David Merriman’s 57″ Seaview part 9A
In honor of David Merriman’s birthday, I’m reposting the final segment of the Seaview article.
Well, here we are. Part-9, the concluding installment of the SEAVIEW article. Finally! Time to wrap up and prepare to launch into another multi-installment article … that upcoming piece dealing with a build-up of the Rick Teskey FLYING SUBMARINE (FS-1) kit.
I’ve taught you how to take the fine DeBoer Hulls fifty-seven inch long SEAVIEW kit and improve it – turning it not only into a stunning display piece, but also a reasonably well running practical model r/c submarine. Now that we’re near the end of this saga it’s time to tie up the loose ends. We’ll look at the practical design shortcomings unique to the SEAVIEW; the pre-operating, operating, and post- operating tasks demanded by such a model; and a quick peep at the principles of operation of a practical submarine.
I take care to perform the initial sea-trials at a lake site I know and am comfortable with. That means water I’ve walked through to neck height. A site that I’ve surveyed for weeds and sunken items that would present an entrapment hazard. You might be surprised at what’s laying on the bottom, just out of sight beneath the surface: I’ve found shopping carts, tires, ten-speed bicycles, entire rolls of carpeting, etc., Items that could damage and/or entrap a submerged model submarine.
I search for launching and recovery sites that are sandy, no significant rocks protruding that might scare the bottom of the model submarine. R/c submarines are heavy – a submerged submarine contains not only the structure and equipment needed to make it work, but also the water that fills the unused portions of the open hull. That means the model has a great deal of inertia – it won’t come gently to a stop when it hits something. No. When it hits something, it keeps plowing into the obstacle, suffering extensive hull scaring. Site selection is critical. Not just any body of fresh water will do.
PRE-OPERATING, OPERATING, AND POST OPERATING TASKS
During those initial outings to the lake, as I rung out the SEAVIEW during sea-trials, I took pains to develop a three-part maintenance and adjustment methodology that would insure that the SEAVIEW would receive all the preservation, maintenance, and replenishment services needed to keep the vehicle in top operating condition. I devised three specific documents: the pre-mission, mission, and post-mission maintenance checklists. Each was a chronological listing of the procedures, list of tools, consumables, and safety cautions needing to be performed and observed. One checklist prior to taking the model to the lake, one checklist to be performed at the lake, and another checklist dealing with those preservation and safeing steps performed once the model had been returned to the shop after a days play. I think it instructive here to summarize each checklist:
Pre-mission The WTC and battery are checked first, before integration with the hull. The battery is taken off charge and its Voltage measured (being a lead/acid type battery, the gel-cell units I use are kept on constant ‘trickle charge’). The WTC cylinder is opened up by popping off the after bulkhead that mounts all the mechanicals that drive and operate the vehicle. The bulkheads sealing o-ring is checked clean, and then lubricated with silicon grease. The push rod and drive shaft cup-seals are lubricated with light machine oil, as are the two gear reduction drives. All mechanical and electrical connections are checked tight.
The SEAVIEW and the two major components that make it operational, the WTC and gel-cell battery. The rest of the models interior is free flooding. A ‘wet-hull’ type r/c submarine model like this is relatively light of weight out of the water as opposed to a comparable dry-hull type r/c submarine. Out of water weight is low because of the free-flooding interior.
Only after the submarine is placed in the water and water is permitted to fill the interior, does it take on the same weight as a dry-hull type counterpart. Wet-hull type r/c submarines are easier for we older folk to schlep around between shop, van, and launching site. That’s old-age talking, people.
The on-board gas bottle within the WTC’s ballast tank is charged with liquid ‘Propel’ (air-brush propellant). It is the release of Propel gas that empties the ballast tank of water when the ‘blow’ command is sent from the transmitter (or the on-board safety circuit if it detects a ‘loss of signal’).
The motor bulkhead is then re-inserted into the after end of the clear Lexan watertight cylinder. After waiting five-minutes the pressure-relief valve, mounted on the face of the motor bulkhead, is opened. As I do that I listen for an audible rush of escaping air (slightly compressed as the bulkhead was pressed into place against the cylinder). That sound indicates that the cylinder is indeed, ‘watertight’. The transmitter is turned on, the WTC is connected to the gel-cell battery, and all systems are checked for correct operation (rudder, stern plane, sailplane, ballast system, and throttle).
The battery and WTC are set aside.
Mission Thankfully, the at-the-lake maintenance chores were found to be no more involved than for any other r/c submarine – just the occasional battery change and re-charging of the ballast systems on-board gas bottle. During these periodic servicing chores, I invert the model and inspect the WTC for any water that may have crept into the cylinder.
The client for this turnkey job (I was commissioned to build this SEAVIEW, it’s not part of my personal fleet, Damnit!) built and provided a display stand for his SEAVIEW. When not at the lake terrorizing the local duck population this submarine model will be found on display within the customer’s house. Note the devices and support equipment on the bench under the model.
