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 Post subject: H18 Spreader Rake
PostPosted: Thu Aug 18, 2005 8:23 am 
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Joined: Fri Jul 15, 2005 10:43 am
Posts: 779
Location: St. Louis, MO
I have read alot about H18 spreader rake. I am finally getting into fine tuning my boat and am wondering if there is a basic formula that is dependant on weight. What are the rules of thumb?

I am just looking for information so I can get this right.

Thanks in advance for the help.

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Nick

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'74 Pearson 30
'84 H16
'82 H18 Magnum
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 Post subject:
PostPosted: Thu Aug 18, 2005 9:06 am 
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Joined: Mon Aug 09, 2004 9:35 pm
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Location: Northern Texas
Here is my input. I was told to rake the spreaders back as far as possible. Since there is only two holes drilled in the rear spreader bars I placed mine in the hole that provided the most rearward rake (hole closest to the mast). I don't know about making more holes to create even more rake because it might affect the structural integrity of the mast under load. Maybe someone else can expand on this. The 18 only has drilled holes in the rear spreader bars vs the tiger which has a threaded bar allowing more adjustments. Sure would be nice to see if the spreaders off a tiger would work on an 18.

As a result of the 18 spreaders only having two possible adjustments for rake, the majority of my fine tuning is left to the diamond wires. All of the literature that I have read about diamond wire tension has been extremely conflicting. Some books say to make the diamonds tight to prevent the mast from bending into the slot between the jib and the main. Other books say to leave the diamonds loose to the point where they touch the mast approx. three feet up from the turnbuckles. I don't know which one is correct, but I base my diamond wire tension on weight of the crew and skipper and wind conditions. However, now I have gotten completely off the subject of spreader rake so I will let someone else finish up.


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 Post subject:
PostPosted: Fri Aug 19, 2005 7:24 am 
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Since there is not much to do with the spreader rake, I will move to th ediamond wire tension. I too have heard as many different stories as there are people. I would like to hear what people have to say about spreader rake/diamond wire tension for a heavy crew, 400lbs (I like to think of us as a heavy air crew :lol: ). Right now we sail for fun and don't race. So we are looking mostly for hull flying fun. I may get into racing later, but will owrry about that later.

Thanks again,

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Nick

Current Boat
In the market
Previous boats owned
'74 Pearson 30
'84 H16
'82 H18 Magnum
St. Louis, MO


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 Post subject:
PostPosted: Fri Aug 19, 2005 10:00 am 
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Joined: Mon Aug 09, 2004 9:35 pm
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Location: Northern Texas
Here is what I have set up on my 18. I have three marks on my mast. One mark is at 12" up from the connection between the diamond wire turnbuckles and mast rotator, the second is 12" up from that which results in a mark 24" up from the connection, and the final mark is 12" up from that which results in a mark 36" up from the connection.

When we race, our total crew weight is approx. 396 pounds. We adjust the diamonds using a bungee wrapped around the mast and diamonds to provide a somewhat even tension. In heavy air, we adjust diamond wire tension to almost touch at the 36" mark. Medium air, at the 24" mark, and light air the 12" mark. Currently, we have our diamonds set at approx. 27" and we have been sailing in 15-20 mph winds. We have sailed in light winds, 2-5 mph, with this setting and got our hiney's kicked.

On the other hand, one of our most rivaled competitors had their's set to touch about 1" up from the rotator and got spanked so bad that they were tremendously upset. They also weigh about the same on the boat as us.

Take in mind though that these settings are based on crew weight. I have to readjust when my daughters go out on the boat. They look just like stick figures so the crew weight is about 100 pounds lighter. I have to make the diamonds tighter when they are on the boat by about 6-8".

With these settings we are able to put the windward hull at a 75 degree angle to the water. Lots of fun! However, when racing, we keep the hull at a point where it just kisses the surface of the water. Daggerboard and rudder tip is normally still in the water.

Well, hopefully someone else will chime in on this, but these are the settings we use. You can give them a try and see if they will work for you.


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 Post subject:
PostPosted: Fri Aug 19, 2005 11:51 am 
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Location: St. Louis, MO
Just to be sure I understand what you are trying to achieve with the tension...
In heavier air you want to spill some of the wind from the main so you can keep the boat clser to horizontal and not heel over as far, so you use lighter tension so the mast can bend more. In lighter air you want to harness as much power from the wind as possible so you use more tension so the mast bends less.

An I understanding the idea behind this? I don't like to adjust the boat without understanding why I'm doing things. It's that whole teach a man to fish thing.

