PART V. HULL CONSTRUCTION AND ENGINEERING INSTALLATION, ELCO 77-FOOT MTB, ELCO 80-FOOT MTB
Page Chapter 1. Elco 77-foot MTB 359-388 Hull framing 359-362 Planking 362-363 Interior strengthening 363 Gas tank installation 363-364 Canopy construction 364 Dock strengthenings 364 Fire fighting equipment 364 Drainage 364-365 Packard engines 366 Engineering installation 366-368 Propeller shafts and struts 368 Chapter 2. Elco 80-foot MTB 369-371 Hull framing 369-371 Planking 371 Canopy construction 371 Engineering installation 371 Chapter 3. Hull repairs 372 Canopy cracks 372 Damaged planks 372-373 Broken frames 373-375 Damaged struts, shafts 375 Removal and reinstallation of propellers 375 Replacing rubber strut bearings 375-377 Chapter1. ELCO 77-FOOT MTB
(A) The 77-foot MTB's were built by Elco Naval Division, Bayonne, N. J. They are 77 feet over-all length with a beam of 20 feet. The boats are a V-bottom, hard chine design with a draft ranging from 21/2 feet forward to 41/2 feet aft, and have a loaded displacement of approximately 46 tons. A hard chine design has very little V-shape on its bottom whereas a soft chine boat has a considerable V which gives a sharper entrance into the seas. The hard chine design gives greater speed due to the fact that it causes the boat to plane but it also causes the boats to be
extremely wet in choppy or very rough weather, particularly at slow speeds. The wetness of this type and its lack of sea-keeping qualities has resulted in our later, more modern designs which have a softer chine.
Figure 49.The first step in the construction of an MTB is the assembly of the prefabricated main frames on a building jig which is a double 12- by 12-inch wooden base extending the entire length of the boat. The frames are built of wood braced with plywood
Figure 50.
angles. The bottoms of frames 1 to 34 are laminated of spruce, white oak, and mahogany; the upper part of frames 1 to 34 and the entire frame from 35 to 69 are made of mahogany. All the frame joints are secured with marine glue and screws. Bulkheads are merely frames, properly braced and covered on both sides with fir plywood. They are, for all practical purposes, watertight.The spruce keel, to which is spliced to an oak stem, is put in place and secured with brass bolts. The chine, which is the hull member forming the joint between the bottom of the hull and the sides, is made of spruce and also bolted on. Spruce diagonal frames on the hull sides and longitudinal battens on the bottom are notched into the main frames and fastened with brass screws. Intermediate frames between the main frames are similarly installed in the three forward compartments. The hull is now ready for planking.
(B) The planking is in two layers both made of mahogany boards 6 inches wide. Both layers above the chine are 3/8 inch thick; on the bottom, the inner layer is 3/8 inch, the outer layer 7/16 inch. The two layers are laid on diagonally opposite to each other with sheets of airplane fabric laid in marine glue in-between. The
Figure 51.
planks are fastened to the main frames below the water line with monel screws and above the waterline with brass screws. The fastenings to the diagonals, battens, intermediate frames and securing the planks to each other where there are no frames are copper nails riveted over burrs.(C) When planking is complete, the hull is turned over and the inside work begun. Longitudinal girders made of mahogany covered with plywood run from bulkheads 1, 2, and 3 back to the stern and give the boat a great deal of its stiffness. Cedar clamps or battens are screwed to the inside of the frames on the
Figure 52.sides of the hull and run from bulkhead No. 1 to the stern. The main deck frames are notched, spruce deck longitudinals are screwed in place and a 5/8-inch mahogany plywood deck is put on. The deck is secured to the hull with plywood knees between each frame. The knees are bolted to the deck and to the covering board on top, and to the planking, gunwale, and guard clamp on the sides. An oak rub strake outside the gunwale and an oak chine guard make the outer hull work complete. (See illustration.)
