This DPV unit will perform similar to commercial units. Before starting your project read this manual thoroughly!

Parts needed 1. 8 Inch PVC pipe, don't waste your time at Home Depot or Lowes, this item can only be found at

plumbing supply stores. 2. 12-volt selenoid, find them at auto parts stores, junk yards, I bought mine on eBay for $6 plus $7 S&H. 3. Two 12 volt motorcycle batteries, stock numbers change over the years, the batteries need to put out

22 amp/ hour, must be 7" long, 4" wide, and 6 1/4" high, and weigh 16 pounds. 4. Button with rubber boot attached, you find these at any marine supply store. 5. Fiberglass kit, check marine supply stores, epoxy kit recommended. 6. Aluminum sheet 1/16" thick 7. Trolling motor, Motorguide brand is recommended, you can use anything up to 40 Lb thrust, 24 volt. All you'll need is the lower end, auction off the controls. This contains a PWM unit sought after by robot builders. Also the transom mount might be worth selling. This part contains the clamps which rust and seize up rendering the motor useless. I'm sure owners of such motors will be looking to buy a replacement mount Choosing A Motor You can choose any electric motor up to a 40 lb 24 volts. Remember when using a 24 volt motor on a 12 volt power supply torque will be lost, the thrust put out by such a motor would probably be comparable to a 12 volt 20 lb thrust motor. High-powered motors are heavier, more expensive, and will run down the battery faster. It's best to stick to a 12 volt trolling motor 25 lb thrust or less, anything more would be overkill. These plans are built around a Motorguide trolling motor, other brands will work with these plans, but some modification may be necessary. Some trolling motors have the conduit attached on the front of the lower end. With these motors the electrical connections will be inside the hull and no water proofing is needed, the bulkhead will be installed center of such motors. To install them you'll have to remove the propeller.

Build Your Own Underwater Scooter Scuba Tow

DPV

There are a few models that have the conduit attaching in the very center. These will attach similar to the Motorguide, but the motor mount will be closer to the bulkhead making it very hard to do any work or perform maintenance.

Fabrication First: Purchase the PVC tubing section. You’ll notice there is printing running along its length, use this as a centerline along the top. Next: find the distance around the circumference, and divide into four equal parts. This way you'll have four reference points. You'll need these referrence points during construction. Use the inside of the tube as a template to build two bulkheads. You may use 3/4 inch plywood, or if using epoxy resin, you may also use pink foam insulation. Nose Section/ Ballast Tank This part can be built using different methods we recommend using a 7 3/4" salad bowl storage container (such as Tupperware). Toss out the lid you will not need it. The outer lip should fit the flange of the PVC pipe just right. These containers are usually not meant for the kind of installation and must be reinforced or they will crack at the slightest impact. This is where the fiberglass kit comes in, but before you start you must purchase 2 plastic nut and bolt sets. Size is not critical, but length of the bold should be kept to a minimum. Now drill two holes opposite of each other, these holes must be large enough to insert the bolt through, and should be as close to the rim as possible. Next insert the bolt thru the first hole hand tighten the nut until it will not turn anymore. Secure the nut using 5 minute epoxy or other suitable adhesive. Don't get any glue on the threads! Now apply some clear plastic tape over the exposed part of the bolt, and do same with the other nut and bolt set. You are now ready to fiberglass. Mix the chemicals according to the manufacturer's instructions. Brush on a layer of resin, and lay your first layer of fiberglass, brush on a second layer and add a second fiberglass, finish this off with a coating of resin. You should have your bulkheads coated in the same manner at this time. This will save you time and money, for resin is hard to clean and brushes are usually ruined. Once the resin has cured cut off any excess, and sand down fiberglass to the edge of the bowl. Using a screwdriver remove the bolts , now cut off the excess fiberglass formed over the plastic tape, and replace the bolts. Your ballast tank is now done. Attach it to the finished tube section using black silicone, and four screws. The black silicone make it watertight, the screws make the set up permanent. Kort Nozzle

