DIY Kydex backplate

[victorzamora]

First, a lay-up of carbon and a 3-4mm plywood would be more than sufficient for doubles (strength-wise) but would be vulnerable to banging at the edges of the plate. I'd do biased reinforcement on the edges, personally, but there are several options that would work. Either way, I'd never make it out of just carbon. In the end, the weight savings would be minimal if you had a composite layup like that.
A core made of 3-4mm plywood would be very hard to manufacture with sufficient strength as to not create huge stress concentrations right at the weakest part of the core. Also, not only would the edges be weak, but wherever you placed holes (for either attachments for doubles or worse: attachment for single's wing sex screws as well as two cambands) would be very likely to delaminate. Even with reinforcing strips, even short-term loading of force on the plate will cause delamination after a few dives. With a wooden core, delamination would be the VERY abrupt end of the backplate's life span. A better core, if this was going to be attempted regardless, I think, would be a nomex honeycomb. However, that would necessitate a vacuum pump.


Second, I agree you will get the best results if you use one but a vacuum system it's far from a necessity. I have several items (though not Backplates, kayak paddles, kayaks, etc) I've made without one that have stood up to hard use for 10 years now. It will reduce weight of the resin and get better bonding but it's not a requirement at all. That said, it's not that hard to put one together with a home vacuum to at least get some level of improvement over a hand lay-up.
Something that has to support a force (like kayak paddles or kayaks) spread over a large distance is VASTLY different from the point-forces applied onto a backplate. Scuba tanks put a large force focused on a relatively small area. On top of that, the stress placed on the backplate by the harness is also putting point loads over a small area. Right where the harness goes from the center grommet into the shoulder harness, there is very little material. Something as soft as thin plywood simply won't hold up to much diving...especially when you're jumping in to water.

Third, other than the cost of carbon and resin, it wouldn't really be that expensive when considering how much you'd actually need. That said, I wouldn't go out and buy it just for this project, personally. I would certainly give it a try if I had it on hand and was inclined to build a project like this. In fact I seriously considered doing just that last year but decided I didn't really see the point of a light-weight plate once I got used to my SS.Good carbon will be "expensive"....but you're right, it's not atrociously expensive. However, getting any sort of performance out of a wood-core carbon composite backplate with any sort of longevity practically requires a good vacuum pump, vacuum bag, and everything that goes with it.

I've done a lot of work with composites in the field of Aerospace Engineering with UAV's over a wide range of sizes, but I do have a narrow view of composites....so I have experience, but I still may be wrong. I simply don't see it being a good idea at all.

 

[fjpatrum]

I've done a lot of work with composites in the field of Aerospace Engineering with UAV's over a wide range of sizes, but I do have a narrow view of composites....so I have experience, but I still may be wrong. I simply don't see it being a good idea at all.

I think you're probably right about the core being better with some other material, I just tend to think it's a lot stronger than expected. I've seen shear and tensile tests of a glass/wood/glass lam that were incredibly strong, even at point loads. You're probably right that any delam would be catastrophic, though, I don't think it would be sudden and unexpected. I suspect you'd get fair warning but would have a "major blowout" if it wasn't tended to immediately. A honeycomb core or some other similarly strong structure I think would lose any real weight savings, as I said. I don't have a lot of experience building those, though, just using them and we only see failures when we get planes and pods (also UAVs) back from the field.

You've convinced me, though, I may have to do one just to see how it would work.

 

[Nemrod]

Why core it? I think three or four layers of carbon and glass ought to do it. I do have a vacuum pump that I built. It can pull near 30 inches, even has an auto cycle and a vacuum reserve tank. I have made surfboards, telescope tubes and made a few aircraft repairs with it. As well, I built another portable pump system at work for aircraft composite repairs. Been to a few schools also.

But, without the core, the weight savings would not be there, it might look cool but aluminum is probably better for this application.

I actually have several pieces of cf fabric. It is my intention to someday use an old Voit Snugpack as the mold and pull a cf plate from it with my vacuum pump. But I am in no hurry. I have another telescope tube for a Carton lens I happened upon to build first.

N

 

[fjpatrum]

Why core it? I think three or four layers of carbon and glass ought to do it. I do have a vacuum pump that I built. It can pull near 30 inches, even has an auto cycle and a vacuum reserve tank. I have made surfboards, telescope tubes and made a few aircraft repairs with it. As well, I built another portable pump system at work for aircraft composite repairs. Been to a few schools also.

But, without the core, the weight savings would not be there, it might look cool but aluminum is probably better for this application.

I actually have several pieces of cf fabric. It is my intention to someday use an old Voit Snugpack as the mold and pull a cf plate from it with my vacuum pump. But I am in no hurry. I have another telescope tube for a Carton lens I happened upon to build first.

N

Personally I don't think you'd get the rigidity you'd need from just carbon and glass without any bends. Flat carbon or fiberglass, especially in a light lay-up, are quite flexible. I have a 5 layer fiberglass (4 or 6 oz, I don't remember which) paddle blade, about the same length as a plate, slightly narrower, with a felt core (just for a bright color and a little stiffness) that I can nearly fold in half by hand. The carbon would add some stiffness, especially if you had something like a 12oz material, but like you said, no weight savings at that point.

I do think it would look really awesome though. Like I said, I have some 12 oz CF that I've been saving up so maybe I'll go ahead and make a plate after all. Just to see how well it works.

 

[SangP]

I agree the cool factor outweighs a lot of the negatives n a clear plate with fg would b even cooler!

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[lucca brassi]

carbon backplate @ STA on ebay

 

[mrarmyant]

HOLY OLD THREAD BATMAN. How did this hold up?