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Lower rear VS Spar - rivets too long

challinan

Active Member
Guys,

Just getting started building the vertical stabilizer. The plans (page 06-04) call out a 7/16" (.4375") flush rivet to secure a three-piece stackup: The rear spar itself, the doubler and the hinge bracket. The spar is .032", doubler is .125" and the hinge bracket is .063". That adds up to about a .22" total thickness.

Now put that AN426AD4-7 rivet in the hole, and it sticks out a full 7/32 (.2175 actual) past the edge, meaning 1.75D instead of the usual 1.5D. Needless to say, squeezing that rivet just lays it over. Even the -6 rivet sticks out more than the 1.5D typical.

Has anyone else run into this? Should I just use what works and move on?

-Chris
 
The first thing I always do when something doesn't look right is triple check that I am not missing something. In the case of the new 14 plans, this is probably less likely in your case, but still worth checking again.

In any event, assuming everything is in place as it should be, just use the size rivet that work best. I've even shortened some rivets because the best size was between two whole sizes before.

Chris
 
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I always (well mostly always) check the rivet length with my rivet guage before I start a new set of rivets. I've found a bunch of places where a slight adjustment to the rivet length works out better. I don't have a rivet cutter so sometimes you have to take the best option available and go with that. I do have an assortment of the standard size rivets including half sizes. These are cheap so it's worth it to have them on hand.
 
I don't recall those rivets being too long. I believe your math though. I normally check the rivet lengths, but may have missed those. More often than not, I've noticed Vans may favor the use of a slightly short rivet to prevent a difficult to set shop head.
If you have a c-frame, you may try and back rivet those rivets. It tends to help keep everything nice and lined up. You may not have the space to use the spring loaded back rivet set and have to use a regular straight set. Just make sure to keep the hinges clamped down nice and tight. Think I used some of those open C shaped vise grip pliers.
 
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Hi Chris,

I seem to recall those being a tad on the long side but not enough to do anything about.

Anyway, rivet gun and bucking bar for the 470s and squeezer with longeron yoke for the 426s... pretty sure that's what I did.

BTW using the squeezer took me quite a bit of practice. I still grab the gun and bucking bar first... especially with AN4s. Umm, also, I have two of each of the parts on that page(figure 2). One set got a lot of practicing/learning on:)
 
Chris,

I'm just BARELY ahead of you as I just set the last rivet into the vertical stab Monday evening.

I ran into the same thing. After looking at Mudfly's site, I decided to use my C-frame and back rivet the rear spar including the hinges. It worked well. I had to drill out a couple of the rivets you're describing. I found that the issue was the radius in the hinge brackets. The radius wouldn't allow the plastic portion of the rivet set to sit flush on the surface of the hinge flange. For those rivets, I used the -6 and squeezed. It worked nicely.

One other thought, you want to make sure you set the rivets properly. Under driving the rivets could/will make setting the flush rivets in the skin on either side of the hinges more difficult (don't ask me how I know!).

Best of luck,

Fred
 
My handy "rivet sizer" app calls out for an ad4-6.52 rivet with those numbers. I just used the -7 called for in the plans and squeezed carefully. I guess you could cut the rivet shorter too.
 
With issued serial #'s approaching 350, I haven't heard anyone complain about this rivet call out, but lets do the math....

The material stack up is .125+.032+.063=.220

1.5D of the rivet would be .125X1.5=.1875

.1875(rule of thumb amount of un-driven rivet shank) +.220 (thickness of the material stack-up) =.4075 (overall length of ideal rivet using the .15D rule of thumb)

Overall length of a -6 rivet is .378
Overall length of a -7 rivet is .441

So the -7 rivet is longer than the 1.5D rule of thumb nominal by .0335, but the -6 is short by .0295.
In longer rivet lengths a fair amount of the rivet material gets used up just swelling/filling the interior of the hole so in those cases it is common to not choose the smaller size if the nominal size falls between two standard rivets lengths, but if a -6 produces a shop head that meats the MIL Spec minimums for height and diam., it would be acceptable to use.
 
Option

Not to derail the thread here, although it does seem the issue is resolved, but I have an option for those just finishing up their VS rear spars. I did this for my second VS and it worked out well. I haven't updated my site showing this step yet, but I think I may have some pictures and try to get those posted.
Look at page 10-05 of the plans. Step 1 has you Cleco the vertical stab rear spar to one of the aft bulkheads for match drilling. I found it pretty easy to accomplish this step "before" I attached the VS rear spar to the rest of the VS assembly. Probably not too difficult after the VS is fully assembled, but thought I'd mention it if some want to consider that option.
 
half sizes

Many of the lenghts suggested in the plans are to long im my experience.
For some reason Vans did not include half sizes of rivets. Its not a bad idea to buy half sizes between the rivet lenghts included in the kit.....rivets are very cheap.
 
Many of the lenghts suggested in the plans are to long im my experience.
For some reason Vans did not include half sizes of rivets. Its not a bad idea to buy half sizes between the rivet lenghts included in the kit.....rivets are very cheap.

Half size rivets are not readably available in longer lengths and/or bigger sizes, because actual rivet length is usually not as critical when working with thicker material stack-ups. They are very common in the shorter lengths of -3 rivets.

For instances were a very specific length is desired is why most tool kits include a rivet cutter.
 
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