Full Displacement or Semi Displacement

[psneeld]

Originally Posted by manyboats

Psneeld,
I saw that but didn't study it closely. Should have. Yes that's what I remember from reading books about NA and related subjects. I see displacement hulls go only up to 1.4 don't know w ....... Now I see that chart is for large ships.
I see the upper chart w different numbers. All of this is general and applies to some hulls more so than others and that is the way this whole matter is looked at by most that know and by others that follow like all of us. I wonder why SD was called the "transition zone"? Good description for people like Skidgear that tend to think in the planing mode.

Skid,
How did you measure the BL in the photo? I can't even see most of the bottom. But if the BL alongside or at the keel is in fact 8 degrees then the QBBL will be 4 degrees unless the bottom is concave aft. In that case the QBBL would be more like 2 or 3 degrees. If the hull is convex (or arched as many say) the QBBL would be or could be more than 4 degrees but as I say I can't even see the underside of the hull aft.

By my way of thinking this is not a FD hull for another reason. There are flattish portions of the bottom aft that are placed there to control the tendency to squat and go bow high. Those are not features of a FD hull and since it has these features (much like the Spanish boat w the big flat plane added to it's stern for the same reason. The original FD fishing boat was 100% FD but in my opinion became something else w the attachments (hull modifications).

I am definitely not presenting any of the above in the interest of obtaining followers or believers. It's just my opinion.

Panels I think I mentioned that negative aspect of the FD hull. And being sunk by a stern wave in a second or two could indeed be a surprise.

Study it again I guess....

You musta missed the part of the graph that deals with speedboats, motorboats, fast motor boats, cigarrete boats, fast work boats, fast pilot boats, etc...etc... not just large ships....

Plus the lines on a graph are usually averages of some arbitrary definition "line"...not absolutes...data (real vessels) fall on either side exhibiting and favoring characteristics of above and below the lines....

[RickB]

Originally Posted by manyboats

Psneeld,
I saw that but didn't study it closely. Should have. Yes that's what I remember from reading books about NA and related subjects. I see displacement hulls go only up to 1.4 don't know w ....... Now I see that chart is for large ships.

Did those books say anything about why towing tanks exist?

If measuring one particular feature by viewing a photograph was adequate to define a hull and project its performance, the work of Mr. Froude and the generations of NAs that followed would have been of less value than politicians.

Size doesn't matter, it is disingenuous to dismiss facts that don't conform to your preconceptions because the examples provided are "big ships."

Big ship hulls are tested the same way as yacht hulls (at least yacht hull designs for people who are willing to pay what it costs to perform tank testing) and military vessels of all sizes.

The thread isn't going "downhill," it is just that more participants are finally seeing that many of the concepts which fuel it are as flawed as most of the preconceptions that started it.

[Nomad Willy]

Haha I knew you'd say "size doesn't matter" but I didn't change my text. They do test the same way in the tanks but there is then Reynolds Number and other variables that can't be controlled or otherwise accommodated. But it's not the same in many ways. Would the molecular dynamics be the same on a 2' model and a 700'ship. I suspect not.

Psneeld .. I missed something? Been there done that.

My motive in all this was do listen to others (in the beginning) and then try to (once again) express my understanding of the matter as it seemed many were having trouble understanding the dynamics of the QBBL in the stern and the general dynamics of water flow coming out from under the stern.

You three guys are more interested in winning a debate than having an educational experience. There's probably almost no one left reading it now. And by repeating myself I'll admit to some of the blame too. It has gone down hill in that it's been reduced to you guys throwing tomatoes at me and me ducking and probably worse. I took you guys off the ignore list to see how it would go .... and I saw how it went. Would you guys be interested in going from destructive to constructive?

[psneeld]

Like showing people how QBBL is just part of the design process and not a defining feature?????

as shown by many who HAVE TRIED to make it a learning process????

sure....

[RickB]

Originally Posted by manyboats

They do test the same way in the tanks but there is then Reynolds Number and other variables that can't be controlled or otherwise accommodated. But it's not the same in many ways. Would the molecular dynamics be the same on a 2' model and a 700'ship. I suspect not.

Thanks for confirming my statements about flawed concepts invalidating whatever point you have been trying to make ad nauseum.

I suggest you hit the books for a bit longer and find out how towing tank data is used. The correlation between models and full scale vessels of any size has been used quite profitably for more than a century.

"When a model and its prototype are geometrically similar and their two dimensionless coefficients (Re, Fr) are the same, their resistance coefficients (Ct) should be the same."

[Nomad Willy]

I'm taking the ignore option.

