"DSK" wrote in message
| You mean the boom takes the load as compression... guess what, so does
| the mast, and all the rigging, which transfers it to the hull. The load
| is the same, the total amount of stress is the same, except that much of
| the rigging is pre-loaded. And the compression on the mast is likely to
| be a multiple of the weight involved.

No Doug.... I believe that assumption to be incorrect... you fail to
incorporate the dispersion of the load from the mast head to compression of
the mast and delivery of portions of the load to the shrouds. When you
transfer the load to the vang alone [ via the boom].. the mast is only
subject to a side load from the vang fitting and all the force is supported
by the boom/vang. None of the load is distributed to the entire mast or the
shrouds. In other words any portion of the mast above the boom is not
utilized in the dispersion of the forces generated by the bearing loads.


|
|
| ...while with the vang all the load is delivered to the boom and
| the vang is subjected to the magnified loads.... in other words the
load is
| delivered to the vang and the leverage is delivered by the boom. That's
why
| I mentioned the fulcrum earlier.
|
| OK. It's still not a good explanation and tends to muddy the engineering
| points.

The only thing muddy here is your refusal to approach this with an open
mind..


|
| The weight is the same... check.
|
| With a topping lift, you seem to think that the boom has very little
| stress on it. That is not the case.

I never stated very little stress.. I stated much less stress by a greater
margin than with the vang based option.

|
| Imagine this... replace the boom with your arms. Hang a 100# weight from
| a long rope, and then try to push it 12' away from hanging straight
| down. Depending on the angle to the point of hoist, you could end up
| with more than 100 pounds of force.

Ridiculous... the force required to push it away would be far less than the
force required to keep the arm level while applying force to a point just
aft of my elbow!
|
|
|
| When the boom is the spreader the force is compressive and much less
than
| the forces applied to the vang in such a situation. The topping lift
bears
| the entire load.
|
| No it does not. Do you think the force magically goes away because there
| is a topping lift?

It does not go away nor did I say it did... I said the load is more evenly
distributed over a greater span.. Mast, Boom, Topping lift, Shrouds... etc.
This of course increases the ability of the rig to undertake the bearing
forces. Gawd forbid you would ever be required to calc break-out forces
generated by excavators.


|
|
| Can you see the point of my argument now??
|
| Yes, can you see the error you're making? You should make a diagram of
| the forces involved. It will help you visualize the situation properly.

I am most definitely not in error here Doug... you are... swallow your pride
and look at this problem with an eye to structural engineering. I am
visualizing the situation and after much thought and further toying with the
idea I came to the conclusion that you are not correct in your theory
regarding forces delivered to the vang. You have yet to present a viable
defense for your position on this while I have offered several sound,
reasoned, and logical counterpoints to your pretense.

|
| With a solid vang, that the force on the boom vang is greater than the
| weight is not (or should not be) a problem, no more than the compression
| on an old-timey noodley boom is. They're designed for that. If the gear
| is designed & built properly for it's use, then it is fine.

No Doug... it's not the case at all.... the vang is badly situated to handle
the loads you intend to place to it. The topping lift offers a much better
and more efficient distribution of the load ... thus increasing it's ability
to handle much greater loads.

|
| Ever notice how on modern boats, the boom is not just so shorter section
| of the same type extrusion as the mast? There are engineering reasons
| for that (plus it looks cool).

Quit toying with the damn boom.... look think of it this way... how many
lifting devices utilize a support located under the boom at less than 25% of
the boom length? NONE!
Now how many utilize a cable [topping lift] to the end of the boom?? MOST!

You are dead wrong on this Doug... really!

CM

| ...And the compression on the mast is likely to
| be a multiple of the weight involved.

Capt. Mooron wrote:
No Doug.... I believe that assumption to be incorrect... you fail to
incorporate the dispersion of the load from the mast head to compression of
the mast and delivery of portions of the load to the shrouds.

???

Are you saying that shrouds & stays push up on the mast?


... When you
transfer the load to the vang alone [ via the boom].. the mast is only
subject to a side load from the vang fitting and all the force is supported
by the boom/vang. None of the load is distributed to the entire mast or the
shrouds. In other words any portion of the mast above the boom is not
utilized in the dispersion of the forces generated by the bearing loads.

