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Old 24th July 2008, 08:32 AM   #1
sam 2007
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Default Retro Tuning

Roger,
I have an 8.0 and a 6.5 Retro that I'm having a little trouble rigging on days when the 8.0 is a too much but the 6.5 isn't enough. I rig the 8.0 on a 75% Powerex mast and the 6.5 on a 75% Sailworks mast.

For the 8.0 when I apply medium downhaul the batten above the boom moves back but the top of the sail doesn't show much looseness. To get the top to open the batten is way behind the mast and I don't have much power.

The 6.5 kinda works in reverse of the 8.0. To get the batten to move beside the mast so that it will rotate the top of the sail is very loose and again I do not enough power in medium wind.

My 5.5 and 10.0 Retros rig about like I think they should.

Do you any suggestions about what I might do to get more range out of my 6.5 and 8.0.

Thanks.

Sam
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Old 24th July 2008, 10:46 AM   #2
Roger
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Hi Sam,
Sounds to me like you have some minor mast compatability issues here.
First, I would forget about the top of the sail.
The only way to get the batten above the boom cutout to be at the midpoint (fore and aft) of the mast at the same downhaul tension that gives you the scallop in the top of the sail running in to the tuning mark is to have a fully compatable mast.
You can control (with downhaul tension) the position of the front of the batten above the boom, but you cannot change the bend in the top of the mast which gives you the scallop.
I would worry much less about the top of the sail as there is nothing you can do besides try different masts until you get the correct tuning on the front of the batten above the boom at the same tension that creates the correct scallop in the top of the sail.
So, for the 8.0 m2, just downhaul it until you get the batten above the boom back to the mid point of the mast. This would be the max power light air "tune".
As the wind comes up and you want less power from the 8.0 m2 Retro, downhaul it some more until the mast is just able to pass behind the back of the mast.
More downhaul than this won't do much for you and may make the sail very "on/off".
For your 6.5 Retro, again there's not much you can do to get both of the tuning points
correct if your mast is too soft in the top.
So, again, since you can't change the bend characteristics of the top section of the mast, do the best you can to tune by the front of the batten above the boom and let the top do whatever it does.
You might want to check with some of the folks you sail with and see it you can borrow some different 460 and 490 masts to see if there's a difference in how your sails rig.
Wish we were closer together as I have several masts you could try and I'm pretty sure we could get your Retro's to tune correctly.
If you have any "back up" masts, you could try them as well.
Sounds like the bend characteristics in the top sections of your masts is off, the top of the 490 cm being a little too stiff and the top of your 460 being a little too soft.
Hope this helps,
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Old 26th July 2008, 07:57 AM   #3
sam 2007
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Roger,

Thank you for writing. I'll try the 460 mast on the 8.0.
If 2 masts are the same length and MCS can they still have different stiffnesses in their top halves.

I rig my 5.5 and 10.0 Retros on 75 % Maui Sails masts and they seem to work better.

Another problem - the strap at the top of my 8.0 broke recently. I have extra headcap straps from my 5.5 and 6.5 and hope to find someone local to sew one on. Would it be ok to sew the strap on the outside of the top of the sail? I think that would be easier for someone to do that isn't familar with windsurfing.

Thanks.

Sam
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Old 26th July 2008, 07:59 PM   #4
Roger
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Hi Sam,
What year is your 8.0 m2 Retro?
I've always used 490 IMCS 27-29 masts in my 8.0/8.5 Retro sails.
On your question:
" If 2 masts are the same length and MCS can they still have different stiffnesses in their top halves."
Yes, there can be a small difference. The overall bend ratio can be the same (measured at the mid point with a 30 Kg weight) but the idividual bends can be somewhat different and still give the same deflection at the mid point.
The head cap issue is a tough one.
The top of the sail really needs to be opened up to get to all load bearing fabrics up in the top.
Sewing a strap on the outside might work, but this is something I'd send back to the loft.
So, your Powerex 75% mast that you use in the 8.0 m2 is a 490 cm IMCS 27-29 or something different?
I wouldn't think a 460 cm IMCS 24-26 would work at all in your 8.0 m2.
Hope this helps,
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Old 27th July 2008, 09:06 AM   #5
sam 2007
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Roger,

I checked my 490 Powerex 75 % mast and the IMCS is 29. The 460 Joystick is 25. Both of those masts should work well according to the Sailworks rigging guide.

My sails are 2004s and the masts are about the same age. I agree with you that the 490 mast is too stiff for the 8.0 Retro and the 460 too soft for the 6.5 Retro. However, I don't understand how come they don't work since that's what Sailworks recommends. The Joystick 460 is the ideal mast for the 6.5 Retro from their chart.

Sam
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Old 27th July 2008, 09:02 PM   #6
Roger
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Hi Sam,
Yes, that's what I thought also.
Are you sure you have batten tension in all the battens in both these sails?
Have the always rigged this way?
Short of testing (or having it done) your masts, there is no way to tell if it's the masts or something else.
Can you put your masts in someone else's Retro's and see if the same thing happens?
I'm not sure what to tell you.
R

Last edited by Roger; 29th July 2008 at 02:36 AM.
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Old 28th July 2008, 09:08 PM   #7
Brian S
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Sam,

FWIW, I have the same 8.0, 6.5 sail combination, and I rig them on powerex 75% carbon masts. I think they're all about 2001/2002 vintage. My 8.0 rigs on a 490/IMCS 29, and my 6.5 rigs on a 460/IMCS 25.

I use Roger's "batten above the boom method". The scallops in the leech don't quite look like the rigging guide photos, but the sails both feel good, and each higher batten twists more than the batten below it, both on the ground and while sailing. No matter what downhaul I use, I don't get the exact look shown in the rigging guide. Also, the luff length doesn't quite match the markings on the sail either. I'd say they're within about 3-4 cm though.
Brian
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Old 2nd August 2008, 10:36 PM   #8
sam 2007
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Roger, Brian,

I'll check the batton tension on my 6.5 next time I rig it. I just got a new 8.0 Retro this morning and will let you know how it rigs on the 490 mast.

Thanks for help and I'll keep you posted.

Sam
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Old 4th August 2008, 05:51 PM   #9
crazychemical
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i discovered a small trick which may work .. when i try to get into the footstraps of my GO139, which are fully exentrated i get into the front one first as soon as i start planning (thats the easy part), then i start moving my backfoot back relatively fast and i place it behind the rear strap so that its fully on the tail. when i gain more speed i go more upwind and then to go a bit more downwind again i place my backfoot quickly enough in the backstrap and i start gliding across the water with the biggest of ease.
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Old 7th August 2008, 07:01 AM   #10
vikingsail
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Sam what year is your powerex mast?
there was a time, several years ago, when the powerex masts were not bending properly and it created problems when rigging. I had two powerex 430 zwave masts, same imcs, different years, which rigged on a 4.8 totally different.
(Roger you may remember some of our discussions about this.)
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