Position of kite blocks

[Torchy]

Reviewing photos, particularly the recent ones of Marmite and Eleanor I find myself wondering why the blocks aren't sheeted from the rear of the boat. The kites hook in quite a lot in the bottom 1/4 of the leach.

Has anyone tried this recently? Do they get in the way a lot?

Why not route them through/underneath the tubes? Still leaves the sheets in the way upwind I guess and there's the redundant windward sheet but I guess strategic elastic could sort out these issues.

Would it free up the air around the back of the mainsail downwind and increase lift?

It means longer sheets and might make the kite less stable.

[phil_kirk]

I noticed the same thing on the 18 footers. 
This is a 3D problem.  In the vertical fore and aft plane the angle of the sheet from the clew of the sail to the rack will determine the tesion in the leach and the foot of the sail.  If using the same kite you moved the sheet blocks further aft the leach would become more open and the foot tighter. Yes you may reduce the amount that the sail hooks by doing this. If the sail is cut with a higher clew the sail would set better and allow the sheet blocks to be moved back.  A higher clew would reduce the ptential kite area for a given shape. Practical problems  could include:
Kite sheet getting caught round the boom if the kite flaps (occasionally happens on yachts who have the sheets led aft.
As you indicate you would have a few yards of sheet on or between the racks. The drag from a rope in the water is quite significant.

In the horizontal/vertical plane the hooking could be reduced.

Given that on a cherub we sail the best VMG when the boat is heated up we want the best efficiency when the kite is sheeted tightest whilst also getting an efficient kite shape whilst using the maximum area allowed.

[Torchy]

Barber-haulers anyone?

Would the gain be worth the extra faff?

[simon_jones]

Give it a try, if you cream past us downwind I'll change it.lol

[Torchy]

Depends whether it still works when I'm upside down.

I think it's on the list marked 'Maybe once I can sail the boat'

[JimC]

If you sheeted at the stern the clew would have to be very high indeed... Even in pole kite days we sheeted the kite to mid length because with a an efficient length spinnaker pole the clew was far further forward in the boat than other classes and that was the right place for it...

Kites are desperately inefficient sails really, and sheeting them is always a compromise. They're pretty much inevitably oversheeted at the bottom and too open at the head. The problem you've always got is getting a wide enough sheeting base.

Barber haulers... I'm not sure the optimum position for the sheet varies that much, because on a boat like the Cherub I think you should almost always be sailing the optimum angle... better to drop the kite and two sail rather than try and pinch it, and usually death to soak it. Its something you could experiment with, but in the past I thought about it and found that there wasn't any boat where I'd want to attach barber haulers... The rack boats are very different though in that respect: I really don't know about them.

[Phil Alderson]

The RMW kite I had on Primal was cut with a higher clew, and sheeted about 1.5 meters from the transom, most of the more modern ones seem to sheet further forward.

If the kite is cut for a fwd sheeting position you will have more control over the leech tension. Think trimming a jib on a cruiser 3-4 feet between block and clew, and a racer 6 inches to a foot.

With the higher angle of sheet up to clew you may also get more leach opening when you ease sheet without the foot getting too full

[Torchy]

Even in pole kite days we sheeted the kite to mid length because with a an efficient length spinnaker pole the clew was far further forward in the boat than other classes and that was the right place for it...

This was because moving it further aft didn't change the angle much because of the shape of the hull and the length of the pole (not on Tachyon anyway)...nowadays it often would alter he angle...it would on Loco Perro (quite markedly) but would it help?

Maybe some balmy spring Saturday morning I'll have a play and see what effect moving the sheet position has on the kite.

[Torchy]

Barber haulers... I'm not sure the optimum position for the sheet varies that much, because on a boat like the Cherub I think you should almost always be sailing the optimum angle...

...and if the optimum angle was a little lower as a result of a more efficient kite?

[Will_Lee]

The kite was not right down to the pole end in that photo. Sort that out and suddenly the curly-in bottom problem disappears.

[phil_kirk]

Sorry I didn't get it hoisted quite properly in some of the photos.  The halyard got tight before the pole got all the way out and i didn't want to break anything. 

The sails look good from the photos and appeared to look good from in the boat too.
A great sail in some great boats.

[Torchy]

It's horrible when your every move is scrutinised Phil...wasn't intended

They are gorgeous boats and look horribly fast...I guess the only way of beating them is through cunning and guile

[simon_jones]

Not with us sailing it's not, all you need to do is stay upright.

[Torchy]

Easier said than done in our case...5 minutes we lasted in Suicide Blonde in a force 1