Race to Alaska Boat Design

Well a submersible sailor is a bad idea, unless the image in my brain is way off. lets not be harsh though CT249, lets change the thought process with (my layman's brain of) scienceishness. Strictly due to the viscosity difference between air and water, if drag is kept at a minimum above and below water. more of the structure will inherently want to be above water to the point of vanishing returns. the least amount of surface area dragging through the water the better...
However that does not mean a torpedo with a sail above water won't beat a barge with a bed sheet attached to a telephone pole. But it does mean if you design above and below the water for optimum drag, you will find air to be the winner.

 

Here are my ideas of what would make a good R2AK boat:

R2AK BOAT DESIGN REQUIREMENTS

1.) It must sail very well, especially upwind and down wind. It should be able to reach double digits in knots in a good wind.

2.) It must row or use some other form of human muscle power almost as well as it sails. It should be able to maintain mid single digits (4 to 6) in knots while under muscle power alone, at least in short bursts of two hours or less.

3.) It must provide adequate shelter for its crew, especially while they are off watch, allowing them to lay down in complete shelter.

4.) It must be able to carry at least 100 lbs of provisions per crew member, as well as very good anchors and other ground tackle, and adequate repair supplies.

5.) it must be seaworthy enough to deal with at least three foot high breaking waves.

6.) Its sail plan must be very easy to reef or otherwise de-power in sudden gusts and longer squalls.

7.) It must be very difficult to capsize, or easy to self rescue, preferably both.

8.) It must have reasonably good course keeping capability, without the aid of an autopilot or a steering wind vane. It should be able to hold its course, relative to the wind for at least one half minute, without anyone at the helm.

DESIGN SUGESTIONS

9.) It should be a trimaran with low buoyancy floats, for the following reasons:
a.) to keep a very narrow WL for the main Hull. This along with a rounded section shape will net the least whetted area per Length, in keeping with requirement 2.)
b.) to have a very high initial stability, in keeping with requirements 1.) and 7.).
c.) the low buoyancy floats can be kept far from the main Hull, to allow space for oars in between, also in keeping with requirement 2.)

10.) Its main Hull Length should be as follows: (5 ft per crew - 1) + 15 ft.
a.) This will provide a decent displacement at a low DL ratio, which will allow faster sailing speeds, in keeping with requirement 1.). A one crew boat, for example, be 15 ft long and have a likely D/L of 100 or less, with an all-up displacement of up to 746 lbs, in keeping with requirements 1.), 2.) and 4.). A heavier boat carries better between oar strokes; a lighter one rows faster. But a very long boat can be a handful for just one crew, especially in rapidly changing conditions.
b.) with two crew, the boat can be 20 ft long, more or less. This allows for an even lower D/L with still more than adequate carrying capacity. The longer boat can be wider too, having more space between its floats for longer oars. The greater Length allows for nearly the same rowing speed but for a heavier boat. The crew can row in watches of 2 hours or less, maintaining a steady pace of around 4 kts in calm conditions.
c.) With 3 crew the boat can be 25 ft long, which is probably nearing the limit for just one rower at a time. Its rowing speed may still equal the shorter boats, though being 2 to 3 times as heavy. This is because now the rowing watches can be one hour on, two hours off.
D.) With 4 crew, the boat can be 30 ft long, but now it should have two rowers on duty, for two 2 hour watches.

The reality is that the longer boats are likely to sail faster, while rowing slightly slower than the shorter ones. Longer boats must be stronger boats, with the weight of the boat, per given construction material and method, being a higher proportion of the over-all displacement. For sailing speed, this is not a problem. But for rowing speed, it certainly is.

A 3 to 4 crew boat is probably best. A 1 crew boat has next to no chance of winning, but its skipper will be entitled to a life time worth of bragging rights, if he/she manages to complete the course.

11.) Beam, over-all should probably be around 3/4 Length, especially for the shorter 1 and 2 crew boats. The longer 3 and 4 crew boats could have slightly lower B/L ratios, down to say 2/3 Length. This is because the height of the base of the sailing rig can be proportionately lower on the longer boats.

