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Quickbuild Fuel Tank Attachment

W

Wyzepilot

Active Member
Good Morning,

I am finally getting started on my quick build wings reading through the plans and inspecting the work done. In general everything looks great. However, Vans included a separate notice for quick builders to carefully inspect the fuel tank attachment screws and bolts as they may not be fastened completely for shipping. I found the exact opposite. Not only were all the screws and bolts in but the bolts were way over torqued. I checked a few of them and they were all right around 60 in lbs. These are AN3-4a bolts. I plan on removing both tanks anyway to do a leak test and install the old school stall waring system. My question is, should those bolts be replaced with new ones? Has anyone else noticed the same thing?

Other than that I would call the workmanship excellent from what I have seen so far.

Thanks,

Dave
 
Bolts

I removed my the tanks from my QB wings as well, for a leak check. Some of the bolts were very tight. I replaced all of the hardware when I reinstalled them. Probably not necessary but it was minimal cost.
 
I put in the same bolts. What I have changed in the past, correct or not is the locking nuts if I needed to take them off for any reason. I couldn't change the underlying nutplates for those bolts in the wing therefore I thought there was no value to using new bolts. Who knows. There certainly is a lot of screws around the periphery of the tank that attach to the spar.
 
I'm curious how you measured the 60 in lbs. The 'breakaway' (static friction) torque is higher than the running torque. Did you mark the position, loosen a turn, then torque in?

My QB tanks came with many oversize (long) bolts, with a stack of washers under the head!
 
BobTurner said:
I'm curious how you measured the 60 in lbs. The 'breakaway' (static friction) torque is higher than the running torque. Did you mark the position, loosen a turn, then torque in?

My QB tanks came with many oversize (long) bolts, with a stack of washers under the head!
Click to expand...

Thats a good point Bob, the 60 inch lbs was just an estimate. I loosened then torqued back in to the same spot. My pointer went well past the 60 in lbs which is the max reading on my beam torque wrench. I then loosened the bolt and measured its friction drag torque which was about 8 inch lbs. That's how I came up with approximately 60 inch lbs. It may have even been more. The bolts themselves are not oversized and have one washer under the bolt head. I plan on pulling the tanks off anyway to install the fuel sender and do a thorough leak test. I will re-tourque the bolts when I reinstall the tanks. Its surprising how little force 20-25 in lbs is and how easy it is to over torque one of these an3 bolts. I am curious to know how much torque it would take to stretch and damage one of these bolts? I am guessing that they were no where near that point but I don't know. Thanks for the responses. I still have so much to learn.

Dave
 
While you can still get at them "relatively easily" it's worth checking the B nuts on the vent lines. Others including myself have found leaks in this area with QB wings.
 
over torque determination

If bolts are over torqued they are stretched, hence, the need for replacement, at least that is what folks/mechanics/engineers have always told me. So, if they are really damaged/stretched, then a loosing and re-torque to the same position will have little meaning I believe. Even in older equipment, with possible corrosion helping to "secure" the nut, I have found it is pretty clear (qualitative albeit!) by the force on the wrench handle if they were over tightened/torqued on 3A bolts. For a few dollars in N&B, I would not think twice about replacing all as mentioned earlier in the thread. Good luck on the leak test!
 
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