Outriggers for kayak

[JimD]

I think I have to do this. Have been sailing our dinghy lately and having such a blast and while out for a kayak paddle this afternoon it occurred to me that amas for the kayak is something I'd really enjoy. I know Michael Storer has plans for these:



and clcboats has these:



but I'll probably design my own 8 footers and use the sail off our dinghy:



Any advice re lateral resistance, rudder, CE and lead, etc?

I would use this kayak. My own design, very beamy and comfortable. The deck is cheapo door skin and has a couple rot spots so its time to open it up, redesign, reinforce, etc:

[Woxbox]

I made this argument before and pretty much got shouted down, but the major advantage of a trimaran is it's high initial stability, and therefore it's ability to carry a lot of sail on a very light boat. So I'll suggest that to have real fun with this thing, you'll want to use a bigger sail than that. Also, the stability from the amas means that the main hull can be very skinny and easily driven. That kayak will do fine, of course, but a skinnier one would offer even more speed potential. The other rule of thumb often ignored in kayak and canoe conversions is to place the amas so that they just touch the water when the boat is at rest with everyone aboard. You don't want to be dragging three hulls through the water all the time -- two is plenty. But it looks like a fun project. I just salvaged some aluminum tubing thinking it would be perfect for such a job.

[JimD]

I made this argument before and pretty much got shouted down, but the major advantage of a trimaran is it's high initial stability, and therefore it's ability to carry a lot of sail on a very light boat. So I'll suggest that to have real fun with this thing, you'll want to use a bigger sail than that. Also, the stability from the amas means that the main hull can be very skinny and easily driven. That kayak will do fine, of course, but a skinnier one would offer even more speed potential. The other rule of thumb often ignored in kayak and canoe conversions is to place the amas so that they just touch the water when the boat is at rest with everyone aboard. You don't want to be dragging three hulls through the water all the time -- two is plenty. But it looks like a fun project. I just salvaged some aluminum tubing thinking it would be perfect for such a job.

I think I could manage a bigger sail But I'm going to stick with this wide kayak, about 27" beam. I have another 22" beam kayak but its too nice a kayak to mess around with. And yes, I supposed the bottom of the amas should be at or even slightly above the loaded waterline of the main hull. That seems to be how these things are done.

[JimD]

Read a couple accounts of similar projects that say they don't tack very well. The wider the beam the less well they tack?

[Bobcat]

I have sailed a Windrider, which is a 16 foot tri, designed by Jim Brown, a couple of time. They are a blast and go like hell. Tacking is dicey because the boat is very light and next to no momentum. You have to be careful with the rudder; if you go too far over, it becomes a brake.

I had enough of a good time to consider building amas for one of my canoes. Haven't yet, but it's still on the list

[David Geiss]

Have had about 15 years with small tri, Fulmar 19', and some observations; YMMV:

It's tempting to show a lot of sail with an eye towards developing velocity. I say sometimes less is more. If you are driving your leeward ama into the water, reef, get the helm balanced and keep the ama from submerging. In a gust you'll be glad and in between the gusts the boat will sail efficiently.

Coming about. This small tri of mine likes to be sailed straight through the wind as opposed to bringing her to speed and then throwing the helm over.
Just sheet in as you bring her upwind and through the wind and you will have less drama.

Watch you fore/aft balance (people and gear) and get to know you leeboard, dagger or centerboard, as the case may be (obviously does not apply to Hobie Island Sail or similar). Too much board deployed on a beam or broad reach will give you too much weather helm and you may even hear cavitation...that's your signal that you have too much board showing. Start with less board than you think you might need and add as necessary, not the other way around. My feeling is that these little tris, in light of their three fine hulls, will slide to leeward a little less anyway.

As far as using a kayak for your vaka, I see that as pretty limiting. A decent 17' canoe, even an old Grumman will make a more utilitarian vaka. Think possible boom tent, guests on board, ability to stretch out, carrying of some gear including an anchor. I even like the idea of a single ama with a small tramp.
When it's to leeward, you are good to go. When it's to windward you have the tramp to sit out on to counteract the heeling and if the wind dies off the ama to windward will still keep you upright. Take a look at Canoes of Oceania, makes some notes and sketches and have at it.
The canoe will give you sturdy gunwales to play around with crossbar mounting, leeboard and mast step placement. Usually the seats can go and you may end up re-configuring the exisiting thwarts to optimize for sailing. Make sure you place the backrest thwart a little further aft than you might imagine. The ability to scooch your butt aft when before the wind (or broad reaching) is nice to have; plus, if you have another on board, further fore, you'll need to put yourself as helmsperson a little further aft (all other things being equal).

