Sail Aerodynamics
 

This link was posted recently to a racing discussion

http://www.wb-sails.fi/news/470StreamAnim/index.htm#

Not sure how useful this is, but the pictures are cool. One of the
things I found interesting was the vertical difference in air flow,
and the difference in pressure distribution between the main & jib. On
the jib, the max pressure differential is much further forward.

Also if you look at the photos of the sail, they are much flatter than
often said to be ideal (there is no reference to wind speed, it might
be light air) and the drafts are aft. Also it shows a vortex off the
head of the jib.... now the question is, does a frac rig benefit
because the mainsail supresses the jib's tip vortex, or does the jib
vortex hurt the drive of the mainsail?

This is kind of theoretical, I wich I could actually go sailing but
right now everything is covered in snow & ice. Maybe later this
week.....

Fresh Breezes- Doug King

Sail Aerodynamics
 

DSK wrote:

This link was posted recently to a racing discussion

http://www.wb-sails.fi/news/470StreamAnim/index.htm#

Not sure how useful this is, but the pictures are cool. One of the
things I found interesting was the vertical difference in air flow,
and the difference in pressure distribution between the main & jib. On
the jib, the max pressure differential is much further forward.

I would have thought you would have known that. Never seen the main luff
rising to windward? It's due to the slot and the mast.

Also if you look at the photos of the sail, they are much flatter than
often said to be ideal (there is no reference to wind speed, it might
be light air) and the drafts are aft.

Yes they are flat, but these sails are trimmed for very very close
sailing -probably much closer than most of the nags sailed here could
achieve. Note the relative narrowness of the slot and the shape of the
battens. Note also that the apparent wind is 22 degrees whereas at 33
degrees we used a slightly fuller set (in even lighter air). The draft
is exaggerated by the camera angle in our shot whose purpose was to
identify the max draft position. Note that this moves forward up the
main as the CFD suggest it should). (Can you see the similar lower
batten wrinkes low down that Booby (and you?) complained about).

http://community.webshots.com/photo/...56514380nkBEsE
http://www.wb-sails.fi/news/470StreamAnim/index.htm#


Also it shows a vortex off the
head of the jib.... now the question is, does a frac rig benefit
because the mainsail supresses the jib's tip vortex, or does the jib
vortex hurt the drive of the mainsail?

Yes, the benefit is from the greater adjustability of the frac. rig.

Cheers

Sail Aerodynamics
 

MC wrote:


....Never seen the main luff
rising to windward? It's due to the slot and the mast.

Why, no, Navvie, I never have!

Are you *sure* that a luff (or 'bubble' as it's often called) along the main
luff is due to the slot & the mast? Who'd a thunk it?



Also if you look at the photos of the sail, they are much flatter than
often said to be ideal (there is no reference to wind speed, it might
be light air) and the drafts are aft.

Yes they are flat, but these sails are trimmed for very very close
sailing -probably much closer than most of the nags sailed here could
achieve.

If that's true, then why are the photos of your mainsail, that you're so
proud of, not shaped at all like the ones in the sailmakers web site?

...Note also that the apparent wind is 22 degrees

Gee, Navvie, do you hold a protractor up to your computer screen?




....Also it shows a vortex off the
head of the jib.... now the question is, does a frac rig benefit
because the mainsail supresses the jib's tip vortex, or does the jib
vortex hurt the drive of the mainsail?

Yes, the benefit is from the greater adjustability of the frac. rig.

And the adjustability has *what* to do with the vortex?

I was hoping that somebody might like to discuss rig tuning & sail trim.
Navvie, you are a font of meaningless, self-congratulatory prattle. And
you're not as funny as Boobsie.

DSK

Sail Aerodynamics
 

does a frac rig benefit
because the mainsail supresses the jib's tip vortex,

no.

or does the jib
vortex hurt the drive of the mainsail?

yes.


Yes, the benefit is from the greater adjustability of the frac. rig.

lots of advantages to a frac rig, but suppression of the tip vortex of the jib
is not one of them.

