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PostPosted: Sat Jun 18, 2011 5:55 am 
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Got a quick question for the experience H18 racers. I am familiar with at least two basic tenets of boatspeed in relation to water resistance. One is to keep the stern(s) up to minimize drag induced by the wake, and the 2nd is to try to get as much of the windward hull out of the water as you can to reduce wetted surface. My question is: Which is more important?

As an example, in a recent very light air race, I had my crew just forward of the lee hull/crossbar and I was seated just behind the mast with my eyes glued to the jib telltales. It seemed like there was an awful lot of gurgling/dragging going on on the lee stern. Would it have been better for me to sit on or forward of the windward hull/crossbar? This would get the sterns up more, but place more of the windward hull in the water (visibility is better too). Waves were pretty low, so not a factor in this situation.

Would there be any difference in the answer whether you are beating to windward or gybing downwind?

Just had another thought... I'm about 175 and my crew about 145. Would switching our positions have been a good idea? I imagine it might be tough to reliably read the telltales from the lee hull/crossbar.

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PostPosted: Sat Jun 18, 2011 10:44 am 
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2 weeks ago we raced in light air, when up along side another h18 we were able to pull away by balancing the boat, me on one side and crew on the other, we both had our weight centered about 6" behind the cross bar and roughly equal on both sides. That is where we seemed to find the most speed. I am 200 and the other guy was 165, this was in 4mph winds or so.

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PostPosted: Sat Jun 18, 2011 3:32 pm 
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Your wieght is too far aft!!!!! In light airs, you need to stand a H18 on her bows !!!!!

Think leeward "bridle wires" for you crew's placement ..... if it is really light I (the helm) sometimes end up on the leeward hull as far forward as possible which places me near/on the front crossbar .....

Hint: A "Magnum" Hotstick is very helpful ...

Take time to study the H18 Hull shape some evening while it's on the trailer (a "beverage" may help ...) ... visualize how the water flows along/over the hull ... you want to be as skinny as possible ....

.... also p/u the windward daggerboard to reduce drag ... you don't need that much foil for directional stability in light airs/wind ..... (I don't mess w/ my rudders since a "cam" problem will cost you more then you gain ....)

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PostPosted: Sat Jun 18, 2011 4:30 pm 
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I find that a balanced boat is fastest. You want the lee hull depressed and the windward hull flying if you can, but it isn't always possible. The problem with moving the skipper to the mast is that it becomes very hard to steer. You lose all leverage on the tiller and when sailing upwind, the tiller will interfer with the main blocks. Steering from the leeward side...I wouldn't even try it. It will be very difficult to see puffs coming and steering will be tough because your tiller will interfer with the main blocks.

I also think the "hang on the bridle wire" thing is overkill and makes the boat slower, especially if there is any significant wave action. Every time the bow goes under, the boat will slow down. It also makes the boat somewhat harder to steer because the broad section of the bow is underwater so the boat won't want to turn.

Our upwind light air position is generally crew right behind the front crossbar sitting on the leeward side. Skipper on the windward side sitting on or just in front of the front crossbar, front leg resting on the dolphin striker or mast.

sm


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PostPosted: Sun Jun 19, 2011 6:21 am 
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Did I say to drive the bows under water ... and through waves w/ water passing overtop of the deck ?????

No I did not .....

Yes it is tough to be steering from the leeward side ... but in lite airs it is possible .... especially on a downwind run. Maybe that's why I like to keep my daggerboards partially down and both rudders down also .... I don't "tack" my rudders like the H16's do .... therefore the boat responds to helm input when I want to turn.

As for upwind in lite airs .... the H18 points higher if the boat is running "bow down" ...

As for having difficulty at seeing the "puffs" .... which way are you facing when positioned on the windward side .... vs the leeward side ... were's the wind coming from????

Now I use this technique ONLY in very lite airs .... am being "quiet" on the boat ... and also am not planning to make any radical turns/tacks/jybes .... (so it means you need to plan ahead ...)

And ... in lite airs ... what kind of wave hieghts/action/state are you expecting???

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PostPosted: Sun Jun 19, 2011 11:44 pm 
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In light wind we'd just keeping the transoms out of the water, just making minimum weight this meant both of us would usually drape ourselves over the front cross bar a bit (crew on leeward side).

We also stayed as low and "aero" as possible.

The skipper has to pay 100% attention to the rudders... one small unintentional deflection and you just lost any gains.