As far as steering, I am going to draw on some of my prior posts to say that paddle steering is where it's at for me.
Keep it as a canoe....... when the wind dies you'll be glad to have no rudder. As far as effective paddle steering, there are a number of ways to create a good fulcrum against your gunwale and it's simplicity defined (think leather strop or backrest thwart that overhangs the gunwales on both sides of the canoe by just a few inches......just hook well whipped paddle under the overhang, to leeward side of canoe of course.

I have an ama in progress form CLC plans (if you want to call my glacial pace progress) and my plan is to get it mated to one of my open sailing canoes and essentially bridge the gap between the Fulmar and my canoe sailing Then againg, the Fulmar is really just a glorified sail canoe.....

Yesterday out of Barnegat Inlet facing some 7' walls of water (non breaking) I realized that the traditions of the Balinese sail canoe can't be wrong....

Best,
David

[sailboy3]

I remember seeing a staysail schooner rigged kayak in the "launchings" section of woodenboat a while ago. No amas.

[JimD]

Thanks for all the input. Its definitely going to be the kayak and with a rudder. The kayak is already built, the cockpit is very comfortable and I'll use a spray skirt to keep dry. So it'll be a one person day tripper or possibly camp ashore. This is a Jim Michalak inspired design I thinkhttp://www.mclambs.org/trimaran/ :

[JimD]

Kurt Hughs has this niffty little 12 footer



Big amas to handle a big rig, I suppose:

[Woxbox]

Big amas because real trimarans sail on one ama at times, so it's best to be as long as the main hull and have a volume equal to a minimum 150% of the boat's displacement, with a good argument for 200%. Hughes did another one that was about 15' long, and was designed to come apart easily and go on a roof rack. The one-piece cross-arm unit was designed to be flipped over and turned sideways to act as a cradle for the hulls. Seemed like a good idea. Those 3-meter tris look like good fun, too.

[JimD]

Kurt Hughs 16 foot tri carries 155.5 sq ft of sail:

[JimD]

And Hughs 20 footer is 17' wide

[JimD]

Woods' 18' tri uses the hulls from his 16 ft beach cat.

[JimD]

Suppose I should get over to the Jim Brown Seaclipper thread with some of this so...back to a serious question re amas for a kayak. Storer uses deep vee hulls, triangular in section which also provide lateral resistance.



But dory hulls would have a lot more volume and boyancy. I intend to use the daggerboard off our dinghy for lateral resistance so dory hulls about 6" wide at the bottom sound like a good idea.

[Chris Ostlind]

Stayed rigs with significant horsepower really take this original idea far afield. Trimarans are all about balancing the forces present for a swift, safe ride. I can't tell you how many tri conversions I have seen over the years that looked at one aspect of the design process and then slapped together other elements without much thought as to how they would all work together. Consider your whole package and the way that the component parts will get along.

With the boat shown at the top of the page, start simple. Keep in mind that you will likely not be hiking out from the cockpit and that the ama volumes, aka sizing and aka length will have to do all the work of keeping your boat upright. Skinnier forms are usually faster through the water and weight is an absolute killer when it comes to utility (getting it put together and hauling it around) and especially to performance for a given sail area.

When looking for a little something extra, be very wary of the inevitable design spiral that is actually more like an alien vortex than something you casually talk about in the shop. Keeping this boat tidy, compact, as well as easily sailed and constructed, will lead to many hours of fun on the water. I'll be happy to give you some tips along the way if you run into any difficulties.

[JimD]

... be very wary of the inevitable design spiral that is actually more like an alien vortex than something you casually talk about in the shop. Keeping this boat tidy, compact, as well as easily sailed and constructed, will lead to many hours of fun on the water. I'll be happy to give you some tips along the way if you run into any difficulties.

