P1 Puma RIB racing-scratch building

[Dim L]

Hi to everyone. Since I am new to this forum, let me introduce my self. I am Dimitris, I am from Greece and I am into rc since I was kid (now 39). However, this the first time building a scratch model boat (along with Cozy F1 of Dirk Jan plans). Unfortunately this post is going to be in English since I do not speak Dutch. .

Well, this post is about building from scratch a Rigid Inflatable Boat (RIB) which are very popular here in Greece. I always wanted to build a RIB rc boat with an outboard. Searching in the net, I came across some "plans" of the P1 Puma Racing boat available at this page: http://www.p1ribs.com/.

Of course these are not proper plans but gives an idea of the shape of the hull and the sponsors (inflatable tubes) and the deadrise angle. I decided to take the risk and trying to build the boat using balsa, plywood and a certain amount of improvisation!!!
The real thing follows below:

As you can it is not a stepped hull so it was easier for me to replicate as close as possible the shape of the hull.

The length of the original hull is 7.5 meters so I decided to make 1/10 scale boat of 75 cm.

First, I resized the plans so that the length of the boat equals 75 cm and then I cut 3 pieces using 3mm plywood.
1. I cut the sponsors (marked with orange).
2. I cut the transom (marked with red)
3. I cut a stripe of about 1.5 - 2cm as shown with blue following as close as possible the drawing.
4. I put the pieces together to form the hull.

 

[Dirk Jan]

Nice project Dimitris. I am going to follow this one.
What is the setup you are planning? And what outboard leg?

 

[Dim L]

Thanks a lot Jan.
I want both scale look and speed. So the first candidate is the medium geared TFL outboard:

The motor is a 3660/2075KV SSS and the manufacturer proposes a120 amp speed control and 4s-6s battery and a propeller 3.7 / 1.5.
I think that a 150 amp sc and 4s battery is a safe choice for this engine.

I really love this outboard it is so nice.
However, I think that, for some reason, it is not used by the members of the forum (or more generally by modelists around the world).
(Smashing the gears? Not reliable in general? Too heavy? Cannot hold more power? Too expensive? Something else?)
I really want your opinion guys for this outboard.

A second set up is something similar to the one proposed by Dirk Jan in his new project Cosy F1 T800. The larger TFL leg with a 3674 1650 motor and 5s to 6s. This is for sure a faster choice but is not as scale as I want for this project.
The boat will be 75 cm with weight ranging between 800 to 1000 grams, hopefully.
Any other ideas?

 

[Dim L]

Update #1
Filling the sponsors with solid balsa wood and then sand them down to the required diameter (i.e. the plywood circles marked with color).

The hull with the full sized plans

Making the back of the sponsors

Bonus the speedboat of my 6 years old son

 

[Dirk Jan]

Nice build technique Dimitris. Your work shop looks good too [emoji106].
You could have used hard foam with a glass laminate around it as well.

Regarding the outboard; I have no experience with that unit. Only thing I know is that geared units cannot handle a hot setup and they require more maintenance. As I love speed, I prefer flex shafts and I take the less scale look for granted.

 

[Dim L]

Thank you Jan.
I prefered to use balsa because it is a little bit harder than the foam.
Yes you are probably right. Tfl.de also told me that these outboards do not like high power and rpms.
Another option would be the MHZ look alike outboard

Here the motor is inside the hull and a flex shaft 4.75mm comes through the engine.

It is an interesting solution where you can combine a strong motor with high rpms and absolutely scale look. (149 €).

 

[Dim L]

I was not satisfied with the building process. The hull was not as accurate as I wished and the solid balsa for the sponsors was too heavy. Thus, I decided to create my own plans, using the humble drawing option in ms excel. Drawing by hand in a graph paper was my second option.
First, I decided the hull in 9 parts to be able to draw 8 ribs as shown below:


and I made all necessary measurements : total width, height and the width of the tube for of

 

[Dim L]

Of the rib.
With these data on hand I draw in excel the ribs eg this is the transom:

Then I will follow the standard process of screwing the ribs upside down on a wooden template and start planking the bottom of the hull.

 

[Dim L]

Here are the plans for the 8 ribs in a clean form. I hope the hull comes out well now.

 

[Dirk Jan]

Drawing in Excel, wow never thought of that [emoji6].
Looking forward to the next steps.

By the way, Building 2 boats at the same time.. you must have or make a lot of spare time. Lucky you!

 

[Dim L]

Ecxel it s a new trend in boat designing... . Just kidding. Actually I d like to learn the CAD or the Fusion 360 that I saw here in the forum, but I have no time to invest learning it.
I save about 2 - 3 hours per day from commuting due to teleworking which helps a lot... plus I like to take breaks between the various projects... I haven't touched Cozy for a week.
Bytheway what is your opinion about the Fusion 360 Jan? Is it worth learning it?

 

[Dirk Jan]

I have no experience with Fusion 360 actually. I nowadays use AutoDesk Inventor. I use it for my work and therefore I have the chance to use it in my spare time as well, for my hobby. I actually learned quite a lot of 3D CAD techniques from drawing boats hobby wise!

Of course it is nice to learn 3D CAD, but it is just a tool. If you like to design and draw your own plans quite a bit, it is worth to learn it.

 

[Unusual RC]

Fusion 360 from Autodesk (like Inventor) is free to use for the hobby, and even for small enterprises! A lot of learning resources are free available online, like on YouTube.

As Dirk Jan says: it is a hobby on itself concerning the time you have to invest into it. Most modellers already have a time consuming hobby

I use 2D and mostly 3D Cad for over 25 years now, hard to imagine how it was when learning. Having been a 3D Cad trainer for years, I noticed my students still experienced quite some learning curve before you can design something like your RIB into Fusion, Inventor or any of the mainstream 3D Cad software out there.

Excel is great to create accurate 2D curvature. Airfoils for model airplanes are often plotted with excel.
That said, most 3D Cad software has MS Excel integrated (OLE), or similar functionality build in.

 

[Dim L]

Wow!! thank you so much for your detailed reply. Let's say that excel is a good starting point to get into rc model drawing!!!

 

[Unusual RC]

Let's say that excel is a good starting point to get into rc model drawing!!!

Not the most common starting point for sure, but less unusual as most might think

 

[Dim L]

Bedankt Unsual RC!

 

[Dim L]

I decided to learn Fusion 360 (free version) and make my own plans for the Puma RIB. I have made some progress and here are some results:

Of course I have still a lot to learn in terms of techniques and tips but I really enjoyed it. It was really fun and you gain a lot in terms of accuracy of the hull
I use the Matlab in my work for programming algorithmic computations and probably it helped me a lot since I also produce 3D graphs.
Thank you guys for the discussions, you helped me a lot to discover new things in rc building.
Any tips - suggestions are more than welcome!

 

[Unusual RC]

You are making some progress indeed!
Yes, the power of 3D is a big gain in precision. You can make a hull shape first, and then decide where you want to position your ribs (slices in 2D from the 3D shape)

If you master Matlab (used it many years ago for among other to calculate heat dissipation) 3D Cad might not be such a big leap to master for you!

That said, my appreciation for rc boaters who build hulls from scratch with only pen, rulers and paper did grow a lot the longer I use 3D Cad!

 

[Dim L]

This plan is not that close to the original but I like it better. Some pictures from the afternoon session...

I like it I think I'll keep it (with few modifications perhaps).
Now I have to learn how to slice it to get the ribs.
Youtube tutorials are really helpful.

 

[Dirk Jan]

Great progress! To make a hull with such curves is already quite advanced. Looking forward to the next step.