6.2 m Solar Boat
From MarineWiki
AIM
The aim of this project is to design and build a prototype of a boat, which is completely powered by solar. This is the first one among the series solar boats which we are jointly developing with [Team Sustain http://www.teamsustain.com/]. The entire power is supplied by a series of solar panels arranged on the roof of the boat and driven by two electric outboard motors.
DESIGN
Basic dimensions of the boat is Length = 6.2 m, Breadth = 2.5 m, Depth = 1 m. Since the boat is entirely dependent on solar power it was very essential to design an optimized hull form. With the help of professional software's we were able to complete this task very fast.
CONSTRUCTION
Project commencement : 13 Nov-2008
Day 1
It was a great moment for all of us. This is the First construction project undertaken by us. First job to be finished is preparing the mold. Since the time available was very less we were planing to make a temporary mold using Plywood and wood. We started with making the skeleton structure. Since the depth of the hull is only one meter we were able to get the lines printed on 1:1 scale on A0 sheet paper. Then from these printouts we marked the lines on the plywood. Then the skeleton templates (refer to the pictures)are made from the plywood.
Day 2
The templates are prepared for every 250 mm frame spacing. The estimated time for completing all the templates are around three days. Next step is to fix the skeleton templates on the keel structure. This is the most important step as far the construction is considered. Any mistake that happens in the alignment of the templates or in the dimensions of the templates will be directly reflected on the hull shape and consequently on the performance of the boat. All the templates are to be fixed on the relevant frame spacing. Once we have all the templates fixed next step is to lay the plywood inside the skeleton structure. For getting the smooth finish on the surface plywood will be covered with mica sheets.
Day 3
As expected making the templates was completed today. As ply wood alone will not be strong enough to keep the shape of the hull, the templates are to be strengthened with wood (refer to the pictures). Also these templates are joined to the keel structure by joining these wood members and the keel structure using nails.
Day 4
Keel structure is prepared using the keel offsets. These offsets are marked on the plywood. Then wooden pieces are joined(refer to the picture) to form the bottom shape of the hull. Then the keel structure is kept in the vertical position, so that the templates can be fixed on to it. Make sure that the plane of the templates are perpendicular to the hull center line. Both sides of the hull should be symmetrical. These are the areas where some body who is making there first boat can go wrong.
Day 5
Once the base structure is finished, it is lifted vertical up, and all the templates are arranged on to it. Wooden supports are provided on both sides, and also on the bottom to keep the templates in exact position.
Day 6
Once the templates are arranged on the keel structure next step is laying the plywood (refer picture). For this purpose plywood of 4mm thick is used. Make sure that the plywood is joined correctly. If gaps are formed on the joints then the same impressions will be coming on the surface of the finished hull also.
Day 8
All the templates are fixed to the keel structure. Then covering the templates with the mica sheets is completed. For this purpose mica sheets of 4mm thickness is used. Mica sheets are fixed using nails. Then for smoothing the top edges mica sheets are arranged on top as shown in the below pictures. Irregularities in the surface are removed by grinding.
Day 9
Once entire surface is completed, next step is laying mica sheet (with one side smooth) on top of the plywood. This surface will be forming the outer surface of the finished hull. So this sheet has to be of very smooth surface but need not be of good quality. on top of this sheet we have to give the first layer of Gel coat.
Day 13
While fixing the sheets care must be taken to avoid air getting trapped inside.
Day 14
Carpentry work was finished yesterday. Today FRP workers has started working on the boat. The first job is to fill the gaps between the mica sheets using plaster of paris. This will avoid any possible surface irregularities that may come on hull. A coat of wax polish is then applied to the surface. A more number of coats will give better smooth surface. There are proper curing time for the wax coating. Follow the prescriptions of the manufacturer.
Day 15
More number of coats are to be applied on the surface. After completing one more coat of Gel coat and Pigment mixture, a layer of chopped strand mat is placed on the surface. This is one of the mats that is used for reinforcing. This material is specified by weight: 300, 450, 600 and 900 g/m2 are popular weights of CSM. The one side of the material is slightly smoother than the other which reflects the smooth side of the conveyor belt on which the mat was made. It is the rougher side which should be placed down when laminating. One other type of mat that is used for reinforcement is the Woven roving. Standard specifications are 18 oz per square yard (600 g/m2) and 24 oz (800 g/m2). Next layer of coating is to be done using the resin.
