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Connor.kainalu

Chines in yacht design

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In recent years the stylised look of the modern racing monohull ha come to include a plum or reverse bow, a square top mainsail, fractional jib, and vertical chines in the aft third. Are vertical chines really helpful speedwise? I know that corners are really bad on a yacht, but does the nature of the angle being parallel to the flow cause any difference? And has anyone experimented with chines angled inboard? And does the sharpness matter?

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You can count reverse bows on monohulls on one hand, so it can't be called a trend. I don't even know what a vertical chine is, perhaps you'll post a picture.  if such a thing exists, it's rare enough not to be a trend. I guess the designers would have the best answer for their purpose. The race course is the best measure of their effectiveness.

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I would think that having the topsides come up vertically from the chine would help to reduce wetted surface.  Any angle to the topsides at a chine would tend to increase wetted surface.  Angling the topsides outwards would also add weight, not only for the additional amount of topsides (hull) but also for the deck that would have to be extended to cover the now wider boat.  Angling the topsides inwards might reduce the deck width and weight, but would still add to the hull weight (due to the extended sides of the hull) and the wetted surface. Angling the topsides inward might also lead to reduced buoyancy as the hull submerged more... not necessarily what you want if you're surfing down a wave and might get pooped.  

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My guess is this is another rating aberration. Beam generally cost you in rating, so just wack it off 'here' and pretend it's narrower. Sharp angles traveling through fluids are rarely fast. 

Plumb bow and square top main there is some theoretical basis for, confirmed by experience. They are faster, and are also penalized. 

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Square top is an attempt to get an elliptical lift distribution spanwise. So that is based on actual efficiency.
Plumb bows on "box rating" boats are merely to maximise wetted length. No superior to some rake except for a small weight saving.
Chines are never helpful at sailboat speeds. Except for skiffs and other truly planing boats. This now includes some keelboats but none of the production ones.

Fads spread like wildfire.

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The chines are helpful with a Volvo 70 -limited by beam and water ballast. The chine allows you to get more water outboard but keep the waterline beam less. And they are at planing speed so probably shed water keeping wetted surface low when reaching. So sharp chines are good.

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Tell that to John Spencer.  Infidel / Ragtime, Whispers of Wellywood and a whole generation of his chined boats were awesome performers.

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Plumb bows I can live with reverse bows just don t seem right square top mains yea more sail I'm in and Chines make me think of homebuilt fireballs or steel cruising boats and I like to go fast I just believe you should look good while doing it and while I'm sharing my preferences for style on the water the modern cruise ships look like ugly wedding cakes or lost apartment blocks give me the old Brittania QE or even the QE 2 even the titanic looked good even if it couldn't turn

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Chines often allow he designer to flatten the buttocks aft and that's good for high speed sailing where you want a flat run.

On production cruising type boats chines add volume aft where berth flats commonly are. They can also add some form stability.

But in many cases they are like spoilers of Toyota sedans.

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2 minutes ago, DDW said:

The chines on Ragtime had more to do with plywood than performance. 

That maybe but the chines didn't seem to hinder the performance any!

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3 hours ago, inboard said:

Plumb bows I can live with reverse bows just don t seem right square top mains yea more sail I'm in and Chines make me think of homebuilt fireballs or steel cruising boats and I like to go fast I just believe you should look good while doing it and while I'm sharing my preferences for style on the water the modern cruise ships look like ugly wedding cakes or lost apartment blocks give me the old Brittania QE or even the QE 2 even the titanic looked good even if it couldn't turn

You know you can buy punctuation here, it's not that expensive.

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Hmmm.....there is some fad with this with everybody and there dog doing chines and all the Bunter type of builders so it's all bull shit. How boat a real boat hmmm? My friend Mr. Bieker might have something to say about that.

 

IMG_0002.jpg

IMGP6515 (800x536).jpg

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I love that Longboard, have for a few years. Hope you are at SOAR.

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1 hour ago, Norse Horse said:

I love that Longboard, have for a few years. Hope you are at SOAR.

