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wing mast -v- Bethwaite "wing mast" #79310
07/06/06 10:16 AM
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Glenn_Brown Offline OP
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I see that the Infusion and Capricorn have "wing masts", which appear to be modified teardrop sections. These appear to be quite different from what Bethwaite refered to as a "wing mast" in his 1993 book High Performance Sailing.

Bethwaite's wing mast is a laminar flow section with a square back just after it starts to narrow. This design neatly minimizes the inevitable separation bubbles behind the mast on each side of the sail, was developed in the wind tunnel, and improved the power of the main by 10+ percent compared to a conventional mast. It also leads to even better improvements in extremely light air (<3kts).

So, does anyone know if the Capricorn and Infusion "wing masts" are designed to perform similarly? Or are they simply more streamlined versions of the conventional teardrop? If not, why does no one use the Bethwaite design on a Cat?

-- Have You Seen This? --
Re: wing mast -v- Bethwaite "wing mast" [Re: Glenn_Brown] #79311
07/06/06 10:38 AM
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Jake Offline
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Does Bethwaite use Bethwaite's design? I thought most of the Aussie 18 skiff masts were round? I'm quite sure they don't rotate either.


Jake Kohl
Re: wing mast -v- Bethwaite "wing mast" [Re: Jake] #79312
07/06/06 01:01 PM
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Wouter Offline
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Good point Jake !

Another bethwaite design, the 49-er, doesn't have a rotatin squareback mast either !

with respect to the post made by Glenn


Quote

I see that the Infusion and Capricorn have "wing masts", which appear to be modified teardrop sections.



Not really, the wing masts are seriously different from a teardrop masts. It is not even a simple modification to make a teardrops shape into a wingmast shape.


Quote

and improved the power of the main by 10+ percent compared to a conventional mast.


I'm quite sure the "conventional" mast here is simply a round tube, nothing more. The difference between a wingmast a la Capricorn and the squareback will be a whole lot small is any difference can be measured.


Quote

It also leads to even better improvements in extremely light air (<3kts).



Less then 3 knots is VERY little wind. And the squareback was optimisation for these conditions, I think Bethwaite even wrote that. For the high wind ranges the intended effects can be alot less significant.


Quote

So, does anyone know if the Capricorn and Infusion "wing masts" are designed to perform similarly?


I have a wingmast myself (Taipan F16) and more and more I believe its attractiveness is far more related to the way you can tune its bending. I'm sure some improved aerodynamics is present as well, but not as the dominant factor.


Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: wing mast -v- Bethwaite "wing mast" [Re: Jake] #79313
07/06/06 01:56 PM
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I believe most skiffs can't have rotating masts due to their narrowness. In order to keep the mast "in the boat", they need to have spreaders on their lower shrouds which make mast rotation virtually impossible. Also, they have to carry considerably higher rig tensions than cats.

sm

Re: wing mast -v- Bethwaite "wing mast" [Re: srm] #79314
07/06/06 05:11 PM
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I believe most skiffs can't have rotating masts due to their narrowness. In order to keep the mast "in the boat", they need to have spreaders on their lower shrouds which make mast rotation virtually impossible. Also, they have to carry considerably higher rig tensions than cats.

sm


Higher rig tension? Why?

All that sounds suspicious to me. I think they're skeered.


Jake Kohl
Re: wing mast -v- Bethwaite "wing mast" [Re: srm] #79315
07/06/06 05:27 PM
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I purchased one of the first Tasars sold in the U.S. and raced it for many years (rig designed primarily by Frank Bethwaite) and it has a rotating mast, full battened mainsail, and roller furling jib. This made it easier to sail the similarly rigged Hobie 18 that I bought new in 1980. The main difference being that it was much larger and heavier and rigid. I cannot think of any reason that any dinghy cannot use the same type of rig proven very effective by the Tasar.

Re: wing mast -v- Bethwaite "wing mast" [Re: Jake] #79316
07/06/06 05:35 PM
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Does Bethwaite use Bethwaite's design? I thought most of the Aussie 18 skiff masts were round? I'm quite sure they don't rotate either.


That may be a rules issue. IIRC the i14's (plus most others) are not allowed rotating masts which is most cases will preclude a wing mast.

Tiger Mike

Re: wing mast -v- Bethwaite "wing mast" [Re: srm] #79317
07/06/06 06:26 PM
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Skiffs like I14s have non-rotating masts with high tension upper AND lower stays.

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Eric Poulsen
A-class USA 203
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Re: wing mast -v- Bethwaite "wing mast" [Re: ejpoulsen] #79318
07/06/06 06:27 PM
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Skiffs like 49ers/29ers have non-rotating masts but achieve good airflow by sleeving the sail around the mast.

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Eric Poulsen
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Re: wing mast -v- Bethwaite "wing mast" [Re: ejpoulsen] #79319
07/06/06 07:12 PM
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A 29er only sleeves the mast down low in the bottom 2' (or so) of the main along with part of the boom and the vang strut. the rest of it is a traditional luff groove hoist with an internal halyard arrangement.


Jake Kohl
Re: wing mast -v- Bethwaite "wing mast" [Re: Jake] #79320
07/06/06 08:48 PM
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The rig tension is basically a function of the force that the rig can generate and the geometry of the shrouds/forestay. The higher up the mast and the farther out the shrouds anchor, the lower the rig tension will be.

Consider an 18ft skiff- basically it generates more force from the rig and the shrouds anchor more inboard as compared to an 18ft beach cat. Suppose the shrouds anchor at 3 or 3-1/2ft out from the mast base- a cat anchors at 4 or 4.25ft. The cat as two guys with 8ft or righting moment. The 18ft skiff has 3 guys on a rack 9 or 10ft from center line, so more righting moment= more rig force so more rig tension.
I believe the skiff uses a smaller mast section and they keep it from deflecting to leeward by locking it with spreaders on the lower shrouds. This requires that the leeward shroud be tensioned as well as the windward shroud.
I'm pretty sure the 18s have hydraulic rig tensioning devices.

Re: wing mast -v- Bethwaite "wing mast" [Re: Jake] #79321
07/06/06 10:20 PM
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Quote
A 29er only sleeves the mast down low in the bottom 2' (or so) of the main along with part of the boom and the vang strut. the rest of it is a traditional luff groove hoist with an internal halyard arrangement.

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Eric Poulsen
A-class USA 203
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Re: wing mast -v- Bethwaite "wing mast" [Re: ejpoulsen] #79322
07/06/06 11:57 PM
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18s don't have restrictions against wing rotating masts. The main thing is no one has spent the money recently to try and get one to work, the current mast is efficient to an extent and capable of handling the huge loads generated. Providing no one else changes their rig design (currently CST Composites supplies the whole fleet) there is no need to change the design. It has been discussed in the bar quite often however.

They also do not have hydraulic rig tensioning devices. All the rig tension comes through a boat breaker, similar to a mainsheet set up on a cat (lots of purchases :P)

Cheerio
T_E

Re: wing mast -v- Bethwaite "wing mast" [Re: srm] #79323
07/07/06 04:19 AM
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What a load of nonsense !

