Help with YMCA boatrace

[Scott Baker]

Gentlemen I am a member of YMCA guides and princesses. I have been elected to build our tribe a homemade boat that we will race against 20 other tribes. Distance will be about one football field with one turn. I would like to put as many tribe members on the boat as possible ( 7 dads 7 girls 7 to 8 years old ) . Rules are it must me human powered and they supply the paddles ( no oarlocks ) however I have checked and a bicycle powered paddle wheel would qualify. LOSEING IS NOT A OPTION. I have been reading on this site about 55 gallon drums, inner tubes , pvc pipe and other materials. Questions are monohull with outriggers or catamaran? What type of boat to build and out of what? I would like to make a (sleeper) looks like it would hardly float but would be fast as could be built. I used to own a auto collision repair shop so I am comfortable with welding woodworking fiberglass ect. Budget would be from $ 200.00 to $ 1000.00 with less being the best as this is a one time use. I am very impressed with the post on this site and any help would be greatly appreciated. Scott Baker

[marshmat]

Hi Scott, welcome aboard!
The trick to making a human-powered boat fast, be it a rowboat, canoe, kayak or pedal powered thing, is to make it as long as you can. 7 dads and 7 kids are not going to be able to make the boat plane no matter what, so you're restricted to displacement speeds- the maximum speed you could hope for is the theoretical hull speed, typically around 1.3 times the square root of the waterline length (in knots and feet, respectively).
The other thing that helps with speed on a low-power boat like this is to make it thin and smooth. An Olympic rowing shell is the logical limit of long, thin and smooth. But that gets tippy, real tippy. Which is probably why you're thinking of outriggers or a cat, even if you don't say so outright.
I wouldn't be looking at oil drums or tire tubes, if I were you.... rather I'd head to Home Depot and look for some cheap exterior plywood. (Yes, mariners, I know this stuff is not meant for boats.... but Scott said it's a one-shot deal and the extra durability of marine ply is not going to make a shred of difference in two hours on the water.) Flat bottom, vertical sides, to keep things cheap and easy. Pointy at both ends. Looks like a canoe from the top. As long as you can with the wood you can afford. Wood frames every few feet to hold the shape.
If you're worried about tipping, plastic drums could be used as outriggers, but mount them so that they're clear of the water when the boat is loaded and level. If the crew can keep it level, then you don't have to worry about the extra drag of the outriggers.
Lifejackets must be mandatory for all crew.
Have fun!

[Scott Baker]

Thanks for your input. Is there any math that helps determine the most efficient dimensions length, width, and weigh in the boat. Also do you have any thoughts on paddles vs paddle wheel vs propellers. I was reading the post on HPB and got some good ideas for a bicycle driven paddle wheel or prop. There is a certain amount of psychological factor to having a apparatus bolted on board.Thanks

[marshmat]

Length- As long as possible.
Width- As thin as possible.
Weight- As light as possible.
If you want to go all gung-ho on math, you could read up on the relationships between speed and prismatic coefficient, etc, etc... the literature goes on forever. But for what you're planning- if it looks sleek it probably is. If you want to try some goofing around with a computer, search for "michlet" on this site... great resistance prediction program, if a bit hard to learn. Remember that it's only what's below the waterline that counts.
I don't think you'll be able to go far with propellers etc. on that budget... but feel free to goof around with paddle wheels, if you really want to.... can't hurt to experiment.

[Scott Baker]

I have free access to fan blades off of automobiles and large 18 wheel trucks. If it makes sense I would use a 1 to 1 ratio for a auto fan and a 1 to 3 for a 18 wheel fan. Also I would rig it with a 10 speed bike ( that I already have ) so I could use the gears to fine tune the prop speed. With wood being the building material does anyone know what is the lightest 1/4 plywood there is. I would build it with stitch and glue and wrap it one time with a light coat of epoxy and cloth to keep it from soaking up water, unless someone knows a lighter way to stop water absorption .Any thoughts would be great.

[nordvindcrew]

I'd look at dragon boat designs. They're used for exactly the sort of thing you are going to do. There has to be something if you google it. One concern on the long and narrow factor is that you must do a 180 degree turn. Too long a boat or too little rocker in the bottom will make something that needs a football field to turn. One last piece of advice: can the "losing isn't an option" compete hard, but first of all have fun. I compete in about 7 open water rowing races every year; win some finish 2nd or 3thd sometimes. No one competes any harder than I do, but still I do it for the fun. Good luck!

