Canoe Hull Design
Some of you may be aware of the annual Civil Engineering competition that involves producing a concrete canoe. The competition involves several aspects, but the most prominent is the canoe race. Therefore, a fast and efficient hull design is required.
I'm currently working on our design for this coming year. I would like some recommendations for books and software that would be helpful for creating an optimal canoe hull design. I currently have been reading over a Naval Architecture book that I picked up, but it covers mostly large displacement craft. Iím familiar with Rhino and AutoCAD, but I have no experience with marine software.
The canoes specifications are approximately 20' long with a max beam 28 - 32". I would really like to get a couple of good reads that would help me with the basics.
Any insight is greatly appreciated.
do they say what type of concrete it has to be? because I recently saw floating concrete which has tiny hollow spheres to lower the density, but strength is not compromised. Materials are part of design
The Concrete Mix design is somewhat regulated for the competition. They regulate the amount of Portland cement that has to be maintained in the binder along with the percent passing blends for the aggregates. However, they do not regulate the amounts and types of mineral admixtures that can be used in the concrete.
Over the past two years we have developed a mix design through research and testing that will perform as needed. The mix utilizes lightweight glass microspheres and carbon fiber materials for aggregate and reinforcement, respectively.
As a Civil Engineering student, we are educated in the properties of concrete and its capabilities. Therefore, I'm really are not concerned about the concrete mix design. However, I have no prior experience with the hull design required for this project. Only having the prior knowledge from being around powerboats from youth, I'm currently not of skill.
Any advice on where to look to learn the basics for a canoe type hull design will much appreciated.
Keeping it as light as possible should be on your to do list. An engineer I spoke with recently at Schlumberger's off shore cementing business in the oil industry had a similar design with glass spheres that was less than the density of water. Keep the density down.
I dont know much about canoe design but as a former D1 rower and mechanical engineer I cant tell you what makes those boats go fast.
You want to minimize your wetted surface because friction kills boat speed. To do this you need a rounded hull (which will be less stable) and to design for the total weight. In rowing we have to average our weights and find a hull designed for that it. Too heavy and the boat sits too low in the water, too light and you cant set it up.
Slender boats go faster because they have less of a cross section. Longer boats go straight which you will need as the man in the stern has a serious mechanical advantage when it comes to canoe steering.
Different boat designs will have different properties, such a run or acceleration. Empacher is a company in germany that makes really fast shells and their hull shape has stood the test of time, vespolli in in the US. Hudson boatworks in canada makes great shells and my friends on our national team swear by them. I would contact those companies because a canoe stroke is similar to a rowing stroke in that its a surging motion.
If they are no help, go to a local rowing club and take measurements. That is a great place to start because those boat designs have been perfected over the years.
Also look into dragon boat racing which is popular in hawaii. Those boats are very slender and long, but use an outrigger for stability. You can find links on both at row2k.com
As for the racing part, you can win a race with lesser equipment and better technique. My advice to you is to find a way to get yourself stable, either by kneeling in the boat or with foot stops if your seated and use a body swing. along with an arm draw. The longer your oar is in the water the more you can accelerate the boat. Completely cover the oar at full reach with your body bent to 45, then swing your body back, then draw with the arms and let it come out naturally. The idea is to maintain connection so you pull the boat past the oar. Going deep prevents you from "ripping" which is when you move water as opposed to the boat. Thats how the dragon boat guys do it. If you have a partner in the boat, make sure your timing is on.
Try training by tying a rope to a coffee can and trowing it off the back of a normal canoe. That will add a ton of resistance and make your concrete canoe feel light.
Hope that helps.
Here's a good start for you:
These pieces are by John Winters, who is one of the most respected designers of canoes in the modern fashion. John is a naval architect by training and is credited with bringing modern N.A. design and analysis tools to the canoe industry.
I design canoes and kayaks as well as other small craft and I can give you some basics that will get you rolling to a workable design for your race.
A 20' canoe with a 28-32" beam is going to be on the tippy side of things unless you guys can successfully sit on the bottom of the boat. The more you raise your centers of gravity the more tippy it will become. With some practice, you can probably get to the point where you are kneeling in the boat with a fat foam cushion under your butt for support.
The kneeling position is much more powerful for paddling as you can take a longer stroke and apply more power to each stroke.
