Physics of V-Stretches

and scroll down half way to the president picture and the “Eat at Ed’s” sign examples.

Tension increases as the line approaches 180 degrees, just as Magnum said. However, what he didn’t mention is that your stretching arm has to apply more force to counter that increasing tension. If you want to stretch your dick harder, fine, but it doesn’t matter which way you pull. Whether or not you have a weight draped over your dick, 10 N of pulling force produces 10 N of tension.

The closer the line gets to horizontal, the less “share” the y component has of the tension. Since y supported by the line has to equal the weight of the picture, tension increases until y gets enough to hold the weight (or the line breaks if it isn’t strong enough). As I said though, this isn’t “free tension.” In the sign example, sturdier nails are needed for the smaller angles. Nails that would hold when the line is 60 degrees might break off at 15. When v-stretching your dick, you have to pull harder, increasing tension, to bring your dick closer to horizontal.

That’s my stab at it.

I think Nedd is just pointing out that v-stretches don’t give something for nothing.

Nedd, you’re right about the average stress - static system with equilibrium of force works well here. However, the stress distribution is the key to understand the effectiveness of V-stretch. It’s the local stress (could be several times higher than the average stress over a cross section) that causes the tissue to deform/tear. Just think about how the knife works. The sharper the knife, the higher the local stress, even the average stress remain the same.

BTW, I was trained to design something similar to aircraft for a living, even though I’m not doing that for a living :)

Yeah hobby thats my problem with magnums explanation the fact that there aren’t two fixed points.

Of course that backs up everything Nedd has been saying all along :)

I just have this terrible feeling that there’s something I’m missing, its probably not related to force arm taking the strain but buried deep in the holey bucket of knowledge there is some part I’m not happy with. Sometimes my wittle head hurts.

Oh well time to look up the effect on tensile strength of a deformed cylinder, why suspension bridges insist on looping rather than straight lines (I forget now) and structures in general I guess.

Tantrex,

>It’s the local stress (could be several times higher than the average stress over a cross section) that causes the tissue to deform/tear. Just think about how the knife works. The sharper the knife, the higher the local stress, even the average stress remain the same.<

Yes that makes a lot of sense. It doesn’t feed back to my experience of v-stretches though. I always found that working over a cylinder like a can produced the best effects. Now that could be down to it simply providing the best postioning to exert force, in which case I should try repeating it with a smaller diameter cylinder.

>BTW, I was trained to design something similar to aircraft for a living, even though I’m not doing that for a living<

Then you’ll know all about stresses that were dicovered after crashes that designers had not taken into account :)

btw what is something similar to an aircraft?

Do you know much about harmonic stresses? What interests me is whether there is some period that good be pulsed into a stretch to increase stresses. Not talking JAI here and the effects of the BC.

Well, it made my head hurt too for awhile. :)

Increased local stress makes sense. You can feel different areas getting hit when you move the V around. Divide and conquer.

Another advantage of V-stretches is being in a better position to exert force. I can lock out my elbows and lean into it. Or for reverse, lay my dick over the back of a padded chair and use bodyweight, again with a locked elbow.

Yeah locked elbow is a key and using the bodyweight or the power of the shoulder muscles.

Is 7-ups physics theory correct?

Trigger, thanks for linking a thread where I’m making the opposite point to this thread ;)

Magnum brings up the suspension bridge thing again but the problem with that analogy is always that there aren’t two fixed points, only one (the base).

Bingo.

I agree, it’s completely possible this could be a major benefit of V stretches. I only won’t go any further because I haven’t really had much experience with them, so I don’t know whether I feel increased stress in certain areas. If lots of people do, then it could be quite likely.

I think what Tantrex explains is the only benefit of v-stretching. That’s also how I interpreted the exercise, because the only place I feel something while doing v-stretches is the place where I press down my thumb or my pencil. While pressing down I let it slide from my base to where I’m holding my glans with my other hand and back till my septum is sore.

Hey Nedd, I know what your talking about. I thought about starting up this debate a while back, but I didnt feel like digging through my memory for mathematical formulas! I remember the examples in physics classes of a cloths line with weight in the middle. Of course in these examples the line is anchored at both ends and cannot move, however, in a fulcrum stretch the pulling hand can move. And the force applied to the penis is the same amount pulling with the hand. So one would have to pull that much harder with their pulling hand depending on how much they push down. How much harder depending on how obtuse the angle is. But in any situation the force on both ends of the line (or penis) is equal. Its simple to understand really.

mememto, I think I’ve already given away too much for potential peers viewing the forum :) . Anyway, a good way to experiment with harmonic stress is to use a vibrator or massager instead of thumb or pipe as a fulcrum. Warning, if you use an AC operated body massager, you might bust your veins, especially when erect!

