Windward Performance: Various Shoal Drafts - SailNet Community
 
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post #1 of 10 Old 09-06-2011 Thread Starter
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Windward Performance: Various Shoal Drafts

The advantages of the various shoal drafts are obvious, but I'm wondering about which provides the best/worst performance sailing to weather: fixed fin 4.5ft shoal versus 3'10"/7'6" centerboard versus 3'10" wing keel.

Centerboard provides the deepest draft, but does it sacrifice performance compared to the fixed fin shoal due to less surface area?

Thanks,

GRR
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post #2 of 10 Old 09-06-2011
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You can compare the racing ratings of various models here PHRF New England - Handicapping - Base Handicaps

Centerboard models are indicated as CB, shallow draft SD, and wing keels as WK.. If a model only came in one configuration, such as a wing keel standard, then that indication may be omitted.


They are a variety of boats that have all options rated...

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post #3 of 10 Old 09-06-2011 Thread Starter
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PHRF the whole story?

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Originally Posted by sailingfool View Post
You can compare the racing ratings of various models here PHRF New England - Handicapping - Base Handicaps

Centerboard models are indicated as CB, shallow draft SD, and wing keels as WK.. If a model only came in one configuration, such as a wing keel standard, then that indication may be omitted.


They are a variety of boats that have all options rated...
Does the PHRF tell the whole story about these different keel configurations with regard to windward performance? It seems like it covers speed. I'm also wondering about pointing ability and tracking for cruising purposes. It seems the WK would be most likely to slide to leeward, but what about shoal draft versus centerboard? No major difference?

Thanks,

GRR
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post #4 of 10 Old 09-06-2011
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Originally Posted by Grand River Raider View Post
Does the PHRF tell the whole story about these different keel configurations with regard to windward performance? ...
I'd say it largely does, with a couple of caveats.

The ratings measure for a CB overstates windward performance, as the configuration gets a plus for off wind performance where the raised keel provides a performance improvement...the single ratings measure is a blend of the two.

Secondly it is my experience that the credit given to slower boats for configurations like SD and WK and CB is never enough for how the boats actually perform...ie.e the credits are too conservative. And the proof of that pudding is that serious racers in my experience usually have the taller masts and deeper keel options...

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Last edited by sailingfool; 09-06-2011 at 11:18 AM.
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post #5 of 10 Old 09-06-2011
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Hey,

As far as I know, for going to weather, nothing beats draft. A centerboard should outperform a shoal draft regardless of wings or not.

Barry

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post #6 of 10 Old 09-06-2011
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The PHRFs for the Pearson 28 probably answer your question deep vs shoal keels. The first models (1975 into 1976) had a draft of five feet. The keel was then modified to create a draft of four feet six inches. The hull dimensions remained unchanged, as did displacement and ballast. Six inches of depth reduced the PHRF from 195 to 192.
As to the CB question, it would depend greatly on the size and configuration of the CB. It seems possible that a K/CB design could go to the wind as well as a deep fin and could perform better off the wind.
Like Sailingfool said, look at the fastest boats and there you find the fastest configurations.
For cruising many other factors will influence the keel design whereas racing dictates a deep fin with bulb ballast.
John

Hold it, I just reread this and it seems that reduced draft increasred its performance to a lower PHRF. Does that make sense?

Last edited by ccriders; 09-06-2011 at 11:53 AM. Reason: I confused myself
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Hey,

As far as I know, for going to weather, nothing beats draft. A centerboard should outperform a shoal draft regardless of wings or not.

Barry
Yes, this is what I was thinking as well. But then I got to wondering about the surface area on a CB versus a shoal draft fin, in that some of the centerboards seem to have narrower lateral surface area than the shoal drafts and I wondered how this impacted sliding to leeward.
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Quote:
Originally Posted by ccriders View Post
The PHRFs for the Pearson 28 probably answer your question deep vs shoal keels. The first models (1975 into 1976) had a draft of five feet. The keel was then modified to create a draft of four feet six inches. The hull dimensions remained unchanged, as did displacement and ballast. Six inches of depth reduced the PHRF from 195 to 192.
As to the CB question, it would depend greatly on the size and configuration of the CB. It seems possible that a K/CB design could go to the wind as well as a deep fin and could perform better off the wind.
Like Sailingfool said, look at the fastest boats and there you find the fastest configurations.
For cruising many other factors will influence the keel design whereas racing dictates a deep fin with bulb ballast.
John

Hold it, I just reread this and it seems that reduced draft increasred its performance to a lower PHRF. Does that make sense?
Yes, and it was those factors for cruising that I was considering while also searching for the best windward characteristics possible in a more shallow draft boat. As someone else pointed out to me in another thread, I may wish to make good time/distance on extended cruises while using the Iron Genny sparingly, so this led me to thinking about the best possible compromise. If I purely were searching for speed to weather, I would simply get a deep fin keel.

No, that change in PHRF doesn't make sense as I understand it. I would think that it would be the opposite.
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[QUOTE=sailingfool;770573]I'd say it largely does, with a couple of caveats.

The ratings measure for a CB overstates windward performance, as the configuration gets a plus for off wind performance where the raised keel provides a performance improvement...the single ratings measure is a blend of the two.

QUOTE]

CCRiders,

Unless this blend of the two mentioned by sailingfool explains the decrease in PHRF as maybe it got more pluses for off wind performance that outweighed its negatives for winward performance, but this seems a stretch.

GRR
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Quote:
Originally Posted by Grand River Raider View Post
Yes, this is what I was thinking as well. But then I got to wondering about the surface area on a CB versus a shoal draft fin, in that some of the centerboards seem to have narrower lateral surface area than the shoal drafts and I wondered how this impacted sliding to leeward.
It is the lift from the keel/centerboard that reduces leeway, not the amount of surface area. A 2ft wide foil will outperform a 4ft wide sheet of plywood every day of the week.
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