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wing bolt torque?

RickWoodall

Well Known Member
I cant seem to find the torque settings for the wing bolts.
NAS 1307-50 and NAS 1304-50 (close tolerance ones). Checked manual and drawings...no love. Anyone know where it is listed?

Thanks.
 
For my 10, it was in section 5.

That is the last of the sections in the 8 1/2x11 binder, my plans started at section 6.

I am not sure how the plan set for your 9 is setup-- YMMV??
 
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Not there

Unless vans published it in invisible ink i cant find it. I have gone through all the wing attach reading, they always refer to the drawings..the drawings dont spec the torque and since the bolts arent really an7 or an10 etc, i dont think its ok to just fill in the blank myself. Hmmmmmm. Someone here has to know. Searching the archives, seems many cant figure out how to get the torque wrench on etc, but...they must have a torque to gun for??
 
On that subject, I wonder how necessary it is to get the torque just right and how many people in a *-A model can achieve it correctly. The top nut on the -A model is easy to get to but the bottom ones are probably impossible and it needs to be torque from the bolt side.
Also, these bolts are vastly on sheer force and no tension on the nut, so unless it is sloppy lose, how important is it to get them all right?
 
Check your 43.13 manual for torque values by bolt size.

Assuming you have one or can get access to one.

Glenn Wilkinson
 
On that subject, I wonder how necessary it is to get the torque just right and how many people in a *-A model can achieve it correctly. The top nut on the -A model is easy to get to but the bottom ones are probably impossible and it needs to be torque from the bolt side.
Also, these bolts are vastly on sheer force and no tension on the nut, so unless it is sloppy lose, how important is it to get them all right?

The guy at Van's I talked to (can't remember who it was that time) said that torque isn't important, as the nuts were there pretty much just to keep the bolts from falling out. Seems like those bolts would also carry some of the fuselage load across the spar carrythrough, but then again, I have no idea what I'm talking about.

-Rob
 
Wing Bolt Torque

I'm running into the same problem, helping a friend assemble his airplane, we can't find the wing bolt torque. Has anyone resolved this issue?
 
Write this down!

Finally found my copy of AC 43-13-1a/2a from 1988
Under rec. Bolt torque there is a table that lists
AN4 bolts 50 -70 inch/lbs
AN 7 bolts 450-500 in/lbs

NAS 1304 bolts 80-100 in/lbs
NAS 1307 bolts. 520-630 in/lbs

Nightflier, will you take a sharpie and write those values down where I have all the other important torques written down!!!!!! Thanks Sam!
 
I'm confused...

My copy of 43.13 (1998) doesn't have a table or list any values for NAS bolts. Also Van's torque table in Section 5 basically matches the recommended torque value table (7-1 on page 7-301) for fine threads.

So, is the torque value for the NAS close tolerance bolts different? Any one have a table they could post?
 
AC 43.13 is available digitally for free from the FAA website... I don't have a link handy because I'm on my iPad right now, but I've downloaded it a few times from them.
 
That's were I got my copy -- last time I downloaded it was just a few weeks ago.

43.13-1B Acceptable Methods, Techniques, and Practices - Aircraft Inspection and Repair dated 1998 and

43.13-2B Acceptable Methods, Techniques, and Practices – Aircraft Alterations dated 2008

-1B is the volume germane to this discusson and is generally the one that everyone is referencing when qutoing 43.13.
 
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Jerry,
Thanks for the link. Getting closer to an answer I think. Sooo anybody know if the wing attach bolts are tension or shear (I'm guessing shear)? Makes a 200 in-lb difference in torque on a NAS1307 bolt according to the chart on the link in Jerry's post. That's a pretty signifcant difference in my book and not something I want to get wrong.
 
The spar attach bolts are loaded in shear. Double shear, to be technically correct, with the spar sandwiched between the two center section blocks. Here's an example:

http://www.instron.us/wa/solutions/....com/search;_ylt=Al2l4ViBFF0Y4CexZKvRykObvZx4

Torque for shear.

So, I go to the trouble of searching for my old AC 43-13, finding the TORQUE that we've been using for years, give the torque range for everybody so they have it for posterity, and somehow that isn't good enough!
The table I got the torque values from are for steel tension nuts, the nuts that are called for are AN365! STEEL TENSION NUTS!
If you want to use AN364 shear nut torque values make sure you print that on the side of the plane so everybody who rides in your plane will know your plane has LOOSE wings!
 
