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High Aspect Bermuda vs Batwing


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I have a canoe based trimaran.  Basically just a canoe with outriggers.

I have been using a simple 27 sq ft sprit rig.  Works fine.  Sail down wind/reaching, upwind take the rig down, put it in the bottom of the boat and paddle.  Current leeboard is a sabbot daggerboard on a pivot pin.

I want to improve upwind performance, it's never going to be a keel boat or even a dinghy.   But it has other assets, namely that it can be easily portaged and car topped.

I have pretty much decided I am getting rid of the stubby ply sabbot dagger board and cutting a 4 ft deep pivoting lee board out of hardwood on the band saw.

The rig, I am staying cat rigged.  But I am divided between a somewhat lower aspect 36 sq ft batwing sail and a higher aspect Bermuda rig.  Both sails will reef.

Figure the batwing will be a better reaching sail but the Bermuda will give better upwind performance, which is really the end goal.

Sound about right?

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The higher aspect sail should be a bit better upwind, but really it's a trimacanoe, not a 12 meter.  My gut says the bermuda sail should be better on a reach too, but I may be wrong on that.  One thing that's worth considering for sure is whether the higher center of effort of the bermuda sail will put too much strain on your outrigger connections.  Given the sail size, probably not an issue, but moving the CE higher certainly will have an effect on needed righting moment and could strain the outriggers or your hiking abilities  in some breeze if they're not solid.

Any pictures?  I built a sailing rig for a sit on top kayak in high school that had similar goals - paddle upwind, reach and run under sail.  No outriggers, and capsized a lot when reaching because of it!

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Sprit.thumb.jpg.cbffdaef823e4bb2f82e2b8dadd9a3e6.jpgRight.  I should do the calculations on how much increasing the centre of effort will increase the heeling moment in 5 knot intervals.  Good point.  I only get about 165 ft pounds maximum righting moment from my outriggers.   

Yes, here is a pic with the sprit rig.  Nothing fancy.

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Have you read this book? It has guidelines for just about any type of sail you might want to try on a canoe. It includes some preliminary sailplans in the appendix -- including some not-so-antique ones as you might expect from the title.
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Lower aspect ratio. Do not increase the righting moment, and do not move the center of effort up. Frankly I think you would be uninmpressed with improvements. There's really no great advantage here to going to a new rig. Your hydrodynamics (the amas) suck. And structurally, you don't have anything that can scale up on the loads that come with a deeper board along with a taller rig.

Batwings are cool old canoe rigs. If you want to build one, enjoy it. But do note that the sprt rig can have really good shape on port tack. The traditional batwing has poor shape (but a modern battened square top would have great aero).

The practice is more important than the theory. Getting whatever rig you do trimmed right is the key.

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I'm thinking your upwind performance has more to do with underwater forms/features and balance than the shape of your sail. 

 

I believe getting your leeboard right is going to have more impact than the type of sail. 

If your center of effort on the sail is forward of the center of effort underwater you will never get upwind .

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Okay.  That's good feed back.  This is why I asked before spending any money.

Reinforcing for a stronger leeboard attachment shouldn't be a problem.  These Grummans are pretty solid boats.  This was originally a sailing model, still has the factory mast step etc.  The factory rig that came with these boats originally was a fairly tall 65 square foot Gunter rig.

 

Outriggers.  maybe I should do something about them to make them a bit more useful from a hydrodynamics perspective.  I have some plans I bought, I think from Michael Storer, but these were just so easy and they do work kind of well.    But I have seen some with kind of an asymetric shape to them so they help with performance.

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21 minutes ago, TBW said:

Okay.  That's good feed back.  This is why I asked before spending any money.

Reinforcing for a stronger leeboard attachment shouldn't be a problem.  These Grummans are pretty solid boats.  This was originally a sailing model, still has the factory mast step etc.  The factory rig that came with these boats originally was a fairly tall 65 square foot Gunter rig.

