`

Author Topic: Maximum Displacement Hull Speed  (Read 9792 times)

BigZ

  • Waikiki Status
  • *
  • Posts: 43
    • View Profile
    • Email
Re: Maximum Displacement Hull Speed
« Reply #30 on: March 20, 2023, 08:40:24 PM »
The bottom line. If you have stamina and technique you can flat water start on any foil and any board.  ;).

Check this clip. Way before we had all this advanced equipment ... To summarize. You get on the board (prone sinker by the way) and than you paddle really fast ...  ;)

https://youtu.be/diljo6EGDdQ?t=278




I could only comment on this from experience after todays 1st Flatwater Paddle up.

I had been getting enough advice so after my foil session I went to the harbor and DID IT!  I confirmed what people have been saying.  4 phases

1) Initial Displacement Phase - Slowly paddle and get rhythm @ 50% power

2) Start the bob, or the porpoising, still @ 50%

3) Increase power and cadence stroking @ 70% with rhythmic Bob start semi-skipping

4) Increase to 90% Wait until you feel the Foil.  Then go another 4 strokes.  Don't pop too early or you crash down.

Each of these phases take advantage of the hulls shape.
1) Displacement
2) Nose Rocker, tail shape and Chines
3) Flati-sh bottom and chines allowing for skip and release
4) Final takeoff - Again Flat bottom for skip and chines for release

Sailfish Board @ 128 liters, 7' 9" x 21" wide, Axis 1300, 450P tail, 75 cm mast.
https://www.youtube.com/watch?v=YNN1rSLDW0c
James Casey compared:
PNG 1310 [area 2080] 8 strokes (5 displacement / 3 bob)
PNG 1150 [area 1788] 11 strokes (4 displacement / 7 bob)
PNG 1300 [area 1712] 9 strokes (4 displacement / 5 bob)
HPS 1050 [area 1502] 16 strokes (4 displacement / 12 bob)
HPS 880 [area 1122] 19 strokes (6 displacement / 13 bob)
ART 1099 [area 1144] 14 strokes (4 displacement / 10 bob)
« Last Edit: March 20, 2023, 09:03:16 PM by BigZ »

PonoBill

  • Cortez Bank Status
  • *****
  • Posts: 25803
    • View Profile
Re: Maximum Displacement Hull Speed
« Reply #31 on: March 20, 2023, 10:47:14 PM »
Planing could happen during touchdown, though it's more like a skipping rock than a planing hull, and it's worth remembering that skipped rocks flip over with each touch. It's too dynamic a situation to even guess what's going on, though SurfGTP coupled to a few supercomputers could collect enough data and crunch it to model it.

Ok - I was like "what?" -- I had thought it had to be spun horizontally - and the gyroeffect would not go well with flipping over - but I also checked Google, got lost in the weeds/watched some fun videos including one about converting a clay-pigeon thrower into a "skipper" (of exact same discs, not actual rocks) - there are even some things on not-so-flat rocks and their skipping physics but I can't find anything about flipping?

You'd need to be a lifelong geek and present-day geezer to find the right reference. When I was a kid there was a challenge in Scientific American Magazine to explain the odd pattern that skipping rocks leave in the water. I chucked a few hundred rocks in the Charles River trying to figure it out. Close observation shows that there's a long skip, then a very short one, then a long one...etc., etc. Some guy painted a skipping disc with stripes that showed rotation, and different stripes to differentiate top from bottom, then ran a high-speed camera to record the skips. Turns out that when the stone hits the water it creates a depression that has a definite bow wave pushed up by the stone's forward velocity. The skipped stone "trips" on the bow wave and flips over, taking a short hop, then because of its rotational momentum on the second landing flips higher for the next hop. Lather, rinse, repeat. There was an exhibit showing the experiment in the Boston Museum of Science for quite a few years, which is also where I learned that water molecules in a wave don't move forward, they move mostly up and down in an epicycle.

I can remember a Scientific American article from the late 50s when I was about ten years old, but I have no idea where I put the .6mm extruder hot end that I set down "someplace handy" when I was swapping it in. I've cleaned the entire garage looking for it.

