Newbie needs help with small DIY sail plan, trimaran setup.

[Lee.007]

Hello all, I am new to the forum, name is Lee.

Bottom line up front:
Question 1 - I need a sail plan where I can cut and sew my own sail. Can anyone recommend the best free software, best book to read, or does anyone have a plan for an 84 square foot sail made from a polyester table cloth that is 90 inches by 156 inches?
Question 2 - How far out should I put outriggers on a sailing kayak?
Question 3 - Is a centerboard or a dagger board required on a small sailing trimaran to sail upwind?

The rest of the story:

I am an active duty Army Officer currently stationed in Georgia and I have always wanted an ocean going kayak to do some island hopping around the southern South Carolina, all of Georgia, and northern Florida coastlines. Well, I could not afford one that I considered safe to go to sea, so I decided to build one, which I started last August and finished this past February. It is a 17 foot cedar stripper that I designed myself with "kayakfoundry" (I have a lot of mechancial and electrical engineering experience). Problem is, it is so unstable that I cannot get in it from deep water, and I can barely keep it upright when I get in it from shallow water. It was ok (but not great) until I put the seat in it and raised my center of gravity up 5 inches. I consider myself an intermediate kayaker having grown up in the mountains of East Tennesee and done some river riding, but this beast is no pleasure craft and very unforgiving to reaching or leaning too far to port or starboard. So, "what to do?" says I.

I was about to cut it in half, because it has a very high deck for a kayak, and lower the deck with the intent of lowering the center of gravity. I wanted plenty of room for camping gear to support myself for a week. I made it big and round forward of the cockpit, and flat and big aft. I designed the bow and forward area with a large volume to pop up out of a wave instead of digging in. I worked the stern to be a little flatter so it would maybe surf a little. I worked the numbers in kayakfoundry until I got a small enough drag at 4 knots, about a 295 pound displacement, and a "stability factor" of 103. Cause the internet says a "stability factor" of 100 is supposed to be good, pffft. But hey, what do I know, I am just a Soldier not a Sailor.
The pictures are of me in the kayak before I put the seat in, sitting on the flat bottom. I could keep it up then, but really had to fire every core muscle of my body constantly to keep it upright. So I was about to take a saws-all to it, and my wife suggested, "wait, you've always wanted a sail boat, why don't you put outriggers on it, a mast, and make it a sailing trimaran?". And that's why I married her, cause she is smarter than me! What a wonderful idea, I said, why didn't i think of that?

So, here is the deal. I have researched and read and pondered and stressed myself out silly about what kind of sail rig to go with. I have just about settled on a balanced lug, with no more than a 10 to 12 foot mast (is it safe to go higher?). According to my total displacement with my outriggers added to the numbers, and some website I read, if i want to get 10 to 15 miles an hour out of it I need about 84 square feet of sail.
I have also read that you need to make your sail out of Dacron polyester. Well, my wife donated a polyester table cloth that is 90 inches x 156 inches, solid white, and works out to 97.5 square feet. I know it is not Dacron, but at least its not a poly tarp either. Now I know I cant just hang that up with a broom handle and some bailing twine, else I would look like some dude from the redneck riviera with his inner tube and a bed sheet. And I also want to be able to point up wind fairly decent. Will the table cloth be ok assuming I cut it and sew it into a decent airfoil?

I am building the outriggers now. I just basically made two 1/3 scale models of my kayak with no cockpit or hatches. Is there some number out there that tells me how far out from the kayak center line i need to put them? Or does everybody just do what looks pretty good and let out the sail if you start to tip? Also, I have seen some trimarans on the internet that don't seem to have a centerboard or a dagger board. Do small trimarans need one? I can build one into my kayak if I need to, but would prefer not to. I have plenty of room between my legs in the cockpit, but I don't want to cut into my hull if I don't have to.

I have plenty of time right now to work on this due to Army travel and working restrictions because of COVID, so any advice would be immensely helpful.

Well I guess I have taken up more of your time than I should have by writing so much. I do apologize, but would really appreciate any advice you guys may have for an Army dude that thinks he is a Sailor. Thanks!!

[bluedog225]

Welcome Lee! Nice boat. Stand by. Others will be along.

The old guys who know stuff go to bed at 8.

[Dusty Yevsky]

Hello all, I am new to the forum, name is Lee.

