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Thread: 14x17 film holder build question

  1. #1

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    Mar 2017
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    14x17 film holder build question

    Rather than hijack another thread, I thought I'd start one of my own on this topic.

    I got some ruined sheets of 14x17 x-ray film in the mail today, and I plan to use them to build a ULF camera. It' a long-term project, with no planned completion time, but the film holder is obviously the place for me to start. I'm wondering what others have used for septums in their big film holders. Rigid, thin, and lightweight are not an easy combination.

  2. #2

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    Re: 14x17 film holder build question

    In my experience, starting with the film holders is the best method when you don't have a lot of prof or semiprof woodworking tools available!

    When you get above 8x10", making a lightweight holder which is perfectly true becomes almost impossible.

    I have gone in a different direction and made sure that the mounting system to the camera will hold the somewhat lightweight (and flexible) holder in a perfectly flat plane. This can be done by using a rail or slot system. Of course, the holder has to be perfectly square, but this is not that difficult to achieve.

    My experience is also that single, rather than double holders, is the way to go. I have worked with up to 14x16".

  3. #3

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    Re: 14x17 film holder build question

    Disregarding cost, I'd go with 1/8" carbon fiber sheets. Lightweight, flat, stable, lightproof.
    Next choice would be Garolite or black acrylic. Garolite would be very consistent in thickness, whereas acrylic varies a lot, which could be an issue.

  4. #4

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    Re: 14x17 film holder build question

    Thanks for the tips!

    Steven: I hope to make these to ANSI specifications (I like a challenge), but if I find that I cannot do that (I often fail at challenges!), I'll keep the rail/slot and single-sided ideas in mind.

    radii: I will check up on Carbon fiber. I've already done some research on Garolite (I even found a place that will cut it to my exact dimensions for a very reasonable cost). Do you have a suggestion for what thickness to go for? Weight is an issue, but I'm wondering if rigidness might be more important for the septum.

  5. #5

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    Re: 14x17 film holder build question

    Quote Originally Posted by Paul Kinzer View Post
    Thanks for the tips!

    Steven: I hope to make these to ANSI specifications (I like a challenge), but if I find that I cannot do that (I often fail at challenges!), I'll keep the rail/slot and single-sided ideas in mind.

    radii: I will check up on Carbon fiber. I've already done some research on Garolite (I even found a place that will cut it to my exact dimensions for a very reasonable cost). Do you have a suggestion for what thickness to go for? Weight is an issue, but I'm wondering if rigidness might be more important for the septum.
    In hindsight, a 1/16" thick Garolite septum could have been sufficient as well, but 1/8" is not a bad choice, all things considered. A lot (most?) of the rigidness off the holder will come from the stiles and rails of the frame construction. The holder is essentially the same as a cabinet door with a floating panel. The flatter and sturdier your outside frame is, the better. A thick septum won't bend a wonky frame into submission.

  6. #6

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    Re: 14x17 film holder build question

    I checked a bit on carbon fiber sheet. Yikes! That's beyond my price range. So Garolite looks like the choice (it's 1/11th the cost!). I found it here, where they will also cut it.

    I'm thinking right now about using sandwiched layers of Baltic birch plywood for the stiles and rails. I've used it in telescope parts projects and have found it to be quite sturdy and stiff. This way, I would not need to cut slots in a single piece of wood. I don't have the tools or skills for that. If there is a reason I haven't thought of that this will not work, I'd like to hear about it.*

    I've attached a rough sketch I made of a cross section of one of the stiles. Only the thicknesses of each layer of the sandwich are drawn close to scale. The depth of the slots for the dark slides, film, and septum are not. Advice on those would be appreciated. I found the prices, thicknesses, and sizes here to be attractive. I called them today to get the actual thicknesses of each of their plywoods that I would be using. Those thicknesses are added to the drawing. The drawing shows that I'd be within ANSI standards for the 'depth to film surface' distance.

    Click image for larger version. 

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    I'll need to figure out how the stiles would intersect with the rails, and where and how to place the fingerstock I plan to use**....

    * The last time I posted an idea for a build, I got some pretty blunt, even rude, criticism. So, while I really am grateful for whatever help folks may want to offer, please don't insult me personally, or question my honesty, as someone did a few weeks back. I'm posting to get help, but I always post to forums with the idea that others might read the threads and find them helpful, too. I'm never comfortable reading threads that get derailed by commenters who get personal; nor do I get the motivation.

    ** I'd really like some pointers on what fingerstock to use, too. There sure are a lot of choices, and it's a thing I have no experience with.

  7. #7

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    Re: 14x17 film holder build question

    That looks like a reasonable way to construct the stiles. When gluing up the sandwich, minimize glue squeeze out in the dark slide and septum slots if you can. Maybe mask it with clear tape or spot wax the areas?
    Baltic birch is a great material. I see no reason why it shouldn't work.

    The fingerstock approach looks great. I had never heard of it before.

  8. #8

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    Re: 14x17 film holder build question

    A member here, Erik Larsen, made some really nice 11x14 holders. There's info about the fingerstock he used in that thread.

    It's worth mentioning that another member here reported light transparency issues with XX-Garolite stock. I've made 3 batches of holders and never had a problem with it, but different lots of the material may have some variations in the manufacturing process.

    edited to add: the term 'QC issues' was a poor choice of words on my part- I'm not sure if they even check the stuff it for opacity during quality control.
    Last edited by Colin Graham; 1-Dec-2017 at 11:53.

  9. #9

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    Dec 2014
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    Re: 14x17 film holder build question

    Hi Paul, I'd use lots of wood clamps to squeeze out excess glue to keep everything even. Small staple nails through the layers for added strength to the layers. The challenge of sandwiching method is that you may not find the right thickness to match ANSI standards. I look forward to see your progress.

  10. #10

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    Re: 14x17 film holder build question

    Thanks to both of you!

    radii: I did not see any issues with using the birch plywood, but it's nice to get confirmation of ideas from others who know what they are doing.

    Colin: When I did a search for that fingerstock at the site linked to in the thread about the holders, the was not a perfect match (there are a boatload of choices!), so I'm not positive that what came up is just what he used. I may PM Erik Larsen about this. And thanks for the info about the XX-Garolite. I had no idea.

    I'm excited to get started on this, but have to pace myself. I bad back surgery almost a year ago that did not work as it should have, so I can overdo things quickly, and funding is also an issue. But I'm a maker at heart, and this -- the whole camera, not just the holders -- is going to be a big project. I know I'll hit some snags, but overcoming them makes the end result more rewarding.

    Thanks again!

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