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[Backerther]

Hi all,
I have taken this model up in my short time conversion project for this summer.
This kit is a bit old and so tiny(18.5' OAL) which real one is powered by water jet and very fast capable of sailing over 40 knots/h.
I have never experienced to build this water jet system so far but interested a bit in this system though.
I am anxious about the size of this model as I do intend to sail it on our usual lake often come up on here, a nice sailing spot.!
It's tooo small for this lake, but I have dared to challenge it this time as I could not find any other adequate pla-model fast boat
kit than this one.
It's so surprising  to me that assembly instructions and other explanations on the box were written first in Japanese followed by English and Chinese in spite that this is a Chinese -made kit.!!!!!  So rare and first for me to see this kind of kit...


The package arrived as seen in the pics....I wonder how I should assemble this kit ..water jet or conventional type of propeller?
The last pic below is a Lindberg 1/20 Chris craft Constellation(30' long ) taken up in the last summer as the Rc conversion project, sailing on the Christmas day with a Santa of the last year.

[tica]

Nice 
If you haven't seen it there are a water jet kit for it on ebay https://www.ebay.com/itm/293050678011
Also this video by the designer of the kit. https://www.youtube.com/watch?app=desktop&v=lYAEIMIAuAs

Br   

Carsten

[Backerther]

tica,

Thank you so much for a quick comment on the water jet system and I have ever seen them before many times before
purchasing the model boat. It looks like easy to install in the CB90 kit.

[Backerther]

Well then, shall I start assembling the kit ?..looks easy simply to assemble the kit as it is, but I don't know whether or not
easy to convert it to RC capable one to sail on the large LAKE not on the pond,,,, Anyhow it is so small for the lake....18.5 inch long boat, worth challenging to convert to RCable boat for the lake ??...

Only one thing convenient for me is its instructions written in Japanese first, English and Chinese..Main target is Japanese..??

[Backerther]

I have just studied a general arrangement putting major components.... Geee !! A bit difficult to keep a good balance...
What shall I do ,,??     It's a small boat so that there is no big room to adjust the balance of the boat...Anyhow tiny !!
It's a challenging boat from the beginning !!...

[Backerther]

A water jet pump unit being delivered to me, I have epoxied it in place after intensive trial fit and some slight modifications.
Looks perfectly OK as it is originally designed for the proper use for this boat.

[Backerther]

I have been assembling this kit (including the jet pump unit) like a pla-model easiness currently.
The pics below are stages of fixing stern tubes and motors after intensive alignment adjustment to be able to get a calm and smooth rotation of impeller shafts.   This stage is sooo important to do and worth spending a lot of time for a successful sailing
on the water though the time will come some months later.... when I will smile or not about the result beside the sailing spot..??
The instruction manuals indicated that the motor mounts be fixed with only glue which I think so unreliable and unrealistic to do
for these positions, and so I screwed them on.


The motor is 180 class one which I think is Ok to get it run fast by 2S lipo 1500mAh to sail around 5 min through 7.

[MikeMcP]

even though it looks to be beautifully aligned, I wonder why you didn't use some sort of universal joint, just in case?

[Backerther]

Thanks for your comment and a question to the point.
There are 3 reasons to set this coupling temporarily as follows.
1) The coupling in the pics is ready-made one in the kit and I only set it to know how good the coupling and alignment will work.
2) In a sense, there is no need to use a universal coupling if it should be aligned perfectly.
3)I never intend to use this kit-furnished brass coupling nor universal-one finally as my favorite, calm, tough and secure type
   of coupling is disc coupling as in the pics.

[Backerther]

I made a pair of cooling coils for 180 class motors clumsily as in the pics....       
But they will work securely.!
This time, it was a bit difficult to form neatly due to strange shaped-can of the 180 class motor.  

[Backerther]

Getting back to the hull assembly, I bonded both halves of hull finally after checking the alignment of the two prop shafts
using 30 min. epoxy.  

[Circlip]

Probably won't make a lot of difference but motors overhung on mounting brackets don't look good.


 Regards  Ian

[Backerther]

Yes, indeed, but it does not matter at all for actual performance of this tiny boat.
It is rather advantageous with regard to the more important maintenance.
Perhaps you will know the reason in due course.

[Circlip]

I realise that it wold be difficult/impossible to fit your cooling coils if they weren't overhung but should the motors overheat in this application?


 Regards  Ian.

[Backerther]

I am so much surprised to know that you have soon realised my application of motor setting.!  
That's right, you hit my idea, Ian.....!
But, to tell the truth, the kit instructions itself indicated this style though....And I just followed it and admitted the style for
an easy maintenance and the cooling of the motor.
I suppose overheat will be taken place since the motors will be surely obliged to run always fast enough to generate powerful jet flow.   I just have come to feel that conventional style of propulsion using normal props might be possibly rather effective to run fast on the water...

Kiyo

[Backerther]

I set impeller shafts and disc couplings followed by the grease up in the stuffing tubes.
Everything was OK with a smooth rotation of the impellers with a 1.3 V battery test.
But I am anxious about the size of the impellers of only 10mm dia which are furnished in the water jet kit   .....!!!???

[Backerther]

And I set the control section temporarily and briefly after setting the drive system.

[Backerther]

These are modified RC operable thrust vectoring nozzles from the pla-model kit parts, made previously before getting  into
hull assembly.
They have sufficient amplitude for both sides and work very smoothly.