There is a simple design software available called Bearboat Pro which would be perfect for your needs in creating a smooth hulled canoe form. Google that name and download the package. It has documentation and you will be able to get a shape in process which you can refine as you go.
You may wish to look at the shapes of what are called Tripping Canoes for design cues. They are fast in the water while retaining a decent measure of stability. Pure racing C2 canoes are not as stable and would be a real problem for your team if you are not experienced paddlers of this type of boat.
Anyway, read the Winters stuff, get wet with the Bearboat package and then get back to us. I'll be happy to help you with the project.
This takes you through the design process with some good reference to tools used:
This shows the boat development again with good design reference:
I believe the boat only came middle of the field and have no feedback from the race day. I suspect the engines used make a big difference on race day. I thought the design paper was first class but do not know how well it was presented.
I know the idea is to learn about concrete and design process but I felt the UT effort did not put much emphasis into tuning the engine. As far as boat performance goes this is a vital feature. It also involves a good deal of engineering.
Do the rules specify it has to be paddled. A prop is more efficient.
Reduce your gunwale height to the bare minumum you need. I see a lot of these concrete boat designs carrying around tens of pounds more than they need to just because they have that "canoe shape" stuck in their minds. This reduced weight will allow you to put the remaining weight where it will do the most good.
The Godzilla optimisation that Corey M did for the 2008 UT canoe was based on infinite depth of water. I did notice in the photos that he posted on race day the water was quite shallow. This could be something to take into account in future design exercises.
Also you will see in the "Racing Camoe" thread I made a recommendation on the stability based on my experience with other boats. It would be good to get feedback on how the stability related to actual feel in the water. If reduced stability can be managed then it is one way to gain speed.
Is the race a straight sprint? Are there turns, bouys, obstacle course type stuff? How long does it take? How many people per canoe? Is the race on a lake, river or rapids?
What are the other aspects?
Be careful of overbuilding.
Thanks for all the input guys. I'm sorry for being kind of vague in the description of the competition. The reason being is that some of the rules and regulations change from year to year and I can’t be certain until the release of this year’s rules and regulations in the Fall. Although, they do generally change the rules and regulations year-to-year, they usually are very minor changes.
Here some of the specifics from last year:
600m slalom/endurance (sprint out to 7 buoys spaced 10m apart - sprint to - 3 buoys spaced 40m apart - sprint to finish) For this race you buoys are arrayed in a pentagon type form, being you transverse through a large pentagon from start to finish.
200m sprint (100m out, 180 deg. turn, 100m back)
The canoe has to be paddled. It cannot be rowed nor have any fixed mount attached to the boat for a pivot.
The canoes dimensions are regulated as previously mentioned:
Max Length: 20'
Max Beam: 28 - 32"
Other then these specifications it’s up to the team's discretion for determining the gunwale height, rocker, and all the other perimeters for the hull design. These dimensions may change slightly from year-to-year, but for now I will use these numbers for design purposes and then adjust if needed.
I would like the gunwale height to remain as low as possible for weight savings. Most of the competitive concrete canoes will weigh in the 130-140 lbs. range finished. This is achieved using light weight aggregate and a nominal hull thickness of approx. 1/2 inch. Theoretically, with our mix design we should be able to build to canoe to 120-125 lbs. bare hull. However, the competition maintains a safety factor that involves the canoe being able to resurface and float 2 inchs above the water line at the bow and stern after being completely submerged. Therefore, the canoe has to have concrete encapsulated buoyancy in the last two feet of the bow and stern to maintain this standard. This generally adds 10-15 lbs. to the canoe. The specific weights of most concrete mix designs will generally be around 45-55 lbf/ft^3.
For further interest, check out www.concretecanoe.org, scroll to the bottom of the page to enter. This site has information on the competition and previous winners.
Thank You for the references and your help. Even though the actual competition doesn’t take place till next March. I want to get as much done this summer as possible, because I will be occupied with classes once the Fall semester kicks off.
For paddling technique some teams make seats out of foam blocks and paddle seated. I understand the kneeling technique is more effective and we will try to employ this in practice.
