Proposal for increase in minimum weight to 55Kg?

[Andy P]

I must begin by saying that I reckon that with the current build it will be absolutely impossible for me to get anywhere near the 50kgs.
First I haven’t got a vacuum pump at present
Ian

But you should only be using an stone axe to hollow out a tree trunk! ( not any of those new-fangled metal tools, or glue ) then there's no way to get to even 100kg!

Dragonfly's internal structure... err.... there isn't any really.
and 43litre buoyancy bags - light, don't soak up water ( like blue foam does after a while )
http://www.mediafire.com/i/?ydn3jyvmlmayy9c
http://www.mediafire.com/i/?02gzr22p5450tlt
To resist torsion, the carbon in the hull on both sides of the foam is at ±45°

Perhaps an extra glass or carbon layer on the outside would help prevent dents, this would add less than 2 kg.

I think the problem is that historically, the weight has been high, and so it's a bit of a shock having to be very weight conscious and seeing what you can leave out!

[JamesClose]

What about using glass fibre cloth, epoxy and foam construction? Would this result in a boat more resistant to dents? Can you use one layer of woven cloth on each side of the foam, or does it have to be a laminate of at least 2 layers on each side?

Glass would seem to be a lot cheaper than carbon, but not sure how much of it is required - so not sure how much additional weight there would be. Would a 55kg glass canoe be a possibility?

Could you build a canoe like a windsurf board? Sort of like a really thick foam sandwich with a sculpted top lip, raising up to form a bow. This would mean you don't need the additional material for a deck and save a lot of weight. With a large (2 inch?) solid foam core would you have problems with the air in the foam expanding if the temperature increases once it has been sealed in with the glass cloth? As I understand it surf boards use a polystyrene foam core wrapped with a structural foam sheet, which is then sheathed with glass.

Sorry for lots of questions, but this seems to be a good topic to raise them. I enjoy doodling IC designs and would like to build one day, but wonder how many of them are doomed construction ideas! Would be grateful for any advice. My main aim would be to try to keep costs affordable and build a robust, low maintenance hull, but to the new measurements.

Thanks
James

[Andy P]

My boats have 200g/m² carbon inside, 200g/m² carbon + 86g/m² glass outside. ( and heavier or two layers of carbon on the crewdeck )
To equal the stiffness of the carbon would need at least twice as much glass, so maybe adding 7-8kg.


To laminate over a solid foam core there is a weight / dent / stiffness problem. A solid core would need to be of low density foam, but still would be quite heavy for a boat shape. The normal skins get their stiffness from being a sandwich - both skins 5mm apart take load. To get equal stiffness and strength, the single skins would have to be maybe 4 times the weight, the foam core is very soft, and delamination would be a problem. A solution would be to add a high density foam skin over the light solid core to add hardness under the skin.

Moths have tried this type of construction in the past, but the end result is heavy, dents even more easily, and breaks up with delamination or just breaks in half.
Sailboards do this hard foam wrap, but they are into mass production which makes it easier, and on thinner things.( boards not boats )

[Paul Scott]

Another approach by board folk is to make a hollow extruded polystyrene board, using 2" xps (sic). That way you can make a torsion box (or boxes) that are mainly air ( like the IC with the blue foam above ). Xps is good in compression, but little else. More surfboards are using xps inside for the spine and lateral ladder type support. Then epoxy & cloth around wood, which is itself built around the foam. Sometimes balsa. Same sort of thing for some A class cats, although glass reinforced wood for the main bulkheads and skins. Considered kind of old school, methinks, so same problem as new IC's, weight and stiffness wise.

The hollow board with both inner support and skin of xps solution does leave you the delights of shaping the stuff, although once you get it Shaped right, you have to scuff it up with 200 grit or so so laminates will stay stuck. Laminate a piece of thin ply on the dance floor. But there is still the guessing game on how much stuff is enough to deal with the torque between seat and rig. Swaylocks forums have many posts concerning boards on all these methods.

I support the 50kg rule, and I can't use epoxy! Perhaps throw away hulls are the answer, if they are cheap and quick to put together. Recycle the hardware from hull to hull.. It would give regattas some added spice. But you would have flotation if you used xps.....

Paul

[Alistair]

I must begin by saying that I reckon that with the current build it will be absolutely impossible for me to get anywhere near the 50kgs.
First I haven’t got a vacuum pump at present
Ian

But you should only be using an stone axe to hollow out a tree trunk! ( not any of those new-fangled metal tools, or glue ) then there's no way to get to even 100kg!

