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PostPosted: Wed Jul 25, 2012 11:04 am 
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I just tightened the forestay on my 18, so one hole of the chain plate hangs out of the bottom of the roller furler, and holly blast off!

The boat is soo much faster. Before my buddy was easily able to keep up with me on his 16, and now I can blow him away.

I chased him down half way across the bay and caught him flying a hull the whole way.

I also tightened the diamond wires from the loose setting (able to push them in and touch the mast 36" from the rotator bolt) to the medium setting (able to push them in and touch the mast 24" up from the rotator bolt)

The bows are digging into the water and the boat and I almost flipped twice, but, wow. Super fun.

I think I am going to back the mast off one hole and try it again this weekend.

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PostPosted: Wed Jul 25, 2012 6:07 pm 
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Interesting. Have you measured your mast rake? Measure up 48" from the bottom of the mast and make a mark. Now, measure from that mark to the bridal pins. You should be somewhere in the range of 105" - 107". What's your current (improved) measurement and how much would you estimate you reduced your rake by shortening the chain plate?


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PostPosted: Wed Jul 25, 2012 6:08 pm 
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aaron-hobie wrote:
I also tightened the diamond wires from the loose setting (able to push them in and touch the mast 36" from the rotator bolt) to the medium setting (able to push them in and touch the mast 24" up from the rotator bolt)

The bows are digging into the water and the boat and I almost flipped twice, but, wow. Super fun.


This makes sense. Tighter diamond wires = less mast bend, more depth and more power. In higher winds, this results in excessive heeling. Speaking of, what kind of winds were you sailing in? Any waves to contend with?

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PostPosted: Wed Jul 25, 2012 9:15 pm 
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It was at 107 inches. I didn't measure it after the adjustment, but I tightened the forestay three holes from where it was. I will measure this weekend. I would guess I am around 105 now.

I must say the boat is a totally different animal. The bows dig like crazy, which is unpleasant considering the smooth stable ride she had before. Also, SabresfortheCup she IS way more tippy. We almost flipped twice, but it was very gusty, and the was three foot chop in areas from excessive weekend boat traffic.

I am shocked by the increase in speed though. We went from being competitive with the 16 to totally blowing it away.

I want to find a balance to make the boat more stable, but still fast. I think I am going to loosen the forestay one hole, and tighten the diamond wires, so they can be pressed into the mast at 12" up from the rotator nut.

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PostPosted: Thu Jul 26, 2012 9:02 am 
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Is that 105-107 inches measured at the furler, or at the hulls?

Thanks,

Mark

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PostPosted: Thu Jul 26, 2012 9:04 am 
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From the clevis pin in either bow tang to the center point of the mast 48" up from the base.

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PostPosted: Thu Jul 26, 2012 9:28 am 
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Great, thanks. I'm curious to see how mine measures. Can you also explain exactly how you're doing the Diamond Wire tension test, and what they "should be" for different wind strengths?

Thanks Again,

Mark

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PostPosted: Fri Jul 27, 2012 6:39 pm 
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Tip ... take that measurement (105"-107") from the bridle clevis pins to 48" "up the mast from the bottom" and measure the mast rake the other way of using a trapwire and make yourself a reference chart ... it is very useful information to have ...

"Other Mast-Rake Measurement Procedure/System: Take a trapwire ... untie the bungie and tie on a piece of line approx 36" long ... take the trapwire w/ line forward to the bridle clevis pin ... mark line ... now take the line aft and note where the mark on the line will line up w/ the gunwale ... measure distance to transom or rear crossbar ...

This is how the mast-rake is measured on most other types of beach cats ... and when you know the #'s ... you can just quickly check the mast-rake on your fellow racers ... by using their trap-wires.

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PostPosted: Mon Aug 20, 2012 12:26 pm 
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Ok, I measured my rake this weekend and found 107". What's ideal for 10 knot breezes?

Aaron-Hobie, what was your new measurement after making your change?

Thanks,

Mark

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PostPosted: Tue Aug 21, 2012 4:29 am 
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You are at the max rake using the phil berman formula, I am running 106 and is working well for an all around rake.

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PostPosted: Tue Aug 21, 2012 8:25 am 
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poolemarkw what's your crew weight, and calm, or rough seas? I don't have the book with me today. They look at the wind, crew weight, and water condition to make the recommendation. In general, I found that if you have a lighter crew all the settings recommended depower the boat, and make you go slower.

I realized that everything they are recommending was making us go slower, but to create a much smoother ride.

I think in general the closer to 105' you put the mast the more power you will have, but the more the bows will dig, and the less enjoyable the ride will be. Also, the rake of the mast will affect your pointing ability, and the amount of weather helm you have, but I don't remember which way does what off the top of my head.

I agree with Little Wing 106' is probably a good number.

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PostPosted: Tue Aug 21, 2012 10:05 am 
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I'm about 170 lbs and my son is around 140. I'll make mine 106" and see how I like it from there. Thanks Again for the help.

Mark

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PostPosted: Tue Aug 21, 2012 10:10 am 
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Cool, let us know what you think. If you feel like you have more power.

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PostPosted: Sat Sep 01, 2012 5:54 pm 
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Hi Aaron,

Based upon the advice of a local guy that used to race (and won the state championship) on his Hobie 18 Magnum, we raked the mast forward until one and a half holes were showing below the furler. I had to sail solo today so I couldn't really push it, but the boat did feel faster. I didn't have any issues (like you mentioned) of the hulls digging in. It felt great on all points. The BIG difference was absolutely NO pull on the tiller. The boat was completely neutral to steer. I loved it. I'm going to keep it there until I find some good reason to move it. I forgot to do the mast-to-bridle measurement but will do that the next time I go.

Mark

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