Jeff Vaughan

Jeff Vaughan

Well Known Member
I am just about ready to test fit my wings with the fuse. I am concerned that I can not get a bolt through the wing spar fuse holes only on the bottom row. I have test fit with both close tol. bolts and hardware bolts. The bolts go into the top holes but will not even start to go in the bottom holes. I talked to Vans about this a few months ago and they said there is no way all the holes were not the correct size. Now that I am about to mount the wings I am revisiting. Has any one else had this problem. I will call Vans tomorrow again. I was not satisfied with their answer a few months ago. I had a machinist look at the holes and he agreed that there is no way the bolts were going to fit. He suggested reaming to the correct size. Just wondering if anyone else has experienced this.

Jeff Vaughan
 
Jeff,
Have your machinist measure all the holes, maybe some one did goof.
I fit my wings to fuse a couple days ago using grade 9 bolts and they fit tight but they all fit. use some lube on both the spar and the bolts. my spar was quite snug also!
Good luck
Frank
 
Holes too small

Jeff Vaughan said:
The bolts go into the top holes but will not even start to go in the bottom holes.
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Can you post a photo? It does sound amazing that this type of error would occur. If you do end up needing to ream, I would spend a lot of time with Van's discussing it. You'll probably want to ream with the wings on, so you get a nice hole through the spar box and the spar. As I understand it, this is the way it is done at the factory. Of course, they don't have the fuselage all around it to get in the way! Good luck.
 
What's the possibility of any primer or paint having ended up in those holes?
They are "precision" fit after all, and just the thickness of a primer would give you fits. Also look for a burr on an edge that would do the same thing.
 
I would certainly revisit your installation techniques before reaming those holes! I'm not saying it is impossible, but seems extremely unlikely that the factory somehow undersized those critical holes. It seems likely the factory used the same reamer and tooling application for both the top and bottom holes. First off, make certain no primer overspray is inside them. Surely, your machinist friend has a set of ball gauges and a micrometer in his tool box. Have him verify the correct diameters once and for all. If correct......consider this idea.... though I really cannot comment with certainty because of unfamiliarity with the design. You say you can get the top bolts in but not the bottom bolts. Have you tried loading or unloading the wings, the idea being to generate enough of a flex to get the bolt holes to line up? Another alternative. Try inserting an inboard bottom bolt first, then a top outboard bolt etc.etc. A technique used especially with close tolerance holes is to keep the bolts frozen until just prior to insertion.

Rick Galati RV-6A "Darla"
 
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My plans say go ahead and ream

Regardless of what the company says, they do make mistakes. I can identify several in mine. When you run into them, you just have to work through them and contacting Van's is an important part of the process. If there is a known error they will usually tell you but they deal with a lot of very inexperienced people every day that make a lot of mistakes. They are predisposed to expect builder errors because the vast majority are builder errors. Usually they listen kindly and try to give you the needed help to work through your current problem. It doesn't take long before you become your own best problem solver and you develop the judgement to proceed. The danger is that you make a judgement call that compromises safety. I made one of those with the aileron mounting bracket installation to the rear spar where the factory had drilled 4 holes in one side of the interface (spar or bracket - I can't remember which) and 5 in the other. As I always did when running into these things I contacted the factory and told them the problem and my fix. In this case they said "Oh yes we know about" that and the fix involved drilling over size holes in the top and bottom locations to pick up the total range of the mismatch and install screws inplace of rivets, add one hole in the four hole part to allow installation of the proper rivet for this application and install rivets in the other locations which were properly aligned. The factory sent me a kit containing the screw attachment hardware. I had already made a fix that was not adequate but fortunately the factory fix eclipsed my deficient fix. Note that I called them and learned of the known error and fix before any attempt was made to notify me the builder. A similar situation occured with improperly made elevator horn weldments. I really like Van's Aircraft and the people that work there but you do have to watch out for company errors as well as your own.

