rodndtube.com's (OLD) MyPaipoBoards Forums. Reading but no posting on the OLD forums.

[PaipoJim]

[PaipoJim]

[RoyStewart]

Hello Paipo Jim,
You are mistaken. The foil on the outside of the pipe does not pull the board down into the water. I have built tunnels foiled on both sides and they behave in exactly the same way as one foiled on the outside only. Perhaps they should behave as you say, but they don't.
The bottom line is, that where that tunnel is pointed, that is where it goes. At even moderate surfing speeds it is almost impossible to fight against the direction of the foil if it is pointed upwards.
The annular wing is quite different from a regular wing or foil in that it operates at a zero angle of attack and as a wing it can't be accurately described as creating lift at all. Certainly a complete pipe could not create
lift due to its foil section because it has as much foil section upside down as right way up, but they fly very well.
I should also point out that the tunnel fin can be made very thin. it is only foiled for smooth water flow, so no thick chord ratio is needed, and the thinner it is, the less drag there is.
Regarding noseriding, my opinion on the subject is quite clear: Noseriding is a dysfunctional trick which will always slow you down, and looks ugly as well. Noseriding has kept longboarding in the dark ages and the assumption that everyone who steps onto a board over nine feet automatically has a burning desire to noseride is crazy The fact that people do it is simply the herd response to mass advertising. Boards designed to noseride are always horribly slow. I am into speed surfing and all my boards are designed for speed.
Nevertheless tunnels have historically been used as noseriding aids. You can do it that way if you want to by standing on the nose and fighting the foil. It works but slows you down. The tunnel resists any sideways pressure from any direction, it doesn't pull downwards, it simply has a very strong tendency to go where it is directed.
Get your weight back over the foil and flow with it, you will then go very fast indeed.
Roy

PS I have ridden thousands of waves on tunnel finned boards and they roast all opposition, in fact they leave everything else in their very efficient wake.

PPS Isn't this a Paipo Forum? We can talk longboarding over at Swaylocks, see you there!
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www.woodensurfboardbuilder.com

[RoyStewart]

Paipo Jim . . . should have said about the claims on the glider website that the annular wing toys Don't create lift, . . . that they Don't create thrust, . . .but they do have low drag.
The annular wing does not fly by creating lift, it flies because it has a flat glide ratio and a low drag coefficient.
Roy Stewart
_________________
www.woodensurfboardbuilder.com

[PaipoJim]

[PaipoJim]

[RoyStewart]

Hello Paipo Jim , thankyou very much for your opinion.
I am not contradicting myself. It is apparent that you are assuming that my statement that tunnel fins 'hold in' strongly is tantamount to saying that they pull downwards. That is not what I said. I said that they 'hold in'. What I meant by that was that they resist pressure from any direction. Once they are moving fast they strongly resist any efforts to make them translate their position laterally. That is not the same thing as saying that they 'pull downwards' which I didn't say. Once you realize this it becomes obvious that I am not contradicting myself by saying that a tunnel foiled on both sides acts in the same way as one foiled only on one side.

Regarding your assertion that I have a fundamental misconception about the way that an annular wing creates lift, please allow me to point out that I disagree on the following grounds:

1) An annular wing does not create lift, so it is no misconception to assert that it doesn't.

2) That your assertion that an annular wing creates lift in all directions is untrue, and even if it were true, the net resulting lift would be zero, so there is still zero lift.

You state that annular wings create net lift in the vertical vector by 'various means'. Annular wings do not create lift in the vertical vector, and 'various means' is not a concept which carries any weight whatsoever.


An annular wing stays aloft because of its tenacious resistance to translation across the path of its forward direction. This is why it operates at a zero angle of attack, and has a flat glide ratio.

Nice talking to you, Roy
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www.woodensurfboardbuilder.com

[RoyStewart]

hello Paipo Jim,
You are wrong when you assert that I am mistaken about whether or not a tunnel foil is acting as a directional 'skeg' or a hydrofoil. To the tunnel fin there is no difference between action as a directional skeg and action in the vertical vector. The tunnel is a water flow direction unit which acts in all lateral directions. My boards which sport only a tunnel as their fin setup act as directional skegs through 360 degrees in the lateral plane, and certainly do the job of a 'directional skeg' in the horizontal plane very well indeed.

I do most sincerely hope that you understand this point.

Regarding your rock versus glider lift comment: It is not the case that if it isn't a lift producing glider then it can't fly. The annular wing isn't a lift producing glider, but it flies due to the fact that it has a flat flat flat glide ratio. Do you hear me? Flat glide ratio, no slippage.

