My glider will use a tow rope that is too strong. That rope, when under maximum pull, may damage the glider.

I need to install a weak link as a mechanical 'safety fuse'.

Here is one weak link system I can use:
wingsandwheels.com/tost-weak-l…

But which weak link is appropriate for my glider?

Federal Aviation regulations require a tow rope (or weak link) to have a certain breaking strength with regard to the maximum operating weight of the glider:

"The towline used has breaking strength not less than 80 percent of the maximum certificated operating weight of the glider or unpowered ultralight vehicle and not more than twice this operating weight."

ecfr.gov/current/title-14/chap…

To complicate matters, my glider can carry 400 pounds of water ballast. When I'm flying 'dry', I would prefer to have a weak link that is just strong enough for the dry glider, and when flying 'wet' I would prefer a (somewhat stronger) weak link appropriate to the heavier operating weight.

See the second graphic, which shows which Tost weak links I can use in the dry or wet ballast condition.

I will start out getting the weakest weak links allowed (green, yellow, and white) and see if that launches me well without premature weak link breaks.

Pro-tip. Try not to lift the rear end of the ground launch car.
youtu.be/kd9QxRPb3hk?t=33

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