Please explain further. How is this load "dispersed"? Into the air, maybe?


The only thing muddy here is your refusal to approach this with an open
mind..

If having an open minds leads to conclusions like that above, then I'm
better off (from the engineering standpoint) without.

Fresh Breezes- Doug King

Sounds similar to a thread where you were rebutting a Kerry bashing.

Is this the best you can do?

"DSK" wrote

Are you saying that shrouds & stays push up on the mast?

"The best" is what is true & real.

Shrouds don't push up on a mast and do not "disprse" any loads.

Kerry bashing by paid shills is a poor reason to decide a vote.

"I never give them hell. I just tell the truth and they think it's hell."
--Harry S. Truman

Bart Senior wrote:
Sounds similar to a thread where you were rebutting a Kerry bashing.

Is this the best you can do?

"DSK" wrote

Are you saying that shrouds & stays push up on the mast?

Doug I didn't get your last post... can you repost it so I can attack your
position with some decorum... Thnx ;-)

CM

| "DSK" wrote
|
| Are you saying that shrouds & stays push up on the mast?
|
|
|
|

Capt. Mooron wrote:
Doug I didn't get your last post... can you repost it so I can attack your
position with some decorum... Thnx ;-)

Sorry, it's gone with the wind. However, I can probably remember the
gist of it well enough.

You said that the shrouds "disperse" the load, which is crazy. Shrouds
keep the mast from falling over, at the cost of placing the mast under
compression. A side load on the mast increases tension on the shroud,
which increases compression on the mast. So, the compression on the mast
will *always* be greater than the weight load placed on it... and that's
not taking into account the static tension on the rig (pre-load).

The difference between a boom holding a heavy weight, supported by a
topping lift; and one supported by a solid vang is this:

The topping lift will transfer the weight to the masthead, increasing
compression on the mast. The shrouds keep the mast from falling towards
the weight, increasing compression on the mast. The boom is in
compression, keeping the weight from swinging in towards the mast. The
compression on the mast & tension on the shrouds place a torsion load on
the hull.

The solid boom vang will be in compression. The boom will be in torsion
between the weight pulling down and the vang pushing up. The mast will
have a torsion load on it from the gooseneck to the lower boom vang
swivel fitting.

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 in message
| You said that the shrouds "disperse" the load, which is crazy. Shrouds
| keep the mast from falling over, at the cost of placing the mast under
| compression. A side load on the mast increases tension on the shroud,
| which increases compression on the mast. So, the compression on the mast
| will *always* be greater than the weight load placed on it... and that's
| not taking into account the static tension on the rig (pre-load).

Okay I can agree with the premise that the shrouds provide stability [via
tension].... but the fact that they are attached to the mast indicates
that a transmission of stress is allocated to the shrouds.


|
| The difference between a boom holding a heavy weight, supported by a
| topping lift; and one supported by a solid vang is this:
|
| The topping lift will transfer the weight to the masthead, increasing
| compression on the mast. The shrouds keep the mast from falling towards
| the weight, increasing compression on the mast. The boom is in
| compression, keeping the weight from swinging in towards the mast. The
| compression on the mast & tension on the shrouds place a torsion load on
| the hull.

I concur.. that seems to be a logical dispersion of forces.

|
| The solid boom vang will be in compression. The boom will be in torsion
| between the weight pulling down and the vang pushing up. The mast will
| have a torsion load on it from the gooseneck to the lower boom vang
| swivel fitting.

Again I concur...

|
| 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!

Although I agree with this... my argument was regarding the actual load
capacity between the vang and the topping lift. My point is the topping lift
is able to handle much greater loads than the vang ever could. On this
aspect I stand my ground.... the topping lift has the mechanical advantage
over the vang.

CM


|
| Fresh Breezes- Doug King
|

Doug,

Can you say "GIN POLE?" That is what the boom becomes with a topping
lift Hoist.

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

"Capt. Mooron" wrote

Quit toying with the damn boom.... look think of it this way... how
many
lifting devices utilize a support located under the boom at less
than 25% of
the boom length? NONE!

Wrong, kanook.
Have you never seen an engine crane?
A bascule type draw bridge?
Any hydraulic crane with the boom out?
An excavator?

need more?

Scotty