The Kort Nozzle can be fabricated of 1/16 inch aluminum sheet metal. To form the shape you need to draw two semicircles on a sheet of card stock Start at the bottom of the sheet, loop a 16 inch string to a nail or pin at the other end you should loop a pencil to the string. Proceed to draw the circle. Now get a longer string, 20 inches and do the same. This semicircle needs to be at least 27 inches long. Use this as a template to cut the sheet metal. To form the conical shape you need special tooling not available to backyard builders To have it shaped into a cone you should take it to a metal shop. Some trade schools will actually do the job at no charge, if you don't mind waiting, a commercial shop will do it in the same day, but there will be a nominal fee. Hull Sections The hull sections consist of two sections of 8 inch PVC pipe, approximately 15 1/2 inches long. The end sections need to be smooth and square cut. The back end should be tapered, you can create this effect by filing, or grinding, using a small grinder. Next step is cutting the water intake holes. Using the reference points, draw a parallel line to the reference line one inch on either side. Use a different colored maker, from the reference points, so as to avoid any confusion. Having done this on all four reference points, your next task is to draw a line parallel to the back end of the scooter. This line should be 2 inches away from the tapered edge and should be drawn between the lines you just finished. Do not cross over any reference points! Having completed the first set of lines draw a second set four inches away from the tapered edge. You should now have four rectangular shapes drawn on your scooter's hull. Now cut them out and round off all edges using a file. The Kort nozzle will install over these openings so as to prevent diver contact with the propeller.

Next step is installing the four latches. In conjunction with the four latches is the aluminum ring. The aluminum ring installs on the inside of the front section. This ring acts as a reinforcement for the latches, Facilitates joining sections, and most important it holds the rubber seal. You may have this ring made, but I found it easy to work with when using thin stock aluminum strap at least 1 1/2" wide. You'll have to curve one edge on the strap, and loop the strap inside the PVC pipe. Make sure the strap fits snuggly the inside of the hull By now you should have cut and fiber glassed the two bulkheads. Begin by installing the front section bulkhead first. Drill four holes 1" from the edge of the PVC pipe, using the reference points as a guide. Unless you care about aesthetics countersink your screws. Set the bulkhead in place so the four holes line up in the center, and fasten it using tapered screws. The last step is to seal the bulkhead using black silicone. Place a bead on the outer edge of the bulkhead, do this on both sides. Installing the rear section bulkhead takes a little more planning and work, using a circle cutter bore a hole for the motor in the very center. Now drill two holes for the wires. Install the rear bulkhead using the same process as before, the position will vary according to motor size, and brand. Consult the section 'Choosing A Motor' and the blueprints for details. Clearance between the forward wood blocks and the front bulkhead should be 7", the bolts used to secure the battery should be 6", anything bigger will make installation removal impossible. For this application a carriage bolt is recommended. The bolt should be permanently fastened to the aluminum strap using a nut. To adjust the position of the battery loosen or tighten the second set of bolts using a ratchet set with an extension. As for the rear set of bolts you may use a different type but the size should be same as the forward adjusting bolt. This makes convenient not having to change ratchet sizes. The battery tray consists of a flat piece of wood, with the long sides cut at a 45 degree angle so as to increase the surface area in contact with the hull, this will help it adhere to the hull. On the long side uncut bolt tow aluminum angled stock. This will act as a rail to facilitate balancing the batteries. You may add some axle grease to the rails if the batteries are still hard to move. The batteries were strapped together using duct tape. This made it easier to load them and sliding them out during charging. The wires were tucked under the tape and then looped together using electrical tape so as to prevent tangling. The battery retainer consists of a flat length of wood with aluminum strap attached to the adjusting bolts. In case the batteries are hard to fit into the hull, don’t panic clip off both top corners of the wood. If the batteries still don’t fit clip some more off the corners. Lastly you need to attach the wooden keel and kort nozzle. The keel was water proofed with several layers of polyurethane. Two holes were drilled on the hull, to fasten the keel with two screws. Prior to installation the keel was given a coat on the longest side of thickened resin. This was achieved by adding glass particles to the resin. You may substitute glass particles with a wide range of thickeners, check manufacturers’ recommendations. You may also use any strong adhesive, but water proof it by painting over it prior to submerging your DPV. You’ll need to drill two small holes in the keel to accommodate the motor mount bolts. Installing the kort nozzle is a matter of trial and error. The angle on the keel was left intentionally high (45 degrees) and later shaved down to mate the kort nozzle. The kort nozzle was trimmed off were the ends overlapped. A small wood screw was used to keep it from slipping off. Once the nozzle was centered on the hull a layer of fiberglass was applied to the inner side and then the hull was flipped over so as to do the same on the outer surface. To prevent any resin from ruining the hull a sheet of newspaper was wrapped over the hull. Electrical System

