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1. Subject tests were run under the sponsorship of this Laboratory and the Bureau of Ships as authorized by reference (a) in order to test results previously obtained by Mr. C. A. Sluhan of the American Cyanamid Company and Mr. G. P. Hevenor of the Johnson-March Company on a smaller scale. Enclosure (A) relates the general constitution of the wake-concealing solutions used, and the conclusion that a plain suspension of carbon black in water was the most effective of those tested. It gives promise of blackening the wake of a motor torpedo boat for a period of five minutes at high speed at a cost in weight of between 30 to 50 pounds of solution per mile. In addition to the weight of solution, an equipment weight of 200 to 250 pounds is involved. Enclosure (B) covers the pumping equipment used during the several test runs and makes estimates and recommendations as to the pumping equipment required and the size and positions of the sprays to be used.
2. The tests on June 22 were observed by Mr. Gerome Brush of the Woods Hole Oceanographic Institute; Mr. J. T. Remey representing Section C-6 of the National Defense Research Committee; Mr. Everett Warner of the Bureau of Ships; Mr. G. P. Hevenor of the Johnson-Starch Company; Mr. C. A. Sluhan of the American Cyanamid and Chemical Corporation; Mr. H. M. Parsekian of the Binney and Smith Company; Commander R. W. Dole of the Naval Research Laboratory; Lieut. Comdr. W. C. Specht, the Commanding Officer of Motor Torpedo Squadron Four; and Lieut. Comdr. C. B. Beasley, commanding U.S.S. JAMESTOWN.
3. The wake-coloring material was contained in a drum with a valved connection to the distributing pump suction. The pump, a gasoline driven handy billy, discharged through a jury rig of piping and rubber hose laid on deck to the spray nozzles. The nozzles at the stern, five in number, were screwed into a pipe at the deck edge. Those for the bow waves were screwed into a short horizontal pipe section about two feet above the chine which was fed by a vertical pipe clamped to the deck edge. Several nozzle arrangements were tried in conjunction with several different carbon black suspensions. All were successful in darkening the bow and stern waves at 27 knots as viewed from the bridge of the JAMESTOWN. On one run when the starboard bow wave only was blackened, it was estimated by competent observers to have between 5 and 10% of the reflectivity of the uncolored port bow wave. Inspection from close at hand revealed minor discrepancies in the coverage by different nozzle arrangements, which resulted in the variety of arrangements tried.
4. It is recommended that at least one motor torpedo boat be fitted with a permanent installation system of necessary storage tank, pump, piping, and spray nozzles for tests to establish the most suitable pump size, pressure, and nozzle locations and to determine the optimum concentration and type of coloring agent. Mr. Sluhan and Mr. Hevenor, authors of enclosures (A) and (B), have very generously offered their full cooperation in such consultations as the design personnel of the Bureau may deem advisable. Their cooperation to date in conducting these tests at their own expense for the greater part of the equipment necessary is greatly appreciated. Their experience along the lines of chemical solutions and pumping equipment has been and may be expected to be extremely valuable.
Copy to: CNO (with enclosures)
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C O P Y
THE JOHNSON-MARCH CORPORATION
52 Vanderbilt Avenue
June 30, 1942.
Commander R. W. Dole,
Dear Commander Dole:
The following will serve to supplement our various reports on the subject of application of the Sluhan compound on a P.T. Boat at the Melville Base Training Center. The recommendations and opinions are based on the observations of Mr, George A. Mau and the undersigned.
Test #1 - May 7th and 8th, 194-2, on P.T. 63 - The design of the temporary equipment for this test was based on incomplete data. The size of pump, pressure required and amount of compound to be sprayed were all assumed.
12 GPM Turbine Pump driven by 1 H.P. Portable Gasoline engine,
4 - flat sheet spray .062 nozzles, aft.
A total of 9 l/2 GPM solution was pumped at a pressure of 30 psi.
