Designing to Steve Clark's proposed new rules

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Paul Scott
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Post by Paul Scott » Thu Dec 07, 2006 2:42 am

Chris-

Zoom sounds good. :oops: heh heh

Thanks for your brother's business name.

Paul
"Exuberance is better than good taste" -Flaubert

jimc
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Post by jimc » Fri Dec 08, 2006 1:28 am

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Andy P</i>(If a bit chopped V transom 'normal' hull instead of double-ender canoe hull.) - but maybe that's good.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I've been wondering whether that's am experiment worth making... At uneducated guesses I would think that the wider and more powerful then the more pressure recovery you get off the stern wave, but on the other hand I've noted with the Nethercott that you can immerse the stern and get some pressure recovery laterally off the topsides, and that the Nethercott is somewhat marginal in that the floew definitely tends to break off into turbulence instead: a finer stern would presumably be better in that respect...

Paul Scott
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Post by Paul Scott » Fri Dec 08, 2006 4:39 pm

Jim-

That's my bet. And that's why, I think, big wave boards (guns) taper so much to the stern. If I can just finesse the apparently (modelled) awful wave resistance with that shape - more fullness forward. Maybe max fullness at 50% of length is a good approach?

The Serenity Sailboard (which is long) seems to have a tapered stern, and in some of the pictures of it sailing, there is a small rooster tale off the stern. What does anyone make of that? Is it beneficial?

Didn't Dr. Whitman build an IC with skinny stern? I think Karl had an observation about it's stern wave off the wind . Karl?

Paul
"Exuberance is better than good taste" -Flaubert

Alistair
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Post by Alistair » Tue Jun 19, 2007 12:39 pm

A thought...
we have a height measurement 300mm (275 when rules are updated), but what happens forward or aft of that measurement, I take it that you would be in breach of the rules if you had a step down to the aft. This may be temting as getting c of g down seems a good idea. Which rule would stop you doing this? if it is the fore aft tape rule then it would mean that at the measuring station you would have to have a straight gunnel??
Alistair

Andy P
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Post by Andy P » Tue Jun 19, 2007 7:38 pm

The height is only measured at the BMS ( i e a station with a min height of 300mm (275) where the beam is not less than 750mm ), so in front and aft of the BMS, height can be more ( or less), but i expect a bump just to measure would not be in the spirit.
The meas tapes run along the hull centreline underneath 1m each side of the BMS
and side to side for 500mm each side

There is no restriction on gunwale shape in plan or elevation, so stepped gunwale line is OK - although there have been (unsuccessful) moves to limit the radius of curvature in plan.
My Mk 1 had a stepped gunwale at the seat position. Pyrahna ICs had a stepped gunwale at the shrouds.

Steve Clark
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Post by Steve Clark » Tue Jun 19, 2007 7:58 pm

What seems to be happening is that pushing the BMS aft forces a higher than you might desire sheer line further aft than you might desire it. So the trade off is suitably interesting.
The fat that boats with the BMS pushed max aft tend to be very difficult but not impossible to sail suggests to me that the limits are about right and in about the right places, so I guess I would resist some sneaky work around that disrupts the balance of trade offs.
Of course there is nothing to suggest that the deck has to be as high as the sheer line, on Josie I pushed the center line down and this has had a very salutary effect on her handling relative to Wonk. It looked like a small point and something one should be willing to surrender for skin area reduction and ease of building, but it really wasn't.
SHC
Beatings will continue until morale improves

Rhys Nolan
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Post by Rhys Nolan » Sat Sep 01, 2007 5:27 am

Hi, particularly addressed at Phil, thanks for all the inspiring work, a question though.
I note you suggest that foam bulheads and bow wedges. With the A cats, Tornadoes and even the Windrushes I was involved in building and maintaining I discovered very significant water absorption in some cases kilos of it, even in dry stored boats. Do you have a way to prevent this?
I suspect another reason for DC that most seem to have not addressed.
In some of the more remote regions, eg here in NZ there is very little support available when building (thanks Steve last time around) a Nethercott, and opening the rule could well allow more boats to be built. If this happens, even if the boats are not quite as fast then the exercise is well worthwhile.
Does the depth rule actually push the boats to be so deep looking? To my eye (sorry if I offend someone here) they are not nearly as pretty as the IC design. I remember an article in the newspaper at the Plymouth worlds, headline something like "If Stradivarius was building a boat, he would build an IC". Sorry but the designs so far don't light my fuse to build. May be efficient, but I still want a great looking boat too.
I am lead to wonder if the height of the dance floor above the waterline would contribute to difficult boat handling for the more senior of us?
Yes I do intend to build, but other than Phils boats I can't get to see too many photos?

