Capt. Mooron wrote:
it's an auxiliary diesel.. 30 HP!

???
What is?

.... The vang holds the boom down not up...

Therein lies your error. A solid vang holds the boom up and down.


yes it has the capacity to hold up a boom up with some weight.... but that
is not it's primary function.

Why isn't it? That's like saying that because a bridge is designed for
cars to drive over it, it won't hold up a person walking across.



Leverage is required at the end of the boom for lifting. I'm certain you are
familiar with fulcrums?

Yes. I fail to see your point though. If the vang holds the boom up,
then it holds the boom up.

If the vang will hold the boom down under heavy sailing loads, then it
will probably hold at least as much in the opposite direction, nyet?

How much leach tension do you think your boat generates in a good breeze?


Where would you fasten the mainsheet to the boom... generally it's 50% of
the length or more. Look where the vang is... at what 15%?

Depends.

It's not a relevant issue though. Wherever the boom vang is attached, if
it will stand up to the load then it will... umm... stand up to the
load. If not, then it wasn't strong enough to begin with and that's true
whether it's a solid vang or not.

|
| A *real* solid vang (and boom) will fulfill all the functions of a
| topping lift, except as an emergency backstay replacement. I've seen a
| lot that wouldn't, but I don't like them either.

No Way Doug!! No for all the tea in China. The engineering is out to lunch
for such a claim.

Actually the engineering is quite sound. If you have problems with vangs
breaking and booms folding up, then that suggests that your engineering
needs a little more beef and less cheese.

Fresh Breezes- Doug King

Doug,

Your Bridge example is WRONG. Those cables hanging down are for
suspension. Not compression. I think you can remember the Tacoma Narrows
Bridge when the wind got under it. IT FALL DOWN GO KAPLUNK!

OT

"DSK" wrote in message

| Yes. I fail to see your point though. If the vang holds the boom up,
| then it holds the boom up.
|
| If the vang will hold the boom down under heavy sailing loads, then it
| will probably hold at least as much in the opposite direction, nyet?

No Doug! No No No!.... look the vang may be able to hold the stresses on a
sail "down"... but it will never hold the stresses of a weight at the end of
the boom "UP". The leverage just isn't there. This is not a hydraulic arm on
an excavator! If it were the vang would be massive ... require an engine to
power the compressor and be attached to the end of the boom.

Look..... I can understand where your assumptions are based but I'm
thinking you have not taken into consideration the engineering incorporated
into the vang and it's intended use. If you have 10,000 lbs of pressure on
the main only a fraction of that force will be utilized to incur lift on the
boom. The vang is not holding down the entire pressure placed on the main.

For using the boom as a lifting device.... you will stress the vang unduly
with a set-up located that far back on the load arm. It's not designed for
that. A topping lift to the end of the boom requires much less force to hold
the boom level on a lift than the stresses placed on a vang that is located
at 15% of the load arm length. I don't care if it's a 1/2" I Channel carbon
steel beam for a boom! We are not discussing boom failure here.... we are
discussing load bearing to the vang.

I await your rebuttal... :-)

CM

| If the vang will hold the boom down under heavy sailing loads, then it
| will probably hold at least as much in the opposite direction, nyet?

Capt. Mooron wrote:
No Doug! No No No!.... look the vang may be able to hold the stresses on a
sail "down"... but it will never hold the stresses of a weight at the end of
the boom "UP".

Why not? If the boom can take the torsion in one direction, then unless
it is a very weird asymmetric structure, then it will take the same in
the opposite direction.


... The leverage just isn't there.

Sure it is. It's exactly the same in both directions.

What I'm saying is the same as saying if you can stand on a beam (let's
say a 2x6) between two sawhorses, and it doesn't break, then you can
turn the beam over and still stand on it. You're saying that it doesn't
work that way, if the beam doesn't break one way then it will definitely
break the other...

.... This is not a hydraulic arm on
an excavator! If it were the vang would be massive ... require an engine to
power the compressor and be attached to the end of the boom.