In your case the bolts wouldn't go in the free standing spar bolt holes so this is not a case of preloading the interface and causing misalignment, etc. The bolts simply do not fit! The fact that you got them in the top is a clear indication that these similar holes were not prepared the same way. A guess is they had a lunch break and an operation on the bottom holes was missed but the cause is unimportant to you in builder's isolation.

My plans book says: "If the bolts are just too tight, careful work with an expansion reamer and clean the holes sufficientlyto let the bolts fit. DO NOT remover too much metal -- the reamer should be adjusted so that only fine, dust-like, particles are removed. This, and coating the shanks of the bolts with lubricant (Boelube, Loctite #771, or something similar) will help them tap home with the proper fit."

This is after a paragraph that says "These fit so tightly that they must be driven in by tapping them with a hammer." and "A large C-clamp used as a press also works well." and "Any paint, primer, or slight mis-alignment of the holes will require excessive force to insert the bolts, so cleaning the holes is essential."

Ream the holes as required to get the job done is what I would do.

Bob Axsom
 
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Before doing anything, I'd try to fit the bolts into each part individually. That'll at least tell you if the problem is a wrong hole size or incorrect alignment.
 
I have not put the the wing in place yet. I am only test fitting the open spar box holes. Calling Vans today ! Will keep you posted.

Thanks for your help.

Jeff vaughan
 
Don't have specs in front of me, but

I was a structures engineer for Boeing many moons ago. I don't have the exact specs in front of me but these holes are probably "transition fit" holes, may be even interference fit. Before you START to blame Van or REAM holes. DON'T ream holes until you call Van's. This tight fit is CRITICAL for even load transfer and fatigue. Trust me I know.

First the bolts have tolerance and the holes have a tolerance, so they may be at the tight end (max interference) of the acceptable fit range. Also if you did prime them you will have affected the fit. If you must prime or want to add extra protection to the bolts cad plate, then install them "WET". Which means prime them and install them with wet primer right away.

This tight fit is the reason people use undersized pins and hardware bolts for initial or temporary fit up. These bolts take some effort to fit. You DO NOT want to install and remove the actual bolts multi time for test fits. It is best to use the structural bolts for a one-time final installation. If you want to test fit use undersized pins for test fit-ups.

If you don't have micrometer you can get a decent digital one for $20-$40 from harbor freight. Check the bolt dia and hole dia. You can check bolts to see which ones are smaller for the harder to fit holes. Nothing has a +/- 0.0000 tol, the fit will vary from tight to very tight.

I think your situation is normal but you don't give any numbers. Again don't ream them until you measure and talk to Van's. Chance of the holes being not to the proper size is slim. However if the holes a loose, you better look into it.

Cheers George
 
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My -6A QB was not even close with the wing mount bolt holes and neither were they on my friend's -6A QB of the same vintage. There is no way that these were drilled in company together with the center section. We're both machinists and both had to ream every hole. Took about 6 hours. I didn't consult Van's. After 3 hours of frigging around with round nosed, .005 undersized bolts to try to align and with the wings jacked in many different positions, there was just no way the CT bolts were ever going to go in even with a sledgehammer. The factory certainly made plenty of mistakes back then, some pretty major. Instrument panel angle in plans way wrong, 11 missing dimples for fuel tanks in spars, fuselage contours 3/8 difference side to side, baggage floor skins off 5/8 inches, wing airfoil template off 3/4 inches, I could go on. You just have to work through them. My new -10QB is wonderful so far so that is all now mostly repressed. Once you fly it, those bad memories fade fast!
 
gmcjetpilot said:
This tight fit is the reason people use undersized pins and hardware bolts for initial or temporary fit up. These bolts take some effort to fit. You DO NOT want to install and remove the actual bolts multi time for test fits. It is best to use the structural bolts for a one-time final installation. If you want to test fit use undersized pins for test fit-ups.
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I believe you. I wish Van's had said that in the instructions. Oh well, too late now (for me).
 
