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Dale Niemann

Freely Rotating Masts within Tabernacles for CS 17 mk 3?

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18 hours ago, Dale Niemann said:

I like your idea William but it would seem to have a great amount of stress on the hinge.  It would have to be very strongly constructed. Do you have any drawings or more specific ideas.  With the typical unstayed mast they have a lot of flex.  It seems that the hinge would distort the bending.

What size is your mast?  Wood, Alum or carbon fiber?

This is just a rough model to illustrate, using the forward bulkhead and mast collar of the Spindrift as an example.

The assumption is that the green mast stub can rotate in the collar. The tabernacle is rigidly attached to the stub with through-bolts. Hinge bolt in red, locking pin blue. Shown here with mast 15deg from vertical and locking pin removed.

 

My own mast is ali, 63mm diameter, 3mm wall. I will be making the tabernacle out of Bulletwood. I am sure you are right regarding the flex, but I cannot yet say if it will be a concern.

 

 

rotating tab1.JPG

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Is the design and function dependent on having a green stub mast and tabernacle, and red locking pin? (Sorry, couldn't help myself...)

 

The locking pin could be fore and aft as designed by B&B. I wouldn't be concerned by the lack of flex in this part of the mast. The more traditional tabernacle doesn't flex either. I like the idea of the rotating mast. It allows for the snotter to not need to be readjusted to maintain the sail shape as you let the sheet in or out.

 

I had to look up "bulletwood". They don't seem to carry that at Lowe's.

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William,  The highest stress point of a free standing mast is at the point where it exits the deck.  Some flex immediately above this point helps to relieve part of this stress.  The tabernacle/mast assembly in the illustration looks to be much stiffer than an equivalent length of mast and that it will increase the stress beyond that of a normal free standing mast at this weakest point.  A logical solution to that problem is to make the lower mast section much stronger that the rest of the mast.

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Thank you William, Tom and Chick.

I appreciate your continuing ideas. Once temps here get somewhere near reasonable instead of 95+ in my garage, I think I will attempt to make the main mast be able to rotate on my CS 17m3 'Summer Breeze' and maybe even think about adding a tabernacle with rotation to my CS 17 'Lively'.

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