Cracked hole for engine mount

[RV10Rob]

While enlarging the first of the holes through firewall from 3/16" to 3/8" for the engine mount, the drill got "caught." Kept going, got caught again. Removed it and noticed two cracks in the aluminum piece that goes between the firewall and the steel weldment (I believe this is F-1001B). These cracks are through the entire thickness of the material. I'm guessing this is case of too slow/too much pressure on the drill. I was drilling undersize, so I reamed it out to 3/8", but the cracks are still there.

Anyone heard of this happening, or am I the only idiot that has done this? Of course, it's Saturday morning, so I have to wait two days to call Van's. Thinking about replacing that F-1001B part makes my head hurt.

Also, I just carefully examined the other top engine mount hole (which I haven't touched yet) and there's a huge chunk of material missing beyond where the 3/16" hole is! This is a quickbuild kit, of course, as I would have never riveted that piece with the hole looking like that. I'm wondering if that may be part of the problem.

-Rob

 

[Tom Martin]

Rob
I just got done riveting those pieces togther yesterday in a slow build kit. Pictures would be nice but I would say you are ok. The aluminium is basically in compression here. The main load bearing part is the metal fitting. There are two pieces of aluminium coming together in the top mounts and three pieces in the bottom mount. My point is that there are essentially cracks between these parts but riveted in a sandwhich they become one item.
My guess is that Van's will tell you to move on.

 

[Finley Atherton]

Rob,
I am not familiar with the 10 but are you sure the "cracks" you see are not the join between the pieces of aluminum that Tom describes in post #2. From memory, the mount hole is drilled through the join between the aluminum plates for the RV9 so the finished hole looks like it has cracks.

Fin
9A

 

[RV10Rob]

Rob,
I am not familiar with the 10 but are you sure the "cracks" you see are not the join between the pieces of aluminum that Tom describes in post #2. From memory, the mount hole is drilled through the join between the aluminum plates for the RV9 so the finished hole looks like it has cracks.

Fin
9A

Wow... looking again, that does indeed seem to be what I'm seeing. It's not clear from the plans where those two aluminum pieces join, and since it's a QB, I didn't build that part.

One more reason in the "why to build a standard kit" list

Thanks for the help, guys.

-Rob