Mata Hari

The Wyman Engagement Photos

February 11, 2015February 10, 2015
Photography

The View

18.0 mm || 1/25 || f/3.5 || ISO3200 || NIKON D7000
Seattle, Washington, United States

Charlie Pondering His Future

18.0 mm || 1/13 || f/3.5 || ISO3200 || NIKON D7000
Seattle, Washington, United States

Test Shoot with Rachel

24.0 mm || 1/20 || f/1.6 || ISO3200 || NIKON D7000
Seattle, Washington, United States

Setting Up the Boat

24.0 mm || 1/60 || f/1.4 || ISO3200 || NIKON D7000
Seattle, Washington, United States

24.0 mm || 1/60 || f/1.4 || ISO3200 || NIKON D7000
Seattle, Washington, United States

24.0 mm || 1/80 || f/1.8 || ISO3200 || NIKON D7000
Seattle, Washington, United States

Stephanie hoisting the lights

24.0 mm || 1/30 || f/1.4 || ISO3200 || NIKON D7000
Seattle, Washington, United States

24.0 mm || 1/30 || f/2.8 || ISO3200 || NIKON D7000
Seattle, Washington, United States

Charlie Pondering His Future, Again

24.0 mm || 1/50 || f/1.8 || ISO3200 || NIKON D7000
Seattle, Washington, United States

The Setup

24.0 mm || 1/30 || f/1.8 || ISO3200 || NIKON D7000
Seattle, Washington, United States

24.0 mm || 1/50 || f/2.5 || ISO3200 || NIKON D7000
Seattle, Washington, United States

Surprise

24.0 mm || 1/640 || f/1.6 || ISO3200 || NIKON D7000
Seattle, Washington, United States

That View

24.0 mm || 1/60 || f/1.6 || ISO3200 || NIKON D7000
Seattle, Washington, United States

So Far, So Good

24.0 mm || 1/60 || f/1.6 || ISO3200 || NIKON D7000
Seattle, Washington, United States

Dancing to the Music

24.0 mm || 1/60 || f/2.0 || ISO3200 || NIKON D7000
Seattle, Washington, United States

What’s This? A Boat? With Christmas Carolers? In January?

24.0 mm || 1/60 || f/2.0 || ISO3200 || NIKON D7000
Seattle, Washington, United States

Will You?

24.0 mm || 1/60 || f/2.0 || ISO3200 || NIKON D7000
Seattle, Washington, United States

Three Cheers!

24.0 mm || 1/60 || f/2.0 || ISO3200 || NIKON D7000
Seattle, Washington, United States

Huzzah!

24.0 mm || 1/60 || f/2.0 || ISO3200 || NIKON D7000
Seattle, Washington, United States

See the rest of the photos at: https://www.flickr.com/photos/afdn/sets/72157650275210685

Most pictures taken with: Nikon 24mm f/1.4

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End of Summer

October 29, 2013October 30, 2013
Photoblog

Yes, I’m still in denial.

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Block and Tackle Efficiencies

May 7, 2013May 7, 2013
Answers

Not long ago a friend was looking to upgrade the mainstay¹ block and tackle system on his sailboat.

The question was if the proposed system would provide the anticipated reduction in force. It was an interesting question that, while seemingly straight forward, does have a couple of gotchas.

Block (pulley) and tackle (rope) calculations are usually pretty simple, with the mechanical advantage (MA) idealized as:

$MA = \frac{F_B}{F_A} = n$

where F_A is the input force, F_B is the load, and n rope sections.

Calculating the total force of multiple non-colocated blocks using the same tackle presented a fun challenge that requires one to take into account the individual location of the blocks and the forces transfered.

I did not draw every single link of the block and tackle, but in general the problem looks something like this:

Considering the moment arm:

$F_{L} = (F_{A} \times A) + (F_{B} \times B)$

We devise these relations:

$F_{A} = n_{AD} \times F_{P} \times \arctan\left ( \frac{\left | A-D \right |}{h}\right )$

and

$F_{B} = n_{BC} \times F_{P} \times \arctan\left ( \frac{\left |B-C\right |}{h}\right ) + n_{BD} \times F_{P} \times \arctan\left ( \frac{\left |B-D\right |}{h}\right )$

where n_xy is the mechanical advantage coefficient at a given point, x, with respect to another point, y; F_P is the force exerted on the tackle (which must be uniform throughout!).

Using some assumptions regarding the lengths and relative positions of the blocks greatly simplifies the calculations, and we can plug ‘n chug from there:

$F_{L}=F_{P}\cdot \left ( \frac{n_{AD}}{2} + \frac{n_{BC}}{4} + \frac{n_{BD}}{4}\right )\cdot \cos{(\arctan(\frac{l}{8h}))}$

As expected, there is a loss of useful force due to the ropes not being normal to the boom and that causes the boom height/length ratio to become an interesting variable in these calculations. You lose 10% of your power with a 1:3.87 ratio, 25% with a 1:7.06 ratio, and 50% with a 1:13.86 ratio.

To model a direct input (with no block and tackle), I assume that the force was applied at a point between the two blocks, A and B, and normal to the boom.

The increase from no block and tackle system to the current system (single boom aft block, A; double boom traveling block, B) is:

$\frac{F_{P}\cdot \left ( \frac{2}{2} + \frac{2}{4} + \frac{2}{4}\right )\cdot \cos{(\arctan(\frac{l}{8}))}}{\frac{3\cdot F_{P}}{8}} = \frac{16}{3}\cdot \cos{(\arctan(\frac{l}{8h}))}$

…assuming the boom heigh/length ratio is 7, the mechanical advantage is 1:4.01.

