750cc jet ski drive. - RC Groups
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Nov 05, 2017, 09:59 AM
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750cc jet ski drive.

I recently got offered a jet ski for practically nothing. Ive had an idea in my head for years about building a hull to fit a jet ski power system. I have a few questions about this though, as Im not too experienced in RC boats, or hull design. Im not looking for anything super high performance, or perfect handling, just something I can play around with.

Im thinking of a fairly shallow v hull to start with, somewhere in the 12-18 degree deadrise range. What are some good starting points for length to width ratios? I don't have the drive unit yet, so I don't have and specs as far as dimensions, or weight, but but Im thinking this hull will have to be somewhere in the 8'-10' range in length, and 2'-3' in width. Sound close?

Also if anyone can share some hull design links, or steer me in the right direction to find dimensioned drawings, it would be greatly appreciated.

Thank you.
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Nov 05, 2017, 10:36 AM
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dunk911's Avatar
This might be about right.


I'm building one up at present for 700mm length. It was originally designed as 1000mm so about half the size you mention but it would be easy to scale it up and all the cut list is done so you could get it laser cut for ease of your assembly.

Check out the videos on the thread to see if a scaled up version is the kind of thing you want :-)
Nov 05, 2017, 12:54 PM
Just Plane Nutts
AirDOGGe's Avatar
Could the hull just be the same length as a ski jet? With no rider on board, it should haul butt.
Nov 05, 2017, 01:31 PM
Registered User
Dunk, that looks pretty close to what I have in mind. Maybe slightly narrower, and (possibly?) longer hull, to handle some rougher water.
Do you have a thread going on your build?
Nov 05, 2017, 02:17 PM
Just Plane Nutts
AirDOGGe's Avatar
A "Cocktail Class" 8-foot racer hull might be just right for that drive: http://www.boatracingfacts.com/forum...l-Class-Racing

Here's a plans source. They also sell kits with just the wood parts, since you won't need a seat, steering wheel, etc....: http://www.clcboats.com/shop/boats/b...ass-racer.html
Nov 05, 2017, 03:26 PM
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Thank you airdogge. I will check those out.
Nov 05, 2017, 04:40 PM
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dunk911's Avatar
Originally Posted by Chuck200
Dunk, that looks pretty close to what I have in mind. Maybe slightly narrower, and (possibly?) longer hull, to handle some rougher water.
Do you have a thread going on your build?

No I'm not doing a build thread. It possibly wouldn't be that helpful as I've had to change quite a bit of it to suit my drive. Its not that easy to change things around unless you've done stuff like this before (you change one piece and other bits have to change too) but if you get the standard parts cut out and understand how to change things around to suit your pump I'm sure you could do it.

I can send you some pictures of what I've created so far if you're interested :-)
Nov 05, 2017, 08:04 PM
Registered User
That would be great! Im sure ill need all the help, and advice I can get if Im gonna make this project happen.
Nov 06, 2017, 12:28 PM
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Kayaker's Avatar
For the proportion of length to width on the Bermylizard jet sprint at one meter, Snikwah (Peter), a very fine jet boat builder, says he likes a narrower transom at 390mm instead of Bermylizard's 430mm.

Bermylizard's boat has a deadrise of 23 degrees. This would keep it from sliding around on flat water. I boat only in rapids and use a ride plate with up-side-down fins so I like a little flatter bottom at 18 degrees. This gives better directional control in very turbulent water.

Like Dunk said, “you change one piece and other bits have to change too”.
Nov 06, 2017, 03:34 PM
Registered User
Ill be running mostly on lakes, and larger rivers. A design that handles rougher water would be ideal, since Im not worried about the draft of the hull I was hoping to go with a narrower, and longer hull, with a fairly high dead rise.
I know that jet drives have some limitations with hull design, but if I could flatten out the bottom of the hull enough to keep the jet drive happy, Id love to build it in the offshore boat style, such as an apache style hull. Modified as necessary to keep the drive happy. Those seem to have a length to beam ratio of 3-4:1, would a hull like that be feasible for a jet drive?
Thanks everyone for all the help and advice so far!
Nov 06, 2017, 04:19 PM
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dunk911's Avatar
Here's some of the photos of that plan but they are just the ones I have on my phone :-)

Can do more on request just shout :-)

I would say if you got it laser cut in ply and don't change anything, it would go together really nicely.
Nov 07, 2017, 05:30 PM
Registered User
That's a nice looking hull Dunk . Do you have plans drawn up for that? It would be interesting to see what it looks like scaled up to the size Id need.
Nov 08, 2017, 04:47 PM
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dunk911's Avatar
Its the plan I sent you the link to previously :-)

See post 2!

Any Q's just fire away :-)
Nov 08, 2017, 10:16 PM
Registered User
Lol. Sorry didn't even realize they were both from you! Ive been going a little crazy thinking about this project.

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