This is the mast on my mate's newly acquired Farr 37. It had this prebend ever since it arrived here about 3 years ago. The luff round in the mainsail is a long way off! I have tried to alter the bend previously and spent some time yesterday trying to adjust it. I think having the luff round cut to suit may be the only answer. The halyard is tight along the mast and I estimate the gap in the centre to be 120mm. Easing the backstay has no effect.
You may have to ease the cap shrouds as there may not be enough length in them to allow the mast to come back in column.
Like a J35 or Sydney 41, checks control compression which controls rig tension and forestry sag.
A quick search shows the Glass Yachts built boat had permanent checks and the later Robertson build boats must have had a different section or sleeve and no checks
check the mast base as compared to the deck chocks.
Looks to all low down so check how far the mast is chocked formed at deck level.
Note the bend on this Farr 37. Piccy from DBY boat sales of 1992 Robertson Farr 37 (www.dbyboatsales.com.au/listing/farr-37/). Some chance it is the same boat (this one went by the name Electra 2 and was sold, perhaps in 2019), but if not the same boat, suggests mast bend is a feature.
If I had to guess that sail nos does not match the age of the boat being NSW.
Not the right mainsail.
Battens are too short for that vintage as well and no full length top batten.
Looks like babystay and checkstays, so if you want the straighten the mast, ease the babystay and crank on the checkstays. Screwing around with shroud tension isn't going to do much to alter the bend as it's almost an in-line spreader rig.
That being said, It's more that the luff curve of the main is just cut wrong. Thats a fairly normal looking amount of bend.
This my last boat Farr 37.Pippin..it looks the mast has identical bent .Pippin was professionally tuned, before Sydney Hobart race, as she was winner in her category. Later fully set up for Osaka race, never went. Many years neglect etc.
Have made a few Farr 37 sails. It was originally designed as racing boat and hence the prebend.
A few had runners and checkstay but these were generally dispensed with as the design became more club racing/ recreational in use.
I would not reduce the pre bend too much, some easing of caps maybe? To reduce to +100mm.
I would not go beyond this as may make the mast a bit wobbly and the last thing we want is to have the mast invert falling off big wave(s) and come tumbling down.
Recut the main ( messy and expensive but possible $700-800 and looks like an old sail) or replace it, but please use someone who understands sail design and not cookie cutter production!
My mate with the Farr 37 refitted the mainsail yesterday. I waited till all the work was done and then wandered over. He unpicked the luff tape and laid the sail out on the ground and using lengths of electrical conduit marked out the new luff curve. I think the luff round he used was 110mm, he just eyeballed the distance from the deck. The maximum bend in the mast was just below the second spreader, well above the middle of the luff. He lost a bit of sail area and had to make a new set of cringles. The cringles he made from 38mm stainless tube after turning up a pair of dies on the lathe and pressing them in his hydraulic press. The foot of the sail is a bit shorter now too and the clew arrangement will need some work. In the photo he has no tension on the Cunninham eye and the foot is too tight. I was amazed at how good it looked!