Longboard and Dark Star are 1/2 on the Hein Bank/Swiftsure race. It helps that there was a lot of talent on both boats but it tells you something I guess. Love the SOAR regatta. Might have been at very first one in '80. If not shorty afterwards and competed for many years. As a matter fact my crew was actually thrown out the Cheftain beer parlor. And I don't have to tell that that takes some doing. My crew did. Now the regatta is at high cruising time so haven't come back for sometime. Too bad but? It's like the Gorge in saltwater.

 

 

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Just now, duncan (the other one) said:

plywood does that to a design.

Plywood, the Carbon Fibre of its age !

Interesting to note that John Spencers few round bilge designs were largely unsuccessful performers

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57 minutes ago, Last Post said:

Plywood, the Carbon Fibre of its age !

Interesting to note that John Spencers few round bilge designs were largely unsuccessful performers

Huh. Still love the Thunderbird logo on Ragtime on the main in the '70's. T-birds and still be reckoned with in racing PHRF.

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Chines are fast, they give you extra righting moment at low angles. RM is power.  They also stiffen the hull. 

Adding chines to composite hulls has been going on for a while now. 

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So if a Destroyer, an FPB 64, an Open 60/Volvo 70 and a Bieker Riptide 55 all have plum bows, is it nothing more than maxing out waterline or are their other characteristics such as wave piercing ability that makes  the shape more than just a trickle down trend for post '08 Clorox bottle cruisers?

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2 hours ago, Panoramix said:

Chines are fast, they give you extra righting moment at low angles. RM is power.  They also stiffen the hull. 

Adding chines to composite hulls has been going on for a while now. 

They also tend to create discontinuities in the waterline plane and sectional area curves which usually leads to increased wave drag.

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53 minutes ago, 12 metre said:

They also tend to create discontinuities in the waterline plane and sectional area curves which usually leads to increased wave drag.

Yes, I think that getting it right is quite hard. During the plywood era good designers were producing much better boats. 

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Chined boats seem to have more form stability, especially as regards to rolling. Very noticeable if you've ever been on a Rothbilt unchined skiff vs. a Carolina skiff, for example. They are very popular on midsize power boats- you can see a fair amount of hard chined lobster and tuna boats. Mr. Perry is right. Only downside is that they seem to slam more going through waves.

 

It's questionable how important they are to a boat which gets the majority of its righting moment from ballast and doesn't plane, but for bigger racing boats that go fast and get a lot of RM from beam I could see the need.

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Just because some fast boats have chines, doesn't mean that chines made them fast. The question for Mr. Beiker (or whoever) is, "design a boat with no rules except to be as fast as possible on all points. Will that boat have chines?"

I think it more likely that chines might make a boat faster that is constrained by rules, cost, crew weight, accommodation, styling, marketing, or other. 

The primary reason we see them on cruiser racers is they contribute to sales. History has proven that the yacht buying masses are slavish to style, and style is set by elite racers even though the solutions applied there may be irrelevant in other contexts. 

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1 hour ago, DDW said:

Just because some fast boats have chines, doesn't mean that chines made them fast. The question for Mr. Beiker (or whoever) is, "design a boat with no rules except to be as fast as possible on all points. Will that boat have chines?"

I think it more likely that chines might make a boat faster that is constrained by rules, cost, crew weight, accommodation, styling, marketing, or other. 

The primary reason we see them on cruiser racers is they contribute to sales. History has proven that the yacht buying masses are slavish to style, and style is set by elite racers even though the solutions applied there may be irrelevant in other contexts. 

Something like the Bieker Riptide 55 was designed only to the owner's rule, to go fast. It had chines. Designed some 15 or so years ago (maybe more). It would be interesting to know what some of the other 'constraints' are that led to the hull shape (it had water ballast), or if their are further 'performance' considerations that led to the hull shape. (It also had that trendy plum bow thingy).

That said, your point is well taken, that the trickle down to cruisers may be irrelevant in terms of performance gain.

