hinged mast

[Captphil24]

I am going to help a friend repair and step a broken mast. I would like to investigate the possible design of a mast hinged in the center to allow passage under a bridge. Any ideas would be welcome.
Phil in FL

[knothead]

Originally Posted by Captphil24

I am going to help a friend repair and step a broken mast. I would like to investigate the possible design of a mast hinged in the center to allow passage under a bridge. Any ideas would be welcome.
Phil in FL

Phil, Hi, How big is the boat?
Could use a little more info.

[sailingdog]

It really depends on the size of the boat, but considering that you asking about passing under bridges, I am guessing this is considerably bigger than a sailing dinghy.

However, if you mean hinging the mast in the center of the spar, when you say "Hinging a mast in the center," you're either mad or a complete idiot. JMHO.

Generally, the loads on a mast are generally such that you don't want a weak point in the center of the spar. Also making such a hinged point would add quite a bit of weight aloft, if the point were to be strong enough to take the loads experienced by a spar.

Most setups that allow you to drop the mast on the water involve using a tabernacle setup or a hinge point at the mast step. Generally, a mast step-type hinge is limited to smaller boats, due to the size and weight of the spar.

My boat, which has a 35' 6" mast, has a mast lowering system, but the spar is lowered as a whole, using a series of A-frames instead. I can lower or raise the mast using a single control line. The process can be stopped at any point and reversed at any point if need be.

[sce56]

I'm looking to buy a 30ft Hunter sloop 1978, and have access to a slip at a friends house for free the only problem is I have to go under a bridge to get there and I think the mast will be to tall at low tide to make the passage. I believe this boat has a 45ft mast and is on a tabernacle mount. Will this solve the bridge problem in fact do away with the low tide problem? Thanks for your advice. Rick in California.

[KeelHaulin]

A 45ft mast is a big mast to tabernacle; not sure what you would have to do but it probably could be rigged to raise/lower. I have seen boats lower their mast via a cable winch that attaches to the backstay (IIRC) but not sure if that was the procedure because I was watching from the dock.

If you are serious about doing this I would search for a rigger in the Santa Cruz area who has done it before. The north section of the harbor at SC is blocked by a fixed bridge and sailboats that are berthed there are required to lower/raise their mast to get through. Several 20-30 ft sailboats are rigged to go under the bridge because the wait to get a slip in the south section of the harbor is ~20 years or so.

[feetup]

Captphil;
While I don't agree with Sailingdog's assessment of your mental state I do agree that the physics of a mast hinged in the center are pretty much insurmountable in your case. A stayed mast is under a surprising amount of compression, or to put it another way, the rig is trying to make the mast shorter. Brian Toss gives an analogy of taking an uncooked piece of spaghetti and pushing the ends together. It doesn't take much force to cause it to break in the middle. Obviously a joint of any kind would have to be at least as strong as the rest of the mast, a daunting task to design, and it would be very heavy, placing all that weight well above the waterline where it will have the most affect on stability.
Mounting the mast on a tabernacle will allow it to be lowered and raised and the ease with which that is done is totally dependant on the way it is rigged. The design of the rig (masthead or fractional) location and length of the chain plates, the arraignment of the lowers, the rigging of the forestay and backstay and the arrangement of the running rigging are just a few of the factors that will affect the ease or lack thereof of lowering your mast.
It is not impossible, and has been done very well many times, but it will take a bit of study and planning to make it work well. One of the hardest parts is the ability to keep, or at least be able to re-create the tune of the rig after lowering and raising the mast.
Check out your local library and look through the book sellers for books on rigging. Check out other boats with tabernacle stepped masts and if possible talk to the owners. Do a few Google searches on the topic. Then when you have some working knowledge of the topic and still decide to go ahead the questions you ask here will be much more specific and easier for the pundits on this form to answer knowledgeably.

Feetup

[Lion35]

As Keelhauling mentioned Santa Cruz has a large population of tabernacled rigs because of the bridge disecting the harbor. A 45' rig is at the upper limits of what is normally tabernacled here, but it is done on rigs this tall. If you have a rigid roller furler the task is much more complicated.

sce56, if you already have a tabernacle base you've got the hardest part done. On a rig that size you'll want an electric winch, smaller rigs generally use the main sheet to lower the mast.

As Feetup mentions specific questions will be much easier to answer but here's a very generalized synopsis of how it is normally done.

* add pivot the upper shrouds in line with the mast pivot point
* add pelican hooks or another quick release to the aft lowers if you have them (these are not your normal pelican hooks, they are custom made and large enough to take the shroud load)
* Make a bridle to stay the boom end to the shroud pivots and then back to the primary winches. This holds the boom center line and stays the upper shrouds at the pivot point.
* Add method to connect the back stay to the boom end.
* Add a quick release to the back stay

You then use the winch or the main sheet attached to the boom end to lower and rase the mast.

There's a rigger here in Santa Cruz who has extensive experience in tabernacling boats, but in a sign of the times, he was sued and no longer rigs tabernacles, but I believe Ballenger Spars still makes the pelican hooks.

Hope this helps.

[Captphil24]

Originally Posted by feetup

Captphil;
While I don't agree with Sailingdog's assessment of your mental state I do agree that the physics of a mast hinged in the center are pretty much insurmountable in your case. A stayed mast is under a surprising amount of compression, or to put it another way, the rig is trying to make the mast shorter. Feetup

Let's expand this discussion: The current mast is from a 36 ft sloop. The current mast is broken in the center. The break is at the spreader connection point. My friend is planning on splicing the mast as a repair. I always believed that the main force on the mast was one of compression and that a good splice with a 3 ft fitted core might work just fine. Just wanted to explore the possibility of putting a hinge at that point. So far I have not found a design that would fit this problem. Since the mast will be stayed at this point with short fore and aft stays; seems that you could engineer a fore aft hinge just above this spreader connection. Might require a couple of side ss steel vertical plates. Remember: no balls no blue chips. lol

[knothead]

Originally Posted by Captphil24

Let's expand this discussion: The current mast is from a 36 ft sloop. The current mast is broken in the center. The break is at the spreader connection point. My friend is planning on splicing the mast as a repair. I always believed that the main force on the mast was one of compression and that a good splice with a 3 ft fitted core might work just fine. Just wanted to explore the possibility of putting a hinge at that point. So far I have not found a design that would fit this problem. Since the mast will be stayed at this point with short fore and aft stays; seems that you could engineer a fore aft hinge just above this spreader connection. Might require a couple of side ss steel vertical plates. Remember: no balls no blue chips. lol

A splice at that location would be fine.
A hinge is not practical.

[knothead]

Captphil24 Please don't get me wrong. I admire your "thinking outside the box".
I didn't mean to come off as being short.
Your idea would probably be achievable but prohibitively expensive.