[Scott Baker]

Thanks for your reply. I am with you on losing is not a option. The rules state that you should try to include as many tribe members as possible, what a lot of tribes do is put there two lightest strongest men in a boat and race. Whether we win or not I want to put as many of our kids and dads in the boat as possible ( min 4 dads 4 girls ) so we have a disadvantage to begin with. That makes the boat design that much more important. As you have done this before do you feel that a long 20 to 24 foot canoe could be turned by 2 people paddling backwards on one side and the other side paddling forward ? We do have to make one 180 degree turn. I am going to Google dragon boats and see what I can find. Thanks

[Scott Baker]

I need help ! Were can I find building plans for a 6 person ( about 24 feet canoe ) something that can be paddled and as thin as possible ? Thanks

[gonzo]

Fan blades are useless in water. They will be very inefficient. The beam should be about 26" since they are mostly inexperienced crew and about 30" per person. It can be built of 1/4" plywood with a 1X2 chine and rubrail. The sides should be about 14-16". Keep the sides parallel for maybe 70% of the total lenght. Taper both ends.

[Scott Baker]

Thanks for some great info. I was wondering about adding all the weight and complexity of fan blade drive , you saved a lot of wasted time and effort. I found plans at Chesapeake Light Craft ( peace canoe ) and asked about stretching the design they said it could be done and also agreed with you that I need more than 24 feet. Thanks again for some very help full info. Scott
PS do you have any thoughts on paddle wheels. I was thinking on using the 2 aluminum rims on each side of the boat with large soup or coffee cans attached to the rims. Also I would make it were they could be retracted up out of the water in case of a all out dash were paddles alone would be faster.

[gonzo]

Coffee cans will create a huge amount of drag entering and exiting the water. Flat panels are best. When you start complicating a system, adding weight and parts, it is more likely to fail. If you are really serious that failure is not a option, it is time to start training as a team. Most of these races have teams on a variety of craft, that may or may not float, completely disorganized and uncoordinated. It is unrealistic to thing you are going to build a boat and show up the day of the race and compete.

[marshmat]

Agreed... the boat is best kept simple, and the time saved by not building gadgets goes into getting the team working as a team.
Canoes can easily reach hull speed with paddles, no bike gear involved. Where that stuff has the advantage is when one person is trying to go hundreds of miles on their own power.
I'd go for a light, simple boat- see post 9, I think G. has it right- and get the whole team involved in the building, it'll be a lot of fun! No need for nasty compound curvature or anything complex, just plywood and 1x2s. Then get out on the water and get some practice with it while the opposition is still scrounging up oildrums.

[marshmat]

Here's an idea for you, Scott. Not ready to go as-is but you could start with this and adapt it.
You will need the free, easy to use Free!Ship program, http://www.freeship.org/ to read the file. It runs on any Windows machine and will run under emulation on other systems. You edit the drawing by moving the control points attached to the hull.
What I've put here is a 25-foot boat along the lines of this discussion, all flat panels, all cut from quarter-inch exterior ply, three or four sheets of it. It should take around 23 pounds of paddling force to go seven knots with 400-500 pounds aboard. If you want to make it perfectly flat bottomed (no rocker) it will be easier to build but harder to steer. If you were to shrink it to 23'6" or so it would work out nicely with the 4x8 sheets of ply. Freeship will give you the actual shapes to cut out of the plywood as well. This thing only took eight minutes to draw, it's an easy and handy program and can also give you some idea how it will float.

[Scott Baker]

Thinking about the shape off the hull is why I am looking at buying plans. Would a flat bottom or homemade bottom be faster than a commerical plan hull. Thanks for all the input. I think I take this more serious than some off the other team members and do not know how much training I can get out of them. And is the reason I need to build the best ( or most fool proof ) boat possible.Thanks again for everyones thoughs as they help a lot. Scott

[SamSam]

I would think this is the kind of race where whichever team had the most fun would be the winner. If the boat is for one use only, paint is all you need to water proof it, duct tape will hold it together and patch any holes or leaks that might be made in minamal practice sessions. A series of small boats of 1 or 2 people capacity hooked together like a train might work.
I was in a canoe race once that had a bunch of bouys people had to go around (circle). The winners didn't steer around in a circle, but would go past the bouy on one side, back up past it on the other side and again pass it going forward on the first side on their way to the next bouy, thereby circling the bouy but without turning the whole canoe around in a circle. That probably won't help you in your one bouy race, but it might. Sam

http://images.google.com/imgres?imgu...lr%3D%26sa%3DN