Working on the final fit of the wings and things and was wondering if it really matters what way you install the wing bolts? Meaning can I put them in from the rear forward? This would be super easy as compared to fwd aft. I understand that normal would be FWD to AFT.
Van's Air Force
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Wing bolt install
- Thread starter Chipper G
- Start date
D-Dubya
Well Known Member
Unless Van's states otherwise, fit the wing spar bolts in whichever way you can get them. You may have to give the bolts some love taps with a rubber mallet, so take swing room into consideration.
And yes, normal convention is from top to bottom and front to back. This allows gravity and airflow to help in the event a nut gets loose...at least in theory. If your wing spar bolts are falling out, you have bigger problems anyway.
And yes, normal convention is from top to bottom and front to back. This allows gravity and airflow to help in the event a nut gets loose...at least in theory. If your wing spar bolts are falling out, you have bigger problems anyway.
The bolts on my RV-10 took quite some effort to get in. Close tolerance bolts indeed! If you install them "backwards" the strength is the same, but yes, the risk is that they could fall out.
In the RV-10, that would take 8 stop nuts coming loose and falling off 4 large and 4 medium bolts, then the bolts which need a hammer to install and remove, working themselves out with vibration.
Bottom line is that it is unlikely that "backwards" installation could pose a risk, but, obviously, strange things can happen. Maybe apply torque seal to all the nuts and add a frequent inspection reminder? The minute any bolt shows signs of breaking the seal, it's a super high priority item.
In the RV-10, that would take 8 stop nuts coming loose and falling off 4 large and 4 medium bolts, then the bolts which need a hammer to install and remove, working themselves out with vibration.
Bottom line is that it is unlikely that "backwards" installation could pose a risk, but, obviously, strange things can happen. Maybe apply torque seal to all the nuts and add a frequent inspection reminder? The minute any bolt shows signs of breaking the seal, it's a super high priority item.
I can't really say this for the 8 but some models such as 6A, 7A and 9A the bottom bolts can only go from the aft to front so I would think it will not matter unless one way is easier than the other.
It will help if you leave the bolts in a freezer or even better put them in dry ice with 90% alcohol right before installing them. The cold will shrink them a bit to be installed easier but still will take some effort so don't expect them to be just pushed in by hand.
Good luck and congrats
It will help if you leave the bolts in a freezer or even better put them in dry ice with 90% alcohol right before installing them. The cold will shrink them a bit to be installed easier but still will take some effort so don't expect them to be just pushed in by hand.
Good luck and congrats
MIKE JG
Well Known Member
Lol. Very true!
The top bolts can be installed in either direction. The bottom bolts can only be installed from the rear because the floor from the spar carry through to the gear tower is slanted upward and the bolt will not clear. You will be hammering the bolts using a mallet or something similar and installing from the rear gives you more room to swing that mallet. If everything is lined up perfectly, the bolts will go in easily for the first inch before friction takes over and you have to use more persuasive power.
A ROT for aircraft fastener install:
Threads point down or rearward.
More importantly if the drawing specifies a direction, you should not be deviating from that. The reasons for specifying orientation on the drawing may not always be obvious. There are related case studies written in blood.
Scott Hersha
Well Known Member
I don’t think it really matters which way, as long as other parameters are followed - tight fit on the close tolerance bolts, new lock nuts, no lube on the threads before torquing. And as others have said, if you have an “A” model, some bolts can only go in from back to front. On the two RV8’s that I’ve built (both TD models) my bolts went in from front to back. I had to get creative with some wood pieces and a ‘soft’ brass rivet set on my rivet gun set at low pressure on a couple of them while driving them in, but then the nuts were easier to install, and if I ever had to remove them, it was much easier - an important consideration if you ever have an off airport landing. During initial wing fitting I used the hardware store bolts ground to a point. Knowing I’d have to remove them dictated which way they would go in. When I installed the new final assembly close tolerance bolts, I used some Boelube on the shank. Make sure you don’t get any on the threads. I cleaned the threads with a solvent and alcohol to make sure they were dry before torquing the nuts. I’ve not heard of nuts backing off on RV wing bolts, and then the bolts sliding out. Not saying that it couldn’t happen, but these bolts are loaded 100% in shear. If you see any movement in the hex head end, or the nut end (whichever end you can see) it’s cause for concern.