Several classes like the ORMA tris, open60 and even dinghies like the laser vortex and papertiger catamarans have solve the issue of lower spreader shrouds and rotating masts.

Also it is just nonsense to say that a 49-er is experiencing higher rig tensions then say a Inter 20 or tornado catamaran.

Those I-20's (F20's) overhere carry 1:10 mainsheet systems and 1:12 downhaul systems. Any idea what kind of loads that puts on the mast and mast foot.

Even Orange 2 has a rotating wingmast and its mainsheet (leech) tension is 22 tons !

I've sailed both 49-er and now F16's, these baots are very comparable in the way of sailarea and such. I can tell you from experience that my F16 experiences much high platform and rig loads then the 49-er. Beside the 49-er I sail only had 3:1 mainsheet.

Wouter

Last edited by Wouter; 07/07/06 04:31 AM.

Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: wing mast -v- Bethwaite "wing mast" [Re: ejpoulsen] #79324
07/07/06 04:22 AM
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Bethwaite himself writes against sleeving sails around round mast tubes in his book. It doesn't do much as the flow is seperated before it can reach the sleeve. The round curvature in front is just too sudden. That is why the newer catamaran wingmasts all have an elliptical leading egde. Even Bethwaite write so himself

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: wing mast -v- Bethwaite "wing mast" [Re: Team_EvoLv] #79325
07/07/06 04:30 AM
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Quote

All the rig tension comes through a boat breaker, similar to a mainsheet set up on a cat (lots of purchases :P)



The one we had on the 49-er was only 4:1; it could never put more then 200 to 300 kg of tension on the forestay.

My catamaran 7:1 mainsheet however can easily achieve 600 kg forestay tension as my boom is over 2 mtr long and my forestay bridles are only 1.35 mtr in front of the mast. These difference in leverage result in an additional 1.5 magnifying effect. Effectively resulting in a 10:1 boat breaker. I have to have at least 3 mm dyform or 4 mm 1x19 wire on my forestay or risk breaking it.

Try that on a 49-er. (or 4:1 boat breaker)

No really guys. I really don't believe the skiffs have such high rig tensions in comparison to high performance cats.

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: wing mast -v- Bethwaite "wing mast" [Re: srm] #79326
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If it can be made to work on the open 60 mono's with canting keels then it can certainly be made to work on a 18 ft skiff.


Beside on cat the biggest portion of the rig come from the mainsheet and leech tension. Think 2/3rd or more. The skiffs use ram-vangs and rather weak 3:1 mainsheets therefor don't have this component.

That makes a really big difference.

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: wing mast -v- Bethwaite "wing mast" [Re: Glenn_Brown] #79327
07/07/06 05:34 AM
07/07/06 05:34 AM
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Quote
I see that the Infusion and Capricorn have "wing masts", which appear to be modified teardrop sections. These appear to be quite different from what Bethwaite refered to as a "wing mast" in his 1993 book High Performance Sailing.
So, does anyone know if the Capricorn and Infusion "wing masts" are designed to perform similarly? Or are they simply more streamlined versions of the conventional teardrop? If not, why does no one use the Bethwaite design on a Cat?


Those F18 masts are copies of what classes like the C Class, A Class, Dolphin and later the Taipans have been using for a couple of decades. Nothing new here mate. I was racing with a rig like this on my first cat (Dolphin) in 1992.

As mentioned before, some monos do have wing masts like the Tasar, NS14, MG14

The skiffs don't use it because they have previously spent a lot of $$$$ developing their soft tip rigs and to scap everything and start again developing a wing rig which may not work for them and would cost mega $$$$$.... It is just not worth it.

They also need a lot more support at the top of the mast to carry mast head kites with can be up to 3 x the sail area as our kites. Put your cat kite up the top of an unsupported wing mast tip and see how long it takes before you are calling the insurance company.

Quote

Also it is just nonsense to say that a 49-er is experiencing higher rig tensions then say a Inter 20 or tornado catamaran.
Wouter


Bit of repect there Wouter.

Firstly, compare boats of equal size to each other. A super Maxi will have more rig tension than a T. A 49er is 4.9m long ie 16 foot. An 18 footer is 2 foot shorter than a T or I20 however the rig tension is a lot higher.

I have sailed 12s, 14s, 16s and 18s as well as MANY different cats. Rig tension for a skiff is a lot higher. Just have a look at the compression to an 18s mast when they are cranking on the boat breaker to put the fore stay on. We often thought we were going to snap the mast whilst rigging.

Quote
Consider an 18ft skiff- basically it generates more force from the rig and the shrouds anchor more inboard as compared to an 18ft beach cat. Suppose the shrouds anchor at 3 or 3-1/2ft out from the mast base- a cat anchors at 4 or 4.25ft. The cat as two guys with 8ft or righting moment. The 18ft skiff has 3 guys on a rack 9 or 10ft from center line, so more righting moment= more rig force so more rig tension.


Dont forget that a monos weight without crew is balanced over the keel line and with crew, its righting momentom is the weight of only its crew. In an 18s case, it is 3 crew 7.5 feet from the center line. 15 foot wing span I believe now.

A cats righing momentum is the weight of the platform and its rig from the windward side of the leeward board...... plus the crews weight, 8 foot (or just under 10 foot for a T) out from the pivot point.

Looking at this, the cat has a lot more righing momentum and uses the weight of the boat far more efficiently.

Below is a boat breaker about to be put into action to enable geting the forestay on.
[Linked Image]


Re: wing mast -v- Bethwaite "wing mast" [Re: ejpoulsen] #79328
07/07/06 05:46 AM
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Quote
A 29er only sleeves the mast down low in the bottom 2' (or so) of the main along with part of the boom and the vang strut. the rest of it is a traditional luff groove hoist with an internal halyard arrangement.


I designed a 60lb lead bulb and built the aluminum keel fin for one that a friend owns. I can also tell you that the rigging loads, relative to even a 16' cat (don't know of a 15' cat to compare it to), are tiny on the skiff - it's got a 2:1 mainsheet! (and it's plenty of purchase)

This is not the boat with the bulb keel but shows the mainsail / luff groove arrangement.

[Linked Image]
[Linked Image]

Re: wing mast -v- Bethwaite "wing mast" [Re: Wouter] #79329
07/07/06 05:59 AM
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Quote

Beside on cat the biggest portion of the rig come from the mainsheet and leech tension. Think 2/3rd or more. The skiffs use ram-vangs and rather weak 3:1 mainsheets therefor don't have this component.

That makes a really big difference.

Wouter


The majority of tension on a Skiff rig is given whilst rigging. This is constant tension which is in another league to a cat. Nothing realy to brag about so don't get too upset guys.

Secondly, the boom vangs add a lot of downward tension to the boom, therefore large mainsheet loads are not required as it leach tension is already applied. Once again nothing to brag about or be disapointed about, so don't feel you must compete. Fact is fact.