I was planning on building a practice canoe out of the mold left from last year’s canoe. I would like to build it by laying up fiberglass within the mold, but it appears to be too expensive for our budget. Every team is responsible for raising the funding and materials through sponsorship and donation, so the budget is a limiting factor. After getting a quote of $900 for the fiberglass materials, it looks like I may have to build the practice canoe using the Carvel Method of strip planking and then laminating.
I have the mold left over from last year’s canoe. However, I don’t have the file or any notes on the hull design. The guy who designed it last year graduated and is out of touch. I will attach a picture of the last year’s mold. Any further help in developing an improved hull design for this year is greatly appreciated. Thank You
Note: This is a picture of the mold before we trimmed the excess fiberglass off around the gunwale. The gunwale height is around 13.5 inchs.
Great project. I now wish I had participated in my own engineering school's contest over 25 years ago. Though they did win some of the events even without me, it looked like a fun contest. I have since built 9 boats, including 7 canoes or sea kayaks.
You might go to this website about sea kayaks which has a lot of technical articles, and even links to free design and performance software specificity for canoes and kayaks: http://www.marinerkayaks.com/
The advise you have received is good. Keep it as light as possible, keep your CG low so the hull can be more rounded (less wetted area=less drag) and get the largest length to width ratio as the rules allow. Go look at the hull lines of racing canoes and you will get the idea.
I have thought that if you actually weld a structural frame from 3/8 rebar (or even hollow tube?) forming a kind of truss or structural shell it would be lightest. You have the rebar only at the gunwales and the keel (with thwarts at the appropriate places) and then use light wire mesh to form the skin with a special formulation of concrete that would allow you to make it real thin (like 1/4-3/8 inch). This should give the lightest hull. Though you would need to review the rules to see if welding is actually allowed, you may have to use wire lashing instead.
Good luck, keep us informed on your progress.
OK, let's look at these things in order and get some kind of organized design process going.
First of all, virtually everything you were told by Rick Willoughby is going to effective when it comes to getting that optimal hull. My caveat on that would be, that the "optimal hull" will not always win the race for a wide group of reasons; mostly having to do with the dudes in the boat when the flag drops at the start. The best hull on the planet won't mean squat if the guys aboard are complete doofs, or the stability has been trimmed to the point where only Oly class guys can make it work.
The mold shown is not what I would have arrived at should I be designing a fast (and moderately stable canoe for this kind of competition. I'd much rather see a boat that is tapered at both ends than a boat with a square stern section such as the one shown.
You only have so much horsepower available and it is highly unlikely that a square sterned design will see anything even close to the kind of power that would make use of the form. Putting on a small engine or a nice piece of sail area and we can talk about square sterns, otherwise, they are not the best.
The gunnel height of the lowest point in the hull can be as low as 9" above the water surface when fully loaded and still provide a decent degree of preventative action against wave associated swamping. If you think that a couple of extra inches of lightweight concrete is heavy to cart around, try doing the course with 10 gallons of water sloshing about... if you can keep the boat from totally going over.
It would be good to review any video of previous years to see what happens to the water when the race starts. If it gets whipped into a churning mess with confused waves, then a slightly higher gunnel will save you in big ways. If it stays pretty calm, then you can trim the weight and go with a lower gunnel/shear line without messing with shipping huge amounts of water. If it is windy and there are waves present without any boats doing anything, then nothing works better than a boat that can ride decently high and dry.
Assign one of the paddlers to bailing and you cut your power potential by one fourth. Gunnel height is important, though it all depends on the course rules and the conditions. Gotta keep things in balance to have a winning effort.
Build the prototype with marine plywood in a multichine design. It's way faster than any other building method, will cost the least with simple taped seams and allow you to get a feel for a boat of the type you are proposing. The difference in performance between a slick, smooth chined design and a nicely crafted, mutichine design is about 1-1.5%, so the results will closely match whatever you will do with the concrete version.
Bearboat Pro does not do multichine designs, but Carlson's Hulls will do that and it is incredibly easy to get to know. www.carlsondesign.com about halfway down the page where the boat and sail software is located. Write me a PM if you'd like to have some pointers.
Crew assignments... The forward three guys in the boat are paddlers, pure and simple. They do what the steersman says, they keep their weight low and centered and pull with all they have in measured effort for the whole race.
