wing mast -v- Bethwaite "wing mast"

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.

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

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.

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.

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.

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

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.

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.

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

Skiffs like I14s have non-rotating masts with high tension upper AND lower stays.

Skiffs like 49ers/29ers have non-rotating masts but achieve good airflow by sleeving the sail around the mast.

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.

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.

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

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

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

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

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

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.

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.

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.

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.

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.

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

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.

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.

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

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.

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.

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.

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

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.

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.

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...

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=

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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.

low budget hobie bob http://www.catsailor.com/bb_files/80123-picture027.jpg

Skiffies have a style you just can't buy <img src=

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