Warbird Information Exchange

I am having a running debate with an engineer "friend" who insists that the flush rivets used during the second world war were not truly flush and that the current flush rivets used in restorations are not authentic to the originals. Anybody that confirm or deny this? He also swears that Hellcats had raised rivets on the fuselage. Another "fact" that I don't agree with and have been unable to confirm. Where is a good source of information on these kinds of details, anybody know?

AN426 rivets have been around since WWII. They are 100 degree angle. There is a different one which is 82 degree. I don't recall what the designation is for those. AN426 is Still used today so are authentic if that was originally installed. They do come in different alloys so the strength is different per each alloy. There are different ways of installing them, the skin could be dimpled ( a cone pressed to match the rivet) or countersunk ( a cone of metal removed to match the rivet using a special cutter).

Hellcats had raised rivets on the fuselage aft of a certain point, I believe just aft of the cockpit.

Rich

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AN425 had a 78 degree head.
There were also "domed" countersunk rivets but I have never seen them except in old books.

Sully

I think the DVD "Disney at War" has animations of the several different rivet types very nicely done. I'll have my 11 yr old check that for me as he probably has it memorized just where it is! If I can do a frame grab on them I will see what I can do!

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As I recall, Boeing has/had a small head countersunk rivet. It was slightly domed I believe.

Been a long time and CRS is setting in.

Sully

Where to find data? You 'just' need to see an unrestored W.W.II aircraft with its original rivets in place. Off the cuff the Chicago, Australian War Memorial and Imperial War Museum Spitfires are all still in their original W.W.II paint, with their W.W.II rivets in place underneath- they are unarguable examples. There are close enough photos of these online to answer the question, I'd hope. There are a fair number of static unrestored aircraft like this in museums around the world, some hopefully close to you. Flyers generally will have been rebuilt in most cases by now, although heavier types such as some bombers and transports have the original main structure repaired but not rebuilt.

For Hellcats, the recently recovered example from Lake Michigan would be pretty solid proof.

viewtopic.php?f=3&t=33243

The Fleet Air Arm Museum Corsair conservation story would be another parallel.

http://www.fleetairarm.com/en-GB/past_projects.aspx

Some aircraft had a mixture of flush and roundheaded rivets, of course.

HTH!

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James K

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Flush and "protruding" head rivets.

When reworking a static display aircraft I utilized a brazier rivet set on a universal head rivet. The result was close enough that it was not visible to the eye. I'm sure if measured it would be a little bit off.

Sully

Tigercat is the same way: flush rivets from the trailing edge back, well, level with the flap hinge points to be exact

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Does anyone have a source for new or NOS Brazier head AD rivets? They have a larger head for the rivet size than AN470 rivets.

Dan

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Ah, yes, the Roundheads were the ones trying to 'flush' the Cavaliers out of England.

Thanks for the correction.

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James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

I have a wartime book just on riveting at workand might have some answers in a couple of days. In general flush rivets were supposed to be about an eyelash thickness recessed below the skin's outer level. Recently it has been determined that leaving the head about the same thickness abover the surface level has no harmful effect to aerodynamics and is actually stronger in some instances and in certain sizes of rivets and thickness of skin allows for countersinking rather than dimpling. Each manufacturer had its own internal standards so the answer may very well depend on what aircraft you are looking at.

The reduced diameter head flush rivet has an NAS number. I am not sure if it was available during WW2 but was certainly known not long after. It may or may not have been developed by Boeing. What I do know is that on aircraft using the previous standard AN426 it is possible if you damage the hole to drill it out oversize and then use the next larger size NAS flush rivet which leaves the manufactured head the same size. So that someone looking at the rivet heads wouldn't know that one of them is oversize. I have heard that at Boeing they were called Douglas rivets and at Douglas they were called Boeing rivets meaning that they were used to cover up mistakes. "Hey Jack I blew this hole out give me a Douglas rivet."

Finally a number of years ago Boeing developed a new protruding head rivet. It is similar to the AN 470 rivet except the edge is more vertical, sort of like a round head with the top flattened. It is marked with a raised circle. You wouldn't want to see any of them on a restoration.

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Braziers are AN455 & 456

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Those who possess real knowledge are rare.

Those who can set that knowledge into motion in the physical world are rarer still.

The few who possess real knowledge and can set it into motion of their own hands are the rarest of all.

That is a Briles rivet, and they come in both countersunk and protruding head styles. The countersink is somewhat stepped rather than a uniform angle and the head of the protruding head is exactly as you described.

S

do you have a link or reference for that? I would be very appreciated.

regards,

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rreis

If you want pictures, see rreis@flickr

A rivet which has a flat crown that extends from the head of a rivet. The rivet is typically installed into a workpiece hole which has a countersink. The head has a frusto-conical section that extends from a rivet shank and a cylindrical section that extends from the frusto-conical section. The frusto-conical section sits within a countersink of the workpiece hole. Extending from a top surface of the head is a crown which has a flat end face and a tapered portion that extends from the end face to the top head surface. The crown has a diameter that is smaller than the outer diameter of the head. The flat end face is approximately 0.5 times the diameter of the shank. The crown has a diameter that is approximately 1.25 times the shank diameter. The rivet is deformed by a hammer and an anvil so that the crown becomes flat and the rivet fills the hole of the workpiece. The crown maintains essentially the same diameter during the rivet deformation process so that the deformation forces are transmitted primarily through the shank of the rivet. The rivet head completely fills the workpiece hole without requiring any post-installation shaving process.

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