Author Topic: Sail Design. Masthead/batten.  (Read 16691 times)

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Offline Hayley_Trim

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Re: Sail Design. Masthead/batten.
« Reply #15 on: January 15, 2013, 02:06:38 PM »
PS anyone got some foils from a Moth or RS600 they want to loan. I fancy lashing up a fully foiling Cherub just for fun!! Rolland could test it in case it proved dangerous.

Er, he can use someone other than his regular crew for the first trial!

Offline JP233

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Re: Sail Design. Masthead/batten.
« Reply #16 on: January 15, 2013, 07:48:02 PM »
PS anyone got some foils from a Moth or RS600 they want to loan. I fancy lashing up a fully foiling Cherub just for fun!! Rolland could test it in case it proved dangerous.

Funny, me and Digby were thinking of a foiling Cherub this weekend, we thought the Moth T foil wouldnt be too good, but the foiling 49er concept could be improved by replacing the 49er-bit with a Cherub and not having a cannard fin but using the normal Tfoil rudder to adjust pitch.

Not sure if this has been said or allowed, but why not make the gooseneck 'male' part on the gaff spar, then have a hole in the mast for it to sit in??

Thanks
Jamie
Thanks
Jamie

Offline ade white

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Re: Sail Design. Masthead/batten.
« Reply #17 on: January 15, 2013, 09:53:51 PM »
Thanks Jamie, that has immediately given me more ideas for developing the idea, and it might make it simpler for me to model the fittings.
So far I have a sail head fitting, a ring fitting, and a mast top swivel fitting. the male batten slots into all these as there is a female tube bonded onto each fitting. The fitting is only loaded from batten tension. Therefore the sail head forces will be neutral, compression forces on one side of the ring, and a shear leverage force on the masthead fitting.
I think it looks tempting to go for the sail-head fitting...
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Offline JP233

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Re: Sail Design. Masthead/batten.
« Reply #18 on: January 16, 2013, 04:56:03 PM »
No worries, i'm quite intrigued by this, have you got any pictures or drawings?

Thanks
Jamie

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Re: Sail Design. Masthead/batten.
« Reply #19 on: January 16, 2013, 05:04:00 PM »
Sounds like this can be simplified into more of an "uber batten" than a gaff if the "gooseneck"/ring/fitting can simplified into a bit fabric in a slot on the mast?
Another way of describing this would be to bolt/rivet/glue a plate onto the sail where the batten end protector in the luff normally sits to spread the load and attach your female socket onto this plate?

Offline ade white

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Re: Sail Design. Masthead/batten.
« Reply #20 on: January 16, 2013, 07:02:04 PM »
Yes that is exactly how the idea is going.  Def 'uber' For my first test it is a patch sewn onto the head with a tube fitting sewn into a pocket. The tube is at an elevated angle for the mast head batten. The idea would be for the tube (batten) to finish directly above the outer part of the sail head eyelet patch so as not impend any twist but allow the rotation I am hoping to create at the top of the rig. There would still be no downhaul tension here to effect or induce shape. The batten, I am currently thinking is similar to an ordinary tapered round section but more flexible. The head shape being very curved and also with more area than current mainsails. Batten length approx 2 meters with a chord bend of 45+mm ish.
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Offline ade white

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Re: Sail Design. Masthead/batten.
« Reply #21 on: January 19, 2013, 06:33:35 PM »
I have shown the attachment it is the drawing for the new main. The drawing shows the mast head batten sewn in tube stop insert just behind the headboard. approx angle of batten 45%

here is an interesting reply from my brother (i keep having to apologise as he sails a 'Nat 12' and is therefore to be considered 'still a virgin'!)
...should work from a sailing point of view, just how to get it there and hold it up.
I assume hoisted with boat flat. may need a line to support batten, but the batten could have a split end which goes around the head board in a way that stops the batten dropping.
headboard will need to rotate about the mast without popping the luff in way of the headboard out of the track so a gaff type approach would probably be better than a batten idea, headboard with a half tube to sit about the mast, in way of the head board the sail is not in the track, so just uses the halyard to hold the "headboard half tube" to the mast headboard half tube shapped at the botton edge to allow it to slide back down the mast
.
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Offline Clive Everest

