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Old 18-08-2013, 13:54   #1
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Stability Calculations For Solar Arch

Has anyone put pencil to paper to determine how their solar/radar/davits arch will influence the stability of their boats?

I have searched the threads and found of a number of postings about arches/davits etc. but have yet to find one where someone has gone through the trouble of doing the math.

This is probably fine for most but might not be prudent for others. I think there have been at least few disasters at sea attributed to modifications to superstructures that weren't very well thought out.

Referrals to any resources would be most appreciated. I am thinking of something along the lines of a low profile arch to support solar panels and a wind generator, likely fabricated from aluminum tubing. No davits, no radar.

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Old 18-08-2013, 14:43   #2
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Re: Stability Calculations For Solar Arch

Typically you would weigh the completed arch, including panels and all wiring, and then add a compensatory lead shoe on the keel.

Of course some carefree sailors even take on extra crew without adding extra ballast to compensate for that load either.
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Old 18-08-2013, 14:57   #3
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Re: Stability Calculations For Solar Arch

from what i have OBSERVED , the weight far aft on the boat creates a condition that appears same as squatting, and the resulting boat action is pounding of the bow into seas, which is not comfortable.
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Old 18-08-2013, 15:04   #4
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Re: Stability Calculations For Solar Arch

Quote:
Originally Posted by zeehag View Post
from what i have OBSERVED , the weight far aft on the boat creates a condition that appears same as squatting, and the resulting boat action is pounding of the bow into seas, which is not comfortable.
I totally agree, certain members of my family...erhem..have decided to hang a dingy from davits connected to the solar arch. Now everything but the dog gets stored in the dinghy and the frigging boat sits on its butt in the water. So unsightly and unsailorly. But despite a bunch of off handed remarks about it my "family member" refuses to lighten the load back there. He also refuses to remove the 100 lb bucket of misc nuts and bolts he has decided he must have with him at all times. Grrrr.

The world would be a better place if everyone just did what I said.
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Old 18-08-2013, 19:43   #5
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Re: Stability Calculations For Solar Arch

Stern volume / width is a potentially offsetting factor. I hang a walker bay 10, 500 watts solar, fishing poles and antennae off the arch. Wide beam carried well aft means I don't notice any particular hobby-horsing. The bigger issue is ensuring that the dinks is strapped and can't yaw or swing freely.
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Old 18-08-2013, 20:28   #6
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Re: Stability Calculations For Solar Arch

second--you will not have hobby horsing. you will have pounding, where the bow rises and bangs into seas. different from hobby horsing.
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Old 19-08-2013, 01:11   #7
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Re: Stability Calculations For Solar Arch

If you do not have the static and dynamic specifications for what is called "light ship" condition - that is the distribution of masses and buoyancy with build and fit out completed but before any other loads are added - to start with the calculations required are very extensive. If the vessel is of fairly recent design by a professional designer or builder they could probably advise you on the matter.
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