That is good advice, Chris. I will keep this one simple. A couple 8 or 10 foot dory amas and small lug sail from the dinghy. Something I can scrounge bits and pieces I already have apart from the amas themselves and get it in the water quick and cheap. I'll go over to the Jim Brown tri thread to dream about something bigger and let the professionals design it. I've told myself I'll never build another boat bigger than a kayak anyway. Although Seaclipper 20 or something similar already has me backtracking.

[JimD]

... I'll be happy to give you some tips along the way if you run into any difficulties.

Any guidlines for placement of the amas, mast, sail CE, daggerboard? And I still want to be able to paddle this thing if necessary when the wind dies so there has to be room for a decent paddle stroke.

[Dan St Gean]

Have had about 15 years with small tri, Fulmar 19', and some observations; YMMV:

It's tempting to show a lot of sail with an eye towards developing velocity. I say sometimes less is more. If you are driving your leeward ama into the water, reef, get the helm balanced and keep the ama from submerging. In a gust you'll be glad and in between the gusts the boat will sail efficiently.

>>Good point! I agree & find the tradeoff of larger amas worth the hassle of larger loads on the structure.

Coming about. This small tri of mine likes to be sailed straight through the wind as opposed to bringing her to speed and then throwing the helm over.
Just sheet in as you bring her upwind and through the wind and you will have less drama.

>>Most multis need to be brought about with a bit of finesse rather than just slammed over.


As far as using a kayak for your vaka, I see that as pretty limiting. A decent 17' canoe, even an old Grumman will make a more utilitarian vaka. Think possible boom tent, guests on board, ability to stretch out, carrying of some gear including an anchor. I even like the idea of a single ama with a small tramp.
When it's to leeward, you are good to go. When it's to windward you have the tramp to sit out on to counteract the heeling and if the wind dies off the ama to windward will still keep you upright. Take a look at Canoes of Oceania, makes some notes and sketches and have at it.
The canoe will give you sturdy gunwales to play around with crossbar mounting, leeboard and mast step placement. Usually the seats can go and you may end up re-configuring the exisiting thwarts to optimize for sailing. Make sure you place the backrest thwart a little further aft than you might imagine. The ability to scooch your butt aft when before the wind (or broad reaching) is nice to have; plus, if you have another on board, further fore, you'll need to put yourself as helmsperson a little further aft (all other things being equal).

>>A canoe with all that beam will really limit a trimaran's speed potential though. All the canoe hulls in the size he'd be looking at are about 21" wide max!

As far as steering, I am going to draw on some of my prior posts to say that paddle steering is where it's at for me.
Keep it as a canoe....... when the wind dies you'll be glad to have no rudder. As far as effective paddle steering, there are a number of ways to create a good fulcrum against your gunwale and it's simplicity defined (think leather strop or backrest thwart that overhangs the gunwales on both sides of the canoe by just a few inches......just hook well whipped paddle under the overhang, to leeward side of canoe of course.

>>I prefer a rudder for a solo craft as paddle steering is a two handed affair--what to do with the sheet? A rudder solved my issues.

>>I also overdid the sail area a bit at 128 square feet of sail. My canoe would twist alarmingly in gusts. Reefed to 80 squares it was fine. I could go with a stayed rig, larger amas, and escalate the design spiral. Instead I went with a single ama and sail reefed.

fpage2.jpgDan
Best,
David

I'll try to lengthen the response here so it'll post

[wtarzia]

A few comments from sailing a rudderless shunting proa for three years and a ruddered (quarter and later stern) tacking single-outrigger for 5 years (small craft, 16 feet, 90-110s.f. of sail in jib-cat-ketch usually -- photos at www.wtarzia.com/outrigger.html):

-- Yes, they fast for their size; hull speed reached quickly in light air, and exceeded in good air. You can get away with smaller sail areas for safety and still go fast enough to have fun. Or you can power-up and risk a miserable capsize in a boat that is hard to right from a 180 (though righting very light and small tris as in kayak conversion should not be too bad with a righting line). There will be excitement left over aplenty because the disaster mode of outriggers is a little faster than on monos, and that keeps you on your toes. The outriggers are not training wheels, are some people joke, but a different way to sail, and come with their own skill-needs.

