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3D printed Jetsprint jet boat V1
Link for version 2 is in descriptionMaker/DIY
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Commercial use is not allowed, you must attribute the creator, you may remix this work and the remixed work should be made available under this license.
Forum thread: https://www.rcgroups.com/forums/showthread.php?3061106
A personal project I've been working on. Posting here since there aren't many 3D printed jetboat designs out there.
lijingwei made one too. He's also made some improvements. You can find these here: https://www.thingiverse.com/thing:2890756/remixes
My boat's maiden outing:
- Impeller: 29mm with 29mm pitch (18-29mm pitch files included)
- Nozzle: 22mm
- Hull length: 430mm
- Hull width: ~165mm
- 9g servo for steering
- mounting points for optional reverse bucket and servo
- Assembled mass: 1308kg
- 3674 brushless inrunner motor @1900KV. 61A max. Max power 1800w.
- 2x 2200mAh batteries, 25C.
- 120A watercooled ESC
Credit for the included axial jet drive calculation spreadsheet, goes to RCgroups member UnusualRC. UPDATE: I've been notified there is a mistake in one of the formulas on the sheet. Please be aware of that.
- Get video of it at top speed with CoG moved foward running at 6S then retest
- Test boat with 6S configuration. boat is way overpowered which is great fun. SO fast. Gets a lot of air.
Make next version with bigger hull - calculations were incorrect and hull sat far deeper in the water than calculations indicated
Improve lid to be more water tight on next version.
Other side notes:
batteries, esc and motor all stayed stone cold in 3S mode running at full speed. Motor is wayyy oversized for this boat.
It nowhere near uses the full power available to it running at 3S.
Materials and methods
I printed my hull at 0.3mm layers with 3 perimeters and 25% infill with support structures enabled. The hull is best printed in PETG or ABS for durability. I've printed my impeller in PLA because of how it is easier to get a very clean print when using support material. I find it prints best at 0.15mm so highly recommend that.
The impeller is intended to be glued onto your 3mm drive shaft. Its recommended that you sand the shaft lightly before gluing to ensure a good bond.
The nozzle takes a 3mm inner, 4mm outer diameter teflon tube as a bushing for the shaft (check the last two pictures above). I cut 5mm off my bowden tube and used this. Teflon is a very durable and low friction material - perfect for use here.
Bill of Materials:
- ~430g of filament
- M3 misc screws
- self tapping screws
- 1x 100mm long, 3mm stainless steel rod as driveshaft.
- 1x 623RS bearing (623ZZ is also fine but rubber seal is of course better when water is involved)
- 1x 750mm of servo pushrod wire
- 1x flexible coupler to go from motor to the driveshaft. I used 3 to 5mm adapter. Most 36mm diameter motors use 5mm shafts. I would recommend a universal joint which can be found for $1-2 on aliexpress. You could print your own universal joint or direct coupler (both are printable and included in files).
- 2x 9g servos (1x if you don't opt for the reversing bucket)
- 1x Motor + ESC
I'll be using this motor: https://hobbyking.com/en_us/turnigy-xk3674-1900kv-brushless-inrunner.html
And this ESC: https://hobbyking.com/en_us/hobbyking-120a-boat-esc-4a-ubec.html
You'll want to pick a motor/battery combo that delivers up to 20,000 rpm and can handle about ~75A continuous. Refer to: https://www.kehrer-modellbau.de/en/kmb-jet28/jet-drives/kmb-jet28-rev.-3-with-short-steering-nozzle
Included in the files are mounting brackets for 36mm and 28mm diameter inrunner motors as well as a mount for common airplane motors using 19mm hole spacing. If you need a bracket for a different motor, let me know the dimensions and I'll make one up for you.
- 2x lipo batteries. You'll want two: one to place in either side of the motor for balance. I will use 2x 2200mAh 3S lipo batteries. I like to use velcro to hold batteries in place.
- 1x transmitter/receiver set. I will be using my Flysky i6 transmitter with receiver
If you have any questions, please do ask. As noted at the top of the page with a link, there is now an improved new version published.
Issues are used to track todos, bugs or requests. To get started, you could create an issue.
I recommend using ABS slurry to join the parts if you printed them in ABS.
ABS slurry is made by dissolving ABS filament in acetone.
If you're using PLA, superglue works very well. A good superglue will bond the parts no problems. I find if you use a 'kicker' (its a glue activator) it joins even stronger.
Have printed 2/3 of hull and it is looking nice. (Congatulations) Just wondering how the sections are best joined together.
@BeniniD, I've uploaded a version that has a thicker eyelet and thicker walls everywhere. Hope this helps.
I have a bit of trouble printing the external propulsion unit.
the semi sphere is very thin, and with abs it is fragile.
I advise you to enlarge the walls externally and reinforce the eyelets.
today I try a petg print,
I update you!
ho un po di problemi a stampare il gruppo esterno di propulsione .
la semi sfera è molto sottile , e con abs risulta fragile .
ti consiglio di ingrossare esternamente le pareti e rinforzare gli occhielli .
oggi provo una stampa in petg ,
Thanks! Yes I've just uploaded the STL file for the lid. It doesn't seal very well but it should be ok if you use a soft foam strip. The next version of the design will have a much better lid since this the surface is flat. It is much easier to design a lid for it: https://i.imgur.com/QHB7cP0.png
I haven't made much progress on it lately since university has been really busy and other things have been soaking up a lot of time. If you ever want any other files just let me know and I'll upload them :-)
I look forward to seeing your boat go!
hello Jotham B
I wanted to compliment you on the project.
I'm printing the hull, aware of the problems you've encountered.
would you load the lid file, so over the weekend I mold it and go to the lake to test it?
thank you so much !