Rivets - simple misunderstanding or misled by liars?

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BBerson

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No, but I have had a personal relationship with at minimum 1million solid rivets. I do know that they are not comparable to solid rivets and are not substitutable on a one to one basis. Even CherryMax are not one to one replacement for solids.
Correct. Avex are about one third in shear. ( about 100psi Avex to 300psi solid 1/8”)
So a home builder substituting a solid rivet for Avex shown on the experimental plans only needs to match the Avex's 100psi shear from the solid rivet and could use a smaller shop head. Substituting a weaker rivet is never advised.
 

Angusnofangus

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So a home builder substituting a solid rivet for Avex shown on the experimental plans only needs to match the Avex's 100psi shear from the solid rivet and could use a smaller shop head. Substituting a weaker rivet is never advised.
I'm not quite sure what point you are trying to make here. Zeniths were designed for Avex rivets and therefore one should use Avex rivets at a minimum. Cessnas were designed for solid rivets and that is what they are built with. Shop head sizes for solid rivets have a long established criteria. What solid rivet shop head sizes has to do with Avex rivets I don't know. To never subtitute a weaker fastener than the one originally designed for and used is Basic Sheet Metal 101.
 

Pops

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And I am sure that they are in a place where it would be impossible to buck a solid rivet. I am also sure that the design took into account the lesser strength of CM versus solids.
You are correct. If you do some reskinning you will understand why. Just no way to buck a solid rivet at the locations in a very low stress area.
 

wktaylor

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kjlpdx... Your comment in post #55 ...

"yes and no, a countersunk rivet significantly increases the shear strength in that the diameter is increased, so stronger tha[n] a non-dimpled rivet."... is a difficult-to-understand incomplete sentence that is needs clarification, your part. i am confused regarding Your intent.

BB... be careful... consistency and workmanship are essential to airworthiness. Non-aviation blind rivets used in aircraft should be installed conservatively to ensure consistent holes size, head-fit/tightness, grip-length considerations, bulb-tail formation [size/shape/etc] and corrosion prevention considerations.

My dad used cadmium plated Monel pop-rivets for the majority of this T18's fuselage, per Thorps guidance/standard practices... installed 'wet' with zinc-chromate primer, pulled carefully with a standard hand-tool, inspected from both sides and the head pocket [left by pin-stem break-off] filled-in with Bondo to prevent/minimize moisture intrusion.
 

VWLIFER64

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The head does nothing but keep the rivet in the hole. Remember rivets should only see shear loads... Something the the head has nothing to do with.
Not disagreeing, but need a picture for my head please. How does lift on the wing skin not result in rivet tension that is not a design load consideration of the rivets? How is that load transferred to the ribs/spar? Thanks.
 
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pfarber

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yes and no, a countersunk rivet significantly increases the shear strength in that the diameter is increased, so
stronger tha a non-dimpled rivet.
And the countersunk head is what part of the shop head?

the countersunk portion is also part of the grip length, unlike a 470 that includes no part of the head.
 

pfarber

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Not disagreeing, but need a picture for my head please. How does lift on the wing skin not result in rivet tension that is not a design load consideration of the rivets? How is that load transferred to the ribs/spar? Thanks.
Newtons 3rd law is a good place to start.

Burinelli is still just a theory... Remember that.

Also, only a sith deals in absolutes. If you are going to seriously dispute rivets should only be in shear and any tensile force makes them explode then you are lost cause and i am not going to take one second to explain it.

Some peoples kids
 

wsimpso1

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I just came up to speed on this thread. On the topic of tensile loading of rivets I have a few points to make.

Some manufacturers of structural pulled rivets actually give tensile and shear strengths for their products. Going into squeezed rivets, we know the alloy, its shear strength, and can compute the forces by several failure modes of the rivet, and by referencing the lowest of them, estimate maximum tensile load on such a rivet.

Doing a quick internet search, I found numerous references to design handbooks for various aircraft manufacturers with design guidance on use or rivets in tension. This should not be a surprise to anyone who has looked over a sheet metal airplane wing or, better still, noticed the difference in the top skin between sitting on the ground, and in flight.

On the ground, forces on the skins are small indeed, and the skins appear smooth. Take off and level at cruise speed, and the skin visibly bulges outward. Air inside the wing is typically stationary and at ambient static pressure. Air outside the wing is moving at a velocity near airplane velocity (look in TOWS Appendix I for V/v plots of various foil thickness distributions). This accelerated flow outside is then at pressure substantially lower than ambient. Solve Bernoulli's famous equation to go from local velocity to local pressure. This results in the wings skins being pulled away from the rest of the wing structure. In sheet metal airplanes, the skin is riveted to ribs and usually the spars, with the rivets thus being in tension from this load. Similarly, the tailplanes, control surfaces, and fuselage skin has similar moving air outside, stationary air inside, and the structures being inflated, with rivets holding the skins in place that are under tension.

Clearly, our riveted joints can carry some amount of tension. The result of my brief search indicated a lot of learned folks urging conservatism in design of rivets under tension. So, some designers do use some tension per rivet, and successfully too.

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