The max forces are limited by the righting moment of the boat. On a 30
footer, it doesn't need to be that massive. On bigger boats... take a
look at the vangs on IACC racers...


Look..... I can understand where your assumptions are based but I'm
thinking you have not taken into consideration the engineering incorporated
into the vang and it's intended use.

Actually, I have. It's not that complicated. Try drawing out a diagram
of moments. If you need a refresher
http://www2.umist.ac.uk/construction...xp/sfbmdex.htm


... If you have 10,000 lbs of pressure on
the main only a fraction of that force will be utilized to incur lift on the
boom. The vang is not holding down the entire pressure placed on the main.

No, it isn't... but it is holding down 100% of the leach tension, which
is very large. It also takes all the load of the mainsheet when hauled
in tight to go to windward. If it doesn't break when you honk down on an
8:1 purchase, then it should hold at least 8X your honking strength


For using the boom as a lifting device.... you will stress the vang unduly
with a set-up located that far back on the load arm.

???

... It's not designed for
that.

It should be. Anything less would not be safe for sailing IMHO.



I await your rebuttal... :-)

If I give you a re-buttal, then who was the butt in the first place?

Seriously, I'm not saying 'all solid vangs are great for lifting heavy
objects' because many aren't. But then remember Sturgeons Law '90% of
everything is crap' and then tell me why it *shouldn't* be.

Some are. I know that for a fact. And if I had a solid vang that's what
I'd insist on. YMMV

DSK

"DSK" wrote in message

| Why not? If the boom can take the torsion in one direction, then unless
| it is a very weird asymmetric structure, then it will take the same in
| the opposite direction.

This is where you stray from engineering principal... that is not the case
at all nor is it the rule.

| Sure it is. It's exactly the same in both directions.

No Doug... it is most assuredly not the same in both directions if only by
the points of compression
|
| What I'm saying is the same as saying if you can stand on a beam (let's
| say a 2x6) between two sawhorses, and it doesn't break, then you can
| turn the beam over and still stand on it. You're saying that it doesn't
| work that way, if the beam doesn't break one way then it will definitely
| break the other...

That's not at all what I said and again you are attempting to introduce the
boom as a factor... that is not good methodology for what we are discussing
here.... forget the boom or assume it indestrutructable and unbendable.|

| The max forces are limited by the righting moment of the boat. On a 30
| footer, it doesn't need to be that massive. On bigger boats... take a
| look at the vangs on IACC racers...

Nobody is discussing righting moment here Doug... we are discussing the
ability of basic mathematics in regards to the placement of the vang and the
loads you expect it to encounter.


| Actually, I have. It's not that complicated. Try drawing out a diagram
| of moments. If you need a refresher
|
http://www2.umist.ac.uk/construction...xp/sfbmdex.htm
|

No Doug... it's not that I refuse to seek knowledge but this time you had
better be able to logically explain your theory to me without a jaxxian
reflex to google proof that may or may not have bearing on what we are
discussing.



| No, it isn't... but it is holding down 100% of the leach tension, which
| is very large. It also takes all the load of the mainsheet when hauled
| in tight to go to windward. If it doesn't break when you honk down on an
| 8:1 purchase, then it should hold at least 8X your honking strength

No Doug... it is most certainly NOT holding down 100% of the leech
tension... that load is divided with a bigger factor attributed to the
mainsheet.
|
|
| For using the boom as a lifting device.... you will stress the vang
unduly
| with a set-up located that far back on the load arm.
|
| ???

Well come on now Doug.... it's basic common sense engineering principal!

| ... It's not designed for
| that.
|
| It should be. Anything less would not be safe for sailing IMHO.

No it's not... it's designed as a VANG!


CM

| Why not? If the boom can take the torsion in one direction, then unless
| it is a very weird asymmetric structure, then it will take the same in
| the opposite direction.

Capt. Mooron wrote:
This is where you stray from engineering principal... that is not the case
at all nor is it the rule.

