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Kona One with an Aerotech Zenith and an RDM mast
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Sailboarder



Joined: 10 Apr 2011
Posts: 331

PostPosted: Tue Aug 20, 2013 2:26 pm    Post subject: Reply with quote

I used to put more typical downhaul on mine, a 9.0. When it bulges in the middle, you kind of loose the gust absorbance of the sail. It doesn't let wind out in the gusts anymore.

If I put less downhaul to have even twist, and less outhaul in order to keep the looseness, the loose area flaps quickly in the wind.

I was supported remotely in rigging the non-typical sail by Steve Gottlieb, Aerotech and by the rigging guides. Kona racers also helped on the beach: guys who know the sail but also do raceboard and Formula.

BTW, to be more accurate, I don't put zero downhaul on it. From neutral, it is probably an extra and easy 2 cm. Just enough to be able to rotate the battens with a firm pump, (the bottom one by hand), with a still tight leach.
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Darbonne



Joined: 27 Jan 2012
Posts: 109

PostPosted: Tue Aug 20, 2013 2:47 pm    Post subject: Reply with quote

Sailboarder, after much trial and error and advice. I rig my 9.0 much the same way. I too have to push the batten above the boom around the mast. I have not sailed in high winds yet, but the loose setting works well in the 10-15 mph range. Does your 9.0 have a tack strap?

Here is a little boring footage from my session last weekend. Wind was about 13 mph. Flirting with plane.

http://youtu.be/O0hZdBR4ZbM
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Sailboarder



Joined: 10 Apr 2011
Posts: 331

PostPosted: Tue Aug 20, 2013 4:11 pm    Post subject: Reply with quote

Darbonne wrote:
Sailboarder, after much trial and error and advice. I rig my 9.0 much the same way. I too have to push the batten above the boom around the mast. I have not sailed in high winds yet, but the loose setting works well in the 10-15 mph range. Does your 9.0 have a tack strap?

Here is a little boring footage from my session last weekend. Wind was about 13 mph. Flirting with plane.

http://youtu.be/O0hZdBR4ZbM


You are right, boring to watch! Smile Nothing wrong about it, and I do similar sessions often, but these are not spectator friendly...

About the sail: with a strong pump, my battens switch side, apart from the bottom one, not the one on top of the boom. Not sure what is better. Mine is an older sail, without the tack strap. I can see how the strap would help in smoothing the bottom sometimes.
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konajoe



Joined: 28 Feb 2010
Posts: 103

PostPosted: Tue Aug 20, 2013 6:48 pm    Post subject: Reply with quote

Nobody ever said anything about rigging or sailing a 7.4 with too little downhaul. The range of the optimal amount of downhaul is sail model, year, and brand specific. It is determined by the sail designer and is either printed in the manual in the sail bag, or is available online. It varies, alot. Being an expert on rigging one sail (because the manual for that sail was read and fully understood) doesn't make one an expert at rigging every sail on the beach. But it is sooooo common to see that.

I don't understand why folks think they know more than the sail designer. Sometimes, I guess it pays to be a dumb-ass like me.


Last edited by konajoe on Wed Aug 21, 2013 8:11 am; edited 1 time in total
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nodak



Joined: 13 Nov 2012
Posts: 92

PostPosted: Tue Aug 20, 2013 11:10 pm    Post subject: Reply with quote

KevinDo wrote:

Dmitry, have you tried rigging the sail with just enough downhaul to cause the leech to go slightly loose? Maybe 2 panels?

-Kevin


Yes, the top or even top 1 1/2 panels of the sail were rather loose. It worked terrific with more down haul in high wind. I'd never rigged that Zenith with an RDM before (in my case it was the now discontinued Backbone 460 RDM). Each time I'd apply more down haul with a SDM mast the entire sail went limp; i.e. too much loose leech.

Here's an insight I'd received once from a fellow name Tim Ortlieb regarding one of my former Ezzy sails: "The head of the sail will have a profile that enableshe sail to lighter and heavier winds with maximum comfort, range, and speed...the top of the sail's purpose is to NOT interfere with the more efficient middle section of the sail. The reason you get more efficiently in light wind with a loose head is that you are reducing the upper stall. If you tighten your head too much, the sail will not pump onto a plain easily and will hit a "wall" and stop accelerating, etc.". So that's as far as my awareness of the importance of loose leech goes.

