[Rhodes22-list] Wind Loads

[Ronald Lipton]

Bill,

   Yeah, I am also sceptical about the forces which they quote.  It is
probably for the worst case they can think of.  A motorboat with
very high freeboard and high cabin.  But it does give a general idea
of the range of forces they design for.

Ron
----- Original Message ----- 
From: "Bill Effros" <bill at effros.com>
To: "The Rhodes 22 mail list" <rhodes22-list at rhodes22.org>
Sent: Thursday, January 12, 2006 11:31 PM
Subject: [Rhodes22-list] Wind Loads


> Ron,
>
> I'm with Michael on this one.  I don't believe these wind load factors for 
> a minute.
>
> There's some highly respected guy I keep stumbling across who has spent 
> far more than one summer actually measuring the wind loads, as opposed to 
> estimating.  He says that all the standard tables are way off on the high 
> side.  I'll find him again in the course of this discussion.  I'll let you 
> know when I do.
>
> But if we take the numbers provided by Fortress and others at face value, 
> do you really think any of your cleats or eyes, mounted in heavy duty 
> Spitzer fiberglass could withstand a sustained force in excess of 3/4 ton? 
> I wouldn't want to be anywhere near a boat subjected to anything like that 
> amount of force -- whether the anchors could hold or not.
>
> I've been on board in 20 knot winds at anchor.  Everything creaks.  It's 
> scary.  Don't ever want to do that again.
>
> I've seen my boat subjected to 300 lbs of force on the bow cleat.  It 
> lifts the stern right out of the water.  I wouldn't ever want to see it 
> subjected to 5 times that much load.
>
> Will get back to relative holding power as a function of shaft angle 
> later.
>
> Bill Effros
>
>
>
> Ronald Lipton wrote:
>
>> There is a table of wind loads at the fortress site:
>> http://www.fortressanchors.com/safe_anchoring.html
>> It looks like 1600-1700 pounds at 60 mph for a 22ft
>> boat.  The page also shows the relative holding power
>> as a function of angle of the shaft with respect to the
>> bottom.  Parallel to the bottom is 100%, it falls to 10%
>> with a 2:1 scope (looks like about 30 degrees).  This is a faster
>> loss than I had thought.  The difference between 5:1 and
>> 10:1 is about 30% in holding power.
>>
>> I never would have known this stuff if Bill hadn't incited
>> the mob.
>>
>> Ron
>> On Jan 12, 2006, at 9:05 PM, Michel Meltzer wrote:
>>
>>> d)I could not find the tables for windload from the last time, can
>>> someone calculated look/up the load in lb for a rhode22 type of
>>> sailboat, IIRC I estimated about 900lb's at the top number, but I might
>>> be high.
>>
>>
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