(D) The gasoline tanks are mounted on padded frames and secured in place with padded metal straps. Each tank is provided with its own separate fill pipe and each one vents immediately below the gunwale on the outside of the hull. The engines are
mounted on bed frames which are secured to the longitudinal girder. Shims are provided for aligning the engines properly.(E) The canopy is framed with spruce with all corners and angle joints made of mahogany and fastened with screws and glue. The frame is covered, inside and out, with light plywood which is secured with glue. The voids between frames are filled with rubber insulating material. For convenience in removal of tanks and engines, the canopy is made in three sections, each of which can be removed. The forward or pilot-house section contains the sheet aluminum cockpit and the controls. The midship section contains the gun turrets which are plywood except for a thin metal shield on the top. The after, or engine-room section, is very easily removable and is fitted with a hatch large enough to permit the passage of a reverse gear, V-drive or auxiliary generator. All canopy joints are covered with tape made of airplane fabric to make them watertight and metal clamps are used to hold the two sections together.
(F) A great amount of deck cracking was experienced in the 77-foot MTB's due to the fact that the deck did not have as much flexibility as the hull. This weakness was eliminated by the installation of a hollow fir "strongback" which is a longitudinal stiffener on the deck from forward of the pilothouse to the lazarette hatch on both sides of the canopy. A tendency for the canopy to crack was likewise eliminated by the "strongbacks" and a slightly heavier construction and modified design of the canopy.
(G) The boat's fire-fighting equipment consists of several small hand CO
2 extinguishers and an automatic Lux CO 2 system. The two tanks in the Lux system are located in the starboard officer's stateroom with heat actuators in the tank room and engine room which will cause the system to discharge upon a sudden increase in temperature. A manual control is provided on the deck immediately forward of the canopy hatch. (H) Scuppers are provided to drain water on deck or overboard from the ports, clear-view screens and cockpit. However, the main drainage employs the use of hand bilge pumps and automatic bilge bailers. There are two hand bilge pumps, one under the ladder leading down into the crew's living compartment and the other on the forward starboard side of the center engine. The forward pump may be used to pump either the crew's
Figure 54.
head, crew's quarters, and officer's quarters; the after pump may be used for either the tank compartment, engine room, or lazarette. Bilge bailers utilize the suction created by the motion of the water over a scoop in the bottom of the boat while underway to pump water from the bilges. They are entirely automatic in operation and commence pumping at a speed of about 12 knots. There are six bilge bailers located as follows: one in the lazarette, two aft in the engine room, one forward in the engine room with a suction in the tank compartment, one in the officer's quarters, and one in the crew's compartment.(I) The power plant of the Elco 77-foot MTB consists of three 1,350-horsepower Packard 4M2500 engines. The engine itself can be studied thoroughly in the Packard Operations Manual. The engineering installation has been developed by the boat builder and requires considerable study to understand completely.
(J) The cooling water and lubricating oil in the engines are cooled by use of a heat exchanger in which the cooling medium is sea water. The heat exchanger is a metal cylinder divided into two sections with 50 to 751/4-inch outside diameter copper tubes inside through which salt water flows. The oil and water flow over the tubes, each in its separate section, and are cooled by a constant flow of sea water. Thermostats bypass the heat exchanger in the oil system until the temperature reaches 140°-145° F.
Sea water is supplied to the heat exchanger by an inlet and outlet scoop under the bottom of the hull. There are two scoops for each heat exchanger and each of them is equipped with a valve, the controls for which are located on the inboard side of each wing engine. In normal underway operation, the outlet scoops are opened wide and temperature is controlled by varying the opening of the inlet scoop. While idling at the dock, however, water is circulated through the heat exchanger by the engine saltwater pump, the intake for which is located in the outlet side of the heat exchanger. To insure the pump pulling water through the heat exchanger, when idling or maneuvering at the dock, it is necessary to close the outlet scoop and open the inlet scoop wide.
