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Thread: Lowrider LSA

  1. #1841

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    Sky,

    That makes sense to lap over top. I was going to check the RV site and refresh my memory but 43.13 is a better source for sure. I did the RV wing set between 2 post standing up and not flat on a table...seems like a better way from an ease of access standpoint. I'm having some issues getting square with no twist. Once I get things right I will put the bottom skin on. I'm using a laser level so it is easy to get it set up but clamping in place is not simple.

    I'll follow 43.13 for laps. Dimpling a 48" sheet is a bear.

    Average Feb snow is 8.7" in La Nina years and we have 41" so far. Come on Spring!!
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  2. #1842
    skywagon8a's Avatar
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    Wing Skins

    Low,
    Are you buying prebent skins or bending your own?

    There are two very important things for you to keep in mind when assembling the wings. Make absolutely certain that the twist in each wing is exactly the same.
    The other is that the leading edge radius is correct for the airfoil and is accurate on all of the skins. AND that it is the same on both wings.

    A trick. After the leading edge radius is formed accurately, form a slight curve in the opposite direction (away from the wing rib curve) in the remainder of the sheet. This will force the skin to sit tight against the rib when you drill and fasten it, thus eliminating puckers between the rivets. Work from the leading edge aft.

    IF both leading edges are not exactly the same and to the proper airfoil contour, the performance will not be what you expect. It could be better or more likely it could be worse. One wing may fall off in a stall or the other wing may drop first. It may have a benign stall or it may be abrupt and scary. I flew many different versions of the same model production airplane with a tapered wing. Some of them would stall to the left, some would stall to the right. Some were superb low speed short takeoff performers, others were outright dogs. It was later learned that the cause was a production error. The radius of the leading edge varied from wing to wing. Once the manufacturer started verifying the leading edge with special tooling, the irregularities disappeared.

    Dimple with light taps of the rivet gun after all holes are drilled. Not a big deal.
    N1PA
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  3. #1843

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    Bending my own. I understand the need for matching wings and will do my best to make it so.

    Last sentence...does that mean "dimple with the rivet"...never done that. I'll practice on some scrap. Is there a trick?
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  4. #1844
    skywagon8a's Avatar
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    No not dimple with a rivet. That's possible but tedious and can get away from you. A tool such as these:
    http://www.aircraft-tool.com/shop/search.aspx
    I have the top round one. You also need a dimple/die set for each size rivet which you expect to use. These dimple/dies also fit in a hand squeezer. It just takes a light tap to accomplish the mission. Don't over do it.

    Make sure that the rivet gun is held perpendicular to the skin in order to prevent smiley faces. Practice on scrap.
    Last edited by skywagon8a; 02-08-2017 at 12:51 PM.
    N1PA

  5. #1845

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    Your link didn't work but I think I have what you're talking about. A heavy round thing with the female die that goes under the sheet and a smaller one that takes the male die. Whack the small one and it sets the dimple. I also have the long arm one that is table mounted but won't reach more than maybe 18".
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  6. #1846
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    N1PA
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  7. #1847

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    Yes Sir...same ones I have. They work well but are slow and they must be exactly perpendicular to the sheet for good results. Thanks for reminding me!!
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  8. #1848
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    You will be very pleased with yourself after you have finished.
    N1PA
    Thanks Lowrider thanked for this post

  9. #1849

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    Alright, frustration set in today with trying to set up my wing on the table. If I get the front spar right the there is a twist somewhere and I can't find it....I give up after hours of fooling with it. I took off for Home Depot (with a not so quick stop for fried indian bread, a bowl of clam chowder and giant (1lb) pastrami on fried sour dough sandwich) and picked up two 4x4x8', six 2x4x8' and piece of 1 1/2" PVC to suck down the nose bends. I'm going to stand up the wing between the 4x's and plumb and square it so I can get the damn thing correct. I used this method for my RV 4 wings and they turned out just fine. After all, how hard can a straight wing be to skin anyway! I think by using the 3 direction at once laser level it should be pretty much a simple process setting it up properly and locking it in place. We'll see...suggestions?
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  10. #1850

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    I got my frame work up to suspend the wing. It's cross braced and very solid. just waiting for a couple little things to get done before hang the wing. Ihave painting to do on steel parts before I start skinning.

    I did use the "vacuum bend" method to get the nose bend done on the first piece of skin. It worked great and I learned that my 5 hp shop vac is just a little too much suck for this method. It took about 12 nano seconds for it to go from the "looped" skin to the skin hugging the 1.5" PVC tightly. My first thought was oooops, I ruined the skin but when I removed all the tape and plastic and the PVC the 0.025 2024T3 sprang back to an appropriate bend and no indication of being any worse for the experience. I have a 1.5hp vacuum that I'll try on the next piece...the big one scared me! Just a word to the wise.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  11. #1851

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    I have my tank straps primed and ready for paint. I planned to use anti-chafe tape between the straps and the tank but what I have is 1" and the straps are 1" and I wanted an overlap on the straps so it they shifted in turbulence or another reason the edge of the strap would not be in contact with the aluminum tank. I suppose most anything that would isolate the strap like inner tube rubber would suffice. Anybody have any ideas?
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  12. #1852
    skywagon8a's Avatar
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    Glue the anti-chafe tape on the straps not the tank.
    Last edited by skywagon8a; 02-19-2017 at 06:52 AM.
    N1PA

  13. #1853

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    Another option would be Aircraft Spruce #05-01800 neoprene channel designed for that.
    Practicing open cockpit extremism

  14. #1854

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    Sky,

    That was the plan but I am concerned that the edge of the strap could rub on the tank.

