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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Tue May 22, 2012 3:58 pm 
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Location: USA
Thanks Mal, Alistair I'll have pics of the finished product in 3-4 weeks, I hope. Sitting with my stepdad in a CCU 300 miles from home right now to see if he will recover from a stroke, so will have to wait until I can get back in the garage to complete things. Probably easier for anyone who is interested to look at pics then and make a judgement on legalities. It's my intent to stay within the spirit of the rules, but just to be sure, I'm building a 14' proto, 2' wide, 7.5 Sq M sail area so no toes are directly squished. At best a good trial, training, and destructo sled. Uses less plywood too.

And I'll be able to sail it without guilt! 8)

I'm going to name it Frank B. Heh heh.

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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Tue May 22, 2012 4:10 pm 
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Location: United Kingdom
Back to the weight issue......

I am now starting the third Morrison 2 boat and have ammended the layup based on the first boat, GBR320 Sapphire. I have found the dents only really occur in two main areas; the dancing and rear deck, the sides between shroud tubes and rear deck. The sides are particularly prone to damage from leaning on the boat with knees after a capsize or trying to hold onto the boat when launching. I haven't had any problems with dents in the undersides at all as the boat doesn't seem to turn turtle very often and therefore standing on the bottom hasn't created any dents. A 1m piece of 200g/m3 glass around the daggerboard would solve this probem anyway.

By putting 200g/m3 glass over 200g/m3 carbon on the dancing deck, dents cease to be a major problem. On the bottom outer skin I have changed to 300g/m3 biax which makes a big difference for robustness with 200g/m3 glass as well on the sides. This adds only about 2kg to the overall weight but I have managed to improve the process and saved weight elsewhere by better control of epoxy useage and should get the bare hull to about 25kg. I have used more internals than AndyP but feel happier with a central spine and bracing between spine and sides due to the different way I arrange the deck and carriage rails but these contribute only 1.5-2kg anyway. In short for longevity 25-27kg is achievable in carbon foam boats and can be reasonably robust. A production boat with resin infusion on moulds for deck and hull could probably shave at least 2kg from this figure through less epoxy or by the use of pre-preg carbon.

Carriage and seat are 11kg, seat rails in aluminium 2kg, rig is 6kg, foils 3-5kg, fittings 3-5kg.

In short a 50kg carbon foam which won't dent to buggery is achievable by an amateur but 53kg is much more realistic and only then with practice.

The relative density of wood to a 5mm foam sandwich construction is about 1.2 and then the outside needs a skin of carbon or glass making it impossible to get to the same weight unless thinner ply is used, probably 3mm or 4mm with carbon skins and imaginative use of reinforcement at the high loading points.

The UK sailing committee has voted for the 55kg limit to try and stimulate amatuer builders and the figures above I think illustrate that amateurs trying to build a competitive lightweight boat to 50kg probably will not achieve this in the short term. The class needs to decide which is the most important; long term development or early stimulous of the class. Also how many amatuer builder will actually build boats or will be it be left in the hands of the few professional and semi-professional builders to develop boats and come up with a boat design consensus that others will buy into. The latter will achieve 50kg.

Future developments;, well who knows but 12sqm of 5mm of foam used in a canoe weighs 10kg roughly so an imaginative new air cored structure could make a big difference. Carbon skins could be reduced in weight using lighter but high modulus materials which could shave another 1-2Kg or if new materials like Graphene become available. The 8kg of epoxy used could be reduced by using only a lighter weight glue or polymer if this becomes available or better production technigues but this could also shave off another 1-2kg. In summary over a 10 year period with investment perhaps a 20kg hull could be achievable.

I think the UK membership will have the opportunity to air their views on this at the next AGM.

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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Wed May 23, 2012 7:22 am 
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Paul- Hope family recovers well and your proto boat goes well,
Back to topic as Steve says, supose you have to think what the min weight is for, I always thought it was there to provide a level playing feild so that older boats/ differntly constructed boats could sail at least with no weight advantage/ disadvantage, with that in mind its a fair argument to increase the weight, however if the min weight is there for another reason, perhaps just a weight we are all saying its unfeasaable to build a sensiable boat down to then we should keep it the same. Should not get too hung up on it, but its a variable thats easy to compare between what now are very differently designed boats.

