Paradox Micro Cruisers and "Bilge Runners"

**b.o.a.t.** · 19th July 2008, 01:44 PM

That it still does not go REALLY well to windward using both the undersized
centreboard and quite large (compared to the Paradox) runners together and only does
sortof OK on runners alone indicates one of the below is true

1/ The concept of bilge runners works best on deeper heavier boats
or
2/ The deeper hull in combination with the bilge runners is an optimum use of the idea or
3/ The concept has only marginal use and it is the deeper hull providing the lateral
resistance. Remember that the Paradox is a similar or similar hull depth to many
centreboardless cats which can also go to windward OK without centreboards. They
have more speed which helps generate lift, but also they have much, much more sail
which will require much more lift anyhow.

G'day MIK

Only thing I disagree with here is the word "or".
I think it is a combination of all 3. The runner works primarily as a chine fence turning
the whole of the deeper hull into a lifting body. Even on the light-weight Teal, the
runners make enough difference to provide manoeverability without the dagger board.
Without the runners, when rounding up, Teal just skates sideways nearly as fast as it
can go forwards.

One thing I neglected to mention earlier - my dagger board has very nearly the same immersed
surface area as Bolger's designed leeboard. It would be nice to think that the time I spent on it
attempting a NACA0012 profile makes it a more effective device than Bolger's simple flat lee-boards.
The key difference between Teal as designed & my boat is that I didn't use Bolger's double thickness
external chine logs. Since there are not heaps of reports that the as-designed Teal is a rotten sailor,
it stands to reason that I have merely replaced something provided by those chine logs.

Anyway, once I fit a decent sail (you have to admit the one on her now is pretty ordinary) I think the
higher speed will increase lift & effectiveness of both devices.

But in a way ... which reason is correct is unimportant because the concept of Matt's
Paradox boats is simply extraordinary and it is clear the the package works as a
whole - whatever theoretical spin is put on "why".

Hear, Hear !!

cheers
Alan J.

**Boatmik** · 19th July 2008, 11:58 PM

Howdy AJ,

Yes .. forgot about the sail! So we will see I guess!

MIK

**b.o.a.t.** · 26th July 2008, 02:59 AM

Originally Posted by Boatmik

Howdy AJ,
Yes .. forgot about the sail! So we will see I guess!
MIK

Well, as I wrote off list to you the other day MIK, I was going to start cutting polytarp Thursday.
But it got bit busy with the wife off to the doc & a few other bits & pieces (I'm supposed to be on sick leave!!). Then I was gunna start cutting today, but got caught on long phone calls, writing stuff for CFS & cooking. SO, I'm gunna start termorrer.
Or maybe Sunday. Or maybe Monday after shuffling pianos between rooms. Or possibly Tuesday after the plumber has done the tank... Or maybe next Julember...

Anyways, here's the latest version. It's the largest I can squeeze into a 2.9 x 3.5M polytarp. ($11) Any bigger & I have to go to a $22 polytarp.

53sq.ft is as big as a Nutshell 9'9" & near double the existing 30sq.ft.
I predict a significant increase in speed, & if I fail to get reefing right, a significant increase in involuntary wetness.

By the way, Ted sent the PDR plans on Thurs am (as expected). Haven't read them all the way through yet. Might print a few pages & show them to the bloke who organizes the local 'Shed' on Sunday. Not sure if it's something he'd go for - they tend to be into *really* low-cost projects. Scrap timber stuff. But seeds will be sown, and you never know...

The surgeon said last week I might be looking for "after the CFS" sooner rather than later...

cheers
AJ

**Vernr** · 26th July 2008, 10:59 AM

Originally Posted by b.o.a.t.

The surgeon said last week I might be looking for "after the CFS" sooner rather than later...

........I can really recommend the "after the CFS" bit, AJ..............there IS life after Fire Brigade!!!!

Cheers,
Vern

**b.o.a.t.** · 26th July 2008, 03:17 PM

Originally Posted by Vernr

........I can really recommend the "after the CFS" bit, AJ..............there IS life after Fire Brigade!!!!

Cheers,
Vern

Yeah, but you're a certified oldie, Sir Vern.

