-14 Rudder

[climberrn]

Any cracks found on -14 rudders? Specifically at the rivets of the forward and rear ends of the ribs?
Ordered a -14 rudder for my -7A and am considering making .020 skins for it during the build. The standard -7 rudder is not holding up well at those rivets with the new 390. Don't mind building a new one but would rather it be my last one on that plane. Am aware of people using the -8 rudder on the -7, but I'm going with the -14 one for a couple of reasons.

 

[bjdecker]

I ran into this on my -7 with IO-360-A1B6 (200HP). When you roll the rudder front edges together, the skin deforms a bit and flexes into the stiffeners just behind the spar. Deburr and rounding the forward edges of the stiffeners will eliminate the potential for cracking due to this. I also applied a little neutral cure RTV (wad of bubblegum) to the areas between the rudder spar and each stiffener.

Mad props to DanH -- I can't draw worth a darn. Here's the idea tho -- side view from the top of the rudder assembly; skin (green), spar (blue), stiffeners (orange)...

Clear as mud?

 

[climberrn]

I ran into this on my -7 with IO-360-A1B6 (200HP). When you roll the rudder front edges together, the skin deforms a bit and flexes into the stiffeners just behind the spar. Deburr and rounding the forward edges of the stiffeners will eliminate the potential for cracking due to this. I also applied a little neutral cure RTV (wad of bubblegum) to the areas between the rudder spar and each stiffener.

Mad props to DanH -- I can't draw worth a darn. Here's the idea tho -- side view from the top of the rudder assembly; skin (green), spar (blue), stiffeners (orange)...

Clear as mud?

View attachment 69841

Got it. Vans also suggested a light coat of pro seal under the forward and rear stiffener rivets. The cracks formed from the rivets. Fine for 700 hours with a 200+ HP high compression parallel valve engine. After the new engine I’m finding small cracks after every long trip. The -14 stiffeners tie into the forward spar so that should help. Also found a couple at the aft rivets to the stiffeners.