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Wow, sorry it's taken me so long to do an update. It's been one thing after another stopping me doing the very last steps - first I didn't have a job and couldn't afford to work on it, then I had a job and had no time to work on it... but over the last couple of months I've been slowly acquiring the remaining parts and fitting them to the frame.

I'm a volunteer at the Broken Spoke Bike Co-op in Oxford which has meant that I've been able to use lots of pretty shop tools and do every bit of labour on the bike myself. I've also built the wheels: Shimano XT M756 hubs front and back (back respaced to 120mm with a solid axle and a Velosolo bolt on sprocket) laced to Halo Aerotrack rims with DT Swiss Competition spokes on the drive/disc sides and Revolutions on the other side. Saddle is a Brooks Team Pro Classic, handlebars are Profile OS Airwings with green and brown harlequin tape and twine. I've also fitted SKS Longboard mudguards.

The pedals were a bit of a faff - I wanted to use Wellgo QRD system pedals so I can swap between straps and clipless easily, but the M138 pedals I got originally were much too small for the Pedalbelt straps from Kickstarter. So after a failed experiment with the Wellgo V12 clones, I got hold of some normal C161 pedals which share the same axle as the M138s, and swapped them for the quick release ones. This is a cheaper way of making up for the fact that only a few QRD models are available in the UK (potential swappers, do note that the QRD axles are both right hand threaded, while the non-QRD axles have one left hand threaded).

Here is a terrible photo of the finished article:

Quick snap of the finished article by comatus1649, on Flickr

Naturally you might be wondering why I've not rushed out on it and taken some better photos. This is mostly because I had just finished a long session working on it and began to ride it home, when there was a bad noise, and the tyre began to rub on the chainstay. I took it home and examined it, and the results can be best experienced by flipping backwards and forwards between the two photos labelled 'wibble' and 'wobble' in my photostream. Almost immediately, the joints between the dropouts and the stays had failed - this had been my first time bonding stainless steel with epoxy, and it's not easy.

This presented a bit of a problem, as they were still very strongly attached by the stiff chainstays (the carbon 'lugs' were entirely intact; the dropouts had simply separated from the epoxy plugs inside). After a botched attempt to drill through the lug and pin the joint (stainless steel that has been work-hardened by milling is not only very hard to glue, but also very hard to drill...), I had no choice but to pull them out, a very, very stressful process. When they were out, I did what I should have done in the first place, keying them very aggressively for a strong bond:

Getting rough with the dropouts by comatus1649, on Flickr

They were then glued back into place with Marine JB Weld, more or less the strongest adhesive there is for this kind of application. Learn from my mistakes - smooth, hard stainless steel is extremely difficult to glue, and I shouldn't have made such a pig's ear of it in the first place. It's embarrassing to have such a critical failure documented for all to read but this thread isn't about making me look good ;) This is by far the hardest joint of the entire bike to get right, and it's a pretty important one.

The good news is that I'm pretty sure the bike is ready now, components and all. However, I'm in no great rush to get out on it because the salty roads are playing merry hell with my other bike and by the time I get home from work it's dark... there's also a terrible temptation to never try it in case it breaks again, in which case I've run out of (non-drastic) options and will have to get business cards printed with 'Novelty Bike-Shaped Ornament Maker' on them. This weekend I'm working but the next I'll have a chance to take it for a good test ride and get some decent photos, or that's the plan anyway...

Ben

Belated reply to Djangoberry: garden cane might be your best bet - it is actually generally bamboo, just really skinny stuff (harvested young, I assume). I won't be putting any cable stops on at the moment but will if I decide to run it singlespeed or even geared in future. I'd probably epoxy some normal braze-on cable stops onto the tube rather than using cane/bamboo because of the sizing issues.

VERY, VERY NEARLY FINISHED

So life has a way of filling up what you thought was free time, and I've not quite finished yet. But it's tantalisingly close, probably closer than you could easily tell from photos on the net and I'm going away tomorrow for three weeks, so here's the nearly finished product, and how I got there...

Polishing the CF, a dead end...
The CF was all in place and sealed, so I just had to get it to a finished state. I decided I would polish the epoxy - first I smoothed it off very lightly with wet 1200 grit wet and dry, and then I polished it with Autosol.

