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Thread: Building and finishing my 2+2/PA 14

  1. #41
    C-FIJK's Avatar
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    Marty I saw this on a sportsman here in Canada and as you know I built one as well if I was to do it again , I would not use the stick it gets in your way on the sportsman hits your legs , BTW Awesome job your doing !!!!!!
    Gerry Marcil

    Every day spent flying is a great day !

  2. #42
    Marty57's Avatar
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    Yeah, I'll weld up the ends of the pedals before I finish them. Been trying to move forward with the big items on the fuselage so I can get the fuselage ready for paint. I hope to finish up the seat tracks today or tomorrow than move onto the seat belt tabs and a few other little things up front. All this "little" stuff sure takes a lot of time!
    Marty
    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  3. #43
    Tim's Avatar
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    Marty, I like the shims under the seat tracks, you'll be able to move the seats back much farther than mine. When I get old I may do the same thing.

  4. #44
    Marty57's Avatar
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    Tim,
    Short legs make for innovative building sometimes! You have no idea how many times I have been in and out of the fuselage to try to figure out the best set up for the seats and rudder pedals. I think I have it right. It is nice how far back the seats will move and they will be easy to remove also. lots of figuring to make this work. Thanks again for the pictures of your seats; that helped with the decision making.
    Marty
    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  5. #45
    Cub junkie's Avatar
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    Wag aero plans being vague in some areas brings out the creativity in a builder. Good idea on the seat tracks Marty. I always thought the cable runs/control system on the 2+2 was a little wonky. I put a J3 torque tube in one for a guy but he wanted to sit in the center PA12 style.

  6. #46

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    Marty great work. I ESPECIALLY like the shims. I am short/small so I don't hit my knees getting in, but my long legged
    friends have to do strange yoga moves. Lots of good progress. Jeff

  7. #47
    Marty57's Avatar
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    I think the shims will work out real nice; I'm just about done welding in all the necessary tabs for the tracks. A bit tedious to get it all right and square but coming along. One thing I have noticed is that the sticks are not centered on the seats! I'm going to have to get creative with some stick angles or change the attach points of the sticks some. After the seats are in place I can get a better feel for how the sticks will work. Yeah, the Wag plans get very vague with each turn of the pages.

    Some tricks for jigging up something like the seats. After I made all the tabs, each had to be set in place using the tracks as a jig. I used pieces of floor plywood so everything was spaced as it will be when finished. I used sharpie to blacken the top of the tab, held it in place, and put a drill bit through the hole. Rotating the bit by hand gives me an exact mark for each hole. I then used a nut plate drill jig to drill holes for the attachment of the nut plate. Nut plates will go on after the fuselage is painted.

    Marty

    Some pictures:



    Marking the hole location with a drill bit.



    Tab marked and drilled



    Tab in place and tack welded



    Main tabs in place for the tracks, ready for final welding.

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    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  8. #48
    Bill Rusk's Avatar
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    Great creative solution to the problem of locating the tab, Marty. Well done!! It is coming along very nicely. I'm sure enjoying the blog. Thanks for taking the time to write it up and post pictures.

    Bill
    Very Blessed.

  9. #49
    Marty57's Avatar
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    Thanks Bill; I keep going back to your build when I get to another step I'm not familiar with, sure helps. Question on the nut plates, did you use an aluminum rivet with your squeezer to attach the nut plates or steel ? Are there any concerns with dissimilar metal corrosion using aluminum rivets ? I'm going to prime with epoxy primer before attaching the nut plates but the holes will need to be cleaned out befor riveting. Thanks.

    Marty
    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  10. #50
    Bill Rusk's Avatar
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    Marty

    Aluminum rivets and the nutplates will be fine. The nutplates are coated and corrosion is rarely an issue. I have heard of some folks dipping rivets in various primers, AV-15, ACS50, Boelube, etc prior to riveting but frankly I think it is massive overkill unless you expect to park your airplane outside on the Gulf Coast and land in salt water every day. Just my opinion.