My old Dolphin catamaran had a boom vang and it was amazing how much it took away from main sheet loads.


Re: wing mast -v- Bethwaite "wing mast" [Re: Jake] #79330
07/07/06 06:09 AM
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I can also tell you that the rigging loads, relative to even a 16' cat (don't know of a 15' cat to compare it to), are tiny on the skiff - it's got a 2:1 mainsheet! (and it's plenty of purchase)


Hi Jake,

Don't get confused between rig tension and main sheet loads. The discusion was relating to why Skiffs use round mast sections under intense loads and prebend a opposed to wing masts.

Also, the 29er and 49ers are not skiffs. We will not go to much into that but if you wish to, do a search on Sailing Anarchy.

The 9ers are a far cry from the true skiffs.....

12 footer
[Linked Image]


Re: wing mast -v- Bethwaite "wing mast" [Re: Tornado_ALIVE] #79331
07/07/06 06:14 AM
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12 footer experimenting with an A class rig. It was carring a kite from just above the hounds. The rig has yet to prove itself against the traditional rigs.

[Linked Image]

[Linked Image]


Re: wing mast -v- Bethwaite "wing mast" [Re: Tornado_ALIVE] #79332
07/07/06 06:18 AM
07/07/06 06:18 AM
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Quote

Bit of repect there Wouter.
Firstly, compare boats of equal size to each other.



Okay, I will now compare the 49-er and the Taipan F16 both of which I sailed and rigged often. Both boats are very comparable in their dimensions.

The F16 has higher rig loads during sailing then the 49-er. In the way of leech and luff tensions on the sail it is not even a comparison. The F16 (luff and leech) loads are many times higher. Especially with the large squaretops.

If you compare the 49-er on its trolly and a more conventional boat like the hobie 16 on the beach without the mainsheet tight then the 49-er wins, sure.

I wrote earlier that we never used more then a simple 4:1 boat breaker on the 49-er.


I'm one annoying know-it-all, I admit to that and I'm not even ashamed of it. But don't mistake that for lack of respect. I do respect the skiffies and their designs, I just don't buy all the claims.

Maybe the 18 foot skiff loads are alot higher then say on a F18; I can't judge that as I've only seen a 18 foot skiff in the flesh twice in my life. But the 49-er loads certainly isn't.


Quote

Put your cat kite up the top of an unsupported wing mast tip and see how long it takes before you are calling the insurance company.


That is funny, I actually have an answer to that comment. It took over a year and 170 kg double trapping under spinnaker on a high broad reach to break the Taipan superwing mast that was fitted with a F18 spinnaker that came to 450 mm of the top of the mast. It broke when the mast rotation inverted and the mainsail leech didn't support the top anymore. We were all a bit surprised that the Taipan superwing mast could take such abuse for such a long time.

It is my experience that skiff spinnaker are flown alot more dead downwind then cat spinnakers, their luffs being alot more loose. So I'm not too sure whether a 3 times greater skiff spi actually loads the mast up more then the lot smaller but tighter luffed + more reaching oriented catamaran spinnakers.

I sailed my share of skiffs and all were notoriously difficult to handle on any high broad reaching or reaching. So we mostly did upwind and very deep downwind.

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: wing mast -v- Bethwaite "wing mast" [Re: Tornado_ALIVE] #79333
07/07/06 06:46 AM
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Quote
I can also tell you that the rigging loads, relative to even a 16' cat (don't know of a 15' cat to compare it to), are tiny on the skiff - it's got a 2:1 mainsheet! (and it's plenty of purchase)


Hi Jake,

Don't get confused between rig tension and main sheet loads. The discusion was relating to why Skiffs use round mast sections under intense loads and prebend a opposed to wing masts.

Also, the 29er and 49ers are not skiffs. We will not go to much into that but if you wish to, do a search on Sailing Anarchy.

The 9ers are a far cry from the true skiffs.....

12 footer
[Linked Image]


OK - I'll concede that the vang strut thingy does take away considerably to the sheet loads...perhaps the 29'er is not the greatest comparison

Now I'm really lost however, 29'er not a skiff? Sailing Anarchy as a factual resource? seriously? The thing is a pie tin just like the others...so the rig is a little smaller but does that mean that a Hobie Wave is not a catamaran? - the 9'ers are still the same configuration, bow sprit, main, jib, spinnaker, centerboard, and so unstable in the water that it won't stay upright even without any sails hoisted...how is it not a skiff? Wikipedia even lists the 29'er as an example, among others, of a sailing skiff.


Jake Kohl
Re: wing mast -v- Bethwaite "wing mast" [Re: Wouter] #79334
07/07/06 06:56 AM
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Quote

Quote

Bit of repect there Wouter.
Firstly, compare boats of equal size to each other.



Okay, I will now compare the 49-er and the Taipan F16 both of which I sailed and rigged often. Both boats are very comparable in their dimensions.


I have not rigged or sailed a 49er, however there rig tension is a lot less than a skiff. This includes the shorter 12 footer........ See above 9ers not skiffs.


Quote

I wrote earlier that we never used more then a simple 4:1 boat breaker on the 49-er.

Don't know much about the boat beaker you used on the 49er, however check out the one on the 18 above. firstly you pull as much tension on with the system using the 6 to 1 block set up. This is direct 6:1 down on the fore stay. After you have muscled that, then you crank on the 4:1 system that is on the end of a LOT of leverage. This is a LOT more than direct purchase on the fore stay. If you doubt me, set up this simple system and give it a go.




Quote

Okay, I will now compare the 49-er and the Taipan F16 both of which I sailed and rigged often. Both boats are very comparable in their dimensions.

The F16 has higher rig loads during sailing then the 49-er. In the way of leech and luff tensions on the sail it is not even a comparison. The F16 (luff and leech) loads are many times higher. Especially with the large squaretops.


I have raced both Taipans and F16 sloops and sorry mate, the rig tension even under sail is a LOT more on a smaller 12 foot skiff.

Whilst the Taipan may have fair purchase on the main (7:1 on the ones I sailed), you did not use it all. Over sheeting was far to easy on these tiny cats and would very quickly desort the rig and sail. If I pulled on the main anywhere near what we did with the boat breakers, you would not have a rig left in the T4.9


Quote

It is my experience that skiff spinnaker are flown alot more dead downwind then cat spinnakers, their luffs being alot more loose. So I'm not too sure whether a 3 times greater skiff spi actually loads the mast up more then the lot smaller but tighter luffed + more reaching oriented catamaran spinnakers.


We have sailed many times head to head with these monos and the angles are actually very simular. A cat is all about using low drag and efficency for speed. Skiffs are brute force. There is nothing suptle about it. Grab hold of an 18 kite and it feels like you are about to be pulled threw the blocks. My last ride upfront was on a I14 and whislt the kites are not as big as skiffs, the load was a lot greater than the Tornado. Monos don’t accelerate like a cat when graced by a gust and the loads are really taken up by the rig and the poor sucker holding the sheet. I recently jumped from Cherub to F16 to 12 skiff to Tornado to I14 to F18 and even the smallest mono (AUS Cherub) had larger kite loads than the Tornado.