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Bieker cut his teeth in the I-14 class and you can see some of that heritage in the chined hull form of the Riptide series. There is a speed at which chines get some water release and reduce wetted surface but as boats get bigger that speed goes up. Case in point compare the Laser with the Force Five hull form.

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2 hours ago, DDW said:

Just because some fast boats have chines, doesn't mean that chines made them fast. The question for Mr. Beiker (or whoever) is, "design a boat with no rules except to be as fast as possible on all points. Will that boat have chines?"

I think it more likely that chines might make a boat faster that is constrained by rules, cost, crew weight, accommodation, styling, marketing, or other. 

The primary reason we see them on cruiser racers is they contribute to sales. History has proven that the yacht buying masses are slavish to style, and style is set by elite racers even though the solutions applied there may be irrelevant in other contexts. 

he did that already and you can see the result in the lagoon at Oracle HQ....

 

So, you need to add at least one rule - monohull....  

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Need to differentiate between underwater and above water chines.

Hard bilges accomplish the same things as underwater chines although to a slightly lesser degree, but without the additional wave drag issues.  The main advantage of underwater chines is to facilitate plywood construction.

Above water chines can increase heeled RM by allowing the Centre of Buoyancy to shift more outboard.  But with the heel comes additional wetted surface and a greater degree of immersed assymetry.  They can help promote planing - mainly by flattening out the aft buttock lines.

In summary, there are few absolutes in sailboat design - almost everything involves trade offs in one form or another.   In my view, this is the beauty of sailboat design.

 

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Chines are for sailing on and reduce wetted surface.

4_efcc2c9711.jpeg

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Chines predate plywood...Star, Fish, Seabird Yawl, Snipe. Simpler and easier construction...cheaper boat. If the chines are immersed when boat is upright, they have no effect on stability. Chines are faster on planing boats, when planing. Chines on FG cruising boats are a styling fad.

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And this is a little off topic but I thought I'd share this with the rest of class.

Paul the always the innovator without getting stupid about it as this the rudder/shaft arrangement I shot yesterday on Longboard:

 

20170618_142321 (600x800).jpg

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Chines can make for simpler construction if the surfaces can be simplified into single curvature or planar.  If properly designed, chines can allow for clean release of the flow below the chine at higher/planing speeds.  But, on sailboats operating at multiple heel angles, the designer needs to be very careful of the shape of the chine, otherwise it will be more drag if the chine dips below the water surface.  

As always, trade offs...

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Nice for a racing boat. Has the makings of a maintainence nightmare. A saildrive is pretty low drag, much cheaper, and very low maintainence. Windward Passage had a retractable prop when launched. IDK if they retained it over the years....likely not.

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3 hours ago, 12 metre said:

Above water chines can increase heeled RM by allowing the Centre of Buoyancy to shift more outboard.

 

That is only true if there is a beam constraint. I hard bilge turn, outside of where the chine would have been, has more righting moment still. If the designed max heal places the chine right at the waterline, then some laminate might be saved. But then the chine is going to have to have a very funny shape (reverse sheer with a wiggle at the bow wave?).

In the racing crowd, either there is a beam constraint and the chine allows the hull to act like it is wider that it would otherwise (which I think is your point), or the usage profile has a very high percentage of downwind planing, or the designer/owner thought it looked cool. 

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22 minutes ago, Connor.kainalu said:

I heard a rumour about the rs aero's chines "digging in and preventing leeway" any truth in that?

Possibly - to a small degree.  But the term "digging in"  sounds a lot like increasing drag and marketing hype to me.

Concept was used to decent effect many years ago on the Hobie 14 - but much more efficiently - and was the only element for side force (other than of course the rudder(s).

H14.jpg

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1 hour ago, Connor.kainalu said:

I heard a rumour about the rs aero's chines "digging in and preventing leeway" any truth in that?

 

Carve a ww kayak like a Necky Jive in and out of an eddy and you get an appreciation for how much power a chine can have.

Now try the same eddy moves in an Eskimo Topolino or old slalom boat with no chines. Make SURE you paddle is in the water bracing.;)

 

 

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2 hours ago, Connor.kainalu said:

I heard a rumour about the rs aero's chines "digging in and preventing leeway" any truth in that?