If you want to use AN364 shear nut torque values make sure you print that on the side of the plane so everybody who rides in your plane will know your plane has LOOSE wings!

Yep, I'm sure my plane will fall out of the sky.

Torque for tension, won't hurt a thing. The bolts are not primarily loaded in tension, though. This is a shear load configuration.
 
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Thanks for your help Jon

So, I go to the trouble of searching for my old AC 43-13, finding the TORQUE that we've been using for years, give the torque range for everybody so they have it for posterity, and somehow that isn't good enough!
The table I got the torque values from are for steel tension nuts, the nuts that are called for are AN365! STEEL TENSION NUTS!
If you want to use AN364 shear nut torque values make sure you print that on the side of the plane so everybody who rides in your plane will know your plane has LOOSE wings!

Jon, Just a quick note to say that I bookmarked your answer right away. You are one of the "Go-To" guys that a lot of people on this site turn to for advice. I wanted you to know that not everyone second guesses your experience ....THANKS
 
Please accept my apologies for "second guessing" a moderator. Sorry, Jon. I have learned my lesson and will not attempt to help others from now on.

Surprised, actually, that such an indignant response came from a mod. Or maybe I didn't understand the tone of the response properly.
 
Indignation or Sarcasm? You decide...

Easy sometimes on these forums to mistake sarcasm ( like Jon's comment about loose wings) for indignation... Pretty funny I thought.
 
If only I could get the wing bolts in!

A few days ago I installed the wings on my 7A for hopefully the last time. I temporarily used some slightly undersized bolts to mount the wings. Well, yesterday I spent 6 hours replacing the temp. bolts with the close tolerance bolts. After a full day in the cockpit with a rachet and open end wrenches, I managed to get the top bolts (two big/two small) on each wing. I used a small amount of grease and racheted them in with a fair amount of effort.
The bottom bolts are in place but have a long way to go. With less space to work, I'm open for suggestions on how to get these installed. I was thinking about simultaneously using my rivet gun and an open end wrench to 'assist' in getting them in the hole.

Jim Diehl
7A
Lock Haven Airport, Pa.
 
Wing Bolts

I used a rivet gun - but be sure to pad the tip to avoid mushing the bolt heads and preventing a wrench to fit.
 
Jim, just did these on my 7A a couple of weeks ago, so the pain is still fresh in my mind. A couple of things I noted when doing mine:
1. Start from the outboard bolts and work inboards. Fully tighten each nut before moving to the next one. If you don't do this, you will not be able to get your wrench on the previous nut that you left loose.
2. It is not possible to torque most of these nuts with a torque wrench because of access and the fact that you can only rotate the bolt. And the prevailing torque of the bolt in its hole is very high, meaning the you are not torquing the nut to the required value. Just torque it until the prevailing torque spikes up which indicates that it is bottomed and squeezing, then turn another quarter turn.
3. I used crows foot wrenches with a 3/8" drive universal attached, then a 6" extension for all of the nuts. This was the ONLY combination which worked to hold the nuts out of many ways attempted. Note that you cannot TURN the nuts at all, the best you can do is KEEP THEM FROM TURNING while you rotate the bolt on the aft side. Some people use a flat screwdriver blade wedged against the nut to keep it from rotating, but I was able to use the crows foot wrench which is a little less ghetto I guess.
4. Several people reported using liquid nitrogen to cool and shrink the bolts. I found this to be unnecessary. A small hammer worked fine to tap the lubricated bolt shanks in without ridiculous effort.
5. When driving the bolts in, drive them slowly/carefully so that only 2 threads show on the fwd end. Then start the nut, drive a little more, torque a little, drive a little, then tighten completely. If you drive the bolt too far, you will not be able to get the nut on because of interference with the gear weldments.
6. After each bolt is in, get out of the airplane and take a walk. Shake off the cramps and start again on the next bolt. It took me all of 8 or 10 hours to get these bolts in and tight!
 
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Jim-
Trying to ratchet them in probably won't work. A rubber mallet and/or some taps with a hammer or the rivet gun that others have noted will probably be required. FWIW, my oiled bolts went in fairly easily a couple days ago, chasing out the drift pins one at a time. The rubber mallet sufficed for those and is consistent with AC43.13-1b where it discusses inserting close tolerance bolts. Only with one bolt did I need to use some stronger taps with the hammer. Could have used the rivet gun there, but same difference. As Noah mentioned, do pay attention to see if your wrenches will fit with all four bolts in at once. I didn't do that, but hadn't thought about it until now. I'll maybe have to grind a wrench down. Good luck.
 
