Need to fix a bad gap where F-601N overlaps F-601L on the Firewall

[bruceh]

What is the best approach to minimize this gap?



I can see several possibilities:
1) get out the hammer and vice and apply some gentle persuasion on the F-601N where it overlaps
2) put some shims under the gap
3) grind away some material on one or both of the angles
4) do nothing and have the firewall be less than flat

The factory bend on the F-601N is pretty bad on both L and R sides.
The angle looks more squished than bent. Since this is already predrilled, I'm concerned that trying to bend it more will just crack the parts.
Is there a safe way to bend a better angle in these parts?

[Don Jones]

Originally Posted by bruceh

What is the best approach to minimize this gap?



I can see several possibilities:
1) get out the hammer and vice and apply some gentle persuasion on the F-601N where it overlaps
2) put some shims under the gap
3) grind away some material on one or both of the angles
4) do nothing and have the firewall be less than flat

The factory bend on the F-601N is pretty bad on both L and R sides.
The angle looks more squished than bent. Since this is already predrilled, I'm concerned that trying to bend it more will just crack the parts.
Is there a safe way to bend a better angle in these parts?

....and if it makes the firewall less than flat there you sure can't tell it. Mine came out beautiful.
There are a couple of places just like this on the fuselage construction. The one place where I worked on the angle for a better fit, it came out looking worse than if I had left it alone.

[bruceh]

I ended up fixing this (sort of better, but not perfect) by using a couple of
clamps, another piece of angle with the same thickness, a couple of shims
and my heavy steel back rivet plate.

I put the angle with the bend over a piece of scrap angle with a shim in between. Laid this up against the back rivet plate and then used some
clamping pressure to get the bend to move down.

Seemed to help a bit, but there is still some gap. Looks like this gap should
pinch down when it comes time to rivet this.

[mcencula]

I didn't like how the aluminum angle joggles from Vans were deformed (both for the firewall and the forward floor stiffeners):


So I made up some tooling at work:


That clamps around piece of aluminum angle:


The two blocks on each end are solidly bolted in place, but the middle block is guided in slots on the side plates so that a hydraulic press can be used to push it down:


Resulting in a nice, even joggle:


The new joggles need a little filing and polishing to clean them up:


The joggles ended up being much better behaved and it was easy to control the "depth" of the joggle (.125 in this case). Notice how the new angle (bottom) doesn't have the "hump" that the original (top) did:


I cut the newly joggled angles to length, transferred the holes from the previous angles, and countersunk. They fit quite well:


BTW, anyone is welcome to borrow the joggle tooling for the cost of shipping both directions.

Good luck.

[Danny7]

Mike that is a great looking tool.

on the photo where you say " new joggles need a little filing and polishing to clean them up"

do you think if you put a little radius/ debur on the tool it would reduce the sharp crease? maybe even doing a 5 or ten degree slope for a milimeter or two to give it a transition.

i'm not in a real big hurry (would need to borrow my brothers press anyway) but i'd like to use your tooling.

[WingsOnWheels]

Originally Posted by mcencula

I didn't like how the aluminum angle joggles from Vans were deformed...... (snippet).

That is very impressive! Now you need to call Vans and sell them that tool!

[mcencula]

Danny,

Adding a radius would probably help, but it didn't occur to me. I don't think I'd radius anything more than 1/8". Here's why: since the skins are prepunched, there's only so much distance between the angle being overlapped and the first hole in the skin. The tool is setup to joggle within this space, but radiusing will effectively make the joggle distance a bit longer. Of course the end blocks could be moved towards the center block some to compensate for this, but I don't have access to the machine shop anymore (no longer work there).

To remove the crease I just ran a 1" die grinder along the crease. I held it non perpendicular to the aluminum angle (shaft at say, 45 degrees to the axis of the aluminum angle) so that the radius was somewhat less than 1/2". Came out well.

When you're ready, send me a PM and I'll ship it out. It's probably about 40lb of steel so I'm guessing a USPS flat rate box will be the best bet (assuming it'll fit).

Colin,

Thanks for the compliment. It does a nice job of joggling, but it's not very fast. Each operation makes two joggles, but you've got to almost completely disassemble the tool to get your part out. Takes about 10 minutes per operation. I don't think it would be very cost effective for Vans.

[az_gila]

...older RV-6 method that involves no joggling of the 3/4 angles.

The floor stiffener uses a 2 inch length of 3/4 angle (with a 0.063 spacer) to connect the stiffener to the thicker firewall angle.

Page 31 of the -6 plans.



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