Results - It was quite evident that the pumping unit was entirely too small and the pressure too low; also that the outside pump suction, for seawater to be mixed with the compound, was extremely difficult to maintain. The test served to indicate the amount of compound necessary, the approximate size pump required, the nozzle positions, pressure and capacity required. This preliminary test gave definite indications of the results from the use of the Sluhan solution in blacking out the wake.
Recommendations made for future tests - The installation of a 75 GPM Turbine Pump delivering 80 psi at the nozzles, to be driven from center engine propeller shaft with a belt drive. That the pump suction be taken from a 3" engine heater exchanger intake instead of outboard; that two sets of pulleys be provided on the pump shaft and propeller shaft for minimum and maximum speed requirements; that the following nozzles be placed as shown on the drawings previously submitted:
5 - flat spray nozzles aft ( 3 - .156 - 2 - ,187)
These nozzles would have a total capacity of 53 GPM. The aft nozzles were to be mounted in a pipe secured to the transom on a swivel, so that the angle of the sprays could be changed as desired. Clamps for retaining all piping were shown on the drawings. The port and starboard clamps for the nozzle piping were to be fabricated of a sheet steel to conform to the contour of the hull, with adjustable pipe clamps to permit raising or lowering or changing the angle of the nozzles. These nozzles were to be located about 1' above the chine, at a point approximately opposite the front of the control cabin.
Test #2 - June 22nd and 23rd, 1942 on P.T. 65 - The 75 GPM pump was installed in the engine room. The relief valve and strainer were on hand, but had not been installed. Two strand V belts were used to connect the 12" brass pulley on the propeller shaft to a 3" white metal pulley on the pump shaft. This latter pulley was secured with two l/4" set screws; the hub had been practically all cut away to fit it to the shaft. The V belt capacity was approximately 3 HP and the pulley capacity was less than 1 HP. The 75 GPM pump was not used, since the flat belt and pulleys recommended were not available. The pump was designed to run at 1,750 RPM and the pulley arrangement suggested would have maintained this maximum. The V belt pulleys as installed, however, would have increased the speed of the pump to approximately 3,000 RPM at maximum speed of the boat. As a substitute, a special fire-fighting engine driven pump was installed on the deck. The pressures with this pump were from 30 lbs. to 50 lbs. psi.
The piping for the aft nozzles was quite satisfactory, but were installed without swivel. The port and starboard piping was not mounted on steel plate clamps to conform to the body contour, as recommended, and the pipe was run downward from the gunwale without any lower clamp. This pipe could be raised and lowered to change the angle or position of the nozzles. The aft nozzles consisted of three .187 and two .218 flat sprays having a total capacity of 31 GPM. The port and starboard nozzles consisted of four .218 flat sheet sprays having a total capacity of 30 gallons per minute. This made a total spraying capacity of 61 GPM to cover both the wake and bow waves.
Test results - The position of the nozzles aft, having a 4.5 degree spraying angle from the top of the transom to the water, was quite satisfactory. The capacity of this spraying unit should be increased to five .218 flat spray nozzles having a capacity of approximately 45 GPM. The first test run indicated clearly that the port and starboard nozzles were insufficient to cover the entire bow wave. After many changes in position it was indicated that three .218 nozzles, having an approximate capacity of 27 gallons per minute on each side, approximately opposite the face of the control cabin and located 2' to 3' above the chine, would give very good coverage. These should be located so as to spray at 45 degree angle with one corner of the spray up against the body. This would cover all of the above wake excepting the part breaking at a point about the middle of the torpedo tube. In the test three .187 nozzles and two flattened pipe nozzles, having an estimated capacity of 20 gallons per minute, covered this part of the wake. They were quite satisfactory, despite the fact that the nozzles were mounted on the gunwale and considerable windage loss occurred.