Dragonfly's internal structure... err.... there isn't any really.
and 43litre buoyancy bags - light, don't soak up water ( like blue foam does after a while )
http://www.mediafire.com/i/?ydn3jyvmlmayy9c
http://www.mediafire.com/i/?02gzr22p5450tlt
To resist torsion, the carbon in the hull on both sides of the foam is at ±45°

Perhaps an extra glass or carbon layer on the outside would help prevent dents, this would add less than 2 kg.

I think the problem is that historically, the weight has been high, and so it's a bit of a shock having to be very weight conscious and seeing what you can leave out!

Having sailed Dragonfly there are no problems with hull stiffness, including where i jump around (actually surprisingly stiff), and I would be around an average canoe sailor weight at 12.5 stone (well some times, depends on cake and beer consumption), however the hull does dent fairly easily. I don't think there is a question that boats can be built down to the current 50kg, its just how people feel about trying to achieve this. Andy's right that we are all used to over building our boats, and perhaps some people are using older techniques to build there boats, but if thats what the class wants to do then it would be fairer to have a higher weight, I suppose it depends on what we are all trying to do, always difficult to decipher in the canoe class as we all have very different ideas about why we are sailing in the class. If increasing the weight encourages people to build boats then its a good idea, but perhaps the sort of people who would build a canoe are not too influenced by this and would build (or not) what ever the weight or rules? To me its designing the boat then sailing it that interests me, so as long as the rules are fairly open then I'm in, but there's no point in being the only one out there so I am interested in encouraging others to come out and give it a go.

[SteveC]

AndyP is clearly correct and I can see in retrospect we don't need many frames in the boats at all. When you start making the internals frames do appeal as it does make it a bit easier to put the decks on and make absolutely sure everything is bonded. With thought, proper bonding at the joints and moulding some parts however thay can be completely removed. The canoe is essentially as closed box consruction and the carbon is immensily strong but has to be laid with the stress in line with the fibres. A single layer of carbon can support tensile stresses of several tonnes on a just a 4"wide strip. With a 45/45 layup the torsional strengh in a box construction should be more than adequate to support the loads we use and in fact I think glass may also be OK with some additional unidirectional carbon laid at key points. Calculation however would be tricky and can really only be done by experiment.

I have a spreadsheet which I developed when building Sapphire which seems pretty accurate working out costs and weights. My analysis shows a reasonable correlation between theory and practice. The weight comes out at 24Kg for a bare hull using carbon single layer on hull and decks. I have just run a similar one changing the hull and deck to 2 layers of s-glass on the outside surfaces for robustness, one on the inside but keeping the internals as carbon. Using this analysis the weight shoots up to 34kg. Difference in cost, by the way is minimal as more epoxy is needed.

A composite of carbon/foam and ply on the walking decks is of course is another option as Rob does with his Nethercott's.

[JamesClose]

Thanks for taking the time to answer my construction questions... probably best to stick with the tried and tested methods!

What attracted me to ICs was seeing a picture of Wonk, then a bit later String Theory, and thought they looked like the ultimate singlehanded dinghy. So I brought a Nethercott IC to learn on and have been hooked ever since. Don't think I will ever sail anything other than a canoe again! The only negative with the nethercott was sailing downwind, I don't personally like soaking dead downwind, so I have now got an AC which solves that problem - and I am quite happy getting to grips with it at the moment. However if a new IC design came along that would sail fast on hot angles downwind (like an A Class) then I would be tempted back to ICs, but I like the fact that the nethercott AC seems pretty robust, and lets me get away with capsizing (learning) without fear of doing too much damage.

50kg is probably more exciting from a builders perspective, but is hull weight the ultimate factor in regards to performance/enjoyment of an IC?

55kg might appeal more to non builders, if it means someone could develop one of the new designs into a standardised, more affordable, strong, off the shelf package. Also, if the new boats are more robust they will have a long life on the second hand market which would help attract more people into the class who couldn't afford to buy new.

A complete, new, bespoke boat is a big investment once you factor in a new rig, sails, fittings etc and personally, I think it would be good if the boats were slightly overbuilt, made to last and cope with a few knocks, but maybe that is not in the spirit of a development class?

James

[Paul Scott]

As long as I've been raving about surf tech:

http://woodsurfboardsupply.com

Something to look at..

