[Rhodes22-list] Wind Loads

[Bill Effros]

Ron,

If they can scare people into worrying about these kinds of wind loads, 
they can scare them into heavier anchors, chain, larger rode, 
windlasses, bigger deck hardware--costly overkill.

Our boats can't withstand the kind of wind loads they predict in "worst 
case" analysis.

The Guardian anchor comes with a small diameter rope.  I tested it in 20 
kt. winds.  The force on the boat was greater than I could overcome by 
pulling against it with all my might.  But I could move the boat by 
putting the line on my little winch.  I don't know, but I doubt there 
was more than 200 lbs of load, and probably much less.  I wasn't at all 
concerned about the strength of the line at that load.  The anchor never 
budged--and remember, that is a 2 1/2 lb. anchor.  It's all you'll ever 
need.

I prefer a larger line because it's more comfortable to handle.

Bill Effros

Ronald Lipton wrote:

> 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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>
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