I am aware of the fact that full sized annular wing aircraft have flown. My experience has been with full sized annular wing surfboards and annular wing flying toys. If it makes a difference from a research point of view to sit on the aircraft, then please let me know after you've done it. I have been standing on many full sized surfboards with annular wings and do notice that this practical experience helps immensely in corroborating theoretical projections. The process has been described as scientific method.

Best wishes, Roy
_________________
www.woodensurfboardbuilder.com

[Poobah]

Okay, I think a half pipe should have net lift and behave differently than a full pipe when mounted on the bottom of a flat plywood board, but it sounds to me like Roy strikes some sort of balance by shaping/building concaves into the bottoms of his boards. Maybe Seamus will foil both inside and out to make the lift negligible. If the net lift isn't already negligible. Perhaps the scallops are a waste of time on something that doesn't spin...at least I usually try not to spiral on a paipo.


Last month I was hanging out in a friends garage and he showed me an old tunnel fin made for a water ski. It was a triangular shaped tube maybe four or five inches long. I forget what the brand name was. At the time I wondered if it would be useful at slower speeds.

Seamus, have you considered mounting a boomerang on three pylons to make a twin tunnel fin? You'd have tip drag, but you wouldn't have to worry about hitting submerged rocks.

[PaipoJim]

I assert that your semi-circular tubes produce lift that holds in the tail of a surfboard.

(See the wooden pintail board which you have on your website)

You say:

[RoyStewart]

Hello Paipo Jim,
I am sorry that you no longer wish to discuss the very interesting subject of foils with me. I am not being irrational simply because I do not agree with you about the properties of the annular wing. I have not accused you of being irrational simply just because I disagree with you. I am sure that with a little patience we could sort this matter out, but firstly I must clear up a few small points.
You say that I have produced unnecessary prototypes out of ignorance of the properties of the annular wing. This is not the case. If you look at my website you will see various tunnel finned boards including the very first prototype which I built. That first prototype is identical to the later models apart from the size of the foil and the shape of the board it is attached to. The very first annular wing foil I built worked perfectly.
Now my point here is that whilst this is a free and open discussion, it is still necessary to tread somewhat carefully when talking about other people's personal experience. You have made a mistake in assuming that because I have built many annular wing surfboards, that therefore some of them must have been failures. As I have pointed out, all of them were very successful. It is not possible for you to guess accurately about what I have done in the past, and doing so is a waste of time and reveals a hasty disposition. At least be good enough to realize that I am reporting my own experience honestly and in good faith.
You can say what you like about the laws of physics, but you can't possibly know more about my surfing and boardbuilding experiences than I do myself, so please don't try. The correct way to go is to pool our knowledge. There is no hurry, and no need to run away.

Before we get back to physics, please allow me to suggest that cutting and pasting what I have written in order to reveal supposed inconsistencies is not a very good way of conducting a discussion as it is very easy to get ideas out of context. It is far better to try to first understand what your discussion partner is saying, and then refer to those ideas in your own writing. May I ask you to please avoid this cut and paste style of argument if you are talking to me? it is in the worst tradition of warped journalism, and we are academics not cheap journalists.

Now, to return to the annular wing theory which we were discussing, I must say that I still haven't seen any convincing argument in support of the idea that an annular wing creates lift. There seems to be an underlying assumption of yours that anything which flies must create lift or it will fall out of the sky. If this is in fact what you are assuming then you are partially correct. Any object which stays aloft indefinitely has a source of lift unles it is in orbit, but we are also including gliders in the discussion. Some gliders create lift as a way of delaying their return to earth, but in still air they will nevertheless return to earth anyway. They could be described as falling out of the sky slowly.
If we can agree that an object which falls very gradually to earth (assuming still air) is in one sense gliding, then it can be stated correctly that there are many such objects existing (other than the annuar wing) which stay aloft, or glide, without generating lift. One example is the dandelion seed, which can stay aloft for a relatively long time in still air and which is definitely not a lift producer.
To sum up this argument, I have provided a case against the notion that any object capable of staying aloft for long periods must therefore create lift. Lift is used by some objects to stay aloft, but not all.

