A Physics Problem

You must have a delicate forhead. I don't notice any bouyant pressure, but I do pull each strap snug and it leaves a good superficial forehead indentation.

Tape the ends shut, then tape pennies to it until it is neutrally buoyant.

i think taping the ends shut would result in negative buoyancy since part of the tubing is above the water surface. the part that is above the surface would not need to be displaced by the pennies and in fact already contributes negative bouyancy in the amount of its own weight(like if you verticle kick and raise your arms out of the water). you could mark the tubing at the point where it exits the water, then tape the mouthpiece end shut and add pennies until it floats with the mark at the surface. of course this will not help with the pressure created by moving through the water, especially off the walls. i also have a finis snorkle and it felt weird at first. you could try just giving it a few sessions, you might get used to it.

you could mark the tubing at the point where it exits the water, then tape the mouthpiece end shut and add pennies until it floats with the mark at the surface. Or fill the tube with ~3 cm of water before taping the end shut. i also have a finis snorkle and it felt weird at first. you could try just giving it a few sessions, you might get used to it. That's entirely too practical. That's never the correct solution to a physics problem.

Or fill the tube with ~3 cm of water before taping the end shut. That's entirely too practical. That's never the correct solution to a physics problem. true on both counts:agree: i do wonder about the 3cm though. i would be taking in a lot of water if mine were that low.

You must have a delicate forhead. Agreed. The couple times I've used a Finis snorkel I've felt like my head was in a vice. S

Thanks everyone for the input! My preliminary answer based on sjstuart’s method is . . . more than 15 pennies. That’s all I had, and it wasn’t enough to sink the snorkel with both ends taped. I didn’t try to dunk the snorkel 3 cm into the water and then tape it, because I thought the tape wouldn’t stick. Likewise, to avoid having to dry the snorkel off before taping additional pennies to it, I used a plastic baggie to hold the pennies, which I then to the attached tightly to the snorkel with hair elastics. I thought I could squeeze all the air out of the baggie and keep the pennies dry, but it became obvious that that did not work, so I held the bag underwater to zipper it shut so that no air remained in it. My plan had been to measure the number of pennies I needed to make the snorkel neutrally buoyant, then multiply that by 95 percent or so, to account for the percentage of snorkel above the water, and then round up to the next penny to account for that portion’s weight. I have obtained more pennies and will report back after my next round of experimentation. To predict how many pennies it might require, I took Arthur’s suggestion and filled my snorkel with water and measured it. I must have originally estimated the snorkel’s dimensions on the low side—it actually holds right at 7 ounces of water, or 207 mL. Wikipedia says that pennies weigh 2.5 grams each, so it would take nearly 83 pennies to neutralize the buoyancy of that much air. When the weight of the snorkel itself is factored in, it wouldn’t actually take that many pennies, but wowsers--it still sounds like it might require more than I want to duct tape to the snorkel. And Steve, it is entirely possible that I have a delicate forehead! I have seen entire teams of age-groupers using these contraptions with neither complaint nor snorkel adaptation (or forehead injury, as far as I know). Maybe I should just accept that the snorkel pushes the head up slightly (thereby giving me more than 3 cm clearance for taking on water, which seems a very small margin of error to me, too, now that I think about it), and rest my head on it like a pillow rather than worrying about pushing it back down. Or—aha—maybe I should just pad the snorkel headpiece so it actually becomes more like a pillow, and bothers my forehead less. My plan right now: tape a dozen pennies to the snorkel to weight it a bit and see how that feels, experiment with more pennies in the baggie to see how many it actually takes to make the snorkel neutrally buoyant (because now I’m curious), and brainstorm what I could use to pad the piece that sits on my forehead.

Based on the numbers you gave, it looks like the snorkel displaces around 156mL of water: www.google.ca/search 156mL of water weighs 156 grams or 5.5 ounces. The easiest way to see how much water the snorkel actually displaces would be to fill the snorkel with water and then measure the volume of water.

Once you get the proper weight determined, maybe a lead fishing weight would provide you with a lower profile solution. Or tungsten is 1.7 times heavier than lead. For padding you might try a segment of foam mouse pad, or old wetsuit, adhered with silicone. Good luck with your snorkel experiment and swimming!

The problem seems to be that the strap only contacts my forehead at one point, right in the middle where the two semi-rigid sections of the strap almost meet. These pieces are curved, but the curvature doesn't match that of my head, so the rest of these sections of strap don't make contact with my forehead. You can easily modify the shape with a hair dryer and a little bending. Then you may no longer need the counter weight (keep the tape on though). I had to reshape the tube this way because the tip would point forward and submerse with a neutral head position