[Public-List] replacement spreaders

[Roger L. Kingsland]

Makes perfect sense; time to reverse spreaders; needed to trim the spacer
plates so they won't cut the halyards anyway.


-----Original Message-----
From: public-list-bounces at lists.alberg30.org
[mailto:public-list-bounces at lists.alberg30.org] On Behalf Of
brooks.glenn at comcast.net
Sent: Friday, June 03, 2011 3:35 PM
To: Alberg 30 Public List -- open to all
Subject: Re: [Public-List] replacement spreaders

Dolce ( #318, built 1968) has tapered wood spreaders also. Rounded edge
forward, tapered edge facing aft. They are essentially an airfoil, creating
a bit of lift, and presumably reducing turbulence off the trailing edge and
adjacent portions of the sail. The tapered edge should certainly be facing
aft. Also the I would think the shock loads mostly originate from forward of
the mast and travel aft to the stern. Thin sections are very weak compared
to arched cross sections. The thicker rounded leading edge of the spreader
would provide much greater inertial dampening of the shock waves imparted to
the spreader and adjacent fittings. I think over time, reversing the
spreaders, and having the tapered edge more greatly affected by buffeting
and vibration ( shock loading) would eventually accelerate fatigue in the
spreader. 


Does this sound reasonable?? 


Glenn B 

----- Original Message ----- 
From: "Don Campbell" <dk.campbell at sympatico.ca> 
To: "Alberg 30 Public List -- open to all" <public-list at lists.alberg30.org> 
Sent: Friday, June 3, 2011 9:48:58 AM 
Subject: Re: [Public-List] replacement spreaders 

Roger, just be aware that F.W. Kay in his book, The Science of Yachts, 
Wind, and Water, on page 63 shows the wind resistance for a tapered form 
with the nose a semi-circle and teh tail tapered to a point, the taper 
out of the wind, as 1 and the reverse, so the taper to the wind, as 
1.6. While you may not think it, fish are smart and have their tails on 
the correct, trailing edge. Evolution does work for some things in 
water and fluids like air. (One gets a value of 1 for a circle as 
well, but the diameter of the circle that does have a value of 1 is 
1/10 the the diameter of the tapered shape. 
Time to reverse the spreader's direction, that is if you want a 
faster boat, or at least no obvious slow downs. 
Don 

On 6/3/2011 12:03 PM, Roger L. Kingsland wrote: 
> Michael, 
> 
> This is easy for me because, it just so happens, both tapers (in plan and 
> cross section) face the same way which, for now, is forward. Good Lord 
> willing and the creek don't rise, it will contribute to a fast boat. 
> 
> Best, Roger 
> 
> PS - Has anyone replaced wood spreaders with aluminum; if so, who did it
and 
> how dear was it? 
> 
> 
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