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PostPosted: Fri Jul 11, 2014 10:23 am 
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Ok experience racers/sailors,

Let's discuss mast tuning for optimal racing. I have been bouncing back and forth between the H18 and H20 and I have learned to watch the mast on the H20 as a major factor in boat speed. Pre-bend and on the water adjustment with the downhaul is critical in different wind conditions to optimize boat speed and keeping the boat flat and powered up.

The big difference is that on the H20 is that I can get the mast to prebend/bend on the major axis and almost match it to the luff of the sail. On the 18 I cannot. On the H18 we can only get the mast to bend on the minor axis and I believe this would only be good for depowering the boat. Thus, with a heavy crew, No prebend (but diamand wines tight)and just keeping the mast straight would make sense to me. Extreme Downhaul bends the mast on the Minor axis again and creates this real awkward looking rig. Traveling out and not contorting the rig seems like the better choice to maintaining our pointing ability

Thoughts?????

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H18 '85
H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
Fleet 259 Central Coast California


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PostPosted: Fri Jul 11, 2014 12:25 pm 
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Location: Nepean S.C. Ottawa, Canada
We debate this every week over burgers and beer after Club racing....
with Tornado's, NACRA F18, NACRA Inter 20, H18, and NACRA 500 in our fleet.

Although the small axis bending of the mast adjustment is there on the H18, it does not seem to work as well as on other cats.
Am I missing something?

Have you made a mark 48" from the base of the mast, and measured the distance from that mark to a bow tangs?
Should be somewhere between 103" to 107". After that, we use traveler, mainsheet, outhaul, downhaul, mast rotator in that order. We pre-tighten the leech line on each sail before racing, especially on the jib.

Where do you fly your tell tales?

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1989 Hobie SX18 Sail # 1947
'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'


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PostPosted: Fri Jul 11, 2014 1:02 pm 
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I sail my rig about 105.5. That has worked for me and our combined crew weight (335lbs). On the main I sail the windward tell tails flying 100% on lower tail and upper seem random. Leeward main tail I have given up on and the tails on the trailing edge of the main need to be flying at least 50% of the time.

Obviously the jib is 100% upwind on both sides. Downwind 100% leeward and I sacrifice windward according to my desired boat speed.

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H18 '85
H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
Fleet 259 Central Coast California


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PostPosted: Sun Jul 13, 2014 4:36 am 
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Location: Jersey Shore
It would be difficult to pre-bend the H18 mast as the spreaders don't rake back very far. We run the diamond wires snug to keep the bottom of the mast relatively straight but no prebend. The top of the sail will open up with downhaul and mainsheet tension as the comptip bends. We do all the power tuning with downhaul- if the hull flies too much, applying more downhaul will lower the CE of the rig, move the draft forward to balance the helm, and open up the top of the mainsail to reduce drag. Our general procedure for puff management would be spot the puff, head up slightly and/or crack the sheet slightly to maintain speed and keep the hull from flying excessively, crew cranks on more downhaul, skipper sheets back in as the boat settles down. If the puff subsides, ease both mainsheet and downhaul. We would never dump the traveler down at all until the downhaul blocks are within about 1" of the gooseneck fitting, and usually we would wait until the downhaul is bottomed out before considering dropping the traveler.

sm


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PostPosted: Sun Jul 13, 2014 3:46 pm 
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Location: Bowie, MD
Loosening the diamond wires will de-power the boat. We set diamond wire tension for the lowest wind speed we expect to see during that race since you obviously can't adjust diamond wire tension during the race. Better to de-power in the puffs with your adjustables (downhaul, sheet, and traveler) than to find yourself underpowered in the lulls.

My wife and I are light (near min weight). We start loosening diamond wires around 18 kts.

Caveat: Steve always beats us in heavy air (for that matter, he pretty much just always beats us)


Last edited by jim-doty on Mon Jul 14, 2014 9:25 am, edited 1 time in total.

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PostPosted: Mon Jul 14, 2014 8:52 am 
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Is there any restriction on downhaul design or construction on the 18 with regard to one design?

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H18 '85
H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
Fleet 259 Central Coast California


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PostPosted: Mon Jul 14, 2014 9:23 am 
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Location: Bowie, MD
5.1 Sail downhaul purchase shall not exceed 8:1
purchase. Rigging of downhaul and related control
equipment may be installed to the owner's
and skipper’s specification, provided it does not
structurally weaken the mast or the boat or interfere
with other HOBIE CAT CO. components.
The downhaul attachment point to the sail shall
remain in the same location as supplied by the
HOBIE CAT CO.