-- Outriggers sometimes have trouble tacking, but rarely does that mean a failed tack in my experience. As I just got done saying on the "Tiki 21" thread, I just push the mainboom over a little and it goes through. Since I use a mizzen, in some cases I need to slack the mizzen off a few seconds after starting the tack. I am experimenting with a small jib on a self-tending boom, and holding it a few second longer helps the tack sometimes but not as much as I had thought as it is additional force t overcome. A jib on twin sheets might be better way to hold it aback to go over.

-- I use a leeboard sliding fore-aft 40 inches between aluminum rails and wooden bearings. That allows lots of adjustment in CLR for the various possibilities (different sail altogether, or if I drop jib, or drop mizzen, or shift mizzen to become the main). Of course, it kicks up over obstacles. Also can easily adjust to reduce weather helm. The variables change from side to side on a tacking single-outrigger, but of course a different case for a double-outrigger/trimaran. I like it, but I never figured out the most graceful way to arrange it. The forces on it are strong so I wanted the bearings separated a lot, which puts the lower rail and bearing under water more than I would want (but the boat is fast enough -- maybe I'd hardly notice except for the gurgle and spray?). I encountered strong enough loads last week along the coast that both 1-inch square aluminum tubes were bent permanently a couple of inches. An outrigger stands up to take the stress rather than relieves it through heeling -- you must consider that.

-- By the way, an outrigger might turn out to be a wet boat. The verbs, "sprayed," "hosed," "firehosed" "drenched" seem to appear often when outrigger sailors describe a day of fast sailing. Thinking out spray angles and making dodgers can help a lot, though I tend to sail in waterproof-breathable pants, and a parka close at hand (or on warm days a PFD blocks some). Waves breaking over the ama when it is to windward also can send a lot of water down on you on a choppy day.

-- My ama is about a 100% ama. It holds my weight for re-entering boat after a swim, as well as its own robust weight and that of my solid Doug Fir akas. It is a deep-V design. A brisk sailing run in 10-15 wind can push it under when to lee (trimaran tack) but I have survived that -- I don't know why. Maybe the deep-V is so sharp-ended that it just continues knifing through, the center so buoyant that it keeps hoping to rise, and the deep-V shape so slanted that it gives a lifting force when pushed to lee? But I don't recommend that as a habit. The usual kayak conversion V-amas are not as buoyant and might trip the boat pushed down like that. Forming your own amas to modern trimaran lines (wave-piercing end, rocker aft, etc.) out of Dow foam (Home Depot) on plywood center, foam shaped/faired with hand tools then glassed over, is an excellent choice for efficiency, you could go with fine shapes made with strip planking. Gary Dierking's book, "Building Outrigger Sailing Canoes," inexpensive and available, shows you the various methods.

-- The market is getting more clever with inflatable amas to convert canoes and kayaks. I am going to try two 16 foot inflatables (11.5 inches biggest diameter, with appropriate rocker, etc., displacement something over 400 pounds, 35oz material and dual air chambers) to convert my outrigger to a small trimaran for the Everglades Challenge. It is an experiment, and who knows what I'll think, but the great thing with self-made boats is the fun in experimenting. The ama-ordering from Watertribe Inc. on their "shop" page (www.watertribe.com) is still under construction (I ordered my set informally with the plea I needed to get used to them before my ramp is snowed and iced in in Connecticut), but the system is being worked out, and their basic design is set. These amas seem to be a big improvement over previous inflatable amas on the market (I do not profit from sayng this) -- they are real amas for hard canoe/kayak sailing. I prefer solid wood, etc., but the special needs for transport down to Florida without dragging a trailer made me want to try them.

-- Learning to live with a design with increased set-up time may be the the worst challenge to overcome. If you compromise on beam, as I do, you can keep a small single outrigger on the trailer assembled, and in the garage (I have to given the layout of my city neighborhood and yard). That limits me to 7 feet total beam -- but I have great fun anyway (see my October 6 video on Youtube by searching under my account name 'wadetarzia'). Keeping it assembled in yard on trailer wins you another foot. Rooftopping a light boat but assembling akas/amas is OK, but if you have a long ride (as I do), assembly time starts eating at you. Really thinking out quick-cxonnections can help. No bolts! Horn cleats and lashing line is strong and fast and permits some good shock absorbtion. But I have no objection to snapping quick-connect tubing together if the idea is worked out and affordable.