Sail Aerodynamics
 

JAXAshby wrote:
does a frac rig benefit

because the mainsail supresses the jib's tip vortex,


no.


or does the jib
vortex hurt the drive of the mainsail?


yes.


Yes, the benefit is from the greater adjustability of the frac. rig.


lots of advantages to a frac rig, but suppression of the tip vortex of the jib
is not one of them.


Shh, it'll take Doug quite some time to figure this all out.

Cheers

Sail Aerodynamics
 

DSK wrote:

MC wrote:


....Never seen the main luff
rising to windward? It's due to the slot and the mast.


Why, no, Navvie, I never have!

Are you *sure* that a luff (or 'bubble' as it's often called) along the main
luff is due to the slot & the mast? Who'd a thunk it?


Yep a bubble in the luff -if that's what you like to call it. Now do you
realize what it is?



Also if you look at the photos of the sail, they are much flatter than
often said to be ideal (there is no reference to wind speed, it might
be light air) and the drafts are aft.

Yes they are flat, but these sails are trimmed for very very close
sailing -probably much closer than most of the nags sailed here could
achieve.


If that's true, then why are the photos of your mainsail, that you're so
proud of, not shaped at all like the ones in the sailmakers web site?


Look at the picture legends. Mine 33 degrees 5k ap. Theirs 22 degrees 16
knots. Are you blind or just so desperate to score one point you drop
the ball (again)?


...Note also that the apparent wind is 22 degrees


Gee, Navvie, do you hold a protractor up to your computer screen?



No but I can read the picture legend and understand what it says.
You are a such clown when it comes to the fine points of sail trim Doug!

Cheers MC

Sail Aerodynamics
 

DSK wrote:



Yes, the benefit is from the greater adjustability of the frac. rig.


And the adjustability has *what* to do with the vortex?


You mean you don't know? Good lord!

I was hoping that somebody might like to discuss rig tuning & sail trim.
Navvie, you are a font of meaningless, self-congratulatory prattle. And
you're not as funny as Boobsie.

Bwhahhahahaha. You are soooooooooooo jealous.

Cheers

Sail Aerodynamics
 

"MC" wrote in message
...


JAXAshby wrote:
does a frac rig benefit

because the mainsail supresses the jib's tip vortex,


no.


or does the jib
vortex hurt the drive of the mainsail?


yes.


Yes, the benefit is from the greater adjustability of the frac. rig.


lots of advantages to a frac rig, but suppression of the tip vortex of
the jib
is not one of them.


Shh, it'll take Doug quite some time to figure this all out.


MC,

I'm usually quite lost (at sea) during your discussions with Doug.
However, I never expected to see you depend on Jax for support. Well,
now I know!




Regards


Donal
--

Sail Aerodynamics
 

Donal wrote:

"MC" wrote in message
...


JAXAshby wrote:

does a frac rig benefit


because the mainsail supresses the jib's tip vortex,


no.



or does the jib
vortex hurt the drive of the mainsail?


yes.



Yes, the benefit is from the greater adjustability of the frac. rig.


lots of advantages to a frac rig, but suppression of the tip vortex of

the jib

is not one of them.


Shh, it'll take Doug quite some time to figure this all out.



MC,

I'm usually quite lost (at sea) during your discussions with Doug.
However, I never expected to see you depend on Jax for support. Well,
now I know!


You miss the point. Jax is correct on this one and I am giving him
credit for that. Just 'cos he's Jax doesn't mean he's always wrong!

Cheers

Sail Aerodynamics
 

Donal wrote:
I'm usually quite lost (at sea) during your discussions with Doug.
However, I never expected to see you depend on Jax for support.


He'll take whatever he can get, first it was Bubbles tremendous
expertise he relied on, now it's Jax.



MC wrote:
You miss the point. Jax is correct on this one and I am giving him
credit for that. Just 'cos he's Jax doesn't mean he's always wrong!


But he did not answer either question meaningfully.

DSK

Sail Aerodynamics
 

what word didn't you understand, dougie?