Polishing process by comatus1649, on Flickr

Autosol is a metal polish, but it's pretty good at this as well. I used loads of it, but it came out nicely, better than I had expected in fact:

Polished CF by comatus1649, on Flickr

And it looked better than that in really life. Unfortunately the finish didn't last very well - it seemed to be mostly down to the protective coat that Autosol deposits, and it dulled quite quickly. I also found that the bottom of the BB was getting scuffed pretty easy, so I decided that I wanted to put another protective coat on top. I was going to clear coat the epoxy, but decided not to because of its tendency to yellow, peel and generally be a bitch to get right in the first place. So as I was going to be using Gorilla Glue to seal the bamboo I decided to give that a go (cleaning off the polish residue and roughening it up with 150 grit first), and I was pretty pleased.

Sealing the bamboo

As mentioned before, bamboo has a naturally waxy finish which protects it for a while, but decays after about 6 months when it's dead, so I decided to take it all off (hell of a job) and replace it. I chose to use Gorilla Glue because I had it about, I knew it was very UV-resistant and tough, and because it's been used a little in bamboo rodmaking with good results. It is a bit finickety to use, and I'm not sure whether I'd be bothered with it again. I would probably just use spar varnish. However, it did come out well. You have to apply it very very thinly - I used a slice of washing up sponge to put it on very lightly. Put on too much, and this happens:

Ooops by comatus1649, on Flickr

The same foaming action that makes it great as a glue is not what you want for a finish. It's also worth adding that you don't wet the surface as you would if you were gluing it - the humidity in the air is enough to make it go off very slowly, leaving a nice smooth, glossy and hard finish.

Gorilla glue drying by comatus1649, on Flickr

Bottle bosses
To make this bike as much of a jack of all trades, I wanted to put bottle bosses on. I wish I had bought more, but ended up only putting enough for one cage on the downtube. I nearly just put one on the seat tube because I personally think that position has some advantages, but I didn't have a spare cage and bottle to test and I was worried about clearance with the sloping top tube. So one in a conventional location it is.

I also put two other bosses in strange locations for other purposes - one is on the back of the seat stay wishbone - this will provide a very nice neat way of mounting a rear rack. Drilling a hole here was incredibly difficult but now it's in it actually looks quite neat. The second odd one was on the back of the seat tube, at the point where the wheel will be closest to it. My rationale - I want to run full mudguards because life's too short not to. But I didn't put a chainstay bridge in for cosmetic and ease of wrapping reasons; this boss here will allow me to bolt the mudguard to the seat stay about 5 inches above its end (I'll have to drill another hole unless I have the mudguard ending early). I will have to see how this works out - the rear wheel clearances are relatively tight so it should work alright, and look nice and clean. Of course, it might be a terrible idea. But there have been 6 or 7 things I've done on this bike for the sake of experimental innovation so that I will know not to do them again (or potentially know they're a good idea).

The holes for the bottle bosses were drilled with gimlets first and then with an awl. I thought this would be the most gentle way but still cracked the sodding downtube very slightly. Take it very easy, boys and girls. I don't think the crack will spread but I will add a little more glue to seal it.

So this is where the frame is, essentially finished:

Finished (nearly) by comatus1649, on Flickr

When I get back, I'll finish it totally - one more go with 1200, then more Autosol, then beeswax or similar all over. That should give me the durable shiny finish I want... For now you'll have to be content with smartphone pics, but when I'm happy with it I'll get some proper arty ones. And then it's a matter of building it up (Christmas is on the way, thankfully...)!

Thanks for reading!
Ben

FINALLY FINISHING THE CARBON

After many weeks of doing the carbon fibre, I was getting pretty bored. I feel like this reader's wife and I are celebrating our diamond anniversary. It was nice to finally get it done. After all the carbon fabric is on, it's time to put on (at least) two thick coats of epoxy to create a surface that you can sand down to be fairly flat. As I said before you'll never get the finish you might see on a moulded CF bike, but you can get a pretty nice result. At this stage you'll start to see how all the little defects and imperfections don't look so obvious now it's all shiny, and how the weave of the carbon comes out. However, the surface will still be a bit rough:

2 thick coats of epoxy later... by comatus1649, on Flickr

You can also see little bubbles left in the resin. These can be greatly reduced by a combination of heating the two resin parts before mixing, stirring very gently (definitely transfer it into a second pot if you're being very gentle as you'll otherwise have a bit of unmixed resin at the bottom), hairdrying the resin in the pot (this shortens pot life a bit - a roller tray is best to stop it curing very quickly) and then again when it's on the bike. The foam brushes also tend to froth up the resin so you can either change to normal brushes, or as I did, just go very gently. Beware of cheapo paintbrushes which dispense bristles everywhere.

