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meester

CS15 with a lug yawl rig

95 posts in this topic

Pardon me while I geek out on this topic.  

 

I used to work with some materials scientists, and they think about material strength in at least a couple of different ways.   First off there's what they call "yield stress," which is the amount of force (per area) that a material will hold before it starts to deform.   Think  load ratings on lines, etc.

 

Another way that they think about materials strength is what they call "toughness," which is something like the amount of energy something can absorb before it breaks.  It's kind of like the opposite of brittleness.

 

Take glass for example.  Glass is actually pretty strong stuff, but it's brittle.    In plate glass, even a small scratch can get a crack going, and you can snap it easily.  Strength, but no toughness.   On the other hand, if you make bundles of glass fibers, you get fiberglass, which is really tough.  Broken fiberglass is typically mangled and splintered, and a lot of energy goes into making these extra cracks. The polymer resin also gets mangled and that absorbs a lot of energy.  

 

Rope, brass, whatever.  In the end, it probably doesn't matter if it's not a safety issue.   For me, I chose the rope trick because I had the materials on hand, and I had good examples to follow.

 

Thrillsbe,  if the salty brass makes you feel good, or if you will worry about the rope taking damage while you are sailing, then stick with the brass.  I say the purpose of the boat is to give you pleasure, and the purpose of boat building is that you get to make these little decisions to suit you.  If you don't like the result, you get to mess about with your boat some more, and fix it the way you like.

 

Bob

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I'm going ahead with the rope for the rudder.  My c/b will have a gob of lead on the bottom leading edge, so I think I'm OK there.  I have been toying with the idea of making a second blade with a brass leading edge, because I, too, have those materials on hand.  Might be an interesting science project-- later on.  Right now I'm trying to get done by the Mess-about!

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I've done dozens of boards with a rope leading edge, none have ever seen major, unrepairable damage, in spite of multiple strikes. One even fell out of the case on the road once (a centerboard lanyard parted). It was ground down pretty good and the board's pin was bent a bit, but the rope did it's job and the repair was as simple as packing in some thickened goo and fairing it back in. It's also a lot easier to install, compared to bending a brass strip, which also needs to be drilled and countersunk for fasteners. Lastly, brass isn't very strong, is quite soft and not well suited at all in salt or brackish water.

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  • I love the rope trick - it's probably my my useful decision on Rocinante.  I use my centerboard as a depth finder all the time, and the kick-up rudder as a "no foolin' it's really shallow" idiot light.  This is over some pretty rocky bottoms, too.  And they have taken very little wear in spite of this abuse.  And so easy to make and repair.

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Hi Bob,

 

post-814-0-04227500-1438752742_thumb.jpg

 

This is one of Michael Storers balanced lug rigs on one of Grahams "Flyfishers" the trick it seems on making the rig very manageable when it blows a bit is to have lots of downhaul tension on the boom, enough that the yard has a couple of inches of curve at the ends. As Lynn said, Storers website has a wealth of information on making balanced lugs work well.

 

Best to all, Steve

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I'm not any expert, but there is a lot of info out there on the web.  Mik Storer's site is a great place to start.   (See an earlier post in this thread.)  There are so many adjustments that you can make on a lug, I feel like I can make up for small mistakes in my design.  On the other hand, every adjustment is a way to get things wrong.   :wacko:   I expect to have a long period of tweaking after the splash.

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I have a friend who is about to go this route with a Spindrift 10.  Any words of advice for him?

 

I tried more than a few ways to make a balanced lug rig work on my Spindrift 10 and couldn't. What I did manage was a standing lug similar to what is used on B&B's Amanda design. The problem with the balanced lug on the Spindrift is in the stock mast step position, it moves the center of effort of the sail too far forward. A standing lug gets it about right.

 

The benefit of the lug, as I see it, is a sail that can be raised and more importantly doused or lowered while on the water, and can also be reefed if need be. I also got to try it recently and found it performs really well. I doubt it would compete head to head with the standard cat rig, but for knocking around, but I was pleased to see it points well and was cooking along pretty well on most points of sail. I know it was pointing better and had less leeway than a leg of mutton sail I tried.

 

On mine, I have managed to graft this lug sail to the stock rigging pretty easy. For the mast, simply use the bottom two of the three aluminum mast sections and you can use the stock boom with fixed gooseneck. You tension the luff with the halyard, same as on the stock sail. You can also use the same main sheet and vang positions on the stock boom and could probably even use the same jiffy reefing setup.

 

Option B is to build a different boom using gaff jaws to simplify the setup and instead of the reefing lines, use that third line position as a downhaul on the boom to tension the luff. You  would still need the vang to control the twist.

 

Anyway, I tried it and like it. While I still have the designed cat rig and sail, I suspect the standing lug will be what I use most of the time. Unless you are racing against the designed cat rig, I don't see any downside.

