DIY Backplate webbing slot sizes/angles

[aalbinger]

I saw a link to a backplate design in another thread.

http://www.scubaboard.com/attachment.php?s=&postid=112280

I was able to pick up a cutoff of 1/8" aluminum for peanuts at the local metal shop and I'm going to try make something mostly following that design.

My question is on the size and angles of the upper webbing slots. How do you get away putting 2 inch webbing through the top 1 3/4 inch slot? I know it is on the bend but I still can't figure out how you can get away with less than a 2 inch slot.

Also, it seems that some production backplages have the shoulder straps angled a bit at the top. Is this advisable?

-Andrew

 

[The Kraken]

Ya can't. It's a physical impossibility.

I've made several little gizmos over the years for my diving and I've made my own SS and Al back plates.

When I machined the slots for the webbing in my back plates, I measured the width of the webbing I was using and allowed .100" over for the slot width - ie if the webbing measured 2.00" then I cut the slots 2.100".

Additionally, if you measure the thickness of the webbing and machine your slots to a much closer fit than the slots you find in commercially manufactured you will find that your webbing won't slip as much.

As far as the angles of the top webbing slots go, that is predicated upon two things, the width of your shoulders/neck and how easy it is to turn the webbing 45 degrees.

Having the top slots angled permits an easier "turn" for the webbing. With the slots angled, you cross the straps so that they run diagonally from left to right and right to left.

You may want to take a piece of 1/8 plywood and experiment a bit with the angles to get the desired result.

None of my business, but do you think 1/8" Al is going to be thick enough?

 

[aalbinger]

Ya can't. It's a physical impossibility.

Excellent, I'm not losing my mind (at least not as quickly as I was beginning to think)!

As far as the angles of the top webbing slots go, that is predicated upon two things, the width of your shoulders/neck and how easy it is to turn the webbing 45 degrees.

Having the top slots angled permits an easier "turn" for the webbing. With the slots angled, you cross the straps so that they run diagonally from left to right and right to left.

You may want to take a piece of 1/8 plywood and experiment a bit with the angles to get the desired result.

That makes sense. I'll have to mock something up in plywood.

None of my business, but do you think 1/8" Al is going to be thick enough?

Well, good question. I know FredT has one available in 1/8" al. When I was rooting through the cutoff pile there was 1/4" and 1/8" in there. I couldn't easily flex a 22" X 15" piece of 1/8" aluminum using my hands and pressing it against something so I'm hoping it will be sturdy enough. If not, $10 worth of materials will be used to prove otherwise.

 

[The Kraken]

I think 1/8 may serve for a single tank application, but I don't think I would recommend it for doubles.

 

[cool_hardware52]

I saw a link to a backplate design in another thread.

http://www.scubaboard.com/attachment.php?s=&postid=112280

I was able to pick up a cutoff of 1/8" aluminum for peanuts at the local metal shop and I'm going to try make something mostly following that design.

My question is on the size and angles of the upper webbing slots. How do you get away putting 2 inch webbing through the top 1 3/4 inch slot? I know it is on the bend but I still can't figure out how you can get away with less than a 2 inch slot.

Also, it seems that some production backplages have the shoulder straps angled a bit at the top. Is this advisable?

-Andrew

1/8" al is fine. We even make a stainless reinforced plastic plate that is 1/8"

Slot lenght need match not only the webbing, i.e. 2", but also match the angle, i.e. if you are going to bend the webbing 45 degrees (like at the "crossover") slots at the top of the plate the slot needs to be 1.414 x 2" or ~ 2.8" long. Many commercial plates use 2" slots every where, this results in pinched and point loaded webbing.

Much webbing today is not 2" but is 50mm wide, or about 1.97" wide.


Good luck


Regards,



Tobin

 

[The Kraken]

Thanx, Tob, forgot to mention 2 onto the square root of 2 . . .

 

[The Kraken]

By the way, Tob, had the guys cut me some fantastic web keepers at the laser made of 12 gauge 316 stainless.

 

[cool_hardware52]

By the way, Tob, had the guys cut me some fantastic web keepers at the laser made of 12 gauge 316 stainless.

Lasers are big fun! That webbings not going anywhere with 12 ga keepers.


Regards,


Tobin

 

[The Kraken]

You bet. The webbing measured .090" and I had the slots cut .130". Had them cut some little specials for me for running a piece of bungie through to secure my flashlight on my shoulder strap and a couple of other neat thingies.

 

[JeffG]

I think 1/8 may serve for a single tank application, but I don't think I would recommend it for doubles.

No problems with 1/8 Alum with doubles.

I used ScottK's plate design (found in a zip attachment in his post) for my Alum plate. It has the 2" webslots.