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32 mins ago, kinghong1970 said:

Ok, i did enjoy that video on cooler comparisons but...

 

1) inconsistency in volume of the coolers will affect the cooler performance

2) he should have done a 10 or 15 day test in the shade where they will be exposed to consistent heat

3) if under sun... maybe cooler colors should have been same? varying ambient temps left to right...

4) he needs to buy a temp probe and do a delta t vs ambient... 

 

just being a bit nerdy but the test is not "scientific"

 

4

I think its pretty accurate. People arent going to take color into consideration when they buy. As for volume, he proved that wrong with the two igloo coolers that had the same results with two different sized coolers.

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34 mins ago, Baitbucket said:

I think its pretty accurate. People arent going to take color into consideration when they buy. As for volume, he proved that wrong with the two igloo coolers that had the same results with two different sized coolers.

 

i get your point... for most people, they're not going to get scientific about it... 

but... (warning, sorry for the long read...)

 

last three years, i coach the local middle school science projects team. 

last year, one of the topic was Thermodynamics...

 

the challenge was to build a insulating box (within given volume) that will retain most heat (this is retaining heat but works same as retaining cold) in a 250mL beaker

 

we made 1/2" styrofoam box with an inner box, much like a yeti without the plastic and without the foam insert as we chose air as primary insulator (being the best insulator next to vaccuum)

 

first test was unlined styrofoam white outer box and white inner cavity,  

 

second test was black painted outer box and mylar lined inner cavity

the inner cavity was designed to hold 250mL beaker with heated water snuggly, 

we tried to eliminate as much free air in the vicinity of the beaker because one of the requirement was a 2cm hole on top for temp probes... and when you add heat source, we will have air motion due to convection and loose heat.

 

the second proved to be more efficient.

 

1) internal volume in relation to the insulating wall thickness affects thermal performance tremendously,

not talking about houses where you have active heating/cooling capacity but think of ice as your thermal block and the walls of the cooler the sole insulator

down jackets and insulated jacket comparison does not apply here... we made down jackets ranging from 450 fill power to 800 fill power down jackets and while some will say that a small guy will be equally warm in a down jacket as a size 4XL guy... but again, the body generates heat... does not apply.

 

2)color affects thermal performance tremendously,

this i know from personal experience in dubai and indonesia, i would actually put a down jacket on my lap to keep my legs cool while in car... white jacket vs any other colors...

 

columbia sports uses their "omnitech" reflective material in their lining in the winter garments...

same concept here... it reflects heat, whereas dark colors retain heat.

 

much like how a radiometer works...

 

3) ever notice how fast a surface warms up in the sun? look at his test... the coolers on the right vs the coolers on the left... right ones in sun, left ones in shade...

that built up heat will conduct to the inner wall because you have solid mass (exterior HDPE) then the foam despite being "like air" it is a conductor and only reason it has to be used is because it will keep cooler's structural rigidity... then conducts to the inner wall which will aid in ice melting.  hence he should have done this indoors where all cooler is exposed to same amount of external energy... 

 

anyways, yea, it's geeky and nerdy... but in his test, there are many flaws to equally compare the thermal performance across the board...

but your point is valid... cost of buying more ice in comparison to cost of buying an expensive cooler...

 

but you also have to consider... why drive a porsche/ferrari/aston martin when a toyota yaris gets you from point a to point b?

i think they're tapping into the type of customers who will spend the cash...

 

hahaha... sorry for the wall of text there...

 

enjoy!

 

Al

Yellow Eyed Devils
There's no Sense in Nonsense!

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43 mins ago, kinghong1970 said:

 

i think they're tapping into the type of customers who will spend the cash...

 

This is what I think hobie is doing, the original point I was trying to make by bringing up yeti.

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1 hour ago, kinghong1970 said:

 

i get your point... for most people, they're not going to get scientific about it... 

but... (warning, sorry for the long read...)

 

last three years, i coach the local middle school science projects team. 

last year, one of the topic was Thermodynamics...

