Mast Compression with Aussie Jib Halyard

So after all this - does the aussie rig offer any advantages over the standard rig?

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1979 Hobie (sold)
1983 Hobie 16 Hawiian Sunset (sold)
1981 Hobie 16 Tequilla Sunrise - still own
2008 Hobie 16 (currently sailing the crap out of this boat)
1977 Super Sunfish
Founding member of the "San Dimas Yacht Club"
John

yup
Adv: Easier to hoist. Easier to make fine adjustments.
Disadv: lotsa excess halyard to stow after jib is raised. Costs more.

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Alan
'86 H16, Sail #89057

yup
Improved and more consistent mast rotation and mast bend due to reduced jib halyard load running down the mast, especially on systems where the cheek block is on the side of the mast. i.e., the mast is less inclined to counter-rotate - Primary advantage.


subjective. The load on the halyard while hoisting is 1/3 that of the stock system, but you have to pull 3 times as much. It's actually a little bit more of a pain, but since hoisting the jib is pretty much a no-brainer with both systems, I'd call it a wash.


nope
Since both systems have a final purchase of 3:1, both systems require the same amount of effort to make adjustments.

sm

Subjective, depends on where and how you typically grab the halyard and what you personally feel is easier. Personally, I like not having the lower downhaul block in my way.

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Alan
'86 H16, Sail #89057

There was a lot of discussion in this thread about the Aussie jib haylard, only about half of which I really understood. Here's my experience:

Went for my first sail since upgrading to an Aussie jib haylard today. Wind in the 7 to 20 mph range, lots of gusts, lots of shifts.

Hoisting -- Half a dozen of one, six of the other. Adjusting mast rake required less muscle, but it seem to take forever to finally get the jib up. That line seemed to go on and on. It did get twisted but that didn't seem to effect anything.

Mast rotation -- A big improvement. With the original system, after a tack the mast would hang, and wait for a good gust to rotate into the proper position. Now it rotates through the tack and is in the proper position as soon as the tack is complete. This reduces the sudden position change that was annoying me. It depends upon whether this is a worthwhile improvement depending on how you sail. Racing, definitely you want the power coming from a tack. But cruising it's going to depend upon your tacking frequency. I sail on a smaller lake, and do something like 20+ tacks heading upwind. Tacks are short and there's not much of a run on each tack. So for me, definitely improving this was worth the money. If I tacked a lot less, and made longer runs on each tack, probably not.

Tacking -- I can't really say whether the tacking was better or not. I had too many tacks during wind shifts and they were just bad. I had one tack that ended up 180 degrees because of a wind shift. No way is that going to be a good tack in a catamaran no matter what you do.

In irons -- Several tacks resulted in me being trapped in irons as I tried to figure out where the wind had shifted to. A lot more vibration in the mast during these periods, which was a bit scarey at first, but nothing broke, so I can live with it.

Overall, for me it was worth the money. It smoothed out the period of powering up from a tack and got rid of the sudden mast shift. Since I tack a lot, it's something I'd been noticing.

Best of luck,

Jim Clark-Dawe

The whole mast compression thing is a red herring.

If the Aussie Halyard reduces stretch in the system, it should be faster.

The Jib Luff wire acts as a spring. It stretches x% for every y% of load. A wire of length d might stretch s inches under load t. A wire 2d long will stretch 2s inches at the same load.

This means when a gust hits the jib the luff sag is about double with a wire halyard running down the mast.

Put the 3:1 at the head of the sail and as long as the halyard going down the mast stretches less than 300% of the wire you have a net reduction in luff sag in gusts. The Jib luff stretching also increases rake in gusts, if the main sheet is to-blocked the jib luff stretch should reduce main leech tension and depower the sail.

The other issue is halyard tension causing mast bend. I suspect this is why better tacking is reported. The mast is not popping due to jib halyard induced bend.

I know I'm new here, but I have years of experience as a rigger. Reducing halyard compression loads in masts is sort of a holy grail.

Compression loads in the mast and vertical loads on the mast step are two completely different issues. They are related, but not the same. This is where this tread jumped the shark.

Cheers,

Randy

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Sail More. Tinker Less. Enjoy a Hobie Day.
-2013 H16 #1`13780
-2014 Getaway w/wings,spinnaker,& trapeze

Stretch is a different subject. Pick different halyard. You could go with steel and eliminate stretch, but that's not the point. The whole point of the Aussie system is where the 3:1 happens, and since you go on to defend the idea of lowering the mast compression, I'm not sure why you say that's red herring. Can you clarify what you mean?

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'00 H16 #104691
'78 H16 #32692 ex-rental [gone]
Old Holsclaw trailer
My Hobie 16 pages

I know nothing about mast compression or the rest of it...

But I LOVE the aussie halyard for the fine tuning it allows you to do on the water ... The other setup just never seems to be as smooth nor look as tidy... I guess you could rig it up to be a bit better... but why?


With an extra turning block and a cam cleat on the side of the mast the aussie system is magical..

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www.thehobiewayoflife.com

I have to disagree. SS wire rope stretches. Within elastic limits steel is wonderful stuff for things like rigging and springs. It deforms under load quite predictably and repeatably. If the wire luff and wire halyard to the mast base are 40 ft total an the load is enough to stretch the wire 2 inches fixing the luff at 20 ft reduces the luff stretch by 50% or 1 inch. If the 3:1 at the tang results in a rope halyard that stretches less than 1 inch under 33% of the load you have reduced the total stretch of the system. As I said, "if" the total stretch is reduced by replacing the wire halyard with a rope purchase it should be faster.

If on the other hand the total system stretch is the same and the only difference in the systems is the reduction in section load you have to look at the results of that section load.