« Last Edit: March 20, 2023, 11:47:52 PM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Admin

  • Administrator
  • Cortez Bank Status
  • *****
  • Posts: 6420
    • View Profile
    • StandUpZone
    • Email
Re: Maximum Displacement Hull Speed
« Reply #32 on: March 21, 2023, 12:06:54 AM »
Wonder if they noticed that all of their strokes are bob strokes?

Hdip

  • Peahi Status
  • *****
  • Posts: 507
    • View Profile
Re: Maximum Displacement Hull Speed
« Reply #33 on: March 21, 2023, 08:15:17 AM »
You'd need to be a lifelong geek and present-day geezer to find the right reference.

I did a quick google search and found scientific papers on skipping rocks. They talk a lot about spinning rotations. I didn't see any references to flipping rotations in a quick skim. Then I just cheated and searched youtube for rock skipping in slow motion.

https://www.youtube.com/watch?v=5n7GKxesC0U&t=52s

PonoBill

  • Cortez Bank Status
  • *****
  • Posts: 25803
    • View Profile
Re: Maximum Displacement Hull Speed
« Reply #34 on: March 21, 2023, 10:18:19 AM »
Cool video, it shows the puzzling big spout that occurs after the rock leaves the surface, but isn't close enough, or high rez enough to see what's going on. I doubted the flipping aspect for a while based on my own experiments (if tossing rocks can be termed an experiment) since it doesn't look like it happens, though even in this video there's evidence of something funny going on. It's a bit easier to see as the rock slows down. The short skip is very short, like an inch or so. If you skip a rock in wet sand it's easy to see.

With current technology, it should be easy to see what happens. There's some debate about the flip, though it explained the weird patterns nicely back when I read the original article. I've seen attempts to describe the dynamic mathematically. They get ugly fast.

So I cheated too and asked ChatGTP: Do stones flip when they are skipped on water?

Answer from the all-knowing AI soon to be our overlord:

Yes, when you skip a stone on water, it can flip over several times before it eventually sinks. This is because of the physics of the stone's motion and the properties of the water's surface tension.

As the stone hits the water, it creates a depression or dimple in the water's surface, which creates a force that pushes the stone back up. If the stone is moving fast enough and at the right angle, this force can cause the stone to flip or bounce off the surface of the water several times.

However, not all stones are ideal for skipping. Stones that are too round or too flat may not skip as well as stones that are more oblong in shape. Additionally, the water's surface tension can also affect how well a stone skips. If the water's surface is too calm or too rough, it may be more difficult to skip stones successfully.

Not exactly conclusive. So I asked a question more in keeping with ChatGTP's strong suit--taking over the world:

What is the best form of government for managing humans

"There is no single "best" form of government for managing humans, as different systems can work better or worse depending on a variety of factors such as cultural context, history, and economic development. However, there are a few general principles that many people believe contribute to effective governance:

    Representation: Governments that are responsive to the needs and interests of their citizens tend to be more effective and legitimate. This often means some form of representative democracy, where citizens can choose their leaders and hold them accountable through free and fair elections.

    Separation of powers: It is often considered important to have a separation of powers between different branches of government, such as an executive, legislative, and judiciary. This helps prevent any one group from having too much power and can promote checks and balances.

    Rule of law: Effective governance also depends on the rule of law, where laws are clear, consistent, and applied equally to all citizens. This helps ensure stability and predictability, which can encourage investment and economic growth.

        Transparency and accountability: Good governance often requires transparency and accountability, where government actions are open to scrutiny and officials can be held responsible for their decisions.

In practice, different governments may prioritize these principles to varying degrees, and the effectiveness of a particular system may depend on a range of factors, such as the level of corruption, economic inequality, and social cohesion in a given society."

I'm surprised it didn't just say "Let AIs Rule, die stupid human."
« Last Edit: March 21, 2023, 10:41:17 AM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Hdip

  • Peahi Status
  • *****
  • Posts: 507
    • View Profile
Re: Maximum Displacement Hull Speed
« Reply #35 on: March 21, 2023, 10:59:11 AM »

Beasho

  • Cortez Bank Status
  • *****
  • Posts: 3200
    • View Profile
Re: Maximum Displacement Hull Speed
« Reply #36 on: March 21, 2023, 11:17:29 AM »
Cool video, it shows the puzzling big spout that occurs after the rock leaves the surface, but isn't close enough, or high rez enough to see what's going on. I doubted the flipping aspect for a while based on my own experiments (if tossing rocks can be termed an experiment) since it doesn't look like it happens, though even in this video there's evidence of something funny going on. . . .

