Straight to the point, gonna build a lowdraft jetboat for cleaning up about 2 miles of creek.
working on designing the engines "jet part" not too much online information on how exactly the "jet part" part of the engine works. Been looking a lot of RC related jet boat posting, seems like a lot of the math and testing has already been done for rpm to prop pitch to intake to nozzle sizes. so mainly working off that.
Anyone here have any sort of experience just working one these things?
I have everything else I need design wise, but this whole jet thing, and not that I suspect it to be cheap, but a used jet cost so much freaking money I haven't been able to find one for cheap enough. plus since the boats being built from scratch anyway I figured I could also make the jet part from scratch just gotta get the numbers correct. also some way to get a reverse.. I'd assume it sorta works like reverse thrust like on some jet aircraft.
>>968274
The creeks got lots of fallen trees in it, that sit just below the water, we've tried to take a regular john boat with an outboard out to clean it, but some spots are really bad, and require you to go over the trees first before you should cut them, because we're using the boats + electric winches to drag the logs to the banks, otherwise they'd fall to the bottom, and eventually get floated/pushed to the next low part or choke point of the creek and get super stuck, we've already removed ones like this and it was a huge PITA because they get stuck under live roots and cypress knees underwater and all this junk.. its easier to pull them out of the way and push them up onto the banks now while we're cutting vs leaving them at the bottom and making them a bigger issue.
we don't need them super clean either, just enough so a john boat with an outboard can safely travel up and down it. nothing sucks more then breaking your prop on a hidden 800lb log under water...
>>968278
And here's an example sorta what I'm talking about. since we use the boats for moving the logs around, you can see how getting over the log first benefits one.
A: no bend to pull the log through.
B: once over, you have a straight away to pull the log up
C: can use a combination of the flow, and a pulley off the bank, with a winch rope pulling it towards the bank, and the flow keeping it from anchoring it to the bottom.
the absolute madman
Moving a waterlogged 800 lb tree sounds like a hell of a job for a jet drive, especially a DIY one.
Any reason you can't just slide into a pair of waders and get it done with block and tackle?
>>968274
Lots of stuff about jet boat thrust came up by Googling 'Jet boat thrust'.
Water jet propulsion isn't going to be as efficient as a prop at low speeds (jet boats excel at higher speed). But if the trade off is broken props and snagging your lower drive unit, it might be worthwhile.
>>968704
sorry should of been more clear on this. I did mention it how ever.
what we've been doing is tying off a boat to a large tree off the bank. and using an electric winch mounted to the front of the boat to drag the logs around. once we got the logs where we want to pull them up onto a bank [where they will fit] we tie a rope to the log to keep it from moving away, unhook the winch cable, go on the banks, hammer in a steel tripod, with a pulley in the middle of it, wrap the winch cable around the pulley, and re-attach the cable to the log, and pull the log up onto the bank.
>>968773
the trade off is definitely needed for this type of low level water and work, the boat is mainly acting as transport for persons and supplies, and something to connect a winch too. I've been working off borrowed boats, and have busted too many engine bits and having to afford to replace them.. broken props and rudders are fkin expensive.
>>968274
Use lots of tannerite.
>>968863
the aluminum sheeting used for the boat is gonna be expensive enough anon... thank god it comes in 10' long sheets.
>>968773
>>968849
Another option you might want to consider that is both very easily /diy/ and also perhaps more suited to this job is a simple guard around an existing outboard prop.
But if you MUST go with a jet, for your application I'd recommend going with a centrifugal one like pic related.
>>968911
My jet was going to be an inboard style'd jet. the one like in your picture looks like it still might take damage from hitting logs and low stuff? why this style?
>>968931
>the one like in your picture looks like it still might take damage from hitting logs and low stuff?
No, that's the entire point.
>why this style?
For operating in shallow and debris-ridden waters where open propellers aren't suitable...
But it sounds to me like you're just looking for an excuse to build a particular type of jetboat. So go ahead, do what you're gonna do, OP.
>>968937
>Muh he asked me questions why he should use this particular type of jet turbine.
