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Bottom wing skins & cherrymax

Daniel S.

Well Known Member
Hey all.
I'm not saying I'm going to do this or anything... But I wonder why one couldn't use cherry max -4s for the bottom wing skin to rib rivets rather than the solid -3s. In my thoughts you could use solid rivets for skin to spar / rear spar where it is easily accessible and use cherry max for skin to rib attachment... I wonder if anyone has ever done such a thing on a -6 or -7?Didn't they used to use blind rivets back in the day for the bottom skin on the -6?
 
Hey all.
I'm not saying I'm going to do this or anything... But I wonder why one couldn't use cherry max -4s for the bottom wing skin to rib rivets rather than the solid -3s. In my thoughts you could use solid rivets for skin to spar / rear spar where it is easily accessible and use cherry max for skin to rib attachment... I wonder if anyone has ever done such a thing on a -6 or -7?Didn't they used to use blind rivets back in the day for the bottom skin on the -6?

The -6 instructions do say you can use blind rivets for the bottom skin as an option. I seem to recall they called out the CS4-4, but maybe it was the MK319-BS, been too long....
 
I don't recall using blind rivets as an option in my -6A instructions. I do recall looking for -3 Cherry Max rivets but the smallest size I could find was a -4. If that is still the smallest size that is available, then all the holes and dimples would need to be larger to accommodate them.

I think the instructions called for riveting bottom skins first and later the top skins. This made it easy to rivet the bottom, but much more difficult to rivet the top. I suspect because of the top skin being last, it is more likely that one could end up with "blemishes" on the visible surface of the top skin. If the top skin is riveted first, there were some areas on the bottom skin that could not be bucked. The stronger Cherry Max rivets would have solved this problem.
 
It is acceptable to use the MK319-BS rivets. It's been done on quite a few aircraft.
 
MK319BS

The RV4 plans when I got mine said you can build with Mk319bs rivets...... but why would you want to? They would increase the cost of the build considerably, they don't look as good as solids and would seriously effect resale value.

They are however a good get you out of trouble rivet as they are slightly larger diameter than the 3/32 solids, and are a simple way of dealing with places where it is difficult to buck a solid.

As for Cherrymax..... do you realise how much these cost??? It would seriously damage your bank balance trying to build a wing with these.
 
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The RV4 plans when I got mine said you can build with Mk319bs rivets...... but why would you want to? They would increase the cost of the build considerably, they don't look as good as solids and would seriously effect resale value.

They are however a good get you out of trouble rivet as they are slightly larger diameter than the 3/32 solids, and are a simple way of dealing with places where it is difficult to buck a solid.

As for Cherrymax..... do you realise how much these cost??? It would seriously damage your bank balance trying to build a wing with these.

Like I said, I didn't say I was going to do this & I'm only refering to the bottom skins, not building the whole wing with them. Honestly, if I wanted a pull rivet plane, I would have built a -12 :D I was just asking & having a discussion about it. I do wonder about the effect on resale if it's an "accceptable" practice & approved / documented by Vans. I'm not too concerned about resale in anyway. I'm a one time builder (I think). I plan on keeping this thing till I can't fly anymore.

Hypothetically speaking to do the bottom skins as I described with MK319BS, It would cost about $50 bucks & with the CherryMax -4s it would be about $200.00. Don't think this is too much considering a $120K plane. Still, I wonder about your point about resale.
 
The idea of using solid rivets to do the bottom skins seems daunting until the job is done. Once I figured out the correct pattern of riveting, its was just a mater of squeezing an arm in there. I had serious concerns about bending my skins back and reaching my arm in through the small gaps, but like many tasks that I wring my hands over this one proved to be a non-event.
 
I used a sort-of hybrid approach. Most of the bottom skin rivets aren't difficult to reach, so I just used solid rivets for those. For the difficult ones, it's wasn't worth the aggravation for me--I used the MK-319-BS.

-Rob
 
...
Hypothetically speaking to do the bottom skins as I described with MK319BS, It would cost about $50 bucks & with the CherryMax -4s it would be about $200.00. Don't think this is too much considering a $120K plane. Still, I wonder about your point about resale.

You've either got a source for a great deal on MK319-BS rivets, or you're thinking of Rob's "hybrid" approach. There are over 500 rivets in each bottom skin. Vans' price on MK319-BS rivets is 0.22ea. You're looking at almost $250 to use MK319-BS, or $800 to $1000 to do it with cherry max.
 
Definately not being a pain... Just sharing info At ACS the MK319BS rivets are 0.09 each or $40.50 for 500 or $81.00 for 1000.