Bottom line up front:
Question 1 - I need a sail plan where I can cut and sew my own sail. Can anyone recommend the best free software, best book to read, or does anyone have a plan for an 84 square foot sail made from a polyester table cloth that is 90 inches by 156 inches?

Get some real sailcloth and make a real sail. A polyester tablecloth sounds like it would be shredded on your first trip


Question 2 - How far out should I put outriggers on a sailing kayak?

I've got a sailing kayak and the amas (outriggers) are ten feet apart or five feet from the centerline of the yak. Make sure the two akas (cross beams) are far enough apart from each other to take a natural paddle stroke

Question 3 - Is a centerboard or a dagger board required on a small sailing trimaran to sail upwind?

Some kind of foil is necessary, in the case of kayak this will be a leeboard. You also need to think about a rudder and pedal system.




The rest of the story:

it and raised my center of gravity up 5 inches.

5 inches is way too high for a kayak. At best the seat should be 3 inches of foam with a butt divot that almost goes the whole depth of the foam.



I consider myself an intermediate kayaker having grown up in the mountains of East Tennesee and done some river riding, but this beast is no pleasure craft and very unforgiving to reaching or leaning too far to port or starboard. So, "what to do?" says I.

As you progress as a paddler your self-centering muscle memory will drastically improve



So, here is the deal. I have researched and read and pondered and stressed myself out silly about what kind of sail rig to go with. I have just about settled on a balanced lug, with no more than a 10 to 12 foot mast (is it safe to go higher?).

Yes you can go higher, with properly designed akas and amas you will achieve monolithic stability.You need to worry more about mast and rigging breakage.

Will the table cloth be ok assuming I cut it and sew it into a decent airfoil?

Yes, but probably not for very long, consequently won't be worth the effort. Use real sailcloth available cheap from Duckworks.

I am building the outriggers now. I just basically made two 1/3 scale models of my kayak with no cockpit or hatches. Is there some number out there that tells me how far out from the kayak center line i need to put them? Or does everybody just do what looks pretty good and let out the sail if you start to tip?

You won't tip unless your amas are very, very small.


Also, I have seen some trimarans on the internet that don't seem to have a centerboard or a dagger board. Do small trimarans need one?

This depends on hull shape. Typical kayak hulls will need a foil and for practicality should be a leeboard.


I can build one into my kayak if I need to, but would prefer not to. I have plenty of room between my legs in the cockpit, but I don't want to cut into my hull if I don't have to.

I have plenty of time right now to work on this due to Army travel and working restrictions because of COVID, so any advice would be immensely helpful.

There are several plans available that detail a kayak to tri conversion. Here's a link to a very good set. Worth every penny. https://www.clcboats.com/modules/cat...oe-sailing-rig

Also, get a copy of these books.
https://www.amazon.com/Building-Outr...0055974&sr=8-1

https://www.amazon.com/Canoe-Rig-Essence-Sailpower-Traditional/dp/0937822574

Well I guess I have taken up more of your time than I should have by writing so much. I do apologize, but would really appreciate any advice you guys may have for an Army dude that thinks he is a Sailor. Thanks!!

Also, don't expect 10 to 15 knots. The limiting factor is hull shape for some slightly esoteric reasons. Expect a max of about 7 or 8, which will seem plenty fast.

I hope this advice helps.

[Andrew2]

Welcome Lee and a nice build. You might get some ideas by looking at Mead Gougeon's wotk. here: https://www.google.fr/search?sxsrf=A...sclient=psy-ab

Quite small outriggers and set fairly well out. A lee board or two would work for upwind, very common for kayaks.
A2

[Woxbox]

The boat looks nice. I think you can turn it into a good little trimaran.

For good performance, the outriggers or amas should be more like 2/3 length of the main hull, of at least 100 percent displacement of the craft when fully loaded, and ideally with a fineness ratio of 1/12. That is, if 12' long then 1' beam. Your sail area calculation sounds good to me. As to how far out the outriggers should go, enough so you can paddle it. A total beam of 8' should work, more wouldn't hurt.

What you need to appreciate is that when pushing a trimaran hard, you are sailing on the lee hull. The other two hulls are pretty much just along for the ride and providing good righting moment with their weight. The biggest mistake often made is to think of the amas as though they are training wheels on a bicycle. It doesn't work. If the amas are too short and/or too wide, they act like brakes. If too little volume, they dive underwater and the boat can flip.