    Bill
    Very Blessed.
    Likes pfm liked this post

  11. #51
    Marty57's Avatar
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    Big day today. I finished welding in all the seat tabs and fit the tracks and seats in place for the first time. Everything fits and slides nicely. Once the floating nut plates are installed the tracks will be slightly adjustable for better movement of the seats. All in all I'm very happy. Biggest event was both my wife and I climbing into the plane for the first time. After a combined weight loss of 160 lbs between us (95 for me, 65 for my wife) it was a moment of truth. I bought the plans for the plane back in 2005 so it's been a long hall so far. Drum roll please ....... we fit! With my seat forward and my wife's seat back we have plenty of room; it's very comfortable. It will be nice when the seats are finished and the back rest is at it's proper angle but I'm real happy getting to this point. Now, on to figuring out the seat belt tabs and some other floor tabs. Getting closer to painting this fuselage every day.

    Marty

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    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  12. #52

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    Marty, im sure you thought of it but make sure to have some stops so your seats dont roll right out the back door.

  13. #53
    Marty57's Avatar
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    I'm going to drill and tap a hole at both ends of the track and place a stop bolt in the hole. A was thinking of some sort of flip over cam lever at the front as a safety lock of some type. I'm not sure how that will happen or work but it's in the planning stage. I still need to figure out the seat belt attach tabs. The tabs will be real close to the rudder cable pulley by the door. I also need to figure out how to position the tab vertically so the seat belt wont have to turn. The only point to weld the tab to is the cross tube. Not sure if wrapping the tab around the tube will be ok. More to plan.
    Marty
    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  14. #54
    skywagon8a's Avatar
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    Quote Originally Posted by Marty57 View Post

    Marty, while it may just be the angle of the photo, it appears as though that rusty curved "U" channel could be pressed against the elevator torque tube causing interference. It might be a good idea to weld in a vertical piece of "U" between the rusty piece and the cross tube as a safety factor.
    N1PA

  15. #55
    Marty57's Avatar
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    Skywagon,
    It's the angle. The tube clears the "U" channel through the full range of motion. Thanks for looking; always good to have a second set of eyes.

    Marty
    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  16. #56
    skywagon8a's Avatar
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    Quote Originally Posted by Marty57 View Post
    Skywagon,
    It's the angle. The tube clears the "U" channel through the full range of motion. Thanks for looking; always good to have a second set of eyes.

    Marty
    Marty, My concern is that IF something hit that channel pushing it up, AND you were unaware that it happened, then what?? Stuff does happen once in a while.
    N1PA

  17. #57
    Marty57's Avatar
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    Skywagon,
    I get your concern now, makes sense. There isn't much support in that area, you are right. I'll take a look at welding something on either side of the tube from the channel to the "V" above it. Thanks for the input, good idea.

    Marty
    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  18. #58
    jimboflying's Avatar
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    Marty,

    What thickness of material are you using for the seatbelt attach fittings?

  19. #59

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    Marty,

    Congratulations to to you and your wife on the weight loss! That takes real determination - kind of like building an airplane.

  20. #60
    Marty57's Avatar
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    Jim,
    The seat belt tabs are .090 4130. I bought them from Javron to save some time fabricating them. I have decided to wrap them around the cross tube, the surface of the tab will be parallel with the floor and angled up about 45 degrees. I think this will work easily. Pictures of the tabs are on another post, http://www.supercub.org/forum/showth...seat-belt-tabs

    Marty
    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  21. #61
    jimboflying's Avatar
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    Seatbelts are important. A friend of mine survived a crash but the seatbelts broke and he sustained serious facial injuries.

