Will need help... my BD-12 was affected by Milton

[Scott]

Have you removed the fabric from the rudder yet?

Not overly complicated to repair the rudder. Can be done on a flat bench. The trailing edge lower section is suseptible to corrosion as are the other "catch water" points.

[Robert Lees]

Also, metal will weigh much more. The Taylorcraft as a breed suffers from the risk of aft CG issues at the best of times...adding a pound or two at the aft-most point will not help. Unless you lose the tailwheel & go for a skid!
To my knowledge, it's never been done before, so as others have said you'd be into STC and other legal issues. Go with option 1 or 3. 1 would be best (at least you'll know it will fit after repair!)

[Hank Jarrett]

Finding a used rudder to cover, or even one already covered shouldn't be a problem. Tail surfaces seem to be one of those items that tend to survive when the rest of the airplane is damaged. I would not even consider covering with metal.

Have to agree here. When you modify a control surface a WHOLE LOT of problems crop up with the FAA. You WILL need to know which rudder you need and which one you are looking at as a replacement. The easiest way to tell is to make sure the hinge line tube is the same as your damaged rudder. Pre war rudders were shorter with a larger chord while the post war rudders were taller. They are NOT interchangeable!

Hank

[3Dreaming]

Finding a used rudder to cover, or even one already covered shouldn't be a problem. Tail surfaces seem to be one of those items that tend to survive when the rest of the airplane is damaged. I would not even consider covering with metal.

[taylormarc]

I removed the rudder. As you can see it is pretty mangled up so I will need to:
1) rebuild it and put fabric on it or
2) rebuild it and put a thin metal cover on it if I can get and tx (I know of a Cessna 140 owner who has metallic wings so maybe?)
3) buy a new rudder somewhere

any ideas and is there anyone with the know how for #1 or #2?

I’ll address the aileron hinges after the rudder issue and thanks for all the insights about doing my own parts.

[Hank Jarrett]

Message sent

[woodmw]

Hank, I'm thinking it will be a lot more time and work dealing with the powers to be than the drawing, printing, milling, etc. If you are willing to ship part to me, I'm willing to spend some time trying.

[Hank Jarrett]

I have some corroded cast hinges that are complete enough to scan or draw from but NOT airworthy. Before you go to a whole lot of work I would make sure they will allow you to make a material substitution.

Hank

[woodmw]

Hank or Scott, do you, or anyone else on the forum, have a hinge that is unairworthy or otherwise unusable, that you would be willing to send me. I will try to draw part in CAD program and submit for criticism. I will return part if wanted.

[Schlitt]

I'm a DER that does this sort of thing quire often for a living, but with more critical items on helicopters. Although a fixed wing mechanic, I lack the fixed wing DER rating to help you guys out here with a directly approved alternate; however, I can sometimes grease the skids with one of a few FSDO contacts for surrogate field approvals using the same level of data package that I would normally write within my delegation. Replacements for magnesium are some of the easiest to substantiate substitutes from 2024.... even if there are forging grain flows to consider. 6061 even better, for corrosion protection. Its probably not financially worth the while to develop a data package and champion a serialized approval, but perhaps instead a collective STC effort. Are there enough folks that want these parts? Maybe a collaboration can make this worth while. I no longer fly a BC-12, but can sympathize with keeping antiques alive. Anyone have pre-war Chief Shinn brake parts or a spare Corsair wing lying around that they would sell me?

[braol]

Too bad we're not the Super Cub community...someone would have produced a titanium part by now...with a bushplane option of some sort I'm sure.

[Scott]

Understand the problems with approvals if you go that route. My thoughts were just about owner produced parts.

2024T3 is a much stronger more durable material than cast magnesium. Common and acceptable practice to use a higher grade material to fabricate replacement parts. Using 4130 in place of 1025 for example, or 2024 in place of nicral, or 032" in place of 025" etc..

I would certainly have no problem signing off a certificated aircraft with owner produced parts duplicated as described.

The advantages over steel are clear - no jigs needed, more consistant parts, that are easier to produce once the cnc file is created, and weight similar to the original magnesium ones.

Anyway just a thought.
S

[Hank Jarrett]

Giving this a bit more thought, I believe there is a relatively easy solution (especially if you know someone with access to a CNC or even manual milling machine).

for the two standard hinges, duplicating the magnesium castings by machining from 2024T3 bar stock would be stronger, similar weight, and more corrosion resistant.

The aileron bellcrank/hinge assembly would be less straightforward but still a relatively easy candidate for CNC duplication.

I had considered making door handles from solid (using hand tools) but in the end found two acceptable ones.

All these magnesium parts are getting hard to find so machining from solid might be an option.
S

Only problem is getting the FAA to approve the material change. ESPECIALLY on a part in the control system! You will need a DER to do the engineering analysis and then he will need to convince the Feds to allow it. NOT going to be easy, especially compared to making one from welded steel using the pre war welded ones that are already approved for use on pre and post war planes.

Hank

[Scott]

Giving this a bit more thought, I believe there is a relatively easy solution (especially if you know someone with access to a CNC or even manual milling machine).

for the two standard hinges, duplicating the magnesium castings by machining from 2024T3 bar stock would be stronger, similar weight, and more corrosion resistant.

The aileron bellcrank/hinge assembly would be less straightforward but still a relatively easy candidate for CNC duplication.

I had considered making door handles from solid (using hand tools) but in the end found two acceptable ones.

All these magnesium parts are getting hard to find so machining from solid might be an option.
S

[Scott]

Magnesium alloys have come a long way, but the early versions are suseptible to pretty much all types of corrosion.

To me the greatest risk is that corrosion happily occurs under protective coatings without showing at the surface.

one key factor is preparation. Chromate primers actually promote corrosion of magnesium alloys so non-etching primers are the only option. But similar to aluminium alloys, primer/paint does not adhere well without some sort of conversion process applied to the surface.

The proper conversion coating for Magnesium contains hexavalent chromium and is no longer available. In 2014 when I was restoring CF-CLR I found a plating company in NY that sold wipes soaked in mag conversion chemical but they too are no longer available.

There are prepcoats available that claim to provide a paintable surface but it's not a true mag conversion coating.

Frankly, if you can't find or make steel brackets, I'd be inclined to clean an airworthy mag version using the prepcoat, but instead of paint maybe coat them with a non-curing corrosion grease like True Turn. Very sticky, transparent, yet still has capillary action capabilities, and is proven even in saltwater environments.

This would at the very least, enable on-going visual monitoring for corrosion.