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Sam.Spoons View Drop Down
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 19 Dec 18 at 4:34pm
Originally posted by getafix

I'm also wondering if un-stayed rigs enable cheaper hull construction, in the same way daggers versus centerboards, as although the loads are roughly equivalent, you don't need to resist the forces from shrouds/lowers in the side decks as well as at mast foot & gate level and you don't have to factor a forestay loading into your bow design?

I'd have guessed more expensive as the loads are concentrated in one area and the cantilever effect multiplies the loads at deck and keel level compared to up at the CoE of the rig.
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 19 Dec 18 at 4:42pm
Well as part of my needing to practise wiring I fitted trap wires to the jolly old EPS of joy, it has a two part mast, although I seem to remember fitting the wires below the joint, it has so far done the job, not that I've dealt with any serious wind using it, that's what the Farr works best in.

This reminds me of my quest for cheaper carbon masts, given the average cost of 6 mtrs of raw carbon tube can be had for as little as £130.00 I've always felt two grand is just a little excessive in what we're expected to pay for masts and I've yet to come across anything particularly sophisticated, nor its bend curve actually matched to the luff curve of any given sail, that may be the case in some other classes, naturally I've never studied the Finn which is rumoured to have quite 'trick' masts, but I bet they don't even try for a designed luff curve mismatch.

It's such a pity classes don't come together to discuss their mutual needs, take the Streaker for example it needs a carbon mast, they're all lightweights, arguably there's a case for the Solution going down the carbon mast route and don't even mention the Solo.. If there were a consortium of classes, then the boot could be on our foot instead of the other way round and we get a grip of these stupid prices y'all get conned into.
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 19 Dec 18 at 5:04pm
Finn and OK masts are pretty sophisticated these days and we've been matching the bend and luff curve since they were made of wood. With a wooden stick you could easily alter the stiffness/curve by the simple expedient of gluing on timber battens or planing them off again. With ally masts the stiffness curve was fixed and the sail had to be cut for a specific mast. I suppose Carbon would allow the mast to be adjusted again but suspect none are.
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 19 Dec 18 at 6:22pm
I've never ordered a mainsail for any mast, tin or plastic, without doing the measurements of spar bend. Its routine in the development classes.

And yes, its by no means unknown to customise a carbon spar to change the bend. I've done it. Of course you need a new or possibly altered sail to match the altered spar.

Edited by JimC - 19 Dec 18 at 6:36pm
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Post Options Post Options   Quote getafix Quote  Post ReplyReply Direct Link To This Post Posted: 20 Dec 18 at 12:20pm
Originally posted by Sam.Spoons

Originally posted by getafix

I'm also wondering if un-stayed rigs enable cheaper hull construction, in the same way daggers versus centerboards, as although the loads are roughly equivalent, you don't need to resist the forces from shrouds/lowers in the side decks as well as at mast foot & gate level and you don't have to factor a forestay loading into your bow design?

I'd have guessed more expensive as the loads are concentrated in one area and the cantilever effect multiplies the loads at deck and keel level compared to up at the CoE of the rig.

I wonder about this.  No doubt you are right about the load concentration being different.  Keel is always a reinforced area anyhow.  I doubt the hull cost being higher if you use a higher collar/deck gate, as with OK, Aero, D-Zero.  Reinforcement at the mast step/mast gate level is surely preferable to bow or typical areas where the shrouds would be located?  Could it be that un-stayed masts enable cheaper hull construction and less weight at the bow/max-beam areas?
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 20 Dec 18 at 1:32pm
By and large with dinghies my experience, FWIW, is that by the time you have a hull shell that has adequate panel stiffness and dent resistance there isn't an awful lot more needs to be done to the skin. Given the extreme rigging loads used these days you do need to control compression loads, but an awful lot of that can be done by good design at deck level. I've never really thought about what loads might be like on an unstayed rig, it seems so inferior from POV of rig weight, mast size, bend control etc that I've never really considered it.

Now I think of it I tend to use mast posts/stumps, and that possibly has some of the same structural challenges as an unstayed rig. The concern with the post is handling very large kicking strap loads. The post on my Cherub was in fact the bottom of a Finn mast reinforced, but above the post the real spar was way lighter and thinner than any unstayed mast.
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Post Options Post Options   Quote E.J. Quote  Post ReplyReply Direct Link To This Post Posted: 20 Dec 18 at 5:19pm
I vaguely remember a trapeze boat introduced called the Delta 14. We had a demo at our club an I recall it was unstayed with a mega thick ally bottom section and laser style hole in the deck to step it. I wasnít very nice to sail and diapered quickly. So it can be done, but donít.

I may have dreamt all of that, it was in the mid nineties and was usually sailing with a stinking hangover and hallucinating.
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Sam.Spoons View Drop Down
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 20 Dec 18 at 5:49pm
Originally posted by E.J.

It wasnít very nice to sail and diapered quickly. So it can be done, but donít.

I guess it was a bit cr@p?

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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 20 Dec 18 at 7:06pm
The delta as at the dinghy show. Huge mast.

I like the simplicity of an unstayed rig, even if less efficient. And I like letting the boom go forwards without hitting the shroud.

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