But he did not answer either question meaningfully.

DSK

Sail Aerodynamics
 

JAXAshby wrote:

what word didn't you understand,

The "yes" and "no" answers to essay questions.

BTW got any investment advice? We're all ears, and I'm sure your new pal
MC would like some pointers.

DSK

Sail Aerodynamics
 

you asked a question, and yes or no were the correct answers.

as far as investment advice goes I can only repeat the advice of Will Rogers.
"Buy and when the stock goes up, sell. If it doesn't go up, don't buy".

JAXAshby wrote:

what word didn't you understand,

The "yes" and "no" answers to essay questions.

BTW got any investment advice? We're all ears, and I'm sure your new pal
MC would like some pointers.

DSK

Sail Aerodynamics
 

JAXAshby wrote:
you asked a question,

No, I asked at least two. I knew you were math-impaired, but I didn't
realize that you could not count to two!

.... and yes or no were the correct answers.

If that is true (seems unlikely in view of your knowledge level) then
please explain why.

DSK

Sail Aerodynamics
 

dougie, the tip vortex comes about because the pressure on the windward side of
the sail is greater than on the leeward side. The greater pressure tries to
make it to the lower pressure. the air on the heavy side rolls over the aft
edge of the sail in the easiest possible manner, which includes going up as
well as back. This makes for the vortex as the aft edge of the sail meets the
forward edge.

having a main sail downwind of the jib does not cause the jib airflow to stop
trying to go from high pressure to low pressure. The vortex generated causes
turbulant air from the jib to screw up the airflow across the main. moving the
top of the jib lower than top of the main just causes the jib vortex to hit
more of the main.

okay?


JAXAshby wrote:
you asked a question,

No, I asked at least two. I knew you were math-impaired, but I didn't
realize that you could not count to two!

.... and yes or no were the correct answers.

If that is true (seems unlikely in view of your knowledge level) then
please explain why.

DSK

Sail Aerodynamics
 

JAXAshby wrote:

dougie, the tip vortex comes about because the pressure on the windward side of
the sail is greater than on the leeward side. The greater pressure tries to
make it to the lower pressure. the air on the heavy side rolls over the aft
edge of the sail in the easiest possible manner, which includes going up as
well as back. This makes for the vortex as the aft edge of the sail meets the
forward edge.

A little slower, Jax... Navvie is taking notes...

You have got part of the explanation of tip vortex, so far so good. But if what you
say is all there is, then why are there not a series of vortexes all along the
trailing edge instead of just at the tip? Of course, when the flow is just
starting, that's true, but after flow is established there is just a vortex at the
tip.

Another thing to account for is vertical pressure distribution.





having a main sail downwind of the jib does not cause the jib airflow to stop
trying to go from high pressure to low pressure. The vortex generated causes
turbulant air from the jib to screw up the airflow across the main. moving the
top of the jib lower than top of the main just causes the jib vortex to hit
more of the main.

okay?

But that doesn't answer the earler question... the differential pressure across the
main is going to interfere with (and suppress) the tip vortex from the jib. Got it
so far? That means that energy lost through the jib head tip vortex will be less.

Now, is that energy gain for a frac rig greater or less than the gain a masthead
rig gets from not having the jib head tip vortex disrupting flow across the main?

Folks, I think Jax *might* begin to actually grasp the question this time.... any
bets?

Fresh Breezes- Doug King

Sail Aerodynamics
 

DSK wrote:

JAXAshby wrote:


dougie, the tip vortex comes about because the pressure on the windward side of
the sail is greater than on the leeward side. The greater pressure tries to
make it to the lower pressure. the air on the heavy side rolls over the aft
edge of the sail in the easiest possible manner, which includes going up as
well as back. This makes for the vortex as the aft edge of the sail meets the
forward edge.


A little slower, Jax... Navvie is taking notes...

You have got part of the explanation of tip vortex, so far so good. But if what you
say is all there is, then why are there not a series of vortexes all along the
trailing edge instead of just at the tip? Of course, when the flow is just
starting, that's true, but after flow is established there is just a vortex at the
tip.