A note on masking techniques - wrap loads of tape around the end of the lugs. This means that you can take off one wrap after each coat, and not have a massive drippy buildup when you're finished. It's probably easier to take off the tape when it's stiff but not cured, but I always put epoxy on before I went to bed so I always had to do it when it was dry - bit more tricky.

The seams between bits of fabric now look much subtler, but it looks pretty homemade:

Built-up epoxy by comatus1649, on Flickr

So it's now time for more sanding.

I hate sanding.

You're taking off a lot of epoxy so begin with the rough stuff - I began with 80 grit aluminium oxide paper. Reading the Carbonmods skinning guide it tells you to use 240 wetndry, which is all very well if you're taking out little lumps and bumps on an otherwise flat surface, but you need to build up a lot more epoxy on these complicated joints, so you'll need to take it off more roughly. This is also your last chance to knock off the high points caused by loose fibres, rough joints and other mistakes. I started with 80, then 150, then 400 wetndry, then a quick go with 1200 to really smooth it out. This was slightly overkill - if you can't see scratches when it's wet, you won't see them when they're covered in epoxy.

This was the technique I mostly used:

Flatting round pieces by comatus1649, on Flickr
For flat bits you could use a block, but there aren't many flat bits on a bike (bottom of the BB shell is the only example really, unless you're doing some ambitious aero nonsense). Excuse the dodgy photo, I don't have three hands and had to wedge my phone between the chainstays ...

It's ok if you get down to fabric in places, but that's a sign you need to back off because once you start damaging the fibres you'll change the final appearance. It's hard to describe what exactly it looks like when you go too deep, but you'll see when you do it - the white high points, instead of looking like random lumps and drips, will look like tiny rectangles at right angles to each other.

Once you've washed off all the dust (and seriously do wash it off, in the shower and everything, because otherwise those little bits of carbon and epoxy dust will fuck it up), it will all look kinda ruined:

After being flatted by comatus1649, on Flickr
But that's alright - it's much flatter now which will make for a good final result. The reason we have to put all that epoxy on and then take it all off again is that there will be some bits of fabric that are maybe 2 or 3mm below the general layer of the part, and you want the surface to be as free from pitting as possible.

This is also a good opportunity for a few sanity checks - will the headset cups fit, for example, or is the joint overbuilt? Does the carbon extend over the edge of the BB shell, or too far onto the dropouts? You can fix all this later if you have to, but it would be nice not to have to.

Now for one final coat of epoxy. I applied this with paper towels to get a really smooth, thin, run-free surface. After this cured, I had a pretty good finish, dust nibs and the odd concealable pit aside:

After final very thin coat of epoxy by comatus1649, on Flickr

Next step is to polish this up with 1200grit, and think about lacquer ... This is the third week in a row I've said this, but I really do think it'll be done this week.

Just the joints; would be kinda neat to do the whole thing with very light carbon though. I think I've seen it done somewhere but can't remember; maybe an experimental Calfee or Brano Meres one.

Next update. This is brief because I can't be bothered to type it all out again. Look at my Flickr for more notes and process photographs.

MORE CF

Finishing the tape layup
Last on my hit list was the BB. I chose an aluminium one because it's much lighter than the steel equivalent I used before; however it's best to isolate carbon fibre from aluminium due to the potential for galvanic corrosion. So I skinned it with a thin layer of fibreglass first, then built it up with the carbon fibre as before. I took my lead from the wrapping guide already mentioned but had to change it quite a bit because my 25mm tape is much wider than tow. After the peel ply (hard to wrap tight around this complex shape) came off, this is what I had:

After curing by comatus1649, on Flickr

Looks pretty neat and strong. But if you look at my other pictures on Flickr you'll see that there are voids in the layup on top of the chainstays. These could have been avoided by building the fillets up more, or possibly by thinking about my wraps a bit more carefully. I'll have to fill these later, but I don't think they'll affect the strength too much.

