Unstayed masts or stayed masts?

[Fard12]

The shell weight of a Wilderness 1230 is 140KG. The all up weight is approx 260kg including furler, rigging (standing and running) boom, light package TV aerial, VHF and cable (12mm) and provision for a radar on lower spreader.
The cost of a rig for this boat is $29500.00 approx including furler and mast RCB cars and striker wire.
Deck hardware and winches extra.
Mast rigging should be checked by the owner constantly and by a rigger every year or so.
Wires should be replaced depending on mileage every 7 or 8 years.
The mast should last for the life of the boat.

[rob denney]

Originally Posted by Fard12

The shell weight of a Wilderness 1230 is 140KG. The all up weight is approx 260kg including furler, rigging (standing and running) boom, light package TV aerial, VHF and cable (12mm) and provision for a radar on lower spreader.
The cost of a rig for this boat is $29500.00 approx including furler and mast RCB cars and striker wire.
Deck hardware and winches extra.
Mast rigging should be checked by the owner constantly and by a rigger every year or so.
Wires should be replaced depending on mileage every 7 or 8 years.
The mast should last for the life of the boat.

G'day,

Thanks Fard12.

Looks like we can put a couple more unstayed mast myths to bed.

An unstayed carbon mast tube is near enough the same weight as a bare aluminium tube for a stayed rig.

An unstayed carbon main only rig is significantly lighter, with a much lower centre of gravity. The rig on it's own is a little more expensive, although a lot of the extra is painting and fairing which could be done by the owner.

Include the weight and cost of the forebeam, chain plates, traveller, sheet winches, track, headsail and all the beefing up these require versus the beefing up of the deck and the larger mainsail on the unstayed rig and the unstayed rig is much cheaper and lighter.

The biplane boats will be lighter, with a lower centre of gravity (less pitching) and maybe a little more costly if we fair and paint them.

Against this are all the advantages i mentioned earlier and the near certainty that they will never fall down.

Now, just got to get the shop up and running. ;-)

regards,

Rob

[Fard12]

When I look at a carbon mast as opposed to alloy it’s shell weight is generally around 45 to 50% of that of an alloy extrusion as a stayed rig.
I am no engineer so can you explain to me how a freestanding carbon mast can have the same weight as a stayed carbon mast.
Although the freestanding mast is shorter in length it is still working with the same moment in the boat. (RM to a hull-lifting angle of 11deg)

[rob denney]

G'day,

The reasons for the unstayed mast being as light as the bare tube for the alloy stayed masts are as follows:

1) The unstayed mast is bigger in section. As stiffness goes up as the cube of the thickness, a tube twice as wide is 8 times stiiffer. The bigger section is more drag, unless it is a wing section, where it improves the sail as well as being easier to control and much less windage.
2) The unstayed mast only has material where it is required and tapers to about 20% of max diameter, the alloy tube is the same section and wall thickness all the way up.
3) Stays exert large compression loads, which mean the tube must be strong enough in compression, with walls thick enough not to buckle and to attach fittings to. Meeting one of these criiteria will usually mean the other is over size.
4) carbon is 6 times stiffer than alloy for a given weight.
5) The stayed mast is stiff, the unstayed one has some flex.
6) Our carbon tracks are about one tenth the weight of the extruded ones on your tubes.

Just to rub salt into the wound, the carbon masts we build have glass on the off axis layers. This keeps the cost down, but at the expense of about 20 kgs in the case of the mast in the video.

Fard12, are you in Brisbane? If so, I would like to show you some samples when we are up and running. Please drop me a line at harryproa@google.com if you are interested.

regards,

Rob

[catty]

Mmmm, So if one is happy to slop around down wind and not carry extras (Spinaker , Screecher etc) the unstayed rig has very low compression loads.

As soon as these extras are added we have a problem unless we add more carbon, increase section size etc etc. Up goes the weight, cost etc and suddenly we are comparing two rigs ( one unstayed and one stayed) that have the potential to fly similar sail areas.

As the unstayed mast is tapered , as soon as you reef the main the sails luff curve no longer matches the mast bend for the lower Section of spar it is now setting on (effectively now a stiffer spar), so now it sets like crap. I suppose you can't have everything. Setting extras from the bow certainly assists in moving the center of effort to where it can be put to best use, self steering , boat balance etc for free legs of the course.
Gee, at the end of the day if it was so efficient we would be seeing it on racing boats. Were not.