  22. #62
    skywagon8a's Avatar
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    Quote Originally Posted by Marty57 View Post
    Jim,
    The seat belt tabs are .090 4130. I bought them from Javron to save some time fabricating them. I have decided to wrap them around the cross tube, the surface of the tab will be parallel with the floor and angled up about 45 degrees. I think this will work easily. Pictures of the tabs are on another post, http://www.supercub.org/forum/showth...seat-belt-tabs

    Marty
    Quote Originally Posted by jimboflying View Post
    Seatbelts are important. A friend of mine survived a crash but the seatbelts broke and he sustained serious facial injuries.
    These two comments are leading me to question how much thought is going into the seat belt installations. Not just Marty and Jim, but everyone. This might be a good exercise for a retired engineer's evening project. He could calculate the crash loads of a heavy human body against the seat belt. The angle these loads apply to the seat belt anchors. The size of the bolt which holds the belt to the anchor. Is this bolt in shear or bending? Is the bolt in a single (bending) or double shear installation? The tear out loads of the bolt in the hole of the anchor strap. What is the direction of the load on the welding of the anchor strap? Are there enough inches of weld for the applied load? Will the .090" by x" wide strap handle these loads? How far around the fuselage tube should the anchor strap be wrapped? Will the anchor strap tear off in a crash? What alloy should the strap be? Will the fuselage tube support all of the above loads? All of these questions, and perhaps others, need to be answered with certainty. Whichever of those questions produces the least strength is the location that will fail first.

    Darrel Starr, are you there?
    N1PA

  23. #63
    Cub junkie's Avatar
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    If it's up to me and I'm free stylin' on seat belt mounts on an experimental I always go with .125 material in double shear. If you shear a 5/16 or 3/8 bolt in double shear you are probably not salvageable. As a former sprint car driver I have taken a few extreme G rides and have the mended collar bone to remind me.

  24. #64
    Marty57's Avatar
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    I'm a bit stuck with the seat belt install and the seat's for that matter. After installing the seat tracks on the shims I'm having difficulties with the seats rolling easily. The new Piper seat track is taller and that might eliminate the issue. I will likely need to toss the tracks I have and get the newer ones from McFarland. The issue is that they are 2.3" wide at the base vs the current ones I have at 1" wide at the base. This adds to the issues with the seat belts.

    First, a current picture of the tracks and seat with out the floor. Remember, anything can be changed; I need to get this right.



    Another view:



    You can see some of the issues here for the seatbelt install; where will they fit? I have two options right now to consider. This first option is to simply weld the tabs to a newly welded cross tube; the tabs would be between the seat rails. This would be easy but is it ok? I just don't have enough information to go on. Are the tabs too close, is the orientation ok for the seat belts? The belts would either run between the seat back and the butt cushion or around the seat. Here's a couple pictures of option one:



    The next option is to add a another tube to the right of the seat track and locate right tab on that tube and the left on the side of the fuselage above the ruder cable pulley. Is the left tab location in this option strong enough? It's just 3/4, maybe .035? Here's a picture of option 2:



    I can shorten the tracks and get rid of the wood shim under the track if necessary; those are there so I can slide the seat back further for easier entry and exit. As for thickness of tabs, I can go with any thickness at this point; not restricted to the tabs I have.

    I'm really stuck here with figuring this out. Needless to say, there is nothing in the plans except to use a narrowed Cessna 172 seat and tracks with no indication of mount ing the tracks and no mention of the seat belts at all. This phase of the project is very slow and difficult when I have to be the designer and builder; not being very comfortable with the design part. I am open to any suggestions and changes here; different seats, tracks, other options on the seat belts, etc. I can't move forward on anything until I solve this problem. Thoughts???

    Thanks,
    Marty
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    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  25. #65
    Cub junkie's Avatar
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    As an internet trolling expert, I like your last picture with the additional tubes.

  26. #66
    skywagon8a's Avatar
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    Marty, some random thoughts.
    This link shows a recommended 55* angle to the horizontal for the lap belt. Figure this from your normal seat location.
    https://www.faa.gov/pilots/safety/pi...tbelt_web2.pdf

    Dave Thurston's book "Design for Flying" suggests that the anchor location for the shoulder harness be able to support a 4000 lb load. Other publications suggest that the angle of the shoulder harness be such that there be no down load on the shoulders. 20* above comes to mind?

    CAR 3.386(a) states that the belt attachments be able to withstand a load of 3.0g upward, 9.0g forward and 1.5g sideward. Since the belt is at an angle of 55* it will take some geometry to get the correct answer. The equation "the square of the hypotenuse is equal to the sum of the squares of the other two sides" will work.

