Model Boat Mayhem - Forum

Dry Dock / Shipyard: Builds & Questions => Pleasure boats, Sports, Race, Power and Leisure Boats: => Topic started by: Mad_Mike on March 19, 2012, 09:50:35 AM

Title: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 19, 2012, 09:50:35 AM
i had posted in temp forum but ill repost it here and do a build thread.

Iíve always fancied having a go making my own water jet, yeah I know you can buy them and thereís even a really cheap eBay one but it defies the point of what Iím trying to achieve, a complete bolt in unit just wonít cut it for me. Now I have read threads on mayhem and other places about the attempts and regular failings of people trying to make your own jet unit by mounting a propeller inside a piece of pipe and then trying to make a stator which counteracts the swirling affect of the water at the output. I have tried this method myself before so I know first hand just how difficult they are to NOT make as such but make affective. So knowing what Iím up against Iím going to attempt a different approach fit it to a model then see what happens.
A toy battery operated boat of my sons has a jet pump inside it. I remember when I was a kid having lots of these small bath boats and also remember the transition from a standard propeller to these internal impeller style crafts. You donít see many battery operate toy bath boats these days with a propeller no more. One of those things health and safety slammed down on. Anyway hereís the little boat:

(http://s13.postimage.org/40w1q1hir/SDC14529.jpg) (http://postimage.org/image/40w1q1hir/)

and heres the jet unit:

(http://s13.postimage.org/a9lyxd4hf/SDC14530.jpg) (http://postimage.org/image/a9lyxd4hf/)

with the cowling off:

(http://s15.postimage.org/m3yrs493b/SDC14533.jpg) (http://postimage.org/image/m3yrs493b/)

The motor is mounted onto a vertical axis at the stern. My idea is to incorperate this basic pump design into a larger scale and power it by a 540 or hopefully a brushless motor. Its principle is allready used in bait boats and even some types of outboard motor:

(http://s16.postimage.org/dt7wn6781/Optimax_Jet110.jpg) (http://postimage.org/image/dt7wn6781/)

So Its not the first time this has been done. Using a 540 27t motor ive designed and fixed a centrifugal pump on the end too see what would happen:

(http://s18.postimage.org/5wx2psrhh/SDC14535.jpg) (http://postimage.org/image/5wx2psrhh/)

The impeller rotor is 34 mm in diameter and the hole unit is contructed from plastic card. A plate goes over the top to complete the impeller housing and simply bolts togeather. Ive done a test run and heres a youtube link of it working:

http://www.youtube.com/watch?v=nZ1gJeuas7M&feature=channel

From what i can guestimate using the kitchen scales the thrust is about 2 lb's, which i think which move a fairly small boat relatively nippy. ill have to see.

(http://s17.postimage.org/ae37tp9uj/SDC14534.jpg) (http://postimage.org/image/ae37tp9uj/)

The combined height of the motor and pump is a fairly lofty 3 inches. I dare say the boat it will be built into will be no more than 16 inches long. Big enough to incorperate the weight and size of the jet unit and its ancilleries but not to so large and heavy that the jet wont have any affect on it.  The draw back is that at that length and this motor height the chines on the side of the boat would look rediculously tall!! I need to get the overall height of the pump down so as to bring the profile of the hull down too. unless i have the top of the motor sticking out the deck inside a box or something, which id reckon would look pants!!
I was thinking maybe a low profile 2200kv outrunner to replace the standard 540 motor. Does anyone know if this would work or would the pump overload the outrunner?

Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 19, 2012, 12:10:28 PM
i have to admit when i saw your home made unit i thought nahhhhh. it wont pump much but the you tube video proved me wrong. well impressed. many many years ago i made an  axial flow unit powered by a OS40 motor. it could certainly shift some water and was really useful for emptying my little pond but never actually ended up in a boat. wished i had finished it now.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 19, 2012, 12:51:15 PM
I was quite suprised myself at how well it worked. When i come to building the boat ill build the pump housing into the hull itself rather than mount this test one. I think a nozzle or venturi of somekind will concentrate the water flow and maybe even increase thrust. Thats the theory anyway :D
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 20, 2012, 10:03:35 AM
there is an optimum size for nozzle to inlet size.  i think the outlet is 1/3  or thereabout smaller than inlet for best results, dont quote me though.  i do know you will decrease thrust if you go too small.  i'm sure someone will correct me if i'm a long way out. a question for you though. what sort of glue did you use to stick the blades on?  i have never had a lot of success glueing plastic card.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 20, 2012, 10:18:03 AM
Ill have to do some more research. The blades are stuck on with CA glue. I rub down the entire plasticard both sides and then it sticks solid. ive ran the motor on 3s and got the blades spinning about 26k and didnt explode, so far so good. touch wood

Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 20, 2012, 11:00:01 AM
Mercury (amongst others) have been using this for decades. Only difference is that the impeller is made from rubber and the blade tips are deformed by the casing to get the seal. Oh yes, it's the watercooling pump for the engine and on the prop driven O/B's is mounted in the bottom of the rear "Stalk".

