@Shorefun,
From my perspective, The video doesn’t reflect the real world. The RC boat is sailing on concrete (no buoyancy from water) and the hull form is too narrow to contribute to stability. And nobody would steer like that.
From my perspective, the video of a narrow hull without a keel and sailing on concrete is missing some important variables that must be considered in any analysis of the physics of a sailboat’s stability. The crew doesn’t shift its weight to help right the boat. There’s no center of buoyancy to help right the boat because there’s no water. The angle of vanishing stability on theRC without its keel looks to be less than 45 degree. That’s not a realistic representation of a Hunter 170 or most dinghies.
In the real world the Hunter 170 has a significant of stability generated by the wide fullform. Crew can to move to increase the righting moment.
To illustrate my point: how often does the RC boat capsize in the water as long as it has a keel. Would it capsize in water with the keel removed with or without t jib. I believe it would.
I would suggest you look at a technical discussion of stability. For example
http://www.wavetrain.net/boats-a-gear/471-modern-sailboat-design-quantifying-stability
One more salient point:
1. I am assuming that a loose jib means an unsheeted jib. Otherwise this topic would be about explaining why sailing wing on wing dead down wind requires less skill than with just a main in conditions that are dangerous - such as in high winds and swaves that can cause a “death roll”
2 if we are discussing capsizing after an uncontrolled jibe in high winds, I can assure from personal you that having a flooring jib won’t prevent capsize. Neither will having a sheeted but eased jib. You need to release the main sheet.
I’ve sailed catrigged boats and unballasted sloops for decades and raced them too. I seriously doubt that there’s much validity to the claim that an unsheeted jib makes a a significant contribution to stability.
That’s my story and I’m sticking to.
Judy
Ps. Please note that I am not arguing that a novice can’t capsize a Hunter170. He can if he steers the boat through an uncontrolled jibe with the tiller locked over, and stays on the low side, all in strong winds . One can, of course, capsize a Hunter 170, but you gotta do a lot of stuff wrong to do it, like sail in high winds before you learn how to do a controlled jibe. And if the skipper is doing that many things wrong, s/he shouldn’t count on an unsheeted jib to save him.