Centre Board Lead Ballast Weight

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Centre Board Lead Ballast Weight

Postby SMHolmans on Fri Feb 22, 2019 4:04 am

Hi everyone. I poured the lead ballast in my keel and centre board a few days ago. The centre board drawing says it requires 9 kg of lead, but in practice it only took 6 kg to fill the aperture. I assume the drawing is incorrect?
SMHolmans
 
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Re: Centre Board Lead Ballast Weight

Postby mark48 on Sat Feb 23, 2019 8:08 am

I just filled the recess in the centerboard and never weighed the amount of lead required.

Mark
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Re: Centre Board Lead Ballast Weight

Postby riverron on Sat Feb 23, 2019 2:13 pm

I did the same as Mark. Just poured and didn’t weigh. We will add more portable ballast in the bilge at the end also.
Should be fine.

Ron
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Re: Centre Board Lead Ballast Weight

Postby SMHolmans on Sat Feb 23, 2019 2:23 pm

Thanks. When I cut up the lead for the centre board pour I thought it couldn't possibly all fit in the recess, and I was right. And I'm just surprised that the drawing is so far out. No big deal …. the keel lead pour went to plan. 7 kg in the front and 42 kg in the rear compartments. Perfect!
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Re: Centre Board Lead Ballast Weight

Postby Wayne G on Sat Feb 23, 2019 8:07 pm

SMHolmans,
I didn’t weigh the amount of lead either, I just assumed the weights shown on the drawing would be correct. Glad that you’ve confirmed the keel weights are to spec.

Just for the heck of it I’ve calculated the volume of lead in the centerboard based on the PocketShip drawings sheet 7 and come up with 32.27 cubic inches which equates to 12.8lbs or 5.8kg of lead.

My centerboard tends to jam when being lowered and wonder now if this could be a contributing factor.
Wayne Gray
Orlando Florida
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Re: Centre Board Lead Ballast Weight

Postby SMHolmans on Tue Feb 26, 2019 2:38 pm

Thanks for calculating the weight of the centre board ballast Wayne. I had to enlarge my aperture slightly because I made a small mistake, so that's why it swallowed up 6 kg of lead. Looks good now though! And yes, the ballast weights in the keel are just as specified in the drawing and build manual.

Steve
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Re: Centre Board Lead Ballast Weight

Postby Wayne G on Sun Mar 01, 2020 5:56 pm

That my centerboard would not drop without the use of a push stick has been an irritation since my PocketShip was launched in 2016, so following this thread where a discrepancy was discovered between the stated and actual weight of the lead shown on the drawings I bit the bullet (pun) and added another 7lbs of lead to the centerboard. The result is that the centerboard now drops without assistance...we’ll almost. If I release the centerboard while close hauled the CB behaves as before, that is it drops about 2/3 of the way and then gently stops, however, on any other point of sail it drops cleanly. I can live with that.

To access the centerboard I purchased some very expensive (but worth it) jacks that allow the trailer to be removed when the boat is jacked up.
To my surprise the unmodified CB dropped fully without hesitation when on the jacks.
Once the CB was removed I measured CB trunk opening and found it to be 1” at both ends but just 3/4” at the center. I suspected I made this error when I placed weights on the CB trunk while allowing the resin to cure during construction.
I assume that once in the water the upward pressure on the hull bottom pushes it upwards which slightly closes the trunk opening.
While this issue still exists the additional lead provides the CB with sufficient mass to pass through this restriction.

Some photos:
8C4A2E12-BC05-4E20-9BA8-5E3F4DC92868.jpeg
8C4A2E12-BC05-4E20-9BA8-5E3F4DC92868.jpeg (77.86 KiB) Viewed 1481 times

80AFF5C9-3AA7-43DB-AAC5-E954B3781FEC.jpeg
80AFF5C9-3AA7-43DB-AAC5-E954B3781FEC.jpeg (99.23 KiB) Viewed 1481 times

432DABCB-CD34-494D-8504-2D764BC4BDC5.jpeg
432DABCB-CD34-494D-8504-2D764BC4BDC5.jpeg (70.2 KiB) Viewed 1481 times
Wayne Gray
Orlando Florida
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Re: Centre Board Lead Ballast Weight

Postby Bflat on Mon Mar 02, 2020 11:54 pm

It's pretty common for CB's to have a little trouble dropping all the way down when sailing upwind. As it emerges from its case, lateral resistance kicks in and pushes it against the opening. Usually, just falling off the wind abruptly for an instant relieves the pressure allowing the board to fall the rest of the way.
Bob
Last edited by Bflat on Tue Mar 03, 2020 12:01 pm, edited 2 times in total.
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Re: Centre Board Lead Ballast Weight

Postby John in CC on Tue Mar 03, 2020 11:40 am

My inspection ports dragged on the centerboard because they protruded a bit too far. Once I figured out the problem and shaved a bit off of both lips on the portals the centerboard worked and has worked perfectly. It's something to check with some of the common inspection ports out there.
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