Excluding the why's or wherefore's of this.. I came up with a garage sale (let's call it) PA18 (stripped, I mean nothing not welded on) fuselage with zero rust in very good condition except for a slight tweak near the front door center cluster (rear bottom of windshield area right side). I will either use it in an experimental or use it as a form to build an experimental fuse. Anyway the legalities are not my question. My question concerns alignment. I was told this was "off" a little after it had been through an A&P school of some kind and was supposedly signed off as good by the schools IA (no paperwork, can't even identify it as originail Piper except it obviously is PA-18). When I got it home I leveled it up and found these things: Plumb bob level at door punch mark, wing mounts level across and 2.5" difference front to back (center wing mounts)or 4.5 degrees difference front to back (I know that is not the AOI), fuselage floor is level across, tailpost level both directions, firewall level and top firewall bolt holes measure even to rear of sides behind seating area. Strut mounts within 3 degrees of each other and sides from wing attach to strut mounts are within 1/4 inch side to side. Piper tolerances found on Christian Sturms sight are tighter than that with a max of 1/8 inch (you could say one side was 1/8" to long and the other side 1/8" to short) I think on the strut fittings BUT would the things I found fall within a "normal" used fuse?? I believe the plane should fly ok and respond correctly after proper rigging but is that a reasonable idea?
Now the real concern. With everything leveled up in my garage I stand in front of the plane and using my most critical eye I sight through the center line and then looking side to side I perceive the right (front of door cluster) side to be "straighter" up and down than the left side at the front door post cluster ( at bottom rear of windshield area) referencing the top and fuse floor. I drop a string centered between the front wing attach fitting bolts and the string sets 1/2 inch right (to door side) of the center line (tailpost to firewall) string. My eyeball "fix" is confirmed. It would seem the right side could be pushed out at the front-of-door cluster to fix all this but wait.. Before grabbing the porta-power I check the distances from center bolt to center tube, (front wing mount bolts to lower longerons) and the right side comes up 1/4" shorter (my top and bottom levels did not indicate the 1/4 inch difference and I attribute this to my inability to measure "level" as good as I can measure distance). So the right side is shorter top to bottom than the left and will only get worse if I push the center front of the right door cluster "out".. What I think: The cluster needs to go out on the right by 1/2 inch, and the tube going from the windshield bottom to the right wing mount cluster needs to be "lengthened"1/4"+. There is new paint in this area so I think some work was done there. Me, I want to leave it alone. The welds everywhere look good, If it ain't really broke don't fix it, etc.. I can use the cowl formers to make everything look very good outside (tubes will be inside cowling) on the cowling and only the most critical eye maybe would spot this. The planned use for the plane is poking holes in the sky and not show. Thoughts?? I would not expect anyone to fess up to having a fuse more than .00034" out on their own plane but you could say " I have a friend that has a cub like that and it fly's fine". I'm really looking to find out if others are flying slightly "bent " fuselages successfully or if I absolutly positivly must fix these things or during the first stall the plane will roll over on it's back in an unrecoverable inverted flat spin!
::: Seriously it looks like the student got a tube a little off and that's where the problem is. Like so many posts I'm looking for validation that I can use this "as is" dimension wise ( I know structural welds are not discussed here and that is MY responsibility). If it really is not a good idea or fairly common I will (grudgingly) deal with it. Thanks in advance to all thoughtful responses. Dave
P.S. For those who are churning inside about using this in an experimental I have contacted DAR's and FAA (who just won't confirm or deny) and if I build everything else it "may", heavy emphasis on "may" be ok. I lose all fuselage 20 points or so out of 140 or so (windshield is part of the fuse so I get to buy a commercially made windshield and I think torque tube and sticks if I want since they don't count). And I did find out if it fails I can strip all my other parts off, buy or build a fuse and try again with no penalty except "DAR bucks" , reusing my logs for the parts I did build, and spending the time to build it and the worst part of that : welding clusters. I started working on tail feathers a few weeks ago before this came along and it really helps to have something to attach "built" parts to even if it doesn't eventually wind up in my plane.
Now the real concern. With everything leveled up in my garage I stand in front of the plane and using my most critical eye I sight through the center line and then looking side to side I perceive the right (front of door cluster) side to be "straighter" up and down than the left side at the front door post cluster ( at bottom rear of windshield area) referencing the top and fuse floor. I drop a string centered between the front wing attach fitting bolts and the string sets 1/2 inch right (to door side) of the center line (tailpost to firewall) string. My eyeball "fix" is confirmed. It would seem the right side could be pushed out at the front-of-door cluster to fix all this but wait.. Before grabbing the porta-power I check the distances from center bolt to center tube, (front wing mount bolts to lower longerons) and the right side comes up 1/4" shorter (my top and bottom levels did not indicate the 1/4 inch difference and I attribute this to my inability to measure "level" as good as I can measure distance). So the right side is shorter top to bottom than the left and will only get worse if I push the center front of the right door cluster "out".. What I think: The cluster needs to go out on the right by 1/2 inch, and the tube going from the windshield bottom to the right wing mount cluster needs to be "lengthened"1/4"+. There is new paint in this area so I think some work was done there. Me, I want to leave it alone. The welds everywhere look good, If it ain't really broke don't fix it, etc.. I can use the cowl formers to make everything look very good outside (tubes will be inside cowling) on the cowling and only the most critical eye maybe would spot this. The planned use for the plane is poking holes in the sky and not show. Thoughts?? I would not expect anyone to fess up to having a fuse more than .00034" out on their own plane but you could say " I have a friend that has a cub like that and it fly's fine". I'm really looking to find out if others are flying slightly "bent " fuselages successfully or if I absolutly positivly must fix these things or during the first stall the plane will roll over on it's back in an unrecoverable inverted flat spin!
::: Seriously it looks like the student got a tube a little off and that's where the problem is. Like so many posts I'm looking for validation that I can use this "as is" dimension wise ( I know structural welds are not discussed here and that is MY responsibility). If it really is not a good idea or fairly common I will (grudgingly) deal with it. Thanks in advance to all thoughtful responses. DaveP.S. For those who are churning inside about using this in an experimental I have contacted DAR's and FAA (who just won't confirm or deny) and if I build everything else it "may", heavy emphasis on "may" be ok. I lose all fuselage 20 points or so out of 140 or so (windshield is part of the fuse so I get to buy a commercially made windshield and I think torque tube and sticks if I want since they don't count). And I did find out if it fails I can strip all my other parts off, buy or build a fuse and try again with no penalty except "DAR bucks" , reusing my logs for the parts I did build, and spending the time to build it and the worst part of that : welding clusters. I started working on tail feathers a few weeks ago before this came along and it really helps to have something to attach "built" parts to even if it doesn't eventually wind up in my plane.
Eventually I'll need help with the finish welding on all the parts.. I guess there are some good welders here in Port Townsend at the boat building places. dave