Try visiting scrumble.com, the oram 44c build site and see if you can work out what happened in the "carbon mast update 2" post.

[Whimsical]

Originally Posted by catty

Try visiting scrumble.com, the oram 44c build site and see if you can work out what happened in the "carbon mast update 2" post.

Nothing to work out I know what happened and nothing sinister can be impllied as to the construction or suitability.

Mike

[Fard12]

I am interested in your carbon tracks. Do they match the Harken or Ronstan systems?
If so what series?
As far as the free standing masts go, they do work as I have seen them in boats over a lot of years.
However as far as performance goes give me a conventional mast in alloy or carbon any day.
Cheers Fard12

[rob denney]

G'day,

Catty, there is no reason why a spinnaker cannot be flown on an unstayed mast. A screecher won't work very well, but most cruising boat rigs are not designed for masthead screechers either. If you need extra sail area I would suggest going with a taller unstayed mast (very cheap and light compared to a taller stayed mast) and more main sail area, a biplane rig or an Outleader kite.

The first reef happens automatically on an unstayed mast as the mast flexes. Any mismatch between sail and mast on the deep reef is more than offset by the reduction in drag from not having all the stays and spreaders of the stayed rig. This is why few cruisers (Mr Joli in his 60'ter being one of the exceptions) can actually sail to windward under deep reefed main.

Scrumble paid us a 50% deposit, weren't happy (understandably) with our completed price, so I returned the deposit. The arrangements made with the purchaser of the masts are neither Scrumble's business nor yours. As far as I know the photos on the Scrumble web page were taken when the masts were completed. I have no idea why there is no date on them, nor why that is relevant. As they are still planning to use unstayed masts, and we are the only people building them for less than an arm and a leg, I hope we will be asked to quote once they are ready and we are in a position to build them. We intend to be a lot more professional with our pricing than we were last time.

There have been a few unstayed mast race boats. The Wylie 30's on San Francisco Bay do very well, Team Phillip's was blindingly fast until the hulls fell apart and Krazy Coyote was quick enough to be banned. The cruising proa in the video gets along better than any cruising cat or mono of similar sail area, weight or space so I don't think poor performance is an issue. Race boats not using them is evidence of nothing except how staid race boat owners are and how anti innovation their rules are.

By the way, you still haven't supported your scurrilous comments about harryproa builders on the "Sailing a proa" thread. Don't suppose you could either do so, or admit you are full of the smelly brown stuff and delete it?

Fard12, the tracks can be made for any rcb system, we actually designed and built our own non rcb cars from UHMWPE as there is no need for rcb if the mast always points into the wind for raising and lowering. You can see a picture of the track at harryproa / Visionarry - report 12 January 2006 or look at the Visionarry video on You Tube. However, they have not had any long term testing, so it is very much buyer beware at this stage. If you are in Brisbane, I will bring across a sample next visit.

As for racing, if the boat is designed for a free standing rig from the beginning it will be a lot more competitive than a retro fit to a stayed mast boat sailing to a rule designed for stayed masts. For cruisers, the last per cent of speed from continual tweaking of the sails is not such a big deal. For them, the low cost, ease of handling and lack of maintenance make unstayed a no brainer.

regards,

Rob

[dana-tenacity]

Also zero chafe from sails touching the wires.

[Fard12]

Hi Rob,
I had a good look through your site and you have done a good job.
The boat sailing off South West rocks looks to be performing well.
There were no white caps so I am assuming that less than 15kn’s of true wind and a slight sea. The bow of the leeward hull seem to push through ok however I would be interested to see the performance in 25kn’s and a 2 to 3 mtr sea.
Fard12

[44'cruisingcat]

Originally Posted by catty

Try visiting scrumble.com, the oram 44c build site and see if you can work out what happened in the "carbon mast update 2" post.

Wrong web adress. It's :

http://www.scrumble.com.au/

[scrumble]

Thanks 44'cruisingcat, you beat me to that correction.

BTW your boat's looking great, well done.

Tom

[BigCat]

Ask the guy who sailed across the Pacific with them-me-I love them. Then are going on the next boat, a 65 foot catamaran. Engineering cost-$1000. Materials cost for two 70' masts each flying 1200 sq. ft. of sail -about $16,000 USD each in carbon fiber, with some e-glass for torsion, and vinylester resin. Mast caps extra, can be laminate or metal.

