Originally Posted by Equalitude
Thank you guys for your help. Both posts have definitely been very helpful.
I have a more specific question as well. Do you think it's a crazy idea to modify the bicycle wheel itself by adding some paddles to it so that all you have to do is dip the wheel in water and have it propel the boat? I like that patent image but it seems like there are two sets of gear systems and drive chains which almost defeats the convenience of just using a bicycle.
Finally, are there some retail stores that can sell you parts to accomplish this task? I don't have any welding experience nor do I have access to a machine shop.
The key items for a really nice boat drive are a right angle gearbox and a propeller. It is a challenge to make a good system without shop facilities but not impossible.
The best right angle drives I know of are Mitrpak: http://www.mitrpak.com/product_datas...?product_id=31
The one shown is OK for moderate power input. If you really want to sprint hard then go up to the 1/2".
I have suggested the 2:1 so you can use a model plane prop. You can get these from here: http://www.hobbycity.com/hobbycity/s...site_propeller
This prop would be run around 8x cadence. So 4:1 from crank and 2:1 in the rightangle drive.
There is one readily available boat prop that is OK. It is not too bad but needs to be run about 5X cadence and will only suit an easily driven hull. It is a 15 X25 Bolly boat prop about half way down the linked list: http://www.bolly.com.au/models/glasstwo.html
You can get a prop collet from Hobby City as well: http://www.hobbycity.com/hobbycity/s..._shaft_(collet
For the frame you butcher an old bike. Just cut out the bottom bracket with about 14" of frame tube on either side. This is inverted and mounted onto the boat. It is easy to weld or braze mounting plates but if you do not have the facility then get some epoxy resin and fibreglass tape. The frame and seat shown in the attached photo does not have any welding in it. It is all made from carbon fibre cloth, Klegecell foam sheet and Epoxy Resin. It weighs under 5 kilograms including the crank and gearbox.
You can also buy metal brackets that can be riveted or screwed to the frame and then glassed over. You would need a hand drill for this.
I buy resin and cloth from here: http://www.solidsolutions.com.au/ http://fgi.findnearest.com.au/findne...sult.asp&log=1
I am sure you can find places near you with the same materials.
The set up shown on the attached photo is about the best you can get. The offset thrust from the side mounted prop requires negligible effort to correct with small rudder angle. It avoids holes through the hull and the prop can be reached for cleaning off weed. I usually detach the shaft for transport. It is held in place with two thumb screws.
Finding a source of aluminium sections for bits and pieces is handy. I have 5 locations within 20 minutes drive of my home. You can use machinable aluminium rod for the curved prop shaft similar to what I have shown. Aluminium and glass/epoxy work well together. A glass/epoxy wrapped joint is likely to be stronger than a weld if done properly.
I use this supplier for other bits and pieces: http://www.smallparts.com.au/catalogue/
There are smallparts locations in the US as well that supply quickly.
Sitting up on a bike is not the best position for a boat. Your centre of gravity is high and you are more likely to roll it. A recumbent position is best for boating.
Fitting paddles to a bike wheel is not all that easy. To be effective they need to be about 4ft wide so dinky little ones a few inches across that can run through the frame will do nothing.