Facebook

Login

Support Sailonline

If you haven't already - join the SAILONLINE YACHT CLUB!

Please also consider making a donation - all amounts are greatly appreciated!

Board » General Discussion » Boat planning.

Page: 1 2 Next

Posted by
JB


Users avatar

Posts
305
Registered at
2013-03-07 08:54:34
2014-04-03 18:08:54 - Boat planning.
From Wiki:

“When it is at rest, a vessel's weight is borne entirely by the buoyant force. At low speeds every hull acts as a displacement hull, meaning that the buoyant force is mainly responsible for supporting the craft. As speed increases, hydrodynamic lift increases as well. In contrast, the buoyant force decreases as the hull lifts out of the water, decreasing the displaced volume. At some speed, lift becomes the predominant upward force on the hull and the vessel is planning.“.

So, is it possible to put some SOL boats planning? (I was not thinking on the 100 ft barge…).

Yes, it’s possible with just a simple adjustment on same parts of the boat Polar - have a look on the example for the VOR70 in the PDF attachment.

To keep the things interesting, the exact spot of the rising BS can be kept secret and up to everyone discover doing some extra time on helm.
Sail Fair.
Attachments
Posted by
bonknhoot


Users avatar

Posts
104
Registered at
2013-08-06 21:35:15
2014-04-03 19:39:05 - Re: Boat planing.
Hi Joao

Quickly from Wikipedia
V hull = 1.34 x sqrt{L}

where:
L is the length of the waterline in feet, and
V hull is the so-called hull speed of the vessel in knots

For a 70ft yacht, V hull is thus 8.37kn.

Hull speed is the speed at which the vessel pushing through the water creates two non-interfering waves, one at the bow and one at the stern, and without a good whack of extra power the vessel can't ride out over the top of the bow wave in particular, and leave it behind as it were. However, once it does it is effectively planing. So... lang verhaal kort, the VO70 already planes like an F16!
Clipping along
Posted by
sol


Users avatar

Posts
297
Registered at
2008-08-14 11:08:14
2014-04-03 19:58:55 - Re: Boat planning.
The various characteristics of a boat's performance are already incorporated into the composite polar diagram that enables 100% actualization unless changing course.

Posted by
kroppyer


Users avatar

Posts
346
Registered at
2010-02-05 15:25:55
2014-04-03 20:01:14 - Re: Boat planning.
Boats like the VO70 will plane, they are designed to do so. For boats that don't plane, there is a sort of maximum speed, hull speed. For the VO70 that would be about 12kts (or a little more). So whenever a VO70 sails faster than 12kts it's probably planing. A VO70 probably starts planing before it reaches its boatspeed.

But what that means, is that the polar, as is, already includes speeds at which the VO70 is planing. Attached is an image of the VO70_v4 polar with a line at boatspeed=12kts

I reality there is a range in boatspeeds (also depends on wind/heeling angle) where the boat sometime planes, and sometimes doesn't. Usually you are surfing down a with a wave until you overtake it (or it overtakes you, when you're in a slower boat). So at some twa/tws the boatspeed is far from constant. The polar contains averaged speeds.

A way to simulate planing would be by simulating surfing off waves. Giving a 10% bonus for 1 or 2 jumps, and then a 10% penalty after for some jumps after that. Or something like that.

___
EDIT: I see I was a little late, it's (almost) all already explained.

--- Last Edited by kroppyer at 2014-04-04 08:27:59 ---
Attachments
Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2014-04-03 20:13:43 - Re: Boat planning.
Surely the lines shown in the polar diagram already show the boat speed, wind speed and wind angle at which the hull is planing.
(Not to be too critical, it is "PLANING" without the double-"n", after the verb "to plane")
Planing is shown by a small bulge in the polar lines at certain wind angles and speeds.
Nothing further needs to be done!
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
bonknhoot


Users avatar

Posts
104
Registered at
2013-08-06 21:35:15
2014-04-04 08:24:07 - Re: Boat planning.
A VO70 planing. As you can see, the bow wave has moved aft.
Clipping along
Attachments
Posted by
JB


Users avatar

Posts
305
Registered at
2013-03-07 08:54:34
2014-04-04 10:21:06 - Re: Boat planning.
Thank you Jan, Kroppyer, Sol and Rod.

The first and my friend, for bringing some hydrodynamics to the subject.
The second for is enlighten on boat Polars (and, by the way, also for his superb tool “SPINNACER”).
Finally Rod, for bringing the “planing” in the right plane.

So, the VOR70 can plane upwind?
From the CSV file, at TWS = 12 kts and TWA = 51º, the corresponding BS = 12,154 kts (see also “SPINNACER” graphic in the attachment), which is above the hull speed calculated with empirical formula (note: dimensions are not coherent, speed units vs. length units),
V,hull = 1,34 x sqrt (L) = 1,34 x sqrt (70) = 11,211 Kts.