The SEAVIEW is taken off its display stand, mounted onto its work-stand, opened up, and the two pump-jet rotors way back in the stern are given a drop of light machine oil at their bearing points. The control linkage clevises also receive a drop of oil while working back there. Control surfaces are checked by hand for unbinding operation.
Upon satisfactory testing of the WTC, battery, and inspection of the SEAVIEW interior, the three units are united. The battery and WTC are installed within the SEAVIEW hull, each sitting upon a foundation and secured with rubber bands. The two drive shafts and three control surface push rods are made up to the WTC. Powered up once again, at the transmitter I check for correct motion and unobstructed rotation of sailplanes, stern planes, rudders, and pump-jet rotors, on the lookout for any binding of the various linkages and drive shafts. The running lights (bow, sail, and Cadillac fins) are operated to check for burned bulbs.
With all pre-mission checks successfully completed, the WTC is disconnected from the battery, the transmitter turned off, The superstructure of the SEAVIEW attached to the hull, the field box outfitted, and everything is staged into the family van for the trip to the lake.
Here is the SEAVIEW model, the upper superstructure with the attached sail removed for servicing. This shot was taken while I and other model boater’s put on a show at the Mariner’s Museum, Newport News, Virginia. Normal at-site maintenance and checkout chores (mission tasks) are accomplished after removing the superstructure piece, accessing the interior to work on the WTC or replace the gel-cell type propulsion/control battery.
If need be, further access is afford (usually only in the workshop) by removing the stern section of the model, accessing the stern control surface linkages and pump-jet units.
Post-mission Post-mission maintenance with the SEAVIEW, like other r/c submarines, is the most time consuming and important in-shop task. It is during this session that preventive maintenance and structure preservation chores occupy the careful builder/operator: The WTC and battery are removed, the interior of the SEAVIEW hosed out with fresh water, dried with low pressure air, and the lights briefly hooked up to assure no bulbs burned out. Oil is dropped onto all control surface bell cranks and bearing points, and the pump-jet rotor bearings get another squirt of lubricant. The empty SEAVIEW hull is then assembled and put back on its display base and put back on exhibit.
The battery is made up to the WTC and a complete systems check conducted – any problems are addressed. Any water leaks that developed during operation are identified and fixed. The battery is disconnected and (along with replacement batteries) put on charge. The ballast tank on-board bottle is vented off, and the WTC is put into safe storage.
No, r/c submarines are not plug-and-play type items; dusted off and played with on a whim; these are not playthings for the inattentive. A day’s fun at the lake is accompanied by a systematic, careful, time-consuming checkout period, before, during, and after use.
I’m not usually so grumpy looking … honest! At the Mariner’s Museum boat show. This initial effort at weathering was way over done (I’m a proud graduate of the Ed Miarecki school of painting and refinishing, if you must know – sorry, Ed. Couldn’t resist!); too much contrast between the white and the simulated panel lines. I later toned down the underside of the SEAVIEW model with several well-thinned shots of white.
Much better looking now. Note the rectangular openings at the front of the propulsion tube. These provide water to the intake side of the internal pump-jets. These intakes are augmented by the large opening in the bottom of the hull (the mini-sub access hatch) and flood-drain holes along the length of the hull. I could not have done that with a dry-hull type submarine.
PRACTICAL DESIGN SHORTCOMINGS OF THE SEAVIEW DESIGN
As I mentioned in part-8, the SEAVIEW revealed nasty inherent design flaws (the wrongly stated manta-fin rolling problem aside) that evidence themselves when the model operates beneath the surface of the water.
The two big ‘V’ arranged Cadillac fins overhanging the stern work to over stabilize the boat about the yaw axis while submerged … even the three big rudders, two of them benefiting from the high velocity flow from the propulsion nozzles, were not enough to adequately overcome the stabilizers ‘weather cocking’ effect underwater.
Turning radius above the surface (with the fins sticking in the air) is good. Turning radius submerged (with the fins in the water flow) is awful!
Additionally, those huge ‘V’ arranged Cadillac fins contribute to another stability problem: In a submerged high-rate turn they produce a torsional moment that rolls the boat into the turn – that torque, when coupled with that of the sails torsional force, is enough to roll the boat so far over that rudder deflection begins to contributes a ‘down pitch’ component; as the boat rolls nearly on its side the rudders act to pull the stern up and the boat heads to the bottom, out of control.
As pointed out above, the manta-fins induce a stabilizing force about the roll axis, negating a good portion of the ‘V’ shaped Cadillac fin/sail inboard torsion/rolling force. Without the manta-fins the SEAVIEW would be an impractical, almost impossible to control r/c submarine.
