Canoe Hull Design

I was thinking about the chart and realised it is for the 370kg case. This is the 4 man. It needs to be run at lighter displacement to get the actual result for 2 man operation. This is something you can check.

Rick W

 

Rick,

I finally found the section in the Godzilla manual that discusses the shape constraints in detail. It’s actually in part 12, "Godzilla Examples." I'm going to work on modifying the shape to see what kind of results I obtain.

My only reservation about the tri-canoe is the additional material/weight that would be required in construction. I modified the tri-canoe's beam to fit within the regulations from last year. From running the numbers that hull will weigh around 200 lbs; whereas, most of the round chined hulls will weigh between 125-140 lbs, and the multi-chines 140-155 lbs. If we were using a light weight construction material this would not be an issue considering its performance. However, this must be accounted for when considering the construction material will be around 54 lb/ft^3.

All things considered, I still would like to build a prototype based on your design, just to see how it handles. In past years there was no clear definition of a canoe's hull shape in the regulations. If this remains unchanged, I will very seriously consider this design when the new regulations are published. It is very innovative and would definitely draw some attention.

 

Petros,

I appreciate your input. Due to the regulations that govern the competition we were limited to a beam between 28 and 32 inches this past year. They generally set boundaries on the hull's length and beam. The regulations for this coming year will not be published until late September/October where I do expect some change.

I initially thought the round chine was the way to go considering its efficiency. However, I quickly noticed that because of our construction material, the round chine loses allot of its advantage due to the hull weight and load. A round chine hull should weight 125-140 lbs and the multi-chine 140-155 lbs. Even with its additional weight, the multi-chine seems to perform better when loaded.

For the competition there are three teams/load combinations:
Two guys, two girls, and then two guys with two girls.
They have to compete in a sprint (sprint out, 180 degree turn, sprint back) and the endurance ( a combination of sprints, small slaloms, and a 180 degree turn). Therefore, the canoe does need some maneuverability.

I'm going to work some more with Godzilla on the hull shape and I will report back to you what kind of results I obtain with the allotted conditions.

 

The only reason I made it hard chine is for ease of construction out of ply. A round chine version would have less drag. The main point is whether the rules allow such an innovative configuration. You still have to work out how to position paddlers and the best compromise on the outriggers for two and four man crews.

Rick W

 

Rick,

Here is an excerpt from the rules last year:

Section 2 – CANOE
CNCCC Intent – The intent of this section is to provide the specifications for the canoe. In general, teams are tasked to design and construct a canoe that (a) can withstand the rigors of competition including the transportation
to and from the conference and national events, (b) are constructed of materials that are in strict compliance with all of the rules and regulations, (c) has been built within the current academic year and constructed and finished solely by the students, and (d) certified as passing the flotation test to the satisfaction of the judges and/or CNCCC.

2.0 GENERAL

From herein, the term “canoe” shall be defined as any watercraft designed for paddlers using single-blade paddles. The same canoe shall be used at both the Conference and National Competitions and must be built with the
durability required to perform in both competitions and to be transported to and from the competition events. The canoe shall be built within the current academic year.

All canoes shall be constructed and finished by thestudents themselves. For all intents and purposes, construction relates to the actual placement of concrete, reinforcement, and flotation materials to the canoe; finishing relates to the sanding, staining, painting, and sealing ofthe canoe, as well as the application of letters to the canoe. The fabrication of the canoe mold and lettering may be created with assistance from outside sources/vendors.

All canoes are subject to an official weigh-in at the National Competition only (Appendix A-6). The weight of the canoe shall be compared to the weight reported on the Compliance Certificate.

2.1 DIMENSIONAL CONSTRAINTS

2.1.1 Length
The length of the canoe is restricted to a maximum of 20.0 feet. The length is defined as the end-to-end measurement of the canoe taking into account the outermost dimensions of the hull as measured at the gunwale.
(Figure 2.1)

2.1.2 Gunwale Beam
The maximum beam width of the canoe shall be between 28.0 and 32.0 inches. The location of the maximum beam width along the gunwale is at the discretion of the team. The measurement of the maximum beam width is
defined as the outermost dimension of the hull skin as measured within the top 1.0 inch of the gunwale (Figure 2.2).

2.1.3 Other Dimensions
The length (Section 2.1.1) and gunwale beam width (Section 2.1.2) are the only dimensions that are regulated for
the competition. The dimensions for other canoe parameters such as, but not limited to, depth, hull thickness, radii
of chines, and rocker, are not regulated and their values are at the sole discretion of the team.

From my interpetation from last year's regulations, the tri-canoe would be considered a canoe. I hope that will remain unchanged in this coming year's regulations.

 

Rick,

Would you expect a significant change in performance between the hard chined tri-canoe and a rounded chined version? It would certainly be easier to construction in it's hard chined form.

 

The difference would more relate to any extra weight but I believe the hard chine is essentially a stronger shape anyhow. I have not looked at the practicality of getting feet on the bottom of the hull but it needs to be wide enough at the bow to enable the front paddler to work comfortably.

Given the the beam is measured at the widest point you could simply make it more like an outrigger canoe. Place the outriggers fore or aft and not in the middle. Have a high bridging beam. Depends on how much you want to disguise what it actually is.

The most effective way to turn a two man canoe is for the aft paddler to use his paddle as a rudder locked in against the side of the boat. This provides stability in the turn because the forces roll the boat so it leans in. So canoes steer by pushing the stern about. Hence from a steering perspective you need to be able to easily push the stern sideways. It will turn faster if the bow has rocker but the essential is that the stern will go sideways.