12.) The sailing rig should probably be a low AR, 3/4 sloop, with perhaps a head stick on the main, if the main is not a square top. The weight of the head-stick will help insure the main will come down reasonably quickly, once the halyard is released. Since a good setting jib puts proportionately much greater strain on the rig, its size should be kept modest. A huge down-wind sail can always be set from the masthead. The low AR does compromise windward performance, but allows a shorter mast, and a given SA to be carried in stronger winds, in keeping with requirements 2.) and 7.). The fractional rig allows the boat to sail under main only, so striking the jib could be the first reduction of SA, in keeping with requirement 6.)

13.) The SA should provide an S/D of 20 or higher, though one in the mid-teens might be worth trying. This is because the smaller one can have a shorter mast and less air-drag while rowing. But the real speed comes from sailing, and a larger SD allows faster boat speeds in lower wind speeds. So boats with S/D’s even in the 30’s are more likely to win, unless dead calms rule the race.

14.) The ‘Board should be a fore and aft swinging one, set outside the main Hull so:
a.) it can kick up, if it hits an obstacle,
b.) it doesn’t intrude in the off-watch space, and
c.) it allows some adjustment of the Center of Lateral Area (CLA) So the boat will balance better under a wider range of SA’s, in keeping with requirement 8.).

15.) The rudder should be transom mounted and have a blade that can swing aft, if it hits an obstacle. The rudder stock should be strong enough to handle steering this rudder in its kicked up position.

16.) The off-watch space, or cabin, should offer protection from wind, rain, spray, and cold. It should probably be insulated, have decent ventilation, and have sitting headroom, in keeping with requirement 3.).

17.) the Bow of the main Hull should be high and sharp, with a pitched deck capping it. This deck should have a hatch for fore deck work, in keeping with requirement 5.). The height of this pitched deck should probably be about 1/7 the Length of the main Hull, especially on a 1 or 2 crew boat. With the bigger boats, less may be adequate, maybe down to 1/8 or even 1/9 the Hull length.

18.) It may be a good idea to have a permanent awning over the cockpit, with a strategically located hatch. This will keep the worst of the rain off the on watch crew and provide the bases of a very quickly set up cockpit tent, so the entire crew can be housed when the boat is not underway. This awning can provide space for some solar cells.

 

Just for information. At least two of the likely race winners (ie boats that will finish in the top 6) can pedal at 4 knots all day. One person. That is faster than most sail and oar boats can row. We were surprised last year leaving Victoria how many boats we overtook, despite pedalling a 35ft catamaran and being last to leave.

Note: The only "handicapping" in the race is that the first to Victoria are the last to leave, just because the first boats in get the berths nearest the gangway, the later boats dock further out. The race is a Le Mans start, all racers start in front of the Empress hotel and run down stairs to the docks and then to the boats. watching the three guys in wheels chairs go down stone steps at speed was impressive! (They lashed themselves to their chairs). So we had oars not for powering but because it made us 40ft wide so hard for other boats to overtake. As you cna see in my videos from both Victira starts

So you will be uncompetitive, meaning not finishing in the top 10 unless you can human power at at least 3 knots, sail at 12 knots to windward and at high teens or more offwind - as the top 10 multihulls can do

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Quote:
"If you can out-think everyone in the world in an activity in which you only have "some experience" then your brains are being wasted looking at sailing boats when you could be bringing fusion power and universal peace to the world."

I'm working on both of those too!!
Patience, patience, man-o-man.

 

Sharpii2,

Thank you, you've put some thought toward this.

 

Eric,

Vermont is a long way from here...

 

So if the "sail" was a large kite with 15 - 25% vertical lift on the small, semi-submersible, wave-piercing, low-profile hull, you'd feel more comfortable?
It has a planing hull aft that dove-tails clear of the water when in rowing mode.
Crazy, right? I prototyped it last summer and it worked great.
I was able to developed a steering system that eliminates the rudder using aft barber-haulers.

 

It would be great to see the prototype.

 

I prototyped the ideas , I'm building the prototype now.
I appreciate your enthusiasm though upchurch.

 

I see.

Just how big is Bad Kitty? She looks to be around 30 ft or more in length. If so, it is quite surprising how effective the propeller was. The neatest thing about it is that its hub was above the waterline, so the blade was easier to manufacture. The pedals seem to be hooked up directly to the drive shaft. Pretty ingenious.