Quote
I sailed my share of skiffs and all were notoriously difficult to handle on any high broad reaching or reaching. So we mostly did upwind and very deep downwind.
Wouter


You have not sailed a skiff until you have sailed a 12, 16 or 18 footer…… Until then, you can not fully appreciate a true skiff. It is like sailing an F16 and saying that you have experience what a Tornado has to offer………. Different league mate, different league.


Re: wing mast -v- Bethwaite "wing mast" [Re: Tornado_ALIVE] #79335
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Exactly. The skiff, as it is currently designed, has higher "static" rig tension compared to a cat. There is virtually zero mainsheet tensioning used to tension the leech of the main or to tension the headstay on a skiff. Therefore, almost all of the headstay tension on a skiff comes from the side stays.

In an 18ft skiff, I don't see how the tension in the shrouds could possibly be lower than a comparable size cat. The skiff shrouds anchor further inboard yet the rig generates more power due to higher righting moment.

14s and 49ers are smaller boats with smaller (upwind) rigs than most cats so their rig tensions may be lower.

flame on...

Re: wing mast -v- Bethwaite "wing mast" [Re: Jake] #79336
07/07/06 07:11 AM
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Quote

Now I'm really lost however, 29'er not a skiff? Sailing Anarchy as a factual resource? seriously? The thing is a pie tin just like the others...so the rig is a little smaller but does that mean that a Hobie Wave is not a catamaran? - the 9'ers are still the same configuration, bow sprit, main, jib, spinnaker, centerboard, and so unstable in the water that it won't stay upright even without any sails hoisted...how is it not a skiff? Wikipedia even lists the 29'er as an example, among others, of a sailing skiff.



It's probably an australian thing. Unless you can trace a direct lineage down from the early harbour freighties and need to be manned by real, hard, tough men, with scars, it is not a skiff <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Re: wing mast -v- Bethwaite "wing mast" [Re: Jake] #79337
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Now I'm really lost however, 29'er not a skiff? Sailing Anarchy as a factual resource? seriously? The thing is a pie tin just like the others


SA is frequented by many true Skiffies and they are quick to jump on anybody that wants to use the term skiff as marketing BS.

Skiff is a class with its bloodlines tied back directly to the old traditional Waterman's boats of the 1800s and earlier. It is not about performance, even though they are at the pinical. It is about history.

If the skiff was not the pinical of monos, than new (not so)High Performance boats would be calling themself something else.

Imagine if in 50 years from now, every boat, any size and spec that adopted hydrofoils, started calling themself 'Moths'. Do you think the Moth class would be offended. Hell yes.

Anyway, this is not a thread for the 'What is a Skiff' debate, so we'll move on.


Re: wing mast -v- Bethwaite "wing mast" [Re: Tornado_ALIVE] #79338
07/07/06 07:55 AM
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Re: wing mast -v- Bethwaite "wing mast" [Re: Tornado_ALIVE] #79339
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Skiffies have a style you just can't buy <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

[Linked Image]


Re: wing mast -v- Bethwaite "wing mast" [Re: Tornado_ALIVE] #79340
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No no Steve, I am sure I have seen that "move" many times on the regatta course <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Okay, there we have found the core of the ... [Re: Tornado_ALIVE] #79341
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Okay, there we have found the core of the disagreement.

I'm indeed only really familiar with the 29-er, 49-er, laser 3000, laser 4000, laser 5000 and RS800 design. To me these were skiffs. I have only seen (and touched) a 18 footer twice in my life and none of the others. I did not test the rig tension at those times

Apparently these boats are alot different then the real skiffs as that boat breaker you show in the pic it a true monster !

That baby will easily pull effectively 16:1 or close to a 1000 kg.

The pic didn't load the first time I read your post, my internet exploder, ... well ... had some issues. I understand now.

With respect to the sheet loads I guess once again the difference is between the semi skiffs like 49-er and the true skiffs.

I remember we had only one ratchet block on the 49-er with only a 70-90 degree wrap around the sheeve. Remarkably that felt alright with me. Also these spis would collaps as soon as you tried to head up to a high broad reach.

He Stephen the way you make it sound it appears that the skiffs are not sailboats at all, but rather body building apparatus ! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> (joke)


Quote

It is like sailing an F16 and saying that you have experience what a Tornado has to offer………. Different league mate, different league.



I must really get a ride on a tornado sometime, apparently that is something else. I already feel that going from a Taipan 4.9 + spi to a modern F16 like the Blade is a big step up but it appears it gets better still. I never really believed that but maybe I need to do some fact checking in this case.

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: wing mast -v- Bethwaite "wing mast" [Re: Tornado_ALIVE] #79342
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Quote
Quote
Now I'm really lost however, 29'er not a skiff? Sailing Anarchy as a factual resource? seriously? The thing is a pie tin just like the others


SA is frequented by many true Skiffies and they are quick to jump on anybody that wants to use the term skiff as marketing BS.

Skiff is a class with its bloodlines tied back directly to the old traditional Waterman's boats of the 1800s and earlier. It is not about performance, even though they are at the pinical. It is about history.

If the skiff was not the pinical of monos, than new (not so)High Performance boats would be calling themself something else.

Imagine if in 50 years from now, every boat, any size and spec that adopted hydrofoils, started calling themself 'Moths'. Do you think the Moth class would be offended. Hell yes.

Anyway, this is not a thread for the 'What is a Skiff' debate, so we'll move on.


So a "skiff" is not a boat configuration - it's a measure of the testosterone onboard?

They way the terminology is used over here is certainly different. If a boat measured in to the moth class rule, then yeah, it's a moth. The moth is a boat defined by class rules the same way an F18 is. Moth is a "dingy" (I guess?) and an F18 is a "catamaran" as is an I14 a "skiff", etc.

I guess the problem is that folks in Aussy land consider the term "skiff" to not be a reference to the confiuration of the boat as we do in the US and in Wouter-land.


Jake Kohl
Re: Okay, there we have found the core of the ... [Re: Wouter] #79343
07/07/06 08:49 AM
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Quote

I must really get a ride on a tornado sometime, apparently that is something else. I already feel that going from a Taipan 4.9 + spi to a modern F16 like the Blade is a big step up but it appears it gets better still. I never really believed that but maybe I need to do some fact checking in this case.

Wouter


Get a ride on one could be a very expensive mistake <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Chris249 who use to frequent here was a die hard T4.9 sailor and had raced with spinnakers. I lined him up a ride on an old clapped out Reg White with spinnaker at the Sydney International Regatta SIRs...... And well, he was smiling from ear to ear when he hit the shore and could not stop talking about it. He could not believe the power of the big Ts.

I do miss my T <img src="http://www.catsailor.com/forums/images/graemlins/confused.gif" alt="" />....... But feel I have made the right choice with the F18 Worlds in AUS. Will have to return to Ts after though.


