<table class="tborder" border="0" cellspacing="0" cellpadding="5" width="100%" align="center"> <tbody> <tr valign="top"> <td class="alt2" width="175"> <div class="smallfont">
<div></div> </div> </td> <td class="alt1"> <table width="100%"> <tbody> <tr> <td width="90%"><! icon and title > <div class="smallfont">Discussion - Robbe Type XXI And The Cats Meow</div> </td> <td width="10%" align="right"><! End of show warned sign ></td> </tr> </tbody> </table> <hr size="1" style="color: #a7a7a7" /> <! message > <div>I have been busy as allways with this project to build a Type XXI by Robbe with my new Aquacasing and thaught I might share some of the advancements.

First I had to determine just how long the casing should be and how it should become acssesable for maintenance.

If one does not know how the XXI is originaly made with the supplied casing there are certain drawbacks to that designe that can be easily and economicly corrected with a casing that does not require a single large modified screw and most of all a stresed inner component tray that has been known to crack and fail if over tightened A major pain to repair that sinario and if it should fail while in the water well its all over,she will sink in a hurry.

So what I did was to make an Aquacasing that will fit the Robbe XXI and is almost as long as the original casing except that its far more safer to use and can go much deeper and most of all stays dry.

The pump ballst system uses my non pressurized ballast tank type that will give a scale dive and serface and hover operation for this great sub.
The single central tank houses the ballast pump that can run in the wet and is water coolled by the same water it pumps in and out.There is no need for a solinoid valve to keep water from entering the tank past the gear pump ,by using a certain type of filter that has just enugh tensile water restriction to prevent water from entering the tank.
See the operation of this very simple ballast system in this website.

Also in the tank is the hydraulic masts sytem that is also very simple and inexpensive to make and is very reliable and scale like right down to the noise of the pump and is very cool and variable speed.

Well by enlarging the diamiter of the ribs except for the last aft one to fit a 4 inch white PVC shd 20 or thin walled tube to huose the Aquacasing which just so happens to be just under 4 inches but to make a nice slidding out fit I had to round down just a 2 mm of the lugs on the casing and in it went with no snags.

To enlarge the ribs all at once just use a 0ne inch drum sandsing drum and drill clamped in a vice that has the original casing inserted so that the preciese alighnment of the ribs is set then remove the tube and sand or ream away till the 4 inch tube fits slightly lusly.

When the hull halfs are made with the ribs inplace but not dreid yet insert the 4 inch tube for a set alighnment and thats it.

The tube and Aquacasing come out all at once then the outer tube is slid off and then acsses to the Aquacasing is possible,thats it very simple and very solid costruction.

The 4 in tube is then set in place inside of the finished hull with a screw and a stop tab so that it is always set in place when removed and the ballance of the sub is not upset and retains the casing.The smaller last rib in the stern holds the end cap to perfection without any reaming just the vent tube indexis the casings rotation so that it will always be in the right possition for ballance and the masts thrust rod will pass at the right point.Very easy to do and works fantastic,much less mechanicals thatn my first XXI as seen later.

I which I had done the Aquacsing mod to the first one,now I have to do it to mine
Also the original setup riquired a seperate mini casing ahead of the main casing to operate the retraction and operation of the forward dive plains,this eliminates that problem which also requires external electrical wires for the servos inside,not very good.

The Aquacasing eliminates this by haveing a servo in the front cap and a bulkhead partition glued in place to make a mini dry space that is adjustable in size and has excelent acssesability, totaly watertight with just a magnetic connection to operate the plains via lincages or rods and cleeveses.

A gear pump the same type used threwuot the sub is placed out in the bow and it operates the retraction and extention, see vid of it on my sub ,very cool indeed and very scale like operation!

For the electrical charging there are 2 wires pos and neg that are acsesable from the front hatch and eliminates the need to remove the casing from the sub to charge,battery runs in the wet.
The wires are always hot yet are seperated and sealed by a simple solution ,a lenght of silicone large tubbing inserted over each exposed wire end both seals and seperates the wires and makes easy acsses to the circuit.

For the other 2 circuits like the dive plain retraction pump and nave lights a military speck watertight gold plated multypin rotary lock connector is used and they work very nice and I supply them if needed in a variety of number pins from 2 to 14.

The 4 inch tube is drilled with abunch of holes for both water to escape and air to escape and is very important for operation of the sub as traped air will cause an imballance,always watch for that in all builds and iliminate it.

One nice side effect of my ballast system is the bubbler effect that can be made to be seen as the sub dives and looks very scale like also ,a network of small tubes placed aruond the sub would work very nicely and would add to the effects.

Let me know if I can build one for you

Enjoy the vids!
<font color="#22229c">http://s82.photobucket.com/albums/j...=DSCF0001-3.flv</font>
<font color="#22229c">http://s82.photobucket.com/albums/j...=DSCF0001-2.flv</font>
Dave Amur Sub Yard </div> <! / message ><! attachments ></td> </tr> </tbody></table>