Low-cost experimental platform cat for inland waterways

[8Petros]

Greetings from Poland.

For 2024 I plan to build a small platform (3x6m) pontoon catamaran, being a far-fetched derivative of ferroconcrete constructions. Pontoons will be made of heavy-duty XPS (Extruded Polystyrene) foam panels,(such as SOPRA XPS 700 - Soprema United Kingdom https://www.soprema.co.uk/en/product/insulation/xps/sopra-xps-700), glued together and profiled with thermal wire cutter.
To improve impact and scratch resistance, I plan to laminate them with a plastic mesh and glue, normally used for facade finishing after putting thermal insulation on.
Finally I plan to paint pontoons with a ceramic or latex acrylic paint, providing hydrophobic coating.

Now, my question is, whether some Colleagues know similar constructions and would like to help me learn more about the prior art.
The boat will be built for inland waterways and will be a test platform for various propulsion systems and wheelchair-friendly solutions. Overall goal is to develop an amateur construction (will be published under open licence: CC-BY-SA) that can be built, maintained, and repaired with inexpensive tools and materials.

Your feedback will be appreciated.

 

[bajansailor]

Welcome to the Forum Petros.

How are you planning on building the platform which will connect the two hulls?

Re how the hulls will be 'laminated' - will the 'slices' be horizontal or vertical?

Do you have any initial sketches of your proposed design that you could post on here please?

 

[Rumars]

To improve impact and scratch resistance, I plan to laminate them with a plastic mesh and glue, normally used for facade finishing after putting thermal insulation on.
... inexpensive tools and materials

Please do me a favor, go to the hardware store and write down the price per cubic meter of XPS and PUR foam, price per square meter for plastic mesh and price per kilogram for the glue you plan to use.
Then go online and find the same prices for epoxy laminating resin, polyester laminating resin and 200-300gr/sqm plain fiberglass and CSM (or a combination fabric).

Write back how big the difference in zloty per square meter between plastic mesh+glue vs. epoxy+fiberglass and polyester+glass fabric+CSM. To get to the total cost you need a reasonable estimate of the surface area involved, when you have that compare the costs for XPS foam+plastic mesh+glue, XPS foam+epoxy+fiberglass and PUR foam+polyester+fiberglass+CSM.

 

[8Petros]

How are you planning on building the platform which will connect the two hulls

I am going to build a truss of aluminum sqare tubbes, using XYZ nodes (reference: manual for XYZ NODES http://www.n55.dk/MANUALS/XYZNODES/xyznodes.html)
The truss will be built and tested separately, later anchored to pontoons (exact method to be detemined).

Re how the hulls will be 'laminated' - will the 'slices' be horizontal or vertical

Considering the estimate size of pontoons (each side no more than 1 m wide) it is possible to lay the net lengthwise with overlaps at the edges. I am also considering enforcing edges with an angle protector (pictured).

Do you have any initial sketches of your proposed design that you could post on here please?

There is nothing special now to be sketched. Just an average DIY pontoon boat. Most development I am going to do hands-on, and document ex-post.

 

[8Petros]

Please do me a favor, go to the hardware store and write down the price per cubic meter of XPS and PUR foam, price per square meter for plastic mesh and price per kilogram for the glue you plan to use.
Then go online and find the same prices for epoxy laminating resin, polyester laminating resin and 200-300gr/sqm plain fiberglass and CSM (or a combination fabric).

Write back how big the difference in zloty per square meter between plastic mesh+glue vs. epoxy+fiberglass and polyester+glass fabric+CSM. To get to the total cost you need a reasonable estimate of the surface area involved, when you have that compare the costs for XPS foam+plastic mesh+glue, XPS foam+epoxy+fiberglass and PUR foam+polyester+fiberglass+CSM.

I certainly will, when the time comes, and will be happy to share my findings. For now, as I mentioned, I am in search for any similar projects already completed or abandoned. I do not believe I am the first person who had such an idea, so the reasonable way is to start from leaning on my predecessors' mistakes or successes.

 

[Rumars]

Define similar. Small XPS catamaran, yes plenty, using building mesh and glue as reinforcements, slim pickings. There's a reason for that of course, the laminate isn't there to provide "impact and scratch resistance".
A quick search here reveals:

Foam catamaran kayak https://www.boatdesign.net/threads/foam-catamaran-kayak.63162/

any tips for improving the lifespan of a fiberglass-over-Xps insulation foam boat? https://www.boatdesign.net/threads/any-tips-for-improving-the-lifespan-of-a-fiberglass-over-xps-insulation-foam-boat.65833/

We have plenty on using XPS as a core, feel free to explore the search results.

Other projects from the web:

Fly-Carpin: DIY Standamaran Stand Up Paddleboard Plans http://www.flycarpin.com/p/diy-standamaran-stand-up-paddleboard.html

Prototype Catamaran NAU https://www.sailwood.fr/realisations/prototype-catamaran-nau/ (different structure, it's a beach cat)

 

[8Petros]

Thank you for showing me direction. I will dig deeper into it.

 

[fallguy]

XPS is a relatively poor sheer and poor compressability product vs conventional marine foams.

I did use xps for foam amas and they have performed fine, but they do not really contact the bottom. Mine were encased in epoxy and 6 oz glass.

The trouble with xps is the hulls will bang the bottom and crush. So, xps is really only a former for glass.

A better way to go would be to make the bottom of the hulls from marine foam and then glue xps above it, if driving costs down is the wish.

Or all marine foam and polyester as Rumars seems to imply is probably cheaper still.

I did not convert the foam's ratings to english, but you want compressibility and shear over 100 psi or the hulls will crush/delam first time out.

 

[8Petros]

@fallguy,
I have no data on shear resistance, but FINNFOAM F-700 XPS is rate for 700 kPa comression, which translates to ~101 psi.
Thanks to @Rumars I go now through related conversations and there is a wealth of observations there I need to consider seriously. A lot of food for thought here, thank you all!
Luckily, I can work on superstructure, while testing various scale models of pontoons. It all depends on funding available, but I will certainly share the outcome here.

 

[fallguy]

@fallguy,
I have no data on shear resistance, but FINNFOAM F-700 XPS is rate for 700 kPa comression, which translates to ~101 psi.
Thanks to @Rumars I go now through related conversations and there is a wealth of observations there I need to consider seriously. A lot of food for thought here, thank you all!
Luckily, I can work on superstructure, while testing various scale models of pontoons. It all depends on funding available, but I will certainly share the outcome here.

you can also add a cabosil mud base to the bottom vee; this will help with bottom impacts

consider your weight hitting a bit of stone

200 pounds, pressing against a half inch bit of stone is 400 psi, so avoiding delam will be wise; unless you don't mind repairs

 

[waterbear]

Why not use plywood sheathed in fiberglass and epoxy? This is light, strong, durable and inexpensive. If the boat is not stored in the water you can use fiberglass tape and 100% acrylic porch paint.

As for the models, you can use something like freeship to model your boat. From that software you can optimize the area of curves, then export the model to michlet, which will show you just how much power you need. I did this once to build a rowboat, it was very easy and believe me when I say I don't know anything about modeling boats. I believe the modeling software was freeship but I'm not 100% sure. The drag software was definitely michlet, which is free academic software.

Hannu Vartiala has designed many simple plywood boats, and he modeled the drag of some of the later ones, you can see the graphs on his various designs, Eg this one sheet dugout canoe style boat:

The Dug | Free Boat Plans (hvartial.kapsi.fi)