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The test indicated that a 75 GPM pump, driven from the propeller shaft and delivering at least 80 psi pressure at the nozzles, would be both feasible and necessary. The five nozzle arrangement on the transom with a 45 GPM capacity would be quite effective to adequately cover the propeller wake. Two .250 flat spray nozzles, having a capacity of 12 l/2 GPM each should be mounted slightly forward of the control cabin on the port and starboard sides. One nozzle should be mounted 2" above the chine and the second 3' above the chine. In addition there should be four .218 nozzles, having a capacity of 9 GPM each, mounted 2, 3, 4 and 5 feet above the chine about 2' apart and starting about 5' back from the two front .250 nozzles. All nozzles should be directed so as to spray from the hull at a 45 degree angle aft and a 45 degree angle to the water.
Summary - The foregoing recommendations are intended to cover the application of the Sluhan compound at all speeds. The normal requirement with any one set of nozzles operating would be 80 to 90 gallons per minute. This is based on the use of a 10% solution of the compound, similar to that used in the test. If a 20% solution is used the total weight of compound would obviously be considerably reduced. We recommend that a permanent spray system be so installed and valved so that any set of sprays can be controlled at will. For example, under certain conditions it might be advisable to only black out the bow waves or either one of them - likewise, the stern wake alone could be blacked.
The permanent equipment should consist of a bronze pump having a capacity of at least 80 GPM at 100 lbs. pressure driven by the motor shaft; inside brass piping and all brass or bronze nozzles inserted through the hull. The total weight of the equipment should not exceed 200 lbs. The most convenient size for the compound containers would be about 30 gallons. These should be equipped with quick acting connections to the pump intake.
The indications are that both the bow and stern wakes can be well blacked out with the 10% Sluhan compound at a weight of equipment and material of about 100 lbs. per mile of water travel. It should be possible, by using a more concentrated compound and higher pressures, to reduce this weight factor to approximately 50 lbs. per mile.
In our opinion this system for blacking out the wake also has considerable possibilities on larger ships, such as destroyers or fast cargo ships. In this case the wake area, in proportion to hull size, is considerably smaller than the P.T. Boat and the space and power available very much greater. We also believe that the Sluhan compound will be very helpful in rendering the phosphorescence in the wake and bow wave invisible at night.
We are very appreciative of the fine cooperation given us by Lieutenant Commander W. C. Specht, the various other officers at Melville and by you. If you decide to carry on any further test or to design a permanent installation for any particular type of boat, we will be glad to give our service and to cooperate as we have to date.
Yours very truly,
C O P Y
AMERICAN CYANAMID & CHEMICAL CORPORATION
June 30, 1942
Commander R. W. Dole
Dear Commander Dole:
This report covers primarily the chemical and pigmentation phase of the experiments run on torpedo boat PT 65 on June 22nd and 23rd, The report on the equipment used is being submitted separately by Mr. G. P. Hevenor of the Johnson March Corp.
The tests conducted on PT 63 on May 7th and 8th indicated that the equipment had insufficient capacity but appeared promising enough for you to authorize additional tests.
The present runs were made on June 22nd and 23rd on PT 65 at Melville, Rhode Island. The first tests were made using as an indicator or "spotter" Binney & Smith Company's Colloidal Black Dispersion "0", diluted to 10% carbon black with sea water. The "spotter" was used to determine the best nozzle positions and also the amount of coloring necessary to do the job.
The boat speed was 27 knots (propeller 1400 r.p.m.) and the coloring solution fed with the valve wide open. The consensus of opinion of observers was that the color was too dark but that the wake next to the hull at the prow was not covered. The quantity of coloring material was not determined.
On this run, the same type of coloring solution was used as in run #1, but the nozzle positions were changed to completely cover the prow wake. These two tests (runs #1, #2) seemed to indicate that with proper nozzle adjustment the straight carbon black dispersion would give entirely satisfactory results for this application.
