Why is the H-plate unsuitable to twinset

[Tom_Ivan]

I'm making up a CAD drawing for a back plate. Was thinking of copying the H-plate by Huwporter but apparently this won't work for doubles.

Having never dived doubles I can't figure out why. If its a space problem between the tank bands and the back plate wouldn't a removable spacer inserted at the bolt holes fix that?

 

[guruboy]

Why don't you think it will work?

 

[cool_hardware52]

I'm making up a CAD drawing for a back plate. Was thinking of copying the H-plate by Huwporter but apparently this won't work for doubles.

Having never dived doubles I can't figure out why. If its a space problem between the tank bands and the back plate wouldn't a removable spacer inserted at the bolt holes fix that?

I recommend speaking with who ever you plan to have break the plate after you cut it out. Show them the bends you want and the spacing. Make sure they have the punches and dies required. Simple press break tooling runs $30-60 per *inch* more for custom profiles.

Bends that are close together require narrow dies, and narrow dies require more tonnage. Make sure they have enough machine too.

BTW, the DSS design results a similar low profile position for singles with excellent stability and still allows use with doubles....

Good luck,

Tobin

 

[Tom_Ivan]

Why don't you think it will work?

It was mentioned that it wouldn't in another scubaboard post somewhere from a few years ago. I can't find the original post anymore and thought it best not to dredge up an old topic anyway. Huwporter also states on his website that its a dedicated singles plate.

BTW, the DSS design....

You talking about these designs?

 

[tbone1004]

@Tom_Ivan it is likely that the bend is too shallow combined with the rounded spine to accept normal doubles bolt lengths. If you mounted that plate to doubles, the wing nuts would be sticking out and dig into your spine/exposure protection.

If you want a low profile design, the DSS plates are really fantastic for singles, and they have no problem mounting to doubles

 

[cool_hardware52]

You talking about these designs?

Those are my designs. Single tank offset is influenced by a number of additive factors.

The first is over all plate bend. DSS plates have a much flatter bend than most plates originally designed to mount doubles.

The depth of the center channel. DSS plates have a conventional style center channel, but it is far shallower that most plates originally designed to mount doubles.

Wing grommets. Most wings use a #3 grommet and a piece of resin reinforced webbing in the center panel. These grommets + Webbing are .25" thick. These grommets act to space the STA up away from the center channel of the back plate.

STAs all have some thickness, typically about 1/16, and they are designed so the cambands pass between the sta and the cylinder. Camband webbing is ~1/8" thick. STA's also require mounting bolts, typically a domed headed carriage bolt. These heads are also between the cylinder and the back plate. Often at least one camband passed over the head of these bolts, usually both do.

Starting at the back plate. Metal wing grommet, .25", STA metal, .06, Bolt head .18, Camband , .12 Total .61 or almost 5/8"

DSS designs us no STA, and our wings have no metal grommets. The molded rubber elements in the center panel of our wings are less than 1/8" thick.

Add to that a flatter plate, and much shallower center channel and the cylinder offset with a single tank is often at least an inch less than designs based on a doubles plate, that was *adapted* for use with singles by slapping on a Single Tank Adapter......

Having said that 95+% of the time I use mine with doubles.

Tobin

 

[Bison Ravi]

I have the last Huw porter plate he sold (i believe). Its really really nice and low profile, perfect for single tank but might be a bit shallow for doubles as tbone1004 said.

 

[Scared Silly]

@Tom_Ivan it is likely that the bend is too shallow combined with the rounded spine to accept normal doubles bolt lengths. If you mounted that plate to doubles, the wing nuts would be sticking out and dig into your spine/exposure protection.

I recently changed out bolts on a several of our doubles because they were too long for small diameter cylinders. Not really any big deal. That said one can also just add a stopper nut so the back plate does not get pushed so far back. Probably the easiest if one is uses a set of double with different back plates.

 

[tbone1004]

I recently changed out bolts on a several of our doubles because they were too long for small diameter cylinders. Not really any big deal. That said one can also just add a stopper nut so the back plate does not get pushed so far back. Probably the easiest if one is uses a set of double with different back plates.

it doesn't look like the bolt length would be the issue. If you look at the two pictures below, the issue is that there is no space for the wing nuts. When the bolt comes through the spine of the H-plate, it is sticking out, long enough to engage at least a washer and a wing nut, preferably a washer, lock washer, and wing nut. You can see the Halcyon plate with just a wing nut on the backplate. The spine is recessed in that backplate to allow for this without come into the area where the divers back is going to be. You put a wing not on the spine of the H-plate, regardless of how long the bolt is, and you're going to be in some serious pain, and your drysuit or wetsuit will likely have a nice 11" on center pair of holes in them at the end of the dive.

 

[Doby45]

You could use something like this.. But swap the cap nuts for wing nuts..