Frequently Asked Questions
Do you sell boat plans and designs?
Yes. We do not sell our design rights but we do sell a license to build a boat. So when you order a kit you get the right to build one boat. We retain ownership of all copyright and intellectual property. That way we can sell the same design to others which allows us to keep the cost down. If you want an exclusive one off design we can do it for you but it will incure extra by the hour design costs. So to summarise our range of DIY Flat pack kits will not give you any ownership rights to the design, just the right to build 1 boat per kit.
Is a Jig required to build your kits?
No. Our kits are designed to be pulled up on the floor. Once done all that is needed is some props to stabilise the hull.
Is any plate rolling required?
No. The plates are developable so they pull into shape without any prior rolling.
Is any press brake bending required?
Yes. Some parts require bending. We supply a bending drawing and all parts that require bending are marked with the bend centre line and bend angle. Pipe bending is also required for fuel pipes and hand rails.
Do you supply flat pack kits?
Yes. We can supply the kit which includes all aluminium components for the build. If you would like get the kit cut yourself you will need to purchase the design files. This will also allow you to build multiple vessels.
Can you supply a stage 1 bare hull?
No. However we can arrange for one of our trusted builders or a builder of your choice to do this for you. We will arrange for the kit to be delivered to the builders workshop at which stage you can organise with them any further details.
What format are your cutting files and drawings?
Cutting files are Autocad 2004 format, drawings are pdf format A3 size. We also supply you with a hardcopy (printed A3 sheets) of all the drawings.
If I buy the unlimited build option can I sell kits?
No. You can build an unlimited number of boats and sell them, but you can not sell the cutting files or sell flat pack kits. See our Terms and Conditions.
Can I give the cutting files to my boat builder?
No. You can only give the files to a material supplier and you must ensure that they respect our copyright. If your builder has in house cutting then you must check with us first. See our Terms and Conditions.
All these plate boats look the same, what makes you different from the others?
- We allow you to deal with the builder of your choice and allow you to buy your own materials if you are able to.
- We are operated by people with design skills whereas most boat builders are run by people with manufacturing skills. Where they have to pay for design development, we do not. We can spend as much time as it takes getting a design right on the computer without worrying about the cost. This allows us to get the design right in terms of performance, ease of production and minimising wastage.
- We use the latest computer software to individually design each boat. Each hull shape is custom designed for its length and configuration to ensure it performs safely and efficiently. Some builders (not all of them) try to save cost by modifying existing designs themselves rather than paying a Naval Architect to design them properly.
- You get to deal directly with the designer of your boat and can have all your technical questions answered.
What sort of questions should I ask other builders?
Some questions to ask would be who designed the boat, was it specifically designed for its length and configuration or is it a different hull shape that has been stretched or otherwise modified, how far will it heal over with half a tank of fuel and two people standing to one side, how far can it heal before it rolls over, what warranty is offered and what are the exclusions, are they boat building specialists, is it hand cut or computer cut, what code or rules was it designed to. If the builder or salesman can answer these questions then it is a good sign. Also many builders use the same designer so ring the designer and ask them who their preferred builder is.
What should we look for in a hull shape?
It is quite simple to get an idea of how a hull will perform by just looking at it. In order for a boat to move forward it must displace water. When it lands off a wave it must displace water. The easier it can displace or move the water out of the way the better the performance. If you are only going to use your boat on a river or estuary where waves are small then a fine entry under the water line is probably most important. However for open water use you should also consider how a boat will land when falling off a swell or punching into a wave. Look at the hull and see how easily the water can be displaced. Check the shape above the waterline. Flat sections will cause a hard landing, steep deadrises will soften it – but beware of steep deadrises with flat sections just above the waterline. The boat will just keep going down until it bottoms out on the flat section – ouch! So just look at the hull shape above and below the waterline and try to visualise how the water will be displaced. This applies to boats made of any material.
Is your hull shape based on a Jackman Design?
No. Our hull shape was developed by us and is exclusive to us. If you are considering buying a Jackman design do your research and make sure it’s a genuine Jackman hull shape. Since Dave Jackman used to give out his designs on mylar film, it was very easy for people to copy them and modify them. So what started out as a Jackman Design may be someone else’s modified version. For example someone may have taken a 5m Jackman hull and just added 1m to the back and then call it a 6m Jackman. This drastically changes the proportions of the hull shape and could result in poor stability and handling. It would be a different shape to a genuine 6m Jackman. Genuine Jackman designs are great but modified ones could be a disaster. So do your homework. One simple test is to just ask for proof of purchase/ownership of the design rights, or at least make sure they have a proven product.
I have heard that reverse angled chines improve stability and performance so why don’t you use them?
