[MHml] Catamarans

[Mark Stephens]

IT would but keeping it vertical leaves room for the sails, furler etc. It
also puts the load down through the beam web in composite spars. Having it
lean back would put a shearing force at the striker base rather than just
compression.

Mark

...................................
Mark Stephens
www.harryproa.com 


-----Original Message-----
From: multihulls-bounces at steamradio.com
[mailto:multihulls-bounces at steamradio.com] On Behalf Of Dave Culp
Sent: Friday, 8 September 2006 9:29 AM
To: Informed discussion of multihull issues
Subject: Re: [MHml] Catamarans



So, riddle me this, o learned one. Why is a seagul striker typically aligned
vertically, and not in line with the force it is resisting, which is
parallel with the forestay? A simple answer might be that the typical
crossbeam is elliptical, with sufficient bending resistance in a fore-aft
direction, but really, wouldn't it make more sense to align the striker with
the force itself?

Just wondering...

Dave

On 9/7/06, Roy Mills <rsirfj at shaw.ca> wrote:
> At 12:33 PM 9/7/06, you wrote:
> >And here, I was going on the rather pedestrian viewpoint that a 
> >striker of either family was actually an extension of one of the 
> >horizontal beams and not the sprit at all.
> >
> >Apparently, it is also referencing any vertically aligned structural 
> >element that gives triangulated strength to any given beam component. 
> >Note to self: fix terminology filings.
>
>          Well said Chris. I was going to have chipped in to say that a 
> dolphin striker in my experience is a downward pointing pole, with a 
> mast step on top and a wire or other metal bracing element underneath, 
> the pole taking the pressure from the mast and transfering it down to 
> the metal brace underneath, which in turn transfers the strain back up 
> to a strongpoint on each hull.  Dolphin strikers originally were found 
> on old time ships which had a pole pointing downwards underneath the 
> bowsprit or jib boom to give a better angle of resisting pull to a 
> line leading from the end of the sprit or boom back to the bow. The 
> bowspit or jib boom was being pulled upwards by tension from stays or 
> halyards from foresails fastened to it, so the dolphin striker helped 
> resist that upward pull. Since dolphins played around the bows of 
> ships and the downward pointing pole often plunged into the sea as the 
> boat  pitched, it became called the dolphin striker, in joke.
>
>           Catamarans need a similar triangulated structure to brace 
> the front crossbeam against the pull of the foresail and jib halyard . 
> In this case the pole points upwards and presses against the centre of 
> a wire bridle leading from one end of the front crossbeam to the 
> other, so it is called a seagull striker.
>
>          And no, I don't think we automatically call a cruising 
> catamaran ugly, it is just that to get all that accomodation and 
> standing headroom into the available dimensions they tend to look 
> somewhat clumsy in comparison with one which is not built for charter 
> but for greater speed and can look more graceful.
>
>           You will soon get the hang of the names of the sails and 
> rigging, most of them go back hundreds of years to rather different 
> boats, but tradition being what it is, the old names still get used, 
> like dolphin striker.  Seagull striker is a newly coined name based on 
> that old one to suit something sticking up into the air rather than 
> down towards the sea.
>
>          I can't comment on Rolly Tasker sails these days. Some years 
> ago their reputation was for quite good sails at a low price, 
> therefore good value for money on that basis, but not the best sails 
> for a more demanding sailor.
>
>          Roy Mills
>
>
> _______________________________________________
> >Alter your subscription details or unsubscribe at the bottom of this 
> >page: http://www.steamradio.com/mailman/listinfo/multihulls
> >
> >Multihulls mailing list      (Multihulls at steamradio.com)
> >
> >
> >
> >--
> >No virus found in this incoming message.
> >Checked by AVG Free Edition.
> >Version: 7.1.405 / Virus Database: 268.12.1/440 - Release Date: 
> >9/6/06
>
> _______________________________________________
> Alter your subscription details or unsubscribe at the bottom of this 
> page: http://www.steamradio.com/mailman/listinfo/multihulls
>
> Multihulls mailing list      (Multihulls at steamradio.com)
>
>
_______________________________________________
Alter your subscription details or unsubscribe at the bottom of this page:
http://www.steamradio.com/mailman/listinfo/multihulls

Multihulls mailing list      (Multihulls at steamradio.com)