Bearhawk Aircraft Bearhawk Tailwheels LLC Eric Newton's Builder Manuals Bearhawk Plans Bearhawk Store


No announcement yet.

Any hints/tips on drilling the holes in the pilot seat rail?

  • Filter
  • Time
  • Show
Clear All
new posts

  • Any hints/tips on drilling the holes in the pilot seat rail?

    Any hints/tips on drilling the bolts in the pilot seat rail? I thought I did a pretty good job marking the rear most hole, and drilling on center, but once fitting the seat, it seems my job wasn't the best. My drill walked just a smidgen on the seat rail and the tapped hole then doesn't line up. Very nervous about trying the next set forward...
    LSA QB started 2/6/2022, My Build Log, N67BH reserved.

  • #2
    The good news is, once you enlarge the holes to properly align, they will be out of sight, no one will ever see it
    Revo Sunglasses Ambassador


    • #3
      Have you considered match drilling the remaining holes....meaning move the seat up an inch or so and match drill the next hole in the fixed rail to the hole in your sliding seat.

      Also, it sounds like maybe you threaded the hole in your seat to lock it in position. I've seen a quick release ball lock dowel hold the seat.
      Screen Shot 2022-02-21 at 12.46.59 PM.png
      Brooks Cone
      Southeast Michigan
      Patrol #303, Kit build


      • #4
        The LSA is different than the Patrol in it's seat locking mechanism. The tube on the seat has a nut welded to the top of it from the factory. You are then suppose to drill 4 position holes in each seat tube (on the fuselage) to match and then bolt your seat in. To move positions, you have to remove the two bolts, slide it forward, and then screw it back down :-(

        I am considering not using the bolt and match drill holes through the side and using a ball locking pin as Bcone1381 has suggested. Not only would it be easier to adjust the seat, but much easier to drill properly.

        Bolts welded to the rear seat slides by jeremy4039, on Flickr

        Rear most seat stop holes drilled, tapped, and bolts actually thread in! by jeremy4039, on Flickr
        Last edited by jcowgar; 02-21-2022, 08:07 AM.
        LSA QB started 2/6/2022, My Build Log, N67BH reserved.


        • Bcone1381
          Bcone1381 commented
          Editing a comment
          Thats nice!! Kits are getting nicer!!

          Center drill that bolt. Chuck it up in a lathe and drill a 3/32" hole from the head thru the center of the bolt. (Do you have access to a lathe?) Then you can drill a pilot hole in the rail.

        • jcowgar
          jcowgar commented
          Editing a comment
          I do not have a lathe :-( That's a good idea though. I'll ask around at my local EAA club.

      • #5
        I welded a short tube on in place of the nut on my scratch build and used a pip pin similar to what Bcone shows.

        Used a transfer punch to center punch the hole locations.

        Probably could also use a transfer punch through the nut.

        But if I was to do it again, I would go sideways with the pip pin passing all the way thru instead of from the top. This would result in a stronger attachment as wouldn't be depending on the "slit tube" not bending outward under load since the pin would be in "double shear" instead of single sheer that generally is to be avoided..

        I am sure it is strong enough the way it is, after all, the seat belt (tied to the fuselage frame, not the seat)should be taking all the load in a crash.

        But it would just "Feel a bit more "right"", adding strength without any weight penalty....


        • #6
          Brooks has the right approach. I would probably do a series of pilot bolts working your way up to something just undersized and then do the final drill to size.


          • #7
            You could use a smaller bushing that you can buy at lowes that would fit inside the welded nut. Use the bushing as a guide to drill the hole undersized then move seat out of the way and step up the hole size to final diameter/size. The bushings can be found at a real hardware store for 25-50 cents.

            We use similar techniques on drilling structure on production lines with special drill plates and fixtures...the bushings are replaceable.


            • #8
              Thanks guys for the suggestions! I wound up drilling horizontally and went with a stainless steel locking pin in each rail. I actually think it is more secure, going through both walls, and easier to adjust the seat. I am the only pilot right now, but two of girls are in ground school right now and starting flight training this spring. The one is already a balloon pilot. Long story, but in short, I think I will need to adjust the pilot seat more frequently than some.
              LSA QB started 2/6/2022, My Build Log, N67BH reserved.


              • #9
                Like Brooks, I drilled out the bolt on my lathe then used it as a pilot to drill all holes. I think I have four per side. After all were drilled I reamed the welded hole nut out to the size of my adjustment pin. I fabricated a spring loaded mechanism for my adjustment to eliminate using the bolts.
                I would be happy to send you my drilled out bolts however I'm in Arizona foe a couple more weeks,


                • jcowgar
                  jcowgar commented
                  Editing a comment
                  Thanks for the offer, but I wound up drilling it out horizontally and using a locking T-pin. I can now change my seat position w/o tools. I like some of the handle based locking mechanisms I've seen, but I'm not that good :-)

              • #10
                Different Strokes, The picture below shows the seat locking system I made for my LSA .Stinger
                Attached Files