Another thing to account for is vertical pressure distribution.





having a main sail downwind of the jib does not cause the jib airflow to stop
trying to go from high pressure to low pressure. The vortex generated causes
turbulant air from the jib to screw up the airflow across the main. moving the
top of the jib lower than top of the main just causes the jib vortex to hit
more of the main.

okay?


But that doesn't answer the earler question... the differential pressure across the
main is going to interfere with (and suppress) the tip vortex from the jib. Got it
so far? That means that energy lost through the jib head tip vortex will be less.

Now, is that energy gain for a frac rig greater or less than the gain a masthead
rig gets from not having the jib head tip vortex disrupting flow across the main?

Folks, I think Jax *might* begin to actually grasp the question this time.... any
bets?


I'll bet you haven't got a clue what you are talking about. It was you
who didn't know where the greatest pressure on the main was wasn't it?
Your earlier comments also show you don't even begin to understand the
relationship between constructing an effective eliptical planaform by
controlling draft position.

Cheers

Sail Aerodynamics
 

MC wrote:


I'll bet you haven't got a clue what you are talking about.

If I haven't got a clue, then you should be able to easily show the mistakes in my post
above.


It was you
who didn't know where the greatest pressure on the main was wasn't it?

where did you get that idea? In any event, pressure distribution will be different under
different conditions.


Your earlier comments also show you don't even begin to understand the
relationship between constructing an effective eliptical planaform by
controlling draft position.

Maybe not. Go ahead and explain it clearly.

Oh, and fully answer the question from the above post.

DSK

Sail Aerodynamics
 

DSK wrote:

MC wrote:


I'll bet you haven't got a clue what you are talking about.


If I haven't got a clue, then you should be able to easily show the mistakes in my post
above.



It was you
who didn't know where the greatest pressure on the main was wasn't it?


where did you get that idea? In any event, pressure distribution will be different under
different conditions.


Your earlier comments also show you don't even begin to understand the
relationship between constructing an effective eliptical planaform by
controlling draft position.


Maybe not. Go ahead and explain it clearly.

Oh, and fully answer the question from the above post.


I will if you'll admit you don't know why the vortex forms


Cheers

Sail Aerodynamics
 

DSK wrote:

MC wrote:


I'll bet you haven't got a clue what you are talking about.


If I haven't got a clue, then you should be able to easily show the mistakes in my post
above.



Your mistake is you you thinking you had posted anything except a series
of questions. In fact, this is correct in so far as it shows that you
don't know what you are talking about -as I pointed out.

Cheers

Sail Aerodynamics
 

MC wrote:

Your mistake is you you thinking you had posted anything except a series
of questions.

Oh? Let's see, did I post a bit of further explanation after Jax fell
short on tip vortex? It's in my "sent" file. Or did it go right over
your head?


... In fact, this is correct in so far as it shows that you
don't know what you are talking about -as I pointed out.

OK, in that case prove it. You explain 1- how tip vortex forms 2- your
calculations as to which represents a greater energy loss... flow
effects across the upper main from a frac jib, or combined tip vortex
from main + masthead jib.

If you can't explain it clearly, then you're bluffing. There is no third
alternative, is there?

DSK

Sail Aerodynamics
 

dougies, go back and re-read it until you understand about vertices (not
vortexes, but vortices).

"vertical pressure distribution"? dougies, dougies, dougies, the term is
"spanwise loading". Now, go back to study hall.

JAXAshby wrote:

dougie, the tip vortex comes about because the pressure on the windward
side of
the sail is greater than on the leeward side. The greater pressure tries
to
make it to the lower pressure. the air on the heavy side rolls over the
aft
edge of the sail in the easiest possible manner, which includes going up as
well as back. This makes for the vortex as the aft edge of the sail meets
the
forward edge.

A little slower, Jax... Navvie is taking notes...