This type of claim is very general. We tried to research exactly what aspects of performance and stability were improved and by how much and could not find any clear answers. We therefore decided to spend a little time and modeled an angled chine on our hull shape to see what effect it had on stability. We found that the amount a 6.5m boat would heel with 2 persons sitting on the side was reduced by only 0.7 degrees. Other than that we found no other benefit. We also found that the angled chine caused an increase in wetted surface area of around 8-10% which would increase skin friction resistance and therefore reduce speed and increase running costs. Considering the power to weight ratio (and speed) of the typical aluminium or fibreglass fishing boat, we don’t believe that there would be any air cushioning effects. There may however be increased drag due to turbulence at the entry to the angled area. The angled chine also makes it harder to displace water sideways when landing off a wave so the rough weather ride may be worse. Add to that the fact that commercial boats don’t have them and that was enough for us to decide not to use them. If you are considering buying a boat with this sort of chine then ask the seller exactly what aspects of performance are improved and by how much. Also ask to see some proof of their claims in terms of calculations or test data. However if you really want them we can design a kit with them on the condition that you don’t complain to us if you don’t like the ride.
Can a ballast tank be used to improve stability?
A ballast tank will improve at rest stability by making the back of the boat heavier and causing the chines to sit deeper in the water. The problem is that they usually drain when under way so they will not improve handling while underway, unless you keep them full but that means carrying around all that extra weight.
Does a sealed deck mean a boat wont sink if it gets a hole in the hull?
Most likely the boat will sink. When the bottom of a boat is damaged the deck effectively becomes the new bottom. Most people think that if the deck is sealed then the boat wont sink. That is only the case if water can not get onto the top of the deck. If your boat has freeing ports, scuppers, a transom door, a floodable kill tank, or a tank hatch that’s not water tight then water can get onto the deck and it will most likely sink. Of course if it has floatation or water tight compartments then this is less likely but most recreational boats don’t have them. The good news for aluminium boat owners is that aluminium is a ductile material meaning that it is more likely to bend or deform upon impact rather than crack or shatter like brittle materials. For boats without freeing ports & scuppers, while they may be safer if damaged, they are far less safe if swamped by a wave. If the water cant escape from the deck area then the boat will roll over due to the “free surface moment”. The chance of being swamped by a wave is higher than getting a hole in your boat so scuppers or freeing ports are of vital importance. Have you tested your bilge pump lately?
How can I tell if a boat has floating frames or not?
Just look at the bottom plate from underneath. Even with a 5mm bottom you should still be able to see the welding penetration marks. If you cant see any then the frames most likely aren’t welded to the plate. You should also be able to see them for the stiffeners. Alternatively you can ask the builder to inspect a boat under construction or see their production drawings.
What does "rocking the chines" mean?
This is a phrase used to describe the situation where a boat will sit to one side when under way and then rock over to the other side. It is caused by poor hull design resulting in the chines being out of the water when planing. The boat will fall to one side with only one chine in the water. A change in direction, or hitting a wave or swell can cause the boat to rock over to the other side. This can be a dangerous situation as the performance of the boat can become unpredictable.
Does the requirement for a HIN plate assure quality?
No. The HIN plate should deter boat theft in a similar way to car VIN’s but there are no independent design or quality checks before one is issued and fitted.
I have heard some builders say that it is cheaper to cut the parts out by hand rather than paying for computer controlled cutting?
Cutting just a few simple shapes by hand could possibly be cheaper but cutting complex shapes using computer controlled machinery is not only cheaper in the long run, but also minimises wastage and eliminates human cutting errors. A typical 6.5m boat has over 120 cut parts with over 570m of cutting length. Additionally manual cutting of many of our complex parts would require sawing, drilling and grinding processes on the one part. The CNC machine produces the part in just one efficient process. We also have the machine print alignment marks on our parts. The total length of our plate markings exceeds 120m. Making these marks manually would require measuring at least 2 points from a reference and then drawing the line between the points for each mark. This would be very time consuming and be subject to human error.
What are the alignment marks used for?
The alignment marks show the builder where the parts should be located. Using them minimises assembly errors and ensures that each boat is built the same way. It also reduces cost by speeding up the build process since the builder doesn’t need to refer to drawings or make measurements as much as he would without them.
How much more would it cost to have a boat built with a 6mm bottom?
Only the extra material Cost. We have strategically arranged our parts on standard sheet sizes so that material thicknesses in specific areas can be easily changed. There will be no additional design costs.
Which Brand of Engine Should I Choose?
We do not have any alliances with any engine manufacturer so this decision will have to be your choice. We can source prices from any manufacturer and try to find an engine that best suits your needs and budget.
Got a question?
Email us your question and we will answer you directly as well as post the question and our answer on this page.
CNC Marine We Believe in Making Boat Building Easier
Phone - 1300 548 262