   Surprised Styrene iis difficult to glue if the basic material is chemically clean and using a solvent type cement. Cyano is eventually degraded with water.

  Regards  Ian.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 20, 2012, 12:39:47 PM
Of course i realise that the method is allready used. What im trying to do is replicate such a system on a basic principle level using basic tools and minimal funding. I will agree that CA does degrade with water BUT only when exposed to extended periods of submersion. Seeing as the boat wont be on the water longer than 20 minutes at a time it doesnt cause a problem. Ive built now 12 boats all with CA and the ones i built last year are still holding strong. If any part needs a bit extra i use epoxy.  Im just trying to write a build thread thats a bit different. Once youve read one build thread of a boat you basically read them all because the process hardly ever changes.
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 20, 2012, 12:49:12 PM
Wersern't a knock Mike, difference is, the "Prop" is churning the water about so you're doing what manufacturers call an "Accelerated Life Test"  :-)  The solubility of Cyano is just to remind some that it is a factor.

   Regards   Ian
Title: Re: Water Jet experiment and Jet boat build
Post by: gwa84the2nd on March 20, 2012, 03:26:22 PM
looking good ther mike might have to steel the idea and have a go myself with that one
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 20, 2012, 05:04:03 PM
Wersern't a knock Mike, difference is, the "Prop" is churning the water about so you're doing what manufacturers call an "Accelerated Life Test"  :-)  The solubility of Cyano is just to remind some that it is a factor.

   Regards   Ian

Im sorry i thought it was a dig. I hope you will find myt build thread interesting. when it gets going at least :-))
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 20, 2012, 05:05:51 PM
looking good ther mike might have to steel the idea and have a go myself with that one

by all means give it a go. Some point hopefully by the weekend ill start the boat build, and it would be interesting to see what other people can do. maybe you will do a better job.
Title: Re: Water Jet experiment and Jet boat build
Post by: gwa84the2nd on March 20, 2012, 05:50:57 PM
i will probably buld it in metal and wack a nitro engine on it  lol more pawer  :-))
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 20, 2012, 06:51:28 PM
I dont know much about nitro, ill take your word for it. I dont think metal would be best suited though as its heavy. cast resin would be best i think.
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 20, 2012, 09:00:44 PM
Mercury (amongst others) have been using this for decades. Only difference is that the impeller is made from rubber and the blade tips are deformed by the casing to get the seal. Oh yes, it's the watercooling pump for the engine and on the prop driven O/B's is mounted in the bottom of the rear "Stalk".

   Surprised Styrene iis difficult to glue if the basic material is chemically clean and using a solvent type cement. Cyano is eventually degraded with water.

  Regards  Ian.


i don't think most people have a problem with glueing card....just me. LOL. I do clean and rough the surfaces and the glue sticks but has no strength. i have found pvc glue works well but takes a while to set and is messier to apply than the proper glues


Modified
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 20, 2012, 09:03:42 PM
while i'm here. can someone please tell me why my previous post is included in the quote. what am i doing wrong. not the first time its happened.
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 20, 2012, 09:13:49 PM
while i'm here. can someone please tell me why my previous post is included in the quote. what am i doing wrong. not the first time its happened.

 If you've pressed the quote button on the top RHS of the last box, you then need to click below the [/quot] before typing your own comments. And yes, I did deliberately misspell quote.

   Regards  Ian.
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 20, 2012, 09:24:00 PM
To go back on post, once you start to refine the idea, if you look at the impeller of a turbine, there are extended and curved over inner lips to the blade, like the leading edge of a normal prop, to scoop the water or air in and fling it to the outside. All very clever but far from Mikes simple but very effective build. Krishnas pancake VHS motor rewind would be ideal as a low profile drive unit.

  Regards  Ian
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 21, 2012, 08:11:12 AM
I could have a go at making the scoops on the waterpump impeller. I need to build the boat first but the impeller could be improved on later.
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 21, 2012, 08:20:03 AM
my impellor was 50mm diameter.  4 brass blades on a brass hub with overlap. quite tricky to silversolder.  aluminium housing with a stainless wear ring and phosphor (sp)  bronze bearings. but worth the effort. as i said previously it could certainly pump the water.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 21, 2012, 09:08:58 AM
the picture looks like the traditional hamilton jet type impeller. Did you make the jet yourself? how did you do the stator?
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 21, 2012, 09:57:39 AM
a bit of cheating there.  :embarrassed:it is a traditional impellor. (never took any photos of mine. this was well before digital photography etc). mine was very similar though. stator was brass strips silver soldered to a hub and pressed in bearing.  the whole thing was then pressed  and loctited in to the 'pump housing'.  there is a local engineer here who milled three impellors out of a block of brass and made a three stage unit powered with a chainsaw motor. that was impressive to see but our local boating pond is really a large puddle so he cant wind it up to anywhere near full speed. good for soaking the spectators though . {-)
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 21, 2012, 10:13:49 AM
The type I was reffering to is the centrifugal type as used in turbos and the original "Goblin" jet engine in where the outer parts of the blade are as Mikes and the inner part are curved over. What it should allow is that the unit doesn't need to protrude below the hull as the first photo.

