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#151823 - 08/07/08 09:32 PM Re: sshhh [Re: ncik]  
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JeffS Offline
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It has a fixed ali frame similar to Wouters F12 that holds one swing down centreplate. I'm not a fan of that metal. The Arafura and Arrow were designed by the same designer as the Mozzie and that was a mini Stingray which was a mini Tornado. I really bought up the weight to show that in my opinion the modern boat should be lighter as per the original discussion with the F12 design. Specifically a cheap cat that kids can rig themselves, light weight, practical, exciting to look at, safe easy to homebuild cat.


Jeff Southall
Nacra 5.8 1667 Ram Raider
Nacra 18 Square
Taipan 5.7 134
Mosquito 404
Arrow 1576
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#151824 - 08/07/08 10:19 PM Re: sshhh [Re: JeffS]  
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ncik Offline
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As a comparison, the lightest carbon foiler moth hull ever made was 6.9kg delivered. After some time it increased to about 9kg which is similar to what most new foiling moth hulls are built at now in pre-preg carbon and foam (Fastacraft advertise 9.5kg once painted).

My mates and I have built a hand-laid glass foam moth hull which started at about 12kg and ended up about 14-15kg once we made local repairs where it wasn't strong enough (mast chock, transom).

Moth hulls are of a similar size to F12's and these bare hull weights are in the vicinity of what the F12's are being designed/built to.

So I don't think there is much weight to save in the hull structure. Centreboards and rudders are pretty well known so not a lot of weight to save there. Beams - going to carbon is an option to save weight but cost could be an issue (filament wound tube 50 x 2.5 x 1330mm = $350). Not much weight to save in the rig without going to a carbon mast or light sail materials.

High technology and low cost for home builders are opposing goals.

Carbon Fibre Express

#151825 - 08/07/08 11:17 PM Re: sshhh [Re: ncik]  
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Nothing high teck Ncik Rg and Scarecrow went to a lot of trouble with their designs to keep weight down. Gato built his "heavy" with 4mm instead of 3mm ply and used wood inside his mast instead of foam. The boat came out perfect in my opinion. RG's boat will probably weigh even less, the new class rules want more weight instead of being the original design weight of under 50kg.
regards


Jeff Southall
Nacra 5.8 1667 Ram Raider
Nacra 18 Square
Taipan 5.7 134
Mosquito 404
Arrow 1576
#151826 - 08/08/08 03:20 AM Re: sshhh [Re: JeffS]  
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Wouter, the 100 kg is the all up weight
I should explain that as this isn't a one design class I offer the same basic design in displacements of 100, 110, 115, 120 and 130kg, all you have to do is ask for the displacement you want. Much over 130 and I think it will be a pig, so Im not going to do anything past that number.
The 4 boats that Billy is building now are all the 100 kg version and if you look at the link to the multihull article and the pics of the kids in it....none are remotely close to 50kg yet and probably won't be for quite some time to come, so that version will suit them.
As for boat weight, I don't think the finished boat will make 50kg, probably closer to 46kg when I last redid the numbers, so the design as it stands look right at a max of 54kg for the crew and probably won't be sailed at that weight for some time yet.
Cheers
RG

#151827 - 08/08/08 04:27 AM Re: sshhh [Re: JeffS]  
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Wouter Offline
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Last time I checked the weights of these and similar classes the quoted weights didn't included everything needed to go sailing. There tends to be a tradition of quoting weights that only comprises a hull or the platform and present that as a boatweight. The newly launched Weta is the same. It is quoted at 85 kg but independently measured at 126 kg.

So you are confusing the matter here Jeff; you should have know that the Arrow rules actually state :

Quote

hull and beams shall be dry when weighed and include fixed fitting only.
Centreplate, complete rudder assembly and all removable fittings and sheets shall be removed. Minimum weight 50 kg. Weight correctors are permitted but must be bolted inside the hull to main frame in an easily accessible position (max 3kg of lead permitted).


Source : http://www.arrowarafura.com/Arrow%20Restrictions%20-%20current.pdf

We have to compare apples to apples here. The proposed minimum weight for the F12's INCLUDES EVERYTHING NEEDED TO GO SAILING, as is THE standard in a formula class.

Basically, any F12 coming off the water with the water drained and the sand rubbed off must go past this limit when put directly onto the scales. The Arafure and Arrow have significantly different weight definations and will be significantly heavier in their ready-to-sail attire. Didn't we cover this several times before already, when are people going to pay attention ?

Additionally, the F12 was never started as a showcase of "modern engineering" remember. It is supposed to be a low-cost, good looking and generally available, but yet effective and performant, entry catamaran.

Wouter

Last edited by Wouter; 08/08/08 04:32 AM.
#151828 - 08/08/08 04:40 AM Re: sshhh [Re: JeffS]  
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Wouter Offline
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Quote

It has a fixed ali frame similar to Wouters F12 that holds one swing down centreplate. I'm not a fan of that metal.



How many times can you be wrong in one thread ?

My F12 DOESN'T have this metal work. It only has an unstayed mast that is supported by two 30x2 mm pushrods of 1.5 kg combined weight including fasteners.

I agree with the others here the Arafure Cadet will be heavier then the F12 when it is ready to be sailed so your point is mute.

May I advice you as a well intending person to do your research more thoroughly the next time. No-one is benefiting from any wild goose chases that are based on falty intepretations.

Wouter

Last edited by Wouter; 08/08/08 04:41 AM.

Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#151829 - 08/08/08 04:50 AM Re: sshhh [Re: JeffS]  
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Wouter Offline
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Like I said how many times can you be wrong in one single thread ?

Quote

the new class rules want more weight instead of being the original design weight of under 50kg.



I'm working on these rules right now; most working on the wording rather then the numbers or intent of the rules and your "assumption" is unfounded. The F12 never had an orginal established weight rule as we never reach agreement on it till recently. But even in the proposed rules the ready-to-sail weight was never "under 50 kg"; I don't know where this perception is coming from. The most original F12 rule come from me and had a 60 kg minimum weight limits, that in fact WILL BE lowered in the new class rules as a result of the recent discussions on this matter. So as a FACT the new (proposed) rules will indeed "want" less weight rather then more as you have errornously stated.


Forgive me my inflammatory style of writing but I have a hard time "understanding" anyone making a fuss without having checked the validity of his claims before hand. And checking your facts is such a simple thing to do with the internet these days !

Wouter

Last edited by Wouter; 08/08/08 05:05 AM.

Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#151830 - 08/08/08 05:00 AM Re: sshhh [Re: Wouter]  
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Quote
Additionally, the F12 was never started as a showcase of "modern engineering" remember. It is supposed to be a low-cost, good looking and generally available, but yet effective and performant, entry catamaran.

Wouter


Wouter, I don't think we used a hell of a lot of engineering at all, in fact a good deal of it was seat of the pants stuff. We only went for Foam/Glass because we thought it would be easier to build than plywood.
I have done a set of drawings for a plywood version of the hard chine hull, but so far not a single person has taken a set of plans for it.
Cheers
RG

#151831 - 08/08/08 06:15 PM Re: sshhh [Re: Wouter]  

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Wouter,

Shut the [censored] up. You've put a lot of people off F16 by being a pedantic wanker, don't do the same for F12. While your contribution to the F12 has not been insignificant we can do without a three posts in a row correcting people in a rather impolite fashion. It doesn't actually matter if people make slightly incorrect assumptions or mistakes. We're all working towards the same goal.

Chris.

#151832 - 08/11/08 07:32 AM Re: sshhh [Re: RetiredGeek]  
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Quote
why I dont see the F12 minimum weight as planned to be a miracle of modern engineering. JeffS


RG, that assertion was made by JeffS, not Wouter.

Aside from that, the fact is that the F12's currently being designed and built are under or very close to the weights of similarly sized existing classes, which shouldn't be unexpected. There seems to be some confusion about platform and rigged weights.

To clarify my previous posts, my platform weight estimate is 35.4kg and rigged weight is 50.9kg (with a very crude rig weight estimate). So this isn't far from the proposed rule weight of 50kg.

From a design point of view, I could've dropped the design displacement down a fraction to 100-110kg, but to tell you the truth at this size of vessel my opinion is that it is best to design for the heavy side of the weight range, hence 120kg. Unless ofcourse you have a range of designs to offer.

#151833 - 08/11/08 05:36 PM Re: sshhh [Re: ncik]  
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Ncik I may be wrong but I was under the impression the proposed minimum rule was going to be upwards of 55kg. Earier discussions had weight being added on top of Gato's, not using his as a benchmark. If its only going to be 50kg then its back on track.
regards


Jeff Southall
Nacra 5.8 1667 Ram Raider
Nacra 18 Square
Taipan 5.7 134
Mosquito 404
Arrow 1576
#151834 - 08/12/08 05:35 AM Re: sshhh [Re: ncik]  
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News from the workshop, two halves made.
http://www.gust.ax/gallery/f12/08-08-12/

#151835 - 08/12/08 11:34 AM Re: sshhh [Re: Gato]  
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You are impressively fast Gato! Looks like foam stripping, but without the glass in place?

How did you cut the mould, by hand with a jigsaw?

Are those two Blade hulls I see beneath the F12? What is up with those?

#151836 - 08/12/08 06:50 PM Re: sshhh [Re: Rolf_Nilsen]  
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Thats a really pretty hull....nice work Nick & Gato :_)
Cheers
RG

#151837 - 08/13/08 04:18 PM Re: sshhh [Re: Rolf_Nilsen]  
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Gato Offline
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It's foam stripping, the glass on the inside. I will make up a better thing on the blog when I get the time. The two Blade hulls. lost the inspiration whit the discussions on the forum and the fact that the CHAIRMAN of the F16 class sold us some junk yard stuff at the price of super duper stuff..., but thats another story.

#151838 - 08/13/08 06:41 PM Re: sshhh [Re: RetiredGeek]  
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Thanks. Really impressed with how fast it is coming together. Still haven't come up with a name though, any ideas?

#151839 - 08/14/08 01:57 AM Re: sshhh [Re: ncik]  
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billby Offline
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very impressive Gato nice work

#151840 - 08/20/08 11:49 AM Re: sshhh [Re: billby]  
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It has no name yet, I'm behind on the blog, and it's my first boat done in foam...
http://www.gust.ax/gallery/f12/08-08-20/

#151841 - 08/20/08 12:26 PM Re: sshhh [Re: Gato]  
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A little bit less behind on the blog...
http://www.gust.ax/gallery/f12/08-08-21/

#151842 - 08/20/08 04:52 PM Re: sshhh [Re: Gato]  

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Gato,

I hope you've got some lead left over from one of your last projects. This boat looks like it will set a new bar weight wise.

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