Bye

[RickB]

Originally Posted by manyboats

Would you guys be interested in going from destructive to constructive?

Sure, read up on hull design, Froude, and Reynolds and towing tank testing and get back to us.

I'm taking the ignore option. Bye

[Art]

Originally Posted by manyboats

I'm taking the ignore option.

Bye

Yo, Eric

Please don't let your panties get into too much of a wad! Now, you might not look at this the same way I do... but... Personally, I don't place ignore-feature onto anybody... even though there are a few who I feel are s-disturbers or even dummies that occasionally post on TF. My reasoning... even the lowest of life have some items that not only make sense but that are at times actually interestingly correct. With ignore affixed to their asssses - I just might miss that single pearl of wisdom they at some time may provide!

Important factor here (in this instance) is that both you and RickB are truly a couple of darn sharp intelligences. I know, I know... you are a really nice guy who seldom harshly confronts other contributor's input, and, Rick has a typing finger that lashes out and stings sometimes toward you and/or others, even me too... but so what??!!! To be in most any game of life we need to have thick skins and wear our helmets/shoulder pads while providing input and hoping for agreement by others, but still realizing that stern, even disconcerting rebuttals may be thrown at us from more than one direction.

If you’ll recall... Marin and I were not best of compatriots during many posts concerning our conflicting thoughts, and we’d at times get into a wordsmith shooting match with smoking guns and bullet holes in both bodies. But occasionally he and I would agree and I believe learn at least something from one another. It seemed that in most ways you and he were pretty close. At any rate... I feel that Marin and my conflicting TF relationship carries at very least a glimmer of similarity to yours and RickB’s relationship on TF. That said – I will read and look forward to continue learning from you both! Hopeing that you both can continue TF interaction.

Rick – If I may suggest – Please try to not have your words/messages/cartoons beat some people to a pulp... to me your lashes are just another ho-hum day at BOD meeting. To others you can be crushing!

Come on guys - - > I ask you to make up! Don’t bother kissing (yuck!)... but, at least let us hear a high five that communications can continue!

Now, you can both go back to the stools in your corners for a little R&R before your next bout! - LOL

Happy Boating Daze! - Art

[Nomad Willy]

Art you can bring a smile to my face no matter where we are. Don't ever loose that ability.

Most of the time we don't need these guys for their knowledge. We're mostly here for the fun of it anyway and these guys dislike me so much it's anything but fun. I had psneeld on ignore for many months and decided I wanted to hear what he had to say again ..... But it's just not worth it

Your post was a pleasant shock and .. If there's such a thing as a pleasant shock .. I appreciate you and what you say. Thank you Art.

But no .. I'm going to keep them in their rabbit holes, doghouses or wherever they go.

[Art]

Originally Posted by manyboats

Art you can bring a smile to my face no matter where we are. Don't ever loose that ability.

Most of the time we don't need these guys for their knowledge. We're mostly here for the fun of it anyway and these guys dislike me so much it's anything but fun. I had psneeld on ignore for many months and decided I wanted to hear what he had to say again ..... But it's just not worth it

Your post was a pleasant shock and .. If there's such a thing as a pleasant shock .. I appreciate you and what you say. Thank you Art.

But no .. I'm going to keep them in their rabbit holes, doghouses or wherever they go.

OK, OK!! I Give Up - Sorta!

[RickB]

There are no "personalities' involved in this discussion, just reality vs imagination. As far as the cartoon goes, it illustrates what ignoring input does for one and the discussion. It is a shame that it takes a cartoon to get that point across. I seriously doubt that post is or was "ignored" in any event. If it was then once again my point is proven.


Personally, I could care less what fantasies Eric chooses to hold with regard to hydrodynamics and hull design. I chose not to join the angels dancing on that pinhead but the silliness finally overcame my hesitation to try to leaven the rise of absurdity that was beginning to run amuck - again.

Why should I pull any punches with regard to illustrating a point that is patently false or when responding to something like the Swaggart ploy? There is nothing rude or vulgar in my posts - or the ones previous that were removed by person or persons unknown for reasons we can only guess. Nothing I have written violates any rule of this forum as much as some of it may disturb one of the moderators.

Eric is an adult, he doesn't need me or the moderators to shield him from the world or from opposing ideas. If he chooses to "ignore" posts that is his choice alone, I am not responsible for his decisions or his actions. I didn't think that was the purpose of this forum when I joined and I don't believe it should be allowed to become a mutual admiration society for the partially informed or hopelessly thin-skinned either.

[markpierce]

Life is better on forums when one doesn't repeatedly attempt to convince everyone they're not wrong on a particular issue.