Saturday, May 28, 2016

Tokina 12-24mm DX Zoom lens

The Tokina 12-24mm DX Zoom lens is a terrific lens, but it seems to have an annoying problem. The front ring, that the lens shade attaches to was wobbling.
I guess over time it got loose. It's easy to miss this as it's happening, it can seem like it's supposed to be like this.
Nope.  The good part is that none of the bits that are wobbling or that I'm going to tell you to mess with have any effect on the performance of the lens.
Here's the fix. It's easy
At the front there is the detachable lens shade (and lens cap of course)
Attached to the lens body are the wobbly outside part (like a tube) and the stepped black surround to the front lens element.
If you're having the problem I had, when you wiggle the lens you'll hear a rattle--that is three little screws loose inside...
First you'll have to remove the stepped lens surround. There are two notches for a lens wrench. I just poked my finest phillips head electronics/computer/camera screw driver in one of the notch and it easily rotated counter-clockwise. A few turns and it comes off.
Be careful because as soon as it comes off the wobbly part will come right off and the loose screws can fall out.
Now you can see what the problem is. These screws need to be reinserted.
There are two sets of holes in the loose piece offset by about 10 degrees. There are three issues to deal with.
First, is there any dust in there? I didn't see any.
Second, what's going to keep them falling out again? I put some Locktite on each of them. (Does this work on plastic? I hope so).
And third, which holes to use?
Not hard to figure out. Put the lens on the camera body the shade on the wobbly part; then set it on the lens. It'll be very clear which set of holes to use. For me it was the ones on the left side as you look at the front of the lens.
Take off the lens shade, dip the screw threads in a little bubble of LockTite and screw them in.
Then screw in the stepped-black-surround, I just used my fingertips.
It's all tight and good.

I included this because I found some information when I was trying to figure out this problem, but nothing specific to this lens and this exact problem.
Of course there were numerous postings of people who've had this problem, but little information (unless I missed it).
Yes,  you're absolutely correct--I should've included photos. However, I don't think any one reads this blog. If anyone actually needs photos. Let me know, I'll take the front bit off my lens ....

Saturday, March 12, 2016

Kayak: The Iqyax (Baidarka) Problem (MAE 593)

The Iqyax Problem, aka the Baidarka Problem. George Dyson framed this question in his paper on the Baidarka.  (Dyson and many others use the Russian or Ukrainian term 'baidarka.' The people who used this term were colonizing **** who banned fast kayak designs, enslaved, exploited, murdered... another nasty holocaust, so why use their term? The Unangan, Aleut people used the term iqyax for their amazing craft--I may spell it differently and make other errors, but I will argue that we should use their term. As I understand it iqyax is the same word as kayak or qajaq, etc... but is unique enough that it can be used to specifically denote the type of fast skin boats made by the Aleuts.

Reliable 18th century reports that Aleuts were paddling their iqyax at 10 sea miles, or 10 knots. The most reliable account is from Captain Cook's navigator.
Modern Olympic--world class--paddling speeds over 1000 and 2000 meters are about 12 knots. Apparently the Aleuts could keep these velocities for long distances.
Yes they were stronger. Archaeological studies of arm bone rugature, muscle attachment for Aleut male skeletons indicated that on average they had the strongest arms in history.
Dyson conjectured that to achieve these velocities the Aleuts probably were planing on the surface, like modern speedboats. If you've ever operated one, like a Bayliner, they're a bit sluggish starting out, but once they being planing on the surface less power is needed and they move a lot faster.
Dyson then calculated the energy needed to plane a kayak. Humans, strong humans, can do it, but not for very long. Even super strong humans--with history's strongest arms--can't do it for very long.
So, if the Aleuts accomplished this: How did they do it?

I've been trying to figure this out since 1992 when I George Dyson's article in Scientific American. I've been building kayaks since 2004. I was in a couple of Hobies a couple of times prior to building one that I launched in July 2005. I've been paddling and building since then. Something about Dyson's article connected.
A few years ago I came up with a few ideas. I gave myself a year to test them. If I wasn't able to test my conjectures I'd share my ideas.
Two things.
1. Kayak community blogs are an endless melange of 'hull speed', 'hull speed,' and a lot of 'gee whiz, what if...?' There's a lot of good information, but it seems to always dead end.
2. I confess that I'm in the 'gee whiz, what if...?' side of things, but not in a conspiracy theory perpetual motion tinfoil hat kind of way. (I hope)

Summer 2015 I felt compelled to finally build a skinboat. I'd previously made two wood strip kayaks, one 17' long 23" beam Great Auk Hull the other a 20' 17" beam Mystery. Both Guillemot, Nick Schade designs (but I always mess with the deck design, so I think he just shakes his head and hopes whatever I'm doing is not contagious. )
The 20' is about as fast as the 17'. I was warned, but I wanted to find out for myself.

