so many nice paddles
as a long time canoeist of many years, all i know is that you can buy a very fine paddle or 3 for a few hundred dollars and do amazing things with them in a canoe. just stunning tools of incredible passion and workmanship. really, all the rest is purely academic.
yes
well, yes I have been a pic, have passed faa exams and I have also authored several FAA documents.
That’s fine with me…
…because I did my best to NOT focus on wings or airplanes, but to steer thought toward a “bent shape” that simply pushes sideways against a fluid medium, as is done by a paddle. I first got into this as a way of pointing out why pilot’s initial idea that there was no perceivable similarity between airplane wings and canoe paddles actually had a reason behind it, and that reason could be explained if one didn’t try to compare aerodynamic lift with a direct force. It was only after my second response that someone reminded me that he was the guy who insisted that a heavy Royalex canoe floats noticeably higher in the water and rides over waves better than a lightweight composite one “because Royalex itself is a buoyant material”. In that case, every time I tried to explain that anything that makes a boat heavier also makes it displace more water, he insisted I was wrong, so if I had remembered one day sooner how tenaciously he clung to an indefensible reason for buoyancy while deliberately ignoring every illustration I provided of the two simple factors that come into play in Archimedes Principle, I’d have never entered this discussion in the first place.
gbg …
– Last Updated: May-21-11 12:49 AM EST –
....... you can "do your best" all you want to offer explanations and theory about a paddle , it's shape , a geometric dihedral angle and/or lack thereof , applied forces and all that , it's ok by me , I don't care .
Other than my original mention of my "unsuccessfull" effort to see if I could find an association or relationship between the airplane wings w/dihedral and the paddle shape w/dihedral ... I never had "anything more" to say about paddles myself , nor "said" or "ask" anything more about them .
I simply answered the question you ask me about an airplane and sideslip .
You the "one" been doing all the brain talking . Even more , you been directing your brain talking towards me as if I had ask you something .
I never ask you a thing .
I did tell you that you shouldn't be attempting to brain talk to me in an instructional manner about airplanes and flight characteristics cause you haven't a competent enough understanding of it to do so .
About the canoe thing and the bouyancy discussion we had prior .
I said the full floation core in Old Town Expedition 169 of mine aided greatly in it's bouyancy and helped it to float higher in the water ...... then you proceeded to brain talk on and on about bouyancy and repeatly tell me how I did not understand bouyancy , how I didn't know what I was talking about .
When I felt you were finished with all you had to say ... I asked you how does all that you just said reason out when you ship water into my hull , does that full floatation core aid greatly in it's bouyancy and help it to float higher then ?? .
Funny how you became silent and had no more to say at that point ... obviously you knew the answer would have to be ... "yes" .
And to think , you had just spent days and countless words telling me otherwise .
and …
…
Have you read John Winters on
paddle shape? If he were here I would pay attention.
I was…
I was nearly “blinded by paddle science”…
so I went paddling instead of reading anymore.
My paddle(a $65.00 Sawyer I got as boot with a canoe I bought) fluttered a little bit on occasion.
I didn’t care; the sun came out, and I just kept on paddling.
It was a great day…
BOB
I’ll try one comment on buouyancy
– Last Updated: May-21-11 11:38 PM EST –
Actually, your last post to me that I remember from that previous discussion said something to the effect that "maybe" there was something valid about what I was saying (and to review, my only point was that the amount of water displaced by a floating object always weighs the same as the object itself), but you added that that surely a buoyant hull material provides a buoyant force even when the boat is floating normally. In fact, you did that just now too (once again claiming a buoyant force in the absence of displaced water), but I'll get to that in a moment. Before it was all over I got quite a few emails from people who enjoyed my explanations (not everyone hates "brain problems") but were amazed at the logic you were willing to ignore just so you could hang on to your premise.
Anyway, just now when you said ...
