Designing to Steve Clark's proposed new rules

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Phil Stevenson
Posts: 202
Joined: Wed Sep 07, 2005 9:54 pm
Location: Australia

Post by Phil Stevenson » Wed Aug 16, 2006 10:07 pm

I have worked out that starting with 60 dia tubes will make everything a lot easier. Some internal local reinf will be needed. And fortunately they will fit into my present arangement on the boat.

My calcs indicate that a plank made from timber, consisting of two 60 x 20 rails on edge, 3mm ply skins top and bottom of an EPS core, and some carbon tape reinforcing, would only just make it under the 12kg limit.

I think I can make another stronger 60mm alloy one to 10kg, but if Andy is right 8kg should be achievable with foam and carbon.

I know there are a lot of seats out there but they all seem to be very thick, and I was trying to minimise windage and wave drag as well as reduce weight, and I started with 50mm because that is what the skates have. Calcs proved this wrong for the canoe geometry.

There is a big trade in weight in deciding whether the plank goes to the leeward gunwale or to the (carriage) centreline. The centreline plank is shorter and potentially lighter but the bearing loads and hence shear stresses at the windward gunwale are heaps bigger, requiring lots more strength in that area of the seat/plank. A pretty substantial carriage is needed too, where as mine only stops the plank from skewing and weighs only 600g.

I post this just for info of anyone else out there who is heading in a different direction from what is proven.
Design perfection is achieved, not when there is nothing else to add but when there is nothing else which can be taken away.
http://philscanoes.blogspot.com/

colin brown
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Joined: Tue Aug 12, 2003 12:29 pm
Location: United Kingdom

Post by colin brown » Thu Aug 17, 2006 12:31 pm

Phil, there is no difference in shear stress on the seat at the windward gunwhale. Forget your calculations, the seat is a cantilever.It can go 2 meters across the canoe or 10 meters it makes no difference. All the long planks built light fail. Its been tried before, by 'experts' but they still break. Please save yourself some time and follow the existing route, or you will spend the summer in the workshop re inventing the wheel. Remember, there is nothing new in canoeing. Ask before you try.
colin brown

Phil Stevenson
Posts: 202
Joined: Wed Sep 07, 2005 9:54 pm
Location: Australia

Post by Phil Stevenson » Thu Aug 17, 2006 10:31 pm

But this is a development boat. If I was made to copy everything I probobly would not be sailing a Nethercott but settle for a Laser.

If our ancestors did not experiment we would all be sailing clinker dinghies with wooden spars and flax sails.

OK the BM and shear do not change but the bearing loads do and that is what I believe damaged the tubes in my case.
Design perfection is achieved, not when there is nothing else to add but when there is nothing else which can be taken away.
http://philscanoes.blogspot.com/

Steve Clark
Posts: 165
Joined: Fri Aug 01, 2003 2:26 pm

Post by Steve Clark » Fri Aug 18, 2006 1:51 am

Image
A simple alternative I have been thinking about.
100mm deep central beam.
Triangular cross-section.
Lots of simple gussets.
Cradles at each sheer.
3mm skins with Kevlar on inside.
Should work and be very light.
Problem for me is that I have a tool that works, so motivation to try something different is pretty limited.
My latest seats have been finishing at about 7.5 kg with hiking straps. I think there is another 1/2-3/4 kg to get before I have to retool the part to reduce skin area.
SHC
Beatings will continue until morale improves

Mal Smith
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Joined: Mon Dec 20, 2004 1:42 am
Location: Australia

Post by Mal Smith » Fri Aug 18, 2006 2:48 am

I'm currently building a new seat which is made from 3mm plywood. It is a triangular section beam as Steve suggests but I am including a 40mm x 20mm cedar stringer at the bottom of the beam (in the vee) and a 20mm x 20mm mm stringer in each of the top corners. It has three webs along the length of the seat and lots of small webs accross the seat. I and covering the outside with Dynel for durability. I was going to use glass, but then the glass would be taking all of the load and the wood structure would only be acting as a core. Dynel has similar mechanical properties to wood and will strain enough to allow the wood structure to take the load. In theory then, the dynel and wood will fail at the same time, whereas if I used glass or some other higher modulus material, the glass would fail first, followed quickly by the wood structure, ie the glass has to be designed to take almost all of the stress. In effect the Dynel/wood structure may be more efficient weight wise, but it will probably flex more. I hope I am right! My projected weight for the seat is around 7kg. There are some design sketches and early construction photos at http://photos.yahoo.com/mal_smith_au

Mal.
AUS019

Paul Scott
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Location: USA

Post by Paul Scott » Fri Aug 18, 2006 4:39 am

Mal-

Very clean, Very Tech, Very Nice.

