small block at bottom of tabernacle

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small block at bottom of tabernacle

Postby dbeck on Sun Jul 14, 2024 1:40 am

Yesterday I had my first try on installing and raising the mast.

On page 270, the manual suggests a small block of 3/4" thickness to achieve a bit of rake in the mast.

In an old forum post [1], John writes
Set up the shrouds so that the mast can't pivot forward and cantilever itself against the tabernacle,


My interpretation of the latter statement is, that the erected mast is supposed to have contact only to the pivot bolt but not the 3/4" small block at the bottom of the tabernacle.

My question: Do you remove the 3/4" block after the shroud length has been set? Or do you leave that block in and you tighten the jib halyard only that much, that the bottom of the mast does not touch that block?

[1] viewtopic.php?f=3&t=633&hilit=shroud+bulkhead&start=20#p4387
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Re: small block at bottom of tabernacle

Postby [email protected] on Tue Jul 16, 2024 2:15 pm

My own boat has a reasonable amount weather helm without the shim at the base of the mast. There was no reason to add it.
Try sailing without it to see if it is really necessary.
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Re: small block at bottom of tabernacle

Postby dbeck on Tue Jul 16, 2024 4:07 pm

Thanks for the info Doug. Does the base of your mast touch the back of the tabernacle after the jib halyard has been tightened? Or the other way round: How do you determine the correct tension of the shrouds? And how hard do you tighten the jib halyard? I understand, that Pocketship as a gaffer requires little rig tension compared to a racing dinghy.

Dietrich
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Re: small block at bottom of tabernacle

Postby Bflat on Wed Jul 17, 2024 12:35 pm

I left a space at the bottom. It seems to me that having contact could cause the mast to lever the tabernacle off if the shrouds happen to be even slightly too loose.
Bob
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Re: small block at bottom of tabernacle

Postby slash2 on Thu Jul 18, 2024 6:00 pm

I tensioned my shrouds evenly keeping about as much tension as I could on the lashings. I believe John, in his Pocketship set up video, states the jib halyard should be ‘guitar string’ tight. With the lashed stays and halyard, I don’t think you can seriously over tighten the rigging. On the other hand, if it’s loose you will have trouble.
Steve Sawtelle
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Re: small block at bottom of tabernacle

Postby dbeck on Fri Jul 19, 2024 3:13 am

Doug, Steve, Martin, Bob,

thanks for your replies.

Steve, could you send me a link to that setup video? I thought I knew all Pocketship videos. But I find that one neither on Youtube nor via the CLC Boatbuilding Video Collection on the CLC website.

Dietrich
Last edited by dbeck on Fri Jul 19, 2024 6:54 am, edited 1 time in total.
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Re: small block at bottom of tabernacle

Postby [email protected] on Fri Jul 19, 2024 4:06 am

I think the bottom of the mast just barely touches the back of the tabernacle. But I am not sure - I adjusted the shrouds once when I installed them two years ago, and I haven;t had to adjust them since then.
The mast is pretty stiff and the boom is not attached to it, so it does not seem to flex hardly at all.

dbeck wrote:Thanks for the info Doug. Does the base of your mast touch the back of the tabernacle after the jib halyard has been tightened? Or the other way round: How do you determine the correct tension of the shrouds? And how hard do you tighten the jib halyard? I understand, that Pocketship as a gaffer requires little rig tension compared to a racing dinghy.

Dietrich
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Re: small block at bottom of tabernacle

Postby Tom G on Tue Jul 23, 2024 8:27 am

I believe the base of the mast should touch the forward edge of tabernacle when the jib halyard is tensioned to stabilize the rig. I don't think you would want the shrouds so tight that they prevent this contact. The shroud adjustment also keeps the mast in column vertically above the boa and prevents it from moving off too far to leeward when under sail. If it moves a long way you risk breaking the tabernacle. I have the3/4 inch block in stalled but have never tried it with out one. If you do the math I think this little block moves the top of the mast back around 3 inches. Depending how close your head stay is to the spec length you can end up with a situation where the top thimble on the head stay touches the block at the top of the mast and prevents full tension on the jib. My head stay was a bit too long and this occurred even with the block so I ended up shortening it a bit. Now that I have a shorter head stay I might try sailing with out the block to see what I think.
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Re: small block at bottom of tabernacle

Postby slash2 on Tue Jul 23, 2024 10:40 am

Hi Dietrich,

I saw the mention of ‘guitar string tight’ in the first video on the Pocketship page on CLC website- “Launching and sailing Pocketship” - about 3 minutes in.

-steve
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Re: small block at bottom of tabernacle

Postby dbeck on Wed Jul 24, 2024 2:44 am

slash2 wrote:I saw the mention of ‘guitar string tight’ in the first video on the Pocketship page on CLC website- “Launching and sailing Pocketship” - about 3 minutes in.
-steve


Ah, thx. Hm, on the video it does not look as John Harris is applying much force to the halyard. At least I have to work harder to achieve 'guiter-string tightness' :-)

@Tom: Yes, I tried with and w/o that block. The forestay is according to specs, but actually it feels a little bit too long without that block. The shrouds feel quite tight but maybe we'll shorten the lashings a little bit.

Thanks for all the replies.
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