Or is it just possible for the VOR70 to be above his hull speed but not yet in planning mode in those conditions?

Well I’ve never thought that the VOR 70 Polar already incorporated the planning effect, as it curves shapes doesn’t show it at all ( in a mathematic perspective: no “really” singular points in the curves).

My primary idea was to bring some further interest and action to the race. An extra BS coming from planing would be nice, especially if the Polar zone for that purpose had to be discovered by each one (hence the different shapes suggested for that particular zone).
In another perspective: a premium for being more time at the helm.
I think the “non-routers”, namely, would appreciate that.
Sail Fair.
Attachments
Posted by
A2


Users avatar

Posts
347
Registered at
2009-10-26 00:39:42
2014-04-04 16:06:49 - Re: Boat planning.
*(Posted earlier as sol)

Everyone is given equal marks for skillful sailing such that the competition is decided by the judgement of the afterguard regarding navigation with respect to the weather & optimum route to destination.

--- Last Edited by A2R at 2014-04-04 16:24:44 ---
None so blind
Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2014-04-06 18:05:18 - Re: Boat planning.
There is something of a difference in the planing of a motorized speedboat hull, compared with planing in a sailing yacht. The equations describing the speed above which planing can occur assume that a considerable increase in horsepower is available, and that the hull will then plane.
This is usually not the case in sailing boats, where sail pressure results in max hull speed. Any increase in speed beyond this point must come from a large increase in windspeed. This is unlikely to occur in sailing because it usually results in a 'knock-down'.
Instead, what we see happening is that hull speed gradually increases with increasing windspeed, and that natural result of this is that the hull gradually rises in the water, due to its shape. With reduced drag comes additional hullspeed, so that the hull is moving a small amount faster than it could if it still maintained the same immersed volume and surface area that it would have if measured while at rest. This explains why a polar diagram can indicate a higher hullspeed than the simple equation should allow.
The net effect of all this is that a displacement sailboat approaches planing speeds gradually.
This phenomenon interests me because I have been sailing and designing small radio-control sailboats in the Footy Class, and they exhibit a phenomenon called "nose-dancing", where the pressure of the wind on the sails causes the bow to submerge. Unlike larger boat classes, this is an almost stable condition that may continue for several seconds, until a broach occurs.
The object of my current interests in Footy design involve trying to prevent "nose-dancing".
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
JB


Users avatar

Posts
305
Registered at
2013-03-07 08:54:34
2014-04-07 11:12:34 - Re: Boat planning.
Dear Rod, I’m no specialist on boat design. Anyhow, this is what I think.

The Footy has a short hull - see pictures and plans in the attachment (data from http://www.scalesailing.com ).
Without any disregard for the Footy, she has a shape like a “cube”: short length, high freeboard.
The mast position is pushed to the bow and the bottom of the hull is banana shaped and very light, so, the extremities lack material/buoyancy, principally the bow.
Dynamically speaking, the result has to be a boat with a high frequency longitudinal motion in both planes (short pendulum like):
1 - In the vertical plane (passing the boat’s “CG”) - causing the so called “nose diving”, with this motion helped by the curved hull shape;
2 - In the horizontal plane - causing the “nose dancing”.

She doesn’t have enough length to cushion in due time the instability created by the above mentioned motions, so , Rod , she must be very hard to control, even in light wind conditions (immediately transferring the boat’s reaction to the bow when the wind enters and promoting the “nose diving”), and, I just imagine her sailing in little choppy waters…

If the class rules permit, try to bring aft the mast’s application point and some weight.
Maybe she will:

3 - Lose some upwind ability;
4 - Gain stability, and,
5 - a little downwind speed.
Sail Fair.
Attachments

Page: 1 2 Next

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

Melbourne Osaka Cup Double-Handed Yacht Race 2025

Welcome once again to what these days is Sailonline’s almost annual virtual Melbourne to Osaka Yacht Race. In real life, this double-handed 5500 nm race between these two sister cities, one deep in the southern hemisphere, the other high in the northern hemisphere, is run every four to five years, and this year is such a year. So, this year’s online version is in sync with the Melbourne Osaka Cup 2025 organised by the Ocean Racing Club of Victoria (ORCV), and the Sandringham (SYC) and Osaka Hokko (OHYC) yacht clubs. We’ll be racing the well-known First 40, a popular size of boat which should be a good match for many of the boats entered in the real race. With the doldrums unavoidably lying across our course, you can expect to be at virtual sea for at least a month!
Race #1669
INFO by brainaid.de
First 40 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Mar 16th 06:00 Registration will open soon