Re: Okay, there we have found the core of the ... [Re: Tornado_ALIVE] #79344
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Hello gents,

Wouter, on an 18 we don't have 20mins to haul the spinnaker up and play with moving shroud bases. Like TA said, the boat relies on pure grunt; the wing mast could be beneficial if you could figure out a system that worked efficiently. One day someone will, right now there isn’t the need for one.

As the poor bowman (yeah right I love it!!!) on one of these craft I can tell you that the spinnaker loads are out of this world. I have sailed on a F18 with TA in 30+ knots and there was no comparison between the sheeting loads.

The wing mast has been experimented with a long time ago but then was shelved after a fair few of them blew up downwind under spinnaker in 25 knots.

For reference the number 1 spinnaker on an 18ft skiff is approximately 750ft^2. That will vary from boat to boat as the sail sizes are unrestricted.

I have blown up a rig breaker before trying to get the rig tension on and whilst wave jumping in 20 knots on Sydney Harbour snapped 6 of the 9 or so strands which comprise 4mm wire. I think you could say the 18 rig has a fair bit on. Must be off now chaps, lovely chatting to you.

Cheerio
T_E

Re: wing mast -v- Bethwaite "wing mast" [Re: Tornado_ALIVE] #79345
07/07/06 09:52 AM
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There is one thing I still don't understand though.

For all their grunt and huge sailareas, the VYC handicap ratings (statistics based) are still slower then a Hobie 16's.

Even the now real skiff 49-er is rated faster then the 12, 14 and 16 foot skiffs as well B14, cherub. As a matter of fact it is the second fastest rated MONOHULL boat after the 18 foot skiff. Pretty much 85 % of the cats is rated faster.

How is that explained. Is the rating system wrong ?

http://www.nsw.yachting.org.au/site/yachting/nsw/downloads/Yardsticks04_05.pdf

Wouter

Last edited by Wouter; 07/07/06 09:53 AM.

Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: Okay, there we have found the core of the ... [Re: Team_EvoLv] #79346
07/07/06 09:59 AM
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Wow, 750ft^2 Spin on an 18' skiff (or whatever you want to call it) I've got a spin of that size on my 27' Stiletto. 36' Masthead rig and its huge... I've run a 400ft^2 on a 20' boat and sheeted it back to the rear beam. Where do you put the other 350ft^2?

Just curious as I know nothing about Skiffs. <img src="http://www.catsailor.com/forums/images/graemlins/confused.gif" alt="" />

Clayton
S27, H16

Re: wing mast -v- Bethwaite "wing mast" [Re: Wouter] #79347
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Most of the skiffs listed never race in mixed fleets so data is not sent in (some numbers may be inaccurate, most are pretty good). The 18ft skiff is only slower by 2.5 points or so to the Tornado from that data (from memory) which would be an accurate reflection between the boats.

Pretty sure the foiling Moths are faster than a 49er too, will find out soon enough.

T_E

Re: Okay, there we have found the core of the ... [Re: Clayton] #79348
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Hi Clayton,
The 18ft skiff rig is around 34' from memory and the bow sprit is around 12ft long. To be fair it is scary how much there is pulling you along. If you do a google image search you will be blown away at the sheer size of the sail area.
T_E

Re: Okay, there we have found the core of the ... [Re: Team_EvoLv] #79349
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Wouter, I have sailed with 49ers and in NO WAY a Hobie 16 can be as fast as a 49er, something must be quite wrong with this yardstick.

Re: Okay, there we have found the core of the ... [Re: claus] #79350
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For that matter, a 29'er is only rates slightly faster than a laser (mainsail only!)...I think it's mostly because a lot of the data reflects sailors who's skill level may not be sufficient to keep them upright around the course because a 29'er is most certainly faster.


Jake Kohl
Re: Okay, there we have found the core of the ... [Re: Jake] #79351
07/07/06 01:03 PM
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I'll be sailing in a mixed fleet with I14s, 29ers, and possibly 49ers tomorrow--we'll see how it shakes out on the water.


Eric Poulsen
A-class USA 203
Ultimate 20
Central California
Re: Okay, there we have found the core of the ... [Re: ejpoulsen] #79352
07/07/06 08:21 PM
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At the end of July we will be racing a harbour marathon, followed by a regatta 2 weeks later on Sydney Harbour. Monos will include 29ers, 49ers, B14s, Cherubs, Moths, Foiling Moths, 12s, 14s, 16s, 18s.

Cats should include A Class, F16s, F18s, Tornadoes, Maccas Super Taipan...... So expect an ambush from the cats <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Brass Monkey Regatta 2005

[Linked Image]

18 Footer

[Linked Image]


Re: Okay, there we have found the core of the ... [Re: Tornado_ALIVE] #79353
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The yardsticks for nearly all of the skiffs are slightly inaccurate there. The 29er is about the same speed as the 505 and Flying Dutchman (keep in mind Australia has the top 29er fleet globally),yardstick 95.

The Laser has a yardstick of 112, this is so low because it is sailed by such talented sailors who are extremely good at sailing the Laser. The average club sailor will not be able to race to this number on most occasions.

The 29er is a non professional class. In saying that when my friends went to San Fran for the 05 worlds they were training 6 days a week before hand (that is a hell of a lot of time on a boat). However, I beleive the tactical prowess would not be the same as older more experienced sailors who tend to not sail in the class very much. This means it could be possible for the rating to be even lower.

Oh the 12ft skiff rating is a load of bollox! Absolute rubbish I'm affraid. That boat can almost pace an 18 downwind! (runs deep because of the huge kite, almost as fast, in some conditions)

T_E

different tack [Re: Team_EvoLv] #79354
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Bethwaite also talks about gust-onslaught response. He talks about wing masts being fastest in wind tunnel tests. The problem he had, was real world experience wasn't matching the theory. They discovered that in gusty conditions other rigs were faster. The wing masts are too rigid to bend automatically in the gusts. They developed rigs that automatically depower momentarily when a gust hits, giving the crew time to react to the gust, resulting in keeping the boat moving fast on its feet rather than heeling.
Seems like the windsurfer rigs are doing this also, but that the sails are cut to to bleed off power when you reach a certain amount of mast bend.

The closest I come to skiff sailing is an occasional sail on an I-14. So I don't have personal experience there, just seemed what appeared to me to be an important point in Bethwaite's book wasn't being brought up.

John
Miracle 20

Re: Okay, there we have found the core of the ... [Re: Team_EvoLv] #79355
07/10/06 07:56 AM
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Quote

That boat can almost pace an 18 downwind!


Yes, but what does it do upwind ? The 18footer has 9 foot wide racks and am I correct that the 12' don't allow racks at all?

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: Okay, there we have found the core of the ... [Re: Wouter] #79356
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Racks are allowed on the stern to help prevent nose diving downwind but they are inline with the max beam of the boat.

Upwind the boat isn't as quick obviously. I think someone said 9knots upwind tacking through 80 degrees, don't quote me on that. The boats have 4 rigs so they can have the appropriate craziness for each wind strength. The number 1 rig is 28ft high.