The challenge with skipping rocks was always to find a Flat, but round-ish shape that you could spin.  When spinning, as the rocks are in the video, there is almost no way that they can flip.  The key was to spin them and huck them so they descend gently so the edge wouldn't catch.  5 skips was just the price of entry.  15 good.  20 -> Infinity Great.  The only way to get to infinity was for the rock to settle and stop skipping, then to just GLIDE cleanly across the surface before submerging. 

Beasho

  • Cortez Bank Status
  • *****
  • Posts: 3200
    • View Profile
Re: Maximum Displacement Hull Speed
« Reply #37 on: March 21, 2023, 11:18:20 AM »
PS: Hopefully the AI considers us like Dogs.  Fun, loveable and worth having around.

Fishman

  • Peahi Status
  • *****
  • Posts: 517
    • View Profile
    • Email
Re: Maximum Displacement Hull Speed
« Reply #38 on: March 21, 2023, 05:58:12 PM »




I like the following graphic.  It shows where a Barracuda shape (Yellow graph) ~ 8 feet X 19 inches maxes out at 4.5 mph.   At that point you better be porpoising and converting to hydro-foil lift.
This is a great traffic but it would be so much more helpful and relevant if it was separated. One with the same width but different lengths, and I a with the same length and different widths.  Id assume it's already been done but finding it...
SupSurfMachine 9'9" longboard
SupSurfMachine  8'2" funboard

surfcowboy

  • Cortez Bank Status
  • *****
  • Posts: 4928
    • View Profile
Re: Maximum Displacement Hull Speed
« Reply #39 on: March 21, 2023, 09:18:34 PM »
Nitro-powered copy writers.Though let's see, one percent would be about .04 mph or 0.06 feet per second, so .72 inches per second. So sure, that could be measured, though maybe not on the water."

Bless you Pono. I did this math but didn't want to be a jerk and post it. 😂 Glad you did. Hahahahaha.

SUPeter

  • Sunset Status
  • ****
  • Posts: 454
    • View Profile
    • Email
Re: Maximum Displacement Hull Speed
« Reply #40 on: March 22, 2023, 08:35:40 AM »
Planing could happen during touchdown, though it's more like a skipping rock than a planing hull, and it's worth remembering that skipped rocks flip over with each touch. It's too dynamic a situation to even guess what's going on, though SurfGTP coupled to a few supercomputers could collect enough data and crunch it to model it.

Ok - I was like "what?" -- I had thought it had to be spun horizontally - and the gyroeffect would not go well with flipping over - but I also checked Google, got lost in the weeds/watched some fun videos including one about converting a clay-pigeon thrower into a "skipper" (of exact same discs, not actual rocks) - there are even some things on not-so-flat rocks and their skipping physics but I can't find anything about flipping?

You'd need to be a lifelong geek and present-day geezer to find the right reference. When I was a kid there was a challenge in Scientific American Magazine to explain the odd pattern that skipping rocks leave in the water. I chucked a few hundred rocks in the Charles River trying to figure it out. Close observation shows that there's a long skip, then a very short one, then a long one...etc., etc. Some guy painted a skipping disc with stripes that showed rotation, and different stripes to differentiate top from bottom, then ran a high-speed camera to record the skips. Turns out that when the stone hits the water it creates a depression that has a definite bow wave pushed up by the stone's forward velocity. The skipped stone "trips" on the bow wave and flips over, taking a short hop, then because of its rotational momentum on the second landing flips higher for the next hop. Lather, rinse, repeat. There was an exhibit showing the experiment in the Boston Museum of Science for quite a few years, which is also where I learned that water molecules in a wave don't move forward, they move mostly up and down in an epicycle.

I can remember a Scientific American article from the late 50s when I was about ten years old, but I have no idea where I put the .6mm extruder hot end that I set down "someplace handy" when I was swapping it in. I've cleaned the entire garage looking for it.



