MODEL JET BOAT PROJECT

 





The goal of this project is to design and build an R/C model jet sprint style boat to play around the pond at work. Although the pond is probably too small, it is a good visual motivation as I walk past it to get to work every day. The model boat will be powered by a Zenoah two stroke gas engine. The hull will be constructed out of wood and fibre glass. The design of the hull and jet intake were done using 3D CAD pakage call Pro Engineer. The stator and impeller were machined on a 4th axis cnc milling machine.

Pond at work Example of a jetsprint boat

 

Hull Design:

The hull was designed from looking at pictures of jetsprint boats and modelled on 3D CAD package (Pro-Engineer) The dimensions are 1000mm in length x 390mm in width. The deadrise is 23 degrees.

Top veiw of Computer model Underneath veiw of Computer model

 

Hull Construction:

Rough plans were printed off from the 3D model. Hulls sections were cut out from the cross section plans and a top elevation was used for construction.

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Motor:

The power house for this boat is a 23cc water cooled Zenaoh. (Thanks Matthew Waldron) Which should be capable of producing 3-4hp with the right tuned pipe and a few engine mods. The engine is water cooled and gets its water supply from the jet pump. Its a two stroke engine and uses normal gasoline and two stroke oil.

Intake side Exust side

 

Jet intake Construction :

The Jet intake was modelled on Pro-E. It was then machined out of two pieces of billet Aluminium using a CNC milling machine.

CNC Milling machine 1st side being drilled and tapped 2nd side being machined 2nd side ready for surface cutting

 

Jet intake polished:

The Jet intake was sanded up to 1000grit and polished with a metal polish and a buffing wheel.

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Nozzel:

I turned up a nozzel on the lathe

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Impeller design:

Used Pro E to design the impeller and stator.

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Assembly:

Bits placed in the boat to see how they look and fit :o)

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Impeller:

I used a 4th axis milling machine to make up the impeller.

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Stator:

I used the 4th axis milling machine to make up the stator as well

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Bath testing:

I attatched an electric drill to the shaft of the jet drive and tried it out in the bath tub. I did use a safty transformer (sometimes) ;o)

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Hull progress:

2nd may 2002

I made some more progress on my hull. The hull has been fiber-glassed and few more trimmings have been added to the hull construction. The bow decking should go on soon.

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Construction Completion:

3rd June 2002

Finished all the sanding and expoxy coating. Just needs some paint. Stuck the boat in the bath to make sure it floated level.

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Jet Pump Test Box:

3rd September 2002

It has been a long time since I've had anything to add but I've got my motor going. I made up a test box to put the pump in and tried it all out in the pond. The result is that I need to redesign the stator as it is fanning out the water too much

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Jet Pump Test Box with honeycomb:

29th August 2002

The motor wasnt producing much power above 1/4 throttle so I've opened up the motor exhaust outlet and put a honeycomb over the nozzel to act as a flow straightener. The honeycomb made a big diffence but is not practical to use. The extra exhust area also helped and now the throttle is responsive over the full range.

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2nd Generation parts:

28th October 2002

I've redesigned the stator, impeller and nozzel to see if I can reduced the swirl without needing a honeycomb. Will do tests soon

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Here are the test pics. I think the swirl is a lot less. The flow maybe just a tad more.

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WOW BIG UPDATE COMING:

24th may 2003

I cant belive it's been so long since I've updated this site. Part of the reason was that for a while I didn't have much to add but lately its been because I've been too busy making bits and pieces.

Paint Job:

I used some pretty crappy paint out of a spray can. But it was was the only way I could get fluro green!

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2nd Generation Pumps:

One of the reasons for taking so long was that I decided to make two extra pumps for some friends of mine. In return I got an extra motor. (Full mod G260) which should output 6hp at 15,900rpm!!DYNO RESULTS

If the strong motor turns out to be over kill, I can always put the stock motor back in. But I doubt it Matthew ;o)

1:These show the difference between bead blasted and a polised pump.

2:The mass producing all the internals. (this took months!!)

3:Nice and shiney again

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4:One bad impeller after the CNC went bad

5:All parts anodised. A pitty the shine was lost :o(

6:Completed pumps. (Time for a big rest)

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G260 Zenoah engine testing:

I tested out the engine, pump and hull in the water without radio gear to make sure everything was ok. I discovered that there were a few things that needed changing. The grubs holding the impeller and shaft on needed locktight becasue they came loose from the vibrations. The stator bush was binding on the shaft because the nozzle wasn't able to bolt pendicular to the transom. I fixed lots of thing and made a new bush out of brass. the old one was plastic and melted when not water cooled!

1:Mounted engine onto engine rails and testing fuel position (IV bags).

2:View of the pond at work. Starting to get dark (winters coming)

3:Got a little shock off the engine (Don't touch the black wire!)

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4:Pumping some water. Engine a bit smokey.

5:A bit more gas. Need to two people to hold onto it

6:Sent the boat off by itself at idle. (But had a some string to stop it getting away)

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I manage to measure 45km/hr on the GPS. Unfortunately I hit the shark cage and put a nasty little hole in the side.

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Some extra pump modifications:

I fixed up the hole and made a few new impellers to see if I could gain more speed. I made a new design with 55mm, 50mm and 45mm pitched impellers. The 55 went a bit faster than the 50mm but alot faster than the 45mm pitch so I'm guessing that a 53mm would be optimal. I tried reducing the nozzle diameter to make the boat go faster but it just made it very hard to steer the boat.

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I also anodised my own pump in gold

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New Movie 30th October 2004:

Here is a new movie of the boat going for a spin. It actually gets airborne at one stage. It might not be saved here for long so save it if you want to keep a copy. Its 3.17Mb is size.

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LINKS:

Jim's Graphics section

 

 

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