Attaching Leading Edge to Spar??

Thermos · Post by **Thermos** » Sat Sep 30, 2006 5:06 am

RV7Factory wrote:I've seen documented quotes from Tech Support at Van's approving the use of LP4-x's or MSP-4x's. My understaning is that these are not structural rivets. I am confused, anyone care to comment?

You're absolutely right, they're not structural but Van's engineering approves their use here. To me, "structural" only means that they could support the same loads as a driven solid rivet - which those soft aluminum pop rivets obviously can't do. However, there are parts of the structure where a less-strong rivet might be just fine based on the shear and tension loads in that area - and Van's engineers must have the numbers to know that the nose rib-to-spar attach points fall into that category.

Dave

Thermos · Post by **Thermos** » Sat Sep 30, 2006 5:10 am

cjensen wrote:Too many builders try to second guess the design. It's a kit plane. It's overengineered and built for a reason...

Well said, Chad!

RV7Factory · Post by **RV7Factory** » Sat Sep 30, 2006 1:49 pm

Thanks Dave.

Wicked Stick · Post by **Wicked Stick** » Sat Sep 30, 2006 2:25 pm

Perhaps it is true that they don't "have" to be, but I would feel more comfortable with either Solid aluminum rivets, or cherry max or something similar in it's place, rather than soft pop rivets.

Lorin Dueck · Post by **Lorin Dueck** » Sat Sep 30, 2006 4:35 pm

All -
Wow - who would have thought a simple question would have sparked so many responses (including hooby/booby sidetracks

)??
Just for the record - I didn't want to start the equivalent of "Primer Wars II"...

Anyway, Thanks for your very valuable insights, suggestions & opinions....
After giving it some thought - I've decided to wimp out - and use the LP4-3/4 blind rivets.
Why??
- Van's endorses it (so it's structurally ok)
- It's easier
- Much less chance for me to really screw up a wing I've been working on for some time.

Thanks again - you guys are the best

Lorin D
9A Wings
N194LD reserved

RV7Factory · Post by **RV7Factory** » Wed Oct 11, 2006 8:38 pm

OK guys, I am reviving this post cuz I want you to check my logic and numbers.

According to my calcs, a -4 (1/8") AD solid rivet with a shear strength of 26,000psi and tensile of 38,000psi, calculuates out to have an actual strength of 320 lbs. shear and 466 lbs. tensile (for that size rivet). That seems a lot lower than I thought it would be. Anyone care to back me up?

prestwich · Post by **prestwich** » Wed Oct 11, 2006 9:39 pm

Hey Brad,

What the heck do you want out of one measly rivet? I'd say several hundred pounds of strength is pretty good! I don't know where you got your psi suppositions, but assuming they're accurate, I'll back you up on the arithmetic!

Jon

cjensen · Post by **cjensen** » Wed Oct 11, 2006 9:53 pm

Sounds good to me! Now, take that one rivet, multiply it by say 5,000 (just the 1/8th rivets) and you have 1,600,000lbs shear, and 2,330,000lbs tensile. Just round numbers...this means absolutely nothing BTW! I just made it up 'cuz I'm tired!

RV7Factory · Post by **RV7Factory** » Wed Oct 11, 2006 10:10 pm

Alright, here is where I am going with this...

My A&P neighbor came over today and we were talking about riveting the LEs to the spar. He was kind of surprised to see clearance issues, and I said, "Van's also approves the use of blind rivets here". Anyway, a discussion ensued about the strength of rivets and I pulled out my calculator and Aircraft Spuce catalog. Here is what I came up with...

Solid -4 AD rivets - 320 lbs. shear / 466 lbs. tensile
Cherry N blind MSP (non-structural) - 350 shear / 525 tensile
Cherry Q blind AACQ aluminum (structural) - 225 shear / 250 tensile
Cherry Q blind BSPQ (structural) - 350 shear / 325 tensile
CherryMax blind (structural) - 615 shear
Cherry Q blind CCPQ stainless (structural) - 700 shear / 600 tensile

Can you see what I am getting at here? In most cases, with the exception of the Cherry Q BSPQs and AACQs, which ironically are "structural" rivets, the blind rivets all appear to have better numbers than the solid. Is this correct, or am wrong somewhere here? I am somewhat surprised at the numbers... I would have thought the solid rivets would win by a wide margin.

Thermos · Post by **Thermos** » Thu Oct 12, 2006 5:00 am

Brad,

I'd say your numbers are at least in the ballpark. If I remember correctly, those Cherry rivets do have quite a bit of strength because they're designed to keep part of the steel mandrel inside the rivet - that makes the shear strength higher.

I don't think that most of the relatively soft aluminum blind rivets we use in RVs are guaranteed to retain the mandrel. It would be interesting to find some numbers on those LP4s that Van's recommends for the leading edge.

Dave

RV7Factory · Post by **RV7Factory** » Thu Oct 12, 2006 12:21 pm

Thermos wrote:It would be interesting to find some numbers on those LP4s that Van's recommends for the leading edge.

I really wanted to include them in the list, but couldn't find stats for them.

What I find most interesting is that the MSP rivets, which are classified as non-structural, appear to be stronger than the solids and many of the so called "structural" blind rivets. As you have pointed out, it has to do with the materials used, Monel (M) and Steel (S) in this case.

Lorin Dueck · Post by **Lorin Dueck** » Thu Oct 12, 2006 3:01 pm

All -

I saw a lot of "he said.. she said" on this thread.
So I called Van's yesterday - just to confirm that blind rivets are ok for fastening the LE Ribs to the Wing Spar.
I spoke with Tom Green and he agreed.
Tom also said I could use LP4-3 & LP4-4 (as opposed to CherryMax).
The one other piece of information he added was several builders use solid rivets on the outboard sections where it is easier to buck them.
Just more food for thought....

Lorin D
9A Wings
N194LD reserved

RivetBangers.com

Attaching Leading Edge to Spar??

Re: pops v. solids