You have got part of the explanation of tip vortex, so far so good. But if
what you
say is all there is, then why are there not a series of vortexes all along
the
trailing edge instead of just at the tip? Of course, when the flow is just
starting, that's true, but after flow is established there is just a vortex
at the
tip.

Another thing to account for is vertical pressure distribution.





having a main sail downwind of the jib does not cause the jib airflow to
stop
trying to go from high pressure to low pressure. The vortex generated
causes
turbulant air from the jib to screw up the airflow across the main. moving
the
top of the jib lower than top of the main just causes the jib vortex to hit
more of the main.

okay?

But that doesn't answer the earler question... the differential pressure
across the
main is going to interfere with (and suppress) the tip vortex from the jib.
Got it
so far? That means that energy lost through the jib head tip vortex will be
less.

Now, is that energy gain for a frac rig greater or less than the gain a
masthead
rig gets from not having the jib head tip vortex disrupting flow across the
main?

Folks, I think Jax *might* begin to actually grasp the question this time....
any
bets?

Fresh Breezes- Doug King

Sail Aerodynamics
 

dougies, what you are saying is bull****, pure and simple.

But that doesn't answer the earler question... the differential pressure
across the
main is going to interfere with (and suppress) the tip vortex from the jib.
Got it
so far? That means that energy lost through the jib head tip vortex will be
less.

Now, is that energy gain for a frac rig greater or less than the gain a
masthead
rig gets from not having the jib head tip vortex disrupting flow across the
main?

Folks, I think Jax *might* begin to actually grasp the question this time....
any
bets?

Fresh Breezes- Doug King

Sail Aerodynamics
 

Let's see, did I post a bit of further explanation after Jax fell
short on tip vortex? It's in my "sent" file. Or did it go right over
your head?


don't bother, dougies. what you posted in bull**** lifted from some writer who
didn't know any more about vortices that you do.

(do keep in mind, dougies, that *neither* you nor he knew that the plural of
vortex is votices)

Sail Aerodynamics
 

Let's see, did I post a bit of further explanation after Jax fell
short on tip vortex? It's in my "sent" file. Or did it go right over
your head?


JAXAshby wrote:
don't bother, dougies. what you posted in bull**** lifted from some writer who
didn't know any more about vortices that you do.

In other words, you don't know the answer and now you're running away.
But why are you running away so soon, Jax? Losing confidence in your
MENSA power?


(do keep in mind, dougies, that *neither* you nor he knew that the plural of
vortex is votices)

Both 'vortexes' and 'vortices' are listed as correct in my dictionary.
But when you don't really know anything about a subject, you quibble as
strongly as you can (which in this case, ain't very)

DSK

Sail Aerodynamics
 

dougies, I gave you the answer. read it again. And again, if you need to.
And again. And again.

Let's see, did I post a bit of further explanation after Jax fell
short on tip vortex? It's in my "sent" file. Or did it go right over
your head?


JAXAshby wrote:
don't bother, dougies. what you posted in bull**** lifted from some writer
who
didn't know any more about vortices that you do.

In other words, you don't know the answer and now you're running away.
But why are you running away so soon, Jax? Losing confidence in your
MENSA power?


(do keep in mind, dougies, that *neither* you nor he knew that the plural
of
vortex is votices)

Both 'vortexes' and 'vortices' are listed as correct in my dictionary.
But when you don't really know anything about a subject, you quibble as
strongly as you can (which in this case, ain't very)

DSK

Sail Aerodynamics
 

DSK wrote:



MC wrote:


Your mistake is you you thinking you had posted anything except a
series of questions.


Oh? Let's see, did I post a bit of further explanation after Jax fell
short on tip vortex? It's in my "sent" file. Or did it go right over
your head?


... In fact, this is correct in so far as it shows that you don't know
what you are talking about -as I pointed out.


OK, in that case prove it. You explain 1- how tip vortex forms 2- your
calculations as to which represents a greater energy loss... flow
effects across the upper main from a frac jib, or combined tip vortex
from main + masthead jib.