During manufacture, the roving is woven into a cloth such that roving in the “warp” direction (length of the cloth) is continuous for the whole length of the roll which results in a high tensile strength. WR also gives a higher glass per unit volume ratio than CSM which reduces the amount of resin needed. Approximate resin to glass ratio for CSM is 2.5:1 by weight (30% glass) and for WR is 1.25:1 (45% glass). So for a large vessel whose hull shell weight is measured in tons, inaccurate resin/glass ratios or a laminate with too much CSM and not enough WR may waste substantial amounts of materials and money.
However, it is rare to find any WR in vessels of less than 6 m and equally rare to find vessels built wholly of WR. CSM laminates are normally adequate for smaller boats while wholly WR laminates do not provide a good inter-laminar bond (adhesion of successive layers) at any size. For these reasons experience has shown that normal hull laminates are best made of alternate layers of CSM and WR with extra CSM near the outside.
After the mould has been cleaned, waxed and polished, the first step in the molding process is the application of Gelcoat by the laminating team of 2 persons with mohair paint rollers.When cured it forms the shiny, smooth outer surface of the hull. It is usually a polyester resin but is more viscous. It is usually harder than laminating resin and has greater weather and chemical resistance as it forms a protective barrier between the environment and the reinforced laminate of the hull itself. A single heavy coating of 0.6 mm thickness or 2 medium coatings of 0.5 mm each is required on all surfaces which may curve from vertical topside to the horizontal bottom area. Paint brushes with unpainted wooden handles can be used to cover restricted corners. A pot life of 20-40 minutes will be planned which will require a 1 % catalyst content in the tropics.
This liquid is HIGHLY INFLAMABLE and evaporates quickly. Personnel should rinse any exposed skin in clean acetone followed by the tools in the same liquid before washing skin and tools again in soapy water then fresh water. Brushes and rollers must be dry before re-use
Once the resin, reinforcement, mould, personnel, and tools are ready, the catalyst can be added to the resin and the laminating begun. This assumes that the gel coat has been applied to the mould already, has cured, has been checked for flaws and is considered acceptable. If gel coat has been applied in the early morning, it may have achieved sufficient cure to be overlaid at the end of the working day. If an attempt is made to laminate over gel coat which is not cured sufficiently, the exotherm from the lay-up resin may deform the gel coat and leave problems which will only be visible when the hull (or deck) is released from the mould. If the gel coat is left for too long (a weekend) it may harden to a point which will not provide good bonding with the subsequent laminate. Reference to the manufacturer’s instructions and experience will soon further define these broad outlines.
Inspection of gel coat may indicate contamination by rain or sand and this should be remedied before any new resin is applied. Any rough areas may need to be lightly sanded and any dust removed. Any over cured areas can be lightly washed with acetone or styrene to regain some tackiness. The designer and manager will decide if reinforcement is to be laid transversely or fore and aft, the later is recommended as it more easily accommodates changes of skin thickness required between topside and bottom and is the faster method.
A sequence should be worked out so that the binder is dissolving in CSM reinforcement laid in one part of the mould while previously laid CSM with now dissolved binder is being consolidated in another part. While a layer is curing in one side of the mould, the other side can be worked on. This allows application or resin and reinforcement, consolidating and curing to take place in rotation.
APPLY RESIN BEFORE REINFORCEMENT!!
It is usual to lay up CSM alone for 1 or 2 layers next to the gel coat. Subsequent layers should be applied as soon as the resin hardens. These subsequent layers may be augmented by the inclusion of cloth or WR layer which can be laid in the mould at the same time as CSM and which are consolidated together. This saves time and achieves a superior bond as both layers of reinforcement are using the same batch of resin. If there are large dry patches, further resin can be applied before the WR is laid on as better impregnation is achieved if the resin is drawn and not forced down through the reinforcement. Being of a woven nature, WR is less prone to disintegration than wet CSM during rolling out, it can be consolidated using rollers but a “squeegee” is probably the best, quickest and simplest tool to use. The sequence for subsequent layers has been described, but it should be clearly understood that the opposite side of the hull should be molded in sequence with the first side.