The lubricating oil system utilizes a separate 30-gallon tank for each engine equipped with a gage glass to indicate the oil level. Only 24 to 26 gallons of 1,100 (S. A. E. 50) oil are put in the tank. Oil is pumped from the engine by the scavenger pump through an
Figure 55.
on-edge type oil filter (which must be cleaned daily by turning the handle once), cooled by the heat exchanger, and then back to the oil tank.The water system of each engine is provided with an expansion tank which is installed higher than any part of the engine. A gage glass shows the amount of water in the tank. The main purpose of the expansion tank is to provide a level for the water system although it does replace water lost through leaks, evaporation, etc. Cooling water after it has been through the engine, does not return to the expansion tank. It is cooled by the heat exchanger and goes directly back to the engine.
As the engines are installed in the boat, the two wing engines are apparently installed backwards, the reverse gear being towards the bow of the boat. To drive the propeller shafts which run aft, a gear box called a V drive is used. The V drive consists of two cone-shaped gears with roller bearings at each journal. The engine drives one gear which drives the other which, in turn, drives the propeller. Cooling is accomplished by use of water jackets through which sea water is pumped by the engine salt-water pump. A separate oil tank for each V drive is located in the bilge under the unit. Oil is put in the housing of the V drive itself and its level is determined by a bayonet type gage on the filler plug. Lubrication is furnished by an oil pump driven by the unit itself.
(K) The 2-inch Monel propeller shafts go through the hull through a unit called the stern tube. The stern tube is a bronze casting with a flax-packed gland on the inboard end which keeps the water out of the hull. A packing nut tightens or loosens the packing. Cooling is obtained by circulating salt water with a small scoop. A bronze bushing is lubricated by a permanently installed grease gun.
There are eight bronze struts bolted to the bottom of the boat, three for each wing engine shaft and two for the center engine shaft. Each strut is equipped with a rubber bearing which is a pressure fit. When a bearing becomes worn enough to permit shaft vibration, the whole bearing must be replaced.
The three propellers are bronze and keyed to the shaft with a bronze key. Great care must be exercised in the installation of propellers to be certain that they are all the way "home" on the taper and not riding the key or off center.
Chapter2. ELCO 80-FOOT MTB's
(A) The 80-foot MTB's are constructed similarly to the 77-foot boats in that transverse frames are prefabricated and placed upside down on a building jig. There are 69 frames and the transom spaced differently depending on the load to be carried. The bottoms of the frames from the bow aft to the tank compartment are laminated of spruce, white oak, and mahogany. The remainder of the frames and the upper part of the forward frames are made of mahogany with a narrow white oak capping on the inner side.
After the frames are in place, longitudinal battens are let into the main frames from the bow to the forward end of the tank compartment where they are scarfed into a solid layer of mahogany planking which extends under the entire tank compartment. Battens are similarly scarfed into the after end of the tank-compartment inner planking, but from that point to the transom the battens run on top of the frames with spruce spacers in between forming a solid flat foundation for the planking from the forward end of the tank compartment to the stern
Secondary transverse frames and topside diagonal frames are similar to the 77-foot boats except that secondary frames are found in various parts of the boat where strain is excessive as well as in the forward three compartments. In the place of longitudinal deck battens, two longitudinal clamps are installed from bow to stern on either side of the deck openings for the superstructure. In addition, all the deck space between the superstructure openings has a longitudinal clamp running on the keel line. An 8-inch coaming is installed above the deck from the forward end of the superstructure to the after end of the engine room hatch This construction replaces the deck strongbacks installed above the deck on the boats of MTB Ron Four. Diagonal wooden pads and stainless steel webbing under the torpedo tube foundations complete the deck framing.
Intercostal plywood knees which were used to tie in the deck and hull on the 77-foot MTB's have been discarded. Both
Figure 56.
deck and planking are bolted to a single continuous wooden member the entire length of the hull. The construction appears to be very strong and should give no difficulty. The deck is of double-planked mahogany, 3/8-inch upper and 5/16-inch lower, with marine glue and airplane fabric between the plank layers. The planks are laid fore and aft, each lower plank acting as a batten for the upper planks and fastened throughout, with brass screws.(B)The planking is double diagonal mahogany laid in the same manner as on the 77-foot MTB's. The total thickness of the topside planking is 3/4-inch, inner 5/16-inch, outer 7/16-inch. The bottom planking totals 15/16-inch; inner, 7/16-inch; outer, 1/2-inch. The fastenings to the main frames are Monel screws below the waterline and brass screws above and copper rivets or clinched nails are used for secondary fastenings. Due to the war requirements of copper, brass, and Monel, it is certain that, in production completed after the summer of 1942, all fastenings will be galvanized steel.
