# a boat from foam-fiberglass laminate panels

Discussion in 'Boat Design' started by TacoFace, May 29, 2021.

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### TacoFaceJunior Member

Hello all. I am entirely new here, looking for help figuring out some concepts.

I have access to trailer loads of lovely foam/fiberglass laminate panels. Just under 2" thick, with a shy 1/16" fiberglass on both sides. Very strong and takes glue well, even edge-to-edge. I made a simple flat-bottom rowboat that works great, but want to make a better hull design. I'm trying to figure out the concept of approximating curves with my flat panels without excessive cutting.

I'm thinking of the parabolic grids for hull design. I'd cut panels to correspond with each part of the grid, split the angle of the cut so both edge surfaces are the same thickness, glue and clamp. I'll glass over the seams if I have to, but so far the glue holds great on it's own.

Is there a CAD program that will approximate a curved hull into faces, and calculate the angles of the cuts?

I know this will work geometrically, but calculating three or four compound miter cuts for each piece would be a nightmare to design. Should be a simple job for a computer program though...

Also, what are the hydrodynamics going to be on a curved hull that is broken up into faces with hard angles? Is it just going to be approximately less streamlined, or is something weirder going to happen?

These panels don't have any bend to them, and I'm trying to keep the number of cuts to a minimum.

How would you design a hull if you weren't allowed to use real curves?

I don't have a particular kind of boat in mind yet, but I'd be starting with something like a rowboat or tiny sailboat. -Mostly I just want to know if this concept makes sense.

Thanks in advance! Any input is appreciated!

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### DogCavalrySenior Member

You're pretty much limited to very low speed barge type craft. Like a big slow houseboat. However, those can be very useful craft.

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### Mr EfficiencySenior Member

What is the foam, polystyrene or polyurethane ?

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### Squidly-DiddlySenior Member

any common CAD like Solidworks or Autodesk Inventor will do a good job at giving you exact dimensions applying flat sheets over a curved surface (dimensions on both sides of panels, angles, etc).

You can get Student Editions for both which are full featured just can't Export to fancy CAM machines and both have good online communities where Power Users compete for clout to answer your questions.

But I gotta sorta agree with Dog. Maybe two or three hulled pontoon boat of flat material but pointy ends.

OR....use your material sorta like flat plywood cross frames you see in boats and apply curvable thin plywood over that.

OR...laminate it together to build up solid foam shape (sorta boat shaped with inside sorta hollow) and shape from there then a layer of glass once you got the shape smoothed out.

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### DejaySenior Newbie

Look into developable surfaces. These are shapes you can bend out of a sheet of paper or sheet of metal without resorting to "compound curvature" (lens or spherical) so they don't require the surface to stretch of compress. They can be thought of as ruled surfaces where you can pass a ruler along the whole surface of the hull.

This carolina dory would be an example of a flat bottom boat that is easy to build with developable surfaces. But for displacement speeds you'd probably want something with a canoe stern as well. Your foam boards will be stiff but not very tough so I don't think a planing hull shape is a good idea.

Maybe with your 1.5mm fiberglass on boat sides this idea could work, but I'm a novice too so please don't take this as expert advice:
I would try cutting kerfs similar to plywood into one side so the outer fiberglass surface stays intact, then fill the cuts with thickened epoxy when gluing them in place. Then fiberglass over the inside. This should be pretty stiff but your foam still won't be very tough and could easily get damaged.
Calculating the cuts would be something like taking length of outer curve minus the length of the inner length divided by number of cuts.

PS: Obviously a boat like this should only be used in safe waters where you can swim to shore but at least even if your boat swamps or crumbles into pieces it would float enough to give you some safety.

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### upchurchmrSenior Member

What is the foam? This is critical.
If it is Styrofoam then just throw it away.
That's a little excessive, but Styrofoam is virtually worthless in load bearing structure.

How is the glass coating made? Is it actual cloth with resin (epoxy or polyester or "other") or chopped fiber or something else.

How thick are the panels? Do they have formica or cloth coverings?

If these are premade panels for office separators, then sell them and make a real boat from boat building materials.

Don't kerf the inside glass.
Just take the inside glass off the panel, bend the one sided glass/ foam to shape, then glass the inside while in place.
That way you don't have useless kerfed inside glass being carried along giving excess weight and holding the panel into flat segments, instead of a nice even curve.

You are getting ready to spend a lot of money and time for something that will be worthless when you want to sell or when you are done with it.

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### TacoFaceJunior Member

Thanks for all the replies. It definitely isn't styrofoam. The panels are cutoffs from an industrial door manufacturer. 2" thick expanded foam sandwiched between fiberglass. I definitely don't want to glue a bunch of garbage together. I've made a few things out of these already and they are very tough. ...have yet to see how it stands up to water long term.

I'll have to get some pictures together for you all. This stuff is not going to bend, even into developable surfaces. It's dead rigid. Imagine you were using 2-inch thick plywood. The only "curve" is going to be facets like a cut diamond or something.

I might well be stuck with flat-bottom barge-houseboat stuff.

I'll try to get some pictures up tomorrow.

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### fallguySenior Member

Please pay attention to @upchurchmr questions. Not much else matters, if you can't answer them, then a boat build is unwise.

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### TacoFaceJunior Member

Copy, yes, I don't know what kind of fiberglass it is. I don't think it's cloth/resin, guessing chopped fiber?

They are not styrofoam office panel dividers. Not covered in cloth. They are cutoffs from industrial exterior door manufacturing.

I can suspend a 5-foot sheet by the ends and stand on the middle with no visible deflection. I'm 300 pounds.

My main concern about the material is that the glass will de-lam from the foam, but the joints are all epoxied and can take a beating.

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### Mr EfficiencySenior Member

Sounds like Polyurethane. It may even be "hard" PU foam (4lbs/cu ft). Did you say 5 feet panels ? That is pretty limiting. What are these joints you speak of ?

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### TacoFaceJunior Member

Closer to 11 pounds per cubic foot. At 2" thick we're talking about two pounds per square foot.

I'll get a spec sheet next time I pick some up. Pictures tomorrow.

I get various size cutoffs, but the large ones, the good ones is a standard cutout at 64x22"

I can glue edge to edge and stand on the joint It's really crazy strong stuff.

For everyone's piece of mind, I'm only building a rowboat / kayak / day-use kind of thing. Not going to be sailing to Madagascar in a boat made out of styrofoam.

This week I'll get proper specs for the stuff.

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### TacoFaceJunior Member

Don't know if this picture helps, but this is some pieces I cut to make an ice-chest. I'd feel safe going down a whitewater river in this ice chest, if it were larger.

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### TacoFaceJunior Member

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### TacoFaceJunior Member

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### Mr EfficiencySenior Member

certainly suitable for making some iceboxes

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