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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Wed May 23, 2012 7:49 am 
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When I consider how much the total displacement of boat and driver varies across the fleet then I find it hard to worry about 2 or 3 kg on the boat. In my case at least a weight reduction campaign would be far better targetted at my waistline than the boat's. 257 didn't become magically unbeatable against other Nethercotts when I took about 15kg out.


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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Wed May 23, 2012 3:58 pm 
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Jim, I am with you on that one.

I am firmly of the opinion that in the AC fleet for example body weight is by far the biggest factor on round the course performance in most wind strengths up to about 4 plus. With wide range of rigs available to us which is one of the greatest strengths of the class the lighter guys go just as well up wind as the more chuncky chappy. The off wind perfromance of the lighter guy is most often at an advantage as he is carrying less with little need to panic over leverage as he simply sails deeper and faster than the heavy weight. We have discussed reducing the weight of the AC over the past few years and I think that 5kg would be a good thing but I do not think it will have a huge effect on perfromance.

Sorry to hi jack an IC debate,

Martyn
AC302
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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Thu May 24, 2012 10:31 am 
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I agree with Martin. I think that a 5kg (eg) saving would be progressive but must not compromise the performance of older boats. The AC class is very strong and is represented by craft some 12 years old or so to near current day with varying skill levels amongst the helms. If a weight reduction were made I believe it to be essential to ensure that current existing older boats
can remain competitive with achievable modifications at reasonable cost.

If the weight reduction exceeded that datum we would be in danger of sending a lot of competitive craft to the graveyard. We must also remember that a lot of helms have invested heavily into revamping their craft to almost new appearance in the last few years which demonstrates a huge commitment and should be encouraged.

Sorry also for the hi-jack.

Steve AC310


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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Fri May 25, 2012 11:17 am 
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Location: United Kingdom
Fair point boys but totally irrelevant as the weight proposal is only for new rules IC's and is a proposal to actually increase minimum weight from 50 to 55kg and is to solely stimulate the build of new boats and especially those made of plywood and ensure they are competitive. It does not affect AC's at all.

The question is quite simple;

Will this stimulate the build of new boats?
Will it scupper future development to have even lighter boats as technology improves?
Does the odd 5kg make actually that much difference?

From building an AC and a IC, my observation is that the big step down from 89kg to 50-55kg does make a difference but 5-10kg around these two limits does not. A lighter boat within the rule limits is just more pleasureable to use and easier to handle on the shore and beach. Eating less pies as Jim points out is by far the biggest difference especially in less than 10knots of breeze.

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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Fri May 25, 2012 2:15 pm 
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I think originally the idea of a weight limit was used to ensure the structural integrity of the boats by removing the possibility of gaining a competitive advantage by cutting corners on the hull structure. Over time it has become more a means of equalising the boats, as may classes allow lead correctors to be applied to hulls which would otherwise be 'under built', which sort of defeats the original intent.

In our case we have a weight limit which is barely achievable using the very best materials. Yet I've not heard reports of structural failure, and if using less exotic materials, most are choosing to wear the extra weight rather than under build their hull. So it seems to me that a weight limit is not required to ensure structural integrity.

On the other hand, the current weight limit is not high enough to serve the purpose of equalising all the boats regardless of construction method.

I would suggest either raise the weight limit to serve the second purpose or (my preference) remove the weight limit altogether. There is no point in having a rule which doesn't achieve anything.

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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Sun May 27, 2012 2:03 pm 
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Uffa et al did beat the Americans with heavier boats......

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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Sun May 27, 2012 5:20 pm 
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Mal Smith wrote:
I think originally the idea of a weight limit was used to ensure the structural integrity of the boats by removing the possibility of gaining a competitive advantage by cutting corners on the hull structure. Over time it has become more a means of equalising the boats

I dunno, from a practical point of view, isn't a target the most important thing a weight limit gives you?