On returning to the first side, the laminate may have become too hard and parts of it may need sanding to remove any protruding pieces of resin and glass which would prevent the following layer from achieving a void-free bond. These cured surfaces can be walked on to achieve access to restricted areas of the mould, but these risks contaminating the next bond. Walking on the FRP in bare feet is one solution, but even slight perspiration from skin in contact with the FRP can lead to a weakening of the bond in that area. Lightweight shoes should be provided to the laminators to eliminate this risk. Further protective clothing such as an overall is also a good idea as the inevitable contact between clothing and wet FRP can rapidly render a laminator’s own clothes unwearable. Filter face masks should also be worn to counter long-term respiratory problems but in practice these are usually declined by experienced laminators as the discomfort while wearing one is greater that the short-term unpleasantness of breathing styrene fumes.
For any job which requires working in a confined space such as a fish or fuel or fuel tank, the laminator should be ordered to wear a face mask. The work should be in short periods and the space should be force ventilated or exhausted. An electric fan may be used to BLOW fresh air via a long pipe but it should NOT BE USED TO EVACUATE a space nor be placed directly in the space as fire may result from the flammable styrene in contact with the electrical contacts of the fan.
Day 16
To maintain the strength at least four layers of coating should be made.Woven strand resins are rarely used for boats of length less than 6 m. Normally one coating can be done using woven strand. Final thickness of finished FRP hull has to be around 5 mm .
Hull is strengthened by providing stiffeners in the transverse direction. These stiffeners can also be laminated in FRP. There can be many ways through which we can achieve this. The method which we followed was to use 2" PVC pipes cut in to two pieces along its length and then each piece is kept inside the hull following the hull profile. To get the correct shape, pipes are cut along the diameter using hacksaw blade. (Refer to the picture). Pipes are given only to get the profile for laminating the FRP. The main load bearing members here are the FRP only.
Day 17
It is better to divide the hull into different compartments. This is to make sure that in case some accidents happens, water will not enter from one compartment to the other. Hull can be divided in to different compartments by providing transverse bulkheads as shown in the picture. We can give any number of bulkheads, depending on the position of the batteries, means of accessing inside the hull etc.
Day 18
First hull got finished today. While taking the hull out from the mould certain precautions are to be taken. Light hammering to encourage mould release or alignment of two moldings should be carried out with a rubber mallet. Hammered fastening or blows with a metal hammer will shatter the laminate.
Day 19
As per schedule both the hulls are finished by 7 th of Dec. Once both the hulls are made they are to be connected by cross structures. We can use wither round pipes of square pipes. But its better to have square pipes since this will prevent any kind of bulging on the deck when load is coming on top. We can use 2" square MS pipes coated with corrosion resistant metal primer and paint. These pipes can be connected to the hull at the both ends by welding to the flat bars which are bolted to the hull.
Day 20
When aligning the hull make sure to align the hulls diagonally as well as along the length. It would be better to fit the center one first and then the first and last one. Checking the diagonal length is very important, since any deviation in the hull shape will be reflected at this stage.
Day 21
Now since both the hulls are connected, we can start laying the deck. Before that the position of the battery has to be finalized and the battery holding plate has to be made accordingly inside the hull. Keep the height of the battery as low as possible. Plywood for deck should be of marine quality. Top side of the plywood has to be coated with FRP. The position of the battery is fixed so that the boat has minimum trim when fully loaded.
Day 22
The deck has to be connected to hull by layering with FRP. One layer of FRP is coated on the edges of the deck and the hull forming a water tight edge. Similarly, the cuts made on the hull for fixing the cross structure also need to be layered with FRP.When all the layering works are over we can start the flooring. This has to be done at the earlier stage because the base of the stainless steel structures will be coming on top of the wooden flooring. Flooring can be done using teak, cut into strips of 50 mm width and 8 mm thickness. After polishing this will give a better finish. Once the flooring is over we can start the SS work. Polishing of the wooden flooring is done only after finishing all the works.