 

the challenge was to build a insulating box (within given volume) that will retain most heat (this is retaining heat but works same as retaining cold) in a 250mL beaker

 

we made 1/2" styrofoam box with an inner box, much like a yeti without the plastic and without the foam insert as we chose air as primary insulator (being the best insulator next to vaccuum)

 

first test was unlined styrofoam white outer box and white inner cavity,  

 

second test was black painted outer box and mylar lined inner cavity

the inner cavity was designed to hold 250mL beaker with heated water snuggly, 

we tried to eliminate as much free air in the vicinity of the beaker because one of the requirement was a 2cm hole on top for temp probes... and when you add heat source, we will have air motion due to convection and loose heat.

 

the second proved to be more efficient.

 

1) internal volume in relation to the insulating wall thickness affects thermal performance tremendously,

not talking about houses where you have active heating/cooling capacity but think of ice as your thermal block and the walls of the cooler the sole insulator

down jackets and insulated jacket comparison does not apply here... we made down jackets ranging from 450 fill power to 800 fill power down jackets and while some will say that a small guy will be equally warm in a down jacket as a size 4XL guy... but again, the body generates heat... does not apply.

 

2)color affects thermal performance tremendously,

this i know from personal experience in dubai and indonesia, i would actually put a down jacket on my lap to keep my legs cool while in car... white jacket vs any other colors...

 

columbia sports uses their "omnitech" reflective material in their lining in the winter garments...

same concept here... it reflects heat, whereas dark colors retain heat.

 

much like how a radiometer works...

 

3) ever notice how fast a surface warms up in the sun? look at his test... the coolers on the right vs the coolers on the left... right ones in sun, left ones in shade...

that built up heat will conduct to the inner wall because you have solid mass (exterior HDPE) then the foam despite being "like air" it is a conductor and only reason it has to be used is because it will keep cooler's structural rigidity... then conducts to the inner wall which will aid in ice melting.  hence he should have done this indoors where all cooler is exposed to same amount of external energy... 

 

anyways, yea, it's geeky and nerdy... but in his test, there are many flaws to equally compare the thermal performance across the board...

but your point is valid... cost of buying more ice in comparison to cost of buying an expensive cooler...

 

but you also have to consider... why drive a porsche/ferrari/aston martin when a toyota yaris gets you from point a to point b?

i think they're tapping into the type of customers who will spend the cash...

 

hahaha... sorry for the wall of text there...

 

enjoy!

 

Al

I’ll just add some more geek stuff to the thermodynamics

 

There are 3 forms of heat transfer:

 

Conductive – physical contact between two things

Convective – fluid movement (fluid being a gas, liquid or plasma)

Radiant – think infrared radiation

 

In practice, these things work together. While you are correct, that air is a great insulator with vacuum only being better, that relative to only the Conductive mode.  The reason foam or other materials are used isn’t just because of structural reasons, it’s to reduce convective heat transfer.  If there were just a big air gap instead of foam in  a cooler, you would get air currents transferring heat from one wall to the other and consequently it would perform very poorly.  In the “perfect insulation” the air cells would be closed, so air couldn’t  move between cells and the cell size would be below a theoretical threshold where air can’t move (has something to do with molecular interaction at a nano scale) and the cell walls would be one molecule thick.  This doesn’t really exist but it pushed the theory to the limits.  

 

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47 mins ago, Baitbucket said:

Another video here with some good shots of the drive well. It looks like it drops in and is removable. It looks like those 4 inner screws and 4 outer screws secure it to the kayak.

 

 

I agree.  I hate to say it but the stress will come at the molded inserts. The screws backing out are the tell tale signs. There is no way someone would forget to torque a screw durable ng icast. Typically a 1/2” -5/8”  into the thermoform.  We will see if the thermo process is stronger than roto mold.  Should be interesting. 

 

 

 

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16 mins ago, The Riddler said:

I agree.  I hate to say it but the stress will come at the molded inserts. The screws backing out are the tell tale signs. There is no way someone would forget to torque a screw durable ng icast. Typically a 1/2” -5/8”  into the thermoform.  We will see if the thermo process is stronger than roto mold.  Should be interesting. 