-- The motion will be different from a mono. No long slow rolls -- they can be a little snappish. Not terrible, but noticeable. Think of it this way; when you sail on a mono, you will enjoy the easier motion, and when you return to the outrigger, you will enjoy the lightness and speed. Everyone should have a small outrigger to stimulate the neural wiring from time to time. -- Wade

[JimD]

Picked up a few sheets of 1/4" meranti today. I'm very tempted to make the amas only eight feet long for the sole reason of a quicker build since I wouldn't have to scarf.

Can I get away with only 8' long amas provided they are boxy enough to provide plenty of buoyancy? Or will they have really quirky handling characteristics because of the shorter length? I'm going to start cutting tomorow so if someone would like to talk me out of such short amas now would be the time.

[wtarzia]

Nice 8 foot amas can be built, but to get them both buoyant enough and efficient enough and not hard to look at, I'm not sure a plywood build is a good idea. Scarfing does not have to take so long if you don't use the planing method. Lay the edges together on flat surface covered with plastic, lay on 6 to 12 inches of glass, let it cure, turn over carefully, do it again. Or use a butt strap. I scarfed my hull and ama panels using a butt strap on the inside and 12 inches of glass cloth on the outside (12 inches let me feather down finely with plenty left for strength though some fairing compound helped, and when I glassed the whole hull over, hardly any evidence of the scrafing can be seen. Don't make the butt strap too wide or it will create a very evident flat spot when you bend the sides in.

I built an 8 foot boxy ama on my first outrigger, a proa (see it at http://www.wtarzia.com/Proa.html). I was impatient to get on the water, so I settled for an incredibly ugly fast-build. And it worked well, not even decked over, just some Dow foam blocks lashed in it. It slapped noisily in choppy water and drove me crazy, but at the higher speeds it sort of planed on its flat bottom. It was my first boat and I had no knowledge and little confidence, and I know now a better ama would not have taken much more time. --Wade

[JimD]

Wade, I know I'm just being lazy and impatient. If I were to make them longer than 8 feet I would just butt block them, which I've done many times and actually prefer to a scarf.

This the one, buddy?



Mine won't be quite so...white and green And they'll have a fair amount of rocker, a strong sheer, and I haven't decided on flair yet or just perfectly vertical sides ala Bolger with a reasonably sharp entry.

[wtarzia]

Yes, that's the old boat with the hasty-ama. OK, if you're going to do all that with sheer and rocker, I'm not sure why you wouldn't go that one step further and get out something longer -- I'd go with a quiet, efficient V-hull. But if your method is much faster to water, I won't argue any more (remember, you asked for an argument against it :-).

When Gary Dierking flies for a vacation on Fiji and builds an outrigger on the beach to use I (his Tamanu design), he takes about two weeks to complete a 20 footer. He uses a 6 inch dia. PVC pipe for the ama by bringing with him a bow plug shaped from foam and glassed over, made to fit perfectly in the pipe -- it ends up looking quite nice and is even closer to the Pacific tradition of log-amas, at least shape-wise. He has photos of it back several entries in his "outrigger blog" at blogspot.com. -- Wade

[Woxbox]

Jim -- A little math would help answer the question. The amas should have a maximum fineness ratio of 10:1, a higher ratio is better, like 12:1. So if they're 8 feet long, or 96", then they should only be 9.6" wide at the normal sailing waterline, which will be near the deck. The difficulty with using ply is that it's hard to achieve a high prismatic coefficient when no compound curves can be easily built in. So how much displacement can you get at 8 feet, using ply, and without making the ama too wide to perform? If you scarf up the ply and go to 12 feet, the numbers are way easier to get to where you want them. And the boat will sail both faster and more safely.

[JimD]

Keep in mind the sail I'll be using is about 40 sq ft. so how much bouyancy am I going to need? I might get around to adding another panel to the sail to bring it up to about 60 sq ft but even so you can see this is not intended as a performance tri. The amas are going on a kayak with a 27" beam and with such a small sail and such low heeling forces I think 8 foot amas about 8-10" wide with a maximum beam around 8 feet should keep me upright. If it turns out I really like this kind of sailing then maybe, maybe, think about a proper or cat.

[JimD]

I have sailed a Windrider, which is a 16 foot tri, designed by Jim Brown, a couple of time. They are a blast and go like hell. Tacking is dicey because the boat is very light and next to no momentum. You have to be careful with the rudder; if you go too far over, it becomes a brake.