CLC's solution.



Look at CLC's trimaran kit. You can get the study plan for a dollar, which will give you a good sense of what the proportions of a successful tri conversion for a kayak need to be.

As to the sail, you'll have better success looking for a very cheap donor rig. Scour Craigs list, eBay, etc. for a mast and sail combo of 60 to 80 square feet. Even and old beat up rig will work better than a tablecloth conversion.

Good luck and keep us posted. Your workmanship looks very good.

[Lee.007]

Thank you all so much for the advice. I am ecstatic at your responses, especially Dusty Yevsky

I just finished glassing the outside hull and deck of the "amas". I am learning big words now. They are about 70 inches long, beam of about 8 inches, height of about 5.5 inches. Pretty much an exact 1/3 scale replica of my kayak(see pic, this is the deck). Given that Woxbox said 2/3' the length of my hull, will they work or are they trash? I would like to use them if I can, I am out of epoxy and fiberglass and have to wait for more to be delivered, so I am not too far gone in the process. I won't be losing a lot of money in them, I made them from scraps, but I will be losing a lot of time and manual labor. Oh, and the shape is the same as the kayak so I was thinking my drag should be small? Or is there some parasitic thing that happens with the whole trimaran system when you make them too small? Thanks again guys!

20200729_175239[1].jpg

[Dusty Yevsky]

I've seen bigger and I've seen smaller. They should be OK especially considering your desire to use a balance lug sail, which can have a low center of effort. Aka length will figure into stability. Now it's going to get interesting as you figure out where the akas should be mounted on the hull and where the mast will be placed. You will need to really reinforce the hull and deck areas where the akas will make contact. First attach everything temporarily using straps and what not, and then carefully experiment in light conditions. Your aim is a balanced rig. You will need a rudder and this must be attached before you can find the sweet spot.

I suspect a lot of kayak/tris were built using TLAR engineering (That Looks About Right)

[Etdbob]

Hey Lee!

Thank you for your service. I'm an ex Air Force NCO myself.

Nice boat!
Dunno about making a tri out of it though -

The port of toledo community boat house has excellent plans for a 75 sq. ft and a 100 sq. ft. lug sails.
I highly recommend that you take a look at them.

The 100 sq. ft. was designed by John Welsford for his SCAMP sailboat.
These sails are shaped with curved edges and work surprisingly well.

http://toledocommunityboathouse.com/plans.htm

I've sewn the 100 sq. ft. version myself -



SAM_7214.jpg

This was the first sail I sewed, two previous sails I made were put together with carpet tape.
I'm a little concerned about the stretch of your table cloth fabric. Poly tarps do make great sails without a heck of allot of work, and I highly recommend making a tarp sail for your first sail making effort!

This lug of mine pulled great and was close winded.
All things considered, it was to much sail for the light 16 foot skiff though.

I don't think you need anything bigger than 75 sq ft. That's gonna be a light tri with little resistance.

image084.jpg

Jim Michalaks book, "Boatbuilding for Beginners and Beyond" also has plans and detailed directions for sewing together a 75 sq. ft. balanced lug sail, using darts to shape the sail.



https://www.amazon.com/Boatbuilding-.../dp/1891369296

[upchurchmr]

The ama shape with the deep belly would have worked better if it was more straight, with the volume not concentrated in the center. But those will work.
Like Woxbox says, you should have long skinny hulls.
If you compare what you made to the CLC plans, those hulls give 100#s of flotation, each. Getting the study plans is a great idea.
That means when you get too much wind in the sails, the hulls will tend to dive below the water, slowing you down quickly.
This can be a safety thing where you know when you are trying to force the speed too much.
If it happens all the time, you might want a smaller sail.

One thing that can happen with a boat with not enough buoyancy in the bow, is a heavy wind from behind can push the bow underwater. Not fun, pushed to extremes the whole boat might flip over upside down.
It might be difficult to stop a large sail from getting too much air if its coming from behind.
So like was said, start in fairly light winds.

You will have to have some kind of board to go upwind, a leeboard is the most reasonable thing.
BUT, it will need to be well braced to stay attached.
Without one, that round bottomed boat will just go sideways when you go upwind.

