---
title: Wing Spars, Wing Attach and Spar Web
description: Wing Spars, Wing Attach and Spar Web. Builder questions and answers from Van's Builder Technical Support.
---
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October 5, 2026
# Wing Spars, Wing Attach and Spar Web
## Builder Tech Support answers on wing spars, wing attach and spar web
This article collects Builder Technical Support answers on wing spars, wing attach and spar web.
### Common wiring harness routing through the spar
The pre-built common wiring harness (WH-000125 and similar) ships with connectors installed at both ends. To route through spar holes and brackets, the standard practice is to de-pin one end, route the wires through, and re-pin. Do not enlarge spar holes. If you are uncomfortable de-pinning, the harness vendor (e.g., SteinAir) can build the harness with one end open for routing.
### RV Wing Spar - Inspection, Damage, and Build Questions
The wing spar is the most safety-critical part of the kit. This article covers what to do when a spar arrives damaged, how to handle mismatched spar serial numbers, and the most common build questions.
### Spar serial numbers do not match the packing list
If the spar serial numbers stamped on your spars do not match the numbers on your packing list, this is usually a packing-list or green-tag error at shipping - not a structural concern. Spars are not matched sets; any left wing spar will work with any right wing spar regardless of date of manufacture. Email Builder Tech Support with your builder number and the actual spar numbers you received, and your account will be updated to reflect the correct numbers. No other action is required.
### Minor bends found when unpacking spars
Do not attempt to straighten a bent spar with pliers, a press, or any field method. Even small bends in spar flanges can affect structural integrity. Photograph the bend with the spar on a flat reference surface so the deflection is visible, include a tape measure for scale, and send to Builder Tech Support with your kit number. Engineering will evaluate the photos and either approve a field repair, request the spar be returned, or ship a replacement.
### Surface scratches and dings on the spar
Light surface scratches that do not penetrate the cladding (the protective alclad layer) can typically be dressed with Scotch-Brite and touched up with primer or paint. Anything that looks like a deeper gouge, dent, or anything you can catch a fingernail in should be photographed and sent to Builder Tech Support for evaluation before continuing.
### Factory rivet in wrong hole
If a factory rivet was installed in an incorrect hole during spar manufacture, photograph the rivet location with a clear view of the surrounding hole pattern and email Builder Tech Support before drilling out anything. Depending on the hole and the structural role, the resolution may be to leave the rivet in place and install a new fastener in the correct hole, or to drill out and re-rivet. Do not assume.
### Significant shipping damage
If a spar assembly arrives with damaged rib attach angles, web damage, or destroyed rivets, do not move it from where it was unpacked. Photograph the as-received condition including packaging if available. Email Builder Tech Support immediately. Significant spar damage from shipping is handled as a freight claim and the spar will be replaced.
### Recent Builder Support notes
Two things come up repeatedly on spar work. First, plan page cross-references are not always right: a page belonging to another model's plan set can appear in your manual through an engineering copy-and-paste error, so if a referenced page does not match your airframe, check it with Builder Tech Support rather than working to it. Second, doublers sometimes need to be shortened to fit and the plans do not always give an instruction for that; trim to fit and ask if you are unsure.
On torque, note that castellated nut locations are called out specifically. Standard torque values apply at some castellated nut locations and deliberately do not at others, so follow the callout for that location rather than applying a single value everywhere.
### Hinge doubler with extra holes (E-00001 series)
If E-00001A/B have four holes that align with the spar and four additional holes that do not match anything on the spar or E-610PP, the extra holes are intentional - they align with structure that gets installed later. Continue per plans and verify alignment when the matching structure is fitted.
### F-704 Center Section Damage
The F-704 is the main center-section spar that transfers wing loads into the airframe. Van's will not endorse cut, shim, or doubler repairs on the F-704 — it must be replaced. If your F-704AFT is on backorder, work with the Orders team to expedite. There is no approved field repair for this part.
### Inspection Procedure
The bulletin instructs drilling the flange tooling holes in the end rib to 7/16" to allow borescope access along the rear spar. You may open the tooling hole to a slightly larger diameter (for example 8 mm) to accommodate a specific borescope probe — confirm any deviation with Tech Support first. Take multiple photos along the rivet line, including overview shots of each side and close-ups of any features that look like potential cracks.
### Crack in the HS Rear Spar at the Outboard Hinge
For a confirmed crack at the outboard hinge of the HS rear spar, only the outer hinge needs replacement — not both hinges unless both are cracked. This is consistent with SB-00036 guidance. See the SB-00036 article for inspection details.