[Steve Clark]

Just to add some actual numbers to the mix.
One of the contentions I made when we started down this road was that one could build a competitive boat out of plywood. USA 250 ( 4th) and USA 250 ( 8th) proved that they were competitive at this years Worlds, so I guess we could state that the point has been made.

In order to hit the 50 KG minimum weight, the fitted hull, with seat carriage in place has to weigh within a kilo or two of 30 KG.
The 4 plywood boats I have built haven't been close. The fitted hulls with essential fixed fasteners have been more like 40 kg, and these haven't been built using stone axes. I may not be as excellent as Andy, but I'm not a complete wanker.

I have played around with the specs quite a bit trying to get this done. Wonk was built of 3mm ply with 200 g/m^2 carbon on either side in the high load areas and just on the outside elsewhere. She had bulkheads every 500mm. Boat has proven strong enough to hurt many people, but is not really very stiff, and you can hear the bottom oilcan some of the time.

GER 78 was built out of 3mm ply with 6mm 55k/m^3 foam and 78g/m^2 Kevlar on the inside. The deck was 3mm with 78g/m^2 Kevlar on the back ply over standard deck beams at 300mm centers. Outside the hull was covered with 150 g/m^2 glass. This boat has had some trouble around the perimeter of tha dance floor and around the mast step.

The last two boats were variations on the above, but all of the flat stuff was built out of 200g/m^2 carbon on either side of 6mm 55k/m^3 foam. So only the curvy bits were built out of plywood, all was carbon and foam. I though this could be a good halfway measure. USA 250 had pink foam bulkheads a la Phil S to try to make best use of the buoyancy foam, the inside was covered with carbon and the outside carboned below the chine. USA 249 had 25mm pink foam glued to the inside of the hull below the chine with Gorilla glue ( The stuff foams like a bastard) and then covered with 78 g/m^2 Kevlar. There is carbon on the outside below the chine. The internal structure is 3 carbon foam bulkheads.

These boats are very stiff, but you will put a knee through the topsides if you fell on them.
I have tried to be very careful with the seat rails and the chain plates and I discovered that my center line mast compression structures had been slightly under cooked in the past. ( See embarrassing photos of Ger 78) The seat carriages have all been in the 3 kg with the hardware bolted on. and the fit out and finish isn't excessive, so I really think that these things are within a few kg of what can reasonably be accomplished in plywood. There might be 5 kg of improvement, but I don't think there is 10. If one wants to recycle a 9 or 10 kg sliding seat, and parts of a 10 kg seat carriage, you will never make it.

I am going around the track again this fall as I try to finish an exportable design and build package. While I am absolutely confident that 50 kg is a good number for composite boats, I'm also pretty sure it will be a complete bear to get there in plywood.
SHC

[Phil Stevenson]

Unlike Steve I have only built one canoe.
The Hollow Log weighed in at 53.2kg at McCrae, including a heavy 65mm dia unstayed mast and a substantial all timber seat. It had higher freeboard and hence more material than any other canoe there. The hull is 3mm ply with 200gsm carbon inside only to within 1m approx of each end. It has only 3 ply bulkheads plus foam bulkheads at about 400mm c-c. There is no longitudinal frame or spine.
I never damaged any part of the hull while sailing. I capsized it many times while learning how to sail it and climbed all over the hull in the process. Christian collided with me in Adelaide once but damage was minimal and we both finished the race. It is a solid boat, proven durable under many people.
I am sure that if I build another one I could save a lot more than 5kg.
I still read these forums so building another one is never completely off my agenda.

[H Virtue]

Firstly I am a self taut amateur builder, I have built some nice boats never had a boat at minimum weight (but very close)

I haven't hit the 50kg just yet but for good reasons.
1. I reused my old (very heavy) hiking plank from my Nethercott.
2. I reused my old very heavy boom from my nethercott.
3. I stuffed up with one layer on a shell. (thats what you get for working 8 hours a day at work and then another 10 on the boat for 4 weeks fatigue nothing else caused it)

I haven't weighed my latest boat just yet I know its not down to minimum until I build a plank and carriage for the boat rather than the hand me down from my Nethercott. Once I build all the new parts for the new rules boat I believe I will hit the 50kg maybe even a little under. I didn't compromise on structure at any stage but I did ask questions from Steve Clark, John Kells, Chris Maas etc about how much carbon they used here and there they where all more than willing to share there lay-ups tech info.... in some case's their entire design.

