Mast positioning

[trebor]

What is the mathematical formula for deciding a mast's position ?
I am looking at converting an Express dinghy into a single hander, Una-Bermudan, so mast will need moving forward ?

[JimC]

Its not nearly as critical as people seem to think. Most dinghies are sharing the side load between both foils, so moving the rig around changes the balance. So any crude method is probably good enough. Making a drawing of the sails, calculating the geometric centre of both, and then moving the mast enough so the centre stays in the same place is plenty good enough.

[trebor]

I had thought about using Laser setup, plenty of abandoned rigs.
Planned on using wooden foredeck to drop mast through and manufacture a base for it that sits on top of spinnaker chute.

[Rupert]

Mast pressures allowing (more than you'd think) it could work, but why not just sail a Laser? The Express was never the best design out there, and I can't imagine bunging the worst bit of a Laser (which has an amazing hull design) on it will improve it.

Now, putting an old bigger rig on it and throwing a trapeze on it, you'd have something slightly different!

[Alan P.]

A Contender rig then Rupert?. Could not agree more about the Laser rig. Ghastly!. The pressures on the bottom mast bearing on an unstayed set up can be quite something.

[trebor]

we have a few rigs to choose from, theirs a decent Cherub set up from the one I have been trying to get rid of before someone takes matches to it, must be at least 20 abandoned rigs.