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Episode 77: Birds in a Truck, Bifurcated boat

  • Birds in a Truck: If birds in a truck fly, does the truck get lighter? busted
  • Bifurcating a boat at 25mph: busted

The Birds in a Truck myth tried to go against Newton's Third Law with predictable results and was mostly notable for Adam and Jamie's failed attempts to capture pigeons. The Bifurcated Boat myth was another opportunity for the build team to crash large objects into one another over at Alameda. The Birds on a Truck myth was credited to the fan site while the boat myth was based on an Internet photo and story.

Birds in a Truck

Myth: If birds in a truck fly, does the truck get lighter?

Story: A guy is travelling behind a big truck. Everytime the truck comes up to a bridge, the driver gets out, bangs on the side of the truck, and then proceeds to drive across. He asks the driver at a gas station why he was doing this -- the driver explained that he was over the weight limit for most of the bridges, so he was banging to make the birds fly and make the truck lighter.

Newton's 3rd Law of Motion: For every action, there is an equal and opposite reaction.

Small-scale test

Adam and Jamie did their best to catch pigeons with bread and seeds, but they ended up getting two pidgeons delivered instead.

Bird Chamber 1: Adam's first bird flying chamber was a tall clear chamber with a piece of mesh on the floor that Adam could vibrate to make the birds fly. The entire chamber was set on top of a scale to measure the weight difference when the birds fly. The vibrating mesh wasn't enough encouragement to keep the birds in the air, which lead to Bird Chamber 2.

Bird Chamber 2: Jamie replaced Adam's vibrating mesh floor with a rotating weed-whacker-like foam tube (not strong enough to hurt). Adam also built the camber much larger so that the birds would have more room to fly. They still had no luck keeping "Jackson" the pidgeon airborne.

R/C Helicopter test

Adam and Jamie were having enough trouble with the bird that they decided to use a R/C helicopter instead. They had their decision to switch to a helicopter validated by Ilkka Koskelo (Physicist, SFSU), who explained that both birds and helicopters are using the same physical principles to fly (i.e. Newton's 3rd Law).

Adam bult a new rig that allowed the helicopter to lift-off but also attached it to a set of poles to keep it centered. The scale on the rig showed 52.6 regardless of whether or not the helicopter was flying on or the ground.

Full-scale test

Setup: * Small trailer rigged with a two larger versions of Jamie's rotating foam tubes * Load cells positioned at each corner to measure the shifting trailer weight * 11lbs of pigeons. Catching the more pigeons was a mini-segment. First, Jamie tried to use Jackson and bird seed as a lure for more pigeons but had little luck. They upgraded to a pnuematic "web shooter". The shooter fired six tennis balls that were tethered to a net. They had little luck with the web shooter as the pigeons flew away long before the net reached them. Adam and Jamie finally gave up and called the pigeon wrangler to deliver more birds.

Most of the birds stayed in the air as they released them. The measurements from the load cell had a little bit of noise but the conclusion was clear: the flying birds did not make the trailer lighter.

Helicopter test: M5 employee Chris was brought in to fly a large model R/C helicopter inside the trailer. The first helicopter myth didn't go well -- the helicopter blades hit the side of the trailer and broke. Chris retrieved another R/C helicopter and on the second test they got the result they wanted: no difference in the weight of the trailer as the helicopter took off.

busted (Newton's Third Law is upheld)

Bifurcated Boat

Myth: If a boat travelling at 25 mph crashes into a channel marker, will it split in two?

Story: This myth is based off a photo that shows a 17-foot gash down the center of a speed boat. The associated story claimed that the speed boat was only going 25 mph when it ran into a channel marker.

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More photos

Baltimore Sun, 9/18/2000 source

Near Bay Bridge Marina on Kent Island: Just before 2 a.m., a 1992, 38-ft. Fountain power boat slammed into a fixed, channel marker, ripping a 17-ft. gash in the forward hull & becoming impaled on the steel piling holding the channel marker. A passenger suffered a broken arm & lacerations; a passing boater rescued the two men. DNR police cited the skipper, who "claimed to have been blinded by the lights of a sailboat", for negligence, traveling at an unsafe speed, & failure to maintain a proper lookout.

