Aloha, all,
Finished the inlay today, waiting for it to dry before sanding...Looks pretty good, I think.
This question's about using a double outrigger setup for sailing.
When using a single outrigger, the drag of the outrigger tends to make the canoe turn toward the outrigger. This is countered by moving the front end of the ama closer to the canoe than the aft end. I'm told that the way to find the proper amount to bring it in is to load the canoe and have someone push it foreward in calm water. The foreward iako is pulled in a little and the process repeated until you find the proper "cant" that makes the canoe go straight.
I'm wondering if my double outrigger setup needs to have some "cant" on both sides, and if so, how do I figure out how much, since the iako are going to be one piece, and can't be moved to one side without "canting" the opposite ama the wrong way? The front iako would have to be shorter to cant both amas in.
I thought about making the single ama setuip first, finding the proper amount of cant, then incorporating this into the double ama rig, but I'm sure the drag created by the wind pushing the ama down into the water is a lot different from what would occur paddling.
Todd, I guess I'm probably going to have to rely on you for this one, as I haven't seen anybody else talking about outriggers, but I thought the rest of the group might get something out of your answer.
Mahalo,
Kent
Double outrigger setup
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KARKAUAI
- Posts: 362
- Joined: Sat May 08, 2004 3:06 pm
- Location: Hickory, NC / Princeville, Kauai, HI
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Aloha, all,
I got this email response from Gary Dierking, the designer of Ulua. Stll would like to hear any other thoughts anybody has.
Kent
"I tried this with my Ulua and could feel no difference at all, but I'm sure it probably
increases drag slightly. When sailing with a single ama, the pivoting leeboard is swung
fore or aft on each tack to neutralize the effect of the ama drag.
No trimaran designs that I know of use any toe-in on the amas. I'm sure it would only
screw up the flow along them. If you calculate in the leeway angle, an ama would
actually cause less drag toed out. I'd advise just keeping everything parallel.
Gary"
I got this email response from Gary Dierking, the designer of Ulua. Stll would like to hear any other thoughts anybody has.
Kent
"I tried this with my Ulua and could feel no difference at all, but I'm sure it probably
increases drag slightly. When sailing with a single ama, the pivoting leeboard is swung
fore or aft on each tack to neutralize the effect of the ama drag.
No trimaran designs that I know of use any toe-in on the amas. I'm sure it would only
screw up the flow along them. If you calculate in the leeway angle, an ama would
actually cause less drag toed out. I'd advise just keeping everything parallel.
Gary"
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Todd Bradshaw
- Posts: 92
- Joined: Tue May 11, 2004 8:16 pm
Gary certainly knows a heck of a lot more about outriggers than I do, but these are my thoughts:
Paddling - You are mating a narrow, very V-bottomed main hull which is going to want to track pretty well, despite it's rocker, with an ama (or amas) having a much smaller cross-section, a rounded bottom and not much to give it directional stability other than it's length. It will cause a bit of drag, but I would think that it will be substantially less than one could easily correct for with a paddle almost without thinking about it, the same way a regular canoe's paddler corrects the boat's course with a J-Stroke. Paddlers routinely do the same thing when dealing with cross-winds, quartering winds or waves. The problem with trying to toe-in the ama to make a predetermined correction is that the only thing that is constant in the entire scenario is that nothing is constant. You are out there coexisting with water and wind conditions that are constantly changing, both minute to minute and day to day, and any change in displacement (add some gear or a companion) or upright attitude (lean over just a little bit) will likely make changes in the amount of drag created by the ama and the effectiveness of your toe-in correction. In addition, even though it's cross-section doesn't create big amounts of directional stability, I seriously wonder whether toeing-in the ama enough to make the boat push forward in a straight line won't result in an ama that's creating even more drag than it did before?
