TEST PIECE - This is the machine that it is all about. It's just 2.2 meters long, but big enough to tell us how the full size development SeaVax will fair in adverse conditions.

STRING LINE - Cement is only useable for so long, that is why it is important to work quickly. In order to do that you need everything set up and in the right place. A string line makes it easy for a brick layer to get a level wall - without have to constantly check with a spirit level. Copyright © April 17 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

PERFECT FIT - Ross (left) and Jamie (right) slide the frame for the sluice gate into place. When calculating pressure on the sluice gate, it helps to mentally divide the height into convenient slices of one foot (if working in imperial - or 30cm if working in metric). This will not give us a completely accurate result, but will give us a rule of thumb figure to design for - and of course we add in a generous margin of safety. The Pressure/Depth Equation in a fluid that is standing still is: the pressure p at depth h is the fluid’s weight-density (mass) w times h: p=wh. Our sluice gate will then have to cope with roughly 1,600lbs in calm conditions or as much as twice that in dynamic conditions (just to be on the safe side), so between .72 and 1.43 tons of load. The fixings securing the sluice gate frame to the walls, must be capable of taking those loads. We are using 13mm threaded rod as studs, cemented into the walls at 250mm centres to a depth of 200mm, to give us 16 fixings for the frame, so that each bolt has to handle between 100-200 lbs of force. In addition, the frame is cemented in place. Copyright © April 17 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

FUNGICIDE - We used this fantastic 15 litre backpack to make the job of cleaning off the moss and other flora a whole lot quicker. You pump this little beauty as you go. No need to stop until the whole tank is used - and yes we did use the whole tank. This was an incredible bargain from the Range in Eastbourne. It will also take care of our weeds. Don't forget to wash up and rinse clean after use, ready for next time. It is a never ending battle against weeds.

RECYCLING - Original bricks were used from other sections of the building that had not fared that well. Cleaning these bricks up is an art-form. Even with lime cement, you have to strike the mortar at the right angle or the brick might break. Quality reclaimed bricks of this age can run to £1 or more each, so we trod carefully. It had been spitting rain earlier, so we covered the newly laid bricks with a tarpaulin that also protects against frost. Copyright © April 24 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

STAIRWAY TO HEAVEN - We had to remove some on the redundant brick steps from the original cottage to be able to fit the recirculating guide vanes. First though we surveyed and recorded the architecture with copious photographs and detailed drawings. As you can see these steps end at a brick wall, meaning that the doorway that was once there has been bricked in. The brick plinth to the left of the steps was more than likely to mount a stone sink. Copyright © April 24 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

HAMMER SDS - Here we see Richard giving it some with a Special Direct System (SDS) drill. These heavy-duty hammer drills can be set to drill with very tough masonry bits, or to chisel, a bit like the road hammers, just smaller. The crew took it in turns to demolish the steps, but they were a mix of engineering bricks and a very strong mortar mix with sharp sand. In the end time defeated us, and it was time to clear up. Copyright © May 1 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

MORE CEMENT PLEASE - Terry calls for another gauge of cement. This area is a suntrap in the afternoons, so we relaxed health & safety a bit for our expert builder to cool down. Terry is also a martial arts enthusiast. Copyright © May 1 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

POINTING - Attention to detail. Once a wall is built, it is usual to point the joins. Terry uses a half round tool to make the job easy. He knows that this wall is likely to be rendered, but figures what the heck. Copyright © May 1 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

MORE RENDER - We decided to render the top half of the original wall as well. The new wall on the right is sure to be rendered, though it goes against the grain when you have such a lovely genuine cottage look, from original period bricks. You may be wondering about the arch on the left? And so you should, this of course needs to be blocked in or we could not fill the tank with water. This is the space between the inner and outer concrete walls of a World War Two air raid shelter. We don't want to spoil the history, so this needs special attention.

We are blocking this chamber with two sheets of treated plywood, laminated together to give us 36mm thickness for strength and then caulked and bolted in place to a timber frame. The overhead gantry is to come next. Copyright © May 1 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

WWII ARCHAEOLOGY - Here we see the timber frame going in. It has to be pretty strong, so we used some serious screws, deep seated in the concrete with heavy duty wall plugs. They had to be tightened up with a spanner, a screwdriver would not budge them. The treated timbers were also bonded to the walls and tight-fit noggins were inserted to push the timbers hard against the concrete. This is a deluxe World War Two air-raid shelter, incorrectly referred to as an Anderson Shelter, which in fact were made of corrugated iron. Air-raid shelters were also known as bomb shelters, structures for the protection of civilians as well as the military against enemy attacks from the air. If the world is ever crazy enough to go to war again (please don't) it's nice to know that this building could provide protection. In fact there is a nuclear blast chamber elsewhere on the grounds. But that is another story.

ANDERSON SHELTER - The Anderson shelter was designed in 1938 by William Paterson and Oscar Carl (Karl) Kerrison as a result of a request from the Home Office. This design was named after Sir John Anderson, then Lord Privy Seal with special responsibility for preparing air-raid precautions immediately prior to the outbreak of World War II, and it was he who then initiated the development of the shelter. After evaluation by Dr David Anderson, Bertram Lawrence Hurst, and Sir Henry Jupp, of the Institution of Civil Engineers, the design was released for production.

