Measuring new standing rigging from scratch?

[onesea]

Another answer could be Dynema I know it's a bit of buzz word at moment.
However for that size boat, you could use lashings instead of bottle screws.

 

[William_H]

The best cheapest option is to go dyneema /spectra rope 4mm or 5mm. Easily spliced and much lighter than wire. A friend has rigged his 22fter with dyneema and reckons it is good. I have used it for back stay and also trailer winch wire replacement.
If Op wants to use wire he may be able to get supplier to provide wire swaged at top so that he can fit it and get length right. Use cable clamps. Then return to rigger for bottom swage. Or just use rope to get length.
The screw end swaged on the wire is a very neat way to do stays with the toggle just at the bottom of the turn screw, Looks better than thimble and swage to fork end on turn screw. (bottle screw) ol'will

 

[DownWest]

On the above. Recent build with a local friend, I was prepared to swage his rigging, but when he went to buy the wire, they suggested Dyneema, as easier and cheaper. So he did, they also gave him the kit of needles to make the ends. Plus all round. And, he did use lashings for the chainplates. 20ft sharpie cruiser.

 

[MontyMariner]

few boats have right angle triangle rig ... the mast foot usually higher than the chainplates

Which can be resolved to two right angled triangles

 

[Refueler]

Which can be resolved to two right angled triangles

Everythng can be resolved of course ... its a matter of what is easy / practical and at hand ...

I'm good at maths ... so for me triangles would work - but I also have a practical mind that looks at tools at hand and sees how to use.

One of the main aspects here - is to work out all the factors with mast stepped.