Yes, water molecules in a wave generally move up and down, but if those waves are created by wind, the uppermost water molecules travel slightly forward with each circular motion.  This makes catching a wind blown swell a little easier than catching the wake off a passing lobster boat.

tarquin

  • Sunset Status
  • ****
  • Posts: 367
    • View Profile
Re: Maximum Displacement Hull Speed
« Reply #41 on: March 22, 2023, 01:07:50 PM »
Unless you are foiling.

StellaBlu

  • Malibu Status
  • **
  • Posts: 76
    • View Profile
    • Email
Re: Maximum Displacement Hull Speed
« Reply #42 on: March 30, 2023, 05:58:23 AM »
There is a ton of interesting content in this thread for a design newb like me (thank you to the contributors). 

One thing that I'm trying to better understand is how to compare hard chines vs a more rounded hull on a pintail downwind board.  I generally understand the pintail, but more designs have very hard chines in the rear portion of the hull leading into the pintail (Baracuda, FFB Dagger, Sultan, Axis, Etc...).  There are some exceptions with more rounded features (Dale Chapman and Sunova), but they are not the norm.

Wouldn't the harder chines create eddys and drag?  wouldn't softer chines allow for better water release and perhaps less wetted area?

Please help a newb understand the hull design philosophy!  Thanks again.

SUPeter

  • Sunset Status
  • ****
  • Posts: 454
    • View Profile
    • Email
Re: Maximum Displacement Hull Speed
« Reply #43 on: March 30, 2023, 09:50:55 AM »
There is a ton of interesting content in this thread for a design newb like me (thank you to the contributors). 

One thing that I'm trying to better understand is how to compare hard chines vs a more rounded hull on a pintail downwind board.  I generally understand the pintail, but more designs have very hard chines in the rear portion of the hull leading into the pintail (Baracuda, FFB Dagger, Sultan, Axis, Etc...).  There are some exceptions with more rounded features (Dale Chapman and Sunova), but they are not the norm.

Wouldn't the harder chines create eddys and drag?  wouldn't softer chines allow for better water release and perhaps less wetted area?

Please help a newb understand the hull design philosophy!  Thanks again.

Just the reverse-  water likes to stay attached to curved surfaces as it flows. Not only is water moving longitudinally along the length of the board but, it is also moving laterally as the board slaps down onto the waters surface as we pump and hop. These hard chines allow this lateral moving water to relaease .  When hulls are curved, the water will ride up along that curved hull trying very hard to stay attached to the hull.  All this added water weight is detrimental to an easy and clean separation of hull from water. I hope this helps.

StellaBlu

  • Malibu Status
  • **
  • Posts: 76
    • View Profile
    • Email
Re: Maximum Displacement Hull Speed
« Reply #44 on: March 30, 2023, 10:34:29 AM »
There is a ton of interesting content in this thread for a design newb like me (thank you to the contributors). 

One thing that I'm trying to better understand is how to compare hard chines vs a more rounded hull on a pintail downwind board.  I generally understand the pintail, but more designs have very hard chines in the rear portion of the hull leading into the pintail (Baracuda, FFB Dagger, Sultan, Axis, Etc...).  There are some exceptions with more rounded features (Dale Chapman and Sunova), but they are not the norm.

Wouldn't the harder chines create eddys and drag?  wouldn't softer chines allow for better water release and perhaps less wetted area?

Please help a newb understand the hull design philosophy!  Thanks again.

Just the reverse-  water likes to stay attached to curved surfaces as it flows. Not only is water moving longitudinally along the length of the board but, it is also moving laterally as the board slaps down onto the waters surface as we pump and hop. These hard chines allow this lateral moving water to relaease .  When hulls are curved, the water will ride up along that curved hull trying very hard to stay attached to the hull.  All this added water weight is detrimental to an easy and clean separation of hull from water. I hope this helps.

Thanks for the reply - this is helpful.  If I understand correctly, my assumption that the hard chines were disturbing the flow, wasn't wrong, but it is an oversimplification (assuming linear flow).  My oversimplification didn't take into account the priority of releasing the hull from the water surface. 