To clarify - I was trying to test fit the hardware bolts when I found this problem. The upper 1/4" holes the hardware bolts can be slid into with very slight pressure. The bottom 1/4" holes are the problem. The threads hang up in the hole. The bolt will not go in.

I did talk to Vans today. They have asked me to try to photograph the holes in order to figure out what the interference is. I have used mirrors and have not been able to see any visable problem. The holes are just smaller than the others. Vans did seem concerned, miffed but concerned. I am to call back tomorrow with my photo investigation completed.

Jeff Vaughan
 
The Plans Book from Vans calls for reaming

I spent days beating those GD bolts in the spars and after so long the timid do-gooder approach goes out the window. They don't fit and Van is not going to send a tech rep out to make it better. You either finish putting the thing together or turn into butter. The wording of the manual from Van's that I quoted earlier acknowledges that sometimes the bolts simply will not go in and in those cases you have to ream the holes. You can run stress analysis until your computer expires but eventually the holes have to be made compatible with the bolts. Wishing Van's did it won't get it done and you can believe even the most sophisticated manufacturers have hole size squawks when parts go through detail inspection. Van's does a very good job and they are getting better.

Bob Axsom
 
I think Jeff is going about it the right way. Figure out what the problem is, confirm what you think the problem is and THEN do what you need to do. This is not a time to go charging into your solution like the happy warrior.

Most of the time on this kit, when things haven't fit, it's been something _I_ did wrong and the one thing I've learned -- I guess this is the education part of homebuilding -- is take your time and do it right.

In the end it very well may be the holes need to be reamed but it's not our wing spar, we can't see it, our advice is cheap, and there's no consequences to us if it's wrong.

Jeff, keep doing what you're doing to diagnose the problem and let us know what you find.
 
Relative to my slow build RV-6A. Other than the series of close tolerance bolts that join the two wing spars together through the upper and lower centerline steel splice plates, most of the remaining holes are drilled for .1875 (3/16") bolts. I found it very interesting that not only was I able to insert the kit supplied AN3 bolts through them.....at times with some difficulty.....but accurate ball gauge measurement of those hole diameters proved they were factory final reamed to a diameter slightly larger than .1890. I agree, this area of assembly is no place to play the happy warrior. Investigate all avenues of possibility before you start reaming pell mell.

Rick Galati RV-6A "Darla"
 
An AN-3 bolt has a diameter of 0.186 to 0.189 inches.... you could first try measuring your selection of bolts and using the ones at the lower end of the tolerance in the tight holes before you ream anything...

gil in Tucson
EAA Technical Counselor
 
Well if it's like mine, I could fit about 6 bolts in gently tapping with a plastic hammer. Some of the other holes were misaligned up to .015! I didn't like to ream but there was no other practical solution. I would not be worried about bolts slopping around after reaming at there are about 40 bolts going through the spar and I had to tap each one in. Once these are tightened, there is no way anything is going to move.

I could never figure out why some bolts went through and others were so far off. My friend's was about the same as mine. Not helping the matter is the fact that some bolts were .0005 to .001 oversized. So much for aircraft hardware accuracy. I had to use .001 over reamers in some holes. I was not too happy about all of this. I think the maual said something like- "simply insert the bolts through spar and center section as they are drilled in concert" Really?
 
It's got to fit somehow

rv6ejguy said:
I would not be worried about bolts slopping around after reaming at there are about 40 bolts going through the spar and I had to tap each one in. Once these are tightened, there is no way anything is going to move.
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Well I agree not to worry and the RV-4,-6 with 40 bolts and steel center line spice is plenty overkill. You could take a few bolts out and it would still be OK. However the new generation RV-7,-8,-9 wing joint is not as overdone but still plenty strong. However ideally you should have the same fit on all joints. For an ultimate load condition it will not matter as the load will "redistribute" to all holes. The tight holes, which are taking more load, start to yield the loose holes will start to go to work. For normal loads it is possible that bolts in the loose holes are doing nothing, which causes slightly higher loads on the tight holes for normal loads. This really is not a big deal except in fatigue life. I am guessing we won?t live long enough or fly enough in two or three lifetimes to reach the fatigue life of the wing body joint, even with a few loose bolts. So don't get too worried or paranoid, not every hole in a Boeing 747 is perfect either.