What might be possible on a racing outrigger, built to track like it's on rails and paddled very consistently by a marathon racer, most likely doesn't apply very well to a more general touring model like the Ulua. You certainly don't want to have to stop, do some testing and reposition the ama every time you take the boat out or every time the wind or wave conditions shift a little bit. My gut feeling is that it's far too easy to "over-think" the issue and you're probably better off to set the ama straight and go paddling. A solo paddler tends to push his canoe off toward the side opposite his paddling side - the reason for things like J and C strokes, pitch-strokes, diagonal draw strokes, etc. which correct by bringing the boat back on course. If in this case, you happen to be paddling on the ama side of the outrigger, it's possible that the ama's drag will do some of this correcting for you, requiring less correction to be done with paddle strokes.
Sailing: The trimaran that we used to own was nearly 16' wide and had big amas which were set straight. I don't remember ever feeling like they were really effecting the steering, especially in comparison to sail trim or centerboard angle, both of which which can effect it significantly. The catamarans we've had often sail with one hull running deep and creating a fair amount of drag and the other riding high, or even flying. The helm (steering) doesn't change dramatically at all during the various phases from riding level all the way up through flying one hull, even though the ratio of drag being created and shared by the two hulls at any one moment may be very different from what it was just seconds earlier. On a canoe, slight changes in fore-and-aft trim are also going to be a big factor, since they have a significant effect on the steering by shifting the Center of Lateral Plane and it's relationship to the sailplan's Center of Effort.
A trimaran's C.L.P. is also constantly changing because at any one moment, various parts of the two amas will actually be in the water, creating drag and lateral resistance, and others will be flying and not contributing to either. Half a second later (or whenever you come to the next wave) things will have changed. One of the things I dislike most about trimarans is that even when sitting still, they wobble. As various portions of the hulls catch waves they go up and down. If you're anchored and trying to eat lunch, it can really be somewhat nauseating, much more so than on a monohull, where the motion tends to be a little more more predictable. When moving, the tri stables-out quite a bit, but even so, the C.L.P. and it's relationship to the C.E. are always changing. What you're thinking about doing would only affect the way the boat steers or tracks part of the time. The rest of the time, the correctiont might be the exact opposite of what you're trying to achieve. Being able to reach over and shift the leeboard forward or backward a few degrees or shifting your weight slightly should have a much greater effect.
Paddling - You are mating a narrow, very V-bottomed main hull which is going to want to track pretty well, despite it's rocker, with an ama (or amas) having a much smaller cross-section, a rounded bottom and not much to give it directional stability other than it's length. It will cause a bit of drag, but I would think that it will be substantially less than one could easily correct for with a paddle almost without thinking about it, the same way a regular canoe's paddler corrects the boat's course with a J-Stroke. Paddlers routinely do the same thing when dealing with cross-winds, quartering winds or waves. The problem with trying to toe-in the ama to make a predetermined correction is that the only thing that is constant in the entire scenario is that nothing is constant. You are out there coexisting with water and wind conditions that are constantly changing, both minute to minute and day to day, and any change in displacement (add some gear or a companion) or upright attitude (lean over just a little bit) will likely make changes in the amount of drag created by the ama and the effectiveness of your toe-in correction. In addition, even though it's cross-section doesn't create big amounts of directional stability, I seriously wonder whether toeing-in the ama enough to make the boat push forward in a straight line won't result in an ama that's creating even more drag than it did before?
What might be possible on a racing outrigger, built to track like it's on rails and paddled very consistently by a marathon racer, most likely doesn't apply very well to a more general touring model like the Ulua. You certainly don't want to have to stop, do some testing and reposition the ama every time you take the boat out or every time the wind or wave conditions shift a little bit. My gut feeling is that it's far too easy to "over-think" the issue and you're probably better off to set the ama straight and go paddling. A solo paddler tends to push his canoe off toward the side opposite his paddling side - the reason for things like J and C strokes, pitch-strokes, diagonal draw strokes, etc. which correct by bringing the boat back on course. If in this case, you happen to be paddling on the ama side of the outrigger, it's possible that the ama's drag will do some of this correcting for you, requiring less correction to be done with paddle strokes.
