Hey J. Same here. But, I don't normally go by numbers for outhaul. I go by looks of the sail profile. However, the only thing I can suggest is some electrical tape wrapped around the tube as an outer marker. Maybe even a tape measure if you can be bothered, which I use for new equipment anyway, as I don't trust the numbers printed.

You can still count, no? The number of holes on the boom end tends to be pretty closely matched to the actual measurement.
Also, if you are using Al booms, they get scratched where they are regularly set. Carbon booms can be marked with a drop of paint. I bought one second hand and the previous owners marks are still visible after probably more than 30 sessions on the water

I never read mine.

Numbers wore off my carbon boom.
I marked with white paint pen and dogy clear coat, still came off.
Tried again, came off. Cant see anyway as I need new glasses and not leaving beach so I’ve been setting boom wherever it lands now.
And my ezzys are all seeming like they need much less outhaul these days, not sure why.

I have painted bands every 10cm and then put a hard wearing clear coat over the top. was lasting fine until I let my brother use it and drag it up the beach, but before I hardly had a scratched them off after around 15 uses with the boom, moving it around every session for different sails and stuff.

mark62 said..
The numbers aren’t strictly correct, the boom length varies depending on boom height, shorter with a low boom and longer with a high boom. Most people simply adjust the boom length accordingly after setting the down haul, so the printed numbers aren’t needed.

The idea that boom height makes a difference is attractive, but it doesn't stand up to maths.
Pythagoras theorem kills it. Say you have a small wave sail with 150cm outhaul and the boom perpendicular to the mast in the middle of the cutout.
Moving the boom up or down by 10cm changes the length to the clew by 0.3mm.
Even a 20cm deviation results in only 13mm change.
The change is relatively smaller as the boom gets longer. At 200cm a 20cm move on the mast is only 10mm at the clew

It’s got nothing to do with Pythagoras fwiw. It’s about how the sail loads are transferred differently depending on boom heights. Next time you stop to adjust outhaul maybe adjust your boom height instead. It does the same thing more or less.

that aside sail designer recommend adjusting outhaul to suit boom height. As a group we need to stop telling people to ignore rigging instructions.

with my sails 0.5cm outhaul adjustment makes a noticeable difference.

Mr Milk said..
Yes, but a 5mm adjustment to outhaul is only 25% of a boom length adjustment. The boom usually stays set at the same set of holes.
Raising or lowering the boom affects the vertical leverage element of the aerofoil. Outhaul varies the belly.

Yep it effects leverage and mast foot pressure, but raising or lowering the boom also effects belly below the boom. Lowering the boom increases tension at the clew and removes shape from below the boom. Opposite for increasing boom height. ie. if you want more outhaul then lowering the boom height does a similar thing. that has been my experience…

if you need a more experienced view. Specific point is 9.37 in but you may find this whole video informative.

Gestalt said..

Imax1 said..
I never read mine.

I use one boom for my entire quiver… so i have to read it to set things correctly.

I never read mine because things change depending on how much downhaul I use. On a bigger sail the difference can be more than one hole . I set the downhaul , pull lightly on outhaul with my fingers in the eyelet and set the distance with about 2 cm gap. It’s a vibe thing. Same with downhaul , I do visual cue on top crease, depending on wind. On one of my sails , which I marked with a texta needs 2 cm less on downhaul settings. I like to have about 2 cm gap between pulleys so I can play with my ratchet downhaul if the wind picks up. Some printed numbers can be out on sails. I had a NP sail that was 12 cm out. Not something you would expect from NP. Obviously a printing error. So I’ve learnt to rig by feel not numbers , that’s why I don’t read boom numbers.

Gestalt said..

mark62 said..
The numbers aren’t strictly correct, the boom length varies depending on boom height, shorter with a low boom and longer with a high boom. Most people simply adjust the boom length accordingly after setting the down haul, so the printed numbers aren’t needed.

The idea that boom height makes a difference is attractive, but it doesn't stand up to maths.
Pythagoras theorem kills it. Say you have a small wave sail with 150cm outhaul and the boom perpendicular to the mast in the middle of the cutout.
Moving the boom up or down by 10cm changes the length to the clew by 0.3mm.
Even a 20cm deviation results in only 13mm change.
The change is relatively smaller as the boom gets longer. At 200cm a 20cm move on the mast is only 10mm at the clew

It’s got nothing to do with Pythagoras fwiw. It’s about how the sail loads are transferred differently depending on boom heights. Next time you stop to adjust outhaul maybe adjust your boom height instead. It does the same thing more or less.

that aside sail designer recommend adjusting outhaul to suit boom height. As a group we need to stop telling people to ignore rigging instructions.

with my sails 0.5cm outhaul adjustment makes a noticeable difference.

Whilst Pythagaros lived on the windswept Greek Island of Samos, he clearly didnt windsurf much. When I change my boom height, the outhaul string either tightens or loosens.

I checked. Rigged my old NP 5.4 Combat in the backyard and lined up a carpenters square by eye.
True, set in the middle of the cut out it deviates from perpendicular a few degrees, but it gets square at about 1/3 from the bottom.
There isn't much more than 20cm of vertical movement possible from there, so my maths is good to the financial modelling standard even if it doesn't pass engineering.

Jasonwave said..
On top of my ailing eyesight, the length numbers on my boom are becoming unreadable from scratching. Is there a lasting way to highlight the typical lengths I use ?


Mast extension seems to be going the same way too.

Can you buy a new tail piece for your boom…

or just replace it.

Mr Milk said..
I checked. Rigged my old NP 5.4 Combat in the backyard and lined up a carpenters square by eye.
True, set in the middle of the cut out it deviates from perpendicular a few degrees, but it gets square at about 1/3 from the bottom.
There isn't much more than 20cm of vertical movement possible from there, so my maths is good to the financial modelling standard even if it doesn't pass engineering.

Proper math is always correct though. ;)
I've now taken a look at my Severne S1 (5.2) laid out flat on the ground, using two straight rulers and a digital angle measurement. My normal boom-height setting gives about 100 degrees between the upper side of the boom and the mast sleeve. Raising the boom about 5cm gives a reading of about 102 degrees. So if we assume that the written numbers (161 cm) are valid at 90 degrees, then following boom-lengths are needed:
@ 100 degrees: 161/cos(10)≈163.5 cm
@102 degrees: 161/cos(12)≈164.6 cm

Seems to me there is not a lot of wind.

Not about niggles, it’s about correcting poor advice so people who aren’t as experienced don’t get lead up the garden path.

just yesterday i commented on a mates wave sail that it looked way over down hauled for the wind. he replied he needed that much for rotation. After the session i asked to look at and tweak his sail.. i was left with the thought that somethings not right… on further discussion he's using an off brand 430 mast in a sail that requires a 460 and went on to say the numbers were out because he has to under downhaul the sail even though it look over downhauled…he went on to say that he needed less outhaul or the sail was too flat. Said, i’ve got a 460 maybe i try that next time…

Fwiw my mate has had rigging issues since he got the sails but is constantly using off brand masts and extensions which is creating outhaul issues, rotation issues etc. so Yesh, the numbers and gear do matter.

Subsonic said..

Imax1 said..
Seems to me there is not a lot of wind.

Yeah, lack of wind always gets seabreeze niggle arguments going. I really don’t get the fuss.

set the boom with more than enough extension, downhaul the sail all the way, bump the boom extension into the correct position. Simples?

Ok, slightly more complex if you’re rigging a cambered sail, but not by much.

Not much more complex with camms ,just leave 3cm gap.