(C) The deck houses are built of spruce frames with curved mahogany corners and covered on both sides with light plywood. The space between the frames in the superstructure is insulated with cork and the whole house is covered with airplane fabric, doped and painted. Hatches are provided to remove gas tanks and engines.
Potable water is carried in a single 200-gallon tank located in the bilge under the chart room. The CO
2 tanks are also installed in the same location with manual releases on the port side aft of the bridge and outside of the engine room hatch. No automatic discharge for the fire extinguisher system is provided. (D) The engineering installation is almost the same as the 77-foot MTB's. The heat exchanger, oil tank, and expansion tank for the center engine are in the port side of the engine room: those for the wing engines are in the conventional location. A seat for the engineer is provided on the starboard engine from which he can start the engines, observe the instrument panel, control the spark and scoops, and shift clutches. A square hatch with hold-down bolts may be lifted off to remove engines.
Chapter3. HULL REPAIRS
(A) One of the most common hull casualties is a crack in the superstructure or canopy. Such damage has little effect on the structure of the boat itself but does cause leaks. Unless the canopy frame itself is broken, covering the crack with a patch of aircraft fabric, doped and painted, is sufficient to stop the leak. If the framing is damaged, corrosion resisting steel patches not more than 0.060-inch thick should be put on both inside and outside of the canopy. White lead and canvas should be laid under the patches to make it watertight. In canopy, as well as other repairs to the boats, care must be taken to keep the bonding system intact and, if new material is installed, it should be connected to the boats' bonding system.
(B) Small gouges in the hull, if not through the outer planking, can best be repaired by putting on several thin layers of plastic wood and sanding it off flush with the planking. More serious cuts or cracks require the replacement of planks, although
Figure 57.
it is usually necessary to replace only the outer layer. It is generally considered advisable to replace entire planks but if the damage is slight, sections of planks may be installed. When installing only sections of planks, the seams where the new patches butt against the old planking must not be in a straight line but should be staggered.Care should be taken in the removal of damaged planks from Elco MTB's to damage as little as possible the aircraft fabric between the planks. If the fabric is not seriously damaged, a coat of marine glue should be applied and the new planking installed over the old fabric. If it is damaged considerably, the fabric must be removed and now fabric installed. All screw holes should be plugged with wooden pegs and the old fastenings duplicated as nearly as possible. The new planks must be very carefully fitted but if a slightly open seam is unavoidable, it should be filled with plastic wood. The new planking, when completed, must be sanded down to a very smooth finish.
(C) Main frames break occasionally and, being almost impossible to remove, they must be repaired in the boat. The most
Figure 58.
effective frame repair is the installation of two heavy plywood "sister frames" extending on both sides of the break as far as possible. The two plywood pieces are cut to the shape of the frame, placed on both sides of it at the break and through-bolted with brass or galvanized bolts. It is advisable to use fairly large bolts and few of them because the fewer holes drilled in the frame, the less the chances are of the break recurring.Cracked battens do not materially weaken the construction of the boat unless there are several of them cracked. A successful method of patching such casualties is to place a similar sized batten over the damaged member and secure it to the main frames with metal angles. The new batten should also be screwed down to the damaged one.
