Edge distance, tank attach brackets

[StuBob]

Ok...I know what "perfect" looks like. But I don't know what "good enough" looks like.

Drilling the most inboard tank attach bracket (RV8), I got closer to the edge than I would've liked. But if I threw the part out, I'm not sure I could make it any better. This is how the un-prepunched part lines up with the prepunched parts. Take a look. Is this something to replace?

[Arie]

I would say that if you put an AN3 bolt in the hole and the head of the bolt does not hang over the edge of the bracket ,it would be good enough. Just my opinion...

[Vlad]

Nutplates go there. Leave it if you don't have a spare Z channel.

[ctennis]

Agreed with above - if the head of the bolt doesn't overhang the edge then I would leave it.

As an aside from someone who did this exact same step last year, I would also recommend very slightly oversizing the holes for the bolts (not the smaller rivet ones that attach directly to the tank baffle).

The reason is that when you mount the tank on spar, the bolt will have to go through both the main spar and the z bracket before going into the nut plate. If the nut plate isn't perfectly centered on every hole (and there are 21 of those holes on each wing), you will have a very difficult time getting the bolt to go through the hole - it will get caught up on the edge of the hole before threading into the plate.

I ended up having 3 bolts that gave me a heck of a time threading in. I had to go back and slightly enlarge the bolt hole in the spar AND the z bracket, and since the z bracket already had the nutplate on it enlarging the hole was not fun.

I also ran into the fun step that I had a #8 nutplate over one of the holes that somehow got mixed up into my #10s.

That was a frustrating day.

[Electrogunner]

Also on the nut plates. I always put a bolt or screw in the nut plates all the way while riveting them in, it lines the nut plates up as well as confirms you grabbed the correct size out of the bins. I use the same bolt or screw to do this so on final assembly gets fresh unused fasteners. I think it a good habit to get into.

[StuBob]

Thanks, guys.

[airguy]

Originally Posted by Electrogunner

Also on the nut plates. I always put a bolt or screw in the nut plates all the way while riveting them in, it lines the nut plates up as well as confirms you grabbed the correct size out of the bins. I use the same bolt or screw to do this so on final assembly gets fresh unused fasteners. I think it a good habit to get into.

I don't usually do this with nutplates, but on the Z-brackets for the tank attach it's A VERY GOOD IDEA - even a slight mislocation will be enough to significantly expand your vocabulary.

[longranger]

For those reading this before drilling your z-brackets, there is an alternative method of drilling them where you locate and drill the bolt holes before match drilling them through the baffle. This method has the added benefit of placing the rivet holes in the baffle side of the brackets slightly further away from the web of the brackets, thus allowing ample access with an un-modified rivet puller when final assembling the tanks. I think Jason Beaver's log (see builders logs on Van's web site), gives a fairly detailed explanation of the method. I have a short version on my build log, starting here.

[David Paule]

I'd recommend replacing the Z-bracket. The edge distance remaining will reduce the strength of the joint significantly. And without knowing the loads on it, we have no way of assessing whether the remaining strength is sufficient.

But hey, I'm just an old engineer... contact support at Van's and ask them. Still, if it were mine, I'd replace it without even thinking twice.

Dave

[pilotkms]

Buy new Z brackets.
Save the old ones, they make great standoffs for electrical routing.
Use the "alternate method" - it works - better.
That's 22 gallons of fuel hanging out there.