 

Outriggers.  maybe I should do something about them to make them a bit more useful from a hydrodynamics perspective.  I have some plans I bought, I think from Michael Storer, but these were just so easy and they do work kind of well.    But I have seen some with kind of an asymetric shape to them so they help with performance.

Length is the most important thing. Those short stubby things create lots of wave drag. The amas should be nearly as long as the hull--if you really want to sail upwind fast. But once you start doing that, all the loads start to go up everywhere and you need to reexamine every detail--the attachment of the akas for isstance.

Make the amas really long and skinny and not too buoyant. That way you limit how hard you can press her. Make the total volume of the ama something like 50% or less of the total displacement of the loaded canoe with you. That way you can only press her so hard before the ama goes under and you capsize and start over :-D

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Max speed isn't my goal- I have a both a beach cat and a dinghy for catching a rush.

This is a camping boat.  Places like Kilarney, Algonquin, the Everglades.  Load up with a weeks worth of gear and head out sailing.  Goal would be consistent progress more than speed.  I am happy if this boat can carry, me, my dog, a cooler, bunch of beer and a tent along at a consistent 2-3 knots.  Of course surfing down waves at 5 or 6 would be a hoot, but not really my goal :)

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ACA Open Sailing Canoes have 45 ft^2 lateen rigs.  An Optimist rig would work perfectly and Optimist sails are just about the most highly developed sprit rig.

 Unless you have some aversion to shifting your ass, why have outriggers at all?  The best way to improve performance is to take the training wheels off. A subset  above mentioned ACA Canoes are raced without rudders, which means the sailor more or less lies back on the high side of inside the canoe.  A single well shaped leeboards about 8 “ forward of mid beam and these boats will go upwind reasonably well. The Grumman is a pretty stable canoe, certainly a lot wider at the waterline than what the racers sail.  The ACA C Class has  55 ft^2 rig which can be full battened and square headed.  

Sailing Canoes show up at Sugar Island off Gananoque each summer for a week usually straddling the end of July beginning of August.  A field trip might be informative.

SHC

 

 

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Why outriggers?  Because neither my dog nor my 2 year old sit very still.   The baby in particular is up and down like a Jack in the box, I can balance a boat out fine solo or with another adult, or even an older child, but the whole family dynamic makes it tricky, and dumping a canoe with 2 kids, a dog and a load of camping gear is total bull shit I would rather avoid.  Like I said, this is a back country camping boat with a sail.  Outriggers make dumping with a load of camping gear unlikely.

Sugar Island is my backyard though, so I may check it out.  

I have seen my fair share of back country sailing canoes in adventure races and I see very few using those ACA rigs as back country rigs.  It's BSDs and Falcons for the most part.  Most BSD sailors seem to use outriggers, so I know I am not alone in wanting a stable boat for exploring.

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On 11/26/2020 at 7:58 PM, TBW said:

Would like a copy, but $100 used seems a bit steep

I see it for less than half that $CDN on Amazon(dot)ca... if that's still an issue, drop a hint to a significant other for a gift to put under the Festivus tree.
I strongly recommend it. My copy was also a gift from SWMBO! It also has calcs for determining centre of effort, leeboard designs.

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Looking at your rig I honestly believe you need a boom to get the sail as flat as possible as  more camber in the sail equates to more sideways force. This is going to make pointing impossible as the leeboard will not be able to handle the loads.

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6 hours ago, Major Tom said:

Looking at your rig I honestly believe you need a boom to get the sail as flat as possible as  more camber in the sail equates to more sideways force. This is going to make pointing impossible as the leeboard will not be able to handle the loads.

I went loose footed sonI didn't have to worry about the kids getting smoked by the boom.

I am thinking a slightly smaller higher aspect rig I can mount aft of the front seat.  Then a boom won't be as problematic.

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If you go on the Woodenboat Forum and post, A question for the sail makers... or similar...Todd Bradshaw will likely appear, the author of the above book.  He is a presence on the Forum and a wealth of knowledge.  Do not bring a knife to a gun fight it you want to dispute his advice.  He has helped many amateur sailmakers.  

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