I think you have missed the whole point of the class though Wouter. You have to have big balls to sail these boats and the only reason they go upwind is so they can go off the planet downwind again.

Do some googling and you might understand where I am coming from. Tell me this, what two man 12ft boat does 24 knots downwind? I have seen the GPS tracks.

Cheers
T_E

Re: Okay, there we have found the core of the ... [Re: Team_EvoLv] #79357
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12ft + a 14ft pole.

Re: Okay, there we have found the core of the ... [Re: Team_EvoLv] #79358
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I don't think I lost the point at all.

A sailboat race is a race around a COURSE. As most will remember I go go against A-cat sailors who claim to be first at the A-mark only to be cheaten out of a victory by OVERALL faster spinnaker boats. In the same line of thought I go against skiffs that do 24 knots downwind only to crawl back up. Seems to me that those VYC ratings can be correct afterall. And that was of course the orginal point as I asked how it could be that those "around a course" handicaps were so slow for the skiffs.

I don't have an axe to grind here I'm still trying to learn why the skiffs are not using the Bethwaite square back rotating masts. The end criterium should be "around the course" performance. And as such the balancing of downwind and upwind performance is important. One poster mentioned that the rotating mast wouldn't carry the mast head spinnaker needed for the downwinds. But what if the true gains are to made upwind ? Would better upwind speed not be worth a smaller spi that the rotating mast can handle.

Looking at the speed difference of (roughly) 9 knots upwind (6.5 knot vmg) and 24 knots downwind (vmg 20 knots) it looks to me, as an engineer, that the upwind is by far the most important leg on these boats and that 5 % additional performance on this leg is worth any "over 15 % performance hit" on the downwind legs. ESPECIALLY when these boats are width limited. The latter point would also favour more efficient rigs and masts (bethwaite squarebacks) then the grunt rigs (round tubes and less earodynamic efficient) they feature now.

It seems to me that I'm actually full on topic here.

In sailboat racing it is all about making the best average around a course, not about maximizing one particular leg at the expense of everything else.

Afterall I can drop my boat of the nearest high rise building and achieve better speeds if it weren't for the problems getting back up again afterwards. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: Okay, there we have found the core of the ... [Re: MauganN20] #79359
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Do you think these skiff sailors are compensating for something ? <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />


Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: Okay, there we have found the core of the ... [Re: Wouter] #79360
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Quote
Do you think these skiff sailors are compensating for something ?


Yeah, their UPwind "performance" :P

Re: Okay, there we have found the core of the ... [Re: Wouter] #79361
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Wouter, 12ft skiffs are a culture, it's obvious you will NEVER understand that. The 12ft skiff is not a professional class and to go out and blow however much money on a wing mast that could snap so easily is a bit much. The whole point of a 12 is the downwind ride. Get it in your head.

This season one of my mates built a skinny 12 and is in the process of trying to make a boat that is more efficient upwind to make the gains on the fleet here and try to hold them off down. It does not work yet because it is too unstable. I think you will find the guys here are a few steps ahead in finding out what works and what does not.

You’re a pretty obnoxious bugger and I think you should stop trying to analyse things you know pretty much nothing about and go back to wouterland.

When you drop your boat off the edge of that high rise building think about going along for the ride. You will then understand what a 12ft skiff ride is like.

Yeah Wouter, great call there champ. You’re a dead set idiot. Go play with yourself because no one else will.

T_E

Re: Okay, there we have found the core of the ... [Re: Team_EvoLv] #79362
07/10/06 09:43 AM
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oh no

you do realize that THE wouter isn't going to like that right?

You'll unleash a fury that will crash browsers.

Re: Okay, there we have found the core of the ... [Re: MauganN20] #79363
07/10/06 10:12 AM
07/10/06 10:12 AM
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Essex, UK
Jalani Offline
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Jalani  Offline
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Time for popcorn I think.........

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John Alani
___________
Stealth F16s GBR527 and GBR538
Re: Okay, there we have found the core of the ... [Re: Jalani] #79364
07/10/06 01:39 PM
07/10/06 01:39 PM
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scooby_simon  Offline
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Quote
Looking at the speed difference of (roughly) 9 knots upwind (6.5 knot vmg) and 24 knots downwind (vmg 20 knots) it looks to me, as an engineer, that the upwind is by far the most important leg on these boats and that 5 % additional performance on this leg is worth any "over 15 % performance hit" on the downwind legs. ESPECIALLY when these boats are width limited. The latter point would also favour more efficient rigs and masts (bethwaite squarebacks) then the grunt rigs (round tubes and less earodynamic efficient) they feature now.


How can this be a good idea?

5% gain on 9 kts upwind gives a speed of 9.45kts (so a .45 kts gain). Not much

15% loss on 24kts downwind gives 20.4 kts (so a 3.6kts loss).

Now unless the boat is having to sail a LOT higher to get this speed(which is not mentioned above), I'd suggest the "slower" upwind boat will still win around the course.

The numbers just don't make sense here.


F16 - GBR 553 - SOLD

I also talk sport here
Re: Okay, there we have found the core of the ... [Re: scooby_simon] #79365
07/10/06 02:18 PM
07/10/06 02:18 PM
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North-West Europe
Wouter Offline
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Okay,

This is simple mechanics math guys.

If a boat is doing say 6.3 knots vmg upwind and 20 knots vmg downwind. how long will it spend racing on the upwind legs, and how long will it spend on the downwind legs of the SAME course ?

Indeed, it will spend 3 times as much time sailing upwind as downwind.

Say he is doing a race of 40 minutes; he is then spending 10 minutes sailing downwind and 30 minutes sailing upwind.

5 % gain on 30 minutes = 90 seconds
15 % loss on the 10 minutes = 90 seconds

So here a 5 % upwind gain cancels out a 15 % downwind loss. We all know that small reaches are included in sailing courses (impacting more on the downwind advantage then on the upwind one, again because of difference in spend time on each leg) and also upwind advantages are very important at the start and right after the start. So in this case I would favour the upwind advantages.

This is what I actually found while sailing the 49-er (and other likewise boats like RS800), which I'm told is not a real skiff. No matter how great the downwind legs it could and would get bagged by Hobie 16's (and other cats) by seriously lacking upwind speed. But then again I'm just an obnoxious nobody who knows diddly squad about sailing. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> So maybe I could not sail that 49-er well if my life dependent on it. I am beating those H16's on my F16 though which has less sailarea and the same weight as 49-er; so I'm not a complete dud.

Wouter

Last edited by Wouter; 07/10/06 02:20 PM.

Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: Okay, there we have found the core of the ... [Re: Wouter] #79366
07/10/06 02:43 PM
07/10/06 02:43 PM
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Good point about spending longer on the upwind work.