Thanks

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Nick

Current Boat
In the market
Previous boats owned
'74 Pearson 30
'84 H16
'82 H18 Magnum
St. Louis, MO


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 Post subject:
PostPosted: Fri Aug 19, 2005 12:13 pm 
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Joined: Mon Aug 09, 2004 9:35 pm
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Location: Northern Texas
Quote:
In heavier air you want to spill some of the wind from the main so you can keep the boat clser to horizontal and not heel over as far, so you use lighter tension so the mast can bend more.


Somewhat correct. As I understand it, bending the mast creates a difference in size of low pressure and high pressure areas in the airfoil (sail). In essence, you are not actually spilling air off the sail, but instead making it flow faster. Might be wrong or I might actually be saying the same thing you are just in different terms.

Quote:
In lighter air you want to harness as much power from the wind as possible so you use more tension so the mast bends less.


Correct. But it has a lot to do with high and low pressure areas again. I will send a link tonight as I can't access the website that explains this in greater detail right now.


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 Post subject: H18 Spreader Rake
PostPosted: Fri Aug 19, 2005 3:07 pm 
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Joined: Mon Jul 04, 2005 10:13 am
Posts: 666
Location: Nepean S.C. Ottawa, Canada
Please post the link on the thread, I am just as confused as Nick. Our crew weight runs around 320 lbs, or 400 with my 11 year old on board.

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'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'


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 Post subject:
PostPosted: Sat Aug 20, 2005 1:52 am 
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Joined: Mon Aug 09, 2004 9:35 pm
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Location: Northern Texas
Here is the link though it doesn't really explain it in great detail as I first thought. You might want to pose the same question there and get some answers from Chris.

http://flumpmaster.dnsalias.com:91/drupal-4.3.2/?q=node/view/929

The link also discusses a little more than diamond wire tension. You will notice that he says to do the opposite of what I say with regards to diamond wire tension. I have just learned through trial and error that the opposite works better for my boat and crew weight. But this is where I started all of my adjustments in the beginning. Hopefully this will work for you guys. :D


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 Post subject:
PostPosted: Mon Aug 22, 2005 10:26 pm 
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Joined: Mon Nov 22, 2004 7:18 pm
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Location: League City, Texas, USA
Mike - I'm with you on diamond wire tension on the Hobie 18. I screwed up in my post on http://texascitydike.com

I meant to say us the 36" setting in heavy wind and the 12" setting in light wind. The theory being relax the diamond tension in big wind so the mast will bend on it's minor axis (the thin side) when the downhaul and main sheet are pulled in tight. Bending the mast in the middle like this will flatten the main in the middle, reducing power with less drag than sheeting out armfuls of main sheet.

The section of the post on prebending the Hobie 18 mast with comptip still holds true in my opinion - avoid prebend.

I will go back and edit the post.

Thanks Mike.

Chris.

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 Post subject:
PostPosted: Tue Aug 23, 2005 7:41 am 
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Joined: Mon Aug 09, 2004 9:35 pm
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Location: Northern Texas
Chris,

Don't edit the post! How do you expect me to keep winning if you let everyone know the secrets! :twisted: Just kidding! :P

I had read the post on the TCDYC website some time ago and after referencing back to it I was wondering if I had not made a mistake myself.

Hey, see you at Ruff Rider!

Wichita Falls Mike


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 Post subject:
PostPosted: Fri Aug 26, 2005 8:42 am 
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Joined: Fri Jul 01, 2005 9:26 am
Posts: 25
Location: Loveland, CO
If you can find a copy of "The hobie 18 performance manual" by Phil Berman. It is very detailed and discusses all the adjustments to make based on crew weight and wind speed.

I am sailing faster than ever after making the suggested adjustments.
8)
enjoy,
Jason


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 Post subject:
PostPosted: Sun Aug 28, 2005 6:08 pm 
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Joined: Tue Jul 05, 2005 8:45 am
Posts: 759
Location: Clinton Lake Lawrence, KS
Phil Berman's book is a litany of detail (well worth the read for basic 18 theory). My comments are based on racing at or slightly above minimum crew weight (Paul and I weigh 305). The big message I get from Phil is the 18 main is flat and a flat sail means more RPM (speed) which is great for us at a light weight.

When not racing I, like everyone, am primarily interested in two basic settings to cover everything for "real windy" and "wish there was a little more wind" (besides if we did everything Mr. Berman wanted us to do it would be dark before we got off the beach).

Spreaders are forward medium and heavy. Mast rake as far forward as possible for medium, one hole back for heavy with shrouds adjusted accordingly, tight(med) & tighter(heavy). The diamond wire set "just tight" on the leeward side when going to weather, which must be checked on the water. This is somewhere between the 24" and 36" marks on our mast (since we're light weight we go loose in light air also i.e. towards the 36" mark, heavy crews will go to 12" in light air). Diamond tension can be easily set by honking in your main and downhaul.

After that the only viable adjustment on the water is downhaul.

Keep the main flat for speed.

That's my two cents, this is a great topic.

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