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JANUARY 24, 1929
SEAWORTHINESS TESTS OF THE ROHRBACH "ROMAR"
By A. HOLZAPFEL
[We have received from Berlin the article of which a translation is given below. The writer of the article is not personally known to us, but the account and photographs give no cause for believing the " story " to be other than quite reliable, and in view of the unusual design of the Rohrbach " Romar," we have thought
When, more than a year ago, the German Ministry of Commerce (Reichsverkehrsministerium) and the German Luft Hansa were faced with the problem of ordering seaworthy flying-boats of the Rohrbach "Romar" type, it doubtless required considerable courage and technical far sightedness to decide upon ordering three boats of this type, especially as at that time the boat was unknown in every way. The confidence in the German industry which was thus shown has been proved fully deserved. The will to seek technical progress which was shown by those who ordered the machines has been attended by success, and the Rohrbach " Romar" has brought German aeromarine commercial aviation a good step forward as far as can be seen and judged by experts at present, It is certain that there will be technical progress after the " Romar," but it is also certain that the " Romar " will remain an important stage in the development.
Concerning the performance and load-carrying tests carried out in October, a good deal has already been published in various German aviation journals. It remains to say something about the seaworthiness tests and matters connected therewith.
Seaworthiness is, besides the ability to get off with a heavy load, the greatest problem in flying-boat design, especially because the stresses in flying-boat hulls set up by waves and water impact cannot be calculated ; moreover, but a modest amount of practical experience is available in the presentday industry. The seaworthiness tests of the Rohrbach " Romar " were carried out as part of a fairly extensive " test programme." All flights were made in the presence of representatives of the Ministry of Commerce, the German Aircraft Experimental Establishment and the German Luft Hansa.
A serious incident took place during the night of November 16-17. A gale was raging all along the Baltic coast, and in the Trawemunde seaplane station one of the Luft Hansa flying-boats moored to its buoy had its tail so badly damaged by the waves that repairs took more than a week. (This boat was of a type which for years has given excellent service.) So violent was the gale that all three motor boats and launches belonging to the seaplane station filled and sank. The wind velocity was approximately 25 m. per sec. (56 m.p.h.), and on the beach velocities of 29 m. per sec. (65 m.p.h.) were measured. The commander of the (sea) pilots of Trawemunde, Herr Westphal, to whom I spoke of the gale on the morning of November 17, said : " Yes, we went to the Wiek with our pilot cutter to attempt to help, but we could do nothing, and the sea was such that we had enough to do to look after ourselves and our cutter." Also the " Romar " had to fight hard in the bad weather. She dragged her moorings, 600 kgs. (1,320 lbs.), and stranded on the north-west beach of the Potenitzer Wiek. There she lay for two days in the surf, and finally was washed ashore by the breakers.
The stranding of a flying-boat, and without anyone on board at that, was an event the results of which were wellknown. Naturally the boat must be badly damaged. At least this was generally assumed, and the report that the " Romar" was lying high and dry but undamaged and •without a leak was received with incredulous smiles, as was also the statement that most likely the machine would be able to get off the next day under her own power. However, thanks to the exceptional strength of the construction, the flying-boat had actually survived the stranding without the least damage, and was able to get off under her own power when the tide rose again. If one recalls the way in which previous flying-boats and seaplanes had suffered under the blows of the breakers after a stranding, and compares them with the behaviour of the " Romar " in this incident, one comes to the conclusion that the construction of the latter represents an enormous progress. The Rohrbach " Rocco " also dragged her moorings, but pulled up about 100 m. from the beach, where she remained and rode out the gale without sustaining any damage whatever.
Concerning the seaworthiness tests themselves, the views of the representatives of the Ministry, the D.V.L. and the Luft Hansa are unanimous. The "Romar" acquitted herself very well indeed. The flights were so arranged that, with the offshore wind blowing at the time, it was possible by choosing the distance from the coast to find a seaway of any magnitude desired. Those in charge of the tests were on board the steamer Trawemunde, and in my account I rely upon the reports of Herr Bertram and Dr. Koppe, from which I shall occasionally quote extracts. During the tests the wind was north-east, strength 6-7, and the seaway in the open sea was 6. In the Neustadter Bay seaways of 3, 4 and 5 could be found by choosing a suitable distance from the coast.
On being informed that the " Romar " had started the Trawemunde put to sea and steamed against the wind in a seaway of 2-3. On the pre-arranged signal being given, the " Romar " alighted in this seaway, and as there was a swell running at the time, across the seas, the total effect corresponded to a seaway of about 4. After the first alighting the machine made a jump, and then came to rest, lying quietly in the sea. The first start, during which no spray came on board, took 22 seconds. The Trawemunde then turned outwards, and farther from the coast found a patch of water where the seaway was 3-4 again with a cross swell. The " Romar " again alighted and but little water came aboard, and this only at the last moment as the machine was almost stationary (purely a breaker). The next start took but 20 seconds. The machine made three jumps, being flung into the air by the top of the waves. A little spray washed over, but this ran off under the engines.
The Trawemunde steamed out until a seaway of magnitude 5 was found, still with a cross swell running, which was equivalent to a seaway of about 6. When alighting, the " Romar " made three bounces clear of the water, but by opening the throttles at the right moment the pilot was able each time to bring the machine back to the correct trim for alighting. At the fourth start the swell, which was coming from starboard, pressed the starboard wing float under. It is assumed that the bolt which secured the diagonal strut to the wing sheared off. The strut collapsed, and the float was free to move forward, with the result that the machine -lay over on the starboard wing. The wing cut under, and the machine swung around through a complete circle, fetching up heading into the wind, and then quickly righting herself. With previous machines such a happening would almost certainly have resulted in total loss, as usually the machine would then dig in and turn over. In the " Romar," however, the watertight construction of the box wing spar gives great buoyancy, and in the case mentioned it saved the machine from capsizing. The " Romar " after the mishap refused a tow, and rolled into Neustadt in a cross sea under her own power. In spite of the heavy sea, across the wind, and the swell which was now aft, the machine could be manoeuvred and kept broadside to the wind. Capsizing was out of the question. The wing float strut collapsed, but the float itself was not damaged and continued to give a certain amount of support. The pilot even asked permission to go up again and continue the tests, which would have been quite feasible, but it was decided to discontinue, mainly for reasons of insurance. The fear that the submerged wing would be damaged was proved groundless, as the wing was quite undamaged in spite of seas breaking over it The ensuing manoeuvre showed that even under such conditions the machine could easily be righted.
The acceptance tests of the " Romar " were thus concluded, and at 4 p.m. the machine was secured at the slipway in Neustadt. Spares for the damaged float were ordered by telephone and sent by car, and at 6.30 the machine was ready to start again. The seaworthiness tests were carried out at the contract weight of 145 metric tonnes (31,900 lbs.) Starting with the assumption that seaworthiness is first and foremost a matter for sailors, I asked the Commandant of the Trawemunde (sea) pilots, Herr Westphal (who had been on board the steamer Trawemunde) to express an opinion, and I quote from his reply the following : " During the manoeuvres on the water, and during the figures-of-eight carried out, when the boat was lying broadside on to the waves, the seaworthiness was good, and the boat rolled very little and never gave any cause for anxiety." During the seaworthiness tests of the " Romar" the seas were especially short and choppy, as they are in the Baltic and North Sea much more than on the coasts of the Atlantic, where the distance between the waves is twice as great.