Rudder reinforcement plates and nut plates

[blueflyer]

I am assembling the reinforcements plates and nut plates to the rudder spar. I see that the plans say to use 470 4-5's to attach the reinforcement plate to the spar and 470 4-7's to attach the reinforcement plate to the spar, and rib, but my question is:

What length rivet do I use to attach the nut plate to the reinforcement plate and spar? I dont see where it calls that out?

Same question for the reinforcement plate in the middle and top of spar? What length? I see it says 4-5 to attach the reinforcement plates to the spar, but nothing about attaching the nut plate to the reinforcement plate and spar.

Thanks for the help.

PS. you can see that I used 4-7 rivets in the bottom reinforcement plate/nut plate and they are too short.....

 

[Sparky]

On my drawing 7 it's called out in the left side view (to the right of the drawings you show). The top and middle rod end bearing platenut rivets are AN470AD4-6 and the bottom rod end bearing platenut rivets are AN470AD4-8.

 

[blueflyer]

yep, you're right. thank you.

 

[Frank Smidler]

check the rivet lengths

Don't blindly follow the plans when it comes to rivet length. With early kits, like my RV-6 the rivet lengths were suggestions that had to be checked. The 7's dwgs are more detailed as to the exact rivet and location but even then you will sometimes have to make adjustments. You want 1.2 dia to 1.5 dia stick thru before setting. Anything over 1.5 dia will roll over. From your pictures you may be setting the rivets too much. Although the setting standard for rivets is 1 Dia tall and 1.5 dia across, this is the ideal. It is almost impossible to achieve the ideal. Don't worry that a rivet is a little off in height or a little off in diameter, this is normal. The best suggestion I can give you is to contact local builders with more experience and work with them as to what is good quality.

 

[blueflyer]

Good advice Frank. Those rivets in the picture were set with too short of a rivet.

 

[roee]

Use a rivet gauge

Even when rivet length is called out on the plans, don't trust it. Use a rivet length gauge and select the rivet length as necessary.

Rivet length gauge:
http://www.averytools.com/prodinfo.asp?number=1008

And after setting the rivet, use a rivet shop head gauge to check that you indeed have no less than the minimum shop head height and diameter.

Rivet shop head gauge:
http://www.averytools.com/prodinfo.asp?number=1007

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Just saw the previous post by Frank Smidler. A couple of comments:

1) The numbers are a good way to describe the spec, but in the shop, using a rivet length gauge is more practical than doing the math.

2) About shop head height and diameter: there is no "ideal", but there are specified minimums that are required to ensure full strength. Your shop heads do have to be no smaller than the minimums, or the riveted joint will be weaker than spec. Bigger than minimums is ok. Again, use a shop head gauge to check them.

 

[Sparky]

Frank and Roee are giving good advice. I always check how much rivet shaft is protruding on the shop end and aim for about 1.2 - 1.5 of the diameter before setting and check with a rivet gauge when the result might be questionable. I often had to use a longer or shorter rivet than Van's called out in the drawings.

 

[az_gila]

Frank and Roee are giving good advice. I always check how much rivet shaft is protruding on the shop end and aim for about 1.2 - 1.5 of the diameter before setting and check with a rivet gauge when the result might be questionable. I often had to use a longer or shorter rivet than Van's called out in the drawings.

Note that 1.2 x diam. may be a bit short for a double dimpled hole since the holes get expanded a bit during dimpling. The rivets have to expand more sideways in the hole.

Aim for 1.5 x or a bit longer in this case - the -3 dimples are a bit less likely to roll over in this situation.

 

[N355DW]

Maybe a dumb question..,

...but is the rivet length that critical for a nutplate? Since the nutplate is basically a nut on the end of a bolt, and the only load the rivet really needs to take is the shear forces from screwing in the bolt, right? And in this case there is a locking nut on the other side as well to hold it all together. I used the largest rivets I had (7's) and they were slightly short on the lowest nutplate because of the lower spar being in the mix.

 

[GAHco]

Nutplates and Rivet Lengths

...but is the rivet length that critical for a nutplate? Since the nutplate is basically a nut on the end of a bolt, and the only load the rivet really needs to take is the shear forces from screwing in the bolt, right? And in this case there is a locking nut on the other side as well to hold it all together. I used the largest rivets I had (7's) and they were slightly short on the lowest nutplate because of the lower spar being in the mix.

For Nutplates it is not as critical, just make sure it has a large enough shop head so you cant take off without drilling it off.

Some time I use NAS1097 (OOps) rivets and they have a small head, they work just fine.

EXCEPTION, if you are installing a nutplate in structure with multiple layers of sheet metal, then use the 1&1/2 to 2 diameters because the rivets are contributing to more than just holding the nutplate. This applies to any style of rivet heads.

 

[longranger]

...but is the rivet length that critical for a nutplate? Since the nutplate is basically a nut on the end of a bolt, and the only load the rivet really needs to take is the shear forces from screwing in the bolt, right? ....

True, but in this case those rivets are also helping to attach the reinforcement plate to the spar.

 

[az_gila]

True, but in this case those rivets are also helping to attach the reinforcement plate to the spar.

Yes... but in this case the bolt and lock nut will provide more clamping force than the two small rivets.

However, it's easier to just make all of the rivets "good" than decide which ones aren't as important...

 

[N355DW]

Yes... but in this case the bolt and lock nut will provide more clamping force than the two small rivets.

However, it's easier to just make all of the rivets "good" than decide which ones aren't as important...

Yes, if I could have found some 8's I would have used them! Maybe they are in a small bag somewhere behind my bench or under a tool shelf....I will likely find them the day I get my pink slip! :-D