Originally Posted by Vampire
Ok this is what I need to know.
I was looking at going up 1.5 ft on the hoist so I will have to put in a new spin halyard.
and I am getting a purpose built sprit that will go out 4.5 ft in front of the fore stay.

what was your sail area?
And did PHRF penalise you?

Any one else have advice on this?
soon I will be starting a new thread on this.
I have heard that this is a common thought.

Here are a couple of thoughts from someone who's spent the last 2 years playing around and working with big A-syms after spending his entire sailing career in J/30's.

New Sheave: If the mast can support it then it's a good idea for a number of reasons which may not have occured to you yet.
1) The obvious bump in sail area that you get with the extra height.
2) This also allows for a larger shoulder to be built into your running asyms (used down to 155-150 AWA) which allows you to rotate the kite to windward and sail deeper.
3) Raising the head of the sail higher and getting the sail away from the forestay will be of great help when you gybe the A-Sail inside (pull the clew around the bow between the stem and the tack fitting of the kite). This is because you have less interference from the forestay and it gives the sail more space to clear and fill faster. J/105's have had problems with their setup forever because their kite is fouled up by the forestay and they wind up having to head up further in order to get it filled as they come out of gybes. Not fast! You avoid that by moving the sheave up the mast.

Sprit: Aluminum should work fine since the loads aren't too high on a J/30. Keep in mind however that if you decide to look into Code Zero's or something similar you'll need a bobstay which is taut at full extension to tension the pole and keep it from bending.

Tackline: Run to the end of the pole, usually through a block which is attached to the bale (another reason to make sure you have one) and a few fairleads running back to the cockpit. This allows you to ease the tack up to run deep as well as pull the sail out to the end of the pole.

The tackline can develop a lot of load so I would suggest (even though it's pricey) that you run it to a clutch which you bolt onto the side of the house on the starboard side. This allows you to deploy the tack on a starboard tack layline and run it to a primary winch for adjustments.
[Linked Image from farm5.static.flickr.com]
IMG_1496 by Daniel Goldman, on Flickr

Halyard: If you're considering experimenting with a Code Zero style sail that requires mucho halyard tension I would go with something not stretchy.

Sheets: One continuous sheet with a strop spliced in at the middle. This strop connects to the clew while the two tails run around the boat to your sheeting points.

Sail Choices: Since your wind doesn't get up above 25 out there much (I think) there are 3 A-Sails that I'd suggest for your inventory. The first thing I have to mention is the numbering scheme of A-Sails. They all have numbers but these numbers mean different things other than the size of the sail. For instance a 1A and 2A might have the same square meterage but they can be cut wildly different. A general rule of thumb for asyms is that even numbered sails are for sailing deep and odd numbered sails are for reaching while the size decreases as the numbers increase (ie: 2A is bigger than 4A). All that said, for a boat like the J/30 in the conditions you'll likely see I would recommend a 1A, 2A and 3A. The 1A for light air because you'll have to sail reachier angles for VMG anyways and a 2A won't do well. The 1A can run decently but over 10 or so you'll want to switch to the 2A which runs beautifully up until about 20 knots. Then you switch to the 3A (which also works reaching over 12) because you need the decreased size and the heavier material.

All of this is assuming unlimited resources and since that is almost never a reality some combination of a reaching asym and a running asym will serve you well.

If you have any further questions I can happily answer any of them.