Because people have reported the mast seems to rotate more freely with the Aussie system and there is no difference in mast step loading between the systems the only thing that remains is sideways mast bend held from one tack by halyard tension. No one has made that argument so far. If the jib halyard tension was high enough to put a static bend in the mast someone would have noticed in the last 40 years.

The comment about reducing halyard compression loads in masts being a holy grail is it allows you to select a lighter section. In the case of the H16 the section is one design and unless the jib halyard tension is high enough and off centre enough to cause sideways mast bend it should have no effect.

It is entirely possible that the real benefit is simply ergonomics of adjusting the tension on the water. Adjustments that are easy to make get made.

_________________
Sail More. Tinker Less. Enjoy a Hobie Day.
-2013 H16 #1`13780
-2014 Getaway w/wings,spinnaker,& trapeze

What does your personal experience tell you? Mine tells me that the old wire halyard doesn't stretch noticeably. I have one lying around here if you want to calculate how much it would stretch before something on the boat broke. The Aussie system is not stiffer, in my personal experience. It also needs to be retensioned after a while, but that's a different kind of stretch anyway.



That was mentioned earlier in the thread, and it seems like a significant factor to me. The masts are pretty flexible when loaded, and reducing the asymmetrical forces can only be a good thing.

_________________
'00 H16 #104691
'78 H16 #32692 ex-rental [gone]
Old Holsclaw trailer
My Hobie 16 pages

The only point I am trying to make is that unless the effect of the jib halyard tension compression on the mast can be measured, reducing that compression cannot have a measurable effect.

The amount the wire stretches is fairly simple to calculate. Most wire rope halyards are 7x19 construction and made of 302 SS or 316 SS. The properties of this wire is known with great accuracy. If you measure the stretch, you can calculate the load if you know the size and alloy of the wire. If you know the load you can calculate the stretch.

You are correct to note the stretch in the Aussie system that requires it to be re-tensioned is not the same stretch that is measured in a wire halyard. All braided line suffers from set and creep.

Your idea about reducing unwanted asymmetric loads is a good idea. However, if there is no measurable effect of the load, spending time and money to reduce it is not the most productive thing to do.

The Hobie 16 rig system is much more complex than the simple 2D force vectors than have been discussed here.

_________________
Sail More. Tinker Less. Enjoy a Hobie Day.
-2013 H16 #1`13780
-2014 Getaway w/wings,spinnaker,& trapeze

What is your actual experience with these halyards and mast rotation?

_________________
'00 H16 #104691
'78 H16 #32692 ex-rental [gone]
Old Holsclaw trailer
My Hobie 16 pages

It is interesting that this thread reanimated. I was the one in the initial page that challenged the Aussie Halyard claims- and my counter claims still stand- there is no change on the downward force applied to the mast (or the upward force applied to the step) with an Aussie halyard- smoke and mirrors. Likewise there is no change to the compressive force on the mast. If you tighten a shroud or halyard, regardless of the method, the force transmitted to and driving the mast downward, regardless of the jib halyard block arrangement, will increase as well.

As to mast rotation, yes that is affected by jib halyard and shroud tension- the Aussie rig doesn't change the force on the tang so it can't improve mast rotation. The only ways mast rotation can be improved are to (a) improve the step bearing, (b) attach the jib halyard and shrouds to masthead bracket or a tang that is free to rotate about the mast.

The only thing the Aussie halyard does is to make it easier to raise jib and adjust halyard tension. On the negative side, with the Aussie halyard you have a ton of excess halyard to stow somewhere once the jib is up.

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Alan
'86 H16, Sail #89057

What and where exactly are the claims that you are supposedly challenging? I think your terminology (and that of others) is loose, and you are making unfounded assumptions about what can and cannot affect mast rotation. The AH does not change pressure on the mast step; I think you have created a straw man on that point. If you think the mast rotation has to do with step friction or the like, you are TOTALLY missing it.

The catalog says, "Reduces mast compression by 66%. Allows easier tacking, better mast rotation and consistent mast bend!" Technically it reduces halyard-related compression by 66%, and although that is only a portion of the whole compression it has an asymmetrical component (important!) that is correspondingly reduced, not to mention that the halyard-related compression is reduced, asymmetric or not. Do you have experience with both? I do, I find better mast rotation and so do others.



I don't agree with that either... Raising the jib is far easier (for me) with the old system. Adjusting, OK that might be easier but it's more of a layout thing than it is related to the fundamental difference in the AH, which is where the 3:1 happens.

I think your position on this is entrenched and this is pretty typical of internet tech spats. Those who get the physics already know who is right and wrong, and you don't need to be an engineer to get the physics of it. But those who don't know might get something from what I've written. Or, read Matt's post at the top of page 2. He sums it up very cleanly.

_________________
'00 H16 #104691
'78 H16 #32692 ex-rental [gone]
Old Holsclaw trailer
My Hobie 16 pages

As I stated, I challenge the assertion that the AH reduces mast compression and improves mast rotation.

If you studied statics and dymamics you would understand.

Correct, exactly my point. That is until you haul on it!

"I think" you are severely misinformed.

Total BS! There is absolutely NO reduction in halyard-related compression. You are talking about a closed, static, and balanced system. Any tightening of the halyard or the shrouds puts a downward force vector on the mast and since the mast doesn't go anywhere, an equal and opposite force must push up on the mast through the step. When sailing those forces become dynamic but are still balanced - again I suggest you educate yourself on statics and dynamics. And yes, I do have knowledge and background in statics and dynamics. (I also graduated from a small engineering school located on the shores of the Severn River in Md.)
I wasn't talking easier for any particular operator, I was talking mechanical advantage- more sheaves, more mechanical advantage, less force required to tighten the halyard.

It sure helps to have engineering knowledge and understanding- it reduces the number posts like this.

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Alan
'86 H16, Sail #89057