P1 Puma RIB racing-scratch building

The project is stranded,but I'm printing a rib .
So maybe the motor is suitable for that..

 

The brass tube system is ready and fitted to the aluminum body (not perfectly though since more sanding - filing is needed).






I used the mini table disc saw to cut the 8mm aluminum using disc for metals and WD 40 spray. The cuts were surprisingly easy and straight.


And this is how the outboard looks right now.

 

I d like show you some progress with the outboard.
It was time to construct the rudder fin of the outboard using m3 stainless steel countersunk hex socket screws.
Step 1. Drilling holes progressively using 1.5 and 2.5 drills.


Step 2: creating screw threads


Step 3 : Countersinking




Step 4: cutting a 3mm wide rectangle to fit the rudder fin




Step 5 : cut the fin


Assemble...





Next step is to cut the leg in shape.

 

Found some time and I shaped the leg. It starts looking like an outboard...


Next step constructing the motor mount...

 

Drawing the motor mount early in the morning was fun...

 

A small step every day...

 

Cool

 

My daily update for the diy outboard . Cutting more pieces and adding some 3mm reinforces.








All pieces will be glued with epoxy for metals and will also be screwed together for maximum strength. The space around the brass tube will also be filled with epoxy for metals.

Then the leg will be filed and sanded so as to be as smooth as possible and hydrodynamic confused: this will be a tricky part because the aluminum is 8mm thick).

Next I am planning to paint the leg with epoxy primer and acrylic paint.

Until now I satisfied with construction process but it's too early yet.
Compared with the outboards out in the market, the diy will be much heavier and less hydrodynamic.
The pros of the diy are the small angle of the flex shaft and the ball bearings.

 

Those commercial outboards are die-cast!
They only need minor work to be finished.

You need some good files for metal to enlighten this work.
Nevertheless it is time consuming, but the reward once finished will be high for sure!
Your own outboard, one or a kind!

I have the same with the impellers I use in my jet. Not for sale, so die-cast is an option I have seen.
Thank god 3D metal printing is here, and relatively affortable. Still you see these rough layers...
I know someone who spends a whole day to make such an impeller shine like the ones you buy in the shop!

 

I think it's very nice Dimm ,lots of work but with such satisfaction to make it all by your selves.
Nice to see the progress working in on it.
Very curius how it wil perform.
Cheers ,Alex

 

You are right @Unusual RC. I may invest in one or two good metal files..
Thank you
!

 

Thank you Alex for your nice words !
I am very curious too. I am concerned about the water resistance due to the shape of the leg. Let's see...

 

It is a very long read, but some details might be interesting. Colin is a model boater (and RC airplane enthusiast) from the UK, who wanted to make a sports-boat with a scale large outboard from Yamaha.

A flex-shaft would be too off-scale, so he went for a geared version. Quite a "tour-the-force", but eventually he succeeded: https://www.rcgroups.com/forums/showthread.php?3683473-Rib-and-scratch-build-Outboard-1-6-scale

Most important for you: the issues he had with the hydrodynamics.

My opinion about your outboard: having read all this, I would not worry too much about it. If you make it look "hydrodynamicly sleek", it will work.

If top speed is your goal, you need to go another route.
Just see the latest movie of Colin's model. It is a big an heavy boat, it flies with this outboard!

 

Nice construction journey and fantastic outboard!!
I think that the problem with the greared outboard is that you must use too big (and strong) gears to handle the power of the motor.
Thus, the lower unit (the bullet with the gears) is unproportionally big compared to the whole outboard causing, possibly, too much water resistance.

 

Exactly!
And still the model, once he solved the ventilating of the propeller issue, the model really flies!
He is looking for a solution to measure the end speed. Pure estimation it is well above 30kmh, probably 40+

You can make a more smooth tail-piece, so this is an indication what you can expect

 

Hello guys, I made some progress the last two days with the outboard.
I redesigned the front piece of aluminum to be stronger as you can see in the plans below.


And some building photos:















None of the pieces have been filed or sanded yet. Next step is the motor plate.

The front piece of the outboard is too long, but it couldn't be different given the small angle of the shaft which makes the motor move at the very front.
Maybe I need a strong steering servo (which I have) and a reinforced mirror to be able handle the forces created by the length of the outboard.

 

Hello guys, I hope you are doing fine !
Finally found some time to continue my diy outboard.
I have changed the design (again ) and I decided to make extensive use of a 2mm carbon fiber plate, which I had available, to reduce weight. I also filed-sanded the leg to be as hydrodynamic as possible (I hope that the shape is visible in the photos below. Finally the extra aluminum parts are screwed and glued with metal epoxy which is also used as putty.

 

Nice work Dimm
I'm rebuilding a thundertigre 3.5 to electric now.
Getting all the gears out machining the leg .
Redirect the flex shaft with brass tubing.
Getting there,running quit smooth allready.

 

Wow very nice rebuilding Alex!
Also cool design for the outboard leg, quite different from what we usually see nowadays.
This gear setup seems a clever solution to reduce the flex shaft angle, but I guess it translates to more weight, friction and possibly problems with the gears to high rpm.
The mounting plate for the motor is 3D printed?
Very glad that you shared your work with us Alex. Looking forward for the next steps and of course the hull that you are planning to fit the outboard.

 

Indeed 3d printed Dimm.
And I just sold the graupner tunnel
And just when I sold it ,this lot came around....