Anderson shelters were designed to accommodate up to six people. The main principle of protection was based on curved and straight galvanised corrugated steel panels. Six curved panels were bolted together at the top, so forming the main body of the shelter, three straight sheets on either side, and two more straight panels were fixed to each end, one containing the door - a total of fourteen panels. A small drainage sump was often incorporated in the floor to collect rainwater seeping into the shelter. The shelters were 6 feet (1.8 m) high, 4.5 feet (1.4 m) wide, and 6.5 feet (2.0 m) long. They were buried 4 ft (1.2 m) deep in the soil and then covered with a minimum of 15 inches (38 cm) of soil above the roof.

BLANKING PLATE - The timber frame was blocked up at the bottom with engineering bricks and a very strong mortar mix (not shown in this picture - see above), being careful to keep the clay drain pipe that vents the chamber clear. On the right of the timber frame you can see the earlier plywood that blocked this feature. Being untreated, the plywood only lasted 15 years. These remnants will be used as patterns to cut the new blanking sheets. Copyright © May 23 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

BLANKING PLATES - Two sheets of treated plywood were cut to shape, tanked on the rear and then fixed into position with stainless steel screws and washers - finally to be caulked in situ, as you can see in the picture above. The reason for using two separate sheets was so that the top half could be undone for inspection and ventilation, leaving the lower sheet to retain water.  Copyright © May 25 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

TRADITION - Back at the quarry face and the going was tough. Sometimes all the modern tools in the world will not get the job done as well as a bolster and club hammer. The same technique was employed here as for rock blasting. Holes were drilled, but instead of using blasting explosives, well aimed blows directed the hammer shocks to good effect. Copyright © May 9 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

THE ROCK FACE - More holed are drilled with an extra long SDS bit. You can see how strong these engineering bricks are from the dense clay. Other bricks are ordinary strength, and being hand made, vary in composition - so come out far easier. Copyright © May 9 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

QUARRY DEMOLITION - The line of drilled holes are obvious from this picture, as is the mix of brick types. Mind you, we are re-using as many original bricks and the mix of engineering and plain is roughly the same. The wall and step face can now be rendered for a smooth surface on which to apply masonry paint. Copyright © May 9 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

CONCRETE STEP - There was a layer of bricks above the slab level here, set on a concrete base - we think for a sink in the cottage C. 1900. An SDS makes light work of such removal. The concrete has to be lowered by around 30mm in order to apply a screed of sharp sand mix to blend in with the existing floor. A club hammer and bolster is used to trim down any high points. Copyright © May 14 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

SEAVAX TEAMWORK - In this picture  you can see the first stages to replace the timber frame that was past its best. While the rest of the team were spreading render on the walls, our chippie was measuring treated wood and checking the angles. Wooden frames will be used for the entrance-ways and door frames. Stainless steel beams are for the water tank sections only. Copyright © May 15 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

REMODELED STEP - That's better. The tank floor is now even, with a gentle slope for emptying purposes. Having a sluice gate means that we can empty our test facilities quickly, to refill with clean water. Most testing tanks are unable to deal with chemical or solids pollution issues - without it costing a fortune in water bills - and time of course. Copyright © May 15 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

TIMBERS - The rotten frame was removed and replaced with treated timbers with a damp proof membrane painted on the underside. We used sharp sand and a strong Portland cement (Mastercrete) mix with lime and waterproofing admixture added, to bed the timbers in. This is much stronger than a conventional DPC. We also used steel pins as locators, pre-drilled into the brick wall. Copyright © May 28 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

CONCRETE - On the other side of the tank we used the same location and bedding system for the wooden frame wall plates. You have to work quickly as a team using this method. Copyright © May 28 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.

RECIRCULATING WAVE - Without re-modeling the steps that were in the lower left hand corner of this diagram, we would not have been able to install the turning vanes to be able to use the tank in recirculating mode. In this mode we can measure the drag of a hull, or any other object, even those submerged, such as a submarine - and for a fraction of the cost of other facilities.

RENDERING

Unless your wall has been recently built, you will need to clean it well – remove any loose paint, and dust or loose debris, plants and moss. Then scrub off any mould with a bleach, or fungicide solution, and hose down the wall to remove any dust and dirt that could stop the render from adhering.

Our walls are old and flaky, with weed growth. So, we needed to give it the Full-Monty. We are treating this as an external wall. The render mix will then be: 3 parts cement, to 4.5 parts soft sand, to 4.5 parts sharp sand and 1 or 2 parts of lime.

Sharp sand increases the strength and reduces cracking and erosion. Sharp sand also improves the moisture resistance of cement. Using an admixture can make a render almost waterproof. Using ordinary building sand makes the mix more pliant. The best way to mix the render is with a cement mixer as this gives a more even mix, without getting you all hot and bothered or straining your back.

RED SKY AT NIGHT - Shepherd's delight, so the saying goes. It was a cold night, getting down to 2 degrees periodically. What you do not want is frost on you fresh cement. Frost and freezing temperatures kills cement unless it has reached cure - you'd have to start all over again. This picture was taken at around 8:00 pm after the final float finishing of the wall render. Copyright © April 17 2016, all rights reserved. You will need permission from Bluebird Marine Systems Ltd to reproduce this photograph.