### Deep Scratch on the Wing Rear Spar
If you discover a deep scratch while removing vinyl from a wing rear spar, sand it down carefully and measure the resulting thickness. The general rule of thumb is up to 10% material removal is acceptable on alclad components, but location matters — scratches immediately outboard of a rib attach point are more concerning than scratches in midspan. Document the as-sanded thickness with a micrometer, photograph the location, and send to Tech Support before riveting.
### Rear Spar Misalignment on a QB Build
For a partially completed (e.g. 80%) QB-6 wing where the rear spar does not line up to the plans during installation, the cause is usually accumulated drilling tolerance from the QB build phase. Photograph the offset, capture measurements, and send to Tech Support. Repair options range from shimming to controlled redrilling, depending on the magnitude.
### SB Compliance Guidance for Rear Stabilizer Spars
For owners getting mixed messages on whether to drill an inspection hole on the rear stabilizer spar, refer to the applicable Service Bulletin (commonly SB-00036) and follow the bulletin's procedure exactly. Van's website lists the current bulletins. Photos and video do not currently substitute for the written bulletin's procedure.
### Wrong rivet hole used on the main spar
If you accidentally installed a rivet in the wrong hole on a main spar (for example, a hole that should have been a bolt location), drill out the rivet, and contact Builder Tech Support. The repair typically involves a new rivet in the correct hole and a bolt in the originally-intended bolt hole — but main spar rework is not a do-it-yourself call. Tech Support and Engineering will sign off on the specific repair before you proceed.
### When to replace vs. repair
Replace any tank skin or rib with cracking, severe dimpling errors, or damage in load-bearing locations near the spar. Cosmetic dents on flat skin areas far from rivet lines are generally acceptable. Proseal-and-patch repairs are appropriate only when we've confirmed the location is not structurally or aerodynamically critical.
### Overview
Wing attachment is the highest-consequence hardware install in an RV build. If you're working through wing fit, bolt substitution, or you've found corrosion or interference, this article covers the recurring questions Builder Tech Support receives.
### Corrosion on spar bolts (quick-build wing)
If you open a quick-build wing crate and find corrosion on the spar bolts, do not clean and use them. Send photos to Builder Tech Support with your kit/serial number and Van's will arrange replacement hardware. Wing-attach hardware is too critical to attempt to refurbish.
### Van's Tech Q&A: RV-12 Rear Wing Spar Play
*Copied from Van's Aircraft Tech Q&A on 2026-10-01. Source: [RV-12 Rear Wing Spar Play](https://www.vansaircraft.com/faq/rv-12-rear-wing-spar-play/).*
The latest documentation and procedure for examining RV-12 rear spar “play” has been moved to the RV-12 Maintenance Manual, the latest version of which is available in the
[*Support \> Service Information and Revisions*](https://www.vansaircraft.com/service-information-and-revisions/)
section of this web site.
### Van's Tech Q&A: Wing Incidence Drilling
*Copied from Van's Aircraft Tech Q&A on 2026-10-01. Source: [Wing Incidence Drilling](https://www.vansaircraft.com/faq-technical-builder-items/wing-incidence-drilling/).*
**DRILLING THE WING — SIMPLIFIED**
1. Don’t put in all of the wing attach bolts right away! You may have to remove each wing a couple of times in this process. Just put in four bolts in a square pattern for each wing. Don’t use the good bolts! Put in hardware store variety and grease them and the holes in the spar to protect the spar and facilitate insertion.
2. Once the wings are TEMPORARILY installed, level the fuselage laterally. You want the two wings to be level left to right. Don’t simply rely on placing a level across the longerons (they are hand bent and may have slight errors), put a level on the top of the main spar center section as well. If the two agree, move on to the next step, if not, average the two. A ½” or less height error at the wingtip is close enough. Now check the forward sweep! Hang 2 plumb bobs on each wing, one at the tip and one at the root (tank area). Then stretch a single long string across the front of these four plumb bobs. If there is no or minimal (get real, less than ½”) sweep fore or aft, then move on to #4 below. At the same time, triangulate from each wingtip to some center point on the aft fuselage. The two measurements should be the same (get real, within ½” or so will be fine).