>Muh thread about not knowing much about jet boats to begin with
>Muh gonna be an asshole anyway because he asked me a question.
it looks like you're just looking for an excuse to make shit up and to see words that were never written. and be an asshole for no fucking reason.
>Muh got mad because I "Thought" someone was disagreeing with me
accusing me of exactly what you just did.. satire m80.
tumblr >>>>>> that way >>>>>>>
![hqdefault[1].jpg](https://i.imgur.com/q3DmaY7.jpg "hqdefault[1].jpg")
>>968274
Have you considered a mud motor? Plenty of people navigate very shallow waterways. With jets I'd be concerned with sucking in debris and rocks and screwing up the impeller.
>>969117
We dont got rocks where I live... So thats not a worry. And any prop is gonna get damaged possibly if it gets hit by something big enough. Even running into fishing line can fubar you.
But I have considered a mud motor.. The thing I don't wanna break the props. Ive considered building some sort of cage around a mud motors prop. And having a hinge on the shaft to the boat. So when the boat hits something. Then the shaft comes in and hits it. The shaft pops up for a second and comes back down.
>>968274
Air boat to get to log
tie long chain to log
then have big anchored wench on land to pull
+ guide log with second chain tied to air boat or other part of land to help insure correct orientation of log or just nudge it with air boat
+if you need to move it further to different spots then get two big anchored wench on land to pull in a hand off style to swing the log down to where you want
Not the fastest but it is simple and cheap. You don't sound like you want to invest that much into it. Because after all you aren't doing this as a full time job for the lucrative lumber money right?
Jet boats cost a lot because jet water motors are much more complicated than they sound. Building one for this project sounds needlessly complex and hard. I have seen people make DIY air boats, but never heard of a DIY jet boat.
>>968868
Tannerite is a poorman's explosive
Easy to make and arguably safe for something that explodes. Also a number of places allow small amounts to be used with little legal trouble, but double check with the government in writing before you start manufacturing explosives for obvious reasons.
>>969480
More im learning about jets. The less complicated it gets. Like a jet engine on a plane. They are pretty stupid easy to understand and its mostly about tolerances.
Also airboats at least anything worth while. Run off of aircraft fuel.. The engine I was thinking about running on my boat was a little diesel powered single turbo 4000rpm at the crank. Motor. I also have some older motorcycle motors but idk about their weight vs the power you get. V4 800cc and you're only making a realistic 54ish hp. Vs the diesel thats making about 100hp but 150ft.lb of torque. And both weigh about the same in terms of total gross weight.
Also its not exactly I wanna spend 10 grand on the project.. Thats my maxing out limit. That boat itself should be 4ish grand to finish. So its more like the best features for how I want to use it and where. Im not over complicating things for myself and im on a pretty steady course. I choose the jet way because it had the best features for what I wanted to do with it. And I'm not looking to race the thing or anything. Probably end up using it for fishing mostly. And just having fun.
>>969491
Aircraft fuel is kerosene. Kerosene is basically diesel. Sometimes just needs thinning with white spirit to make it run in a diesel engine.
Anyway that's beside the point, you can put whatever engine you like on an air boat, as long as it turns the prop
>>969491
>V4 800cc and you're only making a realistic 54ish hp.
are you high? My motorcycle is 23 years old now. 750cc, it makes 100hp at the crank (measured) after all those years, and 7.45 kgf-m torque (over 52 ft lbs for yanks). It also revs up to 12000 RPM. It would be way more useful than any diesel engine.
The best part, an engine is only 300 euros where i live.
>>970227
Avgas is high-octane gasoline, not kerosene/fuel-oil. You're thinking of jet fuel.
>>970276
Yeah I was, Jet A1 is what we call it. Avgas slipped my mind completely, whoops
>>970339
Power , a function of a force and the rate that force is applied at, literally tells you how much work is being done.
That way you can understand why a boat when fitted with a screaming 250 horse power engine can fly out of the water, when before, the previous 150hp lazy boy could only manage cruising speed despite them making the same amount of force (dem torks)