3

It is going to be interesting.  The flipper drives create a unique cyclic loading that the propeller drives don't.  Cyclic loading is what causes flex fatigue and cracking. We've become so used to seeing this drive we take it for granted, but I can't think of any other man-made device that works in a flapping motion on the size scale to move a person.  The only company that has had any long-term vast experience with this is Hobie, so there aren't even any other use cases to use as examples.  Sure you can FEA that models, but gets complicated fast with polymers, laminates and composites.  Thier material properties are also very influenced by processing parameters and will vary from lot to lot.  

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31 mins ago, atv223 said:

It is going to be interesting.  The flipper drives create a unique cyclic loading that the propeller drives don't.  Cyclic loading is what causes flex fatigue and cracking. We've become so used to seeing this drive we take it for granted, but I can't think of any other man-made device that works in a flapping motion on the size scale to move a person.  The only company that has had any long-term vast experience with this is Hobie, so there aren't even any other use cases to use as examples. 

Thought i read somewhere that this technology was originally designed for ships & that Hobie used that as its design model???

 

Does that ring a bell??

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2 mins ago, BillZ said:

Thought i read somewhere that this technology was originally designed for ships & that Hobie used that as its design model???

 

Does that ring a bell??

Yes, I read that somewhere too. I think it was a proposal for very large ocean going vessels. I don’t think it was ever commercialized. There may have been a prototype or two. 

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58 mins ago, The Riddler said:

 There is no way someone would forget to torque a screw durable ng icast. 

You wouldn't believe some of the simple stupid mistakes NASA techs have made causing complete loss of the craft. Things like english to metric conversions and computer code typos. Here's just one page of such: https://www.worldsciencefestival.com/2014/11/six-tiny-scientific-mistakes-created-huge-disasters/

 

But more to the point, if you notice in the video that whole plate is recessed into the deck, it simply can't rotate at all, there's no lateral load on the screws.

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In google patents, search 6,022,249

 

Last paragraph under Background of Invention:

 

The Boston Globe, May 13, 1997, reports on a mechanically powered propulsion system for ships undergoing development at Massachusetts Institute Of Technology which employs as the ultimate propulsion means a pair of flappers said to mimic the flapper motion of a penguin described as being like holding ones arms straight down with the hands open, then bringing the arms together in a clapping motion while rotating one's hands. The system includes four different motors to produce the flapping and twisting functions, all guided by a computer and complex circuiting.

 

 

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That's the one...........Well done! :th:

 

Going thru the chronological history of Hobie, seems like they introduced the working version of the mirage drive the same year...... 1997

 

Takes a while for any company to do their R&D................. there seems to be a time discrepancy with the article & the release of the mirage drive so that kind of introduces a few new questions like what came first the chicken or the egg...was someone @ hobie developing the borrowed technology

 

Regards......

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I seem to remember being told it was a DARPA inspired invention that “Hobie” subsequently acquired the rights for.

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One thing to know about Patents is that they are all in the details.  At this point in time, there are incredibly few wide reaching mechanical technology ideas that no one has every thought about, built, patented, etc.  So what you see are novel applications of an an existing technology or unique, non-obvious tweaks.  Hobie didn't come up with the basic idea of flipper propulsion, but they applied it in a novel way for use in a kayak.  When I would try to develop work arounds for patents or see if someone was infringing out our's, we'd really have to get deep into exactly what the independent claims of the patent were.

 

Here is the claim I would have focused most of my attention on.  The Patent Lawyers did a good job in getting something quite broad allowed.  I can see why no one was able to develop a practical work around for this patent.

 

A novel device adapted to be placed in a watercraft, said device including propulsion means extending below the water line comprising a pair of flexible flappers each adapted to oscillate through an arcuate path in a generally transverse direction with respect to the central longitudinal dimension of said watercraft, and means operatively associated with said propulsion means for applying input force to said propulsion means whereby as input force is applied said flexible flappers that can twist to form an angle of attack for providing forward thrust with respect to the longitudinal dimension of the watercraft while moving in both directions along said arcuate path.

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