Post-layup hull flex?
Heard something interesting today, thought your experience could help me out yet again. Have you ever heard of a hull-warping effect during an extended yard period?
As you know, Christy Lee will soon be splashing after being on the hard for a couple years. Apparently They (yes, the omnipresent ones) say that, without proper structural support in the water, boat hulls tend to "cup" forward to aft somewhat while on stands, and the ends will lower back into place once the boat is back in the water. Logic, then dictates that stays are kept loose for some period and monitored for stress. A proper tuning would have to wait a bit.
My questions then, are
Have you ever heard of this / or observed it?
What is the difference in the effect between a cored hull and the solid hull of an S-35?
Most importantly, how long should I wait before tuning the rig (it's brand new) once I've launched?
thanks in advance,
Mike
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Sat, 11/12/2011 - 13:09
#2
Hi Mike,
I have read about, but never experienced the hull warp from yard storage, but I have seen hull damage in other boats from the blocks under the keel settling in the dirt, and the pads of the jack stands crushing spots in the hull sides.
All boats are different from each other, and from my experience with mast tuning, most hulls relax whenever the rig is removed for a period of time.
You can rig and tune under sail to a perfect tension, then wait a few weeks and it will have loosened up, and have to be adjusted again.
Yes, the conventional wisdom is to wait a few weeks after a boat is put in the water, before adjusting the prop shaft alignment.
Your S-35 with the full keel would be much less likely to change alignment during storage because the keel distributes the load over a much longer area, than a fin keel boat that puts all the stress in a smaller area in the center of the boat.
Let us know how it goes,
David Vollrath SV Swell Horizon S-1330
Fri, 11/11/2011 - 13:34
#3
Hmmm... Interesting question. From personal experience I had True Love on the hard for over 14 months while stripping down the gel-coat and drying the hull. I don't recall any noticeable difference when the boat went back in the water.
That said however I normally have to remove my twin backstays in order for the travel lift to be able to pick up the boat anyway, so my backstays at least are not really even tensioned up until after the splash. After the 14 month haulout they wouldn't even let me put the mast back on the boat until the boat was back in the water, due to the height restrictions of the crane available.
My gut tells me there is quite probably a small amount of hull flex and a corresponding deflection, but I really doubt that there is significant amount of movement. These are really pretty stout boats and correspondingly I would expect them to be more on the stiffer side of things.
I would also think your rigger would have some experience with this scenario. All of this is just my humble opinion. YMMV.
Interesting points!
I had considered that Christy Lee's hull is solid glass, but I completely failed to even consider the full keel; I would think it would make a significant difference. I should find out in two or three weeks. You know, I wonder if somebody in the marina owns a tension gauge. Might make an interesting study...
Fortunately I JUST had the stands moved a couple weeks ago, there isn't any apparent warping where they were.
I won't be able to tune the rig a second time for a while, the sailing season is really over. Takes me back to that tension gauge idea...
Hmmmm...
Mike McCombs
SV Christy Lee
S-35 Hull 8
Chesapeake, VA, USA
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