DSK wrote:
And the compression on the mast is likely to
be a multiple of the weight involved.

Oh boy! I though you said you knew some engineering. The vertical force
is _exactly_ the weight of the lifted object Doug.

Cheers

It's kind of bizarre that a bunch of dinghy sialors talk about people
standing on the end of flimsy booms doncha think?

Cheers

John Cairns wrote:

Slow down, Mooron. I was merely verifying what Doug mentioned, I assuming
that's what he was referring to, the ability of a rigid vang to support the
weight of an individual standing on the boom. I wasn't necessarily referring
to you when I talked about "improvements in sailing technology" Of course
the boom end is supported better by a topping lift on the end than it is by
a rigid vang mounted a quarter of a way along it's length. But a rigid still
offers enough support to hoist someone out of the water with the end of the
boom, or lift an auxiliary out of the engine compartment. Not that I never
question the merits of "technology improvements", I like to think I try to
keep a fair amount of skepticism when I see words like"new and improved",
but I don't reflexively assume that improvements aren't just that. In any
event, I wouldn't think that capacity is an issue when debating the merits
rigid boom vangs. One last point, if you retrofit a rigid vang to you boat
you still have a topping lift to use for things like hoisting someone to the
masthead, or hoisting an auxiliary out of your engine compartment, etc. BTW,
I'm not rushing out to buy a rigid vang for my boat, it's fairly low on my
list of future boat improvements.
John Cairns


"Capt. Mooron" wrote in message
...

Good Grief John.... how can you miss the point of this whole discussion so
adeptly.

Nobody is arguing the merits of the technology... what is being debated

is

the advantage in capacity between a topping lift and a vang.

...and by the way... since when do you undertake the option of never
questioning "improvements in sailing technology"?

CM



"John Cairns" wrote in message
. com...
| Because you've seen someone step up onto the boom to do some work, as

did

| the skipper during the Trans-Erie, he had to re-run a jiffy reefing line
| through a reef clew grommet. You some of the folks here are taking up

the

| arguments of the lately departed Captain Neal, who never met an
improvement
| in sailing technology that he didn't like.
| John Cairns
|
| "DSK" wrote in message
| . ..
| Last but not least, booms supported by solid vangs will (if properly
| engineered) hold up weights at least as heavy as a medium size adult.
| Ask me how I know this for a fact!
|
| Fresh Breezes- Doug King
|
|
|

DSK wrote:

Thom Stewart wrote:

... The improved
booms of today are not meant for end loading with shear pressure.


Shear or torsion?


Good lord. Another engineering term not understood by you!

Cheers

DSK wrote:



Your statements about rigid vangs are like the yokel who was shown a
picture of a giraffe and said "there cain't be no such anny-mal."



Reverting to the good old ad hominem!

Cheers

DSK wrote:

Capt. Mooron wrote:

No John.. I believe Doug's premise is that a properly engineered vang can
equal the capacity of a topping lift... that I dispute.


And you're wrong.

Allow me to put to you 2 separate scenarios... a rigid vang on a 20
footer
and a rigid vang on a 50 footer. Now... on the 20 footer it's obvious the
weight of a man on the end of the boom would tax the rigid vang....


Not necessarily. It depends entirely on how the rig is built.

Ever seen a man standing at the end of a _real_ 20' boat boom supported
by just a rigid vang? Can you imagine it's bend? Try it on you dinghy
-that's about 20' -and you can block up the boom at the vang position.
Then send us the picture -since you are so sure it'll work OK!

Cheers

Capt. Mooron wrote:

"DSK" wrote in message


I think you'd better give your head a shake.... you have explained
nothing... you have obfuscated and side tracked, you've attempted to bring
in a plethora of variables to substantiate your claims. You have provided
very little in the form of actual, logical counter points to my statements.
You've been reduced to brash accusations regarding my experience.... and
now you lament wasted time.... the reasoning of a failed argument.

But if he didn't he wouldn't be Doug!

Cheers

Just for fun why not do a simple engineering calculation for us Doug?

For simplicity let's say the rig has mast without any stays.

Mast 20' vertical Boom 10' horizontal. Gooseneck 3' from base of mast
Vang attched to point 3' from goosneck. 200 lbs to be lifted.

What is the bending moment on the boom at the vang if the load is held
by the vang?
What is the shear stress on the boom the load is held by the vang?
What is the compression force of the boom at the vang attachment?

Now let me quickly solve for the topping lift case:

If a topping lift is used, the bending moment at the vang is 0.
If a topping lift is used, the shear stress is 0
If a topping lift is used, the boom compression is 200 x 10 /17 = 118 lbs.

What is the maximum stress at the vang attachment point in each case?

Cheers

Have you ever had a girlfriend, Nav?

You are incredibly smart...but incredibly boring at the same time.

Any excitement in your life?

LP (curious minds want to know)


"Nav" wrote in message
...
Just for fun why not do a simple engineering calculation for us Doug?

For simplicity let's say the rig has mast without any stays.

Mast 20' vertical Boom 10' horizontal. Gooseneck 3' from base of mast
Vang attched to point 3' from goosneck. 200 lbs to be lifted.

What is the bending moment on the boom at the vang if the load is held
by the vang?
What is the shear stress on the boom the load is held by the vang?
What is the compression force of the boom at the vang attachment?

Now let me quickly solve for the topping lift case:

If a topping lift is used, the bending moment at the vang is 0.
If a topping lift is used, the shear stress is 0
If a topping lift is used, the boom compression is 200 x 10 /17 = 118 lbs.

What is the maximum stress at the vang attachment point in each case?

Cheers

Gee whiz Nav,
how long have you been waiting to work that one into a conversation?
Scout

"Nav" wrote in message
...
Just for fun why not do a simple engineering calculation for us Doug?

For simplicity let's say the rig has mast without any stays.

Mast 20' vertical Boom 10' horizontal. Gooseneck 3' from base of mast
Vang attched to point 3' from goosneck. 200 lbs to be lifted.

What is the bending moment on the boom at the vang if the load is held
by the vang?
What is the shear stress on the boom the load is held by the vang?
What is the compression force of the boom at the vang attachment?

Now let me quickly solve for the topping lift case:

If a topping lift is used, the bending moment at the vang is 0.
If a topping lift is used, the shear stress is 0
If a topping lift is used, the boom compression is 200 x 10 /17 = 118 lbs.

What is the maximum stress at the vang attachment point in each case?

Cheers

MC,

If you fo to all tht trouble of figuring things out every time you sail, do
you ever get to relax? You should have a hibernate setting on the right
side of your brain.
"Scout" wrote in message
...
Gee whiz Nav,
how long have you been waiting to work that one into a conversation?
Scout

"Nav" wrote in message
...
Just for fun why not do a simple engineering calculation for us Doug?

For simplicity let's say the rig has mast without any stays.

Mast 20' vertical Boom 10' horizontal. Gooseneck 3' from base of mast
Vang attched to point 3' from goosneck. 200 lbs to be lifted.

What is the bending moment on the boom at the vang if the load is held
by the vang?
What is the shear stress on the boom the load is held by the vang?
What is the compression force of the boom at the vang attachment?

Now let me quickly solve for the topping lift case:

If a topping lift is used, the bending moment at the vang is 0.
If a topping lift is used, the shear stress is 0
If a topping lift is used, the boom compression is 200 x 10 /17 = 118
lbs.

What is the maximum stress at the vang attachment point in each case?

Cheers