Floating Motorcycle

[Davicus]

Hello all,

I've got a strange one here. I am working on a TV show, and I need to build a vehicle that functions as a motorcycle on the street, but a jet ski in the water. The good news is I own a motorcycle shop, so I'm pretty handy, and have a good amount of resources. The bad news is, I have no idea about boats, jet skis, etc.

I have a budget of about 4k, so I will probably start with a 1970's Honda, build pontoons, etc. I would love any suggestions, ideas, etc.

Best,

Dave

[masalai]

Make 2 so that one is the "motorbike" part and the other is the "jetski part" and as one gets wet, cut/take changing "vehicles" on the spot... Externally they both look identical when on the water so the "jetsky" boes not need wheels and the motorbike does not need a "working" waterjet... Both need a fairly "deep-V" deadrise so the bike can still operate as a bike... - Buy 2 identical busted engine jetskis to get the free cowling to form the externals and "cheat the eyes", as is done in all movies....

[tinhorn]

Easy:

[Frosty]

You might have more luck converting a snowmobile which will almost do both as it is.

4k is a bit thin? you need another zero on that.

[jtd]

Well I think I can safely say there's no such thing, but to aid in your ideas you can go to youtube and see clips of travis pastrana (hydroplaning) a dirt bike.
it is quite impressive, he goes a couple hundred feet or more, but the end result is, it sinks like a rock. I hope this helps & good luck with your prodject.

[masalai]

Hey, how about a link for those of us not so Utube literate:D:D:D

[jtd]

Hey, how about a link for those of us not so Utube literate:D:D:D

here's one its not the one I was thinking of, but it will show what I mean.
http://www.youtube.com/watch?v=AnyTjURH-_I&feature=related

[Davicus]

Thanks for the input fellas. I can't do two bikes, as the whole point of the episode is the challenge of making a dual purpose vehicle.

I am going to use a two stroke 250 cc enduro motor. the front end will be totally stripped of all controls and suspension, with a skinny front tire and a solid rim. off the front fork sliders will be an angular pontoon that will stick out about a foot from each side of the wheel. hopefullly this will work as steering when i get in the water. the bike itself will have an aluminum catamaran style fairing under it, with the rear wheel sticking out teh back. i will run some sort of pto off the engine to power dual water pumps.

my question is, if i weigh 250 lbs, and the bike weighs 400 lbs, how big do my pontoons need to be to keep the whole thing afloat???

[masalai]

big enough to hold 65 gallons of air for the specified weight plus some to keep you above "neutral bouyancy" roughly.... (10 pounds to a gallon of water?) Somewhere my brain remembers that 10 pounds is the weight of a gallon of water? last used "imperial" around 1963 sometimes the stuff sticks sometimes the memory gets its filing system stuffed - = metric is easier litres & Kg are linked in volume & weight of pure water...

[Davicus]

so is that the conversion? 1 gallon of air per pound?

[jtd]

as for your flotation insted of aluminum pontoons I would lean more tword's doing a solid foam core fairing covered with the fiberglass cloth used for surfboards, with epoxy. I cant remember the weight of the cloth. it would be alot easier to form the foam to the shape you want and need as well as keeping the weight and cost down. as for propelling this thing through the water why not go with a paddle tire for sand racing? you already have that rotating mass, & need to keep weight to a minimum. the front tire is probability going to cause so much drag being skinny & parochially submerged you may want to utilize this as a planning surface (wide tire).
now keep in mind I'm just trowing thing out for you to think about I am not a expert, I just like thinking outside the box.
good luck.