Sounds like fun. Good luck, Please keep reporting.

[Woxbox]

Thank you all so much for the advice. I am ecstatic at your responses, especially Dusty Yevsky

I just finished glassing the outside hull and deck of the "amas". I am learning big words now. They are about 70 inches long, beam of about 8 inches, height of about 5.5 inches. Pretty much an exact 1/3 scale replica of my kayak(see pic, this is the deck). Given that Woxbox said 2/3' the length of my hull, will they work or are they trash? I would like to use them if I can, I am out of epoxy and fiberglass and have to wait for more to be delivered, so I am not too far gone in the process. I won't be losing a lot of money in them, I made them from scraps, but I will be losing a lot of time and manual labor. Oh, and the shape is the same as the kayak so I was thinking my drag should be small? Or is there some parasitic thing that happens with the whole trimaran system when you make them too small? Thanks again guys!

20200729_175239[1].jpg

Lee,
I emphasize the need to have good length in the amas because you said up top that you're hoping for a fast boat. The speed a hull can be pushed to relates mostly to it's length, but also to how beamy it is. A 70 inch by 8 inch hull will max out at just under the root of the waterline length in feet times 2, the resulting number in knots. This is less than 5 knots for the amas you are making. Now, downwind where they're just skimming the surface you might get more speed than this, but off wind and upwind they will, as I said earlier, dig in and act like brakes. Or if not brakes, speed limiters. Also, your numbers suggest a total displacement when submerged of just 60 pounds or so for each ama. If this is so, it wont' take much to drive them underwater. Again, best practice is to have amas that can't be driven under very easily. (I used to sail a 27' trimaran that displaced about 3,000 pounds. The amas were designed at 100% displacement and they did indeed dive under more than once. It's not a great feeling.)

But if the amas are almost done, there's no harm in fitting out the boat with them and experimenting on a mild day. As has already been explained, you'll want a board or boards of some kind to prevent leeway. The relative location of the sail, the amas and the leeboard or daggerboard, whatever you fit, are all important to the overall performance of the boat. So to the extent that you can strap and clamp things together for testing, it will save a lot of headaches later.

This is why I suggest studying boats of this type that have been debugged. They have shapes and proportions that have been developed by years of study and trial and error. If your boat looks a lot different from the successful designs, you should have reason to think that it's not going to sail like a thoroughbred.

But that's not to say the boat won't work at all, or that it won't be fun, or a great development project through which you'll learn a lot and gain some skills. Tinkering with our home-built boats is half the point of going this route.

[johngsandusky]

Welcome aboard, thanks for your service!
A little sail will go a long way in a skinny hull. I use a 36 sq ft rig in a 28" canoe and it's a handful in a breeze. (Though I don't use outriggers)
If you're on Facebook, there's a Skinny Hull Sailing group with plenty of ideas and pictures.
Keep us posted.

[bluedog225]

I can’t add much to the technical discussion. Getting your sitter on the very bottom of the boat will help.

Some tippy boats have been stabilized by adding external sponsons. Or they could be integrated into the existing hull. Basically, tubes of air along the waterline. They work well for some sailing kayaks (Nautiraid).

You may also want a look at the CLC Waterlust. https://www.clcboats.com/modules/cat...-sailing-canoe

Sometimes, amas are more like backup safety devices instead of an integral part of the boat when it is sailing/rowing. E.g.:


613580CF-D335-4C77-8E61-AB3DAF9D399B.jpg


EBDDD8F2-A2E3-4205-862E-48587778ED2F.jpg

[Lee.007]

Gentlemen,

Again, many thanks for your advice and guidance. I was wanting to get some work done this week on my "sail-yak" but I bought my daughter a $500 Nissan Xterra that needed rebuilding. So, that's done, now back to the boat building!

I am going to give these amas a try, but still plan on building longer narrower ones if they don't work. I will definitely make my next boat (cause you can't build just one) a better sailor.

I am going to attach my kayak file from the kayak foundry software. If y'all want to download the software and pull in my file maybe you can tell me where I went wrong with the stability.

My ultimate goal is to do some multi-day island hopping without expending all of my energy just getting from one of the barrier islands to another around the southern Atlantic coast. I will definitely look into adding longer amas, especially if it increases my load bearing capacity. Maybe the wife can ride on my boat and I won't have to build her one too!