'Preventing' is a gross exaggeration. A slight reduction of leeway is more accurate, but it's a very inefficient way of doing so.

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12 minutes ago, RKoch said:

'Preventing' is a gross exaggeration. A slight reduction of leeway is more accurate, but it's a very inefficient way of doing so.

Situation: international 14: sometimes, if the reach mark is tight or we've over stood with the kite up, we'll "ride the chine" in a slow, controlled fashion. If you bleed off speed, by heeling, oversheeting the kite a bit and otherwise going slow you can get to a mark faster than going fast, dousing, and re-housting after the gybe.

That has fuck-all to do with cruisers. I like chines on cruisers. Fat ass, lots of volume inside.

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9 hours ago, Maxx Baqustae said:

Then there is the Riptide 50 "Strum" (had the pleasure to race on that too) with no chine. 

Strum2.jpg

Strum3.jpg

But she has never really shown true legs racing. Rates faster than a Tp52, but I don't think she could beat any of them.  Very roundshaped design vs the 35.  

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16 minutes ago, Irish River said:

But she has never really shown true legs racing. Rates faster than a Tp52, but I don't think she could beat any of them.  Very roundshaped design vs the 35.  

I hear you Irish but I don’t think it was supposed a full on world beater. I believe the agenda/design folio was not for that. I really don't know. I was just along for a kewl sailboat ride. 

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'Ride the Chine' 

and

'Digging in to prevent leeway.'

both make sense depending on what point of sail.

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On 2017-06-19 at 9:39 AM, fufkin said:

Something like the Bieker Riptide 55 was designed only to the owner's rule, to go fast. It had chines. Designed some 15 or so years ago (maybe more). It would be interesting to know what some of the other 'constraints' are that led to the hull shape (it had water ballast), or if their are further 'performance' considerations that led to the hull shape. (It also had that trendy plum bow thingy).

That said, your point is well taken, that the trickle down to cruisers may be irrelevant in terms of performance gain.

On 2017-06-19 at 1:23 PM, RKoch said:

Nice for a racing boat. Has the makings of a maintainence nightmare. A saildrive is pretty low drag, much cheaper, and very low maintainence. Windward Passage had a retractable prop when launched. IDK if they retained it over the years....likely not.

Virtually no maintenance at all - service universal joint every 3 years.  The retracting drive unit is so simple and under power pushes Longboard over 8 knots into any seaway - we have to throttle back as prop will launch boat over waves - unlike a saildrive.  When retracted - no turbulence or vibrations when planing downwind.  It's a beautiful piece of Bieker engineering. 

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On 19/06/2017 at 9:45 PM, RKoch said:

... If the chines are immersed when boat is upright, they have no effect on stability...

That's wrong, as the windward chine gets out of the water, it has a massive effect as the centre of buoyancy goes to leeward quickly.

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1 hour ago, Panoramix said:

That's wrong, as the windward chine gets out of the water, it has a massive effect as the centre of buoyancy goes to leeward quickly.

Assuming the windward chine clears the water when heeled, which usually isn't the case.

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you can also look at the design evolution of the later monohull America's Cup boats.  The turn of the bilge became more and more pronounced.  Not a chine I agree, but indicative of the design direction to get the stability out there faster and use a little of the hull shape for lift.  Seemed to make a difference.

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4 hours ago, RKoch said:

Assuming the windward chine clears the water when heeled, which usually isn't the case.

Really?

Chined boats I have sailed with immersed chines that come out when heeled...

nationnal-caravelle.jpg

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I actually would be curious to see photos of boat with chines that never come out.

 

 

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26 minutes ago, Panoramix said:

Really?

Chined boats I have sailed with immersed chines that come out when heeled...

nationnal-caravelle.jpg

5f4aa260ce5aa4089208740aecc3daeb.jpg

I actually would be curious to see photos of boat with chines that never come out.

