Sweet Rhode Island Red
That’s something that I have never been able to understand. I have seen many times that a very curvy/springy keel line with long overhang is considered a good thing for pitch polling or pitch control…
For me, for the same overall length, a boat with a flat keel line and “square” bows will be much more resistant to pitch polling.
The pitch angle you have to get to for those overhangs to start to get into the water and generate lift, the straight keel hull will already have a lot of buoyancy forward by much more hull volume in the water.
If you want to avoid pitch polling, you have to attempt to move the center of buoyancy forward as much as possible for the minimum pitch angle.
How are long overhangs better for this end result?Cheers,
Laurent
I think what is happening here is that for a given hull, sloping the stems out will provide some extra resistance to pitch poling. Of course you now have a longer boat. For a given length I think you are right, a flat keel, vertical stemmed high prismatic hull is going to be better at resisting pitch poling.
Personally I usually don’t worry too much about pitch poling but then I don’t usually pile on as much sail as a certain Frenchman I know 😉
Cheers,
Skip
I like to compare rocker to the suspension on a car. A stiff suspension is good when racing around a smooth track at high speed, just like a flat rockerless keel is good at high speeds in flat water.
A deeply rockered hull is more similar to a soft “deep” suspension that can take very big bumps and very uneven roads, but will pitch more with big calm motions.
Cheers,
Johannes
I only added overhangs to make it look more Marshallese! I agree that hull volume under water as far ahead of the mast as possible prevents pitchpoling. Anyone who has sailed a Hobie 16 versus a Tornado or NACRA understands that.
I notice that Gary Dierking’s Te Wa, Tarawa and T2 don’t have the same kind of keel profile as a Marshallese canoe. They have a lot more forefoot and a gently curving keel. Why was that, Gary? Did you ever experiment with a more “kinked” and exaggerated profile?
I think what is happening here is that for a given hull, sloping the stems out will provide some extra resistance to pitch poling. Of course you now have a longer boat. For a given length I think you are right, a flat keel, vertical stemmed high prismatic hull is going to be better at resisting pitch poling.
Personally I usually don’t worry too much about pitch poling but then I don’t usually pile on as much sail as a certain Frenchman I know 😉
Cheers,
Skip
Got it, and agreed.
For a fixed Length of Water Line, long overhangs will be better against pitchpoling
For a fixed Overr All Length, vertical stems with straight keel line will be better against pitchpoling.
It depends on which parameter you consider fixed in your comparison.
A Frenchman with too much sail area? I wonder who that would be… ;o)
BTW, I FINALLY sailed again on my proa the last 2 week ends, after a looooonnnng repair of the daggerboards trunks. Light and fluky winds, but a lot of fun.
Being overpassed by a Nacra F20 (no, I do not go as fast as a Nacra F20, even in my wildest dreams), the skipper turns around and talks to me:
- ... but…. how do you tack???!!!
- I don’t !!!!
You should have seen the look on his face….
It was very light winds and puffy so I could more or less stay in talking (or shouting) distance with him, so I explain to him the shunting process and tell him to wait, I am going to shunt. So I do it in front of him; his answer:
- Cool !!!
When the wind was in around 10 knots, and steady, going upwind on flat water, with the ama just above the water (only one “trace” on the water behind the boat), it was pure bliss.
A big YEEEEEHHHHAAAA !!! followed.
That’a what happen when you spend too much time in Texas, even for a Frenchman…
Unfortunately, more repair to come, during the second day of sailing, I noticed some compression on the extension carbon fiber tube that I added to the foot of my Moth masts to make them standalone in the sockets inside the hull. Just below the connection of the boom on the mast, as expected with the forces of the vang. Time to go back to the beach, and more repair in front of me. AAAAARRRRGHHH !!!
Laurent
I like to compare rocker to the suspension on a car. A stiff suspension is good when racing around a smooth track at high speed, just like a flat rockerless keel is good at high speeds in flat water.
A deeply rockered hull is more similar to a soft “deep” suspension that can take very big bumps and very uneven roads, but will pitch more with big calm motions.
Cheers,
Johannes
I see what you mean, and even if it is not a very “scientific” analysis, it makes perfect sense to me.
Cheers,
Laurent
I only added overhangs to make it look more Marshallese! I agree that hull volume under water as far ahead of the mast as possible prevents pitchpoling. Anyone who has sailed a Hobie 16 versus a Tornado or NACRA understands that.
I notice that Gary Dierking’s Te Wa, Tarawa and T2 don’t have the same kind of keel profile as a Marshallese canoe. They have a lot more forefoot and a gently curving keel. Why was that, Gary? Did you ever experiment with a more “kinked” and exaggerated profile?
Luomen,
NOTHING, absolutey NOTHING wrong with your boat 3D models ! It’s pure proa porn !