I suppose the main reason a pedal drive is better than oars is that with the pedal drive you get more or less constant power. This way the boat doesn't get a chance to lose momentum between "strokes". In the video you provided, the superiority of pedal over oars is plain to see.

I have for a long time understood that really light boats don't necessarily row faster than heavier ones. Years ago, among the pdracer crowd, I challenged someone to do an experiment. I asked them to try rowing a light pdracer, then rowing again with 100 lbs of "cargo". One person accepted my challenge. He had an unusually light pdracer, one that weighed around 60 lbs. He rowed it light, with his 160 lbs aboard for about a mile. Then he brought about 100 lbs of water on board and rowed it again. The heavier load actually increased his speed by about a quarter of a knot. Since the boat usually rows at around 2.5 knots, this was a significant improvement. He loaded another 100 lbs on board, and the boat rowed even faster, just as I predicted. He was quite amazed.

It seems like the added weight increased the boat's momentum between strokes, acting kind of like a flywheel on a piston engine.

With a pedal system, either driving a propeller or counter moving yullow like foils, the propulsion system is more like a turbine engine, which needs no flywheel.

Thanks for showing us this.

 

It's funny how that works sometimes.
I remember as a kid tearing around in a little 40HP outboard... a lot.
It was noticeably faster ( no GPS in those days ) with two people.
I figured it had to do with planing angles or, as PAR may prefer, "angles of plane".
However, a well designed boat is fastest if kept light.
It simply needs to be designed for that weight and balance.
To make the general assumption that heavier boats are faster, or even as fast, I believe to be a mistake.

 

Bad Kitty is a 35ft catamaran, as I said in a previous post. Lighter boats/planes/cars/people tend to be faster than heavier ones

RW

 

I couldn't agree more. Most of the time this is true. But there are other times, the vast minority, where it is not true. I know this from my personal experience. The light sailboat I once had, had terrible trouble sailing into a head sea. It would often slam to a standstill on each third wave. We don't see very many cruising size multis on the great lakes. I often wonder just how much the local wave conditions have to do with this.

I remember predicting that a lighter pdracer would be faster if it had propeller drive, when I predicted the heavier one would be faster under oars. This is because the oar driven one got its propulsion through pulses, with considerable lad between. The one with a propeller would have a more steady force applied to it. The same reasoning works in reverse in the case of a chop. In this case there is presumably a steady motivating force, the sails, but a pulse like resistance, due to the waves in the chop. In this case, I would expect the lighter boat to need a larger sail plan in proportion to its weight than the heavier boat. The boat I had, had a generous working sail rig of 145 sf for an 800 lb boat, so getting to windward in a chop was never really in doubt. But it was often very rough and jerky.

I believe a narrower hull, of the same Length and displacement, would have been more comfortable and would have been able to get to windward with a more modest sail plan. A multihull, if it's able to keep its connecting structure out of the waves, is really a rather narrow hull for its length, chopped up lengthwise into to two or three even narrower hulls. This is because the hulls themselves don't need to have any form stability. But I wonder that if, in the case of windless choppy conditions, the heaver boat, for its length just might have an advantage.

In still-water, windless conditions I know that longer and lighter will always have the advantage.

Just how heavy is this 35 footer? What's its displacement?

 

For those not familiar with the misbehaved feline, Bad Kitty is a legendary boat in the Pacific Northwest. She's basically an overgrown beach cat. Her owner has no reservations at all to taking a sawzall to her and rebuild her at will. Her accommodations can only be described as "coffin-like." I don't know how many Van Isle 360s she's done, not to mention uncounted other races up and down the coast. The R2AK and Bad Kitty were made for each other.

 

The reason why this is so effective is that the relationship of speed to hull resistance is non-linear especially approaching "hull speed".
The average resistance of a boat at say 3 knots is much less than one varying from 1 to 5 knots.
The heavier boat does have greater resistance than a light one at the same speed but this is more than offset by keeping the heavier boat from getting into the much higher resistance area.

I agree about the pulsing resistance of the waves and would add to it that the rig on the lighter boat will be pitching more and will be less efficient.