Nearly all modern American combat attack submarines employ a set of downward canted (anhedral) stabilizers at the stern (situated between the horizontal surfaces and lower rudder). Their primary function is to serve as foundations from which either evasion devices or towed cables are launched or streamed clear of the propeller/pump-jet disc. The secondary purpose of the stern mounted anhedral stabilizers is to generate a torsional force (created as the boat’s angle of attack about the yaw axis increases) to counter the boats tendency to roll inboard in a turn. On a ‘real’ submarine this unwanted inboard rolling moment originates solely with the sail and a big reason that today’s submarine sail structures are kept as short and low of area as possible. Sail structures are either well faired in to the hull (as practiced by the Russian ‘Ruben’ design bureau) or are so shaped as to limit the structures ability to produce lateral ‘lift’ at a high yaw angle of attack (American LOS ANGELES class).
With the SEAVIEW we are cursed with three surfaces that produce a unified torsional moment in a turn: the large sail and two upward angled fins as the stern.
The rolling, and reduced turn rate experienced by the SEAVIEW underwater was observed and noted. Like any other type submarine I drive, I first work out the maximum underwater speed I can attain and still maintain depth control once the rudder is put hard over. Same test and observations as I work the horizontal control surfaced to maintain or change depth. The objective during these sea-trial activities is to determine the submarines ‘performance envelop’. I determine the edges of that envelop and try not to exceed them during normal vehicle operation. Sea-trials are more than working out the mechanical bugs and trimming the boat, it is also that initial period of operation where you, the Driver, learn what you can and cannot do with the vehicle above and below the surface.
Sometimes, sea-trials are not a happy time between the operator and his new ride. For example:
On the maiden dive of the SEAVIEW model, after a few circles and figure-of-eight turns on the surface to check out the running gear, I commanded an ‘all-stop’ and waited for the big model to coast to a stop. I then commanded a vent of the ballast tank and took the SEAVIEW to submerged trim. With only an inch of the sail projecting above the water (the boat is trimmed a tad light in submerged trim) I was ready to run the model submerged for the first time … little did I know! I slowly advanced the throttle and noted a slight pitch-down of the model, so I threw both transmitter sticks full over to command full rise on the sailplanes and full rise on the stern planes. No change! Even with a low throttle setting the SEAVIEW, both sets of horizontal planes on ‘rise’, continued to pitch down to a dangerously high angle. It was headed to the bottom! Only full astern and ballast blow commands arrested the dive and got the boat back to the surface, in a flurry of foaming water and swirling thick gas vapor – I just managed to keep the SEAVIEW’s bow out of the lake mud. An embarrassing performance to say the least. What went wrong?!
After a reflective pause, I repeated the maneuver. Same thing! Again and again, each time I tried it, the boat dove to the bottom at a severe down angle. Obviously there was something intrinsically wrong with the design – it was not a problem of static trim or improper control surface response to commands, I checked all that. No matter how much ‘up’ I cranked into the stern planes and sailplanes, the SEAVIEW model, once the ballast tank was full and the throttle advanced and the boat got some way on, it would pitch down.
Back at the shop and a good hard look at the SEAVIEW bow in profile. OK, I see … how could I miss that! It became obvious then what was going on: In profile the bow of the SEAVIEW is in the shape of a wedge which assured that water passing over it has to produce a downward force at the bow. The faster the boat goes, the more pronounced this pitch-down moment. As I demonstrated at the lake, the sailplanes and stern planes did not have the authority to overcome the designs inherent tendency to pitch down when advancing submerged.
The fix was to install permanent vanes within each propulsion nozzle, their job to direct the exhausted water upward, countering the pitching moment at the bow. In water tests verified that the fixed vanes countered the bow induced pitching problem throughout the SEAVIEW’s speed regime, net angle change as a consequence of submerged speed was zero. Mission accomplished! But, keep in mind that the two pitching forces (shape of the hull forward, the fixed vanes in the nozzles aft) are directed down; the net force on the vehicle is a downward one. However, this downward force acting on the submerged submarine is of low magnitude and is easily countered by operating the boat at a slight up-angle or simply by cranking in a bit of ‘rise’ on the sailplanes.
After installation of the fixed vanes in the nozzles depth control of the SEAVIEW became no more difficult than driving a ‘traditional’ type r/c submarine.
The SEAVIEW, during sea-trials, with sailplanes set slightly to dive, sinks beneath the surface as its ballast tank fills with water. As is my practice, I build ‘soft’ type ballast systems: the tank is open at the bottom and fills only after a single vent valve atop the tank is opened, permitting the gas within the tank to vent out, letting water in. The boat is trimmed with fixed lead weight and buoyant foam so that a full ballast tank takes on just the right amount of weight to get the submarine to a nearly perfect neutrally buoyant condition when submerged.
On to part 9B