Jumat, 29 Januari 2010

Yawl should know the conundrum of getting a tiller 'round the mizzen mast

The details of how to design a yawl so that the tiller gets around the mizzen is an interesting topic. There are a number of tricks:

Using a line steering system: Here you can see Michael Storer's Beth Sailing Canoe with the tiller forward of the mizzen and the lines connecting to the rudder, which is out of the picture.


I'll add that there are a number of ways to do line steering. My Deblois Street Dory has line steering coming into the boat from a rudder yoke but there is not a remote tiller as in Beth. The Coquina is another example of line steering in which lines are attached directly to the rudder and pass through the transom, via a pulley system, and the steering line goes around the perimeter of the boat.

Using a long push-pull tiller: Here you can see James McMullen's Oughtred's double ender.


Using a curved, laminated tiller or split tiller


Using a normal tiller with an offset mizzen




For the Goat Island Skiff, we go with an offset tiller as in this model by a customer:




The other methods I mentioned just won't fit the situation we have in the Goat Island Skiff, mainly because there is not room for a split tiller and we want to keep the solution simple. We are deciding about just how much to offset the tiller. You can see above that the tiller will hit the mizzen before 45-degrees. The big question is how much room do we want to give the tiller to swing. In the pictures, we decided to test a 45-degree swing. That puts the mizzen a little further off the centerline than I'd like. This boat is very light and pushing a tiller than hard over makes the rudder act like a brake and the risk of losing so much speed that you can't get through the tack is something to consider. Then again, we don't need it so close that things feel claustrophobic. In the picture above of the offset mizzen, notice how little offset the mast is...the tiller must touch the mizzen pretty early. Does that give enough steerage for the helmsman when the push the tiller in the mizzen direction?

We'll have a solution soon after a full-scale mock up. The way we are doing this, collaboratively, is something I do on many projects. It always gets a better result because many thoughts and ideas can be sifted through. The more the merrier. Whatever the solution I draw up, the mizzen can always be moved a little more or less off the centerline according to the skippers preference. The important thing is to maintain the rake of the mizzen, which has been determined. My point is, that collaboration with designers, customers, and other folks with experience through the forums and boat shows can be an advantage in getting many thoughts onto the table and generating the best solution.

Senin, 25 Januari 2010

Great Boatbuilding Article



NY Times has a great article in its Preoccupations editorial about a writer who builds boats for fun and "describes his work on boats as a 'postgrad seminar in character-building". Please visit my links page to see this wonderful article as well as other good links.

"Building a boat offers no paycheck,
but teaches much about the values of work"

quoted from

"Finding an Answer To Rough Seas" by Lawrence W. Cheek

Jumat, 22 Januari 2010

How do you determine the number and dimensions of staves in a Bird's Mouth Mast or Spar?



Birdsmouth is the word in the shop, lately. We have several orders for birdsmouth masts and spars that are in progress. I have been working hard at nailing down the process to be able to make them efficiently and to a very high standard and feel very excited about how it is all going. The Landing School of Boatbuilding has asked me to to give a talk/demo on making things birdsmouth style, so I've been pressed to improve our webpage on birdsmouth spars as well. On the page is my procedure for determining the number and dimensions of staves in a birdsmouth spar. Gaeten Jette, a featured contributer to Duckworks magazine on the topic of Bird's Mouth Spars, generously helped me customize the online calculator for my use and students' use. I hope you find it helpful, too.

We make two styles of Birdsmouth spar, using symmetrical staves (most common) and asymmetrical staves, which when done correctly will yield a perfect octagon and a spar that is slightly stronger and quicker to make. I decided to apply this type to making an ultralight kayak paddle shaft.



I am pleased with the results. The biggest hold up was fitting the plugs in the scoops that will take a ply-composite or a carbon fiber blade, which is already something we produce for our wood/composite, high performance oars.

With that part of the process ironed out it really is just a matter of setting up the operation to produce these paddles after some testing. This one will go to some paddler friends who will take the design on the seas and really test it out. Hopefully, sometime this summer the results will come in and production will begin. I'll leave you with the best part of making new things: breaking them with a hammer. We test most spars this way to make sure that things break the "right" way. That is, in a proper glued structure, the wood should always break before the glue joint does, otherwise there is a problem. Happily, all our spars have been breaking the "right way" in the shop so we know they won't break out on the water.

Selasa, 05 Januari 2010

Why the Yawl Rig for the Goat Island Skiff or for any boat?


I am asked this a lot and wanted to put something together to answer this and other questions. I added the mizzen to the GIS because I wanted a boat for myself that would be easier to singlehand on longer excursions and for use in sail-and-oar events such as the Small Reach Regatta, the Texas 200, and other RAID events like the Shipyard School Raid and Sail Caledonia. Many, many of the boats you see in these events have a mizzen.

For my own use of the GIS, a mizzen is needed for a variety of reasons:

1) to hold the boat into the wind while the sail is raised, lowered, or reefed while singlehanding or sailing with my kids.
2) to hold the boat into the wind while rig is unstepped and stowed and oars are rigged for rowing
3) to be able to hold the boat to windward or to heave-to while underway for taking short breaks to move people, re-stow gear, or go to the bathroom with out getting blown off course.
4) to be able to back off docks and beaches and control steering in tight spaces
5) to be able to 'tune' the weather helm felt by the helmsman by trimming the mizzen

Other FAQ's

Is the designer aware of your changes to the Goat Island Skiff?
Yes, I have a great working relationship with Michael Storer whom I consider a friend. He and I correspond often and he has OK-ed the addition of the mizzen and trusts that I will design and build the new rig so that it fits in with the concept of the GIS. For example, all pains will be taken so that this addition adds very little weight to the boat. The mizzen mast will be a lightweight, birdsmouth mast.

Is the lug sail the same and is it stepped in the same place or how has the lug's position been adjusted for the new mizzen?
I have designed new sail rigs for boats before, for dories actually. After drawing the new rig, finding the new center of effort (CE) of the added sail area, and moving things around, the new CE and old CE are in the same place such that the centerboard does not need to be changed. In the GIS, the lug is the same standard sail (105 SF) and it will step in a secondary partner/step forward of bulkhead #1. It turned out that the lug needs to be moved forward only 9" keeping things tied into the bulkheads for structural integrity and simplicity. The original mast step is retained so the boat can be sailed with or without the mizzen. The GIS Yawl is is still the usual standard GIS, but with an added mizzen. You can take the boat out with more flexibility in rig choice.

Has one been built and how well does it work?
I expect to have a GIS Yawl on the water this summer, my personal boat, but orders for sail rigs and boat kits may prevent that from happening. However, one kit is going to a customer who will be doing the yawl and plans to be sailing this summer in the Texas 200. I have no doubt that the boat will go as well as the standard, upwind and downwind, but with the added benefits of the mizzen for RAIDs and sail0and-oar type of use. If the mizzen is not needed, leave it ashore and use the Goat as the standard lug-only arrangement.

You can learn more about How to Use the Yawl Rig in my blog post.

or the Goat Island Skiff page on my website.