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Old 07-09-2018, 00:52   #16
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Re: Mast rake , can effect mast pumping??

Thank you , by turnbuckle I mean the wire end at the top , I don't know the English name .
I will experiment and try to solve the issue following your advice thank you.
I am not sure if the.mast is 3/4 of 9/10 but the height of the mainsail is 9.80m and the forestay starts around 2 m.lower .( Not exactly measurements )
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Old 07-09-2018, 01:12   #17
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Re: Mast rake , can effect mast pumping??

Dear Gmakhs.

I think you ´re referring to the eye terminal at the top. Doesn´t really matter what we call it, as long you´ re positive they didn´t add a turnbuckle up there..

By the way, 3/4 or 9/10 were just two examples of fractional rigs. It can be anywhere in between, or even a 19/20 for that matter.

This isn´t rocket science, so bring a friend, have a cop of coffee and get to work.

You´re gonna be just fine!

Best regards,
-kjetil-
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Old 07-09-2018, 02:25   #18
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Re: Mast rake , can effect mast pumping??

Good advice from Blis.

One random thought. Is the base of the mast flat on the mast step? Depending on the type of base, If the mast is raked too far aft for the angle of the base it can lift the front of the mast off the base. This can cause it to bend forward in the middle much easier under compression loading and pivot on the aft edge of the mast. Many modern masts have a rounded mast base to account for different rake angles, so this may not be the issue.
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Old 07-09-2018, 15:13   #19
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Re: Mast rake , can effect mast pumping??

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Originally Posted by Snowpetrel View Post
Good advice from Blis.

One random thought. Is the base of the mast flat on the mast step? Depending on the type of base, If the mast is raked too far aft for the angle of the base it can lift the front of the mast off the base. This can cause it to bend forward in the middle much easier under compression loading and pivot on the aft edge of the mast. Many modern masts have a rounded mast base to account for different rake angles, so this may not be the issue.
It's a T bass no pin just the must on it .
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Old 07-09-2018, 16:55   #20
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Re: Mast rake , can effect mast pumping??

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It's a T bass no pin just the must on it .
So in this case if it's what I am thinking you mean the mast could either rock on a curved mast plug, or it could be cut square. If the mast is cut square at the base it should sit flat. Some racing boats deliberately use the bend induced by an angled base and gap to help sail trim/mast bend. But this will reduce fore and aft mast stability, and an inline rig like yours needs all the help it can get.

This may not be the issue, but its worth checking. Pull on the babystay and see where the base pivots is the mast bends.

A firm babystay should help damp any pumping. And a moderate amount of backstay will also help. But it sounds like the mast is getting too much prebend just from compression at the moment. Other things to check are the boom and kicker adjustments. Its just possible that the boom was stabilizing the rig a little. Click image for larger version

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Old 09-09-2018, 00:00   #21
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Re: Mast rake , can effect mast pumping??

My own two cents..

If you have a fractional rig with a babystay but in-line spreaders, not swept back spreaders, then you have nothing to stiffen up the mast bend which would be produced from the forestay and backstay. Normally I would guess the babystay and rearward facing lower shrouds control the mast longitudinal position at mid height and stiffen up the mast here to control pumping. If your lower shrouds are not swept back you only have this stiffness in one direction. You can only use the babystay as a sort of pretensioning device and hope the pumping tendencies do not overcome this under normal use.

What do you think?
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Old 09-09-2018, 10:04   #22
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Re: Mast rake , can effect mast pumping??

Perna
I do agree with your way of thinking but the mast wasn't pumping before
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Old 09-09-2018, 14:45   #23
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Re: Mast rake , can effect mast pumping??

What I meant was if the baby stay is tight enough to induce a bit of mast bend then the mast would not be free to move or rattle at mid height. Not in the dock anyway.

Pumping proper I think refers to this forward/backward movement under sailing conditions where the inertia and sail forces are altogether greater. Are you talking about under sailing or in the dock?

Apologies if I have misunderstood. There are many far more experienced sailors here
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Old 09-09-2018, 16:11   #24
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Re: Mast rake , can effect mast pumping??

The rigger hasn't kicked a spreader base loose? That sort of rig needs accurate and firm spreaders to impart a bit of fore and aft stability.
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