Canoe Hull Design

Fiberglass or aluminum window screen might work well for reinforcement.

Any canoe will work for practicing. One is not that much different from the other, especially in paddling techniques or getting in shape.

 

Concrete structures are usually pre-stressed so the structure will work in both tension and compression. I have attached a couple of images from the UT site linked above showing the layup and pre-stressing jig. This is a mini system compared with what is usually used for bridge structures.

You should do yourself a favour and copy selected images of the design and build before Corey kills the site. Like I said the boat looked first class and worked well but the crew or presentations may not have been up to scratch. I have no idea how points are awarded. Clearly the UT team had some great fun on race day so it could not be all bad.

If you want to rank well and make the nationals then you need to know how points are awarded and put someone in charge of each aspect. Also someone responsible for programming (planning and scheduling) with a big stick to keep things on time.

Rick W.

 

Hello SouthernEngr
Just my personal experience crossing Crystal River bay on a Manatee watching excursion on a "sea kayak". This plastic affair was nothing more than a extra thick surfboard with molded seat and foot wells. I tried kneeling on the thing to give some muscles a rest and spent too much energy trying to stay balanced. Much too unstable to do that, so I went back to setting my tush where it was designed to be placed. Much easier to sustain balance. The difference in center of mass height was illuminating.


Cheers,
BobG

 

Hello Guys,

Sorry it has been so long since I have been back to the forum. I had two summer classes to contend with and I was not able to get much accomplished on the canoe hull design until this last week.

I have been playing around with Delftship, Michlet, and Godzilla as Rick and others had advised. I have become somewhat familiar with their form and function. However, I'm having a few problems with the software and I also have a few design questions.

1) What would be the recommended amount of rocker forward and aft for the 20' canoe? Tracking is important because, although we will be practicing our paddling technique, most of the paddlers will start out green. In contrast, we need the maneuverability to make 90 and 180 degree turns while retaining as much forward momentum as possible.

2) Is it advisable to cut away the deadwood at the bow after Godzilla optimizes to reduce wetted surface and help with maneuverability? If so, how drastic of a cut would be advised?

3) I'm getting an "Invalid Numeric Input" error when I try in import the Godzilla offset text files into Delftship. I have the units set to metric. What am I doing wrong?

4) What’s the easiest way to produce a multi-chine or hard chine hull in Godzilla? I would like to compare the optimization of the two to an optimized round chine.

5) How do you draw a multi or hard chine hull using Delftship? When I enter my dimensions it automatically draws a round chine hull. I have been modifying Chris's example, but I have been unsuccessful in drawing one myself.

6) I was thinking about incorporating some tumblehome in the mid section to help the paddlers. Do you think this is necessary for an approx 30" beamed canoe?

Sorry for the gamut of questions, I'm just trying to get this done over the next week or so. Thanks

 

Work through this:
http://boatdesign.net/forums/showthread.php?t=19110&highlight=concrete
It has fbm files you can use to see what is done to get chines and the like.

Have you ruled out the faux-tri concept. This will have much less drag. You would need to check the rules on hull shape carefully.

Rick W

 

Rick,

I had previously looked over that thread, but I apparently missed where you explained how to get those shapes in Godzilla. I like the tri-maran design and tried to draw it in Delftship without any success. How do you draw a hull shape like that in Delftship?

Have you ever seen for mentioned that error when trying to import the offsets into Delftship?

 

Never seen the import problem.

Give me a design weight, maximum length and target speed then I will use Godzilla to produce the optimum hard chine hull. I will send you an fbm file from this.

Delftship takes a bit of experience. You have to remember you are working with surfaces.

Rick W.

 

Rick,

I really appreciate all your help. Here are the particulars:

D = 770 lbs. = 0.35 m^3 (4 paddlers)
L = 19.98 ft = 6.0913 m
B = 28 - 32 inchs = 0.711 - 0.813
I would assume the target speed should be the hull speed at around 6mph = 2.68 m/s?

These are based on the regulations from this previous academic year. The regulations for this coming year will not be released until October when I expect a nominal change. However, I want to establish a good design based on this past year to build a practice canoe off of while also learning how to do the design and use the software. Then when the regulations are released, I will be able to make any needed adjustments and produce a final design efficently. In theory this should save me alot of time that I could then devote to other areas of the project.