A typical selenoid installation Detail motor You'll need the same gauge wire for the high power connections, as used by the manufacturer in the lower end, black and red conductors for the ground and positive power supply. For the low power connections it iseasier to use thinner wiring. To minimize electrical problems, braided wire was twisted into loops slightly larger than the bolts on the selenoid and batteries, these were heated with a soldering iron, and filled with solder. Amazingly braided wire will soak up molten solder. First let's start with the selenoid. Most likely the one you'll purchase will have only 3 connections points. There should be 2 large bolts this is where the 12 volts charge from battery and the motor will connect. There should be a third bolt much smaller, this should connect directly to the push button. The last connection is the ground. Most manufacturers will not provide you with one. The ground is the chassis on the vehicle. Since we are using a plastic hull you'll have to loop and solder a wire to one of the bolts. The other end of this wire should be connected to the negative battery terminal. If your local marine supply store does not carry the recommended type button, MSC has several. I recommend MSC's 3JC12 bronze nut bonded to black silicone boot, also # 3HZ98 which fits buttons 3HZ97, these parts cost $12.08, $11.98, $12.12 respectively. You may find a suitable button at Radio Shack for less, but these will break easy and repairing them would be impossible as we are encasing them in epoxy. All electrical connections, exposed wires are to be coated over using DIP IT, or Plasticizer, (see my previous file for diluting these compounds and the dangers of explosion) this will prevent any sparks, and subsequent explosion if hydrogen is present. It will also prevent shorts and corrosion in wiring exposed to salt water. Sealing off external wiring is easy first drill holes big enough to slip the wires thru. next mix a small batch of 5 minute epoxy, and dab it inside of the hole, around the cables, and pull the out so as to fill in the hole with epoxy. to seal off the wires externally brush on DIP IT or Plasticizer, you may also use black silicone. After you built the motor mount, disconnect the motor from the controls. This will change according model, but most likely all you have to do is loosen a bolt on the plastic case, where the shaft/ conduit attaches. Remove the transom mount from the shaft, and using a pipe wrench around the shaft carefully loosen the shaft from the motor. To assemble the new motor mount simply turn both pieces until you start feeling some resistance. Remember the pr drilled holes for the wires should face away from the propeller.

You need a plug for the next step. This can be any material that is easy to work with, a cork will do fine, it must fit the pipe nipple snuggly. Cut the cork in half, and drill two holes .Now slip both wires thru the plug and push it down the pipe nipple past the pre drilled holes, and slip both wires through holes in the nipple. And lastly encase the wires in 5 minute epoxy, this will prevent any water from penetrating the motor. After the epoxy hardens, brush on some diluted Dip It or Plasticizer, so as to prevent the nipple from