But I do have a BIG question : when are you going to build one, and which one ? Most of your models beg to be built… At some point, you have to take the plunge, you know…
Cheers,
Laurent
I notice that Gary Dierking’s Te Wa, Tarawa and T2 don’t have the same kind of keel profile as a Marshallese canoe. They have a lot more forefoot and a gently curving keel. Why was that, Gary? Did you ever experiment with a more “kinked” and exaggerated profile?
I don’t know about the Te Wa, but the T2 and the Tarawa seem, to me, to have pretty similar profiles to a Marshallese canoe. The radii at the intersections are quite large, but there are three distinctly linear sections in both of their keels.
A Frenchman with too much sail area? I wonder who that would be… ;o)
BTW, I FINALLY sailed again on my proa the last 2 week ends, after a looooonnnng repair of the daggerboards trunks. Light and fluky winds, but a lot of fun.
Didn’t say too much sail area, just more than me 😉
Glad you got back on the water, hope to do it myself one day, physical therapy’s a lot like paddling upwind…..constantly.
Cheers,
Skip
Torture test of barge-proa - Youtube
I made this short video to show how a hull with very overhanging ends and deep rocker behaves when thrown into the water. This is a very tough test of the hulls ability to keep the ends out of the water and resisting pitchpooling or just digging the bow down into the water and abruptly stopping the boat.
The barge has a lot of displacement very far out in the ends, which makes it very resistant to these kinds of problems. If the hull had been pointy and without deep rocker and big overhangs it would probably have pierced the surface like a spear and stopped the boat very hard and sudden.
This is a test that any hullshape must pass before I will consider it seaworthy.
Cheers,
Johannes
How did the vee hull with curved rocker do in that test?
My deep-v passed that test, but not as well as my barge.
I don’t want to spam this thread with my boats. I just want to show an example of what we are discussing, and where I get my ideas from. I think rocker is important and often missunderstood, and I find these discussions very interesting. I learn a lot.
Cheers,
Johannes
But I do have a BIG question : when are you going to build one, and which one ? Most of your models beg to be built… At some point, you have to take the plunge, you know…
Aaaah…you had to say it!
I’m in the middle of a somewhat stalled boat building project now. I’m 3 years into a 16’ Wa’apa build. The canoe has been done (and out paddling a few times!) for a year and a half, then I have been toying with different rigs, rudder options and the like.
The good news is I’m close. Halyards and stuff just came in the mail. My CLC lug sail is about to get laced on. Like I said, close. But the closer I get the more stuff “appears” on my list.
I’ve attached a pic of the parts I had CNCed (rudders, GIS style rudder case, leeboard, mast step, hiking seats, miscelaneous chocks etc.). All this experience is going to make my next boat go faster.
So here’s the question:
HBBC: I love everything about this daysailer except the rig. I don’t want furlers, but I don’t want to drop jibs each time I shunt. An isocelese pizzeyish sail is an option, but now the mast tilts. I love the idea of having a simple, non tilting rig.
Scampi: This is my best looking design, and the most able cruiser. I love the idea of a schooner rig. I also like the beach cat rig. But it feels complicated. And I feel like Scampi, with an interior of sorts on a 24’ LOA is 5 pounds of sugar in a 3 pound bag. Michael is right—she should be 4-8 feet longer.
SRIR: I LOVE the idea of not dealing with rudders most of the time. And Hugo’s experience with the boomless Gibbons/Dierking rig seems promising—especially reefing without mast tracks or furlers. Now I’ve added my “steering paddles” and I feel complication sneaking back into the design. Plus, seems like (almost) everyone says get the rudders in the hull. That said, having no rudders most of the time seems glorious.
And the final factor is that designing proas, and trying out different ideas is my stress relief. I love to fire up the laptop and bang out some new ideas. I’m worried I’ll have a better idea while I’m building my next canoe.
Thanks to everyone who has been enjoying my renderings.
And yes…I do need to get started…soon.
here’s the pic.
Oh, and Johannes—don’t worry about spamming my threads! I’m glad to see the discussion develop.
Being overpassed by a Nacra F20 (no, I do not go as fast as a Nacra F20, even in my wildest dreams)
How much sail area does your moth schooner put up Laurent? Are there other reasons you couldn’t catch an F20?
They are fast—I crewed on a friend’s. But what’s keeping your boat from going that fast?
I notice that Gary Dierking’s Te Wa, Tarawa and T2 don’t have the same kind of keel profile as a Marshallese canoe. They have a lot more forefoot and a gently curving keel. Why was that, Gary? Did you ever experiment with a more “kinked” and exaggerated profile?
Those designs are based more on Kiribati canoes than Marshallese. Kiribati is right next door to the Marshalls and both types are fast. I chose the smooth curved keel of Kiribati mainly because it is slightly easier to strip plank. The “corners” on the Marshallese keels cause a little unfairness to the shape that may or may not be important.