being really picky about being dumb...

[bloke]

An hour ago, I was installing a bottom bow CAP on a 6/4 bottom bow, and kept having to shift the cap sideways to line up with old bottom bow guard WIRE ("rib") lines on the bow.

Finally, I stopped (to ACTUALLY think/evaluate) and realized a couple of things:
> A previous repair-guy had removed the o.e.m. bottom bow sheet metal cap, tossed that cap in the trash (typical: as they require a great deal of skill to repair and reinstall), and ONLY installed a replacement guard wire/rib.
> Their replacement guard wire/rib was installed off-center, which is why my bottom bow cap didn't want to line up with its marks.

bloke "one of those, 'You think you're SOOOO stupid' moments."

[the elephant]

Mr. Rusk installed my Holton's guard cap crooked enough that you can notice it from about 20 feet away. (grrrrrr…) and then installed the guard wire straight. It looks like CRAP to me, but I am not skilled/experienced in re-fitting bow caps, especially of this large size.

I purchased the Z-60 wheels that help you do this work, but have not yet had the time (or inclination) to learn and then polish this skill set. However, I *will* be doing this as I have a number of horns that would benefit aesthetically from bow caps that match the nice dent work done to the rest of the horn. (To be honest, though, it was that crooked-a$$ Holton cap that bugged me enough to finally buy that three-wheel set.)

I am going to add a sheetmetal shrinker/stretcher tool I have used for body panels in my auto shop. I recently discovered that the teeth do not mar sheet brass like I thought they would. I have not tried it with NS yet, but it will probably work well enough. I wish I could build one of these that was more accurate and took smaller "bites" with less distortion. Having jaws/teeth that are more suited to softer metals would be nice, too. Oh, well…

My big thing with the Holton was replacing as much of the wear and trim parts with nickel silver as I could afford, so — someday — I hope to make new caps for both bows out of NS. Even with brass wire (if I cannot locate it in NS) the visual offset of the NS against the brass bows will be beautiful to me.

And, of course, learning to scratch-build large bow caps will make it much easier for me to simply un-smoosh existing guard caps in the future, making that one more service I can perform to refurbished horns I want to flip.

[bloke]

It's more patience and teasing than skill...

My "secret techniques" involve
- pounding the cap out while still soldered to the bow
- removing the cap
- pounding it out better (against a piece of wood))
- greasing it up with STP and ironing it out on the dent machine (wearing gloves, so I don't cut myself on those treacherous edges)
- wiring it down to the bow (as many or as few wires that it's ill-fitted-ness requires)
- teasing down stubborn areas with the torch, dent hammer, and some burnishing from the inside

It ain't quick...

[the elephant]

Sounds like what I have been doing, except that when I do it the compound curve either opens up or unrolls on me. I have those wheels and hope to learn to shape the guard nicely so that very few wires are needed to solder it in place. Unfortunately, these are usually buffed so thin at the edges that *any* heat warps them outwards, just like welding thin body panels to a car. You have to stitch weld them. Maybe that is something I need to try: stitch soldering? I do not do this specific job much, so when I try to tap out the bad stuff with the guard on the horn the results are painfully slow, involving many hours of work. I can usually get it to fit pretty well and look pretty good, but installing the new guards on my 186 showed me what a correct fit should look like, and how fantastic really nice guards look.

I shall continue striving to improve my skill at this task.

[bloke]

Sounds like what I have been doing, except that when I do it the compound curve either opens up or unrolls on me. I have those wheels and hope to learn to shape the guard nicely so that very few wires are needed to solder it in place. Unfortunately, these are usually buffed so thin at the edges that *any* heat warps them outwards, just like welding thin body panels to a car. You have to stitch weld them. Maybe that is something I need to try: stitch soldering? I do not do this specific job much, so when I try to tap out the bad stuff with the guard on the horn the results are painfully slow, involving many hours of work. I can usually get it to fit pretty well and look pretty good, but installing the new guards on my 186 showed me what a correct fit should look like, and how fantastic really nice guards look.

I shall continue striving to improve my skill at this task.

tips from the almost-on-Medicare-suddenly-a-big-pro-socialism-waiting-to-get-my-physical-ills-fixed-on-your-nickel guy:

> Heat the BOW (with low heat), and NOT the cap...and let the bow swell out (using the heat/swelling phenomenon to your ADVANTAGE - rather than fighting against it) to MEET the cap. Re-flux often/generously (the water type of flux - on a Q-tip), so the surfaces stay clean, so you can solder on first passes, and so as to avoid high high. If you get it ALMOST there (a cap edge former bulge meeting the bow), you can then tease it up to 97% flush with hammer taps and (if looking for 99%) burnish the PAIR of sheet metal surfaces from the INSIDE - burnishing them out TOGETHER. Don't think of the bottom bow as some sort of "immovable do" object, or "something that - ie. "If not precisely ~this~ absolute shape, it will be 'wrong', etc...". Keep in mind that you are REPAIRING (and not fabricating) something, and that it does not have to meet NASA specs. THAT's how you get those annoying cap bulges to disappear...
...ok, but ALSO this: The less you stretch/warp the cap on the Ferree's machine (and the more straightening of the cap you do BEFORE you iron it on the Ferree's machine), the LESS-severe those annoying bulges will be.

bloke "offering tips - NOT as a know-it-all, but as a having-done-it-badly-and-gradually-better-it-all"