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BTW, there is more to these lug rigs than just sail shape. The overalls shape and size of the boom and gaff is also important. The flex in the gaff and boom is used to tension the corners of the sail to get the shape right, so these have to be designed and built to the spec of the sail. In operation, the gaff and boom are loaded like a leaf spring and are a big part of the performance. That isn't mentioned in most places, but appears to be a critical part of the success with these.

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Hi Howard.  

 

Nice to see that the new rig is working out for you.      I guess that when Thrillsbe asked for advice for his friend I should have mentioned doing the sail area math to get the center of effort close to where it should be.  

 

Here are a couple of links that I found useful:  

http://www.duckworksbbs.com/sails/custom/sail_area.

http://reallysimplesails.com/using-really-simple-sails-on-other-boats-advice-and-dimensions/

 

Bob

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Hi  All,

 

What type of wood do you recommend for the keel batten on the CS15?   Graham's plans suggest fir or mahogany.  On the other hand, the keel batten looks like regular yellow pine in Alan's videos.

 

I got a lot done today including doing the butt joints on the hull panels, ripping stringers for the seats, building my temp. center frame and some of the cradle.  Whew!  It's cool to see these actual boat-shaped pieces of wood coming together.

 

Bob

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I did use yellow pine on the keel batten on the 15 in the videos. All the solid wood is yellow pine for that matter. Whatever you use, make sure you use enough thickened epoxy when you install it. Any air gaps can eventually rot.

 

I actually tore the rotted out keel batten out of my CS 17 recently and replaced it with heavy fiberglass tape. I think the keel batten gives the keel a lot of nice rigidity but I know Graham has always been uneasy when it comes to using big pieces of solid wood in an epoxy encapsulated boat. 

 

I suggest coating the piece of wood you shape for the keel batten with 3 coats of epoxy (at least the bottom of it) before installing it in the boat. That will ensure that if you don't get 100% void free glue up, all will be well. 

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My keel batten has been sanded down for the part aft of the trunk, and I'm laying several layers of glass on top... To much wear on that area, and worried the board would rot.

 

For the keel, the small part that had damage due to being pulled on a tow truck, and even after repairs got wet. This was cut out, and a new piece of wood was carefully scarfed in glassed, with half round SS on top of that. Other then that the keel batten and keel in my CS are holding up amazingly.

 

There is a CS20 in Denver with a cat ketch, lug rig. I noticed he really had to upgrade the masts to make it work.

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Thanks, Alan.   It makes good sense to do a little more rot protection in the wettest part of the boat.  I'll pay close attention to the end grain too.

 

Ed, I think you raise a good point about wear.  I can see that sandy feet and gear might scratch through to the raw wood.  

 

How about if I cover the keel batten with a layer of glass for extra protection, unpainted so that I can see if things are going bad?   I'd like to have some wood accents showing here and there.  The  boat will be stored in a garage, so UV damage won't be dramatic.

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Alan, Great suggestion about coating the keel batten before installation. And now I understand the reasoning behind elimination of the wood batten in favor of a "putty" and fiberglass lay-up as called for in the Mk-3 plans.

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I have a friend who is about to go this route with a Spindrift 10.  Any words of advice for him?

 

I tried more than a few ways to make a balanced lug rig work on my Spindrift 10 and couldn't. What I did manage was a standing lug similar to what is used on B&B's Amanda design. The problem with the balanced lug on the Spindrift is in the stock mast step position, it moves the center of effort of the sail too far forward. A standing lug gets it about right.

 

The benefit of the lug, as I see it, is a sail that can be raised and more importantly doused or lowered while on the water, and can also be reefed if need be. I also got to try it recently and found it performs really well. I doubt it would compete head to head with the standard cat rig, but for knocking around, but I was pleased to see it points well and was cooking along pretty well on most points of sail. I know it was pointing better and had less leeway than a leg of mutton sail I tried.

 

On mine, I have managed to graft this lug sail to the stock rigging pretty easy. For the mast, simply use the bottom two of the three aluminum mast sections and you can use the stock boom with fixed gooseneck. You tension the luff with the halyard, same as on the stock sail. You can also use the same main sheet and vang positions on the stock boom and could probably even use the same jiffy reefing setup.

 

Option B is to build a different boom using gaff jaws to simplify the setup and instead of the reefing lines, use that third line position as a downhaul on the boom to tension the luff. You  would still need the vang to control the twist.

 

Anyway, I tried it and like it. While I still have the designed cat rig and sail, I suspect the standing lug will be what I use most of the time. Unless you are racing against the designed cat rig, I don't see any downside.

 

That is what I want to do to my 11N. I like the performance of the stock rig, but I want to make it easier to go from rowboat to motor boat to sailboat. At the wooden boat festival in Mystic earlier, I saw other boats with this rig. The mast and spars were just laying all in a bunch and they were going away in a minute or two. There is a three legged race at MASCF and I'd like to enter it. It seems with a yoke like that you could slip the whole rig off to one side to row, and have it up quickly. Am I correct?  Is there a good book to follow design of a rig like this?

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