deeper forefoot

[mcollins07]

Considering two designs with all else being equal (if that is possible) a monohull with a deeper forefoot will sail closer to the wind?

[Raggi_Thor]

No, that's to simple :-)
On a modern boat most of the lift is from the keel, and the forefoot is not important. On an older design you have to look at the whole boat and keel working together. How close you can sail depends on the total underwater area, the sail area and the wind resistanse from superstrycture and hull above water.

[mcollins07]

I'm want to minimize the keel in a shoal design. Can I want to leverage the use of a forefoot, get by with a little less keel. Increasing the forefoot should increase the total undewater area ( lateral plane). Would not this make a difference if the boat has a small keel?

[MikeJohns]

Originally Posted by mcollins07

Considering two designs with all else being equal (if that is possible) a monohull with a deeper forefoot will sail closer to the wind?

For ocean work a deeper forefoot will give a more comfortable better tracking vessel , this may allow a better pointing ability but the downside is wetted surface area. So depends on all the other design criteria.

The modern racing trend is no virtually no forefoot at all but I woul not recommend that for a cruising hull.

What is the intended use?

[tom28571]

If all else were literally equal, a deep forefoot might generate so much weather helm that the boat would be exceedingly difficult to steer. Would need a lot of rudder angle to restore decent balance with the sail area.

Actually I remember seeing some boats that had very deep forefoots and little other lateral resistance but can't remember where. Might have been in WoodenBoat magazine. Still, I expect it's a poor design direction to go.

[Gregg]

Eventhough this might be out of the "realm" of the current discussion, I had heard if you "gut" the forefoot on larger vessels ie; brigs and maybe some of their cousins, that the little ship will porpoise. I suppose this has more to do with balance of the sail plan, but a large ship can be scaled smaller, and might be something to consider. <---I just ain't smart enough to figure it out.
On a different note, I had a small sailing dingy with rather flat floors with minimal forefoot, and did just fine. Go figure

[FAST FRED]

There are two schools of though about lateral resistance (sliding sideways).

The "racers" use the hull to carry the keel which creates the huge lateral resistance to do combat with other "racers".

The cruisers will use the hull to generate most of the lateral resistance , using as much keel as needed to slow the side slip to 5 deg or so.

The cruiser will have less wetted surface and ghost faster because of it.

Even the racers have to steer off a bit going to windward in heavy going (it takes HP to climb hills) so the ocean tracks will be similar.

FAST FRED

[mcollins07]

I was just reading Bolger's "boats with an open mind." He discusses a "Dart Dinghy" where all the effective lateral plane is near the bow. He also refers to the English Yorkshire coble as his inspiration. I was not able to find any info on this English Yorshire coble via Google. Anyone knowledgable of this boat?

The intended use of my design is a cruiser, however, it is currently a very nonconventional design direction. Perhaps, I'm exploring concepts and design forces more than designing a boat.

[mcollins07]

Are there equations or rules of thumb to estimate how much lateral area or lateral resistance is needed for 5 deg or so of slip for a given sail area?

I've seen some estimations for balance that calculate the geometric center of lateral resistance's longitudinal location neglecting the rudder. Would not a moment about the center of buoyancy be more appropriate?

[DanishBagger]

Damn, this thread is interesting. I get this urge to play with some nice cad-software (I don't own any, so that's out the window).

I'm posting this because I wanted to ask you guys and gals if you could post some pics (or hand-drawn sketches or something). I never thought of this, to be frank.

That Dart Dinghy, I don't understand how that can be done - you have a picture/drawing of it?

[MikeJohns]

Originally Posted by tom28571

If all else were literally equal, a deep forefoot might generate so much weather helm that the boat would be exceedingly difficult to steer. Would need a lot of rudder angle to restore decent balance with the sail area.

Actually I remember seeing some boats that had very deep forefoots and little other lateral resistance but can't remember where. Might have been in WoodenBoat magazine. Still, I expect it's a poor design direction to go.

Tom
That can all be corrected for in the design , the reason for weather helm is simply poor sail balance in relation to the immersed lateral plane not the depth of the forefoot. For a cruising boat a deeper forefoot has many advantages and you would be surprised just how 'handy' and well balanced some very deep forefooted boats are.
The modern trend for a flater fwd section aft of a narrow entry angle is good for fin foiled racers but produces a very unbalanced vessel. A deeper forefoot leading to a fuller underbody with a deep V and a balanced hull are good cruiser attributes. Offshore Cruising boats should be comfortable, good tracking and roomy, the market drives quite a different design they call them cruisers but they are aimed at the coastal daysailing market.

[tom28571]

Originally Posted by MikeJohns

Tom
That can all be corrected for in the design , the reason for weather helm is simply poor sail balance in relation to the immersed lateral plane not the depth of the forefoot. For a cruising boat a deeper forefoot has many advantages and you would be surprised just how 'handy' and well balanced some very deep forefooted boats are.
The modern trend for a flater fwd section aft of a narrow entry angle is good for fin foiled racers but produces a very unbalanced vessel. A deeper forefoot leading to a fuller underbody with a deep V and a balanced hull are good cruiser attributes. Offshore Cruising boats should be comfortable, good tracking and roomy, the market drives quite a different design they call them cruisers but they are aimed at the coastal daysailing market.

Mike,

You misread my post. The key element was that Mcollins said in the original post "all things being equal". Meaning that a "normal" boat that is balanced normally is fitted with a deep forefoot. What I said was that this would upset the balance and create lots of weather helm. True I think.

[MikeJohns]

Sorry Tom , didn't mean to be patronising.
I read it as two similar designs, pretty open interpretation I guess.

[eillew]

Try the following site for info on Yorkshire cobles.

http://www.tradboat2.co.uk/index.html

Colin.

[tom28571]

No problem Mike. I guess it was the coble that caught my attention when it showed up in WoodenBoat.