As far as attaching the amas, I have seen some designs that use PVC pipe and also epoxy and FG laminated wood. I am wondering what material to use. I am open to just about anything, except for super expensive carbon fiber. Also, I have seen some designs that lash their akas to their main hull, and others that bolt it down with some stainless hardware. Does anybody violently oppose or favor one versus the other? Do wooden pins work? Is there a better way?

Thanks again guys for the advice and links to reference materials!

[Lee.007]

If anyone wants to email me, I can send them the kayak design file. file type is a ".yak" file.

[upchurchmr]

Use wood for the aka's, don't ever use PVC (too flexible).
And don't count on the amas to add to your bouyancy, that just makes your boat into a raft and it will be much harder to tack.

[Lee.007]

Ok, so after looking into the poly tarp sails, I think I just might give that a try... we will see how it goes.

[bluedog225]

Lots of success stories with poly tarp. Next to free and you can work out what work and doesn’t.

[Lee.007]

Hey All, So I have been working on sail design, ama design, and just how I plan to mount a mast and amas to the kayak. Here is an autocad rendering of what I plan to do (sorry about the wire forms, kayak foundry doesn't play well with autocad). The amas are 5 feet from center line of the kayak. I have centered them vertically on the same design waterline as the kayak. That is to say the design water line of the amas are in line with the design water line of the kayak. I plan to make the akas out of 1.75" x 1.5" cedar. Attachment from the amas to the akas is 0.75" x 3" cedar. I acquired a lot of cedar from my father in-law. I also plan to make the mast and boom out of cedar. Mast is 13 feet tall from the deck of the kayak, boom is a little over 10 feet. I plan to reinforce the cedar beams and mast with fiberglass and epoxy. Sail area works out to about 60 square feet, and I am putting the center of effort of the sail about 38 inches in front of the center of lateral area of the kayak. Works out to about 12% of lead, if my math is right and according to "The Sailmaker's Apprentice". Do yall think that is that the right amount of lead for this kind of kayak/trimaran?

I feel sailor-smart now(yep, I am probably dangerous), i have been doing a lot of reading. Many thanks to all for the book suggestions. I have "The Sailmaker's Apprentice", and the paper on sail making by Tom Bradshaw that upchurchmr sent me. That is what I used to design the sail. So now it is your turn to ponder over my design, and offer advice. If you think it is going to go over like a turd in a punch bowl, feel free to let me know, but tell me why so I can get better. I have not cut the akas, the mast, or the boom yet, so I can still make modifications.

Oh, I know Dave said my akas need to be longer, but for now I am going to try these out since I have invested so much time in them. They are about 6 feet long. If they become water brakes, I will chuck them and build longer ones. Maybe I will get lucky!

By the way, is it bad luck to sail in a boat without the boat having a name?? Seems like I heard that somewhere...
KayakSail.jpg

[Dusty Yevsky]

I plan to make the akas out of 1.75" x 1.5" cedar. Attachment from the amas to the akas is 0.75" x 3" cedar. I acquired a lot of cedar from my father in-law. I also plan to make the mast and boom out of cedar. Mast is 13 feet tall from the deck of the kayak, boom is a little over 10 feet.

Cedar is not a strong wood at all and not recommended for spar building. Spruce or doug fir are your go-to woods. Making the the akas out of cedar is doable BUT you absolutely need a laminate of stronger, bendable wood like ash on the top and the bottom. The akas (they're really called iakos) are beams and all the tension and compression forces are in the outer layers.

I wouldn't use cedar for a mast. The forces on a trimaran mast are considerable because the main hull will not heel and relieve the strain. If you still want to explore it though here is a link for a company that makes tubular fiberglass sleeves. this is an interesting project so keep posting.

https://www.sollercomposites.com/FiberglassSleeves.html

[upchurchmr]

Your CE of the sail should be behind the center of lateral resistance of the hull. If not, it will tend to always turn to sail downwind and will be uncontrollable. You didn't mention a daggerboard or leeboard. This is absolutely necessary if you want to sail to windward. 5' ama's are very short, but have been used before. Sometimes it is hard to understand why a boat is slow. Short ama's could be a cause. Small ama's will not let you use the power of the rig to go faster, since they will submerge early and you will have to slack off the sail. But you are getting to where you will be able to sail, which is more than a lot of people.