Figure 59.The rub strake and chine cap are put on the boat to prevent damage to vital parts of its construction when the boat makes contact with the dock or floating objects. Because of their purpose both members require fairly frequent replacement. The damaged pieces should be taken out in entire sections as they were built on the boat, the screw holes plugged, and new sections installed. In the shaping of a new chine cap, particular care must be taken to have the bottom of the chine extend at least
1/8 inch below the bottom of the cap to prevent the force of the water from ripping the cap off.(D) MTB's frequently suffer casualties to their struts, shafts, and propellers due to contact with the bottom or a floating object. A bent shaft can be corrected only by replacing it with a new shaft. Monel shafts are somewhat flexible but a shaft should never be reinstalled unless it is tested with a dial indicator or some other accurate method and determined to be true.
A bent strut must be removed and straightened or replaced with a new one. To replace a strut, it must first be determined whether the shaft is bent and if it is, it must be replaced. The after part of the shaft must be blocked up so it is perfectly straight. This can be checked with a dial indicator. The new strut is then placed on the shaft and the wooden strut pad planed down until the shaft has the same "pinch" all around the rubber bearing when the strut is tightly held against the pad. The strut bolts should then be installed, tightened and the whole job tested again for accuracy of alignment.
(E) To remove a damaged propeller, the cotter key and lock nut should be removed and the shaft nut backed off about 1/2 inch. The propeller puller should be put on and tightened up to the point where it puts a strain on the propeller. Further tightening will break the puller. The blades of the propeller should then be struck sharp blows with a hammer which will "shiver" the propeller loose from the shaft. The shaft nut and propeller may then be removed.
To install a new propeller, the brass key should be removed from the shaft and the propeller pushed "home" on the taper. Mark the forward end of the propeller hub on the shaft and remove the propeller. Insert the key in the keyway on the shaft and put the propeller on. The propeller must come up to its previous position on the shaft or it is "riding" the key, thus unbalancing the propeller and perhaps shearing off the key. When the propeller is in the proper position, the shaft nut, lock nut, and cotter key should be installed on the shaft.
(F) Rubber strut bearings have a long life but they will eventually wear out and should be replaced when they do because a worn strut bearing causes a great deal of vibration. Merely because the shaft compresses the bottom of the bearing and does not
Figure 60.
touch the top when examined out of water does not mean that the bearing is worn out. The weight and flexibility of the shaft will cause that. The shaft should be blocked up until it is straight and the bearing examined. If the shaft does not "pinch" the rubber slightly around its entire circumference, the bearing should be replaced. The rubber bearing is vulcanized to a bronze bushing which is a push fit in the strut and secured with set screws, and therefore considerable pressure is required to remove it. A bearing puller has been designed which permits the removal of the old bearing and the installation of the new one without removing the shaft. (See illustration.)
MTB RON Form No. 11
U. S. S. PT ___________ Date ________________
HULL CHECK OFF LIST The following inspections will be made weekly under the supervision of the boat captain and "OK" put in the "Condition" column if satisfactory and "NG" if unsatisfactory. In any item marked "NG," give reasons in the "Remarks" column. These lists will be kept in each boat available for inspection by the squadron commander or first lieutenant.
Condition Remarks 1. Bilges (cleanliness and dryness). 2. Self-bailer shut-off. 3. Self-bailer intake strainer 4. Self-bailer anti-siphon hole. 5. Hand bilge pumps 6. Weigh fire extinguishers 7. Weigh Lux tanks 8. Check Lux release valves 9. Fresh-water tanks and piping. 10. Fresh-water pumps 11. Steering chain and sprocket lubrication. 12. Gemmler gear lubrication 13. Tiller bar lubrication 14. Main and secondary frames 15. Planking 16. Deck 17. Superstructure 18. Girders and deck longitudinals. 19. Paint (topside) 20. Paint (below decks) 21. Deck fittings (cleats, chocks, etc. ) 22. Stowage and condition of ground tackle. 23. Stowage of ammunition and ordnance gear. 24. Stowage of gear in lazarette.