When you're building your boat you should be weighing bits as you go along, and aiming for that target. If you don't have a target then its rather easy to slip quite a long way. When I put a new interior into the shell of 257 I knew I couldn't get anywhere near a 50kg limit because the base shell was around 10kg or so too heavy, having been specified for an 83kg boat. This meant that I didn't really have a target because I had no doubts I could easily get lighter than the old 83kg limit, so I was aiming for "keep it light but be sure nothing breaks", and also made a few cost and time saving compromises. The result was that I probably added another 7 or 8kg more than I really needed to, even at my limited competence level because of a lack of focus at various stages of the build. So in my experience not having a target meant I ended up heavier than necessary.

We have a limit that's challenging but doable. The more minimalist you make your boat the easier it is to achieve it, to the extent that we know that a really minimalist and well built boat can get a fair way under it without resorting to real exotica, and we also know that most people get within close enough range of the limit that they don't feel the need to minimalise the boat by stripping off gear, or putting on ultra narrow planks and similar extreme measures. That seems good enough to me. There's no perfection in boat design or rule making - all one can do is achieve a reasonable compromise.


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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Mon May 28, 2012 2:42 am 
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Location: Australia
jimc wrote:
I dunno, from a practical point of view, isn't a target the most important thing a weight limit gives you?



I don't think you need a mandated weight limit for that purpose. Without a weight limit, your target weight should be the weight of the lightest boat in the fleet. Sure, if you are building a one off, you may need to set a target based on a best guess. But once a few boats have been built, the target becomes self evident.

I should point out that the Moth class provides good evidence that you don't need a weight limit to provide sound boats and good competition.

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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Mon May 28, 2012 7:26 am 
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Mal Smith wrote:
I think originally the idea of a weight limit was used to ensure the structural integrity of the boats by removing the possibility of gaining a competitive advantage by cutting corners on the hull structure. Over time it has become more a means of equalising the boats, as may classes allow lead correctors to be applied to hulls which would otherwise be 'under built', which sort of defeats the original intent.

In our case we have a weight limit which is barely achievable using the very best materials. Yet I've not heard reports of structural failure, and if using less exotic materials, most are choosing to wear the extra weight rather than under build their hull. So it seems to me that a weight limit is not required to ensure structural integrity.

On the other hand, the current weight limit is not high enough to serve the purpose of equalising all the boats regardless of construction method.

I would suggest either raise the weight limit to serve the second purpose or (my preference) remove the weight limit altogether. There is no point in having a rule which doesn't achieve anything.

I think this is where I am getting to, either increase the weight limit or get rid of it.

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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Mon May 28, 2012 11:27 am 
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The start of this topic talked about boats being strong, but possibly denting rather easily. If a 55kg limit makes it possible for builders to build a tougher skin and still be competitive on weight it will be good for the reputation of the class and the longevity of boats on the second hand market. People I meet already think that ICs are a bit crazy, you don't want them to get a reputation for being fragile and expensive to maintain as well - this would push the class even further to the fringes of dinghy sailing, and restrict it to either wealthy people who can afford a builder to keep fixing it, or sailors who also happen to be competent builders themselves.

55kg is still a very light boat by most peoples standards, why do we need to push it so close to the limits of the materials for the sake of 5kg? I think the design game should be to experiment with hull shape, rig design and foil design whilst keeping weight constant to ensure bullet proof boats, to enhance the canoes reputation further.

Materials science and experimentation is probably better suited to the likes of chemical companies and NASA etc!

In my humble opinion....

James.


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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Mon May 28, 2012 1:00 pm 
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Location: USA
Which canoes would be at the high tech/ complex end of the build matrix, and which would be at the minimalist end of things?

High tech/ complex.......................................................Minimalist

String Theory................................................................20th C Log Canoe


:?:

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 Post subject: Re: Proposal for increase in minimum weight to 55Kg?
PostPosted: Wed May 30, 2012 11:10 pm 
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Location: Australia
What a lot of bumkum.
The first DC built was Wonk. Steve Clark got very close to 50kg with a very conservative timber build.
Andy Patterson got something like 5kg under with carbon foam with his first attempt.
My Log was the 3rd build and made 52kg with plywood. My first canoe build, high freeboard and a very heavy mast.
None of these boats have been broken.
If anyone else is having difficulty making 50kg they are wasting materials, or adding un necceary complexity.

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