In this run, a mixture of three formulas 19, 20 and 22 was used. This was cut with an equal quantity of sea water so that a total of 40 gallons stock solution resulted, containing 5% carbon black. The mixture consisted of carbon black, soap and other materials; the soap to "kill" the trailing
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wake and the pigment for coloring. The 40 gallons were used up in 3 minutes and 15 seconds at a speed of 27 knots, and although the color was not as deep as with the straight dispersion, the results were satisfactory. Only one side of the prow and all of the stern was treated and it was definitely shown that the trailing wake was considerably reduced on the treated side but persisted for a great distance on the untreated side.
This run was made with formula 20-B which contained a different combination of soap, solvents and carbon black. It was unsuccessful because the mixture jelled with the sea water so the run was discontinued.
After changes in nozzle design and displacements were made at the suggestion of Lt, Cmdr. Specht, tests were begun again on the afternoon of Tuesday, June 23rd. Formula #21 was used as the stock mixture. This formula was somewhat similar to the mixture used in run #3 and contained 10% carbon black. Because the positions of the nozzles were changed at various times, no attempt was made to determine the rate at which the solution was used. Only one half of the prow wake and the whole of the stern wake was treated. Here again the bubbles in the trailing wake were broken on the treated side while those on the untreated side persisted, Lt. Comdr. C. B. Beasley and Mr. Warner on the U.S.S. Jamestown who were observing, were of the opinion that the color obtained was satisfactory although not as dark as that obtained on runs #1, 2.
In first studying the problem, it was our impression that both breaking and coloring the bubbles were important. However, these tests showed that on this particular job the important consideration was primarily the coloring of the white water and that best results were obtained by using a carbon black dispersion. These tests also showed that a combination of soap and carbon black served the dual role of coloring and breaking the bubbles in the trailing wake. However, in this case the coloring efficiency was reduced because the soap by the mechanism of coagulating with sea water, reduced the effective surface area of the pigment. Therefore, dependent upon the type of application, a product can be used to produce greatest coloring efficiency without affecting collapse of the bubbles or one can be used, which at some sacrifice of coloring efficiency will also cause the trailing wake to be "killed."
The weight of the stock solution, which is an important factor, can in the case of the straight dispersion for the same coloring effect be considerably less than the soap-carbon black mixture for two reasons:
(1) It is possible to make a more concentrated fluid dispersion of carbon black in water than in the case of a soap-solvent carbon black combination
(2) Among other factors, the greatest hiding power of a pigment is obtained when its full surface area is utilized. The soap mixture depends upon coagulation with sea water to collapse the bubbles of foam. Such coagulation decreases the effective surface area of the pigment particles, hence less coloring is obtained as evidenced in runs 3, 5 compared to 1 and 2.
As to the quantities of materials necessary, the only accurate estimate so far possible is that obtainable from run #3. At a speed of 27 knots, 40 gallons of 5% carbon black together with soap was used in 3 minutes and 15 seconds or approximately 12 gallons per minute. Admittedly, only one half the prow and all of the stern was treated, but we believe that by using the straight dispersion (which we feel this particular job requires) the same amount of carbon black will be sufficient for both sides of the prow as well as the stern.
It is possible to produce a fluid 30% carbon black dispersion so that with the equipment used, one mile would require 4 gallons (35 pounds). However, the equipment originally designed and suggested by Messrs. G. Mau and G. Hevenor of the Johnson March Corp. would produce greater pressure and hence greater efficiency so that probably not more than 25 - 30 pounds of concentrate of 30% pigment content would be required per mile. We believe that with a total equipment weight of 200 - 250 pounds and a treating solution of 125 - 150 pounds would be sufficient for 5 miles run at 60 m.p.h.
/s/ C. A. Sluhan
P.S. Within a short time I hope to forward to you the experimental data on the work done in making various soap-carbon black mixtures.
National Archives & Records Administration, College Park
Record Group 19, Bureau of Ships General Correspondence Files
Transcribed by RESEARCHER @ LARGE. Formatting & Comments Copyright R@L.
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