vangs are good for stopping booms rising but not for lifting weights.
 

FYI:

Now this may come as a surprise, but the boom is more likely to buckle
if a rigid vang is used to lift a weight at the boom end than if the
same load is upward (as applied by a sail).

In the upward case the boom wall is being pulled out by the vang -an
effect opposed by tension in the boom surface due to the bending moment.
In the weight lifting case, the lower surface is in compression and is
being pushed in by the vang so that wall buckling is far more likely.

Cheers

Well of course...... and let's not even the mechanical disadvantage offered
by the location of the vang. ;-)

CM
"Nav" wrote in message
...
|
| FYI:
|
| Now this may come as a surprise, but the boom is more likely to buckle
| if a rigid vang is used to lift a weight at the boom end than if the
| same load is upward (as applied by a sail).
|
| In the upward case the boom wall is being pulled out by the vang -an
| effect opposed by tension in the boom surface due to the bending moment.
| In the weight lifting case, the lower surface is in compression and is
| being pushed in by the vang so that wall buckling is far more likely.
|
| Cheers
|

right conclusion, wrong reasoning.

hint: the net resultant load on a boom from a load at the end *is* at the end,
which gives a long lever arm. the net resultant load on a boom from the _same_
load on a sail is at the center or effort on the sail, roughly where the vang
attaches, which gives a short lever arm.




From: Nav
Date: 8/24/2004 7:23 PM Eastern Daylight Time
Message-id:


FYI:

Now this may come as a surprise, but the boom is more likely to buckle
if a rigid vang is used to lift a weight at the boom end than if the
same load is upward (as applied by a sail).

In the upward case the boom wall is being pulled out by the vang -an
effect opposed by tension in the boom surface due to the bending moment.
In the weight lifting case, the lower surface is in compression and is
being pushed in by the vang so that wall buckling is far more likely.

Cheers

Not on my boom it doesn't. The forces appear at the clew...

Cheers

JAXAshby wrote:

right conclusion, wrong reasoning.

hint: the net resultant load on a boom from a load at the end *is* at the end,
which gives a long lever arm. the net resultant load on a boom from the _same_
load on a sail is at the center or effort on the sail, roughly where the vang
attaches, which gives a short lever arm.





From: Nav
Date: 8/24/2004 7:23 PM Eastern Daylight Time
Message-id:


FYI:

Now this may come as a surprise, but the boom is more likely to buckle
if a rigid vang is used to lift a weight at the boom end than if the
same load is upward (as applied by a sail).

In the upward case the boom wall is being pulled out by the vang -an
effect opposed by tension in the boom surface due to the bending moment.
In the weight lifting case, the lower surface is in compression and is
being pushed in by the vang so that wall buckling is far more likely.

Cheers

let's if I understand you correctly. *your* midsheet boom has the very same
load put on the vang from a weight hung off booms end as the same load pulled
upwards on the boom about 1/3 of the way outward from the mast??

Gee, that is interesting. *you* boom does not form a lever. my, my, my. how
did you get *you* boom to ignore the laws of physics?


From: Nav
Date: 8/24/2004 10:25 PM Eastern Daylight Time
Message-id:

Not on my boom it doesn't. The forces appear at the clew...

Cheers

JAXAshby wrote:

right conclusion, wrong reasoning.

hint: the net resultant load on a boom from a load at the end *is* at the
end,
which gives a long lever arm. the net resultant load on a boom from the
_same_
load on a sail is at the center or effort on the sail, roughly where the
vang
attaches, which gives a short lever arm.





From: Nav
Date: 8/24/2004 7:23 PM Eastern Daylight Time
Message-id:


FYI:

Now this may come as a surprise, but the boom is more likely to buckle
if a rigid vang is used to lift a weight at the boom end than if the
same load is upward (as applied by a sail).

In the upward case the boom wall is being pulled out by the vang -an
effect opposed by tension in the boom surface due to the bending moment.
In the weight lifting case, the lower surface is in compression and is
being pushed in by the vang so that wall buckling is far more likely.

Cheers

Jax,

I'm not sure I understand what you're saying?

On my Boom, With a free footed main, I have no upward pressure other
than at the Clew of the sail and at the Tack. I believe this to be about
the same with a boltroped foot also. Pretty much so.

My downward pressure is supplied at the center location by the center
located main ( three blocks) and the vang appox. 1/4 of the way back
from the Tack. This is transmitted to the clew and the tack of the main
by the Boom

I have no direct effect on the center effort of the sail by downward
force of the boom. This downward pressure controls the twist of the Main
( Leech Tension)

I'm not sure what you are saying about center of effort, Am I missing
something?

Ole Thom

Yes, to repeat myself, the sail forces is applied at the clew and it is
irrelevant where the sail C of E is for the boom.

Cheers

JAXAshby wrote:
let's if I understand you correctly. *your* midsheet boom has the very same
load put on the vang from a weight hung off booms end as the same load pulled
upwards on the boom about 1/3 of the way outward from the mast??

Gee, that is interesting. *you* boom does not form a lever. my, my, my. how
did you get *you* boom to ignore the laws of physics?



From: Nav
Date: 8/24/2004 10:25 PM Eastern Daylight Time
Message-id:

Not on my boom it doesn't. The forces appear at the clew...

Cheers

JAXAshby wrote:


right conclusion, wrong reasoning.

hint: the net resultant load on a boom from a load at the end *is* at the

end,

which gives a long lever arm. the net resultant load on a boom from the

_same_

load on a sail is at the center or effort on the sail, roughly where the

vang

attaches, which gives a short lever arm.






From: Nav
Date: 8/24/2004 7:23 PM Eastern Daylight Time
Message-id:


FYI:

Now this may come as a surprise, but the boom is more likely to buckle
if a rigid vang is used to lift a weight at the boom end than if the
same load is upward (as applied by a sail).

In the upward case the boom wall is being pulled out by the vang -an
effect opposed by tension in the boom surface due to the bending moment.
In the weight lifting case, the lower surface is in compression and is
being pushed in by the vang so that wall buckling is far more likely.

Cheers