  Once you start  hanging an "Engine" on, you might as well go back to the Hamilton/Taplin Hydrojet prop in a tube.

  Regards  Ian.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 21, 2012, 10:17:41 AM
sounds impressive. If i had access to the facilities id go the hamilton jet type route but when i tried it last time it failed miserably. The method ive chose is easier to make on the dining room table and im fairly confident it will work, I hope  :embarrassed:  Im not going to poor piles of money in it though because if its just feeble i havent made a great loss.
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 21, 2012, 10:26:22 AM
I was still working on the plastic option Mike. By "Engine" I mean where the Juice is a hydrocarbon derivative.

  Regards  Ian.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 21, 2012, 10:39:59 AM
The type I was reffering to is the centrifugal type as used in turbos and the original "Goblin" jet engine in where the outer parts of the blade are as Mikes and the inner part are curved over. What it should allow is that the unit doesn't need to protrude below the hull as the first photo.

  Once you start  hanging an "Engine" on, you might as well go back to the Hamilton/Taplin Hydrojet prop in a tube.

  Regards  Ian.

I googled some images of impellers and it seems that the air compressor type centrifugals have the scoops on. What i intend to do is have the central section of the rear of the boat flat:

(http://s14.postimage.org/91hw4dct9/om33144.jpg) (http://postimage.org/image/91hw4dct9/)
(http://s10.postimage.org/o2fyg5nrp/yd81286.jpg) (http://postimage.org/image/o2fyg5nrp/)

then build the pump inside the hull rather than hang it off the bottom, so that its still flat. The impeller ifself will be just below the waterline so it is fully bled as soon as the hull touches water. If the speed of the boat gets to a point where its bouncing on the ripples of the lake then i may have to consider the scoops on the blades or even a ram scoop on the inlet to the pump to aid bleeding as it jumps in and out of the water. Otherwise as soon as the boat gets a bit of air under it the pump will go dry, stop thrusting and the boat will stall.
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 22, 2012, 05:43:56 AM
it will cavitate but should take off again as soon as it hits the water. the original hamilton jet boat was just as you are building. a centrifugal pump mounted inside the hull but with a right angle gear box on top connected to the engine. thrust improved quite a bit when he raised the outlet above water though. check this site if you like    http://www.hamiltonjet.co.nz/hamiltonjet_waterjet/waterjet_history
Title: Re: Water Jet experiment and Jet boat build
Post by: triumphjon on March 22, 2012, 07:54:40 AM
thanks for the link hopeitfloats , very interesting timeline , im also building a jet propelled model , but using the graupner mini jet unit , might try to make my own multi bladed impellor though , we started one for the nqd pump but never got past turning the boss !
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 22, 2012, 09:44:30 AM
that is going to be my next project after finishing my long term container ship build. i have the graupner mini jet too. mine is a few years old but never used. dont like the ugly reversing bucket though. think i will build my own there. have you had your unit running.  the impellor is pretty basic isnt it.  what size hull are you planning to use?   craig
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 22, 2012, 11:17:33 AM
it will cavitate but should take off again as soon as it hits the water. the original hamilton jet boat was just as you are building. a centrifugal pump mounted inside the hull but with a right angle gear box on top connected to the engine. thrust improved quite a bit when he raised the outlet above water though. check this site if you like    http://www.hamiltonjet.co.nz/hamiltonjet_waterjet/waterjet_history

fantastic link thanks for that. It had cross my mind to use a right angle bevel gear box but last time I used one it drained the power and the gears could be heard 30ft away!! 
Title: Re: Water Jet experiment and Jet boat build
Post by: unicorn on March 22, 2012, 03:01:58 PM
 :-) :-) :-) :-) :-) :-)

      Have a look at the Schottel SPJ pump jet  (http://www.schottel.de/home/ )  soon to be released by
   Graupner @ 180 euros  ---  yes 180 euros
                                                                :o :o :o :o :o
Title: Re: Water Jet experiment and Jet boat build
Post by: triumphjon on March 22, 2012, 06:24:17 PM
i will stick with the reverse bucket , ive designed my own dory hull  at 24 " longx 8" beam , of balsa construction which is coated in polyester resin and woven glass tissue .
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 26, 2012, 01:00:21 AM
Since my last post on this subject Ive been waiting for my funding to accumulate and the post to arrive but as of Saturday the waiting was over and so over the last days Ive been getting some building done. Well a lot actually!
First up i received my new motor ESC and gear for the impeller. I ordered from giant cod a cheap and cheerful 2200kv brushless outrunner with a none marked 80a forward only esc. I made a brand new impeller using the gear as a boss for the centre, reversed the shaft on the motor so it came out threw the base and mounted it to a piece of plasticard.

