Ketch to sloop

Possible ? Does main mast need to be moved or can it remain with new backstay(s) installed ? Any other thoughts ?
Why not test sail without using the mizzen sail?
I the balance is ok there is no need to move the mast.. But you need to rig proper support for the mast.

What do want to achieve by doing this?
 
As a generalisation you will need to increase the mainsail area by increasing the mast height and move the mast aftwards to balance the boat which will also mean increasing the foresail area.

So basically a total re rig and new sails with the possible need to move an internal bulkhead or mast support, if you want to do it properly.

Otherwise just sail as a sloop without raising the mizzen but with the associated reduction in sail area and balance.
 
Not as simple as that. You need to find out whether the hull design was made with the alternative rig and see what the difference is - mast position, size, sail area. Just removing the mizzen could make a substantial difference to sail area and balance because in a ketch (as opposed to a yawl) the mizzen usually makes a significant contribution.
 
Why not test sail without using the mizzen sail?
I the balance is ok there is no need to move the mast.. But you need to rig proper support for the mast.

What do want to achieve by doing this?

A boat is for sale without masts at a discounted price - not keen on ketches prefer a yawl or sloop just weighing up options
 
Then even more important to have your new rig designed for the boat. Given that you will be getting all new spars then your problem will be deciding its size and where to put it on the boat. This may involve structural changes such as additional support and moving chain plate positions. Expert advice required.
 
A boat is for sale without masts at a discounted price - not keen on ketches prefer a yawl or sloop just weighing up options
In that case I would start to find out if this design have been built with one mast also.

Maybe getting some qualified help is a good idea if the boat is perfect for you. Would be a shame to buy a new mast and find out it's not working out.
 
Thanks all, asking on behalf of a mate, looks like a project too far to me - hunting down 2 identical masts to the damaged ones, equally expensive to have (sloop) mast and its position redesigned and then rerigged and a new sail wardrobe.

As the boats a 40ft motorsailor there may be a way around it but as mentioned a project too far in my opinion.
 
As the boats a 40ft motorsailor there may be a way around it but as mentioned a project too far in my opinion.
Motor sailor? keep her ketch, handy sail at the back that... No climbing over wheelhouse when taking sail down, balances the head-sail with minimal effort to put up. Motor sailing is a different state of mind..

Unless you really think you can make her a boat boat by being sloop rigged, its not worth the effort IMHO..
 
Take a look at how far back the mizzen was originally sited. Many motor sailers had tiny token mizzen sails, which contribute little to performance but a lot to wind age.

If a small mizzen possible could get a reasonable result balance wise, without moving the main mast, by increasing slightly the boom length and/or using fully battened main and putting a bigger roach curve on the back of the mainsail
 
Thanks again all - points well made all around, saw mate today whose not very happy about flying out to see the boat yesterday and finding a complete mess of a boat not worth an offer and not represented correctly by the broker - but that's another topic and not for me to expand on.
 
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