 

 

I've sailed a lot of chined dinghies and keelboats....Optimists, Penguins, Moths, Sunfish, Snipes, Lightnings, Stars, etc.  Only the Sunfish and Lightning are faster with the weather chine out of the water. They are pretty flat-bottomed, and the sunfish chine barely touches the water when upright. Stars would be faster upright, but are easily overpowered, that's why the crews are so big and weight limited. The chined  IOR boats I've sailed (3 miniton designs and a 3/4 ton) had the upper chine clear of water at rest and it was slow to heel enough to immerse it. The lower chines never came out of the water. Both of your pictures the boats are sailing slow with way too much heel, and would be faster sailed flatter, particularly the dinghy.

Med_Snipe%20sailing%20action1.jpg

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In the ongoing IOM design race, chines became all the rage about 7 or so years ago. Chines are still prominent in most modern designs, although there's been at least one new design by a known boat designer without them. There's a lot of talk about hull-induced lift, but I personally don't buy it. A standard IOM foil package is extremely efficient and any extra lift from the hull would probably be insignificant by comparison. I personally believe that the real benefit to the chine on a one-meter long boat is to add rigidity, which allows for the use of thinner fiberglass. Although IOMs have a minimum weight, any weight that can be taken out of the hull and added to the corrector weights in the center of the boat will only improve performance.

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4 minutes ago, RKoch said:

 Both of your pictures the boats are sailing slow and would be faster sailed flatter, particularly the dinghy.

The dinghy is not sailed flat enough but even when sailed at its best, the windward chine is out of the water. Optimum heel is when the chine is a few centimetres above the water. It is the same for the muscadet, here are a few racing at the correct heel angle.

30990-917f37.jpg

Anyway, it's not true that immersed chines have no effect on stability, as soon as they come out they do have a noticeable effect.

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Chines on racing boats have become quite subtle and do not stop at the topsides deck location. If you observe the stern and especially the transom, you will notice if you look carefully, the flat at the centerline, the slight rise around the 1/4 beam followed by a quicker elevation to the transition topsides to deck. On this drawing, I have used more roundness at that point, before going vertical.

 

173CHtransom-JE29-17.jpg

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On ‎6‎/‎28‎/‎2017 at 6:54 PM, Panoramix said:

The dinghy is not sailed flat enough but even when sailed at its best, the windward chine is out of the water. Optimum heel is when the chine is a few centimetres above the water. It is the same for the muscadet, here are a few racing at the correct heel angle.

30990-917f37.jpg

Anyway, it's not true that immersed chines have no effect on stability, as soon as they come out they do have a noticeable effect.

 

National Muscadet?

 

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On 6/18/2017 at 2:01 PM, Maxx Baqustae said:

Longboard and Dark Star are 1/2 on the Hein Bank/Swiftsure race. It helps that there was a lot of talent on both boats but it tells you something I guess. Love the SOAR regatta. Might have been at very first one in '80. If not shorty afterwards and competed for many years. As a matter fact my crew was actually thrown out the Cheftain beer parlor. And I don't have to tell that that takes some doing. My crew did. Now the regatta is at high cruising time so haven't come back for sometime. Too bad but? It's like the Gorge in saltwater.

 

 

Small correction.  They were 1 & 2 in Division 1.  White Cloud won overall out of Division 2.  

I bet they wish they had a chine too!

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15 minutes ago, Go Left said:

Small correction.  They were 1 & 2 in Division 1.  White Cloud won overall out of Division 2.  

I bet they wish they had a chine too!

Yes, that's what I meant actually. Great job on the OA my friend!

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33 minutes ago, Maxx Baqustae said:

Yes, that's what I meant actually. Great job on the OA my friend!

Blind squirrel finds acorn.  You know how it goes.

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To quote Tokyo trash baby " just send it , and sail her under it!" Works for most sail powered boats....lol

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I think the chines add stability and help tracking to windward and allow for the wide beam 9' to keep this boat stable planing off the wind at 25knots with weight well aft. With the dreadnaught bow this 28r needs a lot of beam to ride through wave action which it can do without hobby horsing...the soft chine is better seen from the stern...

IMG_4643.JPG

IMG_4644.JPG

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