TornadoCAN99

My BBS kits is being prep'd.

Any tips or things I should watch out for during the home-build I'll be doing? I went through their video's once so far. I'm a bit concenred of the Balsa butt joints...my boat buidling experience says anytime you've got wood, esp. balsa, any water intrusion will rot it out. Also, the bamboo loads the balsa in compression...isn't it likely to permanetly compress the balsa over time?
I plan to swap over nearly all components from my Carbon Belt Drive, 11-spd Afline IGH and hydraulic disc brakes. If I like the setup I'll buy new components so that I have two complete bikes ultimately...potentially to sell one later.

Canaboo

I'd be watching everything and going above and beyond any prep work they recommend... The bamboo shouldn't compress the balsa since the carbon/glass lug will lock the bamboo from moving into the balsa.
The lack of proper sealing of the bamboo in their method is a real concern to me.
If you want to seal any of the bamboo, make sure it's the inside of the seat tube. Water getting down in there and sitting on that balsa is a recipe for rot in a high stress area.
Not sure what glue is being recommended for tacking but do yourself a favor and use proper glue.
You may also run into clearance trouble depending on your front 'belt ring' size.

TiBikeGuy

Here are pics of a bamboo bike made by students in Singapore. This is prototype frame #3. The parts are mismatched because most are donated parts or purchased 2nd hand parts taken out from other bikes.

TornadoCAN99

That is a really nice looking bikje despite mismatch! I love the burnished look of the bamboo and the look of the joints. Did you varnish the frame?

Just watch out for PANDAS!

TornadoCAN99

The video show them using JB Weld (5 min thickened epoxy) as the tacking glue. I'd prefer to use proper West System epoxy with a thickener. But it seems the tack up stuff isn't really supposed to hold loads after the carbon layup, correct?

One thing I noted they did not do which is definately not best practise in epoxy work...according to the Gugeon Brothers West System instructional guides, epoxy produces an amine compound during curing and this coats the surface as an "Amine Blush". You should never sand/file a freshly cured surface before removing this material...otherwise you just embed it into the sanded surface and it makes for a poor secondary bonding surface. Can lead to delamination of subsequent layers. The blush is water soluble so a damp rag or light spray & wipe will do.

What are people finishing their frames with if anything? I will ride in wet weather often. Like the idea of polyurethane but does it bond well enough to bamboo?

Canaboo

You would be better off using all West if you can get it. G5 for tacking and 610 for the dropouts. The tacking may not be supposed to hold loads but the demonstrated fail points with their technique is the juncture between bamboo and balsa. Just not enough correct fiber orientation in those spots.
I really don't think their process speeds things up over just mitering, particularly if you have some aptitude with tools. Mitering is a far more secure building method.
You shouldn't have to sand between lamination layers..... no reason you can't do all the layers in one go.
It seems that the BBS goes on the premise that the natural silica layer of bamboo is a good waterproof coating but it really isn't after the plant is cut. Plus every little nick in it is a wick for moisture to get in. Bamboo is very hygroscopic.
I have heard of them using Tung Oil but Tung oil is not very waterproof.
You would be wise to coat the frame more thoroughly if riding in wet weather. In order to do that you have to sand the shine off the outer layer or nothing will stick to it.
Also keep in mind that Epoxy is very sensitive to UV rays so if you don't protect them you can be sure your lugs are on borrowed time if the bike will routinely be in strong sunlight. The Epoxy will rapidly take on a muddy appearance.

cameronbrown

I used epoxy with thickener for tacking and when cured the tacked frame was extremely strong on it's own: https://www.cameronbrown.ca/blog/2013...-wrapin-it-up/

TornadoCAN99

Nice work there!
I'm 4 days into my build. Carbon wrapping completed. Sanding & filing now.
I still haven't decided on a finish. I like the look of your finish. Can you specify what you used and how you prep'd the bamboo outer surface?Had been considering a standard marine spar polyU...but worried it will flake off the bamboo surface due to poor adhesion.

Details on my progress here:
https://www.pbase.com/d30/bamboobike&page=1

Canaboo

Not bad for a solo effort. You'll probably want to sand and touch up with extra carbon rather than just filling voids with Epoxy. That is if you have any carbon left over.
You need to at least knock the shine off the skin of the bamboo if you want to have anything stick to it.
A nice natural finish is Lee Valley 'Varnish Oil" with wax on top of it. Requires maintenance but you don't have to worry about chipping or flaking.
You really should at least put a good UV resistant Poly or spar varnish on the carbon/epoxy. The 205 and 206 hardener based mixes go "muddy' very quickly in sunlight and that means your lugs are breaking down.

TornadoCAN99

Yes, I'm familiar with the UV effects on the West System epoxies...I have done lots of work on fiberglass boats over the years. I will be using polyU on at least the carbon lugs. I'll take a look at the Varnish Oil. I ride in lots of rain herei n Vancouver....any concerns for this stuff?

The only location I want to fill in is the underside of the BB...there is a void formed by the overlaps of carbon that just looks ugly...but the setup is pretty strong there. The fill it will just be fore cosmetics.