The Gospel according to St. Van; Vans Instructions

[mustang]

OK, this is not a question, more of a caution to new builders. Don't take all of Vans instructions booklet as gospel.

Case in point, the very first riveting instruction is to sandwich the elevator pivot bearing in between the mounting brackets. Then the instructions specify the rivet type and size. We lightly primed the bearing housing and of course the mounting brackets were already powdercoated. The very next sentence in the instructions was in (brackets) and stated, "(these are the correct length)", refering to the rivets just specified.

We made a dry run with the specified rivets and I thought the rivets seemed a bit short. (I have very little riveting experience) We re-read the instructions and decided to go ahead as instructed. We squeezed a couple of rivets and used the Avery rivet gauge tool. HEY! These rivets did not measure up???? Hmmm,... maybe we are not using the tool correctly?

We pressed on regardless and completed the job. I took the completed part to my very experienced friend and he told me that the rivets were too short.!?! I asked him whether I should drill them out and re-rivet but he said "Don't bother, they are pretty close to spec". "Next time, measure the rivets and disregard what it says in the instructions."

BIG REVELATION! Measure the rivets and disregard the instructions! WOW. For us first time builders this is a big leap of faith, or maybe a big step away from faith. As a pilot of this RV that we are building, I want it to be as correct as possible. But now I am told to disregard the instructions.

This is interesting, because as a very experienced model aircraft builder, I can scratch-build anything I want to. I can also build from kits and I am used to following instructions. In this new world of building a full size aircraft that my life will depend on, I'm feeling a little bit at loss.

I'm losing my thread here, so I'll just say to you new builders, don't take the instructions as gospel, measure your rivets before squeezing, and carry on. I think that the combination of thick powdercoating on the elevator brackets and the primed bearing housing contributed to the short rivets. We have since found other rivets that were not long enough on the horizontal spar doublers, again, probably because of coating the parts with primer. I've had to go over to my friends shop and borrow enough longer rivets to do the spar when the kit supplied rivets were NOT LONG ENOUGH for the job.

OK, That's it from me. Just a little heads up!

Cheers, Pete

[Ron]

Hi Pete,

the rivet's are to short, you did a fine prime job. I also found the same to be true with my 7. And, much like yourself, I have found the rivet's to be to short in other place's as well. They say van's over enginered to compensate for the fact that we, as amatuer's, may tend to bend the longer rivet's. I will be using the gage's thruout my project. It's a good thing we pick up on the little thing's.............Good luck, Ron

[svanarts]

My rule of thumb for Van's rivet size callouts was to go a half step larger. So if Van called out -3.5 rivets, I'd go with -4's. And so on.

[Dan A]

On the rivits for my 8 I used the basic rivit gaging law for shop head rivits. 1&1/2 times the diameter of the rivit for the length for the shop head. It works every time. You will find all that information in the FAA manual AC 43.13.2B
Dan

[arffguy]

This is why the rule that allows homebuilding has the word "education" in it. I have used the Avery gauges all the time. I wouldn't build without them. Especially the one that determines rivet length needed before driving them. Van's instructions usually, and I mean usually, are correct. But there are errors. Everyone who whines about Van's plans errors obviously have not looked at very many sets of airplane (R/C model or full scale) plans. He used to draw them by hand and what the engineers make now are pretty damn good. Remember he started out as a one man shop and look what he has now. However, I would not recommend trying to drive longer rivets than called for as a general rule. Use what works.

[Reheat]

I did the same thing. Put my first rivet in the bearing and it was too short. So I drilled it out and was a little curious as to why Van's went to the trouble to tell us specifically that this was the right size. Later I re-read a sentence in the instructions that stated that sometimes the rivet callout is a little short but has been determined to be ok. So I think that this is one of those cases. Either rivet size will be ok in this instance I believe.

[David]

I am building a RV-8A and almost every rivet called out in the blueprint is correct or close enough to the correct lenght. I have only had to cut about 6 rivets in the whole tail section.

I am using the Avery rivet gauge and this has really helped make the decision if the rivet is OK.

[ptrotter]

iIn a number of locations, Van's purposely undersizes the rivet lengths, where the "correct" length falls in between 2 standard sizes. They do this because they feel that inexperienced riveters tend to bend the longer rivets, which they would then try to remove and redo. They feel that an underlength rivet properly installed is probably better that the possible damage one could do trying to remove a bent rivet, e.g. creating an oversize hole.

In most of the cases where they do this, the stress on the rivet is in shear so a slightly ujndersized shop head is of no consequence.

I used longer rivets on my HS bearing as I measured them the same way, but on other locations, I used Van's call out sizes rather than increase the length as I felt, as did VAn's, that it would make not difference to the strength of the assembly.

If it makes you feel better, by all means use the longer rivets, but it really isn't necesssary.

Paul Trotter
RV-8 82080 Wing Kit