Sailing: The trimaran that we used to own was nearly 16' wide and had big amas which were set straight. I don't remember ever feeling like they were really effecting the steering, especially in comparison to sail trim or centerboard angle, both of which which can effect it significantly. The catamarans we've had often sail with one hull running deep and creating a fair amount of drag and the other riding high, or even flying. The helm (steering) doesn't change dramatically at all during the various phases from riding level all the way up through flying one hull, even though the ratio of drag being created and shared by the two hulls at any one moment may be very different from what it was just seconds earlier. On a canoe, slight changes in fore-and-aft trim are also going to be a big factor, since they have a significant effect on the steering by shifting the Center of Lateral Plane and it's relationship to the sailplan's Center of Effort.
A trimaran's C.L.P. is also constantly changing because at any one moment, various parts of the two amas will actually be in the water, creating drag and lateral resistance, and others will be flying and not contributing to either. Half a second later (or whenever you come to the next wave) things will have changed. One of the things I dislike most about trimarans is that even when sitting still, they wobble. As various portions of the hulls catch waves they go up and down. If you're anchored and trying to eat lunch, it can really be somewhat nauseating, much more so than on a monohull, where the motion tends to be a little more more predictable. When moving, the tri stables-out quite a bit, but even so, the C.L.P. and it's relationship to the C.E. are always changing. What you're thinking about doing would only affect the way the boat steers or tracks part of the time. The rest of the time, the correctiont might be the exact opposite of what you're trying to achieve. Being able to reach over and shift the leeboard forward or backward a few degrees or shifting your weight slightly should have a much greater effect.
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Chris Ostlind
- Posts: 20
- Joined: Tue May 18, 2004 6:03 pm
- Location: Salt Lake City
two amas
I essentially agree with everything Todd has related.
I've paddled a lot of one, two and six man outriggers; casually as well as in races. Perhaps the only time I have ever experienced anything like a "pull" to one side due to ama drag wa sin totally glassed-off conditions. It was easily corrected with paddle strokes.
Todd, I hear you about the rocking motion at rest in a tri. My solution was to hang a large water filled bag that has holes in it, just even with the outer deck of a single ama both fore and aft. The rocking is reduced to a smooth, predictable motion and sleep can be had as well as sandwiches and beer.
Chris
I've paddled a lot of one, two and six man outriggers; casually as well as in races. Perhaps the only time I have ever experienced anything like a "pull" to one side due to ama drag wa sin totally glassed-off conditions. It was easily corrected with paddle strokes.
Todd, I hear you about the rocking motion at rest in a tri. My solution was to hang a large water filled bag that has holes in it, just even with the outer deck of a single ama both fore and aft. The rocking is reduced to a smooth, predictable motion and sleep can be had as well as sandwiches and beer.
Chris
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KARKAUAI
- Posts: 362
- Joined: Sat May 08, 2004 3:06 pm
- Location: Hickory, NC / Princeville, Kauai, HI
- Contact:
Thanks, Guys,
Looks like a set of parallel amas is what I want. The guy who described the toe-in to me was a third generation canoe builder/repairer who deals almost exclusively with classic Hawaiian canoe designs. They all have a completely rounded hull, stem to stern. Maybe that feature allows more sideways crabbing that the ama would aggravate? In any event, as Todd pointed out, Ulua is not a classic Hawaiian hull, as it has significant vee fore and aft, with a small vee amidships. Gary designed it this way because it would track better when sailing. The only down side of this modification is that when surfing steep waves, if it gets turned a little across the wave, there'll be no rescuing. It will round up parallel to the wave and "huli" (flip over sideways) if the wave is breaking. This canoe will probably do everything but surf better than a classic hull.