Chris Maas
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Post by Chris Maas » Sat Sep 01, 2007 11:14 pm

Rhys,
As Steve says in the above post you can lower the sheer height aft by moving the Beam Measurement Station forward. This has the benefit of lowering the center of gravity and giving you a reasonable shroud base without resorting to the bumps that Andy and I have used. But that makes the waterlines fuller forward than I want to see so there's the trade off. Or of course you could use Phil's elegant approach of leaving the shrouds off.
I believe you could make a DC that looks very much like a Nethercott if you wanted to.
The cool thing is that, by most reports, all the DC's seem pretty quick despite the very different approaches.
Another fine thing is that the DC is seriously fun to sail. I think we all agree that upwind the IC is about the finest ride on the planet. Compared to the DC it feels like a school bus. We are definately on to something good here.
There are lots of DC pictures on the US site - Wonk, Josie, String Theory, John Kells new boat and Andy P's builds.

Rhys Nolan
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Post by Rhys Nolan » Sun Sep 02, 2007 5:50 am

At last! Thanks for the track to photos which I have spent way too long searching for!
Steve, now make a suggestion onb what would be a relatively easy boat to build and sail from the hypothetical and real designs, and i will start building the next day!

Phil Stevenson
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Post by Phil Stevenson » Mon Sep 03, 2007 9:15 am

Rhys,
My boat is deeper than min because I wrongly thought it would sail deeper in the water, esp through waves. I would lower the whole deck line if I built again.
If you decide to go my way please make early contact as I will surely have plenty of improvements on offer.
Yes, I have had styrene soak up water in leaky boats. The canoe has had some water in it a couple of times so the foam has probably gained some weight.
No leaks now but it is 7kg over min weight so a kg or so less soak would be handy/
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/

Steve Clark
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Memo to Rhys

Post by Steve Clark » Mon Sep 03, 2007 2:29 pm

Sorry to have been incommunicado, the russianbridepozac/viagralowinterestloaninvestmentopportunities had me distracted.
I have to amplify what Chris has said, the new rule just makes sailing canoes better. If you thought they were cool before, you will REALLY like them now.
Still one of the fastest boats out there is Bill Beaver's Lust Puppet.
Not quite as narrow as the rules allow so no funny stuff is required around the mast/shrouds and straight IC rigs would plug right in.
None have been built to 50 kg minimum. But given how the original stacks up, I think a light one would be right in the mix and would be a good starting point for any fleet building effort.
It is a single chine shape that you could probably bone out in a weekend and finish the next. The two that have been built here have been done over bulkheads.
I have the offsets and could email them to you.
PM me your address.
Then all you have to do is get er done and to McCray!
SHC
Beatings will continue until morale improves

kwittnebel
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Post by kwittnebel » Thu Sep 27, 2007 4:34 pm

Bill is planning to put together a stitch and glue ply Sock Puppet at DC weight, at some point. Sock Puppet is the multichine evolution of Lust Puppet, only with an arc bottom and an extra chine to give her a bit more initial stability. I have sailed Lust Puppet a lot and that hull shape will go fast if sailed correctly, but the Sock Puppet hull is probably equally quick and is definitely more forgiving.

The goal here is to generate a CNC cut file that anyone could use to get a set of panels that could then be stitched together to make a Sock Puppet DC from plywood. That would make the process of building a DC a lot more straightforward for the garage builder without access to a mold or plug - he or she could just call up Chesapeake Light Craft and have them send a set of panels, and then stitch them all together and reinforce. Sort of like the Phil Stevenson program.

All this will take some work in CAD and in the garage but it will probably happen eventually, sooner if there is demonstrated interest by others.

KW
Karl W
USA

kwittnebel
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Sock Puppet Test Case

Post by kwittnebel » Sat Sep 29, 2007 2:46 am

Those of you interested in what Bill's multichine iteration of Lust Puppet might look like as a DC, I narrowed it down to the minimum the DC rule will allow and posted some image files here:

http://picasaweb.google.com/Dr.Wittnebe ... IB8Ba6nHq0
Karl W
USA

Paul Scott
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Post by Paul Scott » Mon Oct 01, 2007 1:25 am

Displacement curve?

8)
"Exuberance is better than good taste" -Flaubert

kwittnebel
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Post by kwittnebel » Mon Oct 01, 2007 5:07 am

Hi Paul -

I'm pretty sure Bill would not build it this narrow, and his judgment is certainly better than mine in such matters. I just thought it would be interesting to see what it would look like at the limit.

If you are really interested in the numbers I'll see what I can do.
Karl W
USA

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