I had enough of a good time to consider building amas for one of my canoes. Haven't yet, but it's still on the list

Looks like it's not too difficult to bury the amas on a Windrider:

[JimD]

I like this Cross 18. 200 sq ft sail area:

[Woxbox]

Jim -- Keep in mind that the buoyancy of amas in a converted kayak tri is a substitute for body weight to windward in a small, light monohull. Sitting in the kayak, you won't be able to shift your weight much. I won't say what you have in mind can't work, and if you don't like them, you can easily enough make up a longer pair and bolt them to the same akas. But the history of trimaran development is all about recognizing that the boat sails as much on the amas as it does on the main hull, and they have to be designed and built with that in mind.

[wtarzia]

Looks like it's not too difficult to bury the amas on a Windrider:

--- That seems so because his ama is wave-piercing. Notice how the middle part of that ama is still up, and it is probably fairly stiff, or at least in balance. I'm not saying he can't bury and go over, but an efficient ama shape will sometimes look pretty buried when it is still functional. That is what I was trying to say above when I noted that my ama has spent some good time under water but showed no signs of imminent failure to trip. -- Wade

[JimD]

Jim -- Keep in mind that the buoyancy of amas in a converted kayak tri is a substitute for body weight to windward in a small, light monohull. Sitting in the kayak, you won't be able to shift your weight much. I won't say what you have in mind can't work, and if you don't like them, you can easily enough make up a longer pair and bolt them to the same akas. But the history of trimaran development is all about recognizing that the boat sails as much on the amas as it does on the main hull, and they have to be designed and built with that in mind.

I'm starting to listen

[JimD]

Here is an interesting thread on converting monohulls to tri's. Wonder if I could put amas on our Glen-L Minuet? Hmmmm....

http://www.boatdesign.net/forums/mul...tri-27292.html

[JimD]

I'm convinced. The amas will be ten feet. Symmetrical to keep them simple. Flat bottomed, about 8 inches wide at the bottom and around twelve inch max beam at the sheer. Thinking plenty of rocker might help tacking so they'll be a little banana-ish in profile.

[wtarzia]

Certain profile of rockered ama could contribute to hobby-horsing. Best perhaps to adapt/copy the rocker on established modern trimarans. If Chris Ostlind is still reading here, I'll bet he can advise you. I say again, flat-bottom ama may drive you crazy with slapping sounds! Look at the design consideration for this on the Jim Brown "Janganda" amas if you do not believe my own experience is relevent. But you can later modify them with foam epoxied, shaped round, and glassed over on their bottoms, perhaps as winter project. -- Wade

[JimD]

The main hull will prevent hobby horsing and there won't be much flat surface presented to the water, especially when heeled there won't be any.

[Bobcat]

Looks like it's not too difficult to bury the amas on a Windrider:

It is. You can bury the main hull as well as you go through, not over, the bow wake when significantly overpowered. Time to throttle back when that happens.

It was a fun boat to sail, but you get really wet

[JimD]

Slight change of plan. Going to use the 'good' kayak, an occume built, sleek and fast Shearwater Merganser. Looks like this:



Going to put long, skinny, 12 foot vee amas on it. Double ended will be the easiest way to build them. Sound better?

[wtarzia]

The main hull will prevent hobby horsing and there won't be much flat surface presented to the water, especially when heeled there won't be any.

--- My heavily rockered ama and flared ama does seem to contribute to some hobbying on that tack, though it is the Wharram V-hull catamarans that have the most evident of this behavior, I am told. --Wade

PS -- And yes I like your 12 foot ama and kayak idea better.

[Dan St Gean]

Sound better?

Yep. One thing about tri's with low volume amas it that you can't pull up to any sort of dock, float, etc. You end up about 4-8' away from your goal and as you try to tie up the ama sinks from beneath you. I always shoot for a single outrigger if going for a little volume ama, and for tri's I like amas that can at least hold my weight.

Dan

[Milo Christensen]

I'm starting to listen

I'm convinced. . . . Flat bottomed, about 8 inches wide at the bottom and around twelve inch max beam at the sheer. Thinking plenty of rocker might help tacking so they'll be a little banana-ish in profile.

. . . Going to put long, skinny, 12 foot vee amas on it. Double ended will be the easiest way to build them. Sound better?