The guy in the way back end of the boat is the steersman and he is in charge of the boat. He says when to crank it and when to cruise for getting a breath. He steers the boat and sees all that is in front of him. This guy needs to be calm, yet highly competitive and ready to bark out orders when they are needed. It helps if he knows the various basic canoe strokes really well, so he can tell the other guys what to do and when.
This should be one really fun challenge for you guys.
I would like to know how points are awarded. The race is only one part of the competition. I know the boat has to perform with two man, maybe two women and four man/woman crew. So weight and power level change.
The UT design covered many considerations on the basic theme of a canoe. There are more radical designs that could be a lot faster.
The fastest human powered boats are rowing sculls. Problem is these need a skillful rower with oars for stabilising. The next best is an outrigger canoe which has outrigger/s for stabilising.
There are some recent ideas on the forum regarding boats that look like monohulls on top but are actually trimarans under water:
If the rules permit you could make a very fast and stable canoe using this concept. Sitting position would be like an OC where you have a foot well below the seating level and you can lock into place.
Unfortunately, I donít think that that type of design would work. The canoe by rules and regulations has to have all its reinforcement encapsulated in concrete. They do allow reinforcement like chicken wire, but itís rarely used in these builds due to its weight and difference in modulus of elasticity compared to the concrete. Even though, the chicken wire may be stronger than some of the high. tech reinforcements its can actually cause cracking in this type of concrete.
Most of the reinforcements that are utilized are some type of fiberglass and/or carbon fiber mesh or scrim and they have better properties for this application. If you used a small rebar for structural strength, it would then have to be encapsulated in concrete. To encapsulate the rebar it would increase the thickness of the hull and add more weight by way of concrete.
This project can be a lot of fun, but it is also a lot of work. With fewer students than most engineering programs to work on these projects, we have to individually work harder than most schools to compete at the same level. That combined with demand for these projects and that of the course schedule can be hard to balance at times.
The students from the academic year before last (2007) designed a hull as you mentioned (tapered at both ends). The mold shown is actually a redesign of that first hull. From what I have been told, that 2007 design was really fast in a straight line, but they couldn't get it to turn. So, for last yearís hull redesigned the hull with a transom like square end, intending for it to be easier to turn. The same student that designed the hull in 2007 designed the 2008 hull that is resembled in the mold and felt the need to change it.
I must say, this is all word of mouth because at the time I wasn't in the CE program yet. With that being said, the fact they couldn't get it to turn (2007) could have very well been due to poor paddling technique. I can't say for sure. I have the 2007 hull design on file in Rhino. If you would like to take a look at it I would be happy to e-mail it to you.
On another note, most teams chose to steer their canoe from the bow by sticking the paddle in the water perpendicular the direction of movement and then paddle the stern around. This technique can be seen in this link http://www.youtube.com/watch?v=wt6IYHq3o7Q .
I understand that the paddling technique can be just as important as the hull design itself. As soon as we decide on a hull design and how to build a practice canoe economically we will be practicing diligently. You mentioned building a canoe like that of our mold with a hard chine instead of a round chine as seen. I have noticed that the recent trend for the canoe hull designs has actually been to use a hard chine. I understand that the hard chine gives you more righting moment and thus better stability over a round chine, but doesnít a hard chine increase drag?
I really like your idea for the canoe. Iím not familiar at all with that type of hull, but I have never seen anything like it in the concrete canoe competitions. If that type of design does reduce drag by 25% over a more traditional hull design thatís impressive.
My only concern would be with strength issues with the concrete. Concrete is very strong in compression, but usually is only has 10% of its compressive strength in tension and 15% in flexure. With that being said, we have to be aware of how the forces will be exerted on the concrete. The type of concrete we use in these builds cracks very easily in tension even with the high tech. reinforcement purely due to the concreteís properties.
The sharp radiuses in the hull concern me as they concentrate forces at the bend. We could supplement this by building up that area with concrete, but we would be adding more weight. Additionally, is the surface area of that hull greater or less than that of a hull of the same overall dimensions? Iím just trying to determine if this hull type would require more concrete to build. Also, do you feel that the hullís efficiency would still be advantageous with the possibility of additional weight?
Thank You all for your insight. Iím currently enrolled in two classes that will not be ending until early July. So, unfortunately I will not be unable to devote myself to covering the references you have given me until that time. However, once classes are over I will be working on learning the material diligently.
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