While I'm on the subject of outriggers, I'll be ready to work on my iako in a week or so. I've only tried laminating once before when I made the stems, and they didn't want to stay the shape I bent them to, even after gluing up on the forms. The curve was minimal, and I was able to pull them into shape on the stem molds and hold them with screws. If this happens with my iako, the amas won't be at the right height relative to the waterline of the hull. How do I make the laminated bends hold their shape? Do I have to bend each laminate to exact shape first (which I don't think I could do), or is there some other trick? I'll be using 13ft 1/4" strips of mahogony with a single 13 ft strip of maple in the center of the 7 board layup, so I'll have a good bit invested in the material, not to mention my time and angst. I'd like to get it right the first time.
Mahalo,
Kent
Looks like a set of parallel amas is what I want. The guy who described the toe-in to me was a third generation canoe builder/repairer who deals almost exclusively with classic Hawaiian canoe designs. They all have a completely rounded hull, stem to stern. Maybe that feature allows more sideways crabbing that the ama would aggravate? In any event, as Todd pointed out, Ulua is not a classic Hawaiian hull, as it has significant vee fore and aft, with a small vee amidships. Gary designed it this way because it would track better when sailing. The only down side of this modification is that when surfing steep waves, if it gets turned a little across the wave, there'll be no rescuing. It will round up parallel to the wave and "huli" (flip over sideways) if the wave is breaking. This canoe will probably do everything but surf better than a classic hull.
While I'm on the subject of outriggers, I'll be ready to work on my iako in a week or so. I've only tried laminating once before when I made the stems, and they didn't want to stay the shape I bent them to, even after gluing up on the forms. The curve was minimal, and I was able to pull them into shape on the stem molds and hold them with screws. If this happens with my iako, the amas won't be at the right height relative to the waterline of the hull. How do I make the laminated bends hold their shape? Do I have to bend each laminate to exact shape first (which I don't think I could do), or is there some other trick? I'll be using 13ft 1/4" strips of mahogony with a single 13 ft strip of maple in the center of the 7 board layup, so I'll have a good bit invested in the material, not to mention my time and angst. I'd like to get it right the first time.
Mahalo,
Kent
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Chris Ostlind
- Posts: 20
- Joined: Tue May 18, 2004 6:03 pm
- Location: Salt Lake City
iako layup
From my experience building curved laminates, there are several conditions that can distort the part.
Is the wood green or has it been kiln dried? Will you need to steam the material to get it to bend to the forms or can it be laid-up from dry stock? What grain orientations are you planning on using in the varous woods you have selected? Have you built-up a test piece to see how much return you will get from the part after it is removed from the lamination forms? Is your raw stock seasoned to the prevailing humidity conditions of your shop or did you recently bring it home from the lumberyard where the conditions could have been different? When you cut the laminating strips, does the wood stay pretty quiet or does it take off in a new direction indicating it has stored energy?
All these things can have an effect on the eventual shape of the part as it comes off the forms.
If you are trying to build two exact parts for your boat and have only one form on which to do it (and especially if you haven't done this before) I'd really try to do one as a test piece before pushing into the finished pieces. It's only a small amount of material and you'll learn a ton of good things as you do the lay-up.
Chris
Is the wood green or has it been kiln dried? Will you need to steam the material to get it to bend to the forms or can it be laid-up from dry stock? What grain orientations are you planning on using in the varous woods you have selected? Have you built-up a test piece to see how much return you will get from the part after it is removed from the lamination forms? Is your raw stock seasoned to the prevailing humidity conditions of your shop or did you recently bring it home from the lumberyard where the conditions could have been different? When you cut the laminating strips, does the wood stay pretty quiet or does it take off in a new direction indicating it has stored energy?
All these things can have an effect on the eventual shape of the part as it comes off the forms.
If you are trying to build two exact parts for your boat and have only one form on which to do it (and especially if you haven't done this before) I'd really try to do one as a test piece before pushing into the finished pieces. It's only a small amount of material and you'll learn a ton of good things as you do the lay-up.