Cosmetic skinning
So the tape laid up already is structural, and the bike is finished in that respect. However, I wanted to put a layer of carbon fibre cloth over the top to really finish it off - UD tape just looks black and uninteresting, and you don't have the nice weave texture people associate with CF. I also chose a carbon/aramid blend which will add a degree of crash protection.

This is a totally different process to the wet layup already shown. The skinning technique is generally used to cover car parts or things like that, and it's much much trickier on complex parts like the joints on a bike. It is also a tiny subset of the tiny community of bamboo bike builders who use carbon cloth, so this is rather undocumented territory. I was helped enormously by this guide, but I have a few tips of my own. First, use a thicker epoxy like the one CarbonMods / Easy Composites sell in their kits. West Systems is a bit thin really. And really do let the epoxy go off until it doesn't come off on your finger when you poke it - only then will it properly stick to the fabric. Otherwise it will drive you mad by coming off, plus the epoxy may soak through the fabric and spoil the look of the weave. You may need to use tape to hold it down while it cures, especially on the smaller tubes (you could alternatively use a very lightweight cloth (90gsm is available), but it's very very expensive).

Working with woven CF cloth is not very easy. It frays easily, is expensive, and the weave distorts if you look at it funny. Easy Composites will sell you 'ProFinish' cloth for £5 more per metre; it's just been sprayed on the back side with spray mount. I used the cheapest stuff I could find on eBay and it clogged endlessly. Post 3M stuff might be better. You want to slowly build up a thin layer on the back. If you're buying from Easy Composites you can cheaply buy a sample of their ProFinish cloth to see how much you need to apply. This makes the fabric a little stiffer but much easier to handle, cut and look after - no longer does it instantly fray wildly.

You need black epoxy for this so that bamboo can't show through the weave of the cloth. I used graphite powder because it's cheaper than pigment and has other uses. You want a smooth, very dark black mixture - mix the graphite into the epoxy before adding the hardener, mix, then transfer to another pot to avoid lumps of unhardened epoxy or graphite. Paint it on everywhere you want the fabric to stick:

Black base coat on dropouts by comatus1649, on Flickr

When it is tacky, you can then apply the cloth which you have already cut to shape, and hold it in place while it cures. At first I had it overlapping, and I then cut back the excess. For larger parts or those where you need a very neat symmetrical seam, I pinched it like this:

New improved skinning technique by comatus1649, on Flickr

When it is almost cured I trimmed back the flap and pressed what little excess there was left into the tacky epoxy. This gives you joins as neat as you are ever going to get. They will never ever be as good as the seamless appearance on moulded carbon frames, but they will look alright once the clear coats of epoxy have gone on.

Another note on complex shapes - I tried cutting the fabric into a shape that would let me do the joints with one bit of cloth, but it was a disaster. The best way, as it seems to me, is to do it in parts - first do the bits that could be considered not the end of a piece of bamboo, then when they're done, neatly do the bits that are the ends of the lugs. That sounds confusing, but the pictures may help. This is the second (and final) lot of black epoxy being put on the HT/DT joint:

Second application of cloth to the HT joint by comatus1649, on Flickr

That's all for now. At time of writing I'm just letting the epoxy cure for the last few bits of cloth to go on around the BB. I've fucked up a couple of bits but it's surprising how well the clear coats of epoxy cover it up (or that's the hope anyway). I will update with that whenever I manage to do it!

Thanks for reading, and for being patient!

Ben

Fuck. I had an enormous post all written out, and then I pressed submit and it disappeared like it hasn't done for ages. Of course this time I neglected to copy like I normally do. So this will be a bit briefer than it was beforehand.

ANYWAY. Update time...

SHINY BITS ARRIVE

Shiny bits by comatus1649, on Flickr

I've fallen for the whole disk brake fad. Got a TRP Spyre on eBay for less than the price of a BB5, and it should be a little better than a BB7 so I'm pretty pleased with that. Looks ace too. The hub is a pretty unexciting Shimano M756, which I chose because I like matching hubs and it can easily be converted into a pretty ace rear hub with a six-bolt sprocket. Rims will be Halo Aerotrack; spokes will be DT Swiss Revolution because I've never laced a wheel with very light spokes and it will be a good experience one way or another ...