F16 - GBR 553 - SOLD

I also talk sport here
Re: Okay, there we have found the core of the ... [Re: scooby_simon] #79367
07/10/06 09:52 PM
07/10/06 09:52 PM
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T
Team_EvoLv Offline
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Team_EvoLv  Offline
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T

Joined: Jul 2006
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Hi Wouter,

Theoretically you have brought up some good points. The only problem with the theoretical values of a 12ft skiff is they often are impractical for the class. The 12ft skiff is so small and susceptible to the environment around it that some ideas will actually mean that the boat is almost impossible to sail in normal conditions.

The 12ft skiff is prone to nose diving and needs the volume in the bow to help ride over the waves downwind. The volume of the hull also helps in this respect and provides a large planning base for the boat to sail on. One of the issues with trying to make a more efficient 12ft skiff is the boat is so small that some compromises must be made to make the boat sailable.

The new skinny 12ft skiff which looks somewhat like a skinny moth with a twin trapeze rig and huge asymmetric spinnaker attached. Theoretically the craft is much faster than the other 12ft skiffs upwind but on the water the boat still needs refinement. The narrow waterline has made it much harder to balance and any gains that have been made due to the changes have been cancelled out by capsizes or tea bagging (dropping the crew in to windward without capsizing). The boat will be sailing this season properly and we will have the chance to see how it goes.

The wing mast is on the agenda for many people down here but proves a challenge to the designers and sailors. The boats carry so much sail area to overcome hull drag and carry the desired crew weight they need the flexible upper mast tip to bleed open during the gust so that they can hold the power. So far the problem has been producing a wing rotating mast that would be able to let the rig de-power upwind but not be completely snapped off by the huge loads exerted by the spinnaker which is in the realms of 50m^2.

Mast compression is a concern in skiff masts and developing a rig which can cope with the loads induced is difficult. For all its short comings the round section does a sterling job and until a reliable wing mast can be produced will take precedence. I am sure you can appreciate the loads from the pictures that have been provided.

It is true that big gains could be made upwind in this regard and many of the skiffs are trying to make improvements in this area of their sailing. From what I have read you’re obviously a very intelligent person. In future I would ask that you show perhaps a little more respect for other classes. Nothing wrong with having an intellectual discussion but it would be appreciated if you dropped the attitude.

Sorry for the huge reply, so much to say.

T_E

Re: Okay, there we have found the core of the ... [Re: ejpoulsen] #79368
07/10/06 10:32 PM
07/10/06 10:32 PM
Joined: May 2002
Posts: 1,037
Central California
ejpoulsen Offline
old hand
ejpoulsen  Offline
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Quote
I'll be sailing in a mixed fleet with I14s, 29ers, and possibly 49ers tomorrow--we'll see how it shakes out on the water.


About 12 I14s present and 8 29ers, most from the SF Bay Area. It was a real treat to see the I14 skiffs--wow, they are getting narrower every year. Very interesting rigs--fun to see how refined every detail was on some boats. I can only imagine how challenging the 12s are to sail. Hats off to the skiffees.

As far as speed around the course goes, really not much to say here as we didn't see them much after the first leg. I believe their "top end" speeds downwind would be insanely fast in breezier conditions than we had, though.

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Eric Poulsen
A-class USA 203
Ultimate 20
Central California
Re: Okay, there we have found the core of the ... [Re: Team_EvoLv] #79369
07/11/06 12:01 AM
07/11/06 12:01 AM
Joined: Nov 2005
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Victoria, Australia
C2 Mike Offline
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C2 Mike  Offline
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Quote
Racks are allowed on the stern to help prevent nose diving downwind but they are inline with the max beam of the boat.

Upwind the boat isn't as quick obviously. I think someone said 9knots upwind tacking through 80 degrees, don't quote me on that. The boats have 4 rigs so they can have the appropriate craziness for each wind strength. The number 1 rig is 28ft high.

Cheers
T_E


Mad. Are you sure the challenge isn't to pack as much $$$ per foot of boat? They would nearly be worse than the i14s to buy!

Tiger Mike

Re: Okay, there we have found the core of the ... [Re: C2 Mike] #79370
07/11/06 12:40 AM
07/11/06 12:40 AM
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T
Team_EvoLv Offline
stranger
Team_EvoLv  Offline
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T

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Well they are money machines in a sense. A new one all kitted up is $50K but the thing is they last for ever. Sponsers and race money help here though. I think 5ohs and i14s are crazy with the money side. Mind you that isn't going to stop me having a go!

T_E

Re: Okay, there we have found the core of the ... [Re: Team_EvoLv] #79371
07/11/06 03:18 AM
07/11/06 03:18 AM
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North-West Europe
Wouter Offline
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Wouter  Offline
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I say thank you for the long reply, I find it interesting to hear this stuff about the skiffs. i've been well aware of them for a long time. I just didn't know that boats like the 49-er were not considered real skiffs. Additionally I find you commentary alot more interesting then the skiff class webpages. You are providing alot more detailed info and info that allows me (at least) to get a better feel for the balancing that is included in designing a better skiff. Afterall, this is part of any boat design.

I can understand the absolute need for the design to help in the area of control. As said, when I sailed the 49-er I noticed that any help here is a major point. It allows you to drive it much higher by not having to keep a significant safe margin. Again this is the interesting balancing act and the skiffs are on a totally different path in the way of rig development.

Clearly the skiff rig tension is heaps more then what I personally found on, again, boats like 49-er. So I think I admitted to that earlier in this thread. And yes this does provide an engineering challenge. Although I do still wonder why exactly this high tig tension is needed. What is its beneficial effect or what is causing this to be necessary ? Do you know ? On the 49-er it appeared that that the designs tried to bend the flexible mast into a stiff lower section by the yielding method of buckling. This does require alot more tension then bending a mast by "cantilevering" it. I feel cats are mostly using the last method and that the stiff for aft plane doesn't require rig tension to sufficiently fix the bottom part of the mast to a given curve. That and the fact that a skiff rig can never accept loose shrouds as that would negative impact on control by having a mast that can independently move relative to the platform. I'm very interested in your ideas here.


Quote

In future I would ask that you show perhaps a little more respect for other classes.



Ohhh, I do very much respect these classes and all as a matter of fact. I'm just also a digger and question everything. I want to know how it really is and you don't get there by asking softball questions. I also fear that at alot of times my way of writing can be intepreted as being respectless, but in basis it truly isn't. Although I do have a streak of using biting sarcasm in my writings alot. That comes from my upbringing, was considered a sport in the (very much loving) family I grew up in. And sadly this was also the case among students and friends at the University I went to after leaving the family. Even in the Netherlands themselfs these have a reputation for being like this.


Quote

Nothing wrong with having an intellectual discussion but it would be appreciated if you dropped the attitude.



I'll try ! But also know that I never mean that much by it, certainly not disrespect. Disagreement with the points stated yes that it signales but not hate or disrespect.

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: Okay, there we have found the core of the ... [Re: Wouter] #79372
07/11/06 07:04 AM
07/11/06 07:04 AM
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scooby_simon Offline
Hull Flying, Snow Sliding....
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Quote
The wing mast is on the agenda for many people down here but proves a challenge to the designers and sailors. The boats carry so much sail area to overcome hull drag and carry the desired crew weight they need the flexible upper mast tip to bleed open during the gust so that they can hold the power.


