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Wing to Fuselage Intersection Fairing Attach - Better Way Than Per Plans?

gmcjetpilot

gmcjetpilot

Well Known Member
Wondering if there is a better way or alternative, and what others have done.

PER PLANS: The intersection fairing is metal strip (and rubber seal) that wraps around the inboard wing, over top of wing (wing walk area), around the leading edge (wing tank). A second short piece is on bottom wing skin (and rib) like on top, Both top and bottom wing skin/rib attach use the same nut plate & screw call out, which is where I want to deviate from the plans.

The wing skin areas top and bottom, per plans call for using a K1000 nut plates, and AN509 now MS24294 dash 8 screws. The nut plates are attached with typical -3 rivets drilled through both skin and rib and machined counter sunk in skin (as I read plans). OK. The small gripe is the #8 screw head countersink depth is 0.069". Since the skin and ribs are already together at this point (can't dimple), so you have to MACHINE COUNTRSINK. Skin is 0.032. Rib is 0.040" I think. So the hole in skin is beyond knife edge and rib knife edged on the bottom. On the top you have wing walk doubler which will be knife edged not rib. The metal strip (intersection fairing) is dimpled. OK. BTW the fuel tank has skin extending past the rib, so skin is dimpled and K1100 (dimpled or recessed) nut plates are used. That is fine for tank area.

Alternative plan drill the wing skins and rib (and wing walk doubler) up to #8 (in designated locations) and dimple skin and rib (and wing walk on top) separate, then assemble. When time to fit metal strip (intersection fairing) after wing is located and mounted to fuselage, finish installation by drilling and dimpling holes in strip intersection fairing. A hole finder or template can be used. The nut plates can be attached to RIB ONLY, so the 3/32 rivets will be hidden by skin (or rivets can go through both skin and rib (and wink walk doubler), in the unlikely event nut plate replacement is needed easier).​

Disclaimer I am not suggesting anyone deviate from plans, just asking for your critique opinion or other ideas. After overthinking Van's baseline for attaching the intersection fairing strip, I think it is fine. However FEEL FREE to opine on your alternative ideas, what you did and how it worked out, and also do you think the above alternative method will work. ALSO are there any other tips and tricks for installing this strip intersection fairing.

PS: Do they make reduced head 3/32 rivets for mounting nut plates, with less countersink depth? If yes where to buy? In the past I have shaved them if they were proud.
 
Did Vans stop supplying proper fillet-style intersection fairings, like the RV-4 kits had? The butt style is really no fairing at all. It leaves the assembly looking unfinished, as though the builder decided to skip a step.
 
Either way would work for me. The majority of the strength in each of those screw/nutplate sandwich locations will be the actual AN509 screw.
 
The rivets you want are NAS1097AD "oops" rivets. Van's sells them. These are reduced-head rivets; an 1/8" one has the head of a 3/32" one, as an example. I've used many for nutplates.

Dave
 
71459 said:
Did Vans stop supplying proper fillet-style intersection fairings, like the RV-4 kits had? The butt style is really no fairing at all. It leaves the assembly looking unfinished, as though the builder decided to skip a step.
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I had an RV-4 and know what you mean. No fillet fairing just flat metal. I actually switched my RV-4 out for the flat because the original fiberglass one was kind of ill fitting. The idea that fillet fairings (fiberglass) helps drag is theoretically good but practically it does nothing. The aesthetics personal choice. There is third parties that sell these full fiberglass intersection fairings. Or you could make your own, but this adds weight.

Ralph Inkster said:
Either way would work for me. The majority of the strength in each of those screw/nutplate sandwich locations will be the actual AN509 screw.
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That is true. With the intersection fairing (metal strip dimpled) and screw clamping down with skin, doubler, rib sandwiched in-between is good, friction works. Besides there are other rivets still in the assembly, I am not worried about strength, However knife edge is it is fatigue structure is a stress concentration, and could lead to crack. However even though this is wing structure the inboard edge has only sheer and no significant tension or compression. It will be fine per drawing.
 
I never liked the change Van’s did on this from the my first build (2000 or so). On the next build I did the wing skin countersink per teh plans and hated the outcome. On the next two builds I did not countersink the screw holes, they are all dimpled. The underlaying wing skin, rib and wing doubler are also dimpled. The screw hole gets a matching dimple style nutplates (either a K1100-08 or MS21053-L08). The nutplate 3/32’ rivets go into dimpled holes, again in the skin, the doubler and the rib.

Side note - I also dimpled the entire wing doubler, skin and associated ribs. This is what Van’s used to call for - no idea why they shifted to machine countersinking for the doubler.

Carl
 
I keep a supply of NAS1097AD3-4 rivets for installing nutplates virtually anywhere. I don't even use a countersink tool - just spin my deburring tool around a couple times and it's done.
 
71459 said:
Did Vans stop supplying proper fillet-style intersection fairings, like the RV-4 kits had? The butt style is really no fairing at all. It leaves the assembly looking unfinished, as though the builder decided to skip a step.
Click to expand...
They stopped that about three decades ago.

Someone ran some tests and the flat metal with rubber was less work, less cost, and there was no drag penalty. In other words, a lower cost, lower work, had the same top speed as the more work and more cost technique.
 
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