Experiences With The SeaDoo Bombardier DPV
Larry "Harris" Taylor, Ph.D.
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The equipment modifications and techniques described below have worked for us (as novices with this particular device) in our environment for the type of diving that we do. It may or may not be applicable for others. Divers must, as in all diving scenarios, determine if my comments are applicable to their diving situations
This article is intended only to document our experiences. Permission to quote from this article for sales or promotional purposes is expressly denied,
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Jump To: Buoyancy Gauges Navigational Nose Storage Harness Procedures
Surface Runs Underwater Runs Durations
Using It Dead Machine Techniques Potential Problems Wish List Conclusion
Before beginning, I should point out that I consider diver propulsion vehicles (DPVs) to be divided into two general classes: recreational and expedition. Recreational class machines are typically used for short duration in shallow, open water environments. Failure of the DPV is not an immediate emergency and these failures typically are handled by a disappointed, irritated ascent to the surface. Expedition class machines may be used in overhead environments, deeper water and long in-water times for advanced recreational, scientific, commercial, public safety or military diving. Failure of these devices is typically more severe. So, expedition class machines require enhanced performance and reliability, as well as some altered-from-open-water procedures. I will limit my comments in this article to the SeaDoo Bombardier as a recreational class machine.
As a general rule, I have been disappointed in sport diver's DPVs. They have been, for the most part, heavy boxes with handles and a prop with the hydrodynamic glide characteristics of a rock. Many have been very cumbersome and difficult to manipulate, especially out of the water. But this, historically, has been primarily a factor of cost and the limitations of available technology, particularly with the power supply. I first saw the Seadoo at the 2003 DEMA show. Its obvious departure from the "norm" caught my eye. (It has a fusiform shape ... the shape associated with swift underwater critters.) The eye-catching shape, a current need for a DPV (to assist in underwater wreck surveys and searching off-wreck bottom lands) and a very good show-special introductory price were the deciding factor in my obtaining two Bombardiers (Extended Range) DPVs for my personal use.
Before using the device in open water, I spent some time in a local pool to set buoyancy and gain familiarity with the DPV. As furnished by the manufacturer, the DPV is buoyant. For diving, the manufacturer recommends adding a few rocks to the buoyancy chamber. The intent is not to weight the DPV excessively, but to give it a tiny bit of weight such that it will be easier to handle at depth. I did not want to rely on adding rocks (concerned about scratching the interior, as well as being unsure of the effects from a shifting weight in the nose .. besides, some dive sites don't have rocks) to the chamber, Nor did I wish to play with various amounts of water (decreasing air space within the chamber) I wanted a relatively permanent don't-have-to-mess-with-it-on-the-dive-site type solution. So, I used a string of "handi-lead" secured with silicone aquarium cement.
Handi-lead strand & the buoyancy chamber
Handi-lead secured in the nose of the chamber
Securing the weights results in a constant center of mass without scratching the inside of the buoyancy chamber. In addition, using aquarium cement allows the weight to be removed at some future time. The device is so well balanced that it required only 177 grams of lead to overcome its natural buoyancy (for fresh water use, salt water will require a bit more weight.) Its buoyancy in fresh water is shown below.
Buoyancy of DPV with added weight
After several dives, one of the buoyancy chambers developed a leak and became progressively more heavy during the dive. This flaw was overcome by adding an O-ring to the foot of the screw threads of the chamber.
Many recreational DPV's do not have a provision for mounting gauges. This can be a problem because it is easy, when riding a DPV, to lose track of time/depth profiles. Since I prefer to know my in-water time and depth, I mounted an older model dive computer (an Orca Marathon) on the handle assembly. I used 4 polypropylene tie wraps to secure the computer to the DPV. Care should be taken to insure that the tie-wrap bands do not interfere with the operation of the speed controls.
The Marathon has large, easily-readable numbers and this allows easy access to time/depth information while keeping both hands on the DPV. It also has a long battery life since seconds are not displayed on the timer. Although this device is no longer manufactured, batteries are available from commercial battery vendors. (If these vendors are used, it is important to note the battery polarity since some of the newer batteries having the same electrical specifications have an opposite polarity.)