Well I had to build a skin on frame someday and not just any SOF. I decided to build from "David Zimmerly's drawing of the Museum of Anthropology and Ethnology's (St. Petersburg, Russia) kayak MAE 593-76 (1986:16, fig.16). It measures 19'1" long, 17" wide, and 8-3/8" deep to sheer"(Harvey Golden)  

This is an iqyax from 1845 and as I understand is the closest known Aleut iqyax to the 10 knot iqyax of 50 years before. 
The Russian colonizers banned the super fast kayaks in about 1800,because they were faster than anything the Russians had--except bullets. So there are no good extent examples.

So here's my basic conjecture in a nut shell.
The four stringers of MAE 593 are not evenly spaced between the keelson and the gunwale. They seem to be bunched up close to the gunwale with a big gap between stringer #1 and the keelson. 
It is my conjecture that this gap allowed the sea lion skin to curve forming a scoop that ran the length of the craft. This scoop trapped or entrained water channeling it aft as the iqyax moved forward. Right underneath the paddler's position a subtle change in the stringer narrows this channel--this would force x amount of water into an x- (minus) cross section. It can't speed up very much so it lifts the craft right at it's center of mass (the paddler). 
The stringer/keelson channel then runs to the aft of the craft in a parallel.
Drawing not to scale. 
 Before I explain further, I would like to say that building my iqyax was a wonderful experience. I grew to loathe planing thin strips of wood and gluing them together--mostly because I wasn't any good at it. I've built many things, some beautiful furniture. A wood strip kayak, or boat, is a completely different task. I'm good with wood, with tools, but I lack patience. My assumption that I could quickly build a stripper is probably like saying, "I know how to saw wood, so I'll bet I can quickly learn to play the violin." 

There are few objects as beautiful as a well made wooden strip kayak, Giotto comes to mind-but not much else, so if you have the patience--get started--you won't regret it. (I don't regret it, I'm just more interested in the paddling it than the building.)  
The parallel frustration building a skin-on-frame craft is steam bending. I eventually bent 40 ribs and then Corey Friedman said, just heat up water in a metal rain gutter...Probably a good idea to take the class. It'll be cheaper and quicker and your iqyax will track straighter.

Everything else was fun.  Sewing the skin? I loved sewing the skin. I look for projects that might require the type of sewing a skinboat requires. I watched Corey Friedman's videos dozens of times. I wore my sinew-calluses proudly and miss them.
My ideas and conjectures changed markedly as I made my iqyax. (If you happened to have followed David Hockney's Secret Knowledge book, Vermeer's Camera, etc... you may also have noticed that it was academics and not painters who argued against the use of camera obscura, mirrors, lenses, etc... I've worked with artists. Malcolm X saying "By any means necessary," he probably got from an artist. All the worriers on TV about Y2K disaster it was pointed out to me were consultants, not one of them was a coder. The coders were saying, "Ah, this is what we spend most of our time doing, fixing code. It's a two week problem.") 
Hands on is always best. History was hands on. 

Further explanation: 
1. Extent kayaks in museum collections appear to be in rough shape. Inuit and Aleut kayaks are living forms (and male BTW). The skins are replaced every year, the thin strips of wood lashed together will move and bend over the years. Wood that was once flexible is now brittle. So MAE 593 might have been a superfast and the design trick is too subtle to be obvious in a 160 year old museum specimen. 
2. The superfast iqyax were banned by about 1800, so we might not have any physical evidence available anywhere. (Though I'm hoping Robert Ballard searches the coldest depths of the Bering Sea...)
Now on me:
3. I don't know the difference between the properties of sea lion skin and ballistic nylon.
4. Therefor I cannot claim to be able to describe what the 'channel or scoop' would be like.
5. I don't have the math skills to figure out what physically happens to X cross section of water moving at 6-10 knots down a channel of unknown dimension reaching a point where the channel narrows to X– cross section. The result is basically a lift versus drag situation. 
6. I'm 60 years old. In pretty good shape, a pretty good paddler... but I'm still old.
 There's a lot I don't know. 
The iqyax I built has a tendency to turn left, which I've trimmed with a rudder. This increases drag. My iqyax is not very fast. 3.3 knots is typical. (In my Mystery and Great Auk, 4.3 knots consistently). 
I was hoping that I might detect some of the effect I'm after, but I'm just too slow. The best way for someone like me to test my idea would be with models in a tank. I've got a 21' tank, I've figured out how to tow models, measure, etc... but I haven't done it. 