You can download a copy of the class rules here:

http://www.hobieclass.com/default.asp?P ... s/10773/0/


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PostPosted: Mon Jul 14, 2014 9:35 am 
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Location: Jersey Shore
jim-doty wrote:
My wife and I are light (near min weight). We start loosening diamond wires around 18 kts.

Caveat: Steve always beats us in heavy air


Note that our tuning styles differ because I'm usually racing at about 60Lbs over minimum weight, so we're always looking to keep some amount of power in the rig, so we keep the diamond wires snug all the time and just tune with comptip bend. If we were running at minimum weight, we would probably have to consider allowing the mast to bend more.

sm


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PostPosted: Mon Jul 14, 2014 9:57 am 
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srm wrote:
If we were running at minimum weight, we would probably have to consider allowing the mast to bend more.


Why give away power before you leave the beach?! I would rather have it all at all times and choose to depower on the water.

Seems to me that maintaining the ability to point while depowering is critical. Traveling out a few inches would allow the sail to remain flatter and reduce drag vs bending the rig with excessive downhaul or mast bend.

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H18 '85
H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
Fleet 259 Central Coast California


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PostPosted: Mon Jul 14, 2014 10:33 am 
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Location: Bowie, MD
Am I not getting a flatter sail when I allow the mast to bend on its minor axis?


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PostPosted: Mon Jul 14, 2014 11:43 am 
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jim-doty wrote:
Am I not getting a flatter sail when I allow the mast to bend on its minor axis?


Hmmm, I will have to look at that this weekend. Retrieving the mast rotator closer to center would be important for sure.

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H18 '85
H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
Fleet 259 Central Coast California


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PostPosted: Mon Jul 14, 2014 12:16 pm 
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Location: Nepean S.C. Ottawa, Canada
I am thinking that one of the bigger 'differences' lies in what kind of sailing we are doing.

Sailing on the Ottawa river (actually it's like a lake where we are due to a series of rapids acting as a dam),
when the wind picks up, so does the chop, and the pitch is VERY short.
So once we get up to anything over 15 knots of wind for more than a couple of hours, the chop makes the ride
very uncomfortable. Who has time to fine tune and adjust... we stick with our general settings and use mainsheet,
downhaul and sometimes the traveler.....

Our wind shifts, due to barns and trees and buildings, can also be quite vicious at times.

Sailing in the ocean is much preferred... Chris and Steve, how are the wind shifts on the NJ shore?

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1989 Hobie SX18 Sail # 1947
'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'


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PostPosted: Tue Jul 15, 2014 5:27 am 
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Location: Metuchen NJ
John,
there are a couple dynamics happening at the shore:
on what I'd call a normal sunny day in the summer, you'll have a mild to moderate W to SW breeze. by 3pm the land heating causes the SSE seabreeze to kick in, so the wind backs to that point. if its been a hot day the breeze continues to build during the afternoon to at least 15 kts. and will eventually die off around or after sunset.

another example happened this past weekend during a regatta:
Sat. had light easterlies (in the west end of Raritan Bay) which kept moving 'right' throughout the day with each gust and increase in wind speed, to it got to nearly dead south. by late afternoon it moved to SSW and blew 15 kts.
Sun. started with light south wind, which also clocked right and built to a strong SSW wind, which is typical for inland areas which includes western Raritan Bay.

of course all that changes when there's weather around.

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Chris
'88 H18SE Arís


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PostPosted: Wed Jul 16, 2014 6:50 pm 
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How are you measuring your diamond tension? Pressing wires against the mast or...?

At one point early in the season I had my rig with diamond wires loose enough to touch the mast around 30'' up from where they meet, and the boat was a pig until I figured out how loose they are. Now they're snug, but I can still just about get them to touch at 12'' up the mast(with much better performance). I'm usually at least 50-80lbs over minimum.

Are you guys doing anything with spreader rake other than as far back as the setting will allow?

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Tom
Fleet 259, Central Coast CA
H18 ('81)
H18 ('85)
H20 ('97)
H18 ('78)


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PostPosted: Thu Jul 17, 2014 1:22 am 
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Location: Bowie, MD
I use a Loos gauge to try to get equal tension on both sides. Probably way to anal, but it helps get rid of one excuse for those nagging questions like "why am I pointing better on this tack than the other?"


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