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The angle was taken from Huw Porter's design, Stainless Steel Single-tank SCUBA Backplate , I think it's to help make the straps sit cleaner on the shoulder. As has been stated by everyone else, we are not saving any real $$ building our own plates. I'm fortunate in that I only have to pay for waterjet cutting of the plates but that will still be between $20 and $40 per plate.
I'm relatively new to diving and have never worn a back plate so I'm on unfamiliar ground, but I really like making my own stuff when possible and I'm having a lot of fun playing. I figured I would follow Huw's philosophy and share the design with the community. I'm always open to suggestions and will gladly change and share the designs with anyone interested.
Nice work - I like the 3D PDF. And thanks for following the ''share alike' philosophy.
There are a couple of little details you may want to look at - these would take about a second to show, but are a bit harder to describe, so forgive me if this gets a bit wordy...
Firstly, related to the top set of cam band slots: A harness normally starts off 'behind' the top of the plate, then comes through to the 'front', then folds through to the 'back' through the diagonal slots - so a normal harness sits inbetween the tank/s and the centre of the plate. To be able to use a set of cam band slots at the top of the plate, the harness needs to thread back through to the front of the plate, otherwise the harness blocks off the slots. Have a look at the third pic down on this page: Ali Single-tank SCUBA Backplate , and compare to the Halcyon plate in the pic below that. The top cam band slots then need to be at the same 'height' as the diagonal slots so this can happen. And you might want to make those cam band slots double width so two thicknesses of webbing (- the harness and cam band) can pass through.
Second, the reason for angling the shoulder straps out is to lessen twisting and wear of the webbing where it leaves the plate to come up over your shoulders, and make it sit more comfortably; you don't want to angle them out too much though, because then the fit could become less secure. I have mine angled 'out' 10 degrees from 'vertical' which works as a good compromise - most plates have them vertical or slightly angled in. This is determined partly by the angle of the diagonal slots - think of it like a beam of light reflecting off a mirror: if the mirror is at 45 degrees, the beam will be reflected to 90 degrees ('vertical'); if the mirror is tilted to 40 degrees the beam will be reflected to 80 degrees (or 10 degrees 'off vertical'). If the 'mirror' (slot edge) is at 40 degrees, the 'beam' (webbing) will move further out from the spine of the plate as it goes up, so, in order for the webbing to run smoothly the top shoulder slots also need to be moved further out from the spine, whereas you have yours vertically in line. So I'd suggest either moving your top slots out a little (half an inch/12mm or so), or changing the angle of your diagonal slots to 45 degrees.
Hope that is clear!
Cheers,
Huw
Last edited by huwporter; January 8th, 2012 at 08:15 PM.
Reason: Clarity.
Nice work - I like the 3D PDF. And thanks for following the ''share alike' philosophy.
There are a couple of little details you may want to look at - these would take about a second to show, but are a bit harder to describe, so forgive me if this gets a bit wordy...
Firstly, related to the top set of cam band slots: A harness normally starts off 'behind' the top of the plate, then comes through to the 'front', then folds through to the 'back' through the diagonal slots - so a normal harness sits inbetween the tank/s and the centre of the plate. To be able to use a set of cam band slots at the top of the plate, the harness needs to thread back through to the front of the plate, otherwise the harness blocks off the slots. Have a look at the third pic down on this page: Ali Single-tank SCUBA Backplate , and compare to the Halcyon plate in the pic below that. The top cam band slots then need to be at the same 'height' as the diagonal slots so this can happen. And you might want to make those cam band slots double width so two thicknesses of webbing (- the harness and cam band) can pass through.
Second, the reason for angling the shoulder straps out is to lessen twisting and wear of the webbing where it leaves the plate to come up over your shoulders, and make it sit more comfortably; you don't want to angle them out too much though, because then the fit could become less secure. I have mine angled 'out' 10 degrees from 'vertical' which works as a good compromise - most plates have them vertical or slightly angled in. This is determined partly by the angle of the diagonal slots - think of it like a beam of light reflecting off a mirror: if the mirror is at 45 degrees, the beam will be reflected to 90 degrees ('vertical'); if the mirror is tilted to 40 degrees the beam will be reflected to 80 degrees (or 10 degrees 'off vertical'). If the 'mirror' (slot edge) is at 40 degrees, the 'beam' (webbing) will move further out from the spine of the plate as it goes up, so, in order for the webbing to run smoothly the top shoulder slots also need to be moved further out from the spine, whereas you have yours vertically in line. So I'd suggest either moving your top slots out a little (half an inch/12mm or so), or changing the angle of your diagonal slots to 45 degrees.
Hope that is clear!
Cheers,
Huw
Thanks Huw what you wrote made perfect sense to me... I'll try to straighten this out today.
Also, I purchased an Al Halcyon plate and all of the webbing slots are around 1/4" (6mm) wide as opposed to 1/8" (3mm) I see on your template. Any reason for halving the width of the slots?
edit: Huw, I think the top slots may need to go in toward the center not out...
Last edited by edthesped; January 11th, 2012 at 03:51 PM.
Also, I purchased an Al Halcyon plate and all of the webbing slots are around 1/4" (6mm) wide as opposed to 1/8" (3mm) I see on your template. Any reason for halving the width of the slots?
It's not really critical - thinner slots hold the webbing more firmly in place, while the wider slots allow it a bit of lateral movement. Wider slots can definitely be easier to de-burr by hand!
Originally Posted by edthesped
edit: Huw, I think the top slots may need to go in toward the center not out...
If you leave the angle of the diagonals at 40 degrees, the top slots definitely move out - or, alternatively and perhaps better (because you don't want the shoulder straps to become too widely spaced) move the diagonals in. Have a look at the dimensions here: Backplate Template - the top slots start from 50mm out from the centre, the diagonals start from 36mm out. To calculate the differential needed, it'll be [the vertical distance between the slots * sin of the angle ] = [ 80mm*sin(10 degrees) ] = approx. 14mm.
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