Carbon Spars on Multihulls

[lolanreg@smartc]

hi Rob Denney, I think I bought some Epoxy anti fouling from you some years back,92 first to use it in the mould of my Inspiration Ten at Bulimba/ Brissie. Hope your leap forward into Carbon masts goes well in October. Reg Harris

[bayview]

Does the added weight aloft in an alloy mast section have any positive benefits?

I notice that archery bows have stabilizers consisting of long rods with weights on the ends. Also from the disastrous Fastnet race we all learned that when monos lost their rigs (stabilizers) they pretty much rolled over and over again. One only has to hold a broom stick above ones head and wave it around to notice that if you tie a brick to the far end it is much harder to flick around.

So the question I'm asking is , as a multi-hull doesn't heel much ,the weight aloft is not such a big deal as it is for a mono, so therefore does a carbon mast provide much of a noticeable performance gain as it does on a heeling mono.


regards

[rob denney]

Originally Posted by lolanreg@smartc

hi Rob Denney, I think I bought some Epoxy anti fouling from you some years back,92 first to use it in the mould of my Inspiration Ten at Bulimba/ Brissie. Hope your leap forward into Carbon masts goes well in October. Reg Harris

G'day,
Indeed you did. Thanks for the kind words. I will keep you informed about the Great Leap. Still waiting for visas to be sorted out. China has practically closed for the Olympics/paralympics.

regards,

Rob

[Tropic Cat]

Rotating, free standing mast on a small catamaran.

[BigCat]

Originally Posted by bayview

Does the added weight aloft in an alloy mast section have any positive benefits?

I notice that archery bows have stabilizers consisting of long rods with weights on the ends. Also from the disastrous Fastnet race we all learned that when monos lost their rigs (stabilizers) they pretty much rolled over and over again. One only has to hold a broom stick above ones head and wave it around to notice that if you tie a brick to the far end it is much harder to flick around.

So the question I'm asking is , as a multi-hull doesn't heel much ,the weight aloft is not such a big deal as it is for a mono, so therefore does a carbon mast provide much of a noticeable performance gain as it does on a heeling mono.


regards

Probably the main advantage is less pitching, to which cats are prone.

[bayview]

Originally Posted by BigCat

Probably the main advantage is less pitching, to which cats are prone.

So the main advantage is to windward when pitch can be a problem. So one pays the substantial extra money for a carbon mast and reaps a small benefit sailing on the windward legs, Which for a cruising boat isn't that often with good passage planning, and these days most cruisers fire up the motors on the windward legs to motor sail and get the uncomfortable bit over as quickly as possible.

So it appears as though extra performance can be gained more cheaply by buying better sails maybe, than going the carbon mast route.

[Eleven]

For the Cats there is often a problem getting enough forestay tension, known problem with the Prouts.
Adding a couple of feet as a splice at the foot of the mast is the cheap way of getting more sail area for light winds.
Putting a frame across the back end and adding or moving the stays backwards may cause problems with the boom and main missing the stays when running but will stiffen up the rig considerably, give space for gismo's like solar, wind, radar, antenae, dinghy hoist and get the traveller up there and there's more space on deck too.
Nobody has done it yet? Some body must have, somewhere.

[rob denney]

Originally Posted by bayview

So the main advantage is to windward when pitch can be a problem. So one pays the substantial extra money for a carbon mast and reaps a small benefit sailing on the windward legs, Which for a cruising boat isn't that often with good passage planning, and these days most cruisers fire up the motors on the windward legs to motor sail and get the uncomfortable bit over as quickly as possible.

So it appears as though extra performance can be gained more cheaply by buying better sails maybe, than going the carbon mast route.

G'day,

If this is the way you sail, the money would be better spent on a bigger motor and more fuel. Spending it on better sails will not help your reaching and running performance appreciably.

regards,
Rob

[Nordic cat]

If I was going for a new mast primary reason would be to get better sailing performance, so the mast would be taller.

This means new sails or large modifications to the exsisting.

The next logical step would be to go for a rotating wing. for the added lift.

Following through on this logic, the next step would be to go unstayed, this is of course not so easy on a replacement job as on a new build.

On a new build, an unstayed rig is the way to go IMO - it's as logical as choosing a multihull in the first place. Isn't it the logic of not lugging tons of metal around at an uncomfortable angle that led us to choose a multihull?

So my conclusion is: Unstayed rotating wingmast(s)


cheers

Alan

[ireaney]

Hi Alan
I can understand on your new design ie a mast on each hull that if it is unstayed you will be able to support it on the bottom of the hull and easily make the deck of the hull where the mast protrudes very strong.
In the case of a standard rig, I assume that the unstayed mast would need to come through the cabin roof (strengthened immensely!!!) to be able to give it some support, also if rotating would the bottom half be sleeved/protected in a way so that if inside the cabin occupants would not be able to touch the mast itself.
Or am I totally missing the point on how the unstayed mast would be supported.
Cheers
Ian

[Nordic cat]

Originally Posted by ireaney

Hi Alan

In the case of a standard rig, I assume that the unstayed mast would need to come through the cabin roof (strengthened immensely!!!) to be able to give it some support, also if rotating would the bottom half be sleeved/protected in a way so that if inside the cabin occupants would not be able to touch the mast itself.
Or am I totally missing the point on how the unstayed mast would be supported.
Cheers
Ian

Hi Ian,

You're right, the cabin roof would need reinforcing. I think John Shuttleworth did a write up on the 52 ft balestron rigged cat that he designed. He designed a kind of monocoque frame structure.

The part of the mast that goes through the cabin should be enclosed in something, also to avoid leaks, as well as avoid rotating parts, if it needs to go through the saloon. Most masts are now at the leading edge of the saloon, so maybe not an issue.

Unstayed masts don't need much "bury", so given standing headroom in the saloon, then a mast of more than 20 m wouldn't be a problem.

There are a number of unstayed masts on cats. I can find some pictures if you like..

I personally like the Balestron rig, as shown in post 34 above, if it is a single mast rig. If designed to carry a gennaker for lighter winds, then you won't find an easier or simpler rig IMO.

cheers

Alan

[BigCat]

Originally Posted by bayview

So the main advantage is to windward when pitch can be a problem. So one pays the substantial extra money for a carbon mast and reaps a small benefit sailing on the windward legs, Which for a cruising boat isn't that often with good passage planning, and these days most cruisers fire up the motors on the windward legs to motor sail and get the uncomfortable bit over as quickly as possible.

So it appears as though extra performance can be gained more cheaply by buying better sails maybe, than going the carbon mast route.

Well, pitching is, if anything, more of a problem when motoring to windward than when sailing to windward. You are right, however, in stating that carbon fiber masts aren't the performance enhancer in multihulls that they are in monohulls.