Fuse longeron countersinking

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Thermos
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Fuse longeron countersinking

Post by Thermos »

Fellow RBers,

I'm riveting together the fuselage canoe, and have discovered that I under-countersunk the longerons. As I've done up to now, I went with Van's "a few clicks below flush" guidance to make a test rivet set around 0.005" below flush in the longeron countersinks, but now that everything's clecoed together I find that the skin dimples don't nest at all well into the longerons - even after riveting a few - and I've got a pretty large (~0.01") gap between the longerons and skins.

Thinking maybe I laid the primer on a little thick, I made up some test parts out of some bare 0.032" sheet and scrap angle...same result.

So my question is...how many of you stuck with Van's guidance? If you did, how did your longeron rivets turn out? If you didn't, how did you figure out the right countersink depth? Van's has been pretty adamant in the past about not overdoing countersinks...don't want to take off any more material than necessary.

Dave
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captain_john
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Post by captain_john »

Dave, can you post a picture?

I know that we discussed it over the telephone but it would be nice to see it.

Sounds like going a little deeper until it looks "right" might just be the ticket.

I think you might be right about the paint filling them back up again.

:) CJ
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DaAV8R
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How many clicks

Post by DaAV8R »

I just finished countersinking the lower and mid longerons. I will start the upper longerons tomorrow night. I will try to count the clicks tomorrow night. It is more than a few. I have noticed that a small gap will close when riveted. I think a small bit of interference is desirable. Sounds like you might need to go just a tad deeper.

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leffler
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Post by leffler »

Sounds like over analysis to me. If you are priming, just countersink just a tad deeper to allow for primer thickness. I always used a rivet or a dimple guage to determine the proper depth.

I made dimple guage out of a small piece of aluminum about 1/2" wide and couple inches long. On one end I drilled a #40 hole and the other a #30 hole, then dimpled each one with the appropriate die. This makes a great tool to determine proper countersink depth. When the guage sits flush, you know you have the correct depth.

bob
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TomNativeNewYorker
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Re: How many clicks

Post by TomNativeNewYorker »

DaAV8R wrote:I will try to count the clicks tomorrow night. It is more than a few.
Theoretically, each click should equal 0.001".

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Thermos
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Post by Thermos »

CJ, I'm bringing some of the test parts I made to your shindig tonight.

Something interesting I found is that Cleaveland dimple dies actually make a wider dimple than my old Avery dies...go figure. I could probably get by with a few extra clicks deeper than 0.005" had I used the Avery dies, but the wider Cleaveland dimple means going down to 0.010-0.015" to get a dimple that nests reasonably well.

What, me overanalyze? Nah... :o

Thanks everybody! :)

Dave
Dave Setser
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Putting the "slow" in slow-build since 2004

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captain_john
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Post by captain_john »

Cool! See you at the pow wow!

:) CJ
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It's all over but the flying! 800+ hours in only 3 years!

DaAV8R
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Countersink depth

Post by DaAV8R »

I checked the depth tonight. .005 to .007 seems about right for my setup.

Spike
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Post by Spike »

Don't forget that they suck up when you actually set the rivets.

John
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Current Build: 2 years into a beautiful little girl

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