More of what I wrote and lost tomorrow.

sigh

More delays I'm afraid. I'm unemployed at the moment and have run out of money entirely, so this will be on hold at least until the bloody Jobcentre process my 4.5wk old JSA application...

What a great thread already! The internet can be handy sometimes. Lovely bike as well, you're a lucky chap.

PS. If you PM me your address, I'll send you a bit of peel ply tape. I've got tons of it, and you'll only need a couple of metres max.

Rough up the surface before hand and get it very clean. Don't use white spirit. I'd use peel ply tape if I were you but you could just use perforated electrical tape, inside out.

I was going at a fair lick on a narrow dirt path, when I suddenly ran into a big divot running across the path where some drainage pipes had been laid and never quite filled back in again. Unweighted the front to avoid taco'd wheel and barrel roll and didn't shift back forwards in time; back wheel hits the edge of the divot like a nasty kerb and I get stabbed in the perineum by my saddle followed by a surprisingly composed endo. I had literally just passed a runner coming the other way but I think I got away with it.

PS. I didn't ream my seat tube on the last one; I found a seat post that was a snug fit and I thought that if it was held securely it didn't matter if it was a round peg in a oval-ish hole.

Thanks for your kind words, guys :) I've been feeling a bit down about the whole thing for the last day or so because I totally cocked up skinning the headtube with carbon cloth (mainly cosmetic) and ended up wasting quite a lot of epoxy and cloth, but I'll give it another go in a few days. I can't wait to see it finished either!

There are a few different ways to get the seat tube to work, none of them quite ideal. Most people try one way or another to recreate what you get on a metal-framed bike - either the bamboo seat tube or a metal insert has a slot cut in it, and a normal separate seat clamp tightens it. The downside is that the bamboo is prone to cracking if you clamp it directly, and the metal insert is both difficult to glue in securely and a little ugly in my opinion. On my first bike I kind of did this, but using a clamp like this - the bottom clamp held the (unslotted and hence still strong) bamboo, and the upper clamp held the seatpost. Worked alright, but it's difficult to get an exactly round clamping area the right size on a bit of bamboo, and it came loose occasionally from expansion and contraction due to humidity.

Another option is to do a fully integrated seatpost. This is a pretty cool idea if you know exactly how long you need it, and (vitally) don't plan to change saddle, cranks, pedals, shoes or height for the lifetime of the bike.

I'm going for a middle route which I'm not entirely convinced about, but I think it's a good principle at least. The first option is out because the thinner bamboo I'm using is only ~22mm internal diameter, which no good seatposts are made in. It is, however, the size of some old stubby BMX posts, and the diameter of the thinner part on the top of those shitty plain-top seatposts. So my plan is to have the bamboo going most of the way up to the saddle (as can be seen in the pics), with a very short 22.2mm seatpost glued in the top for the last couple of inches, onto which a Brompton Pentaclip is attached to hold the saddle rails. I'm hoping that with the Brooks saddle I plan to use the metal part should be mostly hidden anyway. The Pentaclip is not a pretty bit of technology but it's nicer and works better than these horrid things. At some point I'll find someone who can CNC me a nicer one.

Like I said, all these ideas have downsides. The downside of this is that I have to have a stubby cromo seatpost from the 80s glued into my lightweight bamboo and CF frame. There are a few aluminium ones about, but I'd rather carry the extra 50g or so and not have to worry about it bending (very unlikely for such a short bit, but it would be terminal for the bike).

It is quite time consuming to write up, but I really regretted not doing it properly the first time around. Now I'm regretting not taking very good photos, but I'll want to build another one to test out my prototype jig anyway ... it's a terrible addiction!

On the mechanical side, Sheldon Brown will teach you most things you need to know. Some of it is beginning to go out of date but it's a fantastic resource. Sounds like your bike is going to be really not to my taste but have fun building it up!

GETTING STICKY - CARBON FIBRE TIME

3 weeks later, I really should write a proper update. I haven't had as much time to work on it as I had hoped so progress is slow, but I have a few things to say further to my initial reflections.

Surface prep
It's obviously very important to get strong bonds between the composite joints and the bamboo or metal parts, and the first stage in this is effective preparation. The shiny outer skin of the bamboo has to be stripped off if it hasn't been already, and the surface abraded using coarse sandpaper or a file.

