P1 Puma RIB racing-scratch building

Well guys the maiden sail was successful and I am overall satisfied. However, I think that there is a lot of work to do with the set up of boat and there was also an unlucky moment... ...
Let's synopsize the most important moments of today's rc sailing.
1. I really enjoyed the looks of the boat.


2. I am very satisfied with the top speed 44 km/h with only 75%-80% of the throttle because of the very bad spot, as you see in the video, the wavy water and the instability of the hull in high rpms due to propeller torque. I need flaps or turn fins? Any other recommendations guys?


3. The outboard and and the watercooling system worked perfectly. Especially the outboard seems to work smoothly transmitting the power of the motor flawlessly...

4. As I said the spot was terrible (we didn't go to the standard location due to a fisherman) and a wood hurted the hull


5. The videos do not show the big picture of the overall sailing behavior but they give you an idea.




Any recommendations on the set up from the experts are more than welcome

 

First of all, congratulations with this maiden!
Greece is one of my favorite holiday destinations, however I would not book this location. This is not the right place to test a high-speed mono-hull!

She can shoot herself out of the drink with ease. Overpowered for sure!
Knowing there is power in abundance is always a good start!

A mono-hull with a deep-Vee often needs trim-tabs to make here run better.

I would first look for a windless day and more room to slowly increase speed, and sail in straight lines and trottle back for the turns.
What I learned from my jet-boat (being a deep-Vee too) is that vertical trim made here from a total pain into a winner.
Of course prop-walk is absent with a jet, but so is serious speed

I see your boat struggling for a waveless stretch of water in your videos, I am confident you will be able to reach probably much higher speeds. She did not get the chance to run a decent distance.

First see if you can get her handle as you like by adjusting the outboard height and angle.
You can always add trim-tabs later!

 

Thanks a lot Michael... This is what I first thought myself, you are right.. .
I also thought of constructing a new mounting plate for the outboard so as to be able to mount the outboard somewhat (1 - 3 mm) to the right to offset the prop torque.
I forgot to mention that the hull leans to the right at high rpms.... Yes, I believe that she has much more to give in terms of speed
Regarding the location, this is the nearest lake to my house and we usually go to another spot few meters away much more suitable for rc boats. Unfortunately today a fisherman had taken the place...

 

The flex shaft is in perfect condition...


I use this well proven spray (with this evil number !!!! ) for maintenance in the outboard and the watercooling system.

 

Congrats Dim! For a maiden run it is not bad! But the lake is far from ideal, with al those weeds. You cannot really run a speedboat there

From what I see, the outboard should be tilted a little downwards, to reduce the bow lift and the jumping. Maybe the lipo could move more forwards, but only change one item each time, to see the difference.

If the hull tends to lean on the right side, you could try a smaller prop, or maybe trim tabs. I have not much mono hull experience though, so I cannot advice accurately.

I agree with UnusualRC: try to run at a better spot, where you can hit the throttle and run the boat from left to right, so you can see the hull behavior.

Great result on the outboard and already you got 44km/h with short bursts of throttle! I guess 60-70 km/h could be reached quite easily.

 

Thank you Jan for the advices they are very helpful !
Given that I had to check both the outboard and the hull, yes it is not bad for a maiden.
Sure a better spot is essential to test the boat properly, you are both right.
60 - 70 km/h is my goal for this hull
I would be super happy with this speed.
Also the sss motor seems to produce a lot of power.

 

New top speed record with my Penarib: 54 km/h


Still no full throttle a lot of stability issues.
Detailed sail report and videos will follow:

 

Will be interesting to see what causes the instability.
Luckily most deep-vee's can run stable just by the correct trim. And you can always play with trim taps if trimming the outboard and CoG does not give enough improvement.

It is fast for sure!

 

Sailing report #2:
Let's start with the changes I made with the set up to offset the propeller torque: (a) I moved the battery forward and to the left (b) I also moved the outboard to the right after trimming the mounting plate.




