P1 Puma RIB racing-scratch building

Thanks a lot Jan. It is really fun designing your own hull.

 

The inflatable part of the hull has a different diameter from stern to bow.
You might try to loft it by using a sketch/spline as a guide.
Create 2D sketches of the circle along that path.
The more sketches, the more accuracy.
At the cost of more processing is needed

Do not forget to put the sketch planes on this spline perpendicular to the normal.
This often works by adding a centreline on the original spline, and give it a tangent relation.

Than create a plane perpendicular on it, exactly in the start point of the centerline.

3D can be addictive

 

You are right Unusual RC the diameter reduces a lot, even if racing ribs generally have smaller tubes on the front.
I had already started redrawing the hull in away similar to the one you describe above. Thank you very much!
Here are some plans.








My problem is that when I add more profiles to increase accuracy, lofting crashes (warning about geometry etc.) Any ideas????
And yes 3D is addictive. Probably I should go back to Cosy to clean my mind !!

 

Looks a lot better.
In the beginning you will redo a lot, part of the learning curve

Issues with the tube around the nose?
Often lofts go wrong when the shape intersects itself. When you make the radius so tight, that the profile cut into itself.

In reality not possible, but possible in 3D

 

Today is a day off in Greece (celebrating the "No day" at the WWII, resistance to Italian invasion) and I grabbed the opportunity for some designing.













I inspired from a racing RIB of a Greek company (TopLine):



The nose will be like the Bernico RIB:

 

You are progressing swiftly!

A little comment:
If you look at the bottom view of your boat, try to follow the curved lines (called rails in F360) from the stern to the bow.
You will see they are not that smoothly.
A few "dents" (places where the radius is smaller than average) can be seen, as if the rib you added to the wooden construction model was a bit too wide.

I never used F360.
What I do know from other related software is that you have advanced controls when making lofts, to make it more smooth.
And use guide curves to enforce "smoothness".

https://help.autodesk.com/view/fusion360/ENU/?guid=GUID-9310FE7D-9AD4-40B4-A51A-373DA43B7A4A

 

Wow thank you so much for the comment! I do know that weakness in the hull but I must correct it.

 

Love it ,looks super .
Nice drawing!

 

Thank you very much!!!! Few more adjustments and I think it will be ready.

 

I primarily design and recreate true scale hulls in SolidWorks.
You do not know how often I started all over again to get it right

Surface modeling (a solid is an automated sequence of creatung surfaces, which create a completely enclosed en welded surface body. This is then converted into a solid. All in one click) is the most difficult class of 3D modelling, so you start with the hardest learning curve

Often surface modeling gives better result than surface lofts. There are features to manually convert these surface models to solid bodies.

What I have seen from an experienced F360 engineer, there are nice surface tools available in this software.

 

Adding some smooth guide lines to help the loft and here is the final result:


The bottom of the hull is the smoothest so far.



Overall, I am satisfied with this design.
Thank you very much UnusualRC for your comments, they really helped me a lot.
I think it s time to get back to workshop to finish Cosy...

 

Well done!
Always go the extra mile

CAD is fun, but also a distraction from the workshop.

 

After a lot of changes this is the final design of my version of the the Puma Rib.













Some details of the hull ( I keep it small to keep down the costs):

Length: 63 cm,
Beam: 23 cm,
Deadrise angle at the transom: 26 degrees (ultra deep V),
Sponsors diameter: from 4 cm (transom) to 2 cm (at the bow),
Motor: Small TFL outboard,
Battery: 3s,
ESC: 70 A.
Estimated max speed: 40 km/h - 45 km/h (hopefully)

Construction - materials:
Ribs: 3mm plywood
Skin: 1 mm plywood.
Sponsors: hard foam and/or balsa strips,
Cowl: Carbon fiber (want to make a mold and then a make the cover from CF (like Cosy)),
I am planning to apply 50 gr glass fiber both at the inner and the outer surface of the hull to strengthen the hull.
Spray rails at the bottom of the hull (not shown in the plans) will be a challenge.
That is for now.

Thank you.

 

Nice design! The specs sound good as well. 45km/h speed is no issue at all. I think it will be a challenge to go slower on 3S .

Looking forward to the ribs structure.
1 note: the V-shape looks very deep indeed. I have not much experience with V-hulls, but maybe torque roll and/or stability might be an issue?
It also depends on the weight of course.

 

Thank you Jan.
You are right the V is ultra deep but is close to the real ones. The stability is an issue, it may need flaps at the transom. Because I want also to sail at the sea (with rough water even with out wind) i wanted a deep v hull. May reduce it to 22 degrees that is the minimum I have seen to the real racing ribs.

 

Reduced to 21.9 degrees. If it is unstable (highly possible) I will make flaps at the transom.

 

For those interested, here is a nice rc rib construction (also makes flaps at 2:45)

 

Wow, you made some progress with your CAD design skills!
Well done.
Looks very fast even standing still!

Deep V is the choice for rough waters.
My Recoil 26 has a dead-rise angle of 23°, and is known for its rough water performance.

The vessel is equipped from the factory with trim flaps or tabs.

I have no flaps anymore, and since it is water-jet powered I have no physical rudder. It is very prone to chine-walking at speed, which should be gone with flaps.

A huge water rudder will help for sure, so I would not worry. If it becomes an issue, flaps are a solution to try.


Now you have the 3D model laser cutting your wood is an option. At least make 2D sections on paper, and print scale 1 to 1!

My tip: add a ruler for scale on the paper, to check if your printer prints to scale.

 

Thank you unsualRC for your nice comments.
Unfortunately no 3D laser.
I print 2D 1 to 1 and then I measure with a ruler the dimensions to be sure that is indeed 1:1.
I have plenty of 3 mm plywood (dad's present for my name day ) and I wait for 0.8mm and 1mm plywood from Germany.
Believe it or not it is cheaper for me to order from Germany (including shipping costs) than from local stores!

 

If you have the local ability to send DXF 2D files to a laser cutting company, you could do that.
However printing on paper, and use that to cut-out wood yourself is already a big advantage of having designed your model in 3D!

Just add a line of 50mm (the longer the more accurate), and add an annotation (text) to it saying this is a 50mm reference.
If that is spot on, your printer is perfectly calibrated.
Most modern printers do print very accurate, if set to scale 100% or to true scale, depends on the type of printer and/or driver.