I've wanted to build a jet boat for years, but never got around to it. Thanks to the wonderful designers/testers over in the 3D printable Jet Drive thread, I've decided I might as well get started on one. I won't bore you with any background, I'll just get down to it.

I'm using the Bermy plans scaled to 70% (700mm) and the 35mm jet pump.

I've been 3D printing on a homebuilt machine for a few years now, but mostly PLA. I decided this was a good reason to give PETG a shot. Besides 2 or 3 calibration prints, these are my first ever PETG prints (black and orange are PETG, the white nozzle is PLA), and I'm quite pleased with the quality. I'm going to be re-printing the pump, as I have a better plan now for affixing the intake grate to the pump than my first attempt.



The hull is 3/32" and 1/16" ply, with 2 sections in 1/32", as I ran out of the (obnoxiously expensive) plywood from my LHS and had to dip into my scraps from projects of yester-year.

I'll try to keep this thread updated as I go, but here are a few shots of where I'm at so far. Any critiques or advice is appreciated, as this is both my first jet boat, and my first electric boat.

Hey, Mitey and welcome.

There are a couple of us here who can help you.

I have a 350mm version of the Bermy hull and a 750mm jet boat which is closely based on it.

I do have some advice for you straight off the bat as it happens...

- design a hatch before you go much further. You're almost certainly going to need one!
- (you're not going to like this one, sorry) consider ungluing the top side pieces and re-cut them to incorporate the superstructure. It will leave you a much neater, lighter and stronger job.

You could read through my 1/6 scale thread for a more detailed account of the building process :-)

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Welcome!

I am really wondering how the 35mm drive will power this size of the Bermy hull!
I have good faith in this size of our jet-drive.

Dunk, I think I know what I'm going to do for a hatch. Obviously I won't know how well it's going to work until I it all together (who knows, maybe it will be a flop) but I'm going to do something similar to the way I build my radio boxes. I read your build thread once or twice already, but I'm sure I'll end up referencing it again many times before I'm done. Too late now for me to re-cut the sides (if I ever build another, I'll consider it). More wood for this thing means 2 hours of driving and $40 worth of ply. This is already looking like it will end up being spendier than I wanted!

URC, looking forward to trying your drive and letting you know how she goes!

Well that was quick. I just went to mock up one of the bottom pieces, only to find it doesn't fit. It's not nearly long enough, and the curve at the front seems way off. I don't know if this is something that could easily be solved with some patch panels or not. Whenever I encounter extreme fitment issues this early on in a build, it's not usually a good sign.

Did you scale it uniformly? Can you post more pics from above?

Your version seems very wide, perhaps only scaled in one direction, maybe? Just trying to understand why so short.

bermy

Did you size the bottom piece from a flat overhead view? Curious.

One way of making panels is to first cut them from shoebox-like cardboard and then bend, fit and cut to fit around the form or framework correctly. Then flatten the cardboard panel again and use it as a template to cut your wood.

Bermy, it's all printed at 70%. I've got the "spoiler" glued on and drying, I'll try to take a picture tomorrow. It's not just short, the curve at the front doesn't line up well either.

Air, they're printed plans, I didn't design it. The wonderful bermy that posted previous to you designed them (thanks again!)

Bermy, it's all printed at 70%.

Mystery solved. Thx for the info.

Originally Posted by MiteyF

Well that was quick. I just went to mock up one of the bottom pieces, only to find it doesn't fit. It's not nearly long enough, and the curve at the front seems way off. I don't know if this is something that could easily be solved with some patch panels or not. Whenever I encounter extreme fitment issues this early on in a build, it's not usually a good sign.

The curve on mine was way off. I chamfered the front sides of the longitudinals to help the side pieces meet easier :-)

I had to add a few patch panels up at the front when I did mine as well. Other than that everything fit together pretty well.

Looking good so far.

The hull hasn't moved very far, but I printed another pump housing, this time in Inland black PETG. I've got my settings pretty much dialed in now, she's printing wonderfully.

I cut some SS TIG rod for the intake grate, and (without measuring obviously) sat them in place one at a time. I set my soldering iron for 350* C with a trashed tip, and applied pressure to the TIG rod, which melted the plastic and sunk in the rod to just below the surface. Then I took a piece of filament and basically "soldered" over top of the rods to lock them in place. I hit the bottom with a sanding block real quick to see just how uneven it was. It's ugly, but very strong, and as you can see, still quite flat. I could touch it up more if I wanted to, but I think this will work just fine. You can't tell, but the TIG rod extends the entire length of the rectangle that sits proud of the housing.

The hull is coming along. I haven't weighed it yet, but it's even lighter than I was thinking it would be thus far. The lack of bulkheads in the rear makes me think I'd be best off putting on a light layer of glass on the outside instead of just epoxying for waterproofing.

However, I'm wondering if I'd be better off with the 45mm drive... any thoughts? This hull makes the pump look a bit lethargic.

I'm a fan of shoehorning big drives into small spaces, but you've got plenty of room there. If you can spare the bucks for the bigger components ('bout another bill), I vote go for it. I don't think you'll regret it.

BTW, your water pickup looks like it is almost vertical. I've found you're likely to get better flow if you angle it a bit like the picture below (perpendicular to the stator surface).

Your little buddy down there in the 1st photo has a look on his/her face like "Put that thing down, whatever it is, so we can go outside and play ball.".....

I get that look from my dog all of the time.




Keep in mind that due to the lower efficiency of smaller pumps, the size of the pump in relation to the size of the boat will look smaller as the scale of the boat gets larger. The 19mm pump on the back of a common NQD looks big on the boat compared to the real thing ( and HUGE when one upgrades it to a 28mm). When you get to full size boats, nozzles look very small relative to those on our models.







That said, we are always looking for more power. If ya wanna go fast, go big(ger)!