Structural filler (metal or composite) -- need suggestions!

[roee]

Working on the cabin steps: I've shaped the flanges of the step weldment about as close as they're gonna get to the contour of the skin. The edges look good, but there are a couple of low spots toward the center where there's still a slight gap (<1/16") between the flange and the fuselage skin . I'm worried that this is still too much of a gap to force together during riveting, so I'm contemplating how to fill that space.

I'm thinking about either brazing or melting some lead onto the inboard side of the flange. I believe the step weldment is 4130 chro-moly. Anyone have any experience doing this with these materials?

Or how about any epoxy-based (i.e. composite) fillers? Is there anything out there strong enough to withstand the pressure of riveting?

Any other suggestions?

Thanks,
-Roee

 

[frankh]

Shim it

If its not on the edege.

If it is on the edge, heat the plate to cherry red and tap it shape.

Thats what I did anyway.

Oh BTW...make sure you seal between the plate and the cabin sides...Proseal is best but a good caulk or seam sealer will work too.

Why?.....You will get rust stains running down your paint job if you don't....Sure priming should work but it might not.

Just what I found...I prosealed around the edge of the plate after I fitted it and discovered rust stains

Frank

 

[Stephen Lindberg]

FWIW, here is what I did. The fit of the flange was not so good at the back, so I trimmed it with a cut off wheel and then used a torch to heat it bright red and tapped it into shape. The gap (mostly at the bottom/back, 1/8 inch or so) I filled with pro-seal on assembly. I used pro-seal between the flange and the fuselage skin. No moisture will get in there, especially after it is finish painted. Looks good, too.

 

[Charles in SC]

Hello, I am a newbie here and have only lurked so far but I thought I would put in a comment here. I have not fitted the steps to my fuse yet but I have always been told 4130 is brittle when hot and should not be hammered on as it can crack easy.
My .02 and I am stickin to them.

 

[roee]

Thanks for the responses

FYI, the 4130 flange is pretty thin and is actually easy to bend cold using wrenches, hand seamer, etc. (no hammering needed). It's not showing any signs of strain or brittleness due to this shallow curvature. I would also be weary about heating it potentially affecting the temper, but in any case it's not necessary.

However in my case the problem area is very near where the tube is welded to the flange, so it can't really be bent out of plane there, no matter hot or cold.

This weekend I'll play around with shimming it and maybe some different fillers and I'll report back on how it went.

-Roee

 

[az_gila]

JB Weld

Although I'm not a fan of it, the local standy-by filler is JB Weld for the situation you mention....

Seems to get used a lot on the old planes around here ... keeping Bonanzas going (see thread to-day on Beechcraft costs.... ...)

gil in Tucson - buy Beechcraft parts - keep my pension solvent....

 

[videobobk]

Hello, I am a newbie here and have only lurked so far but I thought I would put in a comment here. I have not fitted the steps to my fuse yet but I have always been told 4130 is brittle when hot and should not be hammered on as it can crack easy.
My .02 and I am stickin to them.

4130 works great when hot, especially when at a dull red. The brittle part is if you cool it too quickly. Let it air cool and it will not be brittle, unless it is a very thin part. Those can be brought down slowly by backing off the heat a little at a time. If you oil cool or especially quench in water, 4130 can be VERY brittle.

Bob Kelly

 

[captainron]

Beechcraft parts

gil in Tucson - buy Beechcraft parts - keep my pension solvent....

Do they still determine the price of parts by simply putting a $ sign in front of the part number?