rv6ejguy said:
I could never figure out why some bolts went through and others were so far off. My friend's was about the same as mine. Not helping the matter is the fact that some bolts were .0005 to .001 oversized.
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The thing here folks is we are using plan ol AN bolts in tight fit holes. They are really for clearance holes (net to slight clearance). High tolerance bolts and Hi-loks for transistion/interferance fit cost much more. Also to get true high tolerance joints you almost have to ream the parts in assembly. So using normal AN bolts with their large allowable tolerance can cause a fit problem. If you try to reduce the bolt diameter by sanding the finish off you will remove the Cad plate, which protects against corrosion. However jamming it in a hole too small for it will peal and scrape the Cad off anyway. I am not saying to ream the hole or play with the bolt, but use the best situation you can and match the bolts to the holes. Just be smart about it. You may have 90% of the holes lineup and only 10% need some finesse, but if you fit one of the 10% bolts up first you may end up with 90% of the holes not lining up.

If you screw up you can get oversized "repair" bolts that are a 1/64th or 1/32nd oversized. They are hard to find but they make them. Of course you need a special reamer also. This is done at Boeing all the time when holes are buggered-up.

I agree computer analysis is not going to help, you need to put parts together. Bottom line make it fit as tight as possible, make round holes, no burrs or sharp edges and go-slow. I am not sure if dry lube (like Boeing Lube) would help, but really you need to have 3 things: A straight hole thru all parts (no miss alignment), the proper hole diameter for the bolt (and it's tolerance). If not get a bigger hammer. :D Cheers George

Cheers George
 
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a little tight...

A while back the Air Force had a few problems with the gear breaking on the new C-17s. A possible factor could have been from the factory workers who simply used a 'bigger hammer' to make an out-of-tolerance large inner part fit into an out-of-tolerance small hole. Of course, the gear is made of some very high-strength, but very brittle alloys which are completely different than the RV?s aluminum spars, but my non-engineer mind says there could be a similar issue here...but then again, I've been wrong before...

Here?s a picture?the red is simply grease.

 
Spar holes OK!, Plates misaligned

Here is an update.

After a thorough evaluation using ball gages it was determined that the holes in the spar box are the correct size. The measured .2495. The hardware bolts that would not go in the holes measured .2475.

So you ask why wont the smaller bolt go into the bigger hole ??

The outer plates that are riveted to the meaty portion of the spar are ever so slightly missaligned. I inserted the ball gage into the hole and was not able to remove the gage when I got to the outer plates. Vans told me to go ahead and file the outer plate interferance.

Ready to move ahead !!!

Thanks for all the responses
Jeff Vaughan
 
Jeff Vaughan said:
Here is an update.

After a thorough evaluation using ball gages it was determined that the holes in the spar box are the correct size. The measured .2495. The hardware bolts that would not go in the holes measured .2475............................

Jeff Vaughan
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Jeff,

Thank you for providing us with your most valuable feedback. I'm sure you will agree most people were correct in urging you to explore all avenues before charging in and reaming those holes! Tis far far better to have filed away a small portion of the outer plates for clearance than what would have otherwise occured if you compromised the integrity of those all important spar holes. At risk of repeating myself, I urge all builders to invest in a micrometer and if the occasion arises, to borrow or buy a set of ball gauges. Most builders will discover good use for a micrometer time and time again during the building phase. Twenty years from now Jeff, you'll be that much more comfortable tossing about in moderate to severe turbulence knowing that you did not risk compromising the designers calculations and potential service life of the main spar. Good luck and happy building!

Rick Galati RV-6A "Darla" 38 hours
 
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