Aicraft tool supply has CherryMax (CR3212-4-1) for $23.95 per 50 pieces or $479 for 1000

Wow!!!! I definately didn't know there were about 500 rivet per bottom skin. I just recently helped a friend do his -10 bottom skins & it didn't seem like that many. It did take about 20 hours though :eek: I was guestimating 200 rivets per bottom or 100 per skin x 4.. Great info rivet counters!!!! :D
 
MK319BS

Definately not being a pain... Just sharing info At ACS the MK319BS rivets are 0.09 each or $40.50 for 500 or $81.00 for 1000.

The rivet page at ACS is a bit misleading. The .09 price is not for the MK319BS (which is actually a 7/64" diameter rivet), but for the Cherry CCC-32.

I believe that Van's does not consider them equivalent in terms of performance.
 
Daniel,

My statement on rivet count may have been confusing. It's 500+ rivets for both bottom skins on EACH wing. 1000+ per airplane for the bottom wing skins. My log indicates I set 567 rivets installing the left top skins, and there's roughly the same number top and bottom - 20-21 per rib plus ~1-inch spacing along both spars.
 
The rivet page at ACS is a bit misleading. The .09 price is not for the MK319BS (which is actually a 7/64" diameter rivet), but for the Cherry CCC-32.

I believe that Van's does not consider them equivalent in terms of performance.

That is definately misleading & confusing!!!! I definately would not call that equivalent either... I see now that the drill size call out on that page is a #41 which is a far cry from the 7/64 (#33) I wonder why they would have the MK319BS number there.... Not fair!!! What is the proper cherry number for the 7/64 MK319BS?
 
Definately not being a pain... Just sharing info At ACS the MK319BS rivets are 0.09 each or $40.50 for 500 or $81.00 for 1000.

Aicraft tool supply has CherryMax (CR3212-4-1) for $23.95 per 50 pieces or $479 for 1000

Wow!!!! I definately didn't know there were about 500 rivet per bottom skin. I just recently helped a friend do his -10 bottom skins & it didn't seem like that many. It did take about 20 hours though :eek: I was guestimating 200 rivets per bottom or 100 per skin x 4.. Great info rivet counters!!!! :D

FYI, the rivets ACS sells as compatable with the MK-319-BS is CCC-32. These rivets are not the same at all. The diameter of the CCC-32 is less that 3/32 and they do not set properly in thin sheet. The Vans stuff is more expensive for a good reason.
 
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Strength

From what I have found the CCC-32 Cherry rivets are stronger in both shear and tension than a solid AD3- rivet. Please correct me if I'm wrong.

My concern would be the rivets slowly vibrating loose over time. I think you'd end up with a lot more smoking rivets.

It's also 9c (or 8.1c in bulk) per rivet instead of rivets you've already bought with the kit.
 
From what I have found the CCC-32 Cherry rivets are stronger in both shear and tension than a solid AD3- rivet. Please correct me if I'm wrong.

My concern would be the rivets slowly vibrating loose over time. I think you'd end up with a lot more smoking rivets.

It's also 9c (or 8.1c in bulk) per rivet instead of rivets you've already bought with the kit.

I have found that the ccc-32 rivets are almost always loose. Being SS they are probably very strong in shear, but they don't expand much when set so they don't fill a dimpled hole well. I think they would pull out easily. I reserve the few I have for nutplates.
 
Debate

It is a little bit beyond me why we are having this debate if its not something you intend to do. However, having pointed out that that this is not a good idea for several reasons:

1. Extra cost
2. Lowering of resale value.
3. Turning a swan into a duck.
4. Possibly never being able to get a buyer on resale.

I should also point out there are several other flaws in the points you have made.

1, $120,000 RV6.......... I don't think so.
2. You say you are not concerned about resale, so are you so rich that you can afford to throw away a $50 to 75k aeroplane?
3. Smoking rivets.
4. Its not actually that hard to rivet the wing up properly.

To be fair this thought occurred to me and I bet it has to a lot of builders, but
bottom line is you are building an RV, you really wouldn't want to spoil it in this way. One of the reasons I have not taken on a Mk 26B Spitfire is because of the pop rivets...... if I ever do build one it will have solid rivets.
 
Conclusion

There is no debate here, just discussion. I like hearing all of the differing opinions & like to learn as much during building as possible. This puts the educational element in "experimental" for me. ;)

In all honesty, I was just wondering about options & out of curiosity, I asked the man... (Van's). :D


Here is the Van's response:

"We've always used solid rivets for wing skins and have never done any engineering studies
on a blind rivet replacement. It might be possible, but we just don't have any data, one way
or another.

We've seen a LOT of RVs but don't recall one with blind riveted wing skins and almost never get a call about them..."
 
Using pop rivets vs hard rivets

I am repairing RV10 after hard landing and just wandering if I can use mk319-4
Pop rivets on bottom skins in stead of hard rivets for hard to get to places as I am trying To remove as little as possible to repair it
Thanks
 
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