If you can't explain it clearly, then you're bluffing. There is no third
alternative, is there?


There is. That it would be a complete waste of my time trying to post
something you do not have the education to understand. Thus your post is
just another troll by you that is neither clever not amusing to reply
to. As for the answers to these questions #1 has already been posted by
Jax and others many times (but you didn't seem to understand it) and #2
has no answer unless you define the exact masthead rig and fractional
rig for comparison. If you wanted to enage your pitiful intellect for
just a second you might wonder why all the rig test show that optimal AC
genoa heads are near masthead. Pay me the money you owe me and I'll even
have student here run it in our advanced yacht sail design wind tunnel
facility for free for you.

Cheers

Sail Aerodynamics
 

JAXAshby wrote:

you asked a question, and yes or no were the correct answers.

as far as investment advice goes I can only repeat the advice of Will Rogers.
"Buy and when the stock goes up, sell. If it doesn't go up, don't buy".


Good lord he really walked into that one. I almsot head his nose squash!

LOL

Cheers

Sail Aerodynamics
 

DSK wrote:



(do keep in mind, dougies, that *neither* you nor he knew that the
plural of
vortex is votices)


Both 'vortexes' and 'vortices' are listed as correct in my dictionary.
But when you don't really know anything about a subject, you quibble as
strongly as you can (which in this case, ain't very)


Which just goes to show how those of little education can slaughter a
perfectly good language -in my opinion of course.

Cheers

Sail Aerodynamics
 

JAXAshby wrote:
dougies, I gave you the answer. read it again. And again, if you need to.
And again. And again.

Slow dow, Jax, you're backpeddling so fast you're almost out of sight

Wouldn't it be easier to be honest... just admit you don't have a clue.
You'll feel better and your therapist will be proud of you.

DSK

Sail Aerodynamics
 

OK, in that case prove it. You explain 1- how tip vortex forms 2- your
calculations as to which represents a greater energy loss... flow
effects across the upper main from a frac jib, or combined tip vortex
from main + masthead jib.

If you can't explain it clearly, then you're bluffing. There is no
third alternative, is there?


MC wrote:
There is. That it would be a complete waste of my time trying to post
something you do not have the education to understand.

In other words, it's #2...


.... As for the answers to these questions #1 has already been posted by
Jax

Umm... no. I asked "Of A or B, which is better" and Jax said "yes and no."

... and others

Like who?

... many times

Golly, you can't count either.

... and #2
has no answer unless you define the exact masthead rig and fractional
rig for comparison.

OK then, what factors would affect which one is better?

...you might wonder why all the rig test show that optimal AC
genoa heads are near masthead.

I had that in mind, but those boats are influenced by measurement rules
also.

.... Pay me the money you owe me

You got that backwards too... par for the course.

.....and I'll even
have student here run it in our advanced yacht sail design wind tunnel
facility for free for you.

Oh boy... will you really do that? Put it on the list for right after
they run a simulation of a wave approaching a hull from astern to show
how the transom keeps a wave out... maybe they'll explain 'reserve
bouyancy'... right after they finish laughing...

DSK

Sail Aerodynamics
 

According to the world of Doug:

Oh boy... will you really do that? Put it on the list for right after
they run a simulation of a wave approaching a hull from astern to show
how the transom keeps a wave out...

So, now we know you have never ever sailed offshore in a big sea. Open
transoms are not generally acceptable for really just one reason Doug,
even with no difference in 'buoyancy'. Can you really not imagine a sea
overtaking a running boat? The stern really doesn't rise immediately you
know! In some cases it even goes over the transom and can hit the helm
and even companion washboards. What on earth do you think stops it?
You've got Adlard Coles Heavy Weather right? Have a look at the boat
being overtaken by a wave. What a typical know it all dinghy sailor you
are.

Cheers

Sail Aerodynamics
 

read it again, dougie. And again, if need be. And again. And again. And
again ...

JAXAshby wrote:
dougies, I gave you the answer. read it again. And again, if you need to.

And again. And again.

