Simple sail question

[charlief1]

I've been working on a simple ply composite built "kayak" and I'm wanting to put a sail on it for crossing lakes a little easier. I already figured out where and how the daggerboards (yes 2 and I don't want leeboards) will go but I've been stumped when it comes to the location of the mast. Is there a percentage of the length where the mast should be mounted? Say divide the length into thirds and the mast should be mounted at a line 1/3 back from the front?

No, this isn't a typical kayak and has a width of 45" and an OAL of13.4', The model I made are the pics so you can get an idea of what it will end up looking like. the height will end up being about 14" and draft looks like it will be less than 5" with me and gear in it. The mast won't be big and the sail won't be either since this isn't a dedicated sailboat but an alternative to paddling when I want to go across some of the lakes where I live and not have to paddle that much.

 

[PAR]

How is it you know where the daggers will go, without knowing where the mast will live?

 

[charlief1]

By looking at other boats I figured out that the daggers will be at the front of the open area. One on each side at the front. The issue I have is figuring out how much further in front the mast needs to go. That I haven't found a good pic of to figure it out. I've always been able to look at things and figure out spacing of things that I build, but I haven't found a good pic that looks right to me as far as mast placement, that's why I'm asking.

 

[gggGuest]

To a large extent its the relationship between sail and foil that is important, and the two items in the same relationship can go further forward or aft. A very crude way of getting them in the right sort of relationship is to draw a side on profile and have the middle of the sail area over the middle of the daggerboard area. Its not very critical in a small boat though, in spite of popular opinion.

However, a thought. Traditionally in the US sailing canoes had two masts, one very near the bow and one very near the stern. Its not an especially efficient arrangement, especially for sailing against the wind, but its good for sailing across the wind and it keeps the sails clear of the sailor so you can paddle and sail if you want. It also means that the exact placement of the masts isn't at all critical because you can juggle the relative sizes of the sails to have the same effect if you want to.

Have a browse round the pages below and you'll see some of the old stuff. Remember though that the full on racers with their sliding seats had and have way more sail and complexity than you'll ever need, its the well backed off cruising boats you might look at for a model.

http://www.intcanoe.org/iclife/history.html

 

[gonzo]

14" is really high sided for a kayak. Usually 7-9" would be about right. Also, kayaks are long and narrow. A beamy hull is hard to paddle. For example:http://watercraft.clearstreamwood.com/products/kayaks/skin-on-frames/

 

[PAR]

A good general guide will be to place the leading edge of the daggers just a hair forward (a few inches) of the sail's CE, regardless of its position in the boat (mast location). This means drawing up a profile of the hull getting an idea of it's lateral area and using general and typical proportions, placing the mast and daggers as described. If you design an odd arrangement, you'll have to do some math, but if you stick to conventional arrangements, you'll be close enough, as you can "butt trim" underway.

This would be typical and I recommend you log onto: (> http://www.storerboatplans.com/Canoebits/KayakRig.html <) and have a look.

 

[gonzo]

If you google "sailing canoes" and choose images, there are hundreds of thousands of examples.

 

[charlief1]

14" is really high sided for a kayak. Usually 7-9" would be about right. Also, kayaks are long and narrow. A beamy hull is hard to paddle. For example:http://watercraft.clearstreamwood.com/products/kayaks/skin-on-frames/

Not all of them are narrow and the expansion of what's called a kayak is why I call it one. My description is a canyak. A boat that's got a top on it and will be paddled sitting in a high position. 40" wide is also not that uncommon these days. One of the "decked sailing canoes" that was on the page gggGuest was nice enough to provide had 1 that was 54" wide and 17' long. It was in the design to be paddled as well as sailing, so it's not as wide as you might think. The base is 32" at the widest with the sides sloping (sp) up at a shallow angle so I could add a straight side for the extra height. While it looks ungainly, I've been using a kayak paddle to propel a bass buster around and it's not that bad. It does take some practice but at 48" wide it works decently for ponds and back waters. The point of the canyak is to make something that's a little easier to go in some of the back areas and let me get on the main lake without being swamped. Texas has some serious wind and it can drive any boat sideways when it's up, so this will have a profile that will work for what I want.

To a large extent its the relationship between sail and foil that is important, and the two items in the same relationship can go further forward or aft. A very crude way of getting them in the right sort of relationship is to draw a side on profile and have the middle of the sail area over the middle of the daggerboard area. Its not very critical in a small boat though, in spite of popular opinion.

However, a thought. Traditionally in the US sailing canoes had two masts, one very near the bow and one very near the stern. Its not an especially efficient arrangement, especially for sailing against the wind, but its good for sailing across the wind and it keeps the sails clear of the sailor so you can paddle and sail if you want. It also means that the exact placement of the masts isn't at all critical because you can juggle the relative sizes of the sails to have the same effect if you want to.

