A stomach-in-your-throat drop? What the...?;) If you're talking about drops that don't twist downward, I don't think you'll find many (any?) on a GCI. To see what Thunderhead's layout looks like, click right here.
Getting that "stomach-in-your-throat" feeling depends on the person. I don't really get that feeling on most rides anymore.:(
I think the long and short of it is that a twisty drop has a centripital force because of the curvature which cancels out some of the less than 1 g feeling of dropping. In the EGF and TTD examples, the axis of rotation is more or less through the rider (or very close) so the centripiral force is pretty negligible.
Then again, I may just be talking out my butt. You decide.
They may mean by "twisty", that it is a curving drop that swoops down to the right similar to other GCII coasters like Lightning Racer and Wildcat. Thunderhead does have this. The back seat is the best for the first drop, as you get some nice air on the way down.
The first drop from the back seat on Thunderhead is amazing, you feel as if you are being yanked over the hill. There are several spots on the ride where there are sudden, unexpected drops, which I guess you could classify as "stomach-in-your-throat drops." And there is one (from my recollection) that is actually straight.
Coasterpunk would be the best source on this though, as he has ridden the thing probably more they anyone else.
Thanks for the replies. I didn't know I would cause such confusion.
The reason for my question is that this coaster is being touted as one of the best (if not the best). However, to be one of the best (in my opinion), it has to have a drop that causes that funny, stomach dropping feeling. These drops are usually straight, rather than twisted. An example of such a drop is Ghostrider's first drop- it always "gets me." It sounds like Thunderhead doesn't have that element.