Moving from no block and tackle to the the proposed system (double boom aft block, A; triple boom traveling block, B) is:

$\frac{F_{P}\cdot \left ( \frac{4}{2} + \frac{3}{4} + \frac{3}{4}\right )\cdot \cos{(\arctan(\frac{l}{8}))}}{\frac{3\cdot F_{P}}{8}} = \frac{28}{3}\cdot \cos{(\arctan(\frac{l}{8h}))}$

…again, assuming the boom heigh/length ratio is 7, the mechanical advantage is now 1:7.02.

The mechanical advantage from current system to proposed system is: 1:1.75

$\frac{F_{P}\cdot \left ( \frac{4}{2} + \frac{3}{4} + \frac{3}{4}\right )\cdot \cos{(\arctan(\frac{l}{8h}))}}{F_{P}\cdot \left ( \frac{2}{2} + \frac{2}{4} + \frac{2}{4}\right )\cdot \cos{(\arctan(\frac{l}{8h}))}} = \frac{3.5}{2} = 1:1.75$

It’s not quite the 1:2 advantage originally thought, but it’s close.

Epilogue:

The bonus gotcha occurred when said friend opted to install a double boom aft block (A) and a triple deck traveler block (D), but keep the boom traveler block (B) as a double. Essentially, putting an extra “loop” just between the boom aft block (A) and deck traveler block (D).

The imbalance of tension on the deck traveler block caused it to experience shear stress and bind on the traveler rail in ways it was not designed to — not good.

Converting the boom traveler block (B) to a triple and the deck traveler block (D) to a quad equalized the tension.

Problem solved.

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rope from the top of the main-mast to the foot of the fore-mast on a sailing ship ↩

Duck Dodge

February 12, 2012
Photography

I currently have a back log of 1500+ photos dating back to February of last year. My goal was to get them all done by the end of last year, but that obviously didn’t work.

Every summer, I usually get the pleasure of participating in a few Duck Dodge events on Lake Union as part of the crew of the Mata Hari. Paul asked me to take some pictures of them racing though, which was an awesome challenge and opportunity to follow the Mata Hari around the buoys in a Boston Whaler while trying to take pictures, and not hit anyone!

This is also the first chance I’ve had to use VSCO’s film pack for Lightroom…still getting used to it, but I like the way they turned out!

25.0 mm || 1/250 || f/6.3 || ISO100 || NIKON D7000
Seattle, Washington, United States

18.0 mm || 1/1000 || f/5.6 || ISO1000 || NIKON D7000
Seattle, Washington, United States

200.0 mm || 1/500 || f/4.8 || ISO2500 || NIKON D7000
Seattle, Washington, United States

70.0 mm || 1/250 || f/6.3 || ISO100 || NIKON D7000
Seattle, Washington, United States

56.0 mm || 1/160 || f/6.3 || ISO100 || NIKON D7000
Seattle, Washington, United States

70.0 mm || 1/6400 || f/8.0 || ISO1000 || NIKON D7000
Seattle, Washington, United States

31.0 mm || 1/1000 || f/4.0 || ISO800 || NIKON D7000
Seattle, Washington, United States

As usual, you can see more on Flickr: Duck Dodge (6 Sept 2011)

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Summer Sailing Adventure

September 15, 2009
Photography

GPS data visualized using Google Earth.

GPS data visualized using Google Earth. Click image to embiggen.

Before I left on my trip, I had the opportunity to go sailboat racing with some friends on the Mata Hari. This was also a perfect opportunity for me to test integrating the Amod GPS unit (Google Maps version of the race data or just download the raw KML file.). Unfortunately, I went sailing the weekend before I left and didn’t have time to edit the photos and put them online before I took off.

I finally got around to editing them last night. Part of the reason it took so long to edit them after I got back is that I’ve really been burned out with photography and needed a break. I’ve hardly picked up my camera since I got back and almost contemplated selling it (I’m pretty sure this is a normal feeling, and don’t worry, I’m keeping it).

Last night was really fun though. I’m still not quite ready to pick up my camera, but I’m getting close. I have another couple hundred photos to edit from Edays (yes, from April…holy crap). Perhaps after that, I’ll start doing some more picture taking. In the meantime, enjoy these photos from the beginning of summer as we start to welcome our Fall Overlords.

70.0 mm || 1/2000 || f/4.5 || ISO200 || NIKON D70
Seattle, Washington, United States

18.0 mm || 1/2500 || f/4.5 || ISO200 || NIKON D70
Bainbridge Island, Washington, United States

18.0 mm || 1/2500 || f/4.5 || ISO200 || NIKON D70
Seattle, Washington, United States

70.0 mm || 1/1600 || f/4.5 || ISO200 || NIKON D70
Bainbridge Island, Washington, United States

18.0 mm || 1/2000 || f/4.5 || ISO200 || NIKON D70
Seattle, Washington, United States

112.0 mm || 1/800 || f/5.6 || ISO200 || NIKON D70
Seattle, Washington, United States

70.0 mm || 1/500 || f/4.5 || ISO200 || NIKON D70
Seattle, Washington, United States

18.0 mm || 1/1250 || f/4.5 || ISO200 || NIKON D70
Wautauga Beach, Washington, United States

22.0 mm || 1/2000 || f/4.5 || ISO200 || NIKON D70
Bainbridge Island, Washington, United States

70.0 mm || 1/1000 || f/5.6 || ISO200 || NIKON D70
Hawley, Washington, United States

180.0 mm || 1/1600 || f/5.6 || ISO200 || NIKON D70
Manitou Beach, Washington, United States

300.0 mm || 1/1250 || f/5.6 || ISO200 || NIKON D70
Rollingbay, Washington, United States

As is our usual agreement, the rest of the photos can be found on Flickr at: Summer Sailing 2009

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