Related aspects to my conjecture:
I think the superfast iqax is basically designed to 
1. be narrow and have a small cross section (basic features of a fast kayak)
2. Many if not most of it's specific design features are to support the channeling of water down the stringer #1 keelson scoops.
3. It's hinged keelson is designed to keep the whole length in the water at design depth, so the scoop intake near the bow is in the water, and the channeled water exits near the stern. 
4. Overall the iqyax is to be extremely flexible. To support this, its deck is flat, it's depth (height) is shallow. (a thin piece of wood is more flexible than a thick one)
5. The loose rocks known to be carried inside, I think were positioned fore and aft of the hinged keelson to keep the bow and the stern in the water at 'design depth' to most effectively channel water.
(Ballast in a kayak if you've ever used it, is best very low down and near the center of gravity--where you are sitting. BTW the best and cheapest stuff to use are iron weight lifting plates. ) 

6. The split bow. The lower jaw of the split bow may have worked like a bulbous bow, it's meant to be under the surface-but there are no extent designs that do this. The upper and lower split bows as extent examples seem to indicate slide past each other--allowing more flexibility.
Evidence? I've been paddling my iqyax for months and I've never been able to 'hook' anything in the open split. I have a design using piano wire to fix the problem of picking up weeds, but I don't need it. I've even tried paddling right into weeds and kelp and I haven't hooked anything. Drawings of the Aleut iqyax often show baleen protecting the open split. If their bows were under the surface this would be necessary. 
I also feel fairly certain that one of  the purposes of the split bow is to have a lot of buoyancy at the top, and a very narrow entry at the bottom. I'm betting that sea lion skin stitched to make the concave shape would have problems, the stitches would stretch open... This may have been one path to the overall design.

So how did the Aleuts empirically come up with the superfast iqyax design?
The split bow. Narrow bows were faster, but narrow bows would sink in an oncoming wave or swell. More buoyancy was needed. They may have tried lashing floats to the top of the bow, but... that didn't work. The split bow did. 
The split bow then offers the possibility of a more vertically flexible craft. This in turn if discovered to be more effective led to the invention of the hinged keelson. 

Here I step into the history of science. We moderns tend to think that others slowly developed new designs over hundreds and thousands of years. I think the Aleut Iqyax has so many unique features, like the hinged keelson, that it indicates that observant paddlers noticed certain features of kayaks were better and then began to pursue these features and ideas in a disciplined way. 
The standard 'wonderful' kayak design is widespread across the arctic. It's the big Hudson Bay 'station wagon,' or 'soccer mom van' Nanook paddles in Nanook of the North. It's stable, seems sturdy, and there's plenty of room inside for his child, a couple of dogs, his two wives and the baby. Kayak designs only begin to have specific capabilities when you get to Greenland, the Aleutians, (others know more about this than I). Overall? A kayak just has to be stable, have room inside for family and stuff, and not be too large to be unmanageable in the wind.  So I think when you get to Greenland and the Aleutians, people started to consciously invent, test, make changes. Also it was typical to replace the skin on a kayak every year. Once you get down to the wooden frame you can change things. 
Another factor might be like my iqyax, it veers to the left. If I remove my skin and fix the problem, I will have to sew on a new skin and re-coat, about $300. If an Inuit, Eskimo or Aleut had this problem, they could take out the stitches, fix the problem and sew the same skin back on. 
Suppose you start fixing ribs. Are they likely to get longer? Not a chance, wood doesn't stretch. They are more likely to get shorter. This makes for a narrower and shallower craft, which will be faster.  So, annual re-skinning invites modifications, ease of taking it apart to make repairs, invites further modification and lowers the cost of trying out radical ideas. 

I think that trying to figure out how the superfast Aleut iqyax was invented might lead to a better understanding of pre-modern inventiveness that is probably worldwide. (Have you seen Wally Wallington's videos of him moving multi-ton blocks of concrete by himself? I suggest that the Mayans, the Egyptians, Rapanui-ans, and my ancestors at Stonehenge  had all of their schemes scaled up because an old carpenter like Wally, said, 'Hey, why don't you try it like this...' suddenly they could move stones 10 or 100 times larger and more easily than could the day before. We haven't figured this out yet because there was no YouTube. Instead we think bigger stones more guys pulling on more ropes.... Also look at the PBS Nova program about raising an Egyptian Obelisk. The brilliant engineer (and academic) missed something no framing carpenter would've missed. The timber framer figured out a practical, efficient and reasonably safe way to raise the obelisk. I think it's now considered solved that the people on Rapanui (Easter Island) 'walked' the giant heads to where they were displayed. Polynesian-Wally. )

NOTE: If you read some of my other blog entries you will notice that my iqyax has outriggers. I'm not sure anyone could paddle it as designed without them. I'm willing to let someone, like a surf ski paddler, try. I may have more hours paddling an 1845 MAE 593 than anyone (since 1845) only because of the outriggers.

OK, this is unedited, needs more images..... but for now...