[johngsandusky]

I agree that cedar is limber for a mast. If you use it, I suggest rope stays.

[Woxbox]

Lee,
The amas need to just touch the water, or even clear it by a couple of inches, when the boat is fully loaded and at rest. If you set them as shown, they'll be adding unnecessary drag when you're running downwind or in very light air. Setting them higher also reduces the frequency with which the windward ama slaps the waves. Higher is always better than lower in this design point.

These boats have been made without a leeboard or daggerboard, but having one would improve windward performance noticeably. But I think it makes sense to proceed without one, do some sea trials, and then add something based on your experience.

As to wood choices, I have no disagreements with the comments, but it is also true that any wood can be reinforced with glass or carbon fiber to the point that this added layer takes all the stress and the wood within is just filler material to create the shape. Once you reach that point, even balsa is workable. Unidirectional fabrics are best for this. You're not likely to break the amas if the grain in the wood runs straight, but I would be concerned about the mast.

[Lee.007]

Thank you all for the comments!! I was debating whether or not to use Cedar for the beams and mast as opposed to SPF lumber from lowes. No matter what I use, it will be sealed against the elements with epoxy, and fiberglass for re-enforcement where needed. I was wanting to use cedar to keep the "home built cedar strip kayak" theme. But I totally understand that I must not sacrifice sound seaworthy design for silly pride. Cedar also has lots more knots in it than SPF, and I can get SPF in much longer lumber than cedar. Anybody have any opinions on wooden closet rods for booms? Or even masts? I assume, possibly making a flawed assumption, that curtain rods have to be made of pretty stout wood to hold up all the clothes our ladies acquire? I will also check into those fiberglass sleeves y'all mentioned.

Oh, Rudder and Dagger Board, I just haven't gotten to these yet. I do plan on doing a dagger board. There is plenty of room in the kayak between my knees to build a trunk for a dagger board, and I have found some designs on the internet for some dagger boards. Does anyone have any suggestions for a good design for dagger boards and rudders for this size of a rig? I know there has got to be some relationship between amount of surface area of dagger board needed to turn a certain size boat? I did think of a lee board, probably be much easier to build, but just can't wrap my head around the ugliness of it being attached to the side of my kayak. Again, my foolish pride.

For upchurchmr's comment about center of effort - according to page 35 of "The Sail Maker's Apprentice", the center of effort should lead, be in front of, the center of lateral resistance. Now, me being a Soldier and not a Sailor, I could certainly see how it could be different for different types of boats. The boat pictured on page 35 is a gaff rigged sloop. Is it different for a kayak trimaran? By the way, without doing some calculus that I don't have the time or desire for, I used kayak foundry's number "center of lateral plane" and assumed that it is the same as center of lateral resistance cause the two descriptions I could find sounded pretty much the same. But then I got to thinking, what effect, if any, do the amas have on center of lateral resistance? If I set them high as Dave suggests, then I assume no effect until the whole rig starts to heel. Thanks for the idea Dave, I do like the thought of the amas just skimming the surface until they are needed. And where should I put the dagger board? Does it go dead center on the CLR? Or does it lead or lag the CLR? I guess its position could counter any negative effect of lee or weather helm? Thoughts?

I am very grateful to all of you for your support in my efforts. Keep it coming! I hope to have this thing on some water before winter!!

[bluedog225]

Something to the side might be good as you can experiment with position.

114DE282-F8C6-4493-8E45-FF9C9AA581E8.jpg

[Woxbox]

Also -- if there are any knots chances are the timber will snap. Having straight, tight grain is just as important as the species of wood.

As far as location goes, you need to add the daggerboard to the area below the waterline as part of the exercise of figuring the center of lateral resistance. Keep in mind that CLC is a tool designers use to figure out how to balance a sail plan -- the center of effort of the sail(s) and center of lateral resistance do not, when the boat is sailing, actually line up with the dots on the paper. Not even close, actually. This is why designers add percentage leads that have been found to work over the years. Different types of hulls and rigs needs different adjustments. And yes, multihulls are different than monohulls in this regard. This is why being able to move the board fore and aft to find the best location is really useful. Another common adjustment is to rake the mast back a bit if more weather helm is needed. The more flexible your boat is, the easier it will be to get it sailing well.