It is my contention that annular wing gliders belong to that class of object which is able to stay aloft without generating lift. Now it is quite clearly true that such a class of objects exists, as demonstrated by the example of the dandelion seed. Given that such a class of object exists, what do they have in common, and how do they stay aloft without generating lift? In particular, if my contention that the annular wing is a non lift generating object is correct, how does it stay aloft?
Firstly, the class of non lift generating airborne objects all have in common a means of slowing their passage through the air in a downwards direction. The dandelion seed achieves this by having a very small mass relative to its size, and a structure which creates a lot of drag.
The annular wing does it differently. The annular wing stays aloft by resisting slippage in any and all directions which lie at 90 degrees to its flight path, most importantly in this case it resists slippage in a downwards direction if travelling horizontally. By resisting slippage efficiently it is able to stay aloft without generating lift.
How does the annular wing prevent slippage so efficiently? Firstly, it does so because it always travels along its flight path with a zero angle of attack relative to its flight path, or tries to revert to that state whenever it can. Secondly, this attitude in flight is very low in drag, and offers little opportunity for sideways slippage. Gravitational force is thus able to be translated into forward motion very easily with the annular wing, so easily that a slight lowering of the flight path from the horizontal will convert gravitational energy into forward motion with only negligible loss of altitude. This is sufficient for the annular wing glider to remain aloft for at least as long as its cousin, the lift producing 'flat' wing glider . The situation is perhaps analagous to a very efficient skateboard rolling down a long , very slightly sloping path. No lift is necessary.

I will be back tomorrow with more explanation of the annular wing and its characteristics as a surfing tool, and will attempt to shed light upon the result of using a half pipe.

Yours Faithfully, Roy
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www.woodensurfboardbuilder.com

[RoyStewart]

Paipo Jim,
I must apologise for a slightly misleading statement which I made and to which you were referring in your posting. As you correctly pointed out, I said that annular wings produce lift. What I actually meant was that such a wing can lift upwards if and only if it is pointed upwards. My language was unfortunately too casual for complete accuracy on that occasion. If we take lift to mean (along the lines of your definition) any force at right angles to the flight path, then it can be quite clearly stated that there is no such force generated by an annular wing and that I did not mean to assert that such a force exists. It is usually the case with this kind of discussion that some refining of term is necessary to avoid misunderstanding. What I actually meant was that in a surfing situation, if I am riding a board with a six inch diameter foil, and I point it upwards, then it can easily project the the board and myself out of the water.


There is another matter to be cleared up regarding glide ratio and your assertion that any glide ratio relative to the wave face means you are pearling.
What I was actually saying was that any glide ratio below the horizontal will result in forwards motion on the wave face, and that if the path of the board then starts to diverge from the wave face then the board will start to fly.
Furthermore, although it might be sometimes true that a glide ratio relative to and below the wave face will initiate a 'pearl', it is not always the case. We must remember that we have a thing available called nose rocker! Sometimes this will save the day if we start vectoring beneath the surface!

Best wishes and thanks for a great discussion. Roy
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www.woodensurfboardbuilder.com

[RoyStewart]

Hello Poohbah,
Talking about tunnels it is clearly possible that a half tunnel can produce a force vector downwards if it is foiled only on the outside. This is in spite of the fact that a full tunnel has no net force vector in any direction. I can honestly report that any such downwards force is insignificant compared with the overwhelming tendency for the tunnel to travel directly forwards. In other words if you point it up it is going up anyway. In a surfing situation I cannot tell the difference between a tunnel foiled on both sides and one foiled only on the outside. They both work amazingly well. I wonder how Seamus is getting along with his Wing? Oh, by the way, thanks for the lead to this place.
Roy
_________________
www.woodensurfboardbuilder.com

[RoyStewart]

Hello Paipo Jim,
I am slowly getting through the points which you have raised.
Regarding Pitch, roll, and yaw, it is quite consistent for the annular wing to resist pitch and yaw and to be self correcting in that respect while still being able to turn quite easily. Roll is of course something a pure annular wing has no resistance to which is one of the reasons it is so good on a surfboard . . .there is no resistance to rail to rail movement. Roy
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[tumak]

Hi Roy,

I really like your site, as well as your spirit of independence. One of the guys I admire back here in the U.S. is Skip Frye, who's also surfing boards in the 12'-13' range. I have a 10'6" Hynson "Cojo" pintail that I truly love, partly for the history behind it, and partly for its awesome ride, but I always wish I had a 12'-13' board...though here in Florida conditions for its use would be more rare.
I like balsa as board material; you can see my "Hurricane Fighter Plane" and "Mysterious Turtle" on Poobah's wonderful lamaroo site. Big balsa boards seem to blow apart too easily when they hit the sand; this has been my experience, unfortunately. Now, I restrict my use of balsa to paipo construction.
I know nothing of the issues you raise with Paipo Jim. My knowledge of physics, foils, and "wings" is about as vast as my knowledge of Saturnian
planetary geology. I use ordinary fins (my favorite is a red 10" Greenough 4A on my Mysterious Turtle) which seem to work just fine for me, with my limited understanding.
As a Buddhist, I really dig that you keep your cool so well.
Keep up the good work, and Happy Surfing! -tumak