Hatz Biplane Association

For those without the classic plans, FSBW1 is a simple bracket on the Forward Spar Bottom Wing, it is 0.90 doubled up and welded.
I looked around and it is not easy to find 0.180 4130, definitely not in bar form, but Aircraft Spruce has it in a sheet. I will get that sheet and will probably have enough to cut 2 sets (at least) from the one sheet.
Or I might chicken out and do what the plans say, and edge-weld doubled up 0.090.

I wondered about this also. I checked my 4130 suppliers and no one had .090 thickness.

FSBW1...?????
Not having Classic plans I don't recognize this reference but if you are talking about the plates welded onto the landing gear Vee... I'm with you.
My CB-1 plans had the same type design. Along with welding the two pieces together, the plans ask you to heat and roll the top edge over before you attach it to the Vee. I couldn't see the reason for the two pieces either so I used one thick piece on each side, didn't roll the edges over, and welded them on. When it came time to put the geat strut into the available space it didn't fit. The distance between the two plates was the same as the diameter of the strut tube so there wasn't room for the cross tube the bolt goes through... took some head scratching to get it to fit and I haven't had any problems. The two piece design might have been Dudley's way of having a thin enough piece of material to roll and get the clearance.
Which ever way you choose, make sure you account for the cross tube on top of the gear strut.

Jeff Moore

If I remember correctly, it was normalized, or 'N' condition 4130.

Was'nt there a shortage of some thickness of 4130 plate a few years back ?? Jerry

Stay as close as you can to the drawings. Your project will go faster. Every change you make will create about ten more problems to solve further into the project.
John Hanson HC-012

I've been wondering the exact same thing. I can't think of why they would do that except maybe to make ordering material easier? Just cut 2 extra pieces out of .090 and weld them together rather than ordering stock for two small pieces??? Who knows...

Another question...
Upon studying the steel parts on the plans, I got to see that instead of using 0.180" stock, the instructions tell you to make two 0.090" per FSBW1, and weld them together to double the thickness.
I can't understand why this would be better than just getting 0.190 (or 3/16") thick 4130 and cut the FSBW1 parts out of that.
Any insights? Am I missing something?