I still think you need to compare straight and flat rocker over something like the planned course. Most of the wasted effort I see with untrained paddlers (including me) is the inability to track straight. For me this is the priority.

Rick W.

 

Rick,

Why doesn’t the Godzilla resistance values on the graph match the data in the "ship out" file? I have been using those resistance values on the Godzilla graph as a quick way to gage the optimized hull's efficiency. Today I produced what I thought was my most efficient hull yet after glancing at the Godzilla graph. I then imported the "ship out" file into Excel and quickly realized the data didn't match. What data should I be using?

 

You did not read Corey's thread from last year!!!!!!!!!!

I made an allowance for paddling efficiency of 65%. You should do yourself a favor and go through the thread and also look at Corey's web site if it is still operating. Will save you a lot of time. Copy all the useful bits for future reference.

You also need to know how the scoring is done. The racing is only part of the exercise. Like I recommended earlier you need to make an individual in the team responsible for each aspect. It is too easy to get carried away designing and building the boat. Good records and presentation count quite a lot I believe.

Rick

 

Rick,

I have read through that thread and calculated the loss of efficiency into my calculations. I wasn't referring to the graph you made for me, but one of my own. My issue was the difference between the resistance data from the Godzilla (shift R, t ) graph and the data in the ship out files. In the ship out files the total resistance values are different and it doesn’t seem to be a linear relationship.

For example, Hull1 was less efficient then Hull2 when comparing the total resistance values in Godzilla. However, after importing the ship out files into Excel the resistance values in the ship out file indicate Hull1 is better. Have you noticed this disparity before or am I doing something wrong?

 

I have never taken much notice of the Michlet resistance graph. I look at it to see if the various curves make sense. My data comparisons are always based on the ship_output file.

Just be aware that the scale in the Michlet graph window changes automatically - are you comparing apples with apples.

Rick W.

 

Rick,

Yes, you are correct about the scoring. I was part of our Canoe team last year and went to the regional conference. The scoring is based on four facets.

1) Design Paper (25 pts) - this includes a detail specific design report including the concrete mix design, hull design, project management/scheduling, etc...

2) Final Product/Display (25 pts) - this includes the physical display of the canoe, aesthetics, table top display of materials, construction techniques, etc...

3) Oral Presentation (25 pts) - 5 minute timed presentation before the judges, ability to answer any questions after the presentation

4) Canoe Race (25 pts) - mens/womens/coed sprints and endurance, five events total

Last year (my junior year) I was a laborer, so to speak, on the project. Our canoe didn't do to well in the competition because it cracked during transportation on the way to the event. This year I was elected to be the project manager and I have been working diligently on it since. I have four other students that are committed to the project that have different interests in the project.

We have traditional tripping canoes on campus that students can use on the campus lakes. From my experience, the handling of tripping canoes is very different from that which we are trying to build here. The practice canoes we have had in past years have generally left with the outgoing class.

My main objective currently is to learn and design an good canoe based on last year’s regulations. It will then be built and used for a practice canoe. In doing that I hope to become familiar and confident in design and using the software. Then when the new regulations are released I will be able to make the needed adjustments and produce a good design in a timely manner. This fall will I have 18 credit hours of tough courses and this project to contend with.

In essence most of the project cannot be done until the regulations are released. So, I’m trying to get as much preliminary design work done now to prevent myself from being over loaded this fall. From my experience the design work takes the most patience and time.

 

Rick,

The velocity scale remains unchanged at up to 6 m/s as set in the input file. The y-axis , Total Resistance (KN), changes with the curves and hull design. I assumed the resistance values in the Godzilla graph were accurate, but they don’t correlate with the ship out file. That really through me off because I was using those resistance values as a quick gage for the efficiency and it now appears to have no validity.

 

Leo Lazauskas developed Michlet and its optimising routine Godzilla. He currently has a thread going comparing CFD with Michlet and he also looks into other threads that might be of interest.

If you do a couple of screen dumps to show the issue and post them he might comment on it. If it needs correction he might place it on his to do list.

He has made Michlet freeware and it is an outstanding piece of work based on some very clever thin hull mathematics developed a century or so ago.

On another note, if you have overall responsibility for the project then I suggest you find a team member to take responsibility of each of the four scoring elements. As PM you should be working on organisation, planning, team culture and anything that falls through the cracks. You could have a secondary reporting role as design manager but it would be better to stick with the PM role or look to someone else to fill the PM role if you want to put effort into the design.

Even if you build a boat that blitzes the field you are only 1/4 of the way there. You are entering an engineering learning exercise and the quality of the project management will have a large bearing on the results - like all projects. The hull shape is not going to make a huge difference.

How much effort have you already put into planning the presentation. What training exercises are there for the presentation. Who is the public speaker and public relations guru in the team. Presentation is worth the same points as the boat races. It deserves at least equal attention - possibly more if you do not have a good presenter. Have you thought about recruiting someone from media studies to help on this aspect?

I hope this is helpful and not viewed as being negative.

By the way what group are you in? Is it the same as UT?

Rick W

 

Rick,

After looking over more Godzilla graphs and their respective ship out files, the numbers do correlate; they are just slightly skewed in some cases. The resistance values don't directly correspond to the velocity values on the graph. Where a resistance of .0678 KN at what would be assumed to be 2.25m/s looking at the Godzilla graph is reported in the ship out files as the resistance at 2.4 m/s, or something like that. When the resistance is skewed it seems to be a linear tread throughout the ship out data. Therefore, I believe the Godzilla graph to still be a good reference.