▶ Flash
GO TO RACE

Lake Ladoga Ice Race


For our second race of the 2025 Ice Yachting series, we shall risk disturbing another sect of monks, these of the Orthodox persuasion rather than Buddhist. Good ice is often found in remote places, and remoteness breeds contemplation, and Valaam Island at 61.3N in the north east corner of Lake Ladogo is as remote as it gets. Surrounded by pristine ice in winter, we find there one of the great monasteries of Russian Orthodoxy. So, get your visa’s, fly to St Petersburg, take the N-121 north to Vladimirovka, and get your DN-skates on for another no-PL monk-minding race, this time of 110nm in length, out around Valaam, then Derevnya, to finish near Berezova.
Race #1851
INFOby brainaid.de
DN PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: DN - SYC
Race starts: Mar 10th 09:00 Registration will open soon
▶ Flash
GO TO RACE

Walyalup Sprint 2025


Once upon a time, aboriginal legend has it, the country of the Whadjuk people extended west from the present day Fremantle shoreline out to Rottnest island, but Walyalup as they called it was lost to the sea, and this sprint takes you across those inundated lands, round reefs and across shoals, 25nm in a Dufour 34. For the Walyalup, March fell in Bunuru, the hottest season of the year, which meant living near the water. Expect hot easterly winds, and cooling afternoon sea breezes with little to no rain. Perfect weather for a sail.
Race #1897
INFO by brainaid.de
Dufour 34 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
SPRQ1 - SPRCH - SUPSOL - SYC
Race starts: Mar 08th 03:00 Registration Open!
▶ Flash
GO TO RACE

Tristan da Cunha to Coronation Island 2025

The adventure continues as we embark on the second leg of the RWW series, racing from Tristan da Cunha to the remote and uninhabited Coronation Island, NO, Elephant Island. Nestled between the Scotia Sea and the Weddell Sea, both island were named by 19th C British whalers. Prepare for a thrilling journey through the Roaring Forties and Furious Fifties, where relentless winds and challenging seas will test the mettle of every crew. This leg will be sailed aboard the historically iconic Steinlager II and is part of the prestigious OCCH 2025 series. The RWW series ranking will be determined by each team's best 7 out of 8 race results, so every moment counts! Are you ready to face the ultimate test of skill and endurance?
PRIZE: SMPF
Race #1890
INFO by brainaid.de
Steinlager II PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ1 - RWW - OCCH - SUPSOL - SYC
Race starts: Mar 03rd 11:00 Registration Open!
▶ Flash
GO TO RACE

San Diego Islands Race 2025


Sailonline is proud to once again team up with the San Diego Yacht Club for the annual Islands Race! This 140nm course will take our SOLers from Long Beach, around the Catalina Islands, and down to San Diego, testing skill, strategy, and precision.

This year, we’re racing in the sleek and powerful Ker 40, a high-performance yacht built for speed. With shifting winds and tactical routing, every decision will count as you battle for victory.

The competition is fierce—the race is on! See you at the start line!
Race #1881
INFO by brainaid.de
Ker 40 PARTICULARS
NAM_AWIP WX Updates:
0245 / 0845 / 1445 / 2045
Ranking: SYC
RACE CLOSE: Friday,
March 7 at 2300 UTC.
Race starts: Feb 28th 20:30 Registration Closed
▶ Flash
GO TO RACE

Sinbad by Balloon 2025 - Dondra to Toamasina


Above you see a stratospheric balloon, that if only we had gribs at that altitude would get blasted along quite rapidly and predictably. Alas we just have our SOL balloon that sails rather lower to the sea and that we have crossed the Atlantic in, west to east, last year for the first time in the southern hemisphere. So much fun was had by all, that this year we will attempt the Indian Ocean, but in four legs. Another great piece of fiction, the voyages of Sinbad By Balloon not magic carpet, although you may need a bit of magic to make any progress at times. Pack your wicker basket full for your first leg of at least 2300nm from Sri Lanka to Madagascar; it’s not a picnic hamper, you could be in the air for longer than you hoped!
Race #1883
INFOby brainaid.de
SOL Balloon PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC - SBB
RACE CLOSE: Tuesday,
March 18 at 2300 UTC.
Race starts: Feb 05th 11:00 Registration Closed
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member WRmirekd
  2. Sailonline Yacht Club Member Patrick70119
  3. Sailonline Yacht Club Member vida
  4. Sailonline Yacht Club Member CriticalHippo
  5. Sailonline Yacht Club Member KaSToR
  6. Sailonline Yacht Club Member rafa
  7. Sailonline Yacht Club Member Kipper1258
  8. Sailonline Yacht Club Member FreyjaUSA
  9. Sailonline Yacht Club Member bonknhoot
  10. Sailonline Yacht Club Member CollegeFund

View full list

Series

Mobile Client

SYC members have the benefit of access to our mobile/lightweight web client!

The mobile client