Dönitz's plan for 1944 was simply to survive and await the XXI and Type XXIII submarines. New radars were on the horizon and a direction finding antenna for "Naxos" was scheduled for use. Dönitz established a naval operations scientific staff to focus on more powerful centimetric radars. Production of submarines was streamlined. Parts for eight major sections were fabricated across 60 plants in Europe an assembled at Hamburg, Danzig and Bremen to ease the pressure of bombing and congestion at shipyards. The first of the new generation boats were expected by April 1944. Dönitz hoped for 33 per month by September. In early 1944, Dönitz opted to concentrate west of Ireland, at 15 and 17° west, in the hope convoys would come to them. Single boats were still sent to the Mediterranean and Indian Ocean. With 66 vessels at sea at any one time, and with 200 boats operational, the BdU was still a viable threat and he believed the force could achieve modest success. The U-boats were painfully slow, strategically, operationally and tactically. Crossing the Atlantic took up to a month compared to a week in 1942. Positioning west of Ireland could take several weeks submerged. In the first quarter of 1944, U-boats sank only three of the 3,360 ships that passed south of Ireland. In return 29 crews were lost.