BillL
Well Known Member
Rabbit hole . . .
Here is a direct reference https://vansairforce.net/community/showpost.php?p=989407&postcount=2
There was a big discussion with Bob Axsom, Scott McDaniel and quotes from Ken at Vans (2006) as to whether the torque needed to be NAS or AN - Ken said the AN is good, but the high end of the spec is ok too as it is close to the NAS specs. Lots of discussion about the nut being the main factor.
I did not find the NAS controlling document for torques, but did find a table of the NAS torques. They are equal to Jon Thockers below BUT . . . the table clearly identifies the NAS torque Jon quoted as tension torque. This is not a tension application, so the soft support by Vans (Ken Krueger in the day )on the torque falls back to standard AN torques as being acceptable. That AN torque is listed in the chart below.
Here is Jon Thockers post on same - he lists the NAS torques too.
Here is a direct reference https://vansairforce.net/community/showpost.php?p=989407&postcount=2
There was a big discussion with Bob Axsom, Scott McDaniel and quotes from Ken at Vans (2006) as to whether the torque needed to be NAS or AN - Ken said the AN is good, but the high end of the spec is ok too as it is close to the NAS specs. Lots of discussion about the nut being the main factor.
I did not find the NAS controlling document for torques, but did find a table of the NAS torques. They are equal to Jon Thockers below BUT . . . the table clearly identifies the NAS torque Jon quoted as tension torque. This is not a tension application, so the soft support by Vans (Ken Krueger in the day )on the torque falls back to standard AN torques as being acceptable. That AN torque is listed in the chart below.
Here is Jon Thockers post on same - he lists the NAS torques too.
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Yeah, maybe on small stuff, but I don't think it matters for a big a$$ spar bolt. I don't think you can count on gravity or wind pressure to hold in a wing spar bolt. You lose the nuts, you're going to have a bad day, regardless of bolt orientation.
Hey Larry, the main point was missed. I stated ROT in my slight drift there. The main point was
If the OEM bothers to show fastener installation in a certain orientation, follow it. If unsure or questionable, get clarification.
There could be reasons that aren't obvious e.g. later assembly/fab could limit tool access, etc. If it's something with a low profile like a clevis bolt, more scrutiny should be given. It was specified for a reason.
There are many associated instances/accidents where related mistakes have had serious consequences, unfortunately. One of the earliest that I remember was an early USAF jet (F86 Sabre??). The tech placed some bracket bolts in per convention (threads down) ignoring the engineering releases that specified otherwise. He assumed those were incorrect. Under the high drag load of jet speeds, the wings flexed enough where the ailerons would bind on the improperly installed fastener. The resulting constant roll made survivable ejections impossible. Extreme example I know, but follow the OEM releases.
If the OEM bothers to show fastener installation in a certain orientation, follow it. If unsure or questionable, get clarification.
There could be reasons that aren't obvious e.g. later assembly/fab could limit tool access, etc. If it's something with a low profile like a clevis bolt, more scrutiny should be given. It was specified for a reason.
There are many associated instances/accidents where related mistakes have had serious consequences, unfortunately. One of the earliest that I remember was an early USAF jet (F86 Sabre??). The tech placed some bracket bolts in per convention (threads down) ignoring the engineering releases that specified otherwise. He assumed those were incorrect. Under the high drag load of jet speeds, the wings flexed enough where the ailerons would bind on the improperly installed fastener. The resulting constant roll made survivable ejections impossible. Extreme example I know, but follow the OEM releases.
I almost always follow the designers guidance and wouldn't suggest otherwise. Only stated that the ROT of threads back likely doesn't likely provide any additional safety for spar bolts, unlike a rudder cable attach bolt where gravity may keep it in place a bit longer with threads down.
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claycookiemonster
Well Known Member
Another thing to consider, assuming the situation allows, is which side of the spar is easier to see, and will be seen more often. Confirming the head of a bold still is still in position is good. Confirming that the nut hasn't backed off by referencing torque seal would be better.