(http://s7.postimage.org/5fipenkzb/SDC14580.jpg) (http://postimage.org/image/5fipenkzb/)
(http://s17.postimage.org/xs932y3cr/SDC14581.jpg) (http://postimage.org/image/xs932y3cr/)

I did a spin test with a 3s lipo and the impeller didnt explode so its all good (touch wood)

I then started working on the pump casing. I marked out the shape of the casing on cardboard drew and cut it out on several peices of ply and plasticard andf then laminated them togeather to build up the height.

(http://s13.postimage.org/tg75s3977/SDC14579.jpg) (http://postimage.org/image/tg75s3977/)

For some reason i didnt take a picture of the completed pump on its own, it will show up in these later pics. Anyway i started planning out the hull. Im not sure yet what type of boat im going to build and have no idea how well it will perform so i built a small but basic hull and HOPEFULLY the jet will provide some ample shove for it.
(http://s13.postimage.org/lfsv3ls9f/SDC14622.jpg) (http://postimage.org/image/lfsv3ls9f/)

I then started cutting out the transom and fitted to the pump. In this picture you can see the inside of the pump housing itself with the impeller off.

(http://s8.postimage.org/ipmiobd1t/SDC14671.jpg) (http://postimage.org/image/ipmiobd1t/)

a peice of tube is fixed into the end of the pump jet, i smoothed off the square to cirlce profile with epoxy putty to improve the flow.

A bit of a frame just to get my started:

 (http://s15.postimage.org/gvz61veqv/SDC14685.jpg) (http://postimage.org/image/gvz61veqv/)

After this im afraid there was a gargantuan leap of progress and i was so busy i forgot to take pictures  {:-{ The Hull is made from entire peices, 2 chines and 2 bottoms:

(http://s13.postimage.org/u1e7olro3/SDC14686.jpg) (http://postimage.org/image/u1e7olro3/)
(http://s17.postimage.org/cj8w86mwr/SDC14687.jpg) (http://postimage.org/image/cj8w86mwr/)

The blocks running up the inside of the chines reinforces the seam with the bottom and the **** at the front just holds it togeather while its drying. The interior is not pretty but once the deck is on it wont be seen. A few more gaps need filling but ive pretty much got this part out of the way. Heres a pic of the pump casing closer up:

(http://s14.postimage.org/3y430nl99/SDC14692.jpg) (http://postimage.org/image/3y430nl99/)

another update coming soon :-))
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 26, 2012, 08:45:58 AM
WOW. you certainly get stuck in when you do a project. that would be 3 months work at my rate. well done
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 26, 2012, 09:14:14 AM
WOW. you certainly get stuck in when you do a project. that would be 3 months work at my rate. well done

yeah i build too fast sometimes. I find that i spent weeks saving up and gathering stuff, spend a few days on the build then im bored again for a month  %% Maybe i should span it out a bit more. What was your name before the forum crash?
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 26, 2012, 11:11:54 AM
hopeitfloats. no name change
Title: Re: Water Jet experiment and Jet boat build
Post by: Martin [Admin] on March 26, 2012, 03:17:55 PM
Topic Name changed ...... to protect the innocent.....  ok2
Title: Re: Water Jet experiment and Jet boat build
Post by: Sub driver on March 26, 2012, 03:56:36 PM
It will be interesting to see if it works,
Regards sub.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 27, 2012, 12:11:53 AM
progress has been unusually slow today cant understand it. I sealed up the gaps and holes in the hull, fixed the deck and made the coamings for it. I also got it doped and tissued too:

(http://s15.postimage.org/q2hf1mf7b/SDC14693.jpg) (http://postimage.org/image/q2hf1mf7b/)

hopefully if all goes to plan i can try it in the test tank to see how well the pump will work. I really hope it works out as ive had to come along way in the build process to be able to get to a stage where i can test it. Ohwell %%
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 28, 2012, 12:34:37 AM
got the hardware installed for testing and well tested it %%:

http://www.youtube.com/watch?v=jbKVv5fMztE&context=C494aab3ADvjVQa1PpcFOvRVGjVP9sCyzeGfg0zNaeqY1ZxOjJUKY=

The thrust isn't half bad, in fact I'm quite pleased with it. There are some problems however

1 the boat torque steers left.

2 the pump leaks when under pressure

3 the water jet doesn't come out straight which also assists in its leftyness.

Not due to the nozzle being not straight but because there is a direct line of site betweent the outlet and the impeller. I hope the steering nozzle will correct that and make the torque steer more managable. I can fix the leaky pump no problem but the torque steer i dont know what to do about that. It was something that concerned me and was half expecting it, the only way around it i think is using 2 counter rotating pumps instead of one like i have.

Title: Re: Water Jet experiment and Jet boat build
Post by: triumphjon on March 28, 2012, 07:48:15 AM
have you been able to test it in open water yet? the effects of the already aeiriated water in the domestic test tank are probably affecting the directional control !
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 28, 2012, 09:07:25 AM
not yet, i had only installed the motor 30 minutes prior to shooting that clip. The cardoard on the deck is just a temporary cover to stop water going inside during the test.
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 28, 2012, 09:37:35 AM
A keel might assist although you may be suffering from gyroscopic precession. (Look it up)  O0

   Regards   Ian.