Regarding the height and the trimming of the outboard you can get an idea from the following picture:



Now regarding the sailing itself as you will see in the video below the boat is very jumpy and instable at high rpms. I tried even more trimming but then the boat tended to tip over more easily. I also reduced the height of the outboard without any significant result.



I will proceed with some (or all ) of the following changes in the set up:
a) move the battery even more towards the bow, b) use smaller (35mm instead of 36mm) propeller c) add some weight to the kneel to lower the center of gravity d) use trimm tabs e) replace the horizontal plate of the outboard with a wider one. I ve already ordered the following very nice trim tabs:


The outboard seems to work perfectly and I feel that it has much more to give in terms of speed.

 

It looks there is a crazy amount of power available.

First I thought it runs like a Mercedes (F1): porpoising!
This is the fact for sure, the propeller cannot get enough traction in the water.

This must be solvable with trim for sure!

One tip: always change a single (1) parameter at the time.
This is time consuming.
However if you change more than one at the same time, you will never be able to tell why it runs better or worse than before.

Another tip: write the steps down (or record it on camera).
Been there, done that
Costed me almost halve a year to make the jet-boat run well.
I am confident you will find the solution much sooner.

Nice pond by the way!

 

I think the outboard is working like a hydrofoil its ride on his back moving weight foward make a instabil ride. You can move the outboard up to the point the prop centerline is even with the bottum off the hull or higher In a real boat the cavitatie plate is out off the water at full speed if it is not you can get bouncing and you Go not so fast it helps only pull away with a start. I have a hydrofoil on my real boat and its helping only to pull a wakeboarder easy out off the water. Try to remove the cavitati plate only with water pick up mayby thats helping. Good luck

 

Thank you guys for your tips. I believe that sooner or later I ll find the optimum set up... This is part of the hobby.
Yes Michael it is a very nice pond up to the mountain Parnitha near Athens and close to my home (10 minutes by car). Unfortunately a large portion of the wild forest there was burned down by a wildfire last summer.

 

Hahaha you are absolutely right !
I just read about porpoising and the whole story about the f1 cars, quite interesting.
Nevertheless, I read that in boating the solution is the right combination of weight distribution, tilting and trimming just as you have suggested guys.

 

Porpoising comes from the boating world. F1 has adopted the term
Many RC and real scale jet-boats have issues with this due to the different location of the "push" point.
On a propeller driven boat this point is the center of the propeller.
With a jet-boat this point is always above the waterline. Most hulls are not designed for that, thus need adjustments like trim taps to stop the hopping like a "bruinvis"!

 

Great spot and now it's much more clear to see the hull performance. From what I can see, you need a couple degrees down angle on the outboard. If you push the throttle, the boat almost jumps out of the water.
I have similar behavior on my Speedliner Corsair. The motor is down trimmed quite a lot.

Trim tabs might help, but the root cause is not the lack of trim tabs, I'm pretty sure

Once the hull is more flat on the water, it will be really fast with nice cornering abilities. It looks really promising already and the power is there!

 

I agree on that Jan for sure.
What about the height of the outboard?

The outboard seems powerful, yes. Do you think that the outboard is powerful enough for a full sized 100% T800 cozy?
Note that the penarib weighs 2,670 grams with a 4s 4500 mah.

 

The height of the prop axle seems level with the bottom of the hull. That should basically be fine to start with. Maybe a little higher after fine-tuning. If you angle down, the prop will sit lower again. I would raise the prop axle to be level with the hull bottom again.

Here's a photo of the angle I'm running on my 152VO Speedliner. It is a flatbottom, so different hull. But just for referene; some hulls need quite a lot of down trim to run well!



Regarding the outboard behind a Cozy T800, it could work. It would definitely move, but my feeling is it is on the small side. Some guys, like Alex on his WSB Tunnel, even run 40 size motors.
You already have the motor. Just build a T800 and you will find out

 

Great looking boat now, and very fast, look forward to you getting it to run well. You deserve it.

 

Oh thanks Jan for the photo!
This is some serious trimming. Let's see what angle will be the optimum for the Penarib hull.

 

Oh thank you very much for your kind words @Returntohome! I hope I manage to get some nice sailing but I enjoy the process anyway.