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Classic Wings Magazine Luftwaffe Resource Center WWII Naval Aviation Research Pacific
Final Cut-The Post War B-17 Flying Fortress and Survivors - 5th Edition


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PostPosted: Wed Jan 22, 2014 7:27 pm 
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Might check out Dennison Enterprises LLC Face Book page as well. 8)

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PostPosted: Wed Jan 22, 2014 8:22 pm 
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That looks awfully familiar... :pirate :f4u: :pirate :)

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PostPosted: Thu Jan 23, 2014 7:56 am 
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That is some phenomenal metal fabrication work going on to help restore that Navy fighter back to factory spec! Ain't many fabricators or metal whisperers left like Scott (sdennison) who can conjure this kind of metal fab skill and organic engineering to rebuild and restore complex parts and component assemblies to such an amazing level of accuracy and quality. Let's see more pics.


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PostPosted: Thu Jan 23, 2014 8:32 am 
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It's nice to see examples of what is absolutely 'right' about this website. You have one fellow (Scott) who offers us a look at craftsmanship at the highest level, followed by one of WIX most classy members (Paul) who posts a perfect and most deserving response. Two gems to grace this site from time to time and always to be appreciated for sure.

The only shame is that we don't hear more regularly from both of them.

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PostPosted: Thu Jan 23, 2014 1:07 pm 
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Kind words and thank you. There are many out there who have forgotten more than I will ever know. Look at any of the warbird restoration shops around the country and the world. I am just lucky to have learned my skills from some of the best over the past forty years. I have a number of buddies who do the same in the auto world with Cobras and other exotic cars. I am pleased to see that many of these talented craftsmen are young and will keep the craft alive.

In that vein, I recently lost my youngest son who was beginning to work with me to learn metalworking and based on a precedent set by a great metal smith, Lazze, I intend to share some of my tips and tricks for anyone interested. There are many ways to approach this type of fabrication and I will share my approach. If it is helpful, great. I will post one this evening.

Again, thank you. :drink3:

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PostPosted: Thu Jan 23, 2014 1:45 pm 
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Sorry to hear about your son Scott...terrible news.

Your fab skills are excellent...on at least the same par with any of the craftsman I've seen in the "Name brand" shops I've been exposed to. I'd love to come and apprentice with you.

John


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PostPosted: Thu Jan 23, 2014 2:19 pm 
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Scott,

Pardon my ignorance, but how do you make the 90 degree curved bent without fluting (In 1st and 2nd photo)? I have next to zero sheet metal experience, but I would like that to change...

If you're looking at sharing the tips like Lazze, it'd be cool to have a sheet metal sticky post in the RetroAviation Maintenance Hangar!

Looks great!

Taylor

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PostPosted: Thu Jan 23, 2014 2:51 pm 
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Excellent, I for one am always interested in learning the tricks of the trade so to speak. I would really like to get a whole lot better at the sheetmetal side of things as it is an amazing craft.

Scott.....


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PostPosted: Thu Jan 23, 2014 7:22 pm 
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Taylor, the trick is how tight a radius, how big a flange, what material. In this case, very thighs radius 1 11/16", but .032" dead soft 2024. The link here is that this is an outside curve. On all the other clips for this vane assembly, the angle is formed using a shrinker to make the inside curve. Very straight forward. If I used the same technique with the stretcher, the material would split. So, using the form block is an alternative. The height of the flange is about 1/2" so the material will take the stretch if you work slowly and carefully. It does thin the material .003-.004" but that's ok in this case.

As a rule, as the radius increases, so can the flange and the process gets easier. Remember, there are only four things you can do with metal, cut it, bend it, stretch it or shrink it. Therein lies the magic of metal work. When you understand why it works, you can make it work for you.

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PostPosted: Thu Jan 23, 2014 7:56 pm 
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Very nice work! :drink3:


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PostPosted: Thu Jan 23, 2014 8:58 pm 
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So, I just spent an hour posting here on my Ipad but don't see it. Now I'll do it on the computer and probably have a duplicate, oh well.

So Tips & Tricks.

I start with a poster board pattern of the contour I want to make. Then I make an aluminum template. I use the template to make the contour on the form block. I then make a poster board template for the blank and an aluminum blank. I have discovered that PVC sheet makes the best form material I have found. I use aluminum for the most durable tooling but this PVC is easily worked, shaped, and can be drilled and tapped where necessary. So I cut the form and use a simple radius gage to scrape the radius needed for the part.

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Then I pin the form block and clamp blocks together so I can make both the RH and LH parts simply by reversing the clamp block to the opposite side of the form block. Bear in mind that the clamp block shape is critical. It needs to be the same contour but the shape needs to be at the start of the radius for the part. If the clamp block does not match, the soft aluminum can distort as you try to shape over the form.

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Next, clamp the blank in between the blocks and I flow form the part using a standard 3X rivet gun fitted with a nylon head. For thin materials such as this (.032" 2024-0) it is necessary to turn the air way down and gently flow form the shape. Coax it and convince it to go where you want it go. I liken this to driving a sprint car a hard slick track, pretend you have an egg between your foot and the throttle. If you horse it, you will lose the part.

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Voila! The part can be removed and trimmed.

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The issue here is that we are doing an outside curved piece. On all the other clips in this assembly, it was easy to take an angle and use the shrinker to form the inside curve. These are outside curves and if you chose the stretcher, the material would split and tear. With these tight radius (1 11/16") the form block was my choice. Also, the height/length of the flange makes a difference. This is only about 1/2" and about the limit for this shape. The material thins by about .004" but is ok here. The larger the radius of the curve, the taller the flange can be. Remember that you can do only four things with metal. You can cut it, bend it, shrink it or stretch it. When you understand that, you can make metal do whatever you want it to.

So the form tool for the gun is readily available on EBay and can be radiused as required for your application.

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Questions? 8)

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PostPosted: Thu Jan 23, 2014 9:26 pm 
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sdennison wrote:
<snip>

So the form tool for the gun is readily available on EBay and can be radiused as required for your application.

<snip>

Questions? 8)


One question... What search terms work on Ebay for the flow forming tool? I just used up my entire vocabulary and didn't get a hit.

Googling it leads me to Kent White's site, which has great stuff, but at a premium price.


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PostPosted: Thu Jan 23, 2014 10:37 pm 
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Nylon rivet set

http://www.ebay.com/itm/360476404874?ss ... 1497.l2649

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PostPosted: Fri Jan 24, 2014 9:54 am 
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sdennison, thanks for sharing how to do this type of work!

How are these parts heat-treated to get them "hard", or are they used as made? If heat-treated, do you send them out to a commercial shop, or do you tackle that as well??


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PostPosted: Fri Jan 24, 2014 10:39 am 
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The shop has a small heat treating oven. The process is fairly straight forward. Heat to 925 degrees F and hold for a set time depending on the thickness of the part. Must quench within 8 seconds of removing from the oven. Then you have about four hours to tweek any distortion out before they age harden to full strength. Interestingly, if you chill to 32 degrees F that slows the age hardening, if you freeze with dry ice, you have weeks to work with them, then let them come to room temp and they will harden.

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