3. If there is a sweep or triangulation problem STOP. The common reasons are:
1. The rear spar structure that sticks out of the fuselage is comprised of two pieces of 1/8” aluminum bar. One piece ends up on the front side of the wing rear spar stub and one is on the backside (where you can see it). The forward piece OFTEN is too long and hits the wing root rib flange and prevents sufficient insertion of the rear spar stub into the “hand” of the fuselage (thus producing forward sweep). If so, then remove the wing and cut off the minimum amount required to correct for the sweep error. In general, if the tip of the wing is swept forward 1” then trim 1/8” to ¼” from the end of the bar.
2. Sometimes the culprit is the wing rear spar stub! If it is running into the spacer block in the “hand” of the fuselage, and that is all that is wrong, then remove the wing and trim off as in “A” above.
3. Sometimes it is both problems! Just be sure what the problem is before you get too handy with the trimming!
4. If all is OK, then start the process with the bubble level of setting the wing incidence. DON’T DRILL THE HOLE YET. There is more to this than you think. The CRITICAL part of incidence is not so much the amount, but rather that both wings have the same amount. Other factors to assess are the following:
1. The edge distance of the rear spar attach bolt is PARAMOUNT. 5/8” from the center of the hole in ALL directions in ALL of the material it goes through is the first consideration. Take a good look.
2. It was the hope of the designer that the flaps might fit once the wing is installed! If you look at your flap, you will see that it has a bottom skin that seems to want to go under the fuselage belly skin when the flap is UP. It is really nice if this skin just kisses the bottom of the fuselage. Try putting the flaps on.
3. If you have edge distance met, the flaps fit well, the sweep is OK, the triangulation is good, and the incidence is set, TAKE A BREAK. Move off and away from the airplane and take a look, you are very close to drilling a PILOT hole (say 1/8” or so) in the rear spar! IF you’re ready, go to instruction #6.
5. The only real problem you may have is that the incidence does not allow one of the requirements above to be met. Try some of the advice below:
1. THE FLAPS ARE TOO HIGH TO GO UNDER THE FUSELAGE AND YOU CAN’T RETRACT THEM TO AN “IN TRAIL” POSITION. There are a couple of solutions to this… one is to change the incidence of the wings (lower the rear spar until they will). To a degree, this is OK but of course you must retain that critical edge distance for the attach bolt. IF you can retain this distance and not change the incidence too much (say a degree?) then what will happen? The horizontal stabilizer may need to be repositioned. HOW, and HOW MUCH? Clamp the wing spar in the new location, put Van’s block of wood under the level, and raise the tail of the fuselage until the bubble centers. Now check the horizontal for level fore and aft. Very likely you can’t measure the change from its original position. IF you can and all else is OK then consider changing the spacer under the front spar of the horizontal to correct it.
2. Another solution is to simply cut off the skin that would have been under the fuselage. Now the flap will come up in trail and you will simply have an uncovered hole showing in the fuselage bottom where the actuator push rod will come out (unsightly but no big deal).
3. THE FLAPS ARE TOO LOW WHEN RETRACTED FOR THE BOTTOM FLAP SKIN THAT UNDERLAPS THE FUSELAGE TO TOUCH THE BELLY. Not a big deal but if everything else looks good and you don’t want to raise the rear spar of the wing (thus reducing the wing incidence and maybe losing the PARAMOUNT 5/8” bolt edge distance) then you can simply bend the lower flap skin up a little until it “kisses” the bottom of the fuselage.
6. Get ready to drill the hole! The toughest part of this is getting the hole SQUARE to the surface of the material. Everything there in the rear spar attach area is at a different angle to everything else. It is very hard to hold a drill perpendicular by eye! Make a drill guide! Find a block of iron or aluminum at least one inch thick and two inches square. On a drill press, drill a 1/8” hole through the center of the block. Now you can clamp the block to the rear spar of the wing and it will help to assure that the drill bit penetrates the surface perpendicularly.
7. Drill the hole to 1/8” diameter first! Put a cleco in and check everything again, step back away from the plane and check again! Only then can you safely drill the hole out to the correct size. A nice hole can be achieved by first drilling an undersize hole and then, using a reamer, enlarge it to the final size.
8. During all of the above setup and machinations, DON’T FORGET the wing root fairings. They can be marked and drilled during this fit-up stage. The belly skin of the fuselage can be marked and its hole locations identified during the above processes as well. Also, look at and identify the transition points for the fuel lines and vent lines from the tanks into the fuselage. This is a great time to finish these details. How about the pitot line? Time to take a break!!
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