    I would chose to place the seat belt outboard of the seat frame in order to prevent crushing loads on your hips.

    A suggestion. If the straps which you show clamped to the tubing were in the shape of a triangle, they would distribute the loads across a larger area of the tubing thus reducing any tendency to buckle the tube. And also would give a greater seat position range for optimum strength.
    N1PA

  27. #67
    Marty57's Avatar
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    Skywagon,
    The Shoulder harness is pretty easy; either the "X" brace can be used or the cross tube at the rear wing attach fitting location. As for the 55* for the seat belt I need to see where that puts the attach point relative to the seat when it is forward. As I have been doing some research into this, one of the issues came up with moving the anchor points to the fuselage frame from the seat frame. With the seat frame attach points the seat belt stays at the optimum angle and is snug in all seat positions; the floor mounted anchor points vary the angle and the seat can not be slid forward after buckling in. The sliding issue is not a big deal because the should straps would need to be adjusted when sliding anyway. As for the size of the tabs; the ones I have are the same size as the STC kit that moves the seat belts from the seat to the floor in the PA-18. Regarding the formula you gave me; what is that used for? I'm not sure what is being calculated using the formula?

    The last two pictures give me the best option to have the seat belts at 55* where I will most often have the seat. Take a look at the two pictures below. I think the left side tab needs to be attached to the side of the fuselage to avoid crushing of the hips. I could weld a tube from the longeron to the diagonal that forms the door opening. In the picture I'm holding a piece of strap steel just for location. The tab could than be welded in the wrap method so it angles away from the side wall enough for bolt clearance. The last two pictures I have in previous post show a good location for the right tab; that gives me 55* also. Thoughts on this idea?

    Marty

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    N367PS
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  28. #68
    skywagon8a's Avatar
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    PM sent.
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  29. #69
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    Cub Junkie,

    What does the term "double shear" mean?

  30. #70
    jimboflying's Avatar
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    Marty,

    I used the same seats and rails as you. Instead of the wood shim I just bent the rail to the needed angle since that area is only used when removing the seat.

  31. #71
    Marty57's Avatar
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    Jim,
    I tried the bend but the seat would not go past the point of the bend so I tried the shim. I have given up on the shim idea; too much flex in the floor with the shim and the seats hang up to much. With the shim removed and the tracks cut down the seats slide much better. I can't move the seats back as far as with the shim but I'll get used to it and get the hang of getting in and out. I also decided to buy new track material from McFarland. The holes in the tracks I have are pretty worn so I'll replace them. I need 25" pieces so the cost isn't too bad for four new ones. I'm getting closer on the seat belt plan. The seats you build were for a 2+2 or PA-14? How did you do the seat belts?

    Marty
    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  32. #72
    skywagon8a's Avatar
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    Quote Originally Posted by jimboflying View Post
    Cub Junkie,

    What does the term "double shear" mean?
    The upper pin is in single shear and the lower pin is in double shear. This is the method of getting double the shear strength out of one fastener.
    N1PA

  33. #73
    Lowrider
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    I'm certainly not the expert here but I did a single shear and figured if my butt shears a 3/8" AN bolt I'm toast anyway...but then it can't hurt to double the tabs. I attached mine on the longerons at a cluster with a gusset using 0.100 CM but it's attached to 0.035 in the longeron so I put in a gusset to distribute the load. My weak point is the shoulder straps which are attached at "V" in the tubes but even so they can bend...without adding a lot of heavy metal I'm not sure how to make it stronger in the overhead.
    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!

  34. #74
    Gordon Misch's Avatar
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    Another reason for double shear attachments is to eliminate bending stress on the tabs, caused by eccentric loading.
    Gordon

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  35. #75
    Marty57's Avatar
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    I guess my question is do I build the seat belt tabs up stronger than certified Cubs? I understand the greater strength of the double shear vs single but is it really necessary? Below are a couple pictures from the STC that Atlee Dodge has available. Are there issues with this design? Like many issues in building a Cub, strength and weight have to be managed accordingly and it is very easy to over build. Has any one known of this type of floor mounted seat belt set up to fail in an otherwise survivable crash? I would think that to receive an STC proof of satisfactory performance needed to be met. Or, does this set up simply match the strength of seat mounted belts and they don't have to provide any greater performance for the purpose of the STC? Gordon, how are the seat belt's attached in your '12? I need to do the back seat also so I would like to have a better understanding of the certified Cubs before I do any welding. Below are a the screen shots from Dodge's web site.