"When I felt you were finished with all you had to say ... I asked you how does all that you just said reason out when you ship water into my hull , does that full flotation core aid greatly in it's buoyancy and help it to float higher then ??"
... I don't remember that as your final comment (I remember something like that about halfway through the discussion, and much of what I said addressed this exact situation if you would have understood what I wrote), but this shows once again that you do not understand buoyancy at all. I'm responding to this for a second time only to refute the idea that I'd been unable to provide an answer the first time around. This is all a repeat of what I said before and surely you will realize that right away, because there is STILL only ONE thing to say which covers everything. Water must be displaced to create a buoyant force. Your idea that buoyancy can be created by a substance that is not displacing the same water that supports it (that's the water outside the hull) is just wrong.
A "flotation core" or any other type of low-density hull material makes no difference UNTIL the boat is fully swamped, with gunwales awash and the water inside the boat being contiguous with the water outside. When still floating normally, so that the water inside the boat is not contiguous with the water outside, the extra weight of water splashed on board will have the same effect on ANY boat. In that situation, water inside the hull is just "cargo", and the effect of its weight is to push the hull more deeply into the water, exactly the same as it would if the same amount of water were carried in buckets or jugs instead of sloshing around on the floor.
If your premise were correct, a person carrying enough water for a multi-day trip could make an Old Town canoe float higher (perhaps to get through a shallow spot) simply by dumping the contents of all their drinking-water containers on the floor! If you don't buy that idea, then the only OTHER conceivable option is that a person in a composite boat would make their boat sink lower in the water if they dumped their drinking water on the floor. In actual fact, dumping out your drinking water onto the floor of your boat changes nothing, no matter what the boat is made of, and the effect is the same regardless of hull construction. The weight of cargo (water) on board is still the same after the water's been dumped on the floor, and nothing you can do to alter the shape of that water's containment vessel results in the displacement of water which is supporting the boat. THAT water - the water which supports the boat - is outside the hull, not inside. Going back to your original example, water splashed into the boat is just dead weight. It acts to weigh the boat down in the same way regardless of what the hull is made of, and regardless what shape it conforms to as a result of hull construction. Again, the part you don't get is that water carried inside the boat can't be displaced in a manner which causes the boat to be more buoyant. Only objects within the bilge water can be buoyed by displacing bilge water. A boat with water in the bilge cannot be partially floated by that same water.
To review, only after the boat becomes fully swamped so that the water inside the hull becomes contiguous with the water outside the hull does the water inside the boat contribute a buoyant force, so ONLY THEN does a low-density hull material provide a greater buoyant force than a higher-density hull material.
Andy S. once posted a question here to see if people understood buoyancy. If you can correctly answer this question then it would make no sense for you to also believe the things you have been saying. Here's the question: You are sitting in your boat, floating in a swimming pool. You have a big rock in the boat with you. You toss the rock overboard. What happens to the water level in the swimming pool? Choose one answer: The water level in the pool (A) becomes higher, (B) becomes lower, or (C) remains the same.