I would clamp the board on the side, too. Much more flexible for experimental work. Once you get the right size and location, a permanent case might make sense. A board like the one Bluedog shows will kick up if it hits anything, too. Good luck with it.

[upchurchmr]

I second Wox and Bluedog on the leeboard idea.
Especially if you need to move it to make things work.

I don't know what is going on with your Sailmakers Apprentice book, but you will be in big trouble if you follow what you said.
The thing you want is for the boat to turn upwind when you release the tiller/ rudder while heading upwind. This is a safety measure. It is known as weather helm, since the tiller is pulled to weather (towards the wind) to make the boat go straight. A little is a good thing, too much is bad, just as having to push the tiller away (lee helm) is also bad.

When you first try the boat, deliberately head up wind from your launch point. That is so if you have trouble, you will have a chance of getting back to the launch point without being blown all the way down the lake.

There are some kayak sailboats that work (poorly) with no centerboard or leeboard when going to windward. Those typically have a flat bottom or sharp edges from chines in the water.
You have a nice smooth rounded bottom, which will not generate much if any side force to allow you to go up wind.
With your round bottom (the boat of course) you can just assume the leeboard provides all the sideways force. Ignore the rest of the hull as it will generate very small force.

No matter what you choose, please provide status reports when you get to sailing. Lots of people need the feedback as to what works, and why as much as possible.
Good luck.

[Dusty Yevsky]

Oh, Rudder and Dagger Board, I just haven't gotten to these yet. I do plan on doing a dagger board. There is plenty of room in the kayak between my knees to build a trunk for a dagger board, and I have found some designs on the internet for some dagger boards. Does anyone have any suggestions for a good design for dagger boards and rudders for this size of a rig? I know there has got to be some relationship between amount of surface area of dagger board needed to turn a certain size boat? I did think of a lee board, probably be much easier to build, but just can't wrap my head around the ugliness

Take the advice about the leeboard. One of the great things about kayak tri is the ridiculously thin water you can take them in. This opens up some really interesting places that would be cumbersome at best to navigate with a dagger board. Want to see some real ugliness? Hit a rock at speed with a daggerboard and see the daggerboard case separate from the hull. UUGGLLEE!!!!!
As far as rudder specs go, build a balanced one that can be deployed and retracted from the cockpit via a rope trolley. The Watertribe site has a nice plan.
http://www.watertribe.com/Magazine/Y...cWTRudder.aspx

Edit: the plan used to be free but WT is now charging $35. If the plans are detailed then it's worth it.

I built one for a 21' kayak tri and am happy with it, especially the ability to raise and lower it from the cockpit.

When researching this rudder I came across a spec that said a rudder area should be 1.5% of sail area. My leeboard was built to CLC's Sailrig dimensions so no real suggestions there. Perhaps some of the very knowledgeable NA's on this site will chime in.

[Lee.007]

Want to see some real ugliness? Hit a rock at speed with a daggerboard and see the daggerboard case separate from the hull. UUGGLLEE!!!!!

So that does sound ugly. Kind of like stubbing your big toe on a rusty nail while running at full speed. So I am thinking best of both worlds. What about a swing keel dagger board??? I am going to start drawing up some ideas. I think I have enough room in my cockpit to rig that up. And put in a quick release mechanism that is also adjustable so I can lower or raise the dagger board. A spring detent ball seating in half circle dents in an arc that matches the swing of the board is coming into vision....

For a rudder, here is what I have drawn up so far, after looking at the one on watertribe.com. Still debating how to do my hinge. Thanks for the good ideas!

I had to be on duty this week so not much building got done on the kayak, but I did get some design time going:

KayakRudder2.jpgKayakRudder.JPG

[upchurchmr]

A pivoted daggerboard is called a centerboard.
Whatever you do don't put a horizontal plate at the end.
Doesn't help unless it is specifically designed, and retracting it into the boat will slow the boat until you get it fully retracted. And the case in the boat for that will be a terror to build and seal.
It will really spread your legs also.
The great thing about a centerboard is that it still works (mostly) when partially retracted.
It also has the benefit of being able to shift the CLR aft when you partially retract it.
Controlling it with a line that can pull free means hitting a rock or the bottom allows it to retract to prevent catastrophic damage as in Dusty's post. Same as a leeboard.

