8x20 Holders: Just completed 6 of them...
Well, actually I just completed 5 of them... after I put the first prototype holder through a couple of years of field experience to verify my design.
After I bought my new Canham and saw the $400 price tag for 8x20 holders, I decided to put my woodworking skills to use and make a few of my own holders. Using an ancient 8x20 Corona holder as a typical example, I came up with a design, cut parts for 6 holders, and assembled one of them for verification. It worked beautifully, but I just didn't have the time to finish the other 5 until I retired a few weeks ago.
If you're entertaining the idea of making your own holders, here are some of the things I encountered:
Accuracy cannot be taken for granted. One must work with precision measuring instruments typically used in metalworking. You can't measure to plus or minus 0.005" using a metal ruler.
A thickness planer capable of sizing wood to 0.005" is mighty handy. The router table must be FLAT, and you'll need a way to measure cutter depth to 0.005". You may even need to have cutters ground to specific sizes for slotting the siderails. I have small vertical milling machine which I used to machine intricate joints and the recesses for the light baffles.
At first, I experimented with Oak, but quickly recognized the wisdom of the ages, and used Cherry. Super stable, strong, it machines beautifully, and doesn't split. The parts for the last 5 holders were in storage for the past 3 years, and were just as straight and precise as the parts used for holder number one.
The hinge cloth is a bookbinders fabric which I tested for flexing and cracking. I made a sample hinge and submitted it to 2700 complete reversal (180 degree) bends, with no sign of pinholes thru the coating.
The darksides are "Garolite", a phenolic material, and the septums are 6061 aluminum, both from McMaster-Carr.
It's a complex project, now I understand why these things cost a much as they do...
I agree these things are pretty complex. What did you use for the light trap? How thin is the garolite you've used? I'm building a wetplate holder and would appreciate any tips on these materials. I decide to use 1/16" garolite since I only need one holder for wetplate and decided it could be fairly robust as a result.
I purchased a new walnut 11x14 holder from AWB several years ago and just marvel at the construction ever time I use it. Pricey, but a beautiful piece of woodworking.
Bookbinders cloth? Pray tell more. Where did you get it?
For the light baffles, I cloned the old Corona. It had two strips of thin brass, folded into long "vee's", with a narrow strip of black velveteen glued onto each strip. (I used ordainary 3/8" wide black velveteen ribbon from Fabric Land). They were set down into two parallel grooves, and acted just like the spring action weather stripping on a typical good quality front door. The brass can't be over 0.002" thick, or the insertion force for the darkslide will be too great.
I used 0.032" Garolite. It's a bit thin (I wish it were available in metric thickness, 1 mm would be perfect. By being careful about the spring action on the baffles, I can keep the insertion force low enough so the 1/32" Garolite won't try to buckle. Another advantage is that the total weight of the holder is kept down to a svelte 2lb-3oz, compared to 3lb-6oz for my Blunderbuss Wisner holders.
I got the bookbinders cloth from a local bookbinder (of all places). I picked up a few samples to try, and decided on a pseudo "leatherette" texture on a coated cloth that's 0.012" thick.
Here's a photo of my efforts...
Nice job, Reinhold, the holders look very good!
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Do you have any interest in sharing your technical expertise with others? I think a web page about this project would be popular.
Unless you're thinking of making these as an extra source of income, of course. The market could always use a little competition.
Congratulations on completing your project. The holders look beautiful.
Film is cheap. Opportunities are priceless.
Thanks for the comments. These things give me pleasure every time I pick them up.
I thought about publishing the details, but my web expertise is zero. The idea of offering some for sale also crossed my mind, but making these things would get in the way of taking pictures. What to do.....?
I know.... There's a P-38 and a PBY Catalina not too far from here. I'll put some film in my new "babies" and let them see what old airplanes look like!!...
See you folks later...
Wow, they are really nice. Makes me almost want to take up woodworking, but I am still trying to figure out photography.
Originally Posted by Reinhold
If you want, I would be happy to thow together a web page that you could post on a free web host or the like. You could also get some space from Sean for a few bucks and avoid the ads you get with the free ones. Let me know.
First rate work, Reinhold, really nice. Woodworking and photography are truly made for each other (I just finished a 4x5 camera and a tripod).
-I wanted to ask how you cut the phenolic material, with a special table saw blade or maybe a trim router? I've always wanted to build a ULF, but the cost of the holders alone has almost singlehandeldly held me back. Thanks, Colin