The new X-18 Tank Boat built by Indonesian shipbuilder PT Lundin is expected to begin firing trials next year.Tank Boat X18☆
An actual-sized model is on display at the Indo Defence exhibition. The vessel combines the versatility of a lightweight catamaran with the power of a 105mm gun from CMI Defence, one of Lundin's partners.
The Indonesian MoD has taken a real interest in the system. Widjajanto, the chief commercial officer at PT Pindad – the other partner of Lundin – said that the Minister of Defence has expressed interest in developing a new specialist ‘swamp battalion’ that can traverse the numerous Indonesian waterways and thinks the craft can fit this role.
Widjajanto added that there were discussions with a Middle East country about the vehicle. UAE has previously expressed an interest in the vehicle.
First announced in May 2015, the X-18 has now completed structural design and engineering phases. CEO of PT Lundin, John Lundin, told Shephard that the company has also run the vessel in a test tank to prove the concept and was ready to start building and get a prototype in the water fitted with the CMI 3105 modular turret that can fire from 30mm to 105mm calibre munitions.
Lundin said the X-18 is technically feasible using a catamaran hull made from advanced composite materials and using the 105mm turret from CMI Defence.
The 40t boat ultimately has three functions. The first was to have a brown water/riverine craft but secondly to also has a green water/littoral capability to work close to the shore to support amphibious landings on a large scale as well giving firepower along the waterways and in very shallow water.
Instead of having large warships with small guns and trying to get close to the shore, the concept is to put larger calibre guns on smaller vessels to provide fire support.
‘What is unique about the CMI gun is it has 42° elevation so that when an amphibious landing reaches stage two on the shore it can beach land and provide an artillery function to back up the troops. CMI as far as we know is the only one that can offer this dual functionality,’ Lundin said.
The third role is as a troop transporter/logistics craft. X-18 has a crew of six but can take up to 20 troops and logistics supplies and in the same sense could be used in a medical evacuation role if required.
The main challenge in carrying a heavy gun on a lightweight boat is having good enough stabilisation. The catamaran hull with a hydrofoil (underwater wings) takes away a lot of the stability issues. Along with a good gyrostabilisation system from a vehicle, a relatively small boat can support a larger calibre gun and all additional personnel and logistics loads.
Lundin argued that a turret on a vehicle moving over land actually moves a lot more than when compared to a turret on a waterborne platform.
CMI technology has been able to manage the recoil forces of the gun, Jean-Luc Maurange, president of CMI Defence, told Shephard that ‘although the gun is large calibre the recoil forces that are transported from the weapon to the boat are massively lower than a traditional tank gun’.
Therefore when doing composite materials engineering the forces they have to contend with are of a magnitude less making it more feasible to support a bigger gun.
The other major challenge alongside the stability issue was the marinisation of the 105mm gun and turret for maritime operations. CMI has used different materials, adding corrosion protection sealing for the electronics. Maurange said this was the major part of the work that they had to do.
Furthermore, the tower structure below the turret, which usually goes deep down into a standard naval vessel and includes the basket and ammunition handling and storage, is much less on the X-18.
Maurange said that the CMI gun uses an autoloader with a bussle, which means that the depth that the turret extends into the boat is an order of magnitude lower and permits the architecture for the craft. It can store 32 shells in two rows of 16 and these are stored below the waterline.
The armour package is 7.62mm protection for the crew areas and 12.7mm for frontal protection. Lundin said that during beach landings the protection systems often use 12.7mm so this will offer extra reinforcement although weight restrictions means that it can be provided all around.