Likewise, the metal parts need to be roughed up with a file and cleaned thoroughly. Most things that degrease would be fine - water and washing up liquid (leave to dry well), alcohol, kitchen spray, chain degreaser, etc. The one thing I've come across that you really do have to avoid is white spirit - it leave residue which prevents a strong bond. I also sanded down the fillets to make them smooth and have a gradual transition into the bamboo, which will avoid having voids filled with lots of epoxy and little carbon fibre. Similarly if after putting on a layer of CF there are gaps left, it is sometimes worthwhile sanding them down flat, but there are no hard and fast rules.

First layup - headtube joint
Because it is the simplest joint on the bike, I decided to begin with the HT/TT/DT joint. It is also the most visible, so if you're not happy with your abilities then do some practice joints on scrap bamboo first (it would be very instructive to make some mock joints, then cut them up to see how good they are internally, like learning how to braze lugs). Also consider having a dry run of wrapping the tape without any resin.

This is the most technical part of building a bike, and as I'm only on my second (and indeed my first CF one) I don't really feel qualified to give detailed instructions. There is a lot of information out there - in particular I recommend this post on a very helpful blog, which links to a wrapping guide. You have to modify it slightly if using tape as I have done, or more significantly for joints which are totally different to the norm - I had to play it by ear entirely for the seat cluster / wishbone joint.

In brief, the principles of bike building wet layup are pretty straightforward. Mix up your epoxy as per the manufacturer's instructions, making sure you have enough to finish the job. Using a flat roller tray rather than a pot makes it go off slightly slower. Mix and mix and mix some more because it it's not properly mixed it won't work at all, and you won't realise until it's too late. Decide what wrap you're going to do, and cut a suitable length of tape or tow (you may want to get special composite shears) before getting all sticky. An arms' span was about as much as I could easily handle at once. Also cut about the same length of peel ply tape. Before you go on, think about what you're wearing - I know it sounds stupid but a) epoxy never comes out of anything and b) I get disproportionately hot and sweaty while laying up carbon, and it's a bit late to change when you're all covered in resin. You will probably want to wear gloves at this point as well.

Now wet out the area on the frame around which the tape will wrap. Don't worry about going overboard here as it will just drip off if you use too much, but you can't lay carbon fibre onto a dry surface and wet it out afterwards. Anchor the tape as mentioned in the wrapping guide by wrapping it over itself and pulling it taut. There's no need to pull the tape mega tight as you wrap it around, but don't let it go slack. Whenever tape crosses over itself the lower bit has to be fully wet out first - you can either wet out all the tape as you go along, or (my preferred, less messy option), only wet it out at the end or when you have to go over a part. A foam (AKA Jenny) brush helps to work the resin deep into the weave of the tape - when it's about right, the polyester threads holding the unidirectional tape go almost transparent.

When all the epoxy is applied and the carbon is fully wetted out, wrap peel ply tape tightly around the joint to press it flat and squeeze out any excess. If necessary, add more epoxy to wet out the peel ply. Make sure you leave the end of the peel ply un-stuck down so you can peel it off later. You'll be left with something that looks like this:

HT wrapped in peel ply by comatus1649, on Flickr

And after leaving it for 8 hours and removing the peel ply (which doesn't properly adhere to the epoxy, you can build up the next layer. Because the tape is thick, I only had to do probably 3 wraps (of about 2m each) to complete the HT joint. After removing the last lot of peel ply, I painted more epoxy on top and let it cure into shiny prettiness:

Pre-sanded HT joint by comatus1649, on Flickr

... then sanded it down to make it nice and smooth for the skinning process to come:

Sanded HT joint by comatus1649, on Flickr

Seat cluster joint
The principles of the other joints are just the same - at the time of writing I've 80% finished the seat cluster joint, and not started the BB joint. Both are rather more complicated than the HT joint, but being methodical, thinking about what direction the joint needs to be strong in, and following the wrapping guide make the process not too bad. I was soon left with something that looked a bit like this:

Seat cluster from another angle by comatus1649, on Flickr

Most of the whiteness in the picture is from the flash, but as a matter of fact this last wrap was slightly under-saturated with epoxy, and the white polyester binding can see be seen in real life. As long as each layer is wet out full before the next one is put on top, this isn't too much of a problem - I can put more epoxy on top and it will soak in, but it is easier to get it right first time. The last thing you want are voids of unwetted carbon (or for that matter bits of epoxy with no carbon fibre) within the joint to undermine the fantastic composite properties of cured carbon fibre that we're aiming for.