So why not taper the wind mast ?

John P does it on his F16's and some of the old T's had tapered Alu masts.


F16 - GBR 553 - SOLD

I also talk sport here
Re: Okay, there we have found the core of the ... [Re: Wouter] #79373
07/11/06 07:31 AM
07/11/06 07:31 AM
Joined: Apr 2003
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Melbourne, Australia
Tornado_ALIVE Offline
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Hi Wouter,

I don't think that the rig is the major contributing factor to a monos upwind performace, or lack of..... Just don't think they are as efficient as a cat in using the boat's weight as righting momentum. The only way I see they can minimise the disadvantage is by using wings (skiffs) or canting keel (yachts). Please read what I wrote previously and add your thoughts.

Quote
Dont forget that a monos weight without crew is balanced over the keel line and with crew, its righting momentom is the weight of only its crew. In an 18s case, it is 3 crew 7.5 feet from the center line. 15 foot wing span I believe now.

A cats righing momentum is the weight of the platform and its rig from the windward side of the leeward board...... plus the crews weight, 8 foot (or just under 10 foot for a T) out from the pivot point.

Looking at this, the cat has a lot more righing momentum and uses the weight of the boat far more efficiently.


As for skiff rig tension, I believe that the reason for the high rig tension is to give the rig enough prebend to support a mast head kite without inverting the rig, whilst using a lighter / smaller mast section.

It also allows a bit more gust response than a stiffer wing mast. A mono does not harness and transfer the energy from a gust as well as a cat, but tends to transfer it more to heel, thus the need for better gust response.

Sorry T_E, but if monos were to maximise their efficiecy, they will have to strap on another hull or 2......... or hydrofoils <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/tongue.gif" alt="" />


Re: Okay, there we have found the core of the ... [Re: scooby_simon] #79374
07/11/06 07:36 AM
07/11/06 07:36 AM
Joined: Apr 2003
Posts: 1,669
Melbourne, Australia
Tornado_ALIVE Offline
Pooh-Bah
Tornado_ALIVE  Offline
Pooh-Bah

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Melbourne, Australia
Quote
So why not taper the wind mast ?

John P does it on his F16's and some of the old T's had tapered Alu masts.


They will still need to overcome upper mast stability. I believe it would be achievable by tapering the mast and using 3 to 4 overlaping sets of diamonds to achieve a prebend with enough support up top.

Development cost time and money....... Somebody will do it eventualy. May be some cat guys need to jump ship and show them <img src="http://www.catsailor.com/forums/images/graemlins/shocked.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />


Re: Okay, there we have found the core of the ... [Re: Tornado_ALIVE] #79375
07/11/06 07:49 AM
07/11/06 07:49 AM
Joined: Jun 2001
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North-West Europe
Wouter Offline
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Wouter  Offline
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Quote

Please read what I wrote previously and add your thoughts.



Yes I understand your earlier comments.

My line of reasoning (and it is just that) is that when a craft is limited by righting moment (as surely the mono's are) then a more aerodynamic efficient rig will allow them to create more drive for the given righting moment AS LONG AS it doesn't also include making the mast (leverage) significantly greater.

Pretty much efficiency can be deduced down to a ratio of devellopped drive against devellopped sideways force that causes heel.

I also seem to recall from the Miss Nylex design article that 40 % of the total drag of this C-class cat was the direct result of aerodynamic drag of the sails. It was the single biggest drag factor. I'm not sure how this translates into planing skiff designs. Maybe here the hull drag is significantly higher percentage wise. T_E comments seem to point in that direction.

T_E comments about the (control) compromises is really the only factor then can foil up the above reasoning.

Stephen, you comment :

Quote

As for skiff rig tension, I believe that the reason for the high rig tension is to give the rig enough prebend to support a mast head kite without inverting the rig, whilst using a lighter / smaller mast section.


Combined with my 5%-15 % example seem to suggest that it may pay off to drop the mast head spi for one that comes lower on the mast (as with cats) if that allows a sufficiently better upwind rig.

I wonder whether losing 1 mtr on the luff or so will loose 15 % downwind performance. Also going down on spi hoist height really quickle stiffs up the mast top. There is a very powerful 3rd order (power) relationship there. Going to the mast top is not a straight forward must-have.

This could be a case analogue to "slow down to win" , the well know manouvre when rounding the bottom mark with alot of other boats.

All interesting stuff

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: Okay, there we have found the core of the ... [Re: Wouter] #79376
07/11/06 08:12 AM
07/11/06 08:12 AM
Joined: Apr 2003
Posts: 1,669
Melbourne, Australia
Tornado_ALIVE Offline
Pooh-Bah
Tornado_ALIVE  Offline
Pooh-Bah

Joined: Apr 2003
Posts: 1,669
Melbourne, Australia
Quote

Combined with my 5%-15 % example seem to suggest that it may pay off to drop the mast head spi for one that comes lower on the mast (as with cats) if that allows a sufficiently better upwind rig.

I wonder whether losing 1 mtr on the luff or so will loose 15 % downwind performance. Also going down on spi hoist height really quickle stiffs up the mast top. There is a very powerful 3rd order (power) relationship there. Going to the mast top is not a straight forward must-have.

This could be a case analogue to "slow down to win" , the well know manouvre when rounding the bottom mark with alot of other boats.

All interesting stuff

Wouter


Such as the 12 footer with the A Class rig I posted above...... Don't worry Wouter, they'll catch up one day <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />


Re: Okay, there we have found the core of the ... [Re: Tornado_ALIVE] #79377
07/13/06 12:46 PM
07/13/06 12:46 PM
Joined: Oct 2002
Posts: 307
maui
jollyrodgers Offline
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jollyrodgers  Offline
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maui
i can name a sail boat under twelve feet that goes overt 25 knots, and it doesn't suffer to windward although it has no daggerboard.
windsurfers and kiteboards both have that capability and they don't cost $50,000.
You just can't apply common sense to a topic like this.

Re: Okay, there we have found the core of the ... [Re: Tornado_ALIVE] #79378
07/13/06 04:45 PM
07/13/06 04:45 PM
Joined: Feb 2004
Posts: 461
Sydney Australia
Berny Offline
addict
Berny  Offline
addict

Joined: Feb 2004
Posts: 461
Sydney Australia
[/quote]Such as the 12 footer with the A Class rig I posted above...... Don't worry Wouter, they'll catch up one day <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> [/quote]

I'd think that nosediving would be made worse by the 'A' rig, yes?.

Re: Okay, there we have found the core of the ... [Re: jollyrodgers] #79379
07/14/06 12:07 AM
07/14/06 12:07 AM
Joined: Jul 2006
Posts: 10
T
Team_EvoLv Offline
stranger
Team_EvoLv  Offline
stranger
T

Joined: Jul 2006
Posts: 10
Hey Jollyrodgers,
I said TWO man craft. Read it again champ.
T_E

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