It's not secret here that I'm not much of a UCD/3D fan but heres a question based on observations. They seem like an easy fly with virtually no wing loading and can float around as good as any trainer.

Could these things be used as a trainer and or a good "second plane?"

There was a big thread on this several months ago. A common theme (once the "high wing trainer is the only answer" stuff was weeded out) was that the very light construction would make it too flimsy for an inexperienced pilot. That definitely seems to make sense. I have seen a UCD break just behind the wing on a rough landing that wouldn't hurt a traditional trainer or typical second plane (example: four star) at all.

I know that trainers can take the beating but with the light construction, a UCD won't survive it?

I'll have to agree with carrellh; the UCDs are a bit too fragile for a trainer... IF the student will be on the sticks for landing. If you're talking a buddy box set-up and just allowing the student to fly the model for familiarization, with the master radio/instructor handling things close to the ground, then yes; your reasoning is sound.

Same thoughts on these as a second airplane. If the pilot is past the landing prang stage, then by all means... the UCDs are very tame on low rates.

But they will take practically NO abuse. I realize anyone can have a bad landing. The results of that are why I hold the opinion I do. The UCDs are built very lightly.

That said... no doubt someone will chime in here and write that they have pounded their's in with no damage after doing an inverted double jump-back waterfall, etc.... Perhaps. But I do a bit of teaching at our field, and a UCD of any size would not even make my list for rookie pilots.

YMMV...

the 46 and 60 are two differently built planes, i have both and learned by myself with an alpha trainer and then bought a 60 size ucd and did just fine with it and it is built a lot stronger than the 46 in the area just behind the wing and will not break in half on a hard landing. the 46 will break there.
the weak spot on the 60 is the wing tips, tipping on turns will bugger up the tips pretty good but i would use a 60 size as a trainer and not think twice about it.
almost forgot that the LG is also a weak spot and you shouldnt use the wheelpants untill the gear shears off(will sheer with a clean break) and you beef it up a little, then you can install the pants, this is a easy repair

I have observed than many of the 3D type planes would make good trainers on low rates and power provided they were not whapped on the ground.

I saw a newbe guy several years ago come to the field with a Q500 plane with a TT GP40 engine. I thought it was going to be a gonner. But it flew about the same as a trainer.

There's several Sig SE's at the field and I've observed how forging they are on aproach. The Somthin' Extra is rather durable and also easy to repair when it is banged up. The design is dated now but it's probably one of the best sport plane secrets around.

Enjoy,

Jim