leaving gap at downhaul bottom between pulleys

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gandalf99
gandalf99
33 posts
33 posts
1 Oct 2026 6:28am
Bit of a silly topic perhaps, but curious if I am missing anything:

Assuming the sail has correct downhaul tension, are there are any changes/consequences to be expected when the entire rig is, say, 4cm higher than it would be if it were pulley-to-pulley at the bottom?

For a simplistic example, if the downhaul number is 374, you can rig a 370 with 4cm extension and pull all the way down to the bottom pulley. Or if you had 8cm extension, you can downhaul until you are 4cm from the pulley. The sail has the same tension/shape in either case. Your body is now 4cm lower at any given point on the sail, which should be mostly irrelevant unless you got silly with the number.

Is there anything else that will happen doing this vs. rigging with the minimal base extension? There are a few different reasons for doing this, one of them is that on some very tiny sails the boom cutout is too low. Raising the whole rig allows me to have the correct boom height. I've done it countless times with one particular sail and its seems no different to me.
elmo
elmo
WA
8905 posts
WA, 8905 posts
1 Oct 2026 6:40am
The extension numbers are a guide, if you have found the correct rigging downhaul and you have 4cm extra, then shorten your extension next time.
It is also possible that you are under down hauling your sail which is quite common.
The extra height at the bottom of the sail is only an issue for race sails for closing the gap. The critical height (boom) is set by yourself.
decrepit
decrepit
WA
12917 posts
WA, 12917 posts
1 Oct 2026 9:57am
In theory a gap between sail and board, decreases sail efficiency. how much practical effect that has is anybody's guess.
Maddlad
Maddlad
WA
944 posts
WA, 944 posts
1 Oct 2026 12:06pm
gandalf99 said..
Bit of a silly topic perhaps, but curious if I am missing anything:

Assuming the sail has correct downhaul tension, are there are any changes/consequences to be expected when the entire rig is, say, 4cm higher than it would be if it were pulley-to-pulley at the bottom?

For a simplistic example, if the downhaul number is 374, you can rig a 370 with 4cm extension and pull all the way down to the bottom pulley. Or if you had 8cm extension, you can downhaul until you are 4cm from the pulley. The sail has the same tension/shape in either case. Your body is now 4cm lower at any given point on the sail, which should be mostly irrelevant unless you got silly with the number.

Is there anything else that will happen doing this vs. rigging with the minimal base extension? There are a few different reasons for doing this, one of them is that on some very tiny sails the boom cutout is too low. Raising the whole rig allows me to have the correct boom height. I've done it countless times with one particular sail and its seems no different to me.


You should always have the sail as close to the board as possible to lower the center of effort and centre of gravity in your rig. You can go a couple of centimetres extra if you need more acceleration or release from the sail in gusts, but if you have a big gap between the pulleys on the bottom of the sail and the mast extension thats not efficient.



Orange Whip
Orange Whip
QLD
1088 posts
QLD, 1088 posts
1 Oct 2026 5:31pm
I find that when using a Power XT extension you have to leave at least an extra couple of cm otherwise de-rigging the XT will be problematic. Is this what other Power XT users have found?
SurferKris
SurferKris
511 posts
511 posts
1 Oct 2026 5:27pm
I set my boom height in relation to how the sail feels and how the board behaves on the water. So the "boom-height" in my case would be fixed in relation to the power-center of the sail. Thus having an extra gap between the pulley would mean that the height of the boom, compared to the deck of the board, would be unnecessarily height. This is most noticeable on larger sails where the boom tends to end up fairly high (about chin-level on Formula sails) , and I always strive to have a small gap at the pulleys (maximum around 2cm, but never 0 cm as then one can not fine-tune the downhaul).

For wave-riding you also want to avoid a high boom position as this reduces the reach of the arms and limits the body movements and the ability to put pressure on the rail of the board etc. So it is not about "closing the gap", or sail efficiency, in this application.
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