Stay still, don't move around.

When tacking be as smooth as possible.

I've been in some real floaters... a few races where I wished I has some incense or even a cigarette (not that I'm a smoker - just something with smoke) just to get a sense of the DRIFTING wind... those are the worst.


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PostPosted: Mon Jun 20, 2011 7:45 am 
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Thanks guys-

Your input is very much appreciated. What I was really getting at was weighing the relative importance of bow-depressed versus windward hull up. Seems the conclusion is that bow-down (to a limit) is more important, while minimizing pitch inertia in waves by keeping the crew weight closer to the fore/aft CG.

One somewhat unconventional method we tried in floater conditions with a bit of success was having my crew trap out on the lee side just in front of the crossbar. Realize this creates quite a bit of roll inertia, but didn't seem to slow us down too much.

BTW, on the waters we sail, no wind is not always synonymous with no waves. On the great lakes, there are sometimes swells leftover from previous wind, and on the smaller lakes, their are always those wonderful powerboat wakes trying to yank the side-stays out of the hulls. In this case the trap tension and roll inertia may not be faster, but its gotta be easier on the boat.

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Sail Michigan's Great Lakes in 2014
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PostPosted: Mon Jun 20, 2011 3:24 pm 
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"Wild Thanging" the boat is the fastest!!! It is also the trickiest. It most likely would not work in 4kts but 6 or more and its on. You still keep the bows down and sterns free. Both crew and skipper on the lee side, no vision of windward telltales, sail it by feel. Get the windward hull up and roll!

You can also use the crew on the wire to help tack the boat in light air quickly. Try it!

I watched a stock Miracle 20 beat Tigers under spin doing the "Wild Thang" several years ago.


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PostPosted: Mon Jun 27, 2011 10:13 am 
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How do you use the crew on the wire to help tack the boat in light air ?


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PostPosted: Mon Jun 27, 2011 11:43 am 
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RobPatt - not sure if your post was directed my way. I don't believe having a crew on the lee wire would be any kind of an asset to tacking. I've only done this a couple of times on upwind legs where my goals were simply to reduce wetted surface on the windward hull and keep the lee bow depressed as much as reasonably possible. Honestly, when we did it initially, it was more to amuse ourselves in a very monotonous race, but it seemed to have some merit.

When its time to come about, it's just like any other time - the crew comes in off the wire and joins me toward the back of the tramp for my best imitation of a roll tack.

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PostPosted: Tue Jun 28, 2011 1:35 pm 
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Think roll tack with crew on the wire during the initial portion of the tack. It is tricky and very fast in light air. You basically pivot on one hull. With a heavy crew just hiking out from the straps may be enough to get it lifted. You must scramble to the other side quickly as you come head to wind.


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PostPosted: Tue Jun 28, 2011 2:43 pm 
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Oh... I get it. My crew could move toward the back of the boat while still on the wire. The boat would then pivot around the lee corner for the tack.

I suspect the biggest challenge would be quickly managing the jib sheets although I'm sure I could do it as I'm used to single-handing the boat.

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'10 F18 Closely Called
Sail Michigan's Great Lakes in 2014
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PostPosted: Mon Aug 01, 2011 7:14 am 
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Sorry to resurrect an old thread - I just saw a video clip on the NAF18 site (under "The F18" and "Tuning Tips"). Mischa Heemskerk very clearly answered the question as well. His view is that it is more important to keep the sterns clear than to try and fly the windward hull.

This answer correlates pretty closely with the advice found here. Thanks guys!

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Sail Michigan's Great Lakes in 2014
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PostPosted: Mon Aug 01, 2011 11:53 am 
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rehmbo wrote:
His view is that it is more important to keep the sterns clear than to try and fly the windward hull.


Why can't you do both? The question "which is more important?" is kind of irrelevant because it's not like you have to chose one over the other.

Getting the sterns clear is related to fore and aft crew placement. Getting the hull to fly is related to windward/leeward crew placement. So there's no reason you have to pick one or the other. The fastest hull trim is to have the windward hull just kissing the water with the bow depressed (down but not doing an endo).

You should move the crew weight around to always try to achieve this hull attitude pretty much regardless of wind/sea conditions. In light air it means having the crew weight forward and to leeward, in higher wind the crew weight will move to windward and aft, but the attitude of the hulls will remain more or less the same for all conditions.

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