   Looks like you may have built a waterbourne helicopter problem.
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 28, 2012, 09:53:05 AM
On full sized outboards (There were on me Mercury) is a "Trim tab" that was set to counter the steering effect to enable "Hands off" straight line. Your steering device, tube or blade, should allow you to trim out the vertical rotation by deflecting the thrust to one side. A keel would also assist.

  Regards  Ian.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 30, 2012, 01:00:10 AM
Another update. Due to the fact im not working from a plan and just making it up as i go along the build stages on the thread are a bit whats the word spaced??   {:-{ anyway heres some pics for you to have a butchers:

(http://s15.postimage.org/i2xe8bauf/SDC14777.jpg) (http://postimage.org/image/i2xe8bauf/)
(http://s17.postimage.org/etx9dzkcb/SDC14795.jpg) (http://postimage.org/image/etx9dzkcb/)

Ive decided to base my boat on one of those New Zealand jet sprint boats. I googled some images, saved them and constructed the typical style from ply. Eventually the boat will have a roll cage dummy engine at the rear and 2 figures from shoulder height sitting at the front. Wont look very realistic but i want it to function not look pretty and a cavenous footwell will just fill with water which i have experienced from a previous build.

The steering nozzle:

(http://s13.postimage.org/xwvss9eab/SDC14790.jpg) (http://postimage.org/image/xwvss9eab/)
(http://s14.postimage.org/v2g8vpmsd/SDC14789.jpg) (http://postimage.org/image/v2g8vpmsd/)
(http://s13.postimage.org/pjupbc4gj/SDC14792.jpg) (http://postimage.org/image/pjupbc4gj/)

I want the pump to be servicable so all the components are easily removed with a screw driver. Its all made from plasticard and a bit of water pipe, the aluminium bar holding down the servo is actually a offcut of a ruler. It was something like 8 quid for a metre length of ali and i didnt need it all so i bought an ali ruler for about 2, rubbed the paint of it and cut it up. Thats a servo horn stuck to the side of the nozzle by the way, im fairly confident its up to the job.

Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 30, 2012, 01:08:39 AM
On full sized outboards (There were on me Mercury) is a "Trim tab" that was set to counter the steering effect to enable "Hands off" straight line. Your steering device, tube or blade, should allow you to trim out the vertical rotation by deflecting the thrust to one side. A keel would also assist.

  Regards  Ian.

I intend the run strakes along the bottom of the hull.  how big would the keel need to be? i was trying to avoid hanging stuff off the bottom {:-{

Im not sure though if i should point the steering nozzle slightly starboard to counter the affects of gyroscopic precession (Ill call it GP from now) or to put basically a small rudder or stator inside the nozzle to bias the flow to the starboard side. what do you think?
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 30, 2012, 10:46:54 AM
i wouldnt put anything in the nozzle. put a bit of RH down on your steering trim.  build looks good by the way. beautiful work on the plastic side especially. pity about the strut holding the steering nozzle hanging below the hull though. hope that doesnt effect the steering or cause pump cavitation.
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 30, 2012, 11:26:10 AM
Seconded on the trim offset :-)) I'm sure that the final design will have the "Strut" As part of the bottom plate as will the use of countersunk screws.  Looks very professional though.

  Regards  Ian
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 30, 2012, 11:47:44 AM
ill put a bit of right hand on the nozzle then. nice n simple.

Im afraid circlip that this is the  final design itself  :embarrassed:, sorry if you were expecting something a bit more lavish but has boat has cost me 30 quid so far and dont even know if it wiill work yet so im not gonna go nuts. Just using what i have to hand  O0
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on March 30, 2012, 12:09:26 PM
i'm sure it will work going by your posted videos. but dont forget to take one at the official launch which will be   /  / 2012.? (fill in appropriate date) :-)) :-))
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 30, 2012, 12:31:02 PM
dont know when that will be wont be long though. need to think of a colour scheme at the minute. Im thinking blue.
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 30, 2012, 01:41:00 PM
White or pale yellow are easier to see submerged  :-)) %)

  Regards   Ian.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 30, 2012, 03:05:22 PM
very funny   <*<
Title: Re: Water Jet experiment and Jet boat build
Post by: Netleyned on March 30, 2012, 04:06:40 PM
Have you thought of a name yet?

Gazunder sounds good  %% %% %%

Only joking Mike


Ned
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 30, 2012, 04:38:53 PM
what makes you all think its gonna sink >>:-(
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 30, 2012, 08:28:11 PM
Not thinking about it sinking, just the sheer power from the waterjet driving it under.