It's good to listen, and I'm glad you are. The flat bottomed amas had me worried.

[JimD]

First the 2 foot cardboard cut out to establish lines that closely follow the kayak hull:




Then take advantage of a warm sunny afternoon and loft full size onto a 13 foot long sheet of doorskin I had hanging around:



Short work with the jig saw eh voila! an ama template, more or less;



leaning against the kayak



And now I'm going for a paddle.

[Milo Christensen]

I can't tell from the picture, looks straight across, but I'd like to see some rocker in there on the bottom. I think I'd try a catenary curve starting 3" up at the bow and 1.5" at the stern.

[JimD]

I can't tell from the picture, looks straight across, but I'd like to see some rocker in there on the bottom. I think I'd try a catenary curve starting 3" up at the bow and 1.5" at the stern.

Milo, it doesn't show in the photo but its going to have decent rocker once the panels are stitched up. Might not have time to work on it any more for another week. Looks like I'm going through a multihull phase. I can't stop thinking about cats and tri's and have been perusing plans endlessly.

[PaulC]

What exactly are "door skins"?

[Woxbox]

It's looking pretty good. I think you're headed toward a design that will be rewarding to sail. But what's going on with the stern? Looks like a couple of sharp angles. I don't see how that's going to stitch up fair. Are you going to put little triangular transoms on them? A very fine, clean exit is best. FYI, the aggressively styled tris carry most of their volume in the forward half of the amas. This is to keep them from burying easily, but it also makes for a very long, easy run aft. Keeping more volume forward helps give the whole boat a bow-up attitude as it heels, which also fights any tendency to bury the leeward ama.

I wouldn't bother with asymetrical hulls, either. It's debatable how much net gain you get, since you pay for a little lift with more drag. On a small hull, I doubt the gains are worth it.

[JimD]

What exactly are "door skins"?

In this case, 1/8 inch, cheap, flimsy, mystery hardwood ply used for interior doors. As they are inexpensive they are good for making templates that can then be traced onto proper boat wood but are not very suitable to be used on boats themselves:

[JimD]

... what's going on with the stern? Looks like a couple of sharp angles. I don't see how that's going to stitch up fair. Are you going to put little triangular transoms on them? A very fine, clean exit is best. FYI, the aggressively styled tris carry most of their volume in the forward half of the amas. This is to keep them from burying easily, but it also makes for a very long, easy run aft. Keeping more volume forward helps give the whole boat a bow-up attitude as it heels, which also fights any tendency to bury the leeward ama. .

The stern of the amas will mimic the stern of the kayak, which as you say has a small triangular transom. It works very well and looks like this. As you can see its very narrow and I don't expect its going to create a whole lot of turbulence, deadwater, or all around drag:



Here's the bow



Floating:



And yes, I'm hoping my amas will have plenty of volume forward. The ama template is cut from 15 inch wide panel.

[JimD]

... I still like the idea of more room to move about than being skirted in a kayak but that would mean less sponging...
Best,
David

And there's the trade off. No sponging in the kayak. In fact, virtually no getting wet at all. On a cool, grey, drizzly day being skirted into a cockpit is amazingly warm and dry. Just make sure your hat has a wide enough brim to keep rain from running down the back of your neck and you won't even notice the weather. You see a lot of winter kayaking around here and almost nobody in a canoe. In fact even in summer you don't see canoes. The PNW is definitely kayak country.

[Dan St Gean]

that's one hand for the sheet, one for the helm and one for the bailer/sponge.

David

How do you manage to paddle steer with one hand? Tiny rig?

Dan

[JimD]

How do you manage to paddle steer with one hand? Tiny rig?

Dan

Yes, it does sound like someone is a hand or two short . For my conversion I'm going to see if I can use the rudder from this dinghy. Of course there would have to be a post for the gudgeons but that could possibly do double duty as something to run the mainsheet to. Especially if I sew up a junk rig for it (wink wink):

[wtarzia]

In this case, 1/8 inch, cheap, flimsy, mystery hardwood ply used for interior doors. As they are inexpensive they are good for making templates that can then be traced onto proper boat wood but are not very suitable to be used on boats themselves:...

--- Though one of my proa buddies used dorrskins glassed once both sides to result in a very light and pretty strong hull. -- Wade