MK-319-BS rivets for Flap rib

[seattleworm]

It was late, I was tired and a little rushing, and a mistake was made. I forgot to rivet the inboard flap rib to skins before closing the spar. Now, I have to use pop rivets for entire inboard rib. I ran through some crude analysis and it seemed that the MK-319-BS rivets would be ok to use. Per web info, shear strength = 258 lbs, tensile strength = 298 lbs. The allowable is actually higher than these for AN426AD3 rivets. Just want to get options from the RV experts, is it really OK to use MK-319-BS here, other than the cosmetic reason? Or what is the suggested pop rivet with the equal strength to a solid rivet. I know there is always a gap between "theoretical" and "practical" answers. I am also waiting for "official" answer from Van's.

My quick but conservative calculation (link here) showed the rivet would see a shear force of about 105 lbs (Vfe=100 mph). And the analysis is very conservative in my opinion.

 

[RV10Rob]

Van's can tell you for sure, but I think you can use a MK-319-BS to attach any skin, assuming the materials aren't too thick. It's true for the bottom wing skins, anyway.

-Rob

 

[GAHco]

Personal opinion.

Many people use these plated steel rivets in aluminum.
They may last for a long time in the right conditions.
In wet coastal areas they will damage the skin on and closely around the hole.

My suggestion is to use a CR3214-4-?
It's head size is very close to a 426-3 solid rivet, the hole will need to be #30 it can be put in thinner skins if countersunk or dimpled.

We have small packs of 10 or maybe you can find an rv friend who has an 8, we sold alot of these for gear towers.

 

[Bob Kuykendall]

Monel is not steel

Many people use these plated steel rivets in aluminum...

A minor point: MK319BS rivets are not steel, plated or otherwise. They are made of Monel, an alloy of nickel and copper which is galvanically very neutral against aluminum.

Emhart MD- (monel, domed) and MK- (monel, kountersunk) series pop rivets are used extensively in the HP-series homebuilt sailplanes, in many places to rivet steel and aluminum parts together. I've seen plenty of these birds in their fourth or fifth decade of service, and the rivets have not been an issue.

Thanks, Bob K.

 

[TThurston]

Steel - Aluminum

How about steel to aluminum corrosion issue regarding substituting CCR-246SS-3-2 rivets in the skin - like for those places where people using no-hole yokes after grinding the yoke down. Are these rivets a problem?

 

[seattleworm]

Thanks for everyone's input. I am leaning towards using MK-319-BS rivets. Actually, the drawing calls out MK-319-BS rivets for the last 3 rivets closer to the trailing edge to attaching the rib to both top and bottom flap skins (6 rivets total). Because the shear force at the rivet is primarily caused by the torque due to the aerodynamic load on the flap. With the same rivet spacing, the force should be the same at two of the 3 MK-319-BS callout locations. That makes me thinking it should be ok to use MK-319-BS rivets for the entire rib (16 rivets total), for both structural strength and corrosion. Solid rivets are preferred because they look nicer and much cheaper. Is this a right thinking? I want to make sure it is a right thing to do. I already made enough share of mistakes so far.

 

[bird]

my opinion

The 319 bs rivets will be fine for that, structurally plenty strong. After pulling them put a dab of epoxy in the hole of each one, let it set and carefully sand smooth. Then you and me will be the only ones who know!

happy building,

bird

 

[seattleworm]

Van's Answer

Finally I got answer from Van's. Here is the email. Now I can finish the flap. Appreciate everyone's opinion.

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Shawn,

Yes and MK-319BS would be fine in that location. It's a very strong structural rivet...

Best Regards,

Joe Blank
Airshow Coordination - Builder Support
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