  Regards   Ian.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 31, 2012, 07:58:01 AM
funny how at the beggining  of this thread people were doubtful that the jet would produce any thrust at all %) I dont think it will drive it under, im fitting strakes to it at the minute. Ive dicided to go with mettalic blue. ill put some go faster stripes on it too, just in case its slow.
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 31, 2012, 11:14:11 AM
Quote
funny how at the beggining  of this thread people were doubtful that the jet would produce any thrust at all

  Not everybody, some of us remember the Hoover "Senior" (Cast case one, not the plastic version.) O0

  Lots of years ago, when electric powered "Kipper boxes" had just been invented, a demo at one clubs open day saw a very effective submarine every time he opened the throttle. {-)

   Regards  Ian.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on March 31, 2012, 12:01:13 PM
why did it submarine?
Title: Re: Water Jet experiment and Jet boat build
Post by: Circlip on March 31, 2012, 01:36:04 PM
Combination of pointy nose, heavy batterypack for size of hull (Note I said early, lots of "C" sized cells soldered together) and prop trim a bit orft. It bounced when power was applied and on landing, the pointy bit dug in before the guider reacted. Bit like a bouncy landing but substitute the grass for water.

  Regards  Ian.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on April 03, 2012, 12:33:06 AM
been a while so heres an update.

First up i wanted some drivers and so i flicked threw ebay and managed to find these guys:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=160776307985

I figured that the scale is about 1/10th of the boat and two of these vacuum formed racing drivers will do just the trick. Firstly i cut off the plastic edges then on one of them hacked off his arms!

(http://s17.postimage.org/rgp9p66y3/SDC14798.jpg) (http://postimage.org/image/rgp9p66y3/)

I only need one driver of course so a little bit of work was required. After hacking off his arms i used my lighter to warm up and bend the plastic to follow the new pose of the co driver if you like. I then used the pieces of plastic that i cut off to fill in the gaps around the side and between the arms off the co driver, i reckoned matt red would do just fine for their suits. Ive also been painting the boat itself. I went in the end for metallic blue which i suppose i allways had the intention of doing anyway. I suck at painting so dont expect Leonardo Da Vinci brushwork or you will be disappointed:

(http://s8.postimage.org/v7y3v50q9/SDC14804.jpg) (http://postimage.org/image/v7y3v50q9/)

the drivers are just positioned temporarily for the camera shot.

Ive also plumbed in water cooling for the esc:

(http://s17.postimage.org/oe2saed2j/SDC14802.jpg) (http://postimage.org/image/oe2saed2j/)
(http://s7.postimage.org/svxqglphj/SDC14803.jpg) (http://postimage.org/image/svxqglphj/)

the ESC is from giantcod and a budget one to say the least, forward only it is however pretty good. Being of oriental origin i went over kill on the amp rating just in case:

http://www.giantcod.co.uk/80amp-boat-p-404814.html

The motor doesn't draw anywhere near that kind of current, for 13 quid though i cant complain. I dont even think it was necessary to watercool it but i did anyway simply because you never know. The water picks up from inside the nozzle by a small piece of brass pipe with a 45deg chamfered end. i tested the system once plumbed in and it makes a nice slow but affective trickle. Just the job :-))

On the other hand however Ive got a problem.  {:-{ the bush which the motor spindle goes through into the pump housing leaks. Only when the motor is turning though. I thought i had cured it buy putting a large diameter washer between the impeller and the bottom end plate of the pump housing, then packing it with grease. It hasn't worked so i need to do some rethinking, I have a 3.17mm wide motor axle which i will exchange for the standard shorter axle. With the motor spindle extended going through a snug fitting brass tube and the motor sitting higher I hope it will cure it. hopefully {:-{

oh by the way the steering nozzle works magic and straightened out the jet stream perfectly. I turned the nozzle starboard to counter the effects of the GP which i had previously anticipated to be a problem, I tested it in the domestic tank and the boat turned to starboard rather that port like it did in the youtube clip. I backed off the bit of right hand until it ran straight, funnily enough the steering nozzle was centre again. Therefore the the original problem of turning wasn't down to the motor torque but because the water jet was coming out at an angle.

So there you go :}
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on April 04, 2012, 11:21:07 PM
I managed to gain some control of the leaking bush by exchanging the standard motor shaft for a long one and running to through about 12mm of brass tube:

(http://s16.postimage.org/hah4phqlt/SDC14809.jpg) (http://postimage.org/image/hah4phqlt/)

Its not completely dry though and a little water does seep through into the motor but it doesn't seem to be having any detrimental effects. I hope that once the boat is water born and planing that the issue will be lessened.

Ive painted me crew too:

(http://s8.postimage.org/7fa3br701/SDC14811.jpg) (http://postimage.org/image/7fa3br701/)

theyl do  :-))
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on April 06, 2012, 04:23:15 PM
Ok so ive just about completed the deck features. first up a roll bar:

The roll bar is made from plastrut. I was dead set on having the corners rounded rather than mitred at 90 deg so i had to come up with a plan. In order to bend the plastic i had to heat it and bend it without it kinking so to overcome this i decided to insert a peice of wire or something in side the tube to stop it going flat. I gathered various tubes and wires at first including a bike lock cable. The original tube splintered when melted and the bike lock cable was an absolute ***** to cut. I settled on using curtain wire and plastrut tube in the end and the wire fitted in the end perfectly:

(http://s14.postimage.org/qjir55tjx/SDC14814.jpg) (http://postimage.org/image/qjir55tjx/)

