Rivet Callout Too Short

[Bret S]

I'm a first time builder putting together the RV-7 Emp. and was wondering about the accuracy of Van's rivet length callouts. So far the first two rivet jobs HS-411 hinge assembly and the HS-609PP bars to HS-603PP rear spar are just "plane" wrong. I've only got too coats of SW-988 primer to add to the material thickness, so I don't think this can explain this problem.

I took the EAA SportAir Workshop and was taught to use the rivet guage. The next size longer than Van's callout for the HS-411 assembly is exactly correct. The next size longer for the HS rear spar is just barely too long, but the rivet called out is way too short. So, the class taught me to use the longer rivet.

Are other here finding this issue?

 

[jcoloccia]

A lot of his call outs are too short, but they work fine. The shorter rivets are easier to drive straight. On my first tail I used the shorter ones. On my second one, I used longer ones. I think you'll find that the next size up is actually just slightly too long. Until you get a feel for it, you may have some problems with these clenching over. However much strength you think you'll loose by using Van's callouts will pale in comparison to the strength you loose by screwing up holes trying to drill rivets out (the second one rarely goes in any better than the first).

So I guess that doesn't really help much, does it? I'd just start with his callouts and if you're feeling brave, try some of the longer ones.

edit: just FYI...I called Vans about this last year when I started, and this was the advice I got from them. It's spot on. When I built my first tail, I screwed up a bunch of rivets trying to use the longer ones. On Tail II, I used the longer ones NO problem...I just had a little more experience under my belt.

 

[dan]

Check out the Excel spreadsheet here: Rivet Grip Data. I put together a little table of rivet sizes and their resulting material grip capabilities. Remember the rule that before the rivet is squashed, it should stick out approximately 1.5D from the material (ends up forming a 0.5D tall x 1.5D diameter shop head). So looking at the table, if you have an AN470AD4-7 rivet, in an ideal world it is suited to grip material that is .2500" thick.

So, given this ideal world stuff, let's say Van's ships you parts that, when fastened together, end up being .2800" thick. 4-7 works best with .2500" and 4-8 works best with .3125". Which rivet do they call out? They'll call out the 4-7. The rivet will be a little on the short side, and the shop head might fall a bit short, either on the diameter or the height, or both. But Van's deems it better to use the shorter rivet rather than the longer 4-8 rivet -- because the 4-8 is probably gonna tip over as you squeeze it.

Also remember that Van's doesn't account for primer in their rivet callouts. So let's say you now add .012" to the equation (i.e. four average-to-thick layers of primer). The material is now .292" thick. Now the appropriate rivet size would probably be 4-8, with a material grip of about .3125. It would still be a hair on the long side, but probably the better choice.

Yet another thing to keep in mind is that the 1.5D rule of thumb is just that. A shop head .5D tall and 1.5D diameter is just a guideline. The Mil-Spec 47196A calls out a range for shop head dimensions, not a fixed specific value. So there's some built in leeway there.

Ok, I'm sure you get the point by now. Another answer is the rivet cutter. Let's say you really need an AN470AD4-7.5. You can make your own with the rivet cutter. Some builders will buy half a pound or whatever of extra long rivets, and then just cut 'em down however they need 'em. If you have 10 or 20 holes to fill, this might be a reasonable approach. If you have 500 to fill, then maybe it's not the right approach -- in which case we usually "settle" for a not-so-ideal rivet, but it usually works out just fine.

 

[osxuser]

You can also probably buy half-size rivets. I know I've bought AN470-3-3.5's before. On the other hand, I just did the HS-411's yesterday, and while a bit short, the application is such that it doesn't matter that much. Since those rivets don't have tension on them, just shear, I would also say that it is slightly better to pancake them, then to leave them taller, but not as wide. I'll stick with the recommendations for now, unless something comes up that I feel is dangerous... which I don't think will.

 

[szicree]

Also remember that Van's doesn't account for primer in their rivet callouts. So let's say you now add .012" to the equation (i.e. four average-to-thick layers of primer).

If four layers of primer adds up to .012 you're putting the stuff on with a roller! I just mic'd some and got about .0005 per layer (two coats). This would give only .002 for 4 layers. I think there is some confusion about the thickness of primer versus that of surfacer or high-build sanding primer.

Otherwise, the advice about rivet length is spot-on. Use the rivet gauge and get some half sizes to make things easy.

 

[dan]

If four layers of primer adds up to .012 you're putting the stuff on with a roller! I just mic'd some and got about .0005 per layer (two coats). This would give only .002 for 4 layers. I think there is some confusion about the thickness of primer versus that of surfacer or high-build sanding primer.

Definitely. I was taught only to apply a light dusting of primer. My mentor/DAR Gary Sobek just told me that in A&P school, in the priming exercise, if they added more than 1.5% weight to a part after priming one side, they failed the exercise. Thought that was an interesting point of trivia and worth mentioning here.

 

[Bob Axsom]

WOW! Questioning Rivet Size Callouts?

Rivet sizes are almost never right on. Most drawings used to have a note that you could go up or down two or three sizes as required to get the right finished product. If you don't have sufficient penetration to get a good shop head go to the next size don't use a marginal fastener just because that's what the drawing calls out and that is what is in the kit. Structural integrity override drawing compliance every time. Buy long rivets and a rivet cutter. Make them the size you need for the job.

Bob Axsom

 

[alalalal]

undefinedundefined

all of what dan said esp the last para..

"Another answer is the rivet cutter. Let's say you really need an AN470AD4-7.5. You can make your own with the rivet cutter. Some builders will buy half a pound or whatever of extra long rivets, and then just cut 'em down "

some are on the short to begin with and the primer decreases this and when its cloese already well lets just say now its too close..ther are some threads here more in depth but im sure you get the picture now

if they shoot guns all day its none of my bussiness :eekundefinedundefined:

 

[ratc]

RV-4 Aileron Pushrod tube?

What about if the rivet callout is larger than anything that came in the kit?
For instance the Aileron Pushrod tube (1/2" steel) with AN 490-HTBP fitting calls for 2x AN470AD4-12. I've not found any in the bag's but there are lot's of -11's. I'll measure them later today for length but I expect they will be OK and the callout has changed! What is the callout on other models? I'm pretty sure it will be a common component. Better still, if you have found some
-12's in your kit what bag were they in?