Hi Graeme, no offence taken.
What I was trying to say is that Jami is planning to move the CE of the new SJR sail forward in the hope that it will cure or reduce the weatherhelm.
But as the mast position hasn't been designed originally for SJR, he might not be able to put the jiblet luff the full 33% forward of the mast centreline or need to.
He will have to match the SJR CE to his new proposed weatherhelm-reducing position.
Really, I think that Jami needs first to draw up his proposed SJR, calculate it's CE and offer it up to his paper model to see if his drawn SJR sail CE will line up with his proposed new CE placement and with the leech of the jiblets in their correct position ahead of the split. If it doesn't, he will need to redraw, maybe with smaller jiblets
He will have to match the dimensions of his SJR to the mast position of his boat to ensure the SJR Sail CE is where it needs to be in relation to the hull.
If the jiblets and split end up somewhat less than 33% to achieve this, then that is what is necessary.
Less than 33% will give more positive sail feathering which is no bad thing anyway.
Don't get too fixated on that notional 33%.
I have no idea however by how much, shorter chord jiblets will affect their effectiveness.
As an aside, There are 2 Coromandels in the JRA.
Tammy Norie has an original flat sail and complains of bad weather helm due to heeling. The other Coromandel, Emmelene, has been retrofitted with Slieves original SJR for Amiina, is now exhibiting no weather helm.
No changed mast position and a full jiblet ahead of the mast, so Jami might be lucky yet.
I hope so.
Dave D.