Paul
"Exuberance is better than good taste" -Flaubert

Phil Stevenson
Posts: 202
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Location: Australia

Post by Phil Stevenson » Fri Aug 18, 2006 7:56 am

Keep those good ideas coming, If the pundits are right I will need a Mk 3 soon.
Design perfection is achieved, not when there is nothing else to add but when there is nothing else which can be taken away.
http://philscanoes.blogspot.com/

seth
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Joined: Tue Sep 09, 2003 12:01 pm
Location: Australia

Post by seth » Mon Aug 28, 2006 10:04 pm

Being one of the few canoe sailors to sail a development boat I guess I should express my opinion (better late than never).

I Sailed Phil's new boat at the Brass Monkey on the 12 August (the water was a bit chilly). Being a mothie, Phil has set his boat up a bit like a moth - relatively high aft deck, the top of the seat is only 3" off the deck (way too low for me) and he used some old moth foils to get going.

I've got to say that the boat looked superb, if a little odd. For a two or three month, mostly part time project things worked quite well, even if the plank didn't stand up to the job.

Sailing the boat was tricky in the conditions (very little wind with occasional small gusts). I guess it felt very moth like - there was a moth like pitching sensation due to the relatively low volume in the ends, but it also felt very responsive to the helm. The most challenging thing for me was that sailing down wind (wind is a fairly optimistic description) I couldn't relax. The boat was twitchy and tipped over very easily. I found myself constantly over reacting to the boat healing. I would get used to this in time, but it's a whole new ball game in balance.

In a constant breeze I had no trouble sailing faster than Phil on my boat...this sounds ominous. So I think there is potential in the concept.

I think the size of the centreboard contributed to some of my problems - I think it was about a 5" chord and less than 1m deep. The mainsail was not yet fully sorted with some darts up the front to adjust luff round and a big hooky head. Phil, if you can sort out that main and the foils, I think it will be a very sweet boat.

Seth.
AUS14

Phil Stevenson
Posts: 202
Joined: Wed Sep 07, 2005 9:54 pm
Location: Australia

Post by Phil Stevenson » Mon Aug 28, 2006 10:43 pm

Thanks for the comments Seth, Its good for everyone to read a second opinion.

Despite what Seth says about Moth like I think his trepidation was more due to lack of familiarity with the boat. I capsised his nethercott too when I first sailed it. I do have a moth like mainsheet system because I like to be able to work the sheet for balance rather than move my lazy old body (56), just like sailing a moth, and maybe that was uncomfortable for Seth.

Please believe me that this boat is maybe 5 times more stable than a moth, and is infinitely easier to sail downwind in light weather, and unlike a moth it does not dig the nose in when hard pressed or in gybes. I sailed 4 races that weekend without a swim.

I posted a photo in the Yahoo library (ref in another earlier posting) with a moth hull inside the canoe shell and almost enough space left for a couple of others. This is no moth, it is a big stable boat. But it slips along at least as easilly as a good moth.
Design perfection is achieved, not when there is nothing else to add but when there is nothing else which can be taken away.
http://philscanoes.blogspot.com/

seth
Posts: 4
Joined: Tue Sep 09, 2003 12:01 pm
Location: Australia

Post by seth » Tue Aug 29, 2006 3:41 am

Phil,

You are right. I was very un-familiar with you boat set up and suprise is probably the best word to describe my discomfort. It was definitely more stable than any of the 3 very narrow moths that I have sailed. I don't want to put the dampeners on the development. From the short sail in fairly dull conditions I feel that this boat has great potential.

I really look forward to a match up and a sail in 10 to 15 knots.

Seth.
AUS14

Phil Stevenson
Posts: 202
Joined: Wed Sep 07, 2005 9:54 pm
Location: Australia

Post by Phil Stevenson » Fri Sep 01, 2006 1:36 am

For those who are interested in how I built my DC have a look at the full story on Aust IC web site: http://www.internationalcanoe.yachting. ... F13920%2F0
Design perfection is achieved, not when there is nothing else to add but when there is nothing else which can be taken away.
http://philscanoes.blogspot.com/

Phil Stevenson
Posts: 202
Joined: Wed Sep 07, 2005 9:54 pm
Location: Australia

Post by Phil Stevenson » Mon Sep 04, 2006 1:28 am

I sailed my boat again over the weekend, this time in a breeze gradually increasing to maybe 12 kts. No racing just testing. It was one of those pre-emptive beautiful spring days which pop up this time of year at 27deg C. (Next weekend is promised to be cold and wet to prove it was only a jesture.)

I sailed with a top line foiling moth sailed by a new owner. He was able to foil upwind and reaching but only occasionally downwind. The canoe was consistantly faster and higher upwind. The moth was considerably faster beam reaching, and downwind I sailed away except when he was able to foil for short bursts.

Altogether the performance is very rewarding. I got to the end of the seat in the stronger patches and the boat feels very alive. In the stronger breeze I was able to sail downwind with the apparent brought right forward so there seems to be a good chance these boats will be able to sail angles to advantage in the right conditions, as Steve had planned.

Everything stayed together including he beefed up seat.

Things which did not work for me were the way the seat slides through and associated complications. The slightly thicker seat has closed the gap between the seat and rails and now the mainsheet jambs in there (I know Steve that you told me it would happen). So there were a few swims tacking and gybing with the seat and mainsheet jambed.

As I am the middle of a moth project at present I will try to smooth things up a bit and get the seat working better, but later in the year I will have to build a new seat and carriage, disposing of the rails. I will also talk to the Skate guys when the club starts racing and see if they have any ideas or techniques to make their system work better.
Design perfection is achieved, not when there is nothing else to add but when there is nothing else which can be taken away.
http://philscanoes.blogspot.com/

Karl Wittnebel
Posts: 0
Joined: Tue Dec 09, 2003 9:30 pm
Location: USA

Post by Karl Wittnebel » Thu Sep 07, 2006 4:09 am

Phil -

Your writeup on building the DC is excellent. Thanks for taking the time to explain how you built your boat - it is a service to those of us interested in building similar craft.

Rgds,
Karl
Karl Wittnebel
NC USA 193 (Lust Puppet)

Phil Stevenson
Posts: 202
Joined: Wed Sep 07, 2005 9:54 pm
Location: Australia

Post by Phil Stevenson » Mon Sep 18, 2006 12:35 am

DC AUS 21 "21st Century Hollow Log" update

I sailed the course with the foil moths this saturday. Not top line boats but three competant sailors doing pretty well. I was considerably faster in 10 kts up wind and downwind but as the wind increased, they went a lot faster downwind and balanced out my windward advantage. (The top sailors would be faster in lighter winds, that being harder to master) I am not sure I would be as fast upwind as the top foil boats but must be getting in the ball park.

I have flattened the top of the sail a little and think it went better upwind than before. Certainly faster than anything else I encountered on the day, even though I still spent very little time on the end of the seat.

The sail still needs to be finished off. It has various temporary tucks in the luff pocket as we adjust the luff curve to suit the mast. It is also still a little over size so the pocket will need to be moved back too.

I am still running deep and gybing as little as possible. I think the boat will benefit from reaching off when I gain more confidence in it, especially gybing. This is based on a couple of line up with spinnacker boats.

Next outing will be in two weeks at Albury with other canoes. After that a new seat and carriage and finishing the sail. But I will be mostly moth sailing up to new year now.

Phil S
Design perfection is achieved, not when there is nothing else to add but when there is nothing else which can be taken away.
http://philscanoes.blogspot.com/

colin brown
Posts: 85
Joined: Tue Aug 12, 2003 12:29 pm
Location: United Kingdom

Post by colin brown » Wed Sep 20, 2006 11:38 am

One point I do need to draw to the attention of all sailors considering new rigs concerns SLEEVE LUFF sails. Just a timely reminder that we have had these in the past and rules were drafted at the time for there control, they are as written today.All current rules, IC / AC/ DC require that these be 'easily removed while floating freely' . The ICF committee have advise that in the case of any doubt that measures conduct a test under normal sailing conditions. Please give this safety acpect of our rules your serious consideration.
colin brown

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