nacra I20

[john baker]

Hi guys,

I am thinking about a project on a Nacra Inter 20. The project involves the sheave on the top of the mast that is used for the spinnaker halyard. Does anyone know the diameter of the sheave and the diameter of the pin that goes through the sheave?

thanks,

JMB

[john baker]

wait a minute. That is not right. The sheave is for the main halyard.

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[gordon pease]

I think there is a sheeve.  Bovine has a dyneema line around the sheeve to a block at the right height.  No longer using the upper sheeve. 

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[Will Rottgering]

The main halyard has a sheave, the spinnaker halyard used a Harken 29 mm bullet cheek block.

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[vladimir.eremeev]

Hi, John. There were two types of mast caps on inter boats. One was aluminum and another one carbon fiber. 

If the cap is carbon fiber then the sheave is 1 inch diameter with 1/4 inch pin. It is either 1/2 inch or possibly 7/8 thick, I can remeasure if needed.

If the cap is aluminum it can take a bigger diameter sheave, it’s sometimes useful for fine tuning hook/ring lock 

I tried to post it with pics and I don’t see the post anywhere. So this is my second try without pics. 

Vlad.

Nacra inter 17R

Nacra Inter 20

[Vladimir Eremeev]

Here are the pics, another try with smaller sizes

Sent from my iPhone

On May 11, 2026, at 11:03 AM, vladimir.eremeev <vladimir...@gmail.com> wrote:

Hi, John. There were two types of mast caps on inter boats. One was aluminum and another one carbon fiber. 

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[john baker]

Hi guys,

Thanks for the replies to my questions. They are very helpful. That is one of the things I like about this group. 

There are other groups that would get snarky and reply with more questions. Such as:

Why do you want to know? Shouldn't you already know the answer? Why are you working on a Nacra 20 anyway?

But not this group. We are helpful. Not judgemental. Well not publicly judgemental.

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[Will Rottgering]

Don't worry Mr Baker, we're talking about you behind you back in those other groups!! 🤣🤣

To view this discussion visit https://groups.google.com/d/msgid/WRCRA/827871270.687147.1778513831378%40connect.xfinity.com.

[ken reid]

You all need Harbor freight cheapy calipers for measuring pins and holes.

Ken Reid

311 Martins Cove Rd

Annapolis MD 21409

305-301-4503

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[Patrick Nelson]

John, 

As you are an asset to the fleet, I just assumed you were helping some poor soul out with their boat. 

I remember when my tramp zipper broke and you helped me manually put all the teeth back together using pliers and then I sewed it shut cause I didn't want to pay to fix it.  I thought, "What a guy".  It was a miserable job that he should have said "this is stupid."  Then I lent my boat to Will and he blew it all up and I had to get it fixed. 

Patrick

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[Patrick Stadt]

John, Kreskin has nothing on you!  Those were my exact questions and I am baffled that nobody replied with them (I was traveling….)

Pat

On May 11, 2026, at 10:37, 'john baker' via West River Catamaran Racing Association <WR...@googlegroups.com> wrote:



Hi guys,

Thanks for the replies to my questions. They are very helpful. That is one of the things I like about this group. 

There are other groups that would get snarky and reply with more questions. Such as:

Why do you want to know? Shouldn't you already know the answer? Why are you working on a Nacra 20 anyway?

But not this group. We are helpful. Not judgemental. Well not publicly judgemental.

On 05/11/2026 11:29 AM EDT Vladimir Eremeev <vladimir...@gmail.com> wrote:

 

 

Here are the pics, another try with smaller sizes

<image0.jpeg>

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[Sam Carter]

I likely have replacement sheaves for those in my box...have a few sizes...I might be down this weekend. There is a remote chance the big west marine in Annapolis has something that will work, otherwise its special order.

Calipers: IP54 digital, 6in on Amazon are better than the harbor freights in my experience: https://www.amazon.com/Digital-Caliper-Electronic-Micrometer-Millimeter/dp/B09DSS8SZ9/ref=sr_1_2_sspa?crid=HYUSE4P6WHS8&dib=eyJ2IjoiMSJ9.GcxpzCk2n0BPf16LRv4eB5LZ5SAOEOWOwIFCdzlpfJLgWP7SFg6wVoauoHgEC2p5qzVAA7t55n-0p6SeGJtn_AvJNKB8F4ZPWGbIZliOlJ1vDbf4xkl_eMx5aNn_Ubf_YGpDeZVYClIMub0DPT_aYEN3rpqonzWsPLUhzqGizdNO4OF9-x0l_dOLgEFypfUilqYnI2H-3kz3UifDeBL5DsTwp_Dq_MAEM-wV_ikX5gc.1yvHrfkiG96QjanicfFyMVwunmKr7muByrlVDPiylvo&dib_tag=se&keywords=IP54%2Bdigital%2Bcaliper&qid=1778604761&sprefix=ip54%2Bdigital%2Bcaliper%2Caps%2C117&sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

[Will Rottgering]

I'm 99.9% sure I have one in the front box of my trailer 

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