EdT brought this up on another thread.
I thought it more appropriate to start a new thread...............As this has nothing to do with installing fuel tank.
"Good morning Eric,
Looking at the routing of your fuel line out of the center section tank made me think of something else. The Pitts S-2 has an AD on cracking of the top longerons just aft of the weld where the aft leg connects to the longeron. You can find it on the Aviat web site. I have seen many pictures of the Pitts, various models, where the front and aft cabane struts are connected near the top with a strong piece of 4130 tubing, presumably to address this problem. McKenzie suggested adding a tube, threaded at each end, between the two bolts that attach the upper wing to the top of the cabanes. I believe the purpose is to stabilize the rear leg so as to prevent the flexing that is responsible for cracking in the longeron. I plan to install this tube, and if you do so it might require some tweaking to get the fuel line out of the way. I'm sure others know more about this. Perhaps they can add some additional comments? As always, great work."
__________________
Ed T--Flying S-2B, Building 200HP Skybolt
Last edited by Ed T; Today at 09:07 AM.
I responded with....
Thanks for the compliment.
I am trying to understand the areas of concern you mention.
I placed a straight edge between the bolts (at center of bolt) holding the wing on. I don't see any room for a tube there.
If I could fit a tube, this would need to be a thick walled tube, if the ends need to be threaded for the wing attach bolts.
I don't know if this would be as strong as the nuts now being used on those bolts.
The cabane rear leg that gets to the longeron? I attached a photograph, to ask if this is where you have noticed cracking
I thought it more appropriate to start a new thread...............As this has nothing to do with installing fuel tank.
"Good morning Eric,
Looking at the routing of your fuel line out of the center section tank made me think of something else. The Pitts S-2 has an AD on cracking of the top longerons just aft of the weld where the aft leg connects to the longeron. You can find it on the Aviat web site. I have seen many pictures of the Pitts, various models, where the front and aft cabane struts are connected near the top with a strong piece of 4130 tubing, presumably to address this problem. McKenzie suggested adding a tube, threaded at each end, between the two bolts that attach the upper wing to the top of the cabanes. I believe the purpose is to stabilize the rear leg so as to prevent the flexing that is responsible for cracking in the longeron. I plan to install this tube, and if you do so it might require some tweaking to get the fuel line out of the way. I'm sure others know more about this. Perhaps they can add some additional comments? As always, great work."
__________________
Ed T--Flying S-2B, Building 200HP Skybolt
Last edited by Ed T; Today at 09:07 AM.
I responded with....
Thanks for the compliment.
I am trying to understand the areas of concern you mention.
I placed a straight edge between the bolts (at center of bolt) holding the wing on. I don't see any room for a tube there.
If I could fit a tube, this would need to be a thick walled tube, if the ends need to be threaded for the wing attach bolts.
I don't know if this would be as strong as the nuts now being used on those bolts.
The cabane rear leg that gets to the longeron? I attached a photograph, to ask if this is where you have noticed cracking