rusting, and to seal off the threads, thereby making the motor watertight. Handles The handles are made of 3/4 inch metal conduit. If you have large hands use 1 inch stock. Two equal lengths (approximately 5“)were welded together to form a 90 degree angle One handle had two holes drilled for wiring, but if your button is off to one side you’ll have to drill a hole large enough to install it. This handle will need a washer welded to hold the button. You should have a large fender nut drilled 120 degrees (3 holes) or 90 degrees (4 holes) apart. Try bending the washer slightly by tapping the middle with the ends resting on a section of channel, the idea here is to curve this washer so that it’s shape matches the hull‘s. The handle with the button is filled with epoxy so as to make the button waterproof. Do this after the handle is bolted to the hull. Both handles should be given a couple of coats of diluted Dip It or Plasticizer, to prevent corrosion, and create a good gripping surface, this will also help seal the button. Finishing Up The kort nozzle enhances performance , and serves as a propeller guard, shrouding the water intakes. if you followed my instructions, but the propeller still poses a danger as the rear of the DPV is wide open. To prevent any contact with the propeller I bolted on a grill from an indoor portable fan. The hull was sanded down and the motor was wrapped with newspapers. a coat of OSHA approved paint (yellow) was used to give it a million dollar look. Testing Before you can dive using the DPV you’ll have to make some adjustments. First balance the vehicle by moving the batteries forward or back. Next you’ll have to let some water into the ballast tank, to make it neutrally buoyant ( Slightly positive). Remember salt water is more buoyant than fresh water, therefore you’ll need more ballast. To fill the tanks loosen both screws until you see bubbles emerging from the top. The vehicle is ready for diving when the hull is mostly submerged, it should feel weightless and when loose it should gently float to the surface. Charging To charge the batteries open the DPV, by popping open the hasps. Separate the two halves and loosen the rear adjusting bolts, and slide the batteries out. So far the prototype has been charged using a regular battery charger, but future models will employ a plug system hooked to the charger, and will also feature dc adapter so as to be able to charge the DPV from a car’s or boat’s cigarette lighter (power) outlet.

Water intakes were cut using a circle cutter. Graphics appear sideways to facilitate printing.

TURNING A MOTORGUIDE MOTOR INTO A DEEP SEA WORKHORSE

1. Trolling motors as watertight to one additional atmosphere beyond surface pressure: a depth of 33 feet. People have been known to operate them to about 100 feet without modifications to the lower end unit, and the failure rate at that depth is about 4 to 5 percent. Still, the company won't stand behind that, so 33 feet is the specified depth limit for seal integrity, according to manufacturer. Doubling the number of seals won't ensure operations at greater depths, because pressure sufficient to implode the outer seal will also be enough to implode the inner seal, too. (Since they are side by side on the shaft, there is no cumulative increase in their depth resistant integrity. When the water gets past one, it will immediately bring it's pressure to bear against the other, which will at that time be operating alone, and have no greater strength than it's failed counterpart.) 2. Motors run fine and have excellent depth compensation qualities when the lower end is filled with transformer oil. The fluid is of a fine enough viscosity that reductions in armature RPM are not a problem. Make sure the case is completely topped off and free of any air voids. Another fluid that has been used with some success is hydraulic fluid used in automotive jacks. This fluid is easily bought anywhere auto parts are sold. There may be some draw backs to using it, remember the fluid was not meant to be used with electrical parts and may over time cause damage to the motor.

To remove the nose cone loosen the prop nut by turning counter clockwise. Your prop nut may be different than the one pictured.

Next loosen the two bolts on the outer circle. The 3 sections can now be seperated, all we need is the nose cone try to leave the other sections intact.

Now drill and tap a hole. Next re-install the cone and tighten the bolts. Then re-attach the prop. You are now ready to fill the motor with your fluid of choice. Once the motor has been filled with fluid slip an o-ring through a bolt. Choose a bolt that is approximately the same thickness as the nose cone. Lubricate the threads with pipe dope. Insert the bolt in the hole you made earlier and tighten gently so as not to ruin the threads.

Periodically inspect the fluid for discoloration. This may indicate the presence of water. Change seals if this happens.

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