It doesn't need to look like a daggerboard, one of the faster (and older) catamarans has one that looks like a rounded triangle.

[Lee.007]

It doesn't need to look like a daggerboard, one of the faster (and older) catamarans has one that looks like a rounded triangle.

Aha! Now that reminds me of a geometric relationship trick I used to use with some mechanical machines I built in the past. (before I came back in the Army I was an electro-mechanical design engineer). So you set 3 circles in the same plan as pivot points. 3 points, triangle, right? You play with the pivot radii until you get the motion and range you want from a small movement on one, and a larger movement on the other. The only draw back is the smaller movement takes waaay more torque to move it. So, I can set the pivot point in the bottom of the hull, create a small movement at the top of the centerboard that induces a large movement at the bottom to swing the centerboard down quickly! Yep, I am going to head in this direction and see what I can come up with. Just need to make sure I get enough square footage in the water when it is fully down. I will post my drawings when I get done.

[Todd Bradshaw]

It's also possible to build a daggerboard case containing some rollers for a circular daggerboard, which will kick up if you hit something.

circular-db.jpg

[tom151]

Leeboard.

[Lee.007]

Ok, so after much deliberation, drawing in autocad, and scratching my head, I think i will just do a leeboard. Doesn't look nearly as nice and neat, but after breaking out the tape measure I realized my cockpit is actually tighter than I thought. And I like the idea of building a mount on the side of my yak, and then sliding a dagger board fore and aft as needed to adjust weather helm.

There is just barely enough room to get a centerboard case in the cockpit, but if for some reason I came to a sudden stop, I would crush the family jewels on the case between my legs. I guess I could put a seat belt in there, but I don't like that idea in case I need to bail out quickly or jump up and adjust the trim. There just isn't the room I want to put the case in and also be comfortable.

I have also decided on building a birdsmouth mast and boom. I got some Spruce/Pine/Fir (SPF) at lowes the other day and will start ripping it up tomorrow since I am in my "tele-work" week. SPF is about all I can afford in the 16 foot length I wanted. I am thinking 2.5 inch diameter, 0.5 inch thick staves. Total mast length above the kayak will be about 13 feet. Is that about right as far as thickness goes for a 60 square foot sail?

Would anyone be violently opposed to me making the aka's out of birdsmouth beams as well?? I was thinking they would be structurally a little stronger. Or should I just cut some solid 1.5 x 2 boards, strap them on, and call it a day?

[Lee.007]

Oh yeah, another question I came up with while contemplating the mast, what is the best way of attaching it to the kayak so that I can easily mount and dismount it and throw the whole rig up on top of my Jeep?

[Dusty Yevsky]

Would anyone be violently opposed to me making the aka's out of birdsmouth beams as well?? I was thinking they would be structurally a little stronger. Or should I just cut some solid 1.5 x 2 boards, strap them on, and call it a day?

Birdsmouth for akas is way too complicated. Sawn akas will likely have some endgrain where you don't want it and will be weak. You need something very strong. Solid lamination is the way to go, for several reasons. If you carefully select your stock you can get vertical grain laminates for the full length of the akas, which will be very strong. Also you can easily make the shape you want on a form and bend the aka to your desired shape. Akas tend to be curved so the ama is not sitting so far from the surface as to make the hull heel excessively. Lastly you can mix woods to get an optimum strength/lightness ratio. Hardwood such as ash for the top and bottom skins and soft wood like spruce for the inner plies.

Oh yeah, another question I came up with while contemplating the mast, what is the best way of attaching it to the kayak so that I can easily mount and dismount it and throw the whole rig up on top of my Jeep?

You will need a step and a mast partner. The step should be permanently affixed to the hull.It should be reinforced. The partner could be attached to the front ama. The mast is then simply dropped down through the partner and into the step. You could devise some sort of retaining setup using bungees, pins, etc. for the unlikely event of capsize or turtling.

Also, as you are designing this give some thought as to how you will attach the akas to the hull (vaka). The ancient Micronesian engineers settled on lashings and this technique is time tested and proven. The forces exerted on the aka/vaka connection are considerable and lashing have the very desirable trait of mitigating shock loads