he rolled out they started slowly retracting. That was my view as an 11 year old sitting in the porthole seat. Amazing aircraft. My dad used it to replace a Hughes 269.

    I may have met up with you or your folks way back then, met quite a few. I was working with John Roberts..... Helio Distributor out of Spartanburg/Cross Anchor SC. We made trips back and forth to Pittsburg KS when he was trying to get Helio going again back in the late 70s early 80s. I flew with Larry some, never did get the full checkout. Larry actually lived about a half mile from me. I used to cover Helio ailerons for him. Ended up leasing John Roberts' airport for several years after he died.
    ......... It doesn't cost any more to go first class! You just can't stay as long.

  40. #160

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    Over the past month I have been doing more drawing and calculating, the main subject has been LE slats. I am going with them, the Handly Page style that is. Most recently I have been working out if the slats will be supported on formed tubing as the Helio is or whether I will machine the supports. At this time I think I will use machined supports. Being I need 12 supports in all it is more effective to just draw the parts, basically done at this time, then just lump a hunk of aluminum on the mill and let it make them.
    Much less time for me than running stainless tube through the rollers to hit the 22¼" arc, mill the holes for fasteners. weld in the bushes and ream them.
    The aluminum billet parts will be an I beam in cross section with varying thickness of the flanges as needed where the peak loads will be.
    Metal chips might fly in later May to make the "kit"
    Last edited by CharlieN; 04-27-2018 at 12:19 PM.
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