Determining direction of travel is often a problem while running a DPV.. Since both hands are on the DPV, it is sometimes inconvenient to check gauges and/or compass, particularly if all gauges are mounted within a console. Often, the only practical solution is to stop the DPV and hold it away from the body while the compass is used to determine direction. While not always a requirement, it is sometimes either convenient or essential to have directional information. For this purpose, we created a "navigational nose" (image, below left). This is an extra nose cone that has been fitted (using a brass bolt, a rubber grommet (to act as a space saver between compass and the outside shell of the DPV, a washer, a locking washer and a bolt to secure the assembly, image below, right) with a compass. We prefer the Suunto SK-7. While this compass is easily readable and has a side window for taking bearings, its most desirable feature is a compass card with wide range of motion (+/- 30 degrees tilt). This makes the compass an ideal diver's navigational tool, either on the console, the wrist, or mounted on the DPV. This assembly allows ease of visualization (directly below diver's face when under propulsion) while maintaining a compass reading that is unaffected by the running motor. The nose cone and the mounting hardware are shown below.
|The Nose Cone with SK-7 Compass||The "Hardware"|
When the nose cone is mounted on the DPV (shown below), the compass/computer combination allow hands free continual presentation of time, depth, and direction of travel information.
The addition of the navigational nose increases the versatility of the DPV in research/search operations. The ability to follow a course underwater allows for more rapid sampling along a bearing established form either a fixed location on the bottom or from shore. For generalized searching in open water, a center-of-search marker (see below) is established and a diver runs a compass course out from a central location for a predetermined time (like 1-10 minutes) and then returns via the reciprocal course to the center post . Once the center pole is reached, the search bearing is incremented (amount of angular increment will depend upon water visibility, the size of the object sought, the search area, and the total time allowed for the operation) and the search is repeated, Eventually, the entire area surrounding the center post is observed. We use an operational total search time of 40-45 minutes per battery. Our center pole (an eight foot aluminum rod with reflective & colored vinyl tape markings at 1' intervals, equipped a strobe light for enhanced visibility, and a surface float (SwimNoodles) to mark its location. A piece of rubber vacuum tubing serves as a handle to assist in pounding the pole into the bottom. The pole and the hammer are attached to carabineers with polypropylene tie-wraps.) is shown below. To facilitate manipulation of equipment, the components of the center-pole rod are separately clipped via locking carabineers to a 3.5 " (9 cm) brass ring. The small sledge hammer (to drive the pole into the bottom) is marked with yellow duct-tape bands to increase its underwater visibility. Lastly, a laminated business card (with note thanking divers for not removing) is added to encourage divers to leave the object on the bottom.
When directional information is not needed (like in DPV initial training or playing tourist around a large steel hull common in Great Lake Wrecks), we use the conventional nose. However, when it is necessary to have directional information as part of the dive, then we simply change nose cones.
The manufacturer suggests storing the DPV in the vertical position to minimize distortion of the prop shield. However, this is not always practical, particularly when transporting the DPV in the furnished carrying bag. After only a few dive trips, we noticed some prop scoring on the inside of this guard and a bit of deformation in the guard's circular shape. To minimize this shape deformation, we purchased foam "fun noodles" (a kids' pool toy) and cut them to 12" lengths. Three to five of these, held by a large twisty, provide a pad that minimizes weight on the guard. With time, the assembly compresses a bit to provide a snug fit.
|The Assembled Support||Supporting the DPV||Supporting the DPV|
The furnished battery charger, air pump and small parts fit nicely into an inexpensive 9 qt. Sterilite storage box (cover removed; below, left). Since I have extra batteries, I added a vinyl letter to each: this makes it easier to keep track of battery usage. The orientation of the letter makes proper placement of the battery during assembly (below, center) a tiny bit easier. Two batteries fit nicely (below, right) into the Dive-Rite weight carrying bag.
|Charger, Air Pump & Small Parts||Vinyl Letter||Carrying Batteries|
While the Seadoo is light and easily managed out of the water with one hand, there are times when it necessary to secure the DPV underwater while exiting. We use a harness (purchased at K-Mart) made from a deer-hunter's carcass-carrier. We added a Marine grade white Velcro lining to this harness to limit the opening after the DPV is placed within the loop. To use, the harness is slipped over the DPV, the loop closed with the Velcro and clipped to down-line. For some (depending on DPV buoyancy), adding a small weight will insure that the line stays vertical as the boat moves. The hand loop (surface end) and the loop for the underwater clip are eye-splices on either end of a 1/4" polypropylene line. We use different length lines (6, 10 and 15 feet) for each different DPV to minimize the chance of damage from underwater collisions that might occur from hanging multiple DPV's at the same depth under a moving vessel.
