BYYB Forums

Fellow boat builders, I am ready to assemble my mast. Any comments on the hinge as in the plans vs. side plates and pins. What size  plates and pins are reccomended?  Thanks Jim Stewart

Jim:  The biggest problem with the mast, mastbox and hinge system in the stock plans is the chance for rot.  Water WILL get into the mast box and ultimately lead to rot.  I prefer the tabernacle system Ryerson Clark used on his Weekender.  I used the same setup for my boat.  No chance for water entry'

Dave

Dave, Could you please explain that system. Thanks, Herschel

Greetings Herschel,

Read this ... http://www.byyb.org/forum/index.php?topi...4#msg24234

which contains theses links, which you must also read ...

  http://www.byyb.org/forum/index.php?topic=2385.0

  http://www.byyb.org/forum/index.php?topi...n#msg18894  (includes drawings)

  http://www.byyb.org/forum/index.php?topic=1780.15



Photos from http://ryersonclark.com/Site_3/Weekender..._Blog.html ...










And my favorite $1,500 tabernacle from Marshal Marine ...

[img width=200]http://home.comcast.net/~TomsWeekender/byyb/MarshalMarine/11_Tabernacle1a.jpg[/img] [img width=200]http://home.comcast.net/~TomsWeekender/byyb/MarshalMarine/12_Tabernacle2a.jpg[/img] [img width=200]http://home.comcast.net/~TomsWeekender/byyb/MarshalMarine/13_Tabernacle3a.jpg[/img]

... which unfortunately only works with aluminum masts, but it solves the mast hoops not fitting over the tabernacle problem ...




And a really good image of a traditional Tabernacle minus the mast from the most meticulous boat builder on the planet ...



If you look closely, you will see

1. the hinge pin that the mast pivots on
   
2. the cross piece that helps limits the forward motion of the mast until the rigging gets snugged up
   
3. the bottom brass plate to take the compression load from the heel of the mast and transfer it below decks
   

And a backside view of another tabernacle from a different Sano masterpiece ..



http://sanomagic.world.coocan.jp


And another instance of small boat tabernacle ... http://inlandpacket.blogspot.com/2011/07...lower.html



And another weekender ...



The above photo is instructive of the downside of the tabernacle. Notice that the boom is fixed below the tabernacle, the mast hoops are stranded on the mast above the tabernacle, and the gaff has been completely detached and is bungeed onto the boom.  So there is just a little more fiddling around to do with raising the sails as you have to decide what to do with the boom, hoops, and gaff.


Cheers,
Tom

I took a slightly different tack. 

Water doesn't get into the fore hatch because of it's design.  There is a raised lip around the hole, and the hatch cover fits over it. 

I built a smaller version for the hole the mast fits into, and ran the mast through the middle of this "hatch cover".  The "hatch cover" is epoxied to the mast.  In eleven years of use, I've never had any water get down into the mast box.

You can see a picture of it here: http://www.flickr.com/photos/58781034@N00/600712981/

Bill

I've had no problem with water in my mast box by just using a traditional mast boot.  I do tape the top of the boot to ensure water doesn't get in through there, but other than that, it is nothing special. 

I have had problems with the foreward mast hinge though.  With repeated raising and lowering the mast, the tabs that the pin runs through have begun to spread.  If you go with the standard strap hinge as in the plan, I recommend that you weld the tabs down.  I have done that on a new hinge and will install it in the spring.

Al

Hinges, like that spec'd for a Weekender are designed to take vertical loads. When placed horizontal, the pin hoops and the hinge itself tends to bend and misalign. I've never liked the idea, too many pieces, too many places for things to bend or move. A simple pivot pin is all I ever use. A nice hefty 1/2" or bigger bolt does a fine job, has no moving parts and is stout enough to tolerate what ever comes along.

I've done tabernacles in both metal and wood. Wood looks good, but is often bulky. Metal is physically less imposing, but requires some fabrication that many don't have skills or tools for.

Things to consider in a good tabernacle design are where to have the gooseneck. A good design will have the gooseneck low enough that a gaff and sail can ride on the crotched boom, even when the mast is down. This also means the mast is dependent on the tabernacle base for all of it's support. I dislike this method, but it does work and solves a few other problems. My preferred setup has the mast extend well down into the tabernacle and the heel rests on the deck or bottom plate of the tabernacle. I usually place a hunk of HDPE on the base or mast heel to absorb these compression loads. A sail track solves the problem of getting a sail to lay down with the boom. Hoops and gaskets (loops or lacing) usually have to stay with the mast, which can be odd (see above), but a sail track solves this easily and your sail sets better too. If the mast extends well below the pivot bolt, you can use a tackle to raise and lower the mast. You don't need to leave the cockpit if you have a winch of enough tackle. This is another reason I use this arrangement. My 23' ketch has this and I use a sheet winch to raise and lower the main. The main is 25' long and not easy to raise by hand, but I can grind on the winch and it goes up with little bother. If designing a tabernacle like this, consider the loads imposed on it during the raising and lowering operations (they're huge). It has to be stout, so metal is an option. The ketch's is made from 3/16" mild steel plate, that's been power coated. It's heavy and has some lightening holes cut in it, but it still bends a little during the first part of the raising operations. Lastly, consider how high the tabernacle will be over the deck. You can quickly run into problems with tree limbs and low bridges if you're not careful.

Shown is a wooden one for Rocky, which rests on a ring frame (bulkhead) so it doesn't have a compression post below. This is a typical tabernacle, note the distance between the pivot and the bottom of the mast. This offers mechanical advantage when raising it. It's also ridiculously over built, which they need to be if you power raise the mast, by attaching a line to the bottom of the mast and pulling like crazy. You see when you first pull on this line, there's 340 pounds (there about) to pull before the mast starts to raise. This goes down as it goes up, but the initial pull is a beast on the tabernacle. I use a gun tackle on the line which decreases the line pull to 113 pounds and I use a cordless drill on a 3:1 winch, which brings the load down to about 38 pounds on the drill motor.

Food for thought.