Fair enough tantrex, I’ll just have to assume that its space craft or airships or hovercraft or … :)

Ah yes but frequency is probably vitally important, wavelength the length of the penis or a harminic or that. Amplitude is probably terribly important too. What I need it one of those things building engineers use to shake walls apart on to test (and some spare penises).

>No… if you pretend the folded over penis is one object, then pulling up there are two 10N forces, and pulling down there is the single 20N fulcrum force. This makes a 20N tension, over double the cross sectional area. That’s exactly the same as a 10N tension over the normal cross sectional area.<

OK here we go. So using that as a starting place that would mean you agree there is a 20N force. It would also mean that at the top of the loop there is a 20N force working over the single cross sectional area. So this is our local tension increase.

Clearly its impossible to have a 20N force suddenly change into a 10N force. This feeds into tantrex’s knife example. A knife cuts because it localises tension enough to force through the tissue providing tension in a pinpoint width, but even a knife cutting through skin will provide a tension gradient.

So if we have a simple 20N force over under a thumb and a 10N force at the extremities it seems reasonable to assume that the tension gradient will actually cause effect over the whole shaft. We are directly effecting tension in a fair percentage of the penis (somewhere between 10-20%), so the overall tension in the shaft should increase.

Now in terms of getting nothing for free, thats not happening because some force is being effected by the hand and some by the thumb.

So this

>Okay. Just trying to clear up the confusion. I’d suggest it feels better because you’re pulling harder.<

holds true its just that the force is not all applied by the grip hand.

Hows that ? :) Explain to me why I’m wrong.

Huh? At the joint/fulcrum, there’s a 20N force, but it’s not working over a single cross sectional area adding to the tension like the 10N forces are. This 20N force only acts at the joint, and even there it’s not creating tension. At the joint things get more complicated… I left out detailed analysis of the joint because of that. Frankly I don’t know what goes on at the joint. Like I said it’s complicated, you’d probably need sophisticated measuring equipment to know exactly what’s going on. My guess is there’d be some compressive stresses in there and maybe even some reduced overall tension.

Okay, here we go. I could very well be wrong with this, I’m just making it up as I go along, but: Imagine a cable going round a pulley. On a section of cable around that pulley area there are two tension forces tangent to each end of the arc formed by the section we selected. There is also a radial force exerted by the pulley. This would suggest that there is reduced tension and added compression; the x components of the tangential forces produce tension, and the y components of the tangential forces plus the radial force produce compression. But. Take an infinitesimal piece, and the two tangent forces are parallel. Thus the radial force must be zero, as makes sense considering the fact that there is only an infinitesimal area exposed to the stress the pulley exerts on the cable. Interesting.

So what does that mean? It means, an ideal cable making a continuous curve still has zero compressive forces acting on it and the same tension as any straight section of cable.

How about a discontinuous curve? I guess the points along the discontinuous joint have reduced tension but added compression.

The penis isn’t discontinuous though. It’s also not ideal. So really, I don’t know what exactly’s going on inside the penis. Again, you’d very probably need sophisticated measuring equipment to know.

No. The second a tension gradient exists within a cable, it snaps. Reductio ad absurdum, your reasoning is flawed. I direct you to my first post yet again. The tension in the straight section of penis on either side of the joint must be uniform. Must be. Any reasoning you come up with that shows otherwise is flawed. Even when the penis is not an ideal cable, this remains true.

I don’t know what exactly goes on around the joint, because around there the penis is no longer a simple cable. But I don’t have to know anything about the joint to know that the tension in the straight section of the penis leading up to the joint is uniform, and equal in magnitude to the force you’re pulling it with.

I tried messing around with elastics as theory and empirical experiments can vary a lot. I didnt get proper results and will try again. One method would be to get a elastic chest expander (the 2 handled excersise device you stretch apart with both hands) and hook it to the wall. Then pull as hard as you can with one hand and measure how much it can stretch. Then while still pulling, push down on it like a V stretch with you other hand and try and measure if it lenghtened any more, this may take 2 people. Or simply hang a weight in the middle and again see if it is any longer with your same stretch force. It may be better to use just 2 weights to be sure you dont alter your forces.