[lounge sailor]

Hi. Long time listener first time caller

In 98 we replaced our ageing stayed rig with a prepreg carbon free standing mast on our equally ageing Spencer 42. A big sister to Hal Roths original “Whisper”

I wrote an article detailing the whole event for Ocean Navigator magazine which was published in the May/June 1999 issue #98.

Since we built the mast our selves from scratch including the work on the deck and hull most of our costs were materials. When the dust settled our cost for everything from the deck up with new sails came to about five grand less than the cost for a CT 37 project which was happening at the same time here in Vancouver. The 37 was cutter rigged, double spreaders with all new hardware, rigging, mast and sails. All professionally done.
If we had hired out the work it would have been beyond our budget by a wide margin.


The gentleman we hired to design the mast, its section, lam schedule and new sail plan was Eric Sponberg a yacht designer and certified engineer working out of Newport Ri. at the time but now based in Florida. He has a lot of experience with free standing rigs as well as carbon and was a key asset to the whole project. His contribution was worth every penny and more!

A free standing mast like its stayed brethren has its advantages and disadvantages. Having sailed all my life in stayed rigs and the past 9 or 10 with a proper free standing rig I probably would steer clear of stayed rigs on my own boats if at all possible, but, hey, never say never!

The primary disadvantage is up front cost and from my point of view it is probably the only disadvantage.
Most people are familiar with the freedom rigs. In order to keep labour and materials costs down to a reasonable number they were built on what were essentially aluminium flagpole mandrels.
This geometry is one of the worst shapes one can have on a free standing mast. The bending characteristics are way out whack for designing a sail with decent shape. It can be done of course. Building to a price they really had no choice.
It is to the sail making industries credit that the damn things can sail at all. My suspicion is that the geometry of these kind of masts do nothing to help the sail maker confronted with building a sail for these things.

Eric’s design called for a elliptical shape with a modified entasis shape (think the top half of a Greek column). A series of changing tapers. Not a single taper like a cone or flagpole). As a result the old bucket goes upwind as well if not better than most boats its size.
The new mast is about 9 or 10 feet taller than the old one. which means the rig is about 60 to 80 pounds heavier than the old deck stepped rig all up. The Centre of gravity is almost 3 feet lower than the old rig so they kinda cancel each other out.
If we were to do it again both Eric and I feel we could shave another 60 to 100 pounds off the final weight.
The work on the hull and deck was considerable and took us about three weeks full time to complete Suffice to say that there is a lot of carbon, Knytex and glass where there wasn’t before. All told we used almost 20 gallons (finished/mixed) of epoxy nicely squeezed out I might add, to complete the hull/deck modifications.
We had a lot of fun doing this project, met a lot of cool people, and are still having a ball sailing the old bucket.
We sail a lot and have put the rig and boat through many miles of sailing in a wide variety of conditions. Not one single creak or groan from the rig. The spartite occasionally squeaks a bit and the mast and halyards hum going upwind in a blow with too much sail up. That’s about it.
One thing we didn’t anticipate was how quiet the rig is in high winds ( to date 58 knots true). No screeching and howling in the rigging. Because of the relative quiet we tend to make less hurried and more relaxed decisions. That alone was worth the price of admission.
Handling the boat is much easier than the old rig since we can get her to go with just the main up. Tacking and gybing is a snap in close quarters. Mind you in light airs, 3 to 4 knots true we sometimes have to “snap” the big roachy full batten main over to the opposite side.
Depending on the situation often the first reef is to furl up the jib. It’s great because you don’t have to put down your coffee to tack.
We find we are reefing at around the the same wind strengths as before. We also find that we rarely use the traveller anymore, it is mostly the mainsheet and vang. With a bit of outhaul and cunningham.

We still get jokers coming up and telling us that it won’t work and will fall down. Its always fun to see the variety of shapes and sizes experts come in. Its also fun planting these same jokers when we cross tacks with them out there.
Most people are genuinely interested though and if we have a moment we love taking them sailing.
Not a project I would recommend on a whim. We were just so damn curious, to not do it would have driven us nuts.. Nowadays I just get tired thinking about the whole thing.
So, yes Virginia some kook actually did this and survived.
Hope this adds something to the mix and answers a few questions.
One other disadvantage to this rig is any knowledge I had regarding stayed rigs has atrophied, badly!

Cheers,
Bryan

[GordMay]

WELCOME aboard, Bryan.
Great first post!

See Eric Sponberg’s article (“FREE-STANDING MASTS”) about Bryan’s new free-standing mast for “Copernicus”.
Copernicus