My upper leach was flappy and loose with lots of down haul using the Backbone RDM.

I'm using gear that had never never meant be rigged together, but it works great. O yeah, I also used the 39 cm Select Edge Freeslam. It blew about 20 mph. I think this weekend I'll put a 42cm fin on there to see what happens. Who new the old boring Zenith could be so much fun? I'll take some pictures too.
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konajoe



Joined: 28 Feb 2010
Posts: 103

PostPosted: Wed Aug 21, 2013 8:58 am    Post subject: Reply with quote

Hey Nodak. Which standard diameter mast do you normally use with the Zenith? Once you answer that question, maybe someone on the forum can tell us why the it took so much more downhaul tension to get the trailing edge of the top panel to get floppy when you used the rdm.

You WERE using the same base and pulley system in both cases, weren't you?
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nodak



Joined: 13 Nov 2012
Posts: 92

PostPosted: Wed Aug 21, 2013 10:53 am    Post subject: Reply with quote

konajoe wrote:
Hey Nodak. Which standard diameter mast do you normally use with the Zenith? Once you answer that question, maybe someone on the forum can tell us why the it took so much more downhaul tension to get the trailing edge of the top panel to get floppy when you used the rdm.

You WERE using the same base and pulley system in both cases, weren't you?


Different bases and pulley systems used in both cases. Originally rigged the Zenith with a 460 Gulftech 55% Carbon SDM (unknown bend curves), Chinook US Base and aluminum extension.

Now rigging Zenith on a 460 Backbone 90% Carbon (65/75 curves), Streamlined Europin base with carbon extension.

Like I'd mentioned I'll take a photo this weekend if anyone still cares.
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konajoe



Joined: 28 Feb 2010
Posts: 103

PostPosted: Wed Aug 21, 2013 2:13 pm    Post subject: Reply with quote

So you're saying that the downhauling effort needed to get the trailing edge of the top panel to be floppy, for example, was much harder when you used your rdm. And you're thinking that the reason is that your rdm is much stiffer than the sdm you used in the past. Correct? If so, hopefully one of the mast experts will chime in.

The only other things that could have made it harder to pull the downhaul is a crappy pulley system, criss-crossed lines, or poor quality or over-sized downhaul line. But it sounds like you probably used a better system with the rdm, and you still had to pull harder to get the same amount of floppiness in the leach.

Had you been out on your Kona One in that much wind before? They really do have the ability to light up.
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swchandler



Joined: 08 Nov 1993
Posts: 5479

PostPosted: Thu Aug 22, 2013 3:03 am    Post subject: Reply with quote

nodak,

The Gulftech mast is most likely a 64/76 bend curve. I know my Gulftech RDMs are that bend curve, and usually most manufacturers will engineer both their SDMs or RDMs to produce the same bend curve. That said, it's my understanding that RDMs require a bit more downhaul, and maybe a little extra luff length. I know one of my sails has different luff lengths specified for SDM versus RDM. It's not a lot, maybe 1-2cms.
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jingebritsen



Joined: 21 Aug 2002
Posts: 2293

PostPosted: Sat Aug 24, 2013 6:04 am    Post subject: Reply with quote

interesting swchandler. i've found the aerotechs and others require less down haul with RDM's. otherwise the entry is too lean and the draft moves back tons. SDM's in my sails and NP's, and others, nearly always lead to a more stable feel, but at the price of losing a bit of low end. RDM's lose quite a bit of top end.

i've experimented a bit with the zenith. i've also sailed it first in the USA, if not the world at rufus, oregon. we rigged it at first like any other sail on a SDM, with lotsa D/H. it had no balls. backed off the tensions, it sailed better. backed it off some more, better yet. we were doing a catalog photo shoot, and i had been sailing stuff between 5.2 and 7.0 sizes. the wind was 15-28 or so.

did some plunking around in florida with the 9.0 and 7.4. i've come to appreciate using them with only very least amount of D/H until the wind gets quite lively. my favorite zenith is the 7.4 size. it's brilliant for its application on a long board. every time i increase the D/H in moderate conditions i usually regret doing so.

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