Day 23
For SS works stainless steel of 304 grade is to be used. If poor quality steel is used then there are chances of black spots coming at a later stage. First thing to be fit was the main pillars running from the front to the aft end, and the two aft end pillars.Once the position of these are finalized major part will be over. As per our design we needed SS pipes of 75 mm dia. Also in the front, the pillars were in a curved shape. Using hydraulic bending machines we can get these shapes very accurately. Skill of the SS welders are very important for this work, since any small change in any position will be carried over to all the subsequent welding. Reworking is the most important thing to be avoided since it includes wastage of time and money
Day 24
One of the major things to be kept in mind while designing a solar boat is that the hull should be so optimizes that there should be very less effort to move the hull. The wind resistance should be reduced. Weight of the boat should be very less. Keeping all this factors we had left a lot of open spaces in the design to reduce the wind drag. Also the top roofing is done with thin aluminum sheets.
Day 25
Solar panels were supposed to be supported on angle bars. There should be sufficient gap between the panels and the roof.This is to allow the air flow under the panels. Fans are to be provided to suck air from under the panels to the outside.
Day 26
stainless sheets are initially welded to the pipes. these are 120 mm width plates. Now we can fix the aluminium sheets on to this ss sheets. These roof sheets are not supposed to carry any loads. So they can be very thin sheets.
Day 27
To save time we can get all the known pieces in advance.Then first all the joints are spot welded. After checking for perpendicularity and all the final welding is done. Once the welding is done there will be dark spots generated around the welds. This is removed by a process called buffing. For buffing different types of grinding wheels like cloth wheel etc. are used. Then by the sequential application of these wheels the joints can be made to look same as the original.
Day 28
Flooring of the boat is done using teak. We got it cut in sizes of 8 mm thick and 50 mm width. The it is laid as shown in the pictures below. Once laying the wood is completed it is smoothened by grinding.To give a better look to the wood we have to coat it with marine specific coatings. There are different types of quality coats are available in the market. We should always be careful to take the best one. We are planing to use MRF coating.
Day 29
Next thing had to do was the seating. We had planed earlier to make custom made seats using marine quality leather material. Frame for the seats is also done in SS only. Cushion will be done by the experts. Cushion works are done on marine plywood. Then these plywood's are bolted on the frame work.
Day 30
For flooring the pieces are aligned in the longitudinal direction symmetrical to the center line. normally this work has to be finished before any structure is constructed on the deck. Then once the structure is constructed, there are bases available which can be used to hide the bolts and nuts used to bolt the structures to the deck. But this time we have done the other way first. We were planing to put the putty on the holes and thus hide the bolts and all. Once the deck is laid care must be taken when performing the welding to avoid the hot flux from falling on the deck. This will leave dark spots on the wood which will be very difficult to remove later.
Day 31
After grinding the floor looks as shown in the picture below. Polishing of the floor will be done only in the end.
Day 32
We got the engines today. We are the resellers for the Torqeedo engines in India. These are are imported from Germany. It looks very stylish when fitted on to the hull.
Day 32
Hull is spray painted with one coat of primer and two coats of Poly urethane paint. To protect it from scratches Teflon coating is applied on to it.
Day 33
Once the painting and Teflon coating is finished the fender and bollard is fitted on to the deck. Navigation console we were planing to give wooden finish for the console and stainless steel as the support structure. Please refer to the pictures below.
GETTING READY TO LAUNCH
Finally the day came. After long waiting today :- 24-01-2009 the boat will be launched to water for test run.
LAUNCHING
The boat is launched in the beautiful waters at Thalayolaparambil.
TRIALS
(7th Feb 2009) The second trial of solar boat was done with Malcom Moss, President of Electric Boat Association UK and founder of Moss Solar Trust. We did a the test upstream and downstream at various steps of the motors speed. The highest speed achieved against upstream (0.8 Kmph current) was 11.4 Kmph. Check out second trial video for more details.
The first trials of the solar boat prototype was done at the beautiful waters are Thalayolaparambil. The result was more than the expectations. Check out the first trial video] for more details.
Finished Product
The finished solar boat.