 

I remembered I had already done this one based on Corey's data.

Rick W.

 

Rick,

Have you ever built one yourself? If so, how did it handle compared to a traditional canoe?

 

The KM is low because I have used little immersion. The outrigger hulls may need to go a bit deeper for two up operation - just touching. With four up there will be more power available to overcome outrigger drag so they can be deeper.

The issue with this design will be locating the paddlers so they can stroke clear of the gunwale.

I have built lots of pedal powered boats. This is my latest trimaran design in operation:
http://www.youtube.com/watch?v=KOPSXWicBK0
It has a KMT of 0.1m on a 0.1m draft. The outriggers are set wide and separate to the main hull but the faux-tri works the same. The faux-tri does have some initial stability though and will stiffen up as it rolls. I have not done a full roll analysis but I expect it would be much better than a conventional canoe.

This is a 20ft pedal boat without stabilisers:
http://www.youtube.com/watch?v=PYoW3XjHRbw
I did not like it because it felt skittish but it worked fine. It has a KMT around 400mm. The CofG is 380mm so not much margin. It stiffens a little but I did not test the limit as it was too cold to get wet.

If you think the rules will permit it you would be better off building ply version of the faux-tri to get geometry sorted. From a speed and tracking perspective no rocker is the best but you need to see how well it can be turned.

Rick W

 

Rick,

The boat you built in the first video looks like fun. How do you recommend building the tri-canoe out of plywood. Stitch and glue, cold-mold?

Check out this hull and tell me what you think. I was shooting for a hard chine using the shape constraints in Godzilla and landed somewhere in the middle. However, the particulars looked pretty good.

Is there any way to get godzilla to optimize for rocker?

 

I would not even bother with stitch and glue unless it is something you are familiar with. Just use outdoor ply and basic framing. Screw and glue with a good polyurethane glue. The aim is to make it quick, use it for testing and checking that it suits 2 and 4 paddlers. I think it will be more complex to make in concrete than a normal canoe.

I will look at your hull later and compare with the faux-tri.

You have not constrained the the hull shape factors to get the hard choine. The chine is the second of the 7 factors. The limits need to be 0 and 0 and the seed also 0. The forebody and aftbody shape can be constrained similarly to produce rocker. You will need to read the manual to find which ones as it is not something I do regularly. Rocker slows that boat down for uncertain gain. Unless you are doing something like a slalom I think tracking is more important. Just learn how to use the paddle to turn fast.

Rick W

 

THe attached compares your GodHull with the central hull of the faux-tri through speed range. I have arrowed what you could expect from two man and four man crew with fit paddlers. The f-tri is about 0.5 knot faster at both conditions.

Rick W.

 

others with more knowlage than I can answer your software question, but having built a number of canoes and sea kayaks I thought I would comment about your hull design:

A canoe that big will have to have a fair amount of rocker or it will not turn well at all. One compromise so it tracks well would be to put more rocker in the bow ("cut out the deadwood" as you say) and have the stern keel end in a skeg. Then presuming you have time to test it out, trim off some of the skeg if it too difficult to turn.

Why are you considering multi-chine? A hard chine hull will have more wetted area and weigh slightly more than a smooth rounded hull. On a multi-chine hull there is very little differance between it and smooth hulls of similar size and shape. There is no performance advantage to multi-chine in a canoe, it is done as a manufacutring accomodation.

If you built it 30 in wide you will need tumble home. That is very wide for a "racing" canoe. I consider anything wider than 22 inches as too wide, and I am not small (I weight about 200 lbs). A canoe that wide forces the paddler to lean way out over the gunwale to get a good power stroke. You should consider keeping the width to under 24 inches and make the bottom more flat to compensate for the lost stablity. You will not need the tumble home, the canoe will have less drag (better finess ratio), and the paddlers willnot have to lean out as far to get good purchase on the water.

Also do not neglet the paddle, most of the cheap recrational plastic paddles are junk. If you can not get the high tech carbon racing paddles, than use the smooth wood paddles. They are not as light as the plastic ones but the smooth blade is way more efficient and you get better thrust out of them.

Good luck