The two hull I have built are strong and reliable, AUS30 finished up on a rock break water in very heavy season and written off, considering the belting the hull subject to the amount of damage to the hull was next to nothing only a few areas was the hull full pierced through, the majority only the outer skin was dented without the fibre showing fracturing by the eye. I load the hull up as I did the nethercott without an issue using the same rig I used in the 2008 worlds I haven't had to re-cut the sail or do any major re-tuning.

I built my boats over a male mold full carbon. I did save weight where possible and was carefull to not put any more material than I though I needed. If I build another boat I will build the boat with less internal and I have worked out a way of saving about 350g with a better designed strong back under the dance floor.

Going to 55kg isn't necessary it is possible to build carbon or ply boats to the weight without pro-builder skills. However if people can have a guarantee a mass inful of new boat if we go to 55kg then as a class maybe we should consider it. But with the option of 5-10kg of correctors allow so those who want can build down to 50kg and in time I bet we vote to remove the the led and go to 50kg min weight.

I'm happy to stay at 50kg going to 55kg wont make it cheaper for me to build a hull I would haev to by lead so therefore it will cost me more....

FWIW I went for a very strong dance floor 2 layers of carbon in the working area so I could easily if needed take a heap weight out, but I don't need to make this compromise I will keep building the dance floor this way.

Also Phil Stevo's boat is very light and could easily be built lighter, the materials the boat are made of in no way effect its performance in my view its a fast bot that slipps through the water nicely, its other things on AUS21 that development for big speed improvements.... all well document by Phil in his blog....

H.
(The former)

[Del Olsen]

With all due respect, I heartly disagree with increasing the minimum weight for the following reasons;
1) A minimum weight canoe is a GOAL not a guarantee. You do the best you can and you see how you did when you put her on the scales. It's not supposed to be easy. You're not guaranteed 1st place in the regatta either.
2) Posterity, No one uses the term anymore but do we know what advances in materials and adhesives will be commonplace in 20 or 30 years?. I know that 30+ years ago "carbon fiber" and 'epoxy' were the stuff of myth, available to the military and space programs and frightfully expensive. Today there as easy to get as a computer virus and come from the same place. We accepted a rule for us in the here and now and for the future, we shouldn't compromise the future for our current convienence.
3) IC were on the leading edge of boatbuilding for decades, we're back at the forefront now, let's stay there.
Just look at the hollow spiral wraped wood veneer spars from 100 yrs ago, we've had carbon since the early '80 and were the first class to develop and adopt them, who wants to go back to Alum ?

[Paul Scott]

Keep it at 50kg. It's a goal that makes for a nice mix in the class.

Since I'm on the minimalist end of things, I'd like to see a leeboard made legal, since it makes things simpler, lighter and cheaper. But it would require a support beyond the sheer, or a hole on top of the deck to keep it easy to attach. If anyone is worried about a canting leeboard, what's to keep anyone from canting a centerboard? The size of the deck hole for the DB/CB is not described at all. I think the rules specify just two foils, so it's not an A class scenario, with 4. Anyway, my proto is going to have one before I move on to the next iteration. That actually sails.

My 2 cents.

[Mal Smith]

Although the rules talk about 'THE centreboard' and hull through holes are limited to 'one centreboard trunk and one rudder trunk', I don't think you are actually limited to one centreboard or rudder, as there are 'no restrictions on the design or materials' of the rudder or centreboard. The rules don't expressly prohibit more than one centreboard or rudder. With this in mind, I have a question: If you did for some strange reason have two centreboards (leeboards, say), could you use the allowed rudder trunk through hole for the second leeboard (and have a stern hung rudder)?

[Alistair]

Hi
There are a few rules that are open to interpretation, in fact it would be diffcult to write a set of rules that are bullet proof, but I would say a hole through the boat that had a c/b in it is a c/b hole , so only one hole allowed, but perhaps a double c/b or two going through the same opening would be OK, even perhaps two rudders of the back, but then it does say "the rudder" and "the center board" surgesting single structures . However if some one wanted to try lee boards then why not let them, I think that you may be able to ask for a dispensation? Generally what Paul is looking at doing is within the spirit of the canoe class so why not? Not sure how it makes thing easier, but I don't know the detail of what Paul has in mind. I have visions of trying to raise and lower them whilist tacking and throwing the seat across.........