Results 1 to 10 of 10

Thread: Choosing fittings for a welded fuselage

  1. #1

    Join Date
    Jul 2011
    Location
    Orange, CA
    Posts
    38

    Choosing fittings for a welded fuselage

    Happy weekend, everyone.

    I'm at a point of having to make some decisions on my project and could sure use some input.

    My project is a Stits SA6B Flutterbug, which has a welded 4130 tube fuselage. It's structurally complete, and now I'm pondering all the fittings that I may need down the road. I'm debating what can be attached to the structure with Adel clamps (or similar homemade fittings) and what needs to be bolted to a welded flange/other fitting. Is there a general rule of thumb for what SHOULD be hard mounted vs clamped? I'm specifically wondering about floorboards (all weight loads will still be transferred by resting on the structure), seatbacks/bottoms, the instrument panel, and a sheet metal panel that covers the top half of the fuselage from the cockpit forward.

    In addition, there is a modification from the plans that the previous builder incorporated. The plans have a supplement for a brace in the rear cockpit. The builder modified the design, I guess to make it symmetric and more aesthetically pleasing. Unfortunately, it cuts down on available room and I have to lower myself into the rear cockpit using my arms because my knees won't clear otherwise. I'd rather not subject my passengers (i.e. wife...) to that. Is it worth it to remove the modification and weld it as designed, or am I likely to do more damage to the thin-walled tubing that it's currently welded to? I guess I could leave a healthy boss in place and not try to file down anywhere close to the longeron walls. Pictures of this part are attached.

    Finally, I'm not sure if the previous builder oiled the inside of any of the tubing. What are the repercussions of burning off this oil while welding fittings? Will a simple re-oiling be sufficient?

    picture.jpgplans.jpg

    -Tony

  2. #2
    Neil's Avatar
    Join Date
    Aug 2011
    Location
    Monroe, LA
    Posts
    87
    Sort of a personal opinion here, but I always figured that Adel clamps were designed by someone who forgot to weld a tab or fitting where he needed it. I do have some Adel clamps on my airplane, but for the most part they are around a hose or cable and attached to a tab provided for the clamp. You can see a couple in this photo.0013.jpg Do what you can to keep the use of Adel clamps to a minimum.
    Last edited by Neil; 05-25-2012 at 11:50 PM.

  3. #3
    prasmussen's Avatar
    Join Date
    Feb 2012
    Location
    2OH8
    Posts
    93
    Two builders, five opinions. Here is what I have discovered about welded tabs:




    • Even if you buy the tab to weld on, it is going to be more complicated an operation than slipping on an adel clamp.
    • Back side of the tab is hard to paint; place to rust.

    • Ever had to adjust/move a welded tab?
    • Heating can cause the tube to distort.
    • I have never heard of a tube with oil in it exploding but I have had a weld “hole” itself when welding a sealed container (tube welded at either end).
    • I once saw a Jungmeister (old-timey aerobatic biplane) that had its fairing strips TIED to the fuselage tubing. They could have used welded tabs but string was sufficient and lighter (I believe they used heavy twine and then varnished over it to seal the knot).



    That having been said, welded tabs sure hold things securely and don't cause unsightly lumps in the cover like adel clamps on longerons.

    Best of luck!

  4. #4

    Join Date
    Jul 2011
    Location
    Orange, CA
    Posts
    38
    Hmm...I'm hearing different things here!

    My gut reaction is to agree with Neil on keeping them to a minimum and mounting things the "right" way. However, the flexibility and ease of an Adel (or Adel-like) clamp is very appealing since, for one thing, it would mean that I would still have the option of where things get mounted down the line. To weld tabs, I need to figure out (correctly!) how I want everything mounted today even though I won't be attaching hardware/components/etc for at least another several months.

    Will the FAA balk at using clamps for anything other than ancillary hardware?

    -Tony

  5. #5

    Join Date
    Jul 2011
    Location
    Clarklake, MI
    Posts
    1,281
    Recommended practices for MS21919 cushion clamps are commonly violated, nearly every airplane has at least one improperly installed. When practical, the backside of the clamp should rest against a structural member, not to exceed the recommended angle. Neil S. has it exactly right!

    Tony, simple flat metal tabs are very easy to instally and not really that difficult to relocate when something needs to be changed. But it is a homebuilt and you can do whatever you wish.....the FAA isn't going to care.
    Last edited by martymayes; 05-27-2012 at 09:25 PM.

  6. #6

    Join Date
    Jul 2011
    Location
    Orange, CA
    Posts
    38
    Quote Originally Posted by martymayes View Post
    Tony, simple flat metal tabs are very easy to instally and not really that difficult to relocate when something needs to be changed. But it is a homebuilt and you can do whatever you wish.....the FAA isn't going to care.
    Fair enough - guess I'll just steel my nerves, plan my tabs as best I can, and weld them in place. I'm concerned about the ones I will discover down the road when the fuselage is epoxy coated and new welding is not an option. We'll cross that bridge when we get there.

    -Tony

  7. #7
    prasmussen's Avatar
    Join Date
    Feb 2012
    Location
    2OH8
    Posts
    93
    My SA-3A Playboy is on the gear waiting for the daughter to graduate to be completed and I’ll have to admit to a few extra ears and tubes. Most of them are the result of my wanting to improve on Ray’s design and then finding he was right after all. Think I’ll leave them as reminders of the process even if they add a little to the GW.


    Wasn’t there at the time but am told WWI pilots referred to their aircraft as kites. I have to be reminded occasionally that this vehicle I am building needs to be more a kite than a Mercedes. Maybe we can trade pictures.

  8. #8

    Join Date
    Jul 2011
    Location
    Orange, CA
    Posts
    38
    Quote Originally Posted by prasmussen View Post
    My SA-3A Playboy is on the gear waiting for the daughter to graduate to be completed and I’ll have to admit to a few extra ears and tubes. Most of them are the result of my wanting to improve on Ray’s design and then finding he was right after all. Think I’ll leave them as reminders of the process even if they add a little to the GW.


    Wasn’t there at the time but am told WWI pilots referred to their aircraft as kites. I have to be reminded occasionally that this vehicle I am building needs to be more a kite than a Mercedes. Maybe we can trade pictures.

    I agree that Ray was probably right when he drew up these designs all those years ago. I'm trying to keep from making any changes since what's in the plans has worked just fine so far for other builders. It will also, in theory, get me in the air faster than if I had to reinvent the wheel...

    -Tony

  9. #9
    prasmussen's Avatar
    Join Date
    Feb 2012
    Location
    2OH8
    Posts
    93
    I agree that Ray was probably right when he drew up these designs all those years ago. I'm trying to keep from making any changes since what's in the plans has worked just fine so far for other builders. It will also, in theory, get me in the air faster than if I had to reinvent the wheel...

    -Tony[/QUOTE]

    Enjoyed meeting Ray once at an Oshkosh fabric covering workshop when he owned the paint and process. Gave me a video to use in a class I was teaching. No nonsense sort of guy. I admired his style.

    Still have to change a few things in his design............. ;-)

  10. #10
    Richard Warner's Avatar
    Join Date
    Aug 2011
    Location
    Covington, LA
    Posts
    69
    I'd cut that brace out of the rear cockpit if its not on the plans and it interfered with getting in and out.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •