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    • UnderDawg

      A Few Simple Rules   05/22/2017

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stinky

DC Designs

3,540 posts in this topic

Hi Chris,

 

indeed the Z-Boats are a class which is active in Germany and Austria. We share an event each year. It is a very small class of traditional wooden boats. 20m². Long and narrow and very low freeboard. So some of them go submarining from time to time. They are very fast and there are some beautiful boats among them.

Some more (german) info: http://www.zboot.net/

 

Arne

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Is there a North American IC class association to join?

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Is there a North American IC class association to join?

You're already in it. We're a 100% libertarian organization. No fees, no paperwork, no services.

 

DRC

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I may even volunteer to help do some of the nothing then. Gotta give back a little.

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The one change that is not a clarification requires no tool removal of the mainsail while the boat is upright. Used to be while afloat. My boat is now non-compliant which makes me unhappy. Rerigging to become compliant is not trivial as I have 3 watertight sections in my mast. I had no notice that rules were a-changing.

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Is there a traditional US east coast circuit calendar of IC events?

 

Where does event planning chatter happen?

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Here, mostly.

 

East Coasties, what do you got? My early summer is looking busy but late summer for sure. I'd love to do one or two down here if we have players.

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What diameter rod rigging are people using? Will 2.5mm diameter be man enough?

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Hi Chris

I am sure I am on 3.5mm 7 x 1 dyform, but this is a bit over kill, I think Phil Robin uses 2.5 dyform, not sure about rod.... yet to experiment but like the idea of 3mm carbon rod and 3mm ti rod but don't really need any improvement on what I have.

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I have used 2.5 and 3mm rod. Swedging the ends is the tricky bit. As a rule of thumb, you can drop one size when converting from 1x19 cable. The metal area is almost the same. You get the advantage of less construction related stretch, but it is nnot as profound as if you maintain the diameter when you substitute the rod for cable. Dyeform is not as dense as rod and has less construction creep than 1x19, so I would not suggest the same size reduction formula. I maintain the same diameter and realize less stretch.

SHC

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Well I will go with the 2.5mm rod, I will leave the swedging to the boys at the local riggers. Apparently there is a special technique that they are a bit hush about, but they have a great reputation. Harken Ha300 1" wire blocks should be strong enough to run the high load end of the shroud adjustment. Need to get the rig up to measure the fore triangle so I can pass all the measurements on to Frank Rowsell to make the sails. His lead time will more than likely dictate when I launch.

 

Chris H

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I've recently got Aus 32 back on the water and I'm looking to get a new set of sails. (Need to train for the worlds you see...)

 

Before I do - I want a Jib boom, and may need to make sure the Jib design factors this in.

 

I've been thinking about Black Betty's Jib boom and although I like it, I think you need to be better than me at boat building to integrate it into the hull. I am thinking of something that can be retrofitted to any hull - so I can use something similar on my Nethercott as well, with no hull modification. I don't like the droopy one and the UK style seems to need more things hanging of the mast and lines to control it.

 

I think my design might work, if factored into the sail design, and it should be passive rather than needing control lines - as inspired by Black Betty

 

UK%20Jib%20Boom.jpg

 

Hanging%20Jib%20Boom.jpg

 

Raven%20Jib%20Boom.jpg

 

Black%20Betty%20Jib%20Boom.jpg

 

My%20Idea%20Jib%20Boom.jpg

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I don't think that will work as the forces will deflect the forestay and mess up your jib luff

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Are the upward forces on the jib boom that significant?

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Do what we do and just have the jib made with the battens angled perpendicular to the forestay. It's the lightest, cleanest and most robust solution. Its not tuneable, but tuning isn't everything.

 

DRC

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That's very clever Stefan.

 

I think it's worth a try. It would be fairly simple to make. Important details include getting it as low as possible and allowing it to swivel freely. I'd figure out a way to test it with your old jib first.

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My%20Idea%20Jib%20Boom.jpg

 

I've been mulling over something like this, but the conclusion I keep coming to is that anything that is attached to the forestay will distort the jib quite as badly as a wishbone boom, in which case you may as well just do that - which has been tried and abandoned a few times.. I've sort of had in my mind a slotted carbon tube in a fordeck socket that's concentric to the forestay, and free to rotate so that the jib comes out from the slot and shape unaffected, and leech tension is adjusted from a forward extension of the boom, but with a line just going a few inches to the top of the tube and back down and under the foredeck. I was also thinking a wishbone boom so that the jib can be genuinely closed to the deck. The engineering feels very challenging though.

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Sezed, I have been mulling over this for some time. I have tried using the "uk" style jib boom, and the dangly stick, the dangly stick worked best but required too much adjustment. I have alternated in championships between the jib boom and none at all. I am not convinced of the effectiveness. For certain there is some benefit, and perhaps more if you had a larger jib, I am on about 2.15m2, for ease of use however its nicer without. I also do not wish to add structure to the front of my boat. Have not had much time to experiment recently but I think there might be another solution, perhaps it's just as Dave says, jib batterns.... simple is usually best

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I think your idea was tried by the current owner of "Monkey" Not sure that he has kept it on the boat much longer. You also lack tuning ability, whilst not essential when underway you do need to get the jib leach tension correct for the wind strength. I suspect that the future will be no jib boom with a set up such as what Dave Clark describes.

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Its worth noting that you can probably tune the angled battens by tensioning a control line or bungee in the batten pocket against the central one.

 

DRC

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Has anyone considered a full swing rig as seen in RC / Marbleheads?

 

I know their design case utilises small loads but their refinement and super clean aero resolution cannot be but admired.

 

The complexity of it would be offset by the ability to maintain the slot effect of jib to main in a permanent manner, even when sailing broad angles.

The loads and jib luff deflection are constantly managed and High Modulus carbon may resolve the weight vs. spreader need. Might even allow a small chord wing mast to over rotate on the mast axis.

And, ultimately for a single hander just one control line (mainsheet) needs to be routed to the helm, saving significant amount of fittings and aggro.

Structurally, the hull becomes a simpler deal with loads concentrated between mast stump and rudder in the primary instance which encases the support for CB and sliding seat attachments. The lack of forestay and chain plates being a significant payoff (if the rig stability and stiffness can be resolved on an unstayed solution).

 

The radio guys tune their rigs prior to race and then concentrate on other issues in the actual race - which would have distinct advantages in this class.......

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Has anyone considered a full swing rig as seen in RC / Marbleheads?

 

Been tried a good many occasions over the decades. Doesn't seem to work well at all. Might well be something back in the thread somewhere. ISTR SHC has practical experience.

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Though it wasn't widely covered by the main stream media I won the '11 IC worlds with a swing rig. Actually it was more of a swing jib - the jib swing was de-coupled from the main boom. It worked reasonably well. I figure it sped me up downwind a bit and slowed me upwind. I put a honkin' big window in the jib but when that got a little salt spray on it it was hard to see the waves downwind - which, surprise, is really important.

post-16686-0-90712100-1492271143_thumb.jpeg

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Though it wasn't widely covered by the main stream media I won the '11 IC worlds with a swing rig. Actually it was more of a swing jib - the jib swing was de-coupled from the main boom. It worked reasonably well. I figure it sped me up downwind a bit and slowed me upwind. I put a honkin' big window in the jib but when that got a little salt spray on it it was hard to see the waves downwind - which, surprise, is really important.

I remember. As a perpetually light guy I don't often feel powerless to stop people off the wind in 6-10 knots. I even felt fast with my new ultra pointy boat. It was all useless against Angel of Attack, especially with the swing jib engaged. Extra points for it looking like a carbon crossbow.

 

DRC

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Has anyone considered a full swing rig as seen in RC / Marbleheads?

 

I know their design case utilises small loads but their refinement and super clean aero resolution cannot be but admired.

 

The complexity of it would be offset by the ability to maintain the slot effect of jib to main in a permanent manner, even when sailing broad angles.

The loads and jib luff deflection are constantly managed and High Modulus carbon may resolve the weight vs. spreader need. Might even allow a small chord wing mast to over rotate on the mast axis.

And, ultimately for a single hander just one control line (mainsheet) needs to be routed to the helm, saving significant amount of fittings and aggro.

Structurally, the hull becomes a simpler deal with loads concentrated between mast stump and rudder in the primary instance which encases the support for CB and sliding seat attachments. The lack of forestay and chain plates being a significant payoff (if the rig stability and stiffness can be resolved on an unstayed solution).

 

The radio guys tune their rigs prior to race and then concentrate on other issues in the actual race - which would have distinct advantages in this class.......

One of the problems with scaling up the radio controlled swing rigs is that as you sheet out in a gust the jib backs.... not great. Also a huge load goes through the pivoting rig. Almost everything has been tired in canoes..... the standard set up is generally hard to beat.

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I seem to recall the winner of the last worlds had no jib-boomy-thing at all.

 

Don't recall much from the second-place guy either

 

I confess very little knowledge of how to make an IC go downwind in light air, but in breeze it seemed leech tension on that postage stamp of a jib was fairly close to irrelevant.

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I did use a wishbone boom on my jib at the last worlds. It doesn't do much on the windy reaches but it does help on the runs.

post-16686-0-48640600-1492451547.png

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Any reason not to plug my masthead with a bit of bog and kitty hairs and tighten up the gaps around the sheave box? There aren't any significant holes in the rest of the spar so maybe the tube won't fill very fast anyway?

 

esl0YCBh.jpg

 

 

 

edit- i suppose I'll want the end open to fish a new halyard some day, so maybe just glue a cork in?

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Any reason not to plug my masthead with a bit of bog and kitty hairs and tighten up the gaps around the sheave box? There aren't any significant holes in the rest of the spar so maybe the tube won't fill very fast anyway?

 

esl0YCBh.jpg

 

 

 

edit- i suppose I'll want the end open to fish a new halyard some day, so maybe just glue a cork in?

If you can find the right diameter cap with interior grooves, the absolute professional thing to do is glue in a cap, but thick bog will do the trick fine.

 

DRC

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I did use a wishbone boom on my jib at the last worlds. It doesn't do much on the windy reaches but it does help on the runs.

 

Chris got any larger/better pics of this set up?

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I did use a wishbone boom on my jib at the last worlds. It doesn't do much on the windy reaches but it does help on the runs.

 

Chris got any larger/better pics of this set up?

 

 

Sorry B. I couldn't find any.

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Anyone ever used a seat profile like the orange one in this image?

possible pros/cons?

carbon/foam construction

seat.jpeg

 

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The concave top has been tried. It seems like it could be a good thing for keeping you attached to the seat. Arne Stahl's boat has it and I believe the new Morrison 3 does too.

The curved bottom will get sucked down whenever it hits the water. Maybe you could incorporate a planing step? Or just don't let it touch down.

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1 hour ago, Chris Maas said:

The concave top has been tried. It seems like it could be a good thing for keeping you attached to the seat. Arne Stahl's boat has it and I believe the new Morrison 3 does too.

The curved bottom will get sucked down whenever it hits the water. Maybe you could incorporate a planing step? Or just don't let it touch down.

The concave top was the key element of the design I was after.... I will definitely keep this aspect.

In my quest for circular - or rather spherical symmetry - I didn't even think of that - the getting sucked down bit - just like an upside-down aeroplane wing I suppose... Back to the drawing board :-)

I was kind of inspired by a study of the Sydney Opera House  that described the inherent strength of spherical arcs, as you can see in the linked video, from about 16:37. I'm not an engineer, but it seemed like a good idea.

Of course,I didn't consider hydrodynamics.

 

 

 

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single surface seat.pdf

Many moons ago I thought this might bee a cool way to build a seat.

Essentially 3 big piles of uni carbon connected by a double curved carbon nomex panel.  I never bothered too run the numbers, but in theory it is the same as a triangular truss.  Heel cups would be very shallow core drops and the whole thing could , more or less, be built in a single laminating step the skins would be about twice as heavy as the current seats because there is no inside skin.

The biggest disadvantage I could see was the total lack of buoyancy, which would make it still easier to screw up.

 

SHC

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tweaked... 

New%20Seat%20Design_zpsiwm355ub.jpeg

I-Beam structure in the guts for strength and hopefully this one would have enough of an edge that won't suck down if it hits the water

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