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Spindrift 12 #1275 - Mast Length


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When I laid out my Mast sections with 9" bearing overlaps, I was 3" longer than the plans (233" vs 230" design).

I figured out that my top section is 3'-8" instead of  the 3'-5" design.

 

My inclination is to keep the extra 3" (heck - more head room from the boom.....right?)  But I don't want to assume that is OK and regret it later when I try to rig the sail, lines & hardware, try sailing it, etc.

 

If the answer is to stick with the plan length, I could either trim the top section to plan length or make 10" bearing overlaps.

 

Recommendations?

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16 hours ago, Hirilonde said:

It will add healing force to the boat.  This will also make the boat slower as the wind picks up.  I never find the head room an issue and I always liked going as fast as possible.  To each his/her own.

Wow! You just made me realize that my "layman's logic" is interfering with Graham's intricately calculated design.

I had to look up "heal force"........ https://en.wikipedia.org/wiki/Forces_on_sails    

I haven't studied forces, vectors, velocity, speed, etc... in decades.  This web page is going to take a few revisits from me before I totally "get it".

Bottom line:  Don't "F" with Graham's design. 👍😉

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Hi Jan,

 

Can you hold off on the mast until I check the shop computer tomorrow. I was under the impression that the S12 mast plan was updated. My home computer is showing a mast that I updated in 09. We have gotten rid of the wood mast heel plug and replaced it with a plastic heel which changes the length of the aluminum sections.

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We're talking about 3 inches here so it won't make a lot of difference to the heeling moment. You can always not hoist the sail the last 3 inches and it will be as designed. In theory in light airs it may be beneficial to get a little higher above the boundary layer into a stronger breeze - but we're only talking 3 inches. 

As to adding a healing force I'd do anything for that these days with the arthritis in my hand, back and shoulder🤣

Cheers

Peter HK

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22 hours ago, Graham said:

Hi Jan,

 

Can you hold off on the mast until I check the shop computer tomorrow. I was under the impression that the S12 mast plan was updated. My home computer is showing a mast that I updated in 09. We have gotten rid of the wood mast heel plug and replaced it with a plastic heel which changes the length of the aluminum sections.

I think you found the 3" explanation, Graham. 

My plans show a wood plug 6" long with 3" in the tube, 3" out.  Alan shipped me the plastic plugs (top & bottom) so I can visually understand their impact on length now.  My plans also show a wood upper section. I was pleasantly surprised to find an aluminum upper section in the kit.

However, on the plans, the 230" total length appears to visually include the wood heel plug (of +3").

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12 hours ago, Peter HK said:

We're talking about 3 inches here so it won't make a lot of difference to the heeling moment.

We have gotten into similar discussions before. Another one is the weight of adding glass sheathing to boats that don't require it.  What is a lot?  What is too much?  I want all of of my boats to be as fast and light weight as possible.  For me, anything is a lot. I can plane my Lapwing and Spindrift solo. I wouldn't sacrifice any ability to do that for anything.

 

Damned because it is all related.

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