Propulsion options

[AAAkings]

I am new to the forum and have been reading multiple posts looking for answers for the last few days.

A bit of background info on this post is I am in my final year of Manufacturing Engineering Technology course which requires a substantial project. I have access to CNC Lathes/Milling machines, welders, and tools for composite work (Autoclave).

What I am looking at building is a powered surfboard/kayak like similar to the Jetsurf and similar projects. I will be designing the "boat" and hope to model it on a CAD system (Catia). I was leaning toward the surfboard style for cost purposes (Other recommendations welcome).

Now the main question I have is what your recommendations would be to propel this? All the marketed ones operate via a Jet Drive system. I am having a hard time finding parts small enough to get this to work and am wondering if it is worth using a propeller propulsion system instead? (Use a prop guard for safety). Also after looking through the forums, (The 10HP jet driven boat idea in particular) it doesn't seem like there is a viable option via a jet drive system.

Thanks for reading it through and thanks for any input!

[mohawk]

I sugest spending alittle more and doing something like this. A surfboard would be gutless, and a whole lot of work for very little use.
A similar boat to this gave 59km/ph with the running gear from a 550 stand up ski.
http://www.youtube.com/watch?v=3yzwp...BCBAB5C1FC9554

[AAAkings]

I was looking at making one of these, but for myself at the moment I would need to buy/build a trailer and get a vehicle I feel comfortable towing it with. I was hoping for something I could strap in the trunk/on the roof of a small vehicle.
Also, in terms of building it would be a lot cheaper and easier for myself to make it as a surfboard as I have little welding skill (besides arc, but still did not pass the test to get a ticket). I figure if I designed a surf board via a CAD program I would be able to rout out a foam blank and simply wrap it thus focusing more on the engine part of things. I have very little knowledge regarding boats so if it is not a do-able option I guess I could go back to the drawing board and attempt something different

[Submarine Tom]

AAAkings,

Completely doable, lets see some plans / drawings.

-Tom

[mohawk]

Like this ? http://www.trademe.co.nz/motors/boat...-406896743.htm

[AAAkings]

Mohawk hit it dead on. I hope to be able to make it a bit cheaper considering all that is required is all the parts, all the labor will be done by myself as well as help from an instructor.

Submarine Tom, I don't have any plans of the actual design of the surfboard yet as I thought it would be best to design it around the engine used. I was thinking that if I could not find proper parts required to make it a jet propulsion, it might be better to use sort of a surface prop? (Wrong forum I know but I was Gung-Ho about using the jet system for safety purposes.

Edit: I am wondering what engines I would be able to use in this situation. I am under the impression I will need to make the compartment waterproof, but then the question is what do I do about cooling/airflow. I am a total Noob at this and pardon my ignorance please.

[mohawk]

Water cool pocket bike motor mabey ? Pressureised water from the jet unit is used for cooling. Look for a chinese copy of a B1 (blata ) pocket bike engine if you decide too go that way, their strong and make good power for their size.
http://www.alibaba.com/product-gs/20...ed_Engine.html

[AAAkings]

I took a look at it and it definatley looks like a solid option. I am wondering if a 49cc engine will provide the power I am required? Any formula's I would be able to see without a hull design already chosen?

Another question is should I look at an electric motor? If so what kinda of specs should I be looking at?

BTW, thank you very much mohawk, you have been a great help!

[mohawk]

I doubt electric would have the power you want, and the batterys would weigh too much and not last long ?
I race pocket bikes, we get speeds upto 70-90 kmph with full size 70kg+ riders so there must be some potential there. Torque would be the big issue Id imagine. You would need a very small diametre unit to cope with the rpm or mabey a large model boat jet unit ? or sleve down a small jetski unit.

[AAAkings]

I noticed after the fact how fast those engines moved people! Even if I used a 110cc one it should ensure offer more torque right? modifying a jet ski shouldn't be to much of an issue if someone can explain how and why it needs to be done. I looked into Rc jets but they seem to small? Only a 40mm impeller vs a jetski 140Mm or bigger if I read correctly


Edit: I am now more leaning towards building a kayak instead now due to ease of finding engines that will fit into the hull. Prop an option now or stick with water jet-drive system?

[mohawk]

Stand up 550 ski gear shoud fit in a kayak, but then a small glass dingy would be more fun and cheaper ?

[AAAkings]

Thanks for the info on the ski gear! I will start looking at prices and try to snag one in the next few weeks.

I was thinking at first to build a small, (one or two seater) miniature speed racer boat but I don't have a truck or an SUV to tow it. I plan on making a white-water style kayak as it should still be nimble in the water and basically able to turn simply by leaning. I understand its not the most efficient design for speed, but I figure if I through horsepower at it it should be able to get up to my goal of 35/40 km/h if thats not too fast.

[RivrLivn]

More on the kayak design powered by a water jet is this: http://www.mokai.com/index.html

Not as cool or fast as the surf board, but would still be a fun build.

[AAAkings]

I saw that and actually emailed them asking them to purchase the jet-drive system and possibly the engine as well. They said that they cannot sell it separately but wished me luck with my endeavor. (I emailed the surfboard companies too and same sort of response).

Right now I figure with a kayak, a jet ski propulsion unit it shouldn't be to hard to manipulate (I'm sure I won';t say this when I get to this part however).

Right now I am in the planning stages and am looking at using a White Water style kayak for this build due to its nimbleness and sleek design. And once again just to verify, a 10HP engine should be able to power this kayak at 35-40 km/h fairly reasonably right? (Even looking at the 50cc Balta engine)

[RivrLivn]

The trick to get that kind of speed out of 10hp is to perfectly match your pump.
There are not many jet pumps built for that low of horse power.

Here are some of the smaller ones I have seen: http://2si.com/