Knighthawk double tank conversion

[bthalans]

Hello all:

I'm looking at a slow transition into the technical side of diving over the next year or two. I was looking at my knighthawk the other day and started thinking to myself that it shouldn't be terribly difficult to change out the old plastic back plate into an aluminum or stainless.

I know other people have thought about this, at least that's what I can see from the threads I've looked up on the bc up to this point. Those threads seem to quickly fall into people trashing each other on how much better their equipment is than yours.

I'm really just looking for ideas rather than trashing, I know I want to go into a bp/w setup eventually.

 

[SlowRain]

First thing to look at, and I don't know the answer to this question....Was the BC made to be convertible from single tank to handle doubles? I don't know what the lift capacity is...but having enough is a factor as well. I seem to remember when I went through advanced nitrox/deco class that one of the participants was diving a knighthawk and the instructor seemed to feel it didn't have enough lift. I don't know if your BC is under warranty, but alterations that you are talking about will probably void it if there is one.

I am sure there may well be other models out there, but the only back-inflate BC's I know of that are specifically manufactured to be able to handle both singles and doubles are Zeagles, and only certain models in their product line. I am sure there are probably more that I am not aware of. I would send scuba-pro an email...or perhaps someone else here (scubapro dealer?) knows, to answer the first question.

With Zeagles you perform the change by putting in a pair of wing retention bands, which holds the wing to the harness instead of the single tank bands which are removed. You then have to use either a backplate or a pair of smaller double supports and run the doubles through the BC and plate and bolt them together so that the backplate is against your back.

Having said all that...you can get a backplate and harness pretty cheap. The expensive part is the wing...depending on what brand and type you buy.

Honestly you could probably get through advanced nitrox/deco with what you have now if they teach it using large capacity singles...but I would really recommend on the side of safety that if you are going to be going to doubles that you get a rig designed for them rather than adapt something that may not be designed to handle the job.

 

[Peter_C]

Not worth doing. A backplate and wing can be had for pretty cheap used, or even new. Your Knighthawk is worth something. I sold mine for $400. Bought a brand new BP/W for $375. Then a second one for $250 used that I use with my doubles.

Check Discount Scuba Gear at DiveSports.com - Buy Scuba Diving Equipment & Snorkeling Equipment for some good deals.

Once you dive a BP/W you will never want to go back to a Knighthawk.

 

[Jim Baldwin]

Hello all:

I'm looking at a slow transition into the technical side of diving over the next year or two. I was looking at my knighthawk the other day and started thinking to myself that it shouldn't be terribly difficult to change out the old plastic back plate into an aluminum or stainless.

I know other people have thought about this, at least that's what I can see from the threads I've looked up on the bc up to this point. Those threads seem to quickly fall into people trashing each other on how much better their equipment is than yours.

I'm really just looking for ideas rather than trashing, I know I want to go into a bp/w setup eventually.

I have a Knighthawk and teach in it and it works fine for recreational scuba.

If you transition to doubles you need a setup specifically designed for doubles. Two inch harness material a hard plate, AL, plastic or stainless steel.

When you start training with doubles remember that the two plastic buckles at your chest will be all that will holding over a 100 pounds of steel on your back. Not counting any deco tanks or lights you might need to add.

Yes you can add a backplate with little effort. Undo the velcro attachment, unweave the belt and you can make a plate fit but you will still have a rec vest for a tech diving. When you're ready bite the bullet and buy a BP/W.

And you may also be hard pressed to actually find an instructor that will train you with this setup.

 

[Peter_C]

Check this deal out!
Highland Millworks Stainless Steel Backplate
Call Phil and ask what he can hook you up with for a complete package.

 

[D_B]

there is a thread that has pictures of NASA divers using Knighthawks with twin tanks, it is because of the stainless steel tank bands that have a curved piece under where they are joined together in the center (sorta like a gusset) this mounts to the backplate in the curve where the single tank would have been .. I have a set so I know that they exist (Butterfly Bands?)

but, you are probably going to want a BP/W , and it will grow with you no matter where your diving interests/training takes you

 

[Hoosier]

I don't think OP wanted to hear, "get an ordinary BP/W" in DIY sub-forum.

Do some "search" function.

It has been covered, excursively by me. I have put the double (AL80s) on Knighthawk and Classic plus. Even SP manual said that their BCD can hold upto 72CFs. Their lift capacity (on Medium size) is more than 40lb as I recall.

There are two ways you can mount the double tank.

1. Groove band (Hoop or butter fly band)

The doubles bands is made with a curved center section to fit the groove where the tank would rest in a single tank BC or backpack and most manufacturers accommodated this by providing 2 mounting holes in their backpacks. Many ordinary BCDs provide holes for this purpose.

2. BIBO Type band

I was in the market for the travel twin band. I also digged out the information about BIBO band and contacted the Italian/German companies that manufactured.

BIBO isn't secure enough because of the plastic middle part, so it haven't gotten a huge fan in EU market. I also contacted SP USA about this matter a long time ago.

Instead, you can use an "Aqua Explorer Ultimate Band" I am also using this one and very sturdy enough.


In sum, it is doable and possible to use the double on an ordinary SP BCD in a REC. RANGE.


EDIT:
IN ADDITION,

You can DIY band for your SP BCD. This subject has been covered as well.

 

[bthalans]

Thanks Hoosier, I have read most of your posts on the matter and agree that the bc's lift capacity is more than adequate. I believe mine is rated at 46 lbs since I have the L/XL version.

Have you tried swapping out the plastic backplate for a stainless one yet?

My BC is still under warranty so I'm not going to do anything too drastic (yet), but let's face it. Scuba diving technological advances have been achieved because people decided to modify their original equipment into something different. That's the whole point in me posting this in the DIY section.

 

[JeffG]

Some duct tape should help.

 

[Hoosier]

Have you tried swapping out the plastic backplate for a stainless one yet?

No. I didn't try it because if I wanted to swap BP, there was no point to add the double on the SP BCDs. I would like to use/try an ordinary BC. The plastic back plate (like SP one) has been used many years for a double tank rig. Believe it or not, it is still used, specially in the military diving.

If you want to swap BP, Dive Rite Transpac system can be a good example. You can use DR Transpac with/without the plate. You might need to get a little narrow BP, such as