ADDENDUM: I believe I might understand the source of your confusion about the effect of a flotation core in your hull when a lot of water has been splashed inside. I think you are not seeing the water inside the boat and the water outside the boat as two isolated systems. I think that you believe that since the foam core would obviously float to the surface if not anchored to the floor (or if it were not an integral part of the floor), that the resulting buoyant force must also be "lifting the boat". Well, there's no such buoyant force because the core is not surrounded by the water within the boat itself, but let's pretend that's not the case just so we can attack this problem. If we do that, it's just like trying to power a sailboat by bolting a fan to the deck and aiming the airstream at the sail, or just like standing on the middle of a jump rope and pulling on the free ends to lift yourself off the ground. It does not work, and here's an example to illustrate why. Imagine that you have an aquarium full of water, sitting on a scale. The scale tells you the weight of the glass tank plus the water that it contains. Now, take a block of Styrofoam that weighs one ounce but provides two pounds of floatation when fully submerged. Place that block of Styrofoam in the tank so it floats on the water's surface, and the reading on the scale increases by one ounce. Now, tie the Styrofoam block to the floor of the aquarium, so that the block is fully submerged. If you could measure the tension in the string that holds the block to the bottom of the aquarium, that tension would equal two pounds, the same as the buoyant force provided by the submerged block. Do you really believe that the reading on the scale will now decrease by two pounds? Your premise is that it will, but it will not. The scale reading will STILL be one ounce greater than it was before you put the Styrofoam block in the tank, just like it was when the block was in the tank and floating. It makes no difference if the block is floating or fastened to the bottom of the tank and submerged, the weight of the glass tank + water + the Styrofoam block will always be the same. This is why the foam core of your canoe does not add any buoyancy to your boat when water partially fills the interior. In this example, the scale which supports the aquarium is like the water supporting your canoe, the water within the aquarium represents the water inside your boat, and the Styrofoam block tied to the floor of the aquarium represents the foam core within your hull. The water supporting the foam block is a different system, completely independent of the system which supports the aquarium itself. To make this example even more like your canoe, you could substitute the scale for a larger tank of water, in which the aquarium would be floating (this would work as long as the aquarium's sides extended a few inches higher than the water contained therein). The changes in weight recorded by the scale would instead be seen as changes in waterline depth of the floating aquarium (this works for the same reason that you can measure the gross weight of a ship simply by looking at the waterline markers that are painted on the hull), and the end result of this demonstration would be the same. You can't float a boat by displacing bilge water anymore than you can grab yourself by the belt and lift yourself off the ground.
hey , I read your whole post gbg …
– Last Updated: May-22-11 1:58 AM EST –
...... I think you're correct . Which also must mean my beliefs (we'll call them former beliefs for now) ... must have been incorrect . So the answer to my question was not obviously yes , but obviously "no" .
So help me out with this one . What if the boat rolled and there she was tilted on her side , some under water and swamped , and whatever stays above is above .
Is the full floation core being of any value at that point ??
ps., ... you irritate me sometimes , but I've always liked you anyway cause you're genuine and helpful
Okay, cool!
I thought I came up with a clearer way of explaining that particular thing this time than last time, and I’m glad it did the trick.
Now to your new question (which I’m pretty sure you know the answer to, this time):
“So help me out with this one . What if the boat rolled and there she was tilted on her side , some under water and swamped , and whatever stays above is above .
Is the full floation core being of any value at that point ??”
Yes, in THIS case the flotation core helps to support the boat, and if it were a composite boat, the air chambers would come into play for the same reason. This is just like the “fully swamped” situation I mentioned a few times, because it’s a case where the water inside the boat is “one and the same” with the water outside the boat. I know there must be a better way to describe that situation, but that’s the best I can do right now (like saying the water inside is contiguous with the water outside). Anyway, in this case, with the canoe on its side, you’ve got an irregularly shaped object that is floating by displacing water only be means of its actual material volume, rather than by means of the volume that’s created by being enclosed within the overall shape of the hull.
It’s interesting that you said this too,…
“ps., … you irritate me sometimes , but I’ve always liked you anyway cause you’re genuine and helpful”,
… because when I woke up this morning I thought of a way to illustrate the problem we were talking about by floating two identical bowls (one with Styrofoam taped to the bottom inside) in a washtub and taking photos to show how much they sink into the water that supports them when a measured amount of water was added to each of them. I already had the thought that if I posted photos of the demonstration on my Flickr page, I would explain the reason as “discussing the topic with an on-line friend”, so yeah, I probably come across as being a bit of a jerk, but but even if I get a little frustrated sometimes, it’s not because I harbor any ill will toward you. Quite the opposite is actually true.
you’re like a pair of good ol boots …
… to me gbg !!
Got alot of well earned trustworthy miles on them because they’ve been one of your favorites … see ya round the next bend , take care till then .
Dan