Small-scale tests

Tory made a silicone mold of a small-scale boat so that they could crash multiple models while Grant built the rig to crash them. The rig pulled the boats on a cart across the floor into a small-scale pole. Grant justified the lack of water in their experiment based on the fact that the myth was based on the kinetic energy of the boat, not the water.

The small-scale tests gave them an important conclusion for their full-scale test: when the rig pulled the boat head-on into the pole, the boat would always glance off without splitting. When Tory picked up the boat and rammed it into the pole off-center with a small twist, he was able to penetrate the hull.

Full-scale test

Setup: * Mythity Split: 10,000lb speedboat (bought for $15k, sans engine). * Tow truck * Boat trailer with 'smart wheel' to aid steering. They came up with a clever mechanism that would cause the trailer to turn at the last second: a post in the ground was setup just before the marker; the post hit a small crossbar across the front of the front wheel that turned the trailer at the last second.

First run: their breakaway cable was a little too sensitive and broke as the boat was being towed. Grant blamed Tory for wanting to use a different rope than they usually use as their breakaway rope.

Second run: the boat deflected off the channel marker with no splitting of the actual hull. Their rig worked as planned and turned the boat slightly just before impact. This run busted the myth

Third run: they did their best to resurrect the bent-up trailer, cutting off two wheels and using the tow truck to bend it back into shape. At 45mph they result was similar to the second run, with more damage to the trailer this time. The boat glanced off the channel marker.

Fourth 'run': they lifted the boat up with a crane and dropped it into the ground, with predictable results. Unfortunately for the build team, the boat fell back onto the bed of the crane truck and caused some damage.

busted

Comments

As an avid boater, I think that this picture is completly real. I have hit a bouy at a much lesser speed causing a watermellon size hole in the forward hull of my boat. These boats sit deep in the water, and travel like they are on rails. Water is more dense than air obiously, and the reaction would be extremely different compared to a boat on a trailer with only air stopping it from deflecting off of the channel marker.

The mythbusters siad that the important factor was "kinetic energy". However, the other factor is "angle of attack" or "angle of deflection". The first attempt was fine, but not proof of a rule. The second hit was along the side-- in other words a purely glancing blow. There was no chance for the pole to bite into the boat.

Of course the last drop of the boat hit head on, and did damage-- even though the speed was only (assuming 2 seconds in the air, which is what I saw) was about 58 MPH.

Another nit-picky thing is that "kinetic energy" dependent upon mass. If you take out the engine, people, fuel, etc., the mass is probably less than a third of what the boat would have otherwise.

Good fun anyway! Cheers guys.
-Mark

I tend to agree with Mark L. Burkey. About two years ago I saw the result of a 22 foot whaler rampage hitting a floating bouy. These are some of the sturdiest boats manufactured. The starboard bow was crushed a full 30 inches, the center console torn loose from the floor and the transom was cracked from the inertia of the engine. The driver was a bit under the influence and suffered cuts and bruises, the passenger did not do so well. He was ejected from the boat on impact and fell in the water, his serious injury occured when the drunken captain gaffed him and pulled him back onto the sinking vessel! True story! Just off Adams Cut near Eliot Key Florida.

I agree with Trevor Lampe. A boat running through the water with a load in it would be a lot harder to deflect from an impact. Trying to prove that it cant be done by pulling a boat on a trailer and hitting a pole only proved that it cant be done by pulling a boat on a trailer and hitting a pole and the pole won't split the boat cuz it just deflects off to the side. I hate it the way they try doing something a different way and when they cant get it to work they claim it cant be done the other way too. False assumptions ain't proof.

The splitting boat myth is not a myth because it happened today in Berthierville, Qu├ębec, Canada. Here is the proof:
http://www.cyberpresse.ca/actualites/quebec-canada/justice-et-faits-divers/200908/14/01-892687-accident-de-bateau-deux-personnes-dans-un-etat-critique.php

This picture of the boat incident is very true. I know it doesn't make sense you would think that it would shoot off the marker but it didn't I seen this accident with my own two eyes, it was by the foot of the Chesapeake Bay Bridge on Kent Island, MD just outside the Bay Bridge Marina