So basically if the board weren't on a foil, the rounded chines would be faster, but because the board is on a foil and needs to release from the surface, the hard chines are a beneficial compromise.  But in that case, why do foiling monohull sailboats generally have rounded hull features (AC36)?

Taking this one step further, why do these boards then have soft chines towards the nose?  On a touchdown, isn't release a priority again (in which case harder chines would be beneficial)?

Am I understanding this correctly?
« Last Edit: March 30, 2023, 10:42:31 AM by StellaBlu »

 


* Recent Posts

post Re: AWSI Show 2023
[General Discussion]
burchas
September 22, 2023, 04:44:42 PM
post Re: AWSI Show 2023
[General Discussion]
Hdip
September 22, 2023, 08:15:13 AM
post Re: AWSI Show 2023
[General Discussion]
Thatspec
September 22, 2023, 01:33:23 AM
post Re: Manx EV
[Random]
PonoBill
September 20, 2023, 06:51:47 PM
post Re: Foil Videos
[Foil SUP]
Hdip
September 20, 2023, 09:03:23 AM
post Re: Foil Videos
[Foil SUP]
Beasho
September 20, 2023, 05:48:54 AM
post Re: Foil Videos
[Foil SUP]
Beasho
September 20, 2023, 05:38:59 AM
post Re: Manx EV
[Random]
Badger
September 20, 2023, 03:39:00 AM
post Re: AWSI Show 2023
[General Discussion]
Admin
September 19, 2023, 12:36:49 PM
post Manx EV
[Random]
Dusk Patrol
September 19, 2023, 11:11:42 AM
post Re: Axis 1099 $250 shipping in the US
[Classifieds]
jondrums
September 18, 2023, 10:09:14 PM
post Re: AWSI Show 2023
[General Discussion]
blueplanetsurf
September 18, 2023, 06:13:17 PM
post Re: Axis 1099 $250 shipping in the US
[Classifieds]
Hdip
September 18, 2023, 03:27:50 PM
post Re: AWSI Show 2023
[General Discussion]
Hdip
September 18, 2023, 03:13:17 PM
post Re: AWSI Show 2023
[General Discussion]
blueplanetsurf
September 18, 2023, 01:17:55 PM

* Recent Topics

topic AWSI Show 2023
[General Discussion]
burchas
September 22, 2023, 04:44:42 PM
topic Manx EV
[Random]
PonoBill
September 20, 2023, 06:51:47 PM
topic Foil Videos
[Foil SUP]
Hdip
September 20, 2023, 09:03:23 AM
topic Axis 1099 $250 shipping in the US
[Classifieds]
jondrums
September 18, 2023, 10:09:14 PM
topic GT2200 - $600
[Classifieds]
rw2
September 17, 2023, 05:16:47 PM
topic Gong Sirus XXL Complete Foil Kit - 156cm!
[Classifieds]
Seattle-Wind
September 17, 2023, 05:07:35 PM
topic Yet another new board thread
[Gear Talk]
Noo Noo
September 17, 2023, 02:50:39 AM
topic F-one Strike 4.5M V3 - $850
[Classifieds]
burchas
September 16, 2023, 08:52:35 PM
topic Narrow vs Wide Boards: Beginners to Advanced
[Wingsurfing, Windfoiling, Wingfoiling, Wing SUP]
Dontsink
September 15, 2023, 01:50:15 PM
topic All in One
[The Shape Shack]
PonoBill
September 15, 2023, 01:13:37 PM
topic Anyone in New England have a beginner surfsup to sell ?
[SUP General]
Noo Noo
September 15, 2023, 10:19:00 AM
topic FS - Project Cedrus 80cm Carbon Mast
[Classifieds]
DoobieDad
September 15, 2023, 06:24:05 AM
topic Back surgery advice
[Training, Diet, and Fitness]
surfafrica
September 14, 2023, 05:22:01 PM
topic Accessories
[Classifieds]
kitesurferro
September 14, 2023, 01:12:25 PM
topic Ultralight Board II SUP Foil Bumblebee
[The Shape Shack]
Vancouver_foiler
September 14, 2023, 11:13:59 AM
SimplePortal 2.3.7 © 2008-2023, SimplePortal