    Marty

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  36. #76
    skywagon8a's Avatar
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    The first Atlee picture shows the tab to be welded under the tubing, good installation. This allows the tab some flexibility without tearing out loads on the weld. Naturally a double shear installation would be stronger though in this circumstance is not necessary. In this example it appears that the weakest point would be the edge distance of the hole in the tab.

    This is a collection of handy bolt reference charts. http://www.skybolt.com/catalog-an-ms-hardware.pdf Look on the second page at the single shear strength of the AN4 bolt, 3680 lbs. More than enough for the seat belt application.

    Just make sure that there are no notches in the edge of the tab which would be a stress riser. A crack or tear could start at this location. Particularly if the notch is next to the end of the weld. For this reason you want the end of the weld to be behind the tubing away from the flexing portion of the tab.
    Last edited by skywagon8a; 11-26-2015 at 06:03 AM.
    N1PA

  37. #77
    Cub junkie's Avatar
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    When I made the post about doing tabs in double shear, it was only an opinion. I do it when it will work. .090 in single shear is dam strong too. Seat belts stretch in accidents, a lot more than you would imagine. An installation with proper geometry is as important as the material.
    Last edited by Cub junkie; 11-26-2015 at 11:07 AM.

  38. #78
    Gordon Misch's Avatar
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    Gordon, how are the seat belt's attached in your '12?
    Marty, in light of this discussion I'm a little embarrassed to admit that mine are the factory arrangement. However - the factory arrangement did serve me well when I wrecked my plane 25 years ago. I hit a large upturned spruce stump with enough speed to tear the engine mostly off of the fuselage, knock the radio out of the panel and destroy one wing. But the seat belt (and shoulder harness) held and I was unhurt except for a dislocated toe where the firewall folded over my foot. But despite that success, I wish I had routed the front seatbelt to the floor.
    Gordon

    N4328M KTDO
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  39. #79

    Join Date
    Feb 2009
    Location
    668 8th avenue Salt Lake City, Ut.
    Posts
    56
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    I own the original 2+2 N65WA and am just finishing a restoration. My seat belt mounts (the original configuration) consist of 3/16 " cable wrapped around the fuselage tubes. The belt clips around the cable. I will post some pictures tomorrow. Not sure how they will hold up in a crash but that is how they were done.

  40. #80
    Marty57's Avatar
    Join Date
    Jan 2005
    Location
    Nipomo, Ca
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    1,376
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    Great discussion here. I like the idea of the double shear attachment. I think I could make that attachment pretty easy for the back seat as it wraps around the rear cross tube. Same could be done for the inside tabs for the front seats. The tabs that attach to the side might be a little more difficult to do a double shear. I did come across a nice attachment from Airframes Alaska. They use a welded lock nut on a tab welded at the cluster where it would be difficult to get to the back for a nut. I also like the way the tab is tied to each of the tubes next to the cluster.


    For the sake of discussion of ideas; here's another one. Since I am welding a cross tube between the "V" on the floor, I could slide the below tab on the cross tube and weld in place between the cross tube is welded to the "V". I would still weld the short tubes between the new 3/4" .065 cross tube and the existing cross tube to keep the new tub from bending in a crash. Single tab could be use or two tabs for each belt could be added for a double shear is preferred. I need to add the short tubes in that area anyway for an attach point for the floor mounted flap handle I still need to add. Here's a drawing of this attach tab idea.



    In the picture below, this new tab idea could be welded to the new cross tube before welding to the "V". I would place the tab just to the right of the inside seat track so the seat belt would be placed just outside the seat. Thoughts on this idea?

    Marty

    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

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