Carbon Fibre - 'Flag Wrapping'

Has anyone ever come across or even used this technique?
If I understand correctly then a foam core can be made (using common modelling/Urethane foam), and then carbon fibre can be laminated/wrapped around the core in layers, using an epoxy resin to bond and harden them…??
If anyone has any experience of this or knows anything about it could you say?!?


This is a most common procedure to add stiffness to a few layers of carbon fibre.

I’ve fabricated a lot of composites over the years but haven’t got a clue about the term “flag wrapping”; unless it would be a description of wrapping something around a mandrel … maybe to make a hollow composite tube.

But check out these sites, especially number 2:



  3. Composite Materials | Aircraft Spruce

  4. Composites | Aircraft Spruce


Spend some time reading this stuff. The WestSystem website is a valuable tool. Spend time there and check out the “Using West System Epoxy”, “Projects” sections, and subscribe to their publication “Epoxyworks”.

You’ll also want to check out the process known as Vacuum Bagging, it’s essential to good composite construction.

Fantastic - cheers!
Yeah it’s just one term I’d heard used. Basically I’m looking at using a sculpted Polyurethane Foam core around which the carbon/glass fibre is layered-up…as described in the second link, to build up a monocoque bike frame. It’s been done before by quite a few people, but just after all the reading I can get my hands on before embarking on it.

Cheers for the list of links - most appreciated and some valuable reading in there.


Here’s something to think about scruffy … if you use polySTYRENE foam and EPOXY resins you can simply rinse out your foam"pattern" using acetone; it saves a lot of work. But , if you use polyESTER (traditional “fibreglas resin”) with PS foam it will melt the styrene foam BEFORE your lay-up cures, and you will, most certainly, be back to square one.

So Remember:

PolyURETHANE foams work with polyester resins.
PolySTYRENE foams works with epoxy resings.

Here’s another website that I REALLY like:

check out the “Forums” > “Construction” > “Boatbuilding” and “Materials” forums.


Cheers Lew,

Not really bothered about melting away the foam afterwards. Examples of bike building i’ve seen using this technique have just left the core in saying it gives some (obviosuly very little) added protection should the outer skin be punctured.

Is there any reason not to use a Polyurethane foam core with epoxy resins?? It seems that these are more easily accessible (esp. epoxy…)

Trying to keep this as simples as possible!

Use polyURETHANE with epoxy to your heart’s content.

But make sure you use some form of dust mask/repirator when you sand it. It goes airborne instantly and into your lungs a nanosecond after that. If you’re going to do a lot of this you may want to invest in a painter’s type cartridge respirator with an organic chemical filter. You’ll get light-headed pretty fast. Latex rubber gloves are a “Need To” with both polyesters and epoxies.

It’s also not a good idea to hot-wire cut it unless you’ve got real good ventilation … nasty fumes.

For sure spend some time nosing around Boatdesign. All this process information is buried there in the various forums.

Have fun. . … .