Oh? Are you saying that a symmetric structural member is stronger one
way than the other? If you nail a board into a frame, you have to be
careful to put it label side up or something?




| Sure it is. It's exactly the same in both directions.

No Doug... it is most assuredly not the same in both directions if only by
the points of compression

Well, go explain that to Newton. He had a little to say on the subject.

.... forget the boom or assume it indestrutructable and unbendable.

OK


| The max forces are limited by the righting moment of the boat. On a 30
| footer, it doesn't need to be that massive. On bigger boats... take a
| look at the vangs on IACC racers...

Nobody is discussing righting moment here Doug...

Well, if we're not discussing the strength of the boom, nor the limit of
force on the whole system, then the only thing to complain about it the
compressive strength of the vang itself (which with a proper one, should
not be an issue) or the strength of the connections between vang, mast,
& boom.

If you break the gooseneck, then it probably wasn't strong enough
anyway. The vang connections take greater strain than the gooseneck (due
to the greater leverage) and thus they have to be stronger yet. So that
rules them out.

Now all you're left with is the strength of the vang itself.

How about a hydraulic cylinder? Some are. How about a very thick solid
SS turnbuckle with machine threads? Some are. That leaves the little
fiberglass rod ones (which I agree are not going to hold up much load)
and the spring loaded locking kind. I suggest you take a look at the
specs on several and see if you can't find one or two that look strong
enough to hold up a substantial load. They're there.



... we are discussing the
ability of basic mathematics in regards to the placement of the vang and the
loads you expect it to encounter.

Not really. You were trying to obfuscate the basic point that a vang
needs to be strong enough to stand up to hard sailing, and if it will do
that, it is almost certainly strong enough the other way too (unless
it's one of those wimpy hen-pecked little fiberglass rod ones).

| For using the boom as a lifting device.... you will stress the vang
unduly
| with a set-up located that far back on the load arm.
|
| ???

Well come on now Doug.... it's basic common sense engineering principal!

It can't be that basic, I have no clue what you're talking about.
Doesn't seem to pertain to vangs, though.


| ... It's not designed for
| that.
|
| It should be. Anything less would not be safe for sailing IMHO.

No it's not... it's designed as a VANG!

I guess a tackle employed as a vang would not be strong enough to use
for anything else?

I do one thing... you can't push a rope.

DSK

Doug,

I mentioned early in this discussion that with a topping lift hoisting
boom, the boom only positions the location of hoist. There is very, very
little force on the boom. The hoist is on the topping lift.

Mooran re-stated this.

You are the one insisting the force is the same on the end of the boom
supported on the other end by a Vang and a gooseneck. We say BS and sign
off.

Ole Thom

Hi Thom

Actually the force is revealed as compression on the boom in the topping
lift case and bending in the vang lifgt case. I wonder how many booms
Dog has bent lifting loads that way??? In our case, the solid vang only
serves to hold the boom up is the sail is dropped (and no topping lift
used). Just another thought, do you suppose Doug thinks that compressive
and tensile strengths are the same in symmetrical structures???

Cheers

Thom Stewart wrote:

Doug,

I mentioned early in this discussion that with a topping lift hoisting
boom, the boom only positions the location of hoist. There is very, very
little force on the boom. The hoist is on the topping lift.

Mooran re-stated this.

You are the one insisting the force is the same on the end of the boom
supported on the other end by a Vang and a gooseneck. We say BS and sign
off.

Ole Thom

Thom Stewart wrote:
Doug,

I mentioned early in this discussion that with a topping lift hoisting
boom, the boom only positions the location of hoist. There is very, very
little force on the boom. The hoist is on the topping lift.

Mooran re-stated this.

You are the one insisting the force is the same on the end of the boom
supported on the other end by a Vang and a gooseneck. We say BS and sign
off.

In other words, you're saying that 100# on the end of the boom supported
by a topping lift is not the same as 100# on the end of the boom
supported by a solid vang?

OK but I'm a little confused... how does the weight know the difference?

DSK