Slow dow, Jax, you're backpeddling so fast you're almost out of sight

Wouldn't it be easier to be honest... just admit you don't have a clue.
You'll feel better and your therapist will be proud of you.

DSK

Sail Aerodynamics
 

He won't get it. He'ss incapable of original thought and his
comprehension suffers accordingly.

Cheers

JAXAshby wrote:

read it again, dougie. And again, if need be. And again. And again. And
again ...


JAXAshby wrote:

dougies, I gave you the answer. read it again. And again, if you need to.

And again. And again.

Slow dow, Jax, you're backpeddling so fast you're almost out of sight

Wouldn't it be easier to be honest... just admit you don't have a clue.
You'll feel better and your therapist will be proud of you.

DSK

Sail Aerodynamics
 

DSK wrote:


OK, in that case prove it. You explain 1- how tip vortex forms 2-
your calculations as to which represents a greater energy loss...
flow effects across the upper main from a frac jib, or combined tip
vortex from main + masthead jib.

If you can't explain it clearly, then you're bluffing. There is no
third alternative, is there?


MC wrote:
There is. That it would be a complete waste of my time trying to post
something you do not have the education to understand.


In other words, it's #2...

Nope, its exactly as I wrote. I won't waste my time explain any
complicated problems to someone who is incapable of undertstanding them.
That's why I only try to simplify a few thing that you might begin to
get the idea. Of course I'm probably wasting my time with a bigot.

Cheers

Sail Aerodynamics
 

DSK wrote:



... and #2 has no answer unless you define the exact masthead rig and
fractional rig for comparison.


OK then, what factors would affect which one is better?


Rig geometry of course! This reminds me of children who are too
lazy/stupid to frame a question properly and don't really want to know
the answer but just get attention. They just keep saying "But why..."

Cheers

Sail Aerodynamics
 

MC wrote:
So, now we know you have never ever sailed offshore in a big sea.

Sure, whatever you say. You're as right about this as you are about
aerodynamics... oh wait, you haven't said anything substantive about
aerodynamics, in fact you are vigorously dodging any & all questions...

..... Open
transoms are not generally acceptable for really just one reason Doug,

What you mean to say is that open transoms are not acceptable to _you_.
Oddly enough many others have sailed lots of sea miles with them. So
your comments about how terrible they are show your ownlack of
experience and comprehension.


.... What a typical know it all dinghy sailor you
are.

This thread is following the classic pattern... MC bluffs, he blunders,
he dodges & prevaricates... then he starts with insults. It becomes
obvious that he can't answer the question. Does this pattern fulfill a
psychological need for you, Navvie? How many times will you be driven to
repeat it?

DSK

Sail Aerodynamics
 

OK then, what factors would affect which one is better?


MC wrote:
Rig geometry of course!


Now we are getting somewhere.

What rig geometery would favor a frac rig (remembering the issue of jib
head tip vortex)? Would aspect ratio be significant (again, just a
reminder, jib head tip vortex)? How about the head angle of each sail
respectively?


... This reminds me of children who are too
lazy/stupid to frame a question properly and don't really want to know
the answer but just get attention. They just keep saying "But why..."

So, even your toddlers are asking you questions that you don't know the
answer to?

All you have to do MC is supply a coherent answer to the question.

DSK

Sail Aerodynamics
 

oh wait, you haven't said anything substantive about
aerodynamics,

but I did. I also said you had read a single book or article written by a guy
who didn't even know that the plural of vortex is votices.

Sail Aerodynamics
 

What rig geometery would favor a frac rig (remembering the issue of jib
head tip vortex)?

in the context of jib tip vortices, a masthead rig would be better.

Would aspect ratio be significant (again, just a
reminder, jib head tip vortex)?

Of course.

How about the head angle of each sail
respectively?

WTF are you talking about?

dougies, give it up for the cripes sakes. you read a single article by a
numskull about vortices and now you are trying to play expert. Go read a few
dozen more books. A good start would be check a few of the books offered by
the EAA, mostly decent books written for the amateur.