Chris
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Todd Bradshaw
- Posts: 92
- Joined: Tue May 11, 2004 8:16 pm
As far as I know, the process would either be overcorrecting to allow for springback as one would do with steambending or using a lot of layers in the lamination. Figuring and predicting springback would probably require building a couple prototypes to measure before trying the real thing, which isn't very cost effective. I'd go with as many laminations as possible and would think seven should be enough. If you later find that it didn't hold it's shape, it would logically be because it didn't stay bent enough and you could always add some extra layers at the outboard ends on the bottom to get the right amount of drop and fair it into a reasonable shape.
I wonder how much stronger and stiffer the beams would be with mahogany inside and a maple top and bottom. Stiffness and strength gained from using a non-compressable core with stronger laminations on the outside surfaces should sound familiar...it's how stripper hulls are built. Think of the difference between a hull made with a central fiberglass layer, sandwiched between two 1/8" thick layers of cedar and one built from 1/4" cedar with a layer of glass on both sides.... Putting the maple in the center may increase the breakage or tear strength of the beam somewhat, but probably won't do much to help it keep it's shape or resist flexing. It would take somebody who knows more about engineering than I do to say what the strength/stiffness difference would be, but I suspect it might be substantial as long as you can maintain sheer strength between laminations.
I wonder how much stronger and stiffer the beams would be with mahogany inside and a maple top and bottom. Stiffness and strength gained from using a non-compressable core with stronger laminations on the outside surfaces should sound familiar...it's how stripper hulls are built. Think of the difference between a hull made with a central fiberglass layer, sandwiched between two 1/8" thick layers of cedar and one built from 1/4" cedar with a layer of glass on both sides.... Putting the maple in the center may increase the breakage or tear strength of the beam somewhat, but probably won't do much to help it keep it's shape or resist flexing. It would take somebody who knows more about engineering than I do to say what the strength/stiffness difference would be, but I suspect it might be substantial as long as you can maintain sheer strength between laminations.
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Gary Dierking
laminating iakos
The standard iakos in the plans spring back about 1/2" when the clamps are removed. Since the timber I use is similar to spruce and isn't as stiff as what you're using, I suspect you'll get more springback but I don't know how much. Your layers are thinner so that may compensate. Just layout the clamping blocks for a bit tighter curve than you want and go for it. If after a lot of sailing you decide you'd like the amas higher, you can shim up the whole assembly like they do on the OC6's.
I agree with Todd on the maple. I'd put it on the top compressive side.
I agree with Todd on the maple. I'd put it on the top compressive side.
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KARKAUAI
- Posts: 362
- Joined: Sat May 08, 2004 3:06 pm
- Location: Hickory, NC / Princeville, Kauai, HI
- Contact:
Great replies, guys. Gary, I didn't know you followed this forum...great resource, huh?
Guess I'll do a test piece of the single-ama iako first, using a couple of maple strips top and bottom...wonder if 1/8" would be enough? Would you lay up the whole double ama iako at the same time, or could I bend one side, then flip the iako over and do the other side on the same form?...Guess it'd be hard to glue the second half, huh? How about gluing up the top 1/2 of the laminates first, then seeing how much spring back I have and trying to compensate when gluing up the bottom half?
Mahalo,
Kent
Guess I'll do a test piece of the single-ama iako first, using a couple of maple strips top and bottom...wonder if 1/8" would be enough? Would you lay up the whole double ama iako at the same time, or could I bend one side, then flip the iako over and do the other side on the same form?...Guess it'd be hard to glue the second half, huh? How about gluing up the top 1/2 of the laminates first, then seeing how much spring back I have and trying to compensate when gluing up the bottom half?
Mahalo,
Kent
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Gary Dierking
laminating iakos
I vote for doing it all in one shot. I think that you'll get less springback if you do them all at once. Use protective scraps of wood where you clamp to avoid denting the outside.
I usually knock the hardened glue off with an 8" foam pad disc sander and then run it through a thickness planer. Rout the edges and you're done.
I usually knock the hardened glue off with an 8" foam pad disc sander and then run it through a thickness planer. Rout the edges and you're done.