Kydex for a BP still the right choice

[cruisediver69]

I just recently finished making an extra long (18”) back plate out of Kydex. I am quite happy with how it has turned out. However I am curious if Kydex is the preferred plastic to make a BP out of. I looked at ABS but didn't like how flexible it was. Are there any other reasonable choices?

 

[cool_hardware52]

I just recently finished making an extra long (18&#8221 back plate out of Kydex. I am quite happy with how it has turned out. However I am curious if Kydex is the preferred plastic to make a BP out of. I looked at ABS but didn't like how flexible it was. Are there any other reasonable choices?

Kydex is much tougher than ABS, has better impact resistance, and is much less likely to crack than straight ABS.

Tobin

 

[Couv]

Hello Cruisediver69,

I'd love to see your BP. How about posting some pictures and a description of the work steps, where you bought the material, cost, what problems you had to solve, what you would do differently, etc.

Thanks,

Couv

 

[dumpsterDiver]

http://www.scubaboard.com/forums/making-your-own-gear/325169-diy-backplate-pvc.html

Still works..

 

[cruisediver69]

Kydex is much tougher than ABS, has better impact resistance, and is much less likely to crack than straight ABS.

Tobin

When comparing those two materials side-by-side it was clear to me that I wanted to use Kydex over ABS. I am just curious whether there is a material that is better than Kydex. Kydex flexes a little to much for my liking and I am concerned about the material tearing or breaking around all of the locations where I drilled holes or cut slots.

 

[cruisediver69]

Hello Cruisediver69,

I'd love to see your BP. How about posting some pictures and a description of the work steps, where you bought the material, cost, what problems you had to solve, what you would do differently, etc.

Thanks,

Couv

Unfortunately I didn't take many pictures while building it but will write up the details in a subsequent post.

 

[cool_hardware52]

When comparing those two materials side-by-side it was clear to me that I wanted to use Kydex over ABS. I am just curious whether there is a material that is better than Kydex. Kydex flexes a little to much for my liking and I am concerned about the material tearing or breaking around all of the locations where I drilled holes or cut slots.

I would not recommend using kedex without reinforcing the harness slots and other highly loaded points

Tobin

 

[cruisediver69]

Somewhere along the line I had convinced myself that I needed a BP that was built to fit my body rather than try to adapt my equipment to fit a standard BP size. In particular I wanted one that was:

1) longer than normal to properly fit my back
2) allow me to position the waist belt where it should be instead of half way up my chest
3) allow me to mount my AL80 doubles lower on the BP to allow for a more natural, unweighted trim point.

I spent some time building a model out of cardboard as a mock up. By the time I got finished “tuning it” I ended up with a BP that is 11.5” at its widest point and 18” tall at its longest point. I also knew that I wanted to be able to use this BP for single AL80 tanks as well so it would need to have a built in STA.

Once I finalized the measurements I went looking for material. Although I had access to a local plastics shop they didn’t carry drop sizes in Kydex and I wasn’t happy with the looks of the drop ABS they had available. I found a place online called Harva Plastic which sells odd sizes of Kydex-T. They had a 13”x20” piece of 1/8 Kydex-T that ran me around $20 including shipping. The size was perfect for what I needed and I even liked the red color it came in.

The next step in the process was to translate the cardboard mockup into a wooden form. I can go into more detail of how I did this if someone wants but the essence was to use the skill saw to cut some scrap pieces of lumber at the appropriate angles and then screw it all together. The original intent was to create the bottom form and then a top form. The reality was that I created the bottom form and got lazy and decided that was all I needed. Fortunately I was right.


This is what the wooden form looks like.

Once the Kydex sheet arrived I made the initial cut so I ended up with an 18”x13” sheet. I placed this on top of the wooden form and then used my Harbor Freight (cheapy) heat gun set at 1200 degrees to soften up the Kydex. I kept the gun moving in strokes until the Kydex softend to the point to where it started bending on its own. I then took an 18” piece of scrap wood and held the kydex in place within the center of the form while it cooled. Suprisingly I had to put a lot of pressure on the scrap lumber to keep the Kydex in place. The good thing is that it was easy enough to reheat parts of the Kydex and reform it if I didn’t like the shape it took.


This is what the Kydex looks like after it was heated and then cooled on the form.

 

[cruisediver69]

My next step in the process was to locate the holes for my doubles. I have my doubles bands located in the standard place on my tanks so that me gear setup is directly usable on rental tanks as well. You will notice in the next picture that my holes in the BP are much lower than they are in most standard BPs. This is by design. I have long arms and am head heavy. For my AL80s I wanted to position the tanks much lower on my body than normal but of course still be able to perform a valve drill. To figure out the ideal location for the holes I used a standard aluminum BP and loosened the harness until it was located ideal for me. I then measured the amount of harness adjustment and added that to the standard hole location position to get the new placement.


This is what it looks like with the holes drilled and mounted in its current form to the tanks.

The next step was to make the cosmetic corner cuts on the top and bottom of the BP. I used a template I made on the computer to ensure everything was symmetric and drew the template onto the Kydex with permanent marker. I used a jigsaw to make the cuts. My jigsaw allows me to adjust the speed of the blade. If it is set too high it will melt the Kydex more than it will cut it so I had to set it fairly low. I also used a bottle of water to cool the cuts as they were being made so that the pieces wouldn't fuse behind the blade after the cut was made.


This is what the BP looks like after the cosmetic cuts.

I decided to locate the harness on the bp in the same relative position from the edge of the BP as it is located on my standard aluminum one. Since this BP is longer and wider that in effect located the waist belt of the harness approximately 4 inches lower than it is located on a standard BP. It also placed the shoulder straps 1 inch further out on each side. Both adjustments, although not perfect for me, are much, much better than the standard BP.

To make the harness holes I used the standard aluminum BP as my template for the angle and positioning and drew them on the BP using a permanent pen. I then used a drill press to make a couple of holes so that I could get my jigsaw in there to make a fairly clean cut for each cutout needed.

After all the cuts were made I found 150 grit sandpaper followed by 240 grit sandpaper cleaned up all of the cuts made from the jigsaw nicely.


This is what the BP looks like with the harness slots cut into it.


Finally this is what the BP looks like with my harness threaded on it and it is mounted on my doubles.

I currently have a completed a couple of pool dives along with one pair of open water dives on the BP and have to say it fits me much better than my standard BP. I still need to figure out how I want to reinforce the holes harness slots but aside from that I am pretty happy with the final result.

 

[Couv]

Well done and thank you for taking the time to share the knowledge.