Sweet Rhode Island Red
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?
One Moth rig is 8 sq meters; so 16 sq meters total.
Why I don’t go as fast? Hmmm…. Where do I start?
- Because one is designed by a profesionnal boat designer/naval architect with load of experience, data, and potentially even simulation (CFD???) available to him, and the other is an amateur who looks at a hull shape drawing and thinks: “Hmmm, that looks about right… Let’s build it !!! “
- weight: my boat is in some areas overbuilt and too heavy: 6mm thick bold cypress strip planking with a bunch of bulkheads (too many I believe), and amateur handlaid fiberglass and a few bits of carbon fiber with (too much) epoxy vs. foam core, with vacuum bagging carbon fiber
- sail area; I did not check the data, but I suspect that the sail area vs. displacement ratio of a Nacra F20 is much higher than my boat… Even if I start lifting the ama at 10 to 12 knots of true wind speed
- when I sailed with the F20, it was not the type of wind strength where you need to trapeze, but in more wind, I am sure that it would make a difference; I don’t trapeze, I am just too afraid of breaking my rigs if I do something wrong; they were never designed for trapezing in the first place
- last but not least, skill level of the skipper!!! I sailed for a long time (simply because I am getting old…) but I have never sailed competitively on a beach cat, for instance.
I have not weigthed my boat lately, but from the top of my head:
- ama 40 lbs
- beams (together) : 40 lbs
- main hull: that’s the tricky part; I made a lot of modifications; I would guess 150 lbs
- daggerboards (together): 30 lbs
- rudders, with aluminum Prindle rudder heads, and tiller extensions: 30 lbs
- rigs: (masts, booms - which weight close to nothing, sails) 40 lbs
TOTAL without crew: 330 lbs or 150 kgs…
I do need to weight it properly, though…
Cheers,
Laurent
You have inspired me!
- weight: my boat is in some areas overbuilt and too heavy: 6mm thick bold cypress strip planking with a bunch of bulkheads (too many I believe), and amateur handlaid fiberglass and a few bits of carbon fiber with (too much) epoxy vs. foam core, with vacuum bagging carbon fiber
- sail area; I did not check the data, but I suspect that the sail area vs. displacement ratio of a Nacra F20 is much higher than my boat… Even if I start lifting the ama at 10 to 12 knots of true wind speed
I hear you, Laurent. Especially about the difference between proper engineering and the “yeah that looks right” method.
The Nacra 20 has 24 sqm of sail—50% more than your boat. But the weight is probably pretty similar at 390lbs—the carbon version only skims 15lbs off of that.
You have inspired me!
I appreciate the credit, but its John Pizzey’s invention. And a clever one at that.
Are you going to put a tiller on the outboard side? Is your canoe a tacker?
Here’s the cutaway forefoot brought to its logical conclusion—inspired by Hugo’s lee-keel on Proud Mary.
What if we build a rocker less, 3 sided canoe—like KBBC. But asymmetric, with a straight keel. The lee panel extends below the floor and describes the profile. And then the volume to windward, that’s missing on Proud Mary, is filled in with CNCed foam?
That’s what this version is.
Chris,
Why bother with the hull fillet, just extend the keel sole foil section straight up and add a chine runner to the flat leeward side of it? Maybe even the keel sole section mirrored?
Love your renderings by the way. Well done.
Rob
Reminds me of Munroe’s first proa, but asymmetric.
He changed it to two boards in is next one, but I think it was to compensate for the fixed mast rig.
Chris,
Why bother with the hull fillet, just extend the keel sole foil section straight up and add a chine runner to the flat leeward side of it? Maybe even the keel sole section mirrored?
Love your renderings by the way. Well done.
Rob
The fillet would reduce the amount of interference drag between the main body of the hull and the fin section. Granted I think that particular fillet is excessively large, but a fillet is a very worthwhile feature to incorporate.
Here’s the cutaway forefoot brought to its logical conclusion—inspired by Hugo’s lee-keel on Proud Mary.
N. Herreshoff came to the same logical conclusion; he actually invented the idea of the fin/bulb keel and balanced spade rudder while sailing on Gloriana not long after it was launched. He built a small-ish Sloop with that layout in 1891 (1891!) to test out the idea, it was named “Dilemma” for anyone interested.