I stripped the plastic off the curtain wire to reveal the coil:

(http://s14.postimage.org/kg5ryzsnx/SDC14815.jpg) (http://postimage.org/image/kg5ryzsnx/)

I reckon that this curtain wire will make a good flexicable for something, it was only 57p too:

(http://s16.postimage.org/sueikh72p/SDC14817.jpg) (http://postimage.org/image/sueikh72p/)

Anyway i marked off where i wanted the bend in the tube and inserted the cable into the pipe:

(http://s13.postimage.org/r28on3hf7/SDC14819.jpg) (http://postimage.org/image/r28on3hf7/)

I heated the tube gently with my lighter then bent the tube with the wire inside, I let the tube cool off then pulled the wire out of the end:

(http://s15.postimage.org/ggw7kkwbr/SDC14823.jpg) (http://postimage.org/image/ggw7kkwbr/)

I think the result is pretty good altough the diameter does shrink a bit, but then i suppose if you were to bend steel tube in a pipe bender it would do the same thing. To be honest this is probably my third attempt as on previous attempts i got the plastic too hot and the end results were awful. Anyway after a bit of fiddling with the file i fixed the roll cage to the deck:

(http://s14.postimage.org/6ku5uob19/SDC14824.jpg) (http://postimage.org/image/6ku5uob19/)

Ive also made an engine out of plasticard, the exhaust pipes are pen tubes:

(http://s16.postimage.org/pkrd5wl5d/SDC14825.jpg) (http://postimage.org/image/pkrd5wl5d/)

Ive also adapted the air filter into a lock nut to keep the deck down. I epoxied a nut inside a tooth paste tube cap then added 2 circles on the top and bottom of the cap to male an airfilter. Ive screwed an eye in to the bottom of the hull then a threaded bar with a hook on the end hooks into the eye comes up threw the centre of the engine. The air filter screws on top of that too hold the deck down securely:

(http://s13.postimage.org/n3gj1dz3n/SDC14827.jpg) (http://postimage.org/image/n3gj1dz3n/)

Title: Re: Water Jet experiment and Jet boat build
Post by: Netleyned on April 06, 2012, 04:49:11 PM
Very neat setup there Mike
When is the launch day?

Ned
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on April 06, 2012, 05:46:36 PM
god knows the kids are off school for easter and cant handle them all and sail the boats at the same time. I need to get the painting done but it wont be long till im finished now. Im not going to great lengths into the details on this build.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on April 08, 2012, 08:49:08 PM
right i reckon im about done, painted it up and made some numbers out of wheely bin stickers, ill need to make a grill for the water inlet to stop stuff going in the pump. I cant tell you when ill get it on the lake though i hope thursday.  :-))


(http://s13.postimage.org/c0wu614ub/SDC14839.jpg) (http://postimage.org/image/c0wu614ub/)

can anyone tell me if its totally necessary for my 2.4ghz antena wire to be stuck out the top of the boat?
Title: Re: Water Jet experiment and Jet boat build
Post by: Danny on April 08, 2012, 10:40:40 PM
Mike - as long as there is no metal or carbon fibre surrounding the aerial, it will work fine within the boat.  2.4GHz goes straight through grp or wood.
Cheers
Danny
Title: Re: Water Jet experiment and Jet boat build
Post by: gwa84the2nd on April 08, 2012, 10:45:46 PM
i run mine onn my ic boats inside the radio box so you shouldent have a problem runing with the airial below deck  :-))
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on April 08, 2012, 11:08:38 PM
good ill do that :-))
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on April 13, 2012, 10:21:37 AM
so no test run thursday :-)
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on April 13, 2012, 11:40:37 AM
yes but it wasnt good. I started off the test run with a partially charged testing lipo, everything seemed ok, went straight as an arrow too. Thought right lets give it some welly then so i put in a fresh fully charged lipo and it launched like a scolded cat, came to some ripples in the lake about 20ft out and got it airbourne, on landing the boat cut out completely. I sent me rescue boat after it to recover it and discovered the 25a fuse had popped, bath testing showed that the continuous running was around 7 amps so i thought 25 was plenty of head room especially will the esc rated at 80amp continuous. Tried a new 30a fuse in it when i got home, forgot to take spare with me didnt I, power came back on servo and radio works but motor doesnt run. I reckon that when the boat went airborne the motor overreved when it went dry, then on contact with the lake the flooding of water in the pump loaded the motor again, spiked the current and popped the fuse. i need to purchase a better esc before i take it out again. I new it was risky buying the cheap oriental esc so i made sure i went over the top with its handling capacity, looks like it didnt work.  {:-{
Title: Re: Water Jet experiment and Jet boat build
Post by: hopeitfloats on April 13, 2012, 11:44:22 AM
darn. does the motor turn. just a silly thought that one of the blades might have come off the impellor and jammed.  good to hear it is a runner though.
Title: Re: Water Jet experiment and Jet boat build
Post by: TailUK on April 13, 2012, 12:24:43 PM
So plenty of "ooomph" then?  I've been watching the thread with interest as I think it could be used to power a model I have in mind.  My thought is to use two pumps, one left hand and one right hand, to counteract the torque problem. I'd pump into a chamber and use small nozzles off that.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on April 13, 2012, 12:53:19 PM
plenty of oomph, scale speed maybe a tad over, better tooling and more maths involved could see it perform much more efficiently but thats over my head. When i ran the boat their wasnt a torque problem, or at least not one i noticed. like i said it went straight, what i thought was torque making it steer was actually because the jet of water was exiting sqaure to the transom. The steering nozzle corrected that. Ideally two pumps counter rotating would eliminate any kind of gyroscopic precession as ive been informed its called.
Title: Re: Water Jet experiment and Jet boat build
Post by: Krishna on April 17, 2012, 10:03:29 PM
great craft.. :-))
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on April 19, 2012, 10:21:49 PM
The other day i was reading about timing and pwm settings for speed controllers. Thought hmm i wonder. On intial set up i programmed the esc so that the timing was 30deg and the pwm was 16khz. thats what the intructions said for driving outrunners. Took its word for it and set it like that. Of course on the original trial, it popped the fuse. After a bit of research I changed the timing to 15 deg with 8khz pwm and installed a slightly higer 30a fuse.