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Jim,

Possibly too late for this but before installing my wing bolts I measured the diameter of each bolt with a micrometer over the length of the bolt and found some were slightly bigger in the area where the shank meets the threaded part. I carefully filed away this area to remove the bulge. From memory this mostly amounted to removing the cad plating locally. After this my bolts went in relatively easily. Obviously I would have preferred not to remove the cad plating but I think you would find that some cad plating is removed in this area anyway by all the turning, tapping etc when attempting to install the tight bolts. I also liberally coated them with the lubricant/corrosion inhibitor recommended by my local LAME (A & P).

Using the smaller MS21042 nuts on the lower bolts is an option, see my posts #16 and #18 http://www.vansairforce.com/community/showthread.php?t=34728

Fin
9A
 
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Long Thread......

I might have missed it in this thread, but my understanding is that the final torque is the sum of friction torque of the Locknut/fastener combination and the specified torque range of the normal free running nut. That is what I recall.
 
Also, these bolts are vastly on sheer force and no tension on the nut, so unless it is sloppy lose, how important is it to get them all right?

It is always important that bolts in shear are fully torqued up to their proper value for a couple of reasons:

1. The nuts are less likely to back-off if the bolt is properly prestressed.

2. Engineering analysis assumes that a certain percentage of the shear forces at the connection are picked up as frictional forces between the mating surfaces rather than purely by the shank of the bolt. But if the bolt is not properly torqued then there is insufficient frictional forces developed between the mating surfaces....that then reduces the safety margin of the bolt.

If it wasn't important for bolts in shear to have a torque value then they wouldn't have one.
 
...Engineering analysis assumes that a certain percentage of the shear forces at the connection are picked up as frictional forces between the mating surfaces...

That may be the case sometimes, but it is an unconservative approach and one that is far from universal.

Thanks, Bob K.
 
That may be the case sometimes, but it is an unconservative approach and one that is far from universal.

Thanks, Bob K.

On the contrary, using the proper torque values on bolts in shear is always the most CONSERVATIVE approach for a number of reasons (regardless of whether the design engineer assumes frictional forces at the connection or not).

I don't know that it's a good idea to be encouraging backyard aircraft builders to either undertorque or overtorque their fasteners and fittings.

The aim of my original post was to ensure that RV builders on this forum (very few of whom have any engineering background) do not make dangerous assumptions regarding the need (or lack of need) to apply the proper specified torque on all fasteners and fittings. It's just not an area that lends itself to "intuitive" decision making by laymen.
 
On the contrary, using the proper torque values on bolts in shear is always the most CONSERVATIVE approach...

I agree that using some reasonable torque value is better than using an unreasonable one.

However, I continue to maintain that assuming shear transfer through friction is not universal engineering practice. Especially for large heavily loaded joints such as wing attaches, the vagaries of surface condition, coatings and contaminants make determining the friction an iffy proposition at best, and besides those forces are dwarfed by the magnitude of the forces transferred through shear in the bolt shank.

Thanks, Bob K.
 
installing bolts

Thanks guys,

As I mentioned a few days ago, I was having a tough time installing the bolts. After reading some of your comments, I headed to the airport with rivet gun in hand. Well, with little coaxing, the bolts readily were tapped into place. Getting the nuts on the bottom bolts took a bit more time, but was doable.
Speaking of torquing, the top bolts are easily torqued due to good access. On the other hand, the bottom bolt torques will likely be a best guess. Too much unknown friction to torque from the bolt head and clearly a lack of access on the nut side.
With the bolts and nuts secured, this was a good weekend. Now I can move on to getting the aileron push rods and flaps attached.

Jim N891DD
7A
Based at Piper Memorial Airport, Pa
 
Too much unknown friction to torque from the bolt head and clearly a lack of access on the nut side.

Jim N891DD
7A
Based at Piper Memorial Airport, Pa

Put a torque wrench on the bolt head and you can easily ascertain (by trial and error settings) what torque is required to overcome the interference fit and start rotation of the bolt. Then add that figure to the prescribed bolt torque and the bolt can be reasonably accurately torqued from the head.
 