Dropouts
As mentioned above, I cut away the excess foam in the dropouts and plugged the ends with thickened epoxy so the dropouts were firmly wedged in place. This meant that I didn't have to get too technical about wrapping the dropouts with the fibres running in the right directions - just wrapping tape a couple of times around the joint will strengthen the bamboo enough that the epoxy/metal plug will never be able to break out. This was much, much easier than my technique on my first bike where I needed to reinforce an initially weak joint. It never worked and broke twice which, I don't mind telling you, is quite disconcerting when you go down a curb. Because each of the 4 dropout joints only use a little bit of epoxy and maybe 4-6 inches of tape per layer (I might do a double layer), this is also a good way to use up the little bit that's often left over after you've done a bigger joint.

Test fitting sneak peek
So despite the fact that I took obsessive measurements and checked them numerous times, I've been worried since the beginning that I'd fucked something up and the wheels wouldn't fit. So to set my mind at rest (even though it was much too late to actually do anything non-drastic about it), I took the wheels off my other bike and gave it a quick go. The headset's not in yet, of course, so the front end will rise by 15mm or so, but it gave me a quick idea of how it might look. It also proved that there is plenty of room for the 32c tyres I have at the moment so the 35mm Kojaks I plan to use should be great. I reckon I could probably fit up to 50mm tyres in there if I was careful, which might be fun if I can find a light slick set (fat treadless tyres are the mutt's nuts). I'm liking the look of the Kinesis DC37...

Mockup 1 by comatus1649, on Flickr

That's all for now. I'm getting a bit bored of wrapping lots of tape, so I might skin the headtube next... I need to get some fibreglass from a friend before I can give the BB joints a go.

Ben

The first bits of CF went on in the last couple of days - I've been working away so haven't had time to do much. Will post pictures when I have time to take good enough ones - it's hard to get them when you're covered in epoxy.

Reflections so far - unidirectional tape is much easier to handle than tow, and the thin strands of fibreglass used to hold the tape together provide a very useful visual guide of whether the carbon is properly wetted out (they go virtually clear). Peel ply tape is also very useful, though it is a bit difficult to get it tight on complex joins - it's 50mm thick and doesn't stretch. Perforated electrical tape over the top of peel ply would probably give you the best of both worlds, as the PP is very good at making sure you use just the right amount of epoxy and get super bonds between layers, and the electrical tape would compress it even better. I'm slightly concerned that using just vinyl tape would not encourage strong lamination as you end up with a thin layer of smooth epoxy on top of each layer of carbon. PP sucks out excess epoxy (though in practice you generally have to add more to wet out the PP fully anyway) and leaves a great texturised finish.

For reference, you want appropriately 11-12 grams of epoxy to 10 grams of carbon to wet it out fully. Considering the density of epoxy is about 1.1-1.4 g/cm^2, a reasonable rule of thumb is a millilitre of epoxy to a gram of carbon; 25mm 200gsm UD tape is 5g per metre. Add a little bit for pot/brush wastage.

... also bamboo's not so great with squeezing forces either, and it's a nightmare getting something nearly round to be round enough for a clamp (my last bike had a seatclamp directly on the bamboo and it was forever coming loose). But it's a more elegant solution, so I'll give it a bit more thought.

I had, yes, but found them difficult to find and even more difficult to get them at an acceptable price. I was never sure what to search for (is 'ISP topper' the only/main name they're known by?). Any cheap versions / good places to get them?

Have you considered a bigger top to your ISP? That would let you use a normal ISP topper. Ritchey is in 3 sizes up to 38.35mm, which is presumably big enough that you could wrap your bamboo with some crabon fribé to build it up to the required diameter and roundness

They're nice bits of work, overbuilt but very functional. Pretty ideal for their function, I guess. They're built using quite a clever PVC tubing jig - they're built off a table, on their side, rather than in the more normal orientation for building bikes, which makes using very cheap plastic tubing a possibility. A lot of thought has really gone into them.