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Re: Sail Design. Masthead/batten.
« Reply #22 on: January 19, 2013, 10:56:35 PM »
Hi Ade,
This looks interesting, however how do you see it being better than a more conventional top batten (gaff) arrangement.
I am worried that a few mm of movement at the base of the batten will be massively amplified at the tip, but if the batten was to start further down the mast you could still have the same head profile but it would be more tolerant of any inaccuracies.

Clive
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Offline ade white

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Re: Sail Design. Masthead/batten.
« Reply #23 on: January 20, 2013, 09:02:02 PM »
Hi Clive,
I see what you are saying there.
Further questions from me include... Is it less of a risk incorporating the batten pocket into the headboard?
Or are you thinking the design should have the batten running lower and more vertical to the luff before arcing to the leech but below the headboard?
My thinking is; (I have 5.9m from goose to mast tip) I can increase the height aspect of the rig; given that I can increase the area considerably.
To re-cap... I think the twist control will be benefitial as the head of the sail will be creating vertical 'tension' instead of initial tension being created by downhaul.
Am I right in believing we induce mastbend to create twist at the top? I am thinking this design idea might somewhat create a more even twist.
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Offline PaulClements

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Re: Sail Design. Masthead/batten.
« Reply #24 on: January 21, 2013, 08:00:04 AM »
There is a masthead utube video of a MPS that is enlightening. The top is alive, flexing and opening with every variation in the wind. Key however is how low drag it becomes as the mast flexes. It not only depowers but it does not hold you back when it depowers. Richard stenhouse was best at achieving this go fast setup. Stiff bottom mast section, loads of cunni then chase up with kicker to get desired twist. The top quarter of the mast bends till the top batterns are nearly straight making the leach unstable. In a gust the extra pressure on the leach just opens the top of the sail, depowering and adding almost no drag. An unusual sideproduct of this setup is that sheeting the main in harder overbends the mast and power deminishes . Sheet out and the power increases. Tricky.

The MPS has no uppers but I guess the principle is achievable with the Cherub. Remember if the leach is set soft when windy it is important that the unused sail area goes low drag.

Offline phil_kirk

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Re: Sail Design. Masthead/batten.
« Reply #25 on: January 21, 2013, 01:00:31 PM »
A well set up cherub rig should work in the same way.  The uppers have some effect but using cunningham should enable the top mast to bend aft and hence allow the sail to twist off.  If the uppers are softer this effect will happen earlier than with very tight uppers.

Just a little detail on the gaff arangement. If the headboard/gaff is set on a half tube that rotates round the mast the headboard will not be inline with the rest of the luff in the luff track on the aft edge of the mast.  This may cause wear to the luff of the sail or the mast track. 
This affect would be avoided if the headboard rotated around a point at the aft edge of the mast.  It is sort of like having a boom and gnav arrangement at the top of the sail.  Marmite's top batten tip is higher than the top of the mainsail luff. 


Offline ade white

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Re: Sail Design. Masthead/batten.
« Reply #26 on: January 30, 2013, 09:53:25 PM »
It looks as if i maybe infringed rules on the first attachment.
I have now posted one of the other idea developments. The headboard can be tension-ed independently from a lower eyelet that has now become the attachment to the top of the mast. A down-haul tension can be applied to the headboard for adjustment. In between is a cam batten and the batten is allowed to bend vertically as well as laterally to control the shape.
I think it may sound a bit fiddly however It is only 1 adjustment and can easily be worked on a flat side cleat system. This could give me the same control and area i am hoping to achieve... further food for thought!
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