Managed to get a 3 minute run today, until it made a horrible shuddering grinding sounding and stopped again. Brought the boat back smoke was pooring out of the hatch compartment, Im not sure if i had fried the esc, the motor or both, they both stank pretty bad. The impeller was fine though so no jamming had occured.

the motor is a 2212-06 28a 2200kv with a 28mm dia case turning a 5 balde 33mm dia impeller:

(http://s17.postimage.org/phcc8uz0r/SDC14962.jpg) (http://postimage.org/image/phcc8uz0r/)

i thought this motor would easily have enough torque to spin this impeller but it seems its drawing over the max rated current. There may be some  binding in the prop tube i made but i can easily sort that. Ive actually busted the original motor mount trying to get this out so ill need to make another anyway. I need to get the amps down and i reckon either a lower kv motor or a larger diameter one. With the motor as it is the rpm slows down when the pump starts to move water, if i get a lower kv it will obviosuly have less rpm per volt but im hoping the additonal torque of the lower kv motor will make up the differences in loaded speed between the 2 motors. back to the drawing board then.
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on May 05, 2012, 10:11:50 PM
its been a long time since Ive done an update, i haven't really had a lot to say because the progress has been backwards and forwards. 3 motors and 2 esc's later Ive seem to have got some kind of success that doesn't result in smoke :embarrassed:. Ive now got running a 1900kv 2830 outrunner on 3s spinning a reduced diameter 26mm impeller with lower profile blades. Anyway enough waffling:

http://www.youtube.com/watch?v=o3ULmAkzpgw

I must apologise for the quality of the video, i was on my own and had to put the camera down and sail the boat in shot. There are some leaks between the motor and the pump casing which ill address later once I'm happy with the motor.

 Its actually surprised me how much power is required to run a centrifugal pump as a method of thrust. I was hoping that the rule of thumb for matching props to motors would be transferable to pump impellers but it seems not, the diameter of the outrunner needs to be larger than the impeller.  The boat was initially pulling 25 to 30 amps on 3s with the old impeller and requiring nearly 340 watts of power. Its a little less now but still around the 300w range, its nowhere near as efficient as a propeller. I hope that the extra torque of a 3530 1700kv Ive got coming will overcome this and hopefully I'll be able to up the impeller diameter again.
Title: Re: Water Jet experiment and Jet boat build
Post by: gwa84the2nd on May 06, 2012, 03:02:23 AM
looking good tho matching a camparable sized conventional jet boat for perfomance and manuvarability and concept proven i shall say a pat on the back well deserved  :-))
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on May 06, 2012, 02:44:24 PM
thanks :-))
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on May 11, 2012, 05:07:38 PM
more vids:

http://www.youtube.com/watch?v=bidTCN3fVPQ&feature=youtu.be

http://www.youtube.com/watch?v=0zo6ni_2pCI&feature=channel&list=UL

Title: Re: Water Jet experiment and Jet boat build
Post by: Netleyned on May 11, 2012, 05:14:24 PM
That looks good Mike
Like a waterborne ferret down a rabbit hole.
Plenty of thrust there boyo  :-)) :-))

Ned
Title: Re: Water Jet experiment and Jet boat build
Post by: Mad_Mike on May 17, 2012, 11:57:21 PM
Im more than satisfied with the thrust i must admit and has turned out better than id hoped. As it was in the vid I could only run the boat for about a minute before the motor started to overheat. I received my 3530 1700kv outrunner the other day and installed it. You can see how it is clearly larger than the older 28mm ones. Im hoping that the increased torque will be sufficient to drive the pump without the motor straining. It better work this time because 4 motors later the build cost has gone way over budget <*<:

 (http://s16.postimage.org/4g33jfkm9/042.jpg) (http://postimage.org/image/4g33jfkm9/)