Have a browse round the pages below and you'll see some of the old stuff. Remember though that the full on racers with their sliding seats had and have way more sail and complexity than you'll ever need, its the well backed off cruising boats you might look at for a model.

http://www.intcanoe.org/iclife/history.html

That link was exactly what I'd been missing, thanks! From the pics and descriptions of the boats I picked the right place for the daggerboards and it gives me 2 different spots for the mast. Since I'm not looking for a racer this gives me more than enough ideas since the mast is 10' total length. Somewhere between 30 and 60 SqFt will give it more than enough sail to make her move decently without trying to compete with a power boat.

 

[messabout]

Two dagger boards??? Why two. That is un necessary complication. In fact it may work better with only one board.

 

[PAR]

Agreed (two daggers) and (again) guessing on the mast/dagger placement based on other designs means an ill balanced boat. You'll have some butt adjustment available, but if you're off by much, it'll sail, but not well, particularly to windward, so why guess.

 

[charlief1]

Agreed (two daggers) and (again) guessing on the mast/dagger placement based on other designs means an ill balanced boat. You'll have some butt adjustment available, but if you're off by much, it'll sail, but not well, particularly to windward, so why guess.

It's a shallow draft boat and by running 2 dagger boards I can keep the draft as shallow as possible. Think of it like running 2 leeboards. I just don't want to mess with leeboards and the 2 holes are for an additional idea that I'm still working on. The sail is going to be like the old sufish sailboat so the daggerboards will be in the center of the sail, and since it looks like the sail will be in a position 5.25' from the nose, it should be fairly balanced. This canyak should do what I want and I know it's unconventional, but just about all the projects I've done are unconventional.

I've had quite a few people point out some of the flaws in the design, but as I've gone over older boats this should work really well for what I've got planned.

 

[PAR]

Any retractable appendage by it's nature is shoal, if used properly. The additional weight of an extra case and it's board seems silly in a small boat, that's not very performance oriented. The case can be offset to clear the mast, with no concerns about efficiency. The same is true of the mast, which can be along side the case if necessary. On a lanteen rig, the case wouldn't anywhere near the mast anyway, so the point is moot.

As you can see the case isn't even close to the mast's location on a lanteen rig. Again, I'll ask, how is it you know where the case(s) will live without a clue about the CE or CLP? Given how relatively simple it is to place a set of appendages on a boat like yours, why guess. Place the leading edge of the dagger, a few inches forward of the CE and for this boat, you'll want a fairly modest lead, say in the 14 - 15% range for good balance. The balance aspect can be butt adjusted, but it's nice to get it close enough, so you're in a comfortable position to get to weather.

 

[gggGuest]

Its not a solution I'd adopt, but I can see that a daggerboard case each side of the hull, built into/flush with the sidetanks, would make for an awful lot more room in the cockpit than a conventional design. It would be an interesting thing to try. I'd probably only make one board initially and see how swapping it from side to side worked. Get a better result with one board with a nice foil shape than two boards that were more plank like. Short tacking you could probably get away with leaving it on one side.

The thing is the purpose of the boat. If its primarily a sailing canoe this isn't the way to go, but the OP makes me think this is planned more as a sail assisted paddling boat. Plenty of motor sailor boats round the world have a rudimentary upwind sailing capability but satisfy the owner's needs, doesn't seem impossible same could be true of a paddling boat.

Conventionally with leeboards, BTW, one is lifted up. I personally think they are a ghastly solution, poor hydrodynamically, structurally and aesthetically, and this idea does seem interesting. Hard to be worse!

I would very seriously consider the traditional two mast setup. Another option that might be worth looking at is that a number of turn of the century canoe rigs had full length battens in the sail something like a chinese junk rig. That would be nice and easy to reef down. It could be that with some careful planning you could end up with a pair of free standing sail mast combinations with which the rigs could be removed, sails rolled round the spars, and the whole lot stowed on the foredeck. Err on the large side with the aft sail and you can just tune balance by making it smaller. Even just roll a bit up at the bottom.

You've got to allow for the possibility that something this radical could be a complete and utter flop of course, but if the materials aren't too expensive and you enjoy the construction for its own sake, well...

 

[waynemarlow]

Some of the Tris have offset boards with little consequence to get additional cabin room, maybe worth just fitting one to begin with.

 

[sawmaster]

hey Par: As I understand it, the purpose of lead ( in the 14-15 % range) is to counteract the movement of the C L R forward caused by an assymetric waterplane as the boat heels. So I'm assuming, in boats intended to be sailed flat,somewhat less lead,or even a CE slightly aft of CLR might be desirable? Also, since the rudder can be a significant portion of lateral area in many dinghys,is its area considered in calculations of CLR? If not,I wonder why?