You've been there, done that, & rest on your laurels.
I can still pretend to be young, (at least to myself, and so long as I stay away
from mirrors & avoid genuinely young peoples' conversations !)

When I'm old I'll settle down to a more relaxing hobby.
cheers
AJ

**b.o.a.t.** · 15th October 2008, 12:34 AM

Well the fully modded Teal has hit the water at last, still unpainted.
Huge improvements in a number of areas.

With the bigger rudder, it turns when told to do so, not just when asked very nicely
with much coaxing and promises of ice-cream & lollies. Not in the league of Nutshell
or Tender Behind, but acceptable.

The larger sail accelerates the hull to full comfortable displacement speed quite easily.
Winds on West Lakes today were flukey 5 - 10 kts early, increasing to 10-15 kts later.
Was tempted to start reefed but glad I didn't. The low sail plan is really quite manageable
at these wind speeds. A couple of close calls, but no dunking today. Shaped the spars
loosely scaled to MIK's PDR balanced lug. Lots of flex in gusts. Yard looked close to
breaking a couple of times. Didn't tear out any grommets but the clew grommet
looked a bit strained - I built the sail edges a bit light as I was going to sew it... Not
enough power to plane, but enough to dig a big deep hole with big rolling following waves
to rock the kids doing outdoor ed in canoes. A lighter crew would go faster...

Odd behaviours... strong weather helm beating on starboard tack (sail carried to
starboard) but slight lee helm on port tack. Also seemed a little more powerful on
starboard tack.
Have added a couple of older pics of previous rigs as well as today pic at West Lakes.
cheers
AJ

**m2c1Iw** · 16th October 2008, 07:13 PM

Originally Posted by b.o.a.t.

Odd behaviours... strong weather helm beating on starboard tack (sail carried to
starboard) but slight lee helm on port tack. Also seemed a little more powerful on
starboard tack.

Look good AJ.

What are the tape crosses for?

Re the weather helm is this because you are acheiving a tighter sheeting angle on startboard? In any event the lug CE looks further aft but that does not explain lee helm on port, odd.

Mike

**b.o.a.t.** · 16th October 2008, 09:32 PM

Originally Posted by m2c1Iw

Look good AJ.

What are the tape crosses for?

Re the weather helm is this because you are acheiving a tighter sheeting angle on startboard? In any event the lug CE looks further aft but that does not explain lee helm on port, odd.

Mike

Thanks Mike.

The tape crosses... ah yes... making a failth statement... well, not exactly...

I spent the exhorbitant sum of $11 on the polytarp at a local Mitre 10. On hoisting it in
the back yard to figure out the rigging and getting some tension into it, was alarmed to
realise I could see right through it at a number of points in a line the full height from
peak to foot.

Looks like the manufacturers cutter took a half-hearted swipe at it. Didn't notice the
cuts while it was on the lounge room floor.

Was suddenly relieved I -hadn't- been able to repair the sewing machine I acquired
to sew all the seams... Saved a lot of work on what may be a fairly temporary sail.

Logically, the lee/weather helm means the centre of sail effort is moving forward
appreciably when the mast is not interrupting the sail shape. I sheet to the tiller,
about 50mm forward of the pintle, so any sail pressure -should- induce weather helm.
Should...

Possibilities....
The light polytarp is -very- soft, & my spars are very light so there perhaps isn't
enough fore-and-aft tension in the sail to resist the mast interruption. Could be a case
made for inserting a couple of battens like MIK's "Beth". Easy done, as per the gunter
main I had on Teal before this.
I also note I drew the sail with the foot somewhat aft of where it was sitting on the day.
That might make a difference too.
And I didn't lash the boom to the mast so it sagged out maybe an inch or two on port
tack.
Combination of all 3 perhaps ?
Hopefully one day MIK will cast his jaundiced eye across it, scratch his chin, shift his
weight from foot to foot, & announce it's a crock & should be ritually burnt...

More fiddling next time !! And hopefully see how it performs against a PDR.

cheers
Alan

**m2c1Iw** · 16th October 2008, 10:06 PM

Originally Posted by b.o.a.t.

The tape crosses... ah yes... making a failth statement... well, not exactly...