Condition Remarks 25. Tightness of all hatches, ports, etc. 26.Rub strake 27.Lines and fenders 28. 20 m/m. and torpedo tube deck pads and framing. 29.Blackout system 30.Bonding system
WHEN BOAT IS HAULED
1.Propellers 2. Rudders 3. Shafts 4. Struts 5. Rubber bearings 6. Scoops 7. Planking 8. Chine cap and chine
THE LAWS OF THE NAVY
Now these are laws of the Navy,
Unwritten and varied they be;
And he that is wise will observe them,
Going down in his ship to the sea;
As naught may outrun the destroyer,
Even so with the law and its grip,
For the strength of the ship is the Service,
And the strength of the Service, the ship.Take heed what ye say of your seniors,
Be your words spoken softly or plain,
Lest a bird of the air tell the matter,
And so ye shall hear it again.If ye labour from morn until even'
And meet with reproof for your toil,
It is well that the guns be humbled,
The compressor must check the recoil.On the strength of one link in the cable,
Dependeth the might of the chain.
Who knows when thou mayest be tested?
So live that thou bearest the strain!When the ship that is tired returneth,
With the signs of the sea showing plain,
Men place her in dock for a season,
And her speed she reneweth again.So shalt thou, lest perchance thou grow weary
In the uttermost parts of the sea,
Pray for leave, for the good of the Service,
As much and as oft as may be.
Count not upon certain promotion,
But rather to gain it aspire;
Though the sight-line end on the target,
There cometh, perchance, a misfire.If ye win through an Arctic ice floe,
Unmentioned at home in the Press,
Heed it not, no man seeth the piston,
But it driveth the ship none the less.Can'st follow the track of the dolphin
Or tell where the sea swallows roam;
Where Leviathan taketh his pastime;
What ocean he calleth his home?
Even so with the words of thy seniors,
And the orders those words shall convey.
Every law is as naught beside this one--
"Thou shalt not criticize, but obey!"Saith the wise, "How may I know their purpose?"
Then acts without wherefore or why.
Stays the fool but one moment to question.
And the chance of his life passeth by.Do they growl? It is well: Be thou silent,
So that work goeth forward amain;
Lo, the gun throws her shot to a hair's breadth
And shouteth, yet none shall complain.
Do they growl and the work be retarded?
It is ill, speak, whatever their rank;
The half-loaded gun also shouteth,
But can she pierce armor with blank?Doth the funnels make war with the paintwork?
Do the decks to the cannon complain?
Nay, they know that some soap or a scraper
Unites them as brothers again.
So ye, being Heads of Departments,
Do your growl with a smile on your lip,
Lest ye strive and in anger be parted,
And lessen the might of your ship.
Dost think, in a moment of anger,
'Tis well with thy seniors to fight?
They prosper, who burn in the morning,
The letters they wrote overnight;For some there be, shelved and forgotten,
With nothing to thank for their fate,
Save that (on a half-sheet of foolscap),
Which a fool "Had the honor to state--."Dost deem that thy vessel needs gilding,
And the dockyard forbear to supply;
Place thy hand in thy pocket and gild her,
There be those who have risen thereby.If the fairway be crowded with shipping,
Beating homeward the harbour to win,
It is meet that, lest any should suffer,
The steamers pass cautiously in;
So thou, when thou nearest promotion,
And the peak that is gilded is nigh,
Give heed to thy words and thine actions,
Lest others be wearied thereby.
It is ill for the winners to worry,
Take thy fate as it comes with a smile,
And when thou art safe in the harbour
They will envy, but may not revile.Uncharted the rocks that surround thee,
Take heed that the channels thou learn,
Lest thy name serve to buoy for another
That shoal, the Courts-Martial Return.
Though Armour, the belt that protects her,
The ship bears the scar on her side;
It is well if the court acquit thee;
It were best hadst thou never been tried.
Now these are laws of the Navy,
Unwritten and varied they be;
And he that is wise will observe them,
Going down in his ship to the sea.
As the wave rises clear to the hawse pipe,
Washes aft, and is lost in the wake,
So shall ye drop astern, all unheeded,
Such time as the law ye forsake.Now these are the Laws of the Navy
And many and mighty are they.
But the hull and the deck and the keel
And the truck of the law is--OBEY.--By Captain Hopwood, R. N.
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