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How long does a boat stay fast?

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Stefan Lloyd View Drop Down
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Post Options Post Options   Quote Stefan Lloyd Quote  Post ReplyReply Direct Link To This Post Posted: 16 Mar 05 at 5:30pm
It depends on the build quality and how light the class rules allow the construction to be. To take two contrasting examples, 470 hulls have a notoriously short competitive life before they become soft. Plastic Merlins last well because there is no point in building them ultra-light since they would then need to carry masses of lead to bring them up to class minimum weight,
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Post Options Post Options   Quote flat is fast Quote  Post ReplyReply Direct Link To This Post Posted: 16 Mar 05 at 5:58pm
i agree
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Post Options Post Options   Quote redback Quote  Post ReplyReply Direct Link To This Post Posted: 16 Mar 05 at 8:15pm
I think we've been through this before on this forum.  Boats that were designed to be made from wood tend to be fastest if made from wood.  They tend to have flat panels which are difficult to keep stiff if made from GRP, however techniques like foam sandwich, fancy fibres and epoxy resins are beginning to change this.
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 05 at 11:41am
i agree to
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Phil eltringham View Drop Down
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Post Options Post Options   Quote Phil eltringham Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 05 at 6:21pm

Indeed, it is only with the advent of the new carbon/kevlar cloths, better epoxies, and high modulus foam that hulls originally designed for wooden construction are regulaly faster made in FRP. 

The problem with 470/420's is that they are not sandwich construction as it is next to impossible to make the foam follow the curves of the hull nicely and still have good mechanical properties.  If you made them of carbon/epoxy instead of glass/ployester then they would last a lot longer, but it would make an already expensive boat stupidly priced. 

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Post Options Post Options   Quote Chris Noble Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 05 at 10:49pm
why bother, move to a development class, and go carbon or kevlar, no worries
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Post Options Post Options   Quote hurricane Quote  Post ReplyReply Direct Link To This Post Posted: 25 May 05 at 6:57pm

What is interesting is you all seem to follow the lines of a flexable boat is a slow boat, i heard that the finns are trialing less rigid boats that cut through waves rather than go over them. I have also heard storys where not sure what class it was but sailors would by new boats lend them to people to wear them in so not sure on this one.

It is interesting how a good sailor can get an old boat going well, alot of it is in the mind "Bad workman blaims his tools".

In relation to cats a stiff boat is fast they tend to flex between waves (this is why if u pick up the bow the other should lift at the same time with no delay)making it a fast boat. I know the off the shelf tornado's last about 2 years while the boats they used in the olympics are specialy made thinner but do not last as long. The hurricane 5.9  is built like the 4000 and just lasts forever with some top boats being over 10 years old now.

 



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lifes to short to sail slow boats!

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Post Options Post Options   Quote redback Quote  Post ReplyReply Direct Link To This Post Posted: 25 May 05 at 11:29pm

There might be something in making some parts of the hull flexible to gain speed but those parts involved in holding the rig up need to be as stiff as possible.  Perhaps a flexible Finn is not bad because the rig is already flopping all over the place.

My reasoning is that the rig is a bit like a spring and the more tension you put in it the more it harnesses the wind forces.  Above a certain wind speed your are quite happy to lose some of those forces and the rig tension (among other things) determines at what speed this begins to happen.  If the boat bends under rig tension you may not be able to get enough tension to get all the power you need.

The Finn is a bit different with the rig being floppy all the time (except for some stiffnes in the mast) but plenty of sail area to make up for it and precious little leverage anyway.

A Laser 4000 can take a lot of rig tension and area for area its sail produces a lot of power.

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Post Options Post Options   Quote Phil eltringham Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 05 at 9:21am

If I'm wrong please correct me but I always figured that the more a boat planes across the wind range the stiffer if needs to be, partly due to the higher rig tensions used by styed rigs, and also because of the dynamic pressure on the base of the hull

N.B.: Just as a ball park figure the pressure on the surface of the hull at about 20-25 knots is three times atmospheric pressure, this is the same as the static presure 30 meters below the water's surface. 

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Post Options Post Options   Quote Phat Bouy Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jun 05 at 2:56pm
The stiffness of a hull also depends on factors such as what materials the stiffeners are made from. A hard wood stringer is better than a soft wood one. The use of super fibres such as diolene, kevlar, carbon are very flexible lengthwise. However chop them into very short strands and arrange them such that they run vertically (what used to be called end-grain, as in balsa wood) and they are as solid as a brick. At the end of the day a wooden boat is made from just wood, a FRP boat has fibres and resin and the two are not as homgenous as all wood.
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