Regarding post #34

But not singling for any other reason except to ask this question.
If a person does turn the bolt in order to torque the nut doesn't that cause excessive wear on the bolt hole and possibly cause galling of the bolt hole walls?
 
But not singling for any other reason except to ask this question.
If a person does turn the bolt in order to torque the nut doesn't that cause excessive wear on the bolt hole and possibly cause galling of the bolt hole walls?

On the RV7A there is insufficient space to be able to torque (or even tighten) the nuts on the main lower bolts at the wing-to-centre-section joint. The best you can do is prevent the nut from spinning (and even that takes some ingenuity). So those bolt HAVE to be tightened/torqued from the bolt head. Vans calls for a washer under the bolt head to prevent the head of the bolt from damaging the centre section bulkhead during the rotation of the head (some people fail to put it on). It's always preferable to tighten the nut but in this particular case it isn't possible.

In this instance any wear on the bolt hole would be insignificant. Probably the biggest downside is losing the cad plating on the bolt thus increasing the potential for corrosion between dissimilar metals.
 
possibly cause galling of the bolt hole walls?

A little white lithium grease on the bolt (but not the threads, of course) will prevent that. Factor in the torque required to turn the head, of course.

A lot of the analysis of torque reminds me of when I was learning to drive. Our hands are supposed to be 10-and-2 on the steering wheel, but we eventually realize that 7 and 4 gets the job done too. :D
 
NAS 13xx Bolt versus AN3's

Over the weekend I discovered a broken AN3 bolt on the spar. It snapped off down by the threads just above the nut. I'm trying to figure out the torque setting, and now I see a discussion about NAS bolts. What's the difference between NAS bolts and regular AN3's?? I thought the spar was AN bolts ??
Am I wrong?
 
Over the weekend I discovered a broken AN3 bolt on the spar. It snapped off down by the threads just above the nut. I'm trying to figure out the torque setting, and now I see a discussion about NAS bolts. What's the difference between NAS bolts and regular AN3's?? I thought the spar was AN bolts ??
Am I wrong?

AN3 (3/16") bolts are VERY easy to overtorque. I use 25 INCH-pounds, and that is less than one flat past the "just snug" calibration in my right arm. I've never tried it myself, but a local builder said he was able to break an AN3 without it "feeling tight".

Fastners loaded in shear perform best when they "fill" the hole (like rivets;)), so the main wing attach bolts are close tolerance to "fill" the close tolerance holes in the spar and center section.
 
Ditto about breaking AN3 bolts without them "feeling tight". I was helping a friend complete his RV-8 and we were using a defective torque wrench. We snapped off 2 AN3s before we figured out the problem and believe me, they never did "feel tight". Reminds me of a time when I snapped off a valve cover bolt on a Ford. Them little bolts take a lot less torque than you would imagine.
 
NAS 13xx Bolt versus AN3's

thanks guys.

I discovered the NAS bolts are the same strength as the AN's, but are tighter tolerance and the AN's are to be used. Although apparently some builders will drill holes for the NAS bolts. Torque settings are typical AN-3 torque values
 
Torque for Wing Bolts

Finally found my copy of AC 43-13-1a/2a from 1988
Under rec. Bolt torque there is a table that lists
AN4 bolts 50 -70 inch/lbs
AN 7 bolts 450-500 in/lbs

NAS 1304 bolts 80-100 in/lbs
NAS 1307 bolts. 520-630 in/lbs

Nightflier, will you take a sharpie and write those values down where I have all the other important torques written down!!!!!! Thanks Sam!

Jon
Thanks for printing these torque values in Vans Forum. I'm doing my wings now and one google search sent me right to this. Much Appreciated.
 
I'll second that.

It's a shame the actual answer is buried in 4 pages of bickering...

True, but an additional shame is that people installing something as critical as spar bolts on an airplane go to an on line forum and trust random strangers for critical info rather than look it up themselves in the proper tech. documents.
 
Put a torque wrench on the bolt head and you can easily ascertain (by trial and error settings) what torque is required to overcome the interference fit and start rotation of the bolt. Then add that figure to the prescribed bolt torque and the bolt can be reasonably accurately torqued from the head.

As if to second Scott’s post, I think what Bob meant is to add, not the torque needed to start the bolt turning, but the torque needed to keep it turning (‘running torque’), to the final desired torque.
 
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