The DPV Harness
Using the Harness
The manufacturer claims 90 minutes dive duration with a maximum depth of 100 fsw. No battery powered diving device in my experience has ever lived up to advertised duration claims in the Great Lakes. This is probably a combination of over-zealous advertising, less than ideal ideal test conditions, and the cold water of the Great Lakes. (It is a well known chemical "rule-of-thumb" that most chemical reactions slow 50% for every 10 oC drop in temperature. This is a partial explanation for decreased cold-water performance of CO2 absorbents, all chemical batteries, and people.) So, we decided to test the advertised numbers in OUR DIVING ENVIRONMENT with our diving gear so that we would have some idea of in-water performance expectations before using the device for more serious play, as well as mission oriented surveys of underwater archeological sites.
I suspect that, in addition to water temperature, the variety of diver sizes and equipment configurations, as well as diving styles, will generate an enormous variability in time/duration using this device. So, the "numbers" I obtained are certainly not universal, but hopefully will provide some guidelines for use of the SeaDoo Bombardier. Divers, however, are reminded that these numbers are not rigorous and are determined by the interplay of environment, the diver's size and weight, and underwater drag of the equipment worn by the diver.
All testing was done with freshly charged batteries in water ranging from 50 to 68 oF in a local quarry. Although our test vehicles had the Marathon mounted on the handle, we used a dive watch (Casio G-shock) for more precise timing during speed measurements. Surface speeds were determined by a shore observer measuring the time it took to cover a 100' distance (surveyor's tape). Underwater speed was determined by running along a 150' measured line. We ran for about 20 feet to come to speed before entering the measured distance. Duration was measured by simply exploring the local quarry until the first motor shut-off. No attempt was made to measure the distance traveled, we simply "played" until the batteries died. Remember our intent was not to be scientifically rigorous, but to provide a set of operational guidelines for our diving.
The high speed continuous run was only done once. I found this speed to be a bit excessive (with a more limited bottom time) for me and my anticipated use, so no further continuous tests at the high speed were done. I consider access to higher speed a distinct advantage, but the decreased bottom time, for me, limits its use to short bursts, as needed.
The water surface temperature was 58 oF. Time is the average of two consecutive runs in opposite direction. The DPV was run for about 20 feet prior to entering the measured distance. The DPV was held below the diver such that the mounted dive computer display was readily visible. The diver was breathing through either the snorkel or scuba regulator so the head was in the water.
This is the result of using the SeaDoo as a Skin Diver with full wet suit at low speed.
This is the result of using the SeaDoo as a Skin Diver with full wet suit plus commercial chaps at low speed.
This is the result of using the SeaDoo as a Scuba Diver with full wet suit, tank, back-plate and rec wings, plus commercial chaps at low speed.
This is the result of using the SeaDoo as a Scuba Diver with full wet suit, tank, back-plate and Rec wings, plus commercial chaps at high speed.
This is the result (average of 4 runs) of using the SeaDoo as a Scuba Diver with full wet suit, tank, back-plate and rec wings, plus commercial chaps in water temperature of 58 oF.
Ave duration (4 trials each) at continuous low speed:
72 minutes with water temp in the high 60's. This corresponds to an approximate range of 1.35 miles (1953 yd; 1.17 nmi; 2.17 km)
52 minutes with water temp in the high 50's. This corresponds to an approximate range of 1.11 miles (2376 yd; 0.96 nmi; 1.79 km)
Duration (single trial) at continuous high speed:
38 minutes with water temp in the high 60's. This corresponds to an approximate range of 0.74 miles (1302 yd; 0.64 nmi; 1.19 km).
Regardless of the rationalization used to purchase a DPV, the primary purpose of recreational class machines is to have fun. There is definitely something special about moving through the water with a DPV. Using a DPV increases a diver's ability to experience more underwater wonderfulness. It also decreases air consumption because the DPV, rather than the diver, is doing the work of forward propulsion. Based on the "this is fun" criteria, the SeaDoo Bombardier is an absolute delight! It is distinctly not heavy (20.5 lbs; 9.30 kg on the surface with battery and mounted computer) and easy to handle. It tends to hold a straight line course (as long a both hands are on the device.) The speed controls are easy to manipulate, even with thick gloves. Two dives a day using the DPV at continuous low speed were not fatiguing to either the wrists or the shoulders, but the one continuous run at high speed did leave a noticeable muscle fatigue at the wrists and the shoulders. I particularly liked the ease of using the safety (The magnetic control splits and folds back on itself to avoid accidental activation of the motor.). The DPV seems to naturally hold a position under the diver (where it should be) to direct the thrust under, instead of straight-at, the diver. The machine is extremely maneuverable: crisp sharp turns were easily done.