    Marcus,

    That looks like a better solution than the cloth tape. I searched ACS but I think I was looking for anti-chafe and didn't see the rubber strap material...gotta be specific on searches! Thanks!
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  15. #1855
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    I just used a strip of thin felt glued to the straps. It won't move and it's unlikely that there will be movement between the tank and straps. Emphasis on unlikely, not impossible.
    N1PA

  16. #1856

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    Maybe I'm over thinking this again, but I was interested in having a soft "skid proof" material between the tank and the straps. That's why I was thinking inner tube rubber or something similar. I would have thought felt would wear thru quickly, but I guess if the tank can't move it won't matter so much.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  17. #1857

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    We got the wing hung on the posts and it is Straight, square and plumb and the whole thing is rock solid. I'll start tomorrow to get the first piece of skin set up and ready to start drilling holes. I'm going to use the same straps that I used on my RV-4 wings and see how that works out. The wing contour is way different but it should work with a little tweaking or whatever it takes. Feels really good to get to this point if only with one wing...it's progress...now we'll see if I can buck rivets.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  18. #1858

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    Today's progress:

    wing hung 005.jpg
    Now, to take it apart and dimple. I did get assistance from my wife...she cleco'd and I drilled...went much faster but it didn't come without a price...lunch tomorrow at Mick Duffs...oh well...they have the best calamari in town!


    wing hung 005.jpg
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  19. #1859
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    Looking good Low, Do you have a mushroom rivet set? http://www.cleavelandtool.com/1-Mush.../#.WK7L3tJViko
    You should use one for your flush rivets on the skins. Some of the rivets on the nose ribs look as though you used too much pressure with the set in relation to the rib. There are some dimples around the rivets. Look at the second and fourth nose ribs outboard of the leading edge skin. You don't want this on your nice smooth skins.
    N1PA

  20. #1860

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    Thanks Sky!

    There are no rivets in there yet. It may be some clecos I put in from the back that makes it look that way. That's 0.025 2024-T3 and it is hard to make that nose rib bend even with it pre-bent with the vacuum. The rest of the skin will be 0.020 so it should be a little easier but also easier to put "smiles" on the skin.

    I do have a mushroom set with the rubber around the edges. I'm planning to back-rivet in those areas where I can. I made a 2" round brass bucking bar that works really well for that. It gets beat up some but I just put it in the lathe and "freshen it up" a bit.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  21. #1861
    skywagon8a's Avatar
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    Quote Originally Posted by Lowrider View Post
    Quote Originally Posted by Lowrider View Post
    Thanks Sky!

    There are no rivets in there yet.

    I do have a mushroom set with the rubber around the edges. I'm planning to back-rivet in those areas where I can. I made a 2" round brass bucking bar that works really well for that. It gets beat up some but I just put it in the lathe and "freshen it up" a bit.
    Look outboard of the skin which is clecoed in place. Count outboard to the 2nd and 4th exposed nose ribs. From here it appears that the rivets which are holding the vertical stiffeners are dimpled. This is from not holding the angle stiffener while driving the rivets. If you held the bucking bar in the palm of your hand and held the stiffener with two fingers of that hand while driving the rivets, the dimpling could have been prevented.
    N1PA

  22. #1862

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    I'll take a look. Thanks.
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  23. #1863

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    Right you are! I did those on the table with a plate under the rib and it looks like I must have hit the rivet before it was on the plate...lesson learned.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  24. #1864

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    I'm on the 3rd skin piece and that involves the landing/taxi light. I'm putting in a 30 watt LED with a 60* beam which I aimed maybe 100 yds in front of the nose when in an approximate 3 pt landing configuration. I had the wing hung on the fuselage awhile back and estimated where to aim inside my shop with the house lights off so it very well may need some tweaking once real time flying happens. This will probably just be a bright light for recognition purposes. I'm also doing nav and a strobe light.

    My plan is to cut the skin in an approximate shape, finish riveting the skin then go back to make the plexiglass lens and trim ring before painting. Is that the usual method or would it be better to put the finish cut and make the trim while I still have access to the inside of the wing? I shouldn't need to get into the light unless it needs re-aiming since it's LED and no bulb to replace (I hope). Thoughts?
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

  25. #1865
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    Quote Originally Posted by Lowrider View Post
    My plan is to cut the skin in an approximate shape, finish riveting the skin then go back to make the plexiglass lens and trim ring before painting. Is that the usual method or would it be better to put the finish cut and make the trim while I still have access to the inside of the wing? I shouldn't need to get into the light unless it needs re-aiming since it's LED and no bulb to replace (I hope). Thoughts?
    It is always better to have access and not use it than to not have it and need it.

    Before you cut the leading edge for the landing light make sure that the bend in the leading edge is accurate or just a whisker tighter than desired. If not the skin will spring outward when you cut the hole making a bulge in the skin around the landing light. You will not like this.
    N1PA

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