Mm.....wondered if it was a statement about our current economic malaise

Possibilities....
The light polytarp is -very- soft, & my spars are very light so there perhaps isn't
enough fore-and-aft tension in the sail to resist the mast interruption. Could be a case made for inserting a couple of battens like MIK's "Beth". Easy done, as
Hopefully one day MIK will cast his jaundiced eye across it, scratch his chin, shift his
weight from foot to foot, & announce it's a crock & should be ritually burnt...

Nah he's much too polite, more likely say it can be saved just needs more luff tension.

More fiddling next time !! And hopefully see how it performs against a PDR.

Well hopefully my PDR is not far off so a bit of comparitive data collection is on the cards soon

Mike

**Boatmik** · 17th October 2008, 08:10 AM

Howdy AJ,

The rig looks much more in proportion to the boat. I'll be betting it does EVERYTHING a lot better.

Nice to see that Mike is making some threatening noises!

MIK

**Clarkey** · 25th October 2008, 05:41 AM

Hello All,

Diving into this really late I know but I have always assumed that most of the windward performance of Paradox is probably due to that really big rudder hanging off the back. Combined with the 'lifting body' effect of the heeled hull shape and the relatively far aft CoE, the rudder must provide a big chunk of lift.

I guess that the chine runners help reduce leeway a bit but am inclined to believe that their main effect is to improve the steering characteristics and possibly directional stability.

Just my two-penneth worth.

Chris

**Boatmik** · 28th October 2008, 01:39 PM

I have been meditating on this ...

I think it is almost all to do with the depth of hull in the water vs the very modest sail area. The hull sides are enough of a "keel" by themselves and the rudder and "lifting body" arguments augment the effect of the deep hull.

Best wishes
MIK

**PAR** · 28th October 2008, 03:25 PM

Michael, picture one of these hulls heeled over at say 10 degrees and try to imagine the waterlines. The 'rounding tendency will be strong, so all you have to deal with is leeward slip and steerage. If the runners are well placed, much of the slip can be handled, especially if the bearing area and basic "centers" are relatively close to each other, which appears to be the case with Paradox. Of course there are shape and performance limitations with this approach, but it's valid enough to work moderately well.

**Boatmik** · 28th October 2008, 06:34 PM

Howdy Paul,

Yep, all visualised. Yes ... agreed about the moderately well (read my earlier posts about how good I think the Pardoxes are ... they really are a new type of boat in my book. There have been other micro cruisers, but the sense I get is most were real downwind machines.

I am impressed that the Paradoxes can get upwind at all ... and can see the reasons.

Just wanted to add the depth of immersed hull to the discussion because it is a major feature of the boats and that the chine lips won't be hugely effective on shallower boats.

Happily we have AJ here who is experimenting with exactly that.

Before the boat was a bit undercanvassed .. now it looks about right ... so will be interesting to see the difference it has made.

Best wishes
MIK

**b.o.a.t.** · 28th October 2008, 10:15 PM

Originally Posted by Boatmik

Just wanted to add the depth of immersed hull to the discussion because it is a major feature of the boats and that the chine lips won't be hugely effective on shallower boats.

Happily we have AJ here who is experimenting with exactly that.

Before the boat was a bit undercanvassed .. now it looks about right ... so will be interesting to see the difference it has made.

Best wishes
MIK

I thought the depth of immersed hull was -always- a key part of chine runner operation.
If acting as a fence, there needs to be water trapped above it to work. The more water
trapped, the more effective.

Found last week that it was possible to "switch" the winglets on & off by varying heel
and pitch. Nose up & sailing flat, the board had to do all the work. The winglets
seemed to be neutral or even lifting. Bringing the nose down applied water pressure to
their top surface & I could beel them 'bite', albeit gently. Add a small amount of heel,
and they'd bite harder, leeway being visibly reduced.

Adding to the idea of needing hull depth, Teal is very shallow draft, even shallower
once it gets close to hull-speed & mid-ships is in a trough. At speed, Teal needs to
heel to get any significant effect from the winglets. At speed of course, the NACA foil
is at its most effective & they are less needed, although provide noticeable improvement.

cheers
AJ

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