Dead Machine Technique (Open Water)
All DPV's, regardless of care, will fail at some point in time. This can be from diver error, a manufacturing defect, exceeding design specs, collision, old age or simply a run of bad luck. As such, it is a good idea to have a contingency plan for machine (most likely a dead battery from using the device) failure. The light weight and easy handling of the Sea Doo is a definite asset in carrying the scooter for long distances with no power. We found the following open water procedure to work quite well:
The diver with the dead machine holds the DPV in one hand and places the other on the propelled diver's tank valve. This places the diver with the dead machine directly on the back (and slightly to the side) of the diver with the running machine. Once this position is established, the working DPV pulls both divers. In this position, both divers are free to kick.
Alternatively, if lines are available, the dead machine can be towed behind the divers.
My OPINION on potential problems with using this device:
1. The outside material is rather soft and scratches easily ... while multiple scratches may be anesthetically non-pleasing, the user has no clue as to potential, if any, compromises in structural integrity.
2. The "handles" used to secure the nose cone are soft plastic ... the internal notched-end life is uncertain and represents a potential source of failure. Users should carry a spare set of handles in case of breakage or loss.
Everything in diving is a risk/benefit ratio and divers should aim towards making positive benefits of a dive far exceed potential problems. I suspect the above problems are minor compared to the over all "wonderfulness" of this particular DPV. I have run across other divers using this device. We have each commented on the above problems, but the overall consensus is extremely favorable.
All underwater devices are compromises between manufacturing costs and desired features. Below is a list of items I, as a satisfied user, would like to see implemented to enhance my enjoyment of this particular product:
1. A self-powered, streamlined instrument cluster that would attach across the handle stabilizing bar (same place as my Marathon). I would like to see a minimum of battery power remaining, depth and time at-depth, and current local time gauges. Some directional indicator (tough 'cause of magnetic fields from motor) would be a real bonus.
2. Spare parts kit: extra nose-cone locking handles and 0-rings.
3. Outer hull scratch repair kit.
4. A more rigid prop protection assembly to minimize the deformation with repeated use.
5. More amp-hours for extended time underwater. (No matter what size battery is present, divers will always want more time!)
Bravo and kudos to the engineers at Daka Designs! This machine looks like it wants to move and it moves like it looks. It is a superb investment for those who simply want a "fun toy" as an aid to underwater touring. Plus, its light weight and ease of handling suggests it will be a useful adjunct for light duty mission oriented diving. (More on that in an upcoming article.)
Divers should be aware that each machine's speed/duration parameters are dependent on their diving equipment configuration and environmental parameters. The chaps I typically wear for suit protection (see River Diving: Equipment ) add a lot of drag and, as such, "my numbers" will most likely be less than most ... less drag (not wearing chaps ), less thermal protection and warmer water will most likely increase both underwater speed and duration.
Final Comment: In the days of my youth there was a song, "Poetry In Motion." That song is an apt description of diving with the SeaDoo Bombardier.
Jump To: Buoyancy Gauges Navigational Nose Storage Harness Procedures Surface Runs
Underwater Runs Underwater Runs Durations
Using It Dead Machine Techniques Potential Problems Wish List Conclusion
Home About "Harris" Articles War Stories Biblios Editorials Links Site Map Fini
Thanks to Tyler Schultz (Michigan Adventure Diving) &
All the staff at Portage Quarry, Ohio
for assistance in conducting these experiments
Sea Scooter Express for providing extra parts
Unit conversions were done with the Convert It Pro software application.
About The Author:
Larry "Harris" Taylor, Ph.D. is a biochemist and Diving Safety Coordinator at the University of Michigan. He has authored more than 100 scuba related articles. His personal dive library (See Alert Diver, Mar/Apr, 1997, p. 54) is considered one of the best recreational sources of information In North America.
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