What if we build a rocker less, 3 sided canoe—like KBBC. But asymmetric, with a straight keel. The lee panel extends below the floor and describes the profile. And then the volume to windward, that’s missing on Proud Mary, is filled in with CNCed foam?
That’s what this version is.
I’m not sure what benefit there would be in asymmetry. The keel is so shallow for most of the lwl that I can’t imagine you’d get any lift from it, just higher induced drag. The asymmetry in a full keel proa hull is like a very low aspect ratio wing, the lift to drag ratio isn’t great but it works ok, your proposed hull has basically no aspect ratio so the efficiency would be even worse. If you’re going for the logical conclusion, I think Paul Bieker has it nailed with his proposed Jester-Class boat: A round or multi-chine symmetric vaka and a daggerboard for lift.
I’m not sure what benefit there would be in asymmetry. The keel is so shallow for most of the lwl that I can’t imagine you’d get any lift from it, just higher induced drag. The asymmetry in a full keel proa hull is like a very low aspect ratio wing, the lift to drag ratio isn’t great but it works ok, your proposed hull has basically no aspect ratio so the efficiency would be even worse
I see what you mean. But there are lots of low aspect keels that work pretty well. Never as well as high aspect foils, for sure. SRIR is a meditation on a rugged, simple (for a proa) boat for knocking around on; more of a jeep than a lotus. The question for me is when you optimize each (jeep and lotus), how far apart is the performance, durability, cost and complexity. And character!
I think that through that lens, the “logical conclusion” forefoot is probably not a great boat for beaching, and it might make the wrong compromises from a hydro perspective. What’s interesting is that we have charted a little piece of design space. There might be other stuff there if you poke around.
If you’re going for the logical conclusion, I think Paul Bieker has it nailed with his proposed Jester-Class boat: A round or multi-chine symmetric vaka and a daggerboard for lift.
Amen, Brother. What a thrill to sail one of those babies! The rig, the hull volumes, the foil system; its the best we’ve got. I’m sold!
But I guess what I’m wondering about is if a simpler boat is possible—especially at a smaller size. I’m thinking 20-24”
Thanks for your thoughtful posts, Greg.
Chris
Are you going to put a tiller on the outboard side?
When you wrote the above I had no idea, but today I figured some stuff out and also discovered some neat features of the rudder. I’ve started a thread.
Is your canoe a tacker?
It’s basically a mini wa’apa, two part canoe, made from two sheets of plywood. I’ve linked to my website on my thread. It’s both a tacker and shunter, I built it as a compromise because I couldn’t decide on my ultimate proa design (sound familiar?). Experimenting with this boat should help lead to that goal.
-Thomas
I like your idea so much, Thomas, that I stole it.
I thought I had an idea for a clever build on it, but it ended up being less elegant. This is a really nice set up.
I like your idea so much, Thomas, that I stole it.
Do you think those tillers are long enough? They look awfully low and short, and not particularly comfortable to use. I get that you’re constrained by wanting the rudders to fit fore/aft of the iakos and not wanting the end of the tiller protruding past the leeward gunwale. And I understand why, aesthetically, you might want to do so, but I think you should consider the ergonomics as well.
That’s what tiller extensions are for…
I like your idea so much, Thomas, that I stole it.
You WHAT!
Be very careful about the geometry, it has to be just right or else there is way too much friction. I haven’t really bothered trying to understand this (yet), but by moving mine in about 50mm towards the hull it completely stopped working.
Could you do a quick post somewhere on how you do your models? I have a working knowledge of Solidworks, but not sure what approach to take.
In reply to old greg, I will be using mine with a tiller extension. Much prefer to sail with one.
Do you think those tillers are long enough? They look awfully low and short, and not particularly comfortable to use
I don’t know. The tillers are more than a couple feet long—perpendicular to the rudder shaft. They might want to be longer. If I don’t care about them interfering with the deck they can get longer and taller—but then they’ll hit the deck when they kick up. They can get longer with out interfering by moving the rudder pivot back.
The interesting question is how far back should the rudder be?