***STARTING THE FRONT TRIANGLE

***More tacking...
With the rear triangle all tacked in place, I decided to carefully start on the front while I waited for my epoxy to arrive. There are several ways the jig could be set up to do this including holding the rear triangle at such an angle that the TT needs to be vertical and can easily be checked with a spirit level, but I couldn't make this work. In the end I just went for a simple configuration to hold the two bits in place after I had set the angle (71.5deg ST and 9.2deg TT = 80.7deg between the two). A loop of wool was used to help me set an accurate angle, as the ST has a slight bend to it:

Jig configuration 3 by comatus1649, on Flickr

Somehow, this simple setup was incredibly difficult to get right. I couldn't really clamp this joint very well, so I would hold it in place for up to 20 minutes at a time, get what seemed to be a fairly firm self-supporting joint, go to make a cup of tea and it would have fallen off when I got back. Regardless of what I did, it just would not stay put. I began to blame supernatural causes for the difficulties I was having, and invented elaborate rituals to appease the spirits of the house. After a while I think I just held it in place for ages and ages and it did the trick. Luckily, thanks to the big mating areas, this is a fairly strong joint that's not prone to suddenly breaking like the CS/BB joints can be. If I make another bike using this jig I will make a little bracket to support the end of the TT.

When this was set, I turned to the DT. Both DT and TT were only roughly cut to length at this stage, as it was too difficult to work out how long they would have to be in isolation. The mitre on the BB end of the DT is particularly complex because it has to accommodate a small part of the ST as well as the BB shell. The same jig configuration was used, with the DT running in the channel. Unfortunately the nuts in the channel protruded just slightly too far and made the tube go off to one side, so I had to use my multitool as a shim to keep it centred. The distance between the TT and the DT at the end was set by eye, holding the HT up against them. This turned out to be surprisingly accurate.

Filleting
When these tubes were both set, I wanted to fillet several of the joints in the rear before going any further - filing the mitre for the HT in situ would put a lot of strain on the joints, and I needed them to be fully reinforced first. Filleting is the process of building up thickened epoxy around the joints to round off the edges and really increase the surface area of the joint. This not only makes the joints stronger themselves, but also allows a more curved shape to be achieved with the carbon fibre, making it much stronger.

Because I'm cheap, I used the sawdust I had been collecting all along to thicken the resin rather than any of the additives West System make. This worked fine, though the bits of sandpaper that had ended up in the dust even after I sieved it made the fillets speckled. Getting the epoxy the right thickness is the first and most important stage - too thin and it will just run everywhere and be a nightmare to handle; too thick and it won't adhere properly or add much strength. You're aiming for a peanut butter sort of consistency (smooth, not crunchy), though this depends a lot on what filler you're using. With my grainy sawdust it was not as smooth as peanut butter, but it had a similar thickness - it is more of a paste than a liquid in the mixing cup. After a few goes you get a hang of it; if you get it just right the fillets almost make themselves - they're thick enough to stay where you put them, but thin enough to flow out slightly and leave a fairly smooth finish. If you find the epoxy is dripping, it's too thin, and if it's grainy like wet sand, it's too thick. And don't mix up more than you need - the filler makes it go a lot further than you might have thought.

It's also really, really important to mask things off carefully before getting epoxy near the frame. If you get it in the BB threads, it'll be a nightmare to get out. You should also mask off the parts of the bamboo that won't end up part of the joints, but I forgot at first. Later on I used clingfilm between the bands of masking tape to create nice sharp edges to the joints.

Once your mixture is at the right consistency, you want to work it into the joints and round them off nicely. It's such a fiddly process that it's impossible to properly describe it, but using a rounded flat spreader you can slap on the epoxy, then carefully work it in to the right shape - a light touch and having made the mixture just the right consistency are the key requirements for success. Build up a little bit at a time, and don't obsess about getting it just right. Once I was done, I left it in the sun to go quite hard (an hour or so perhaps, but it varies so much), then moulded it into exactly the right shape with wet fingers. When it's nearly touch-dry, it can be worked without getting you all sticky as long as you keep your fingers damp. It's also worth saying that although I do this without gloves on and am fine, if you have sensitive skin or don't know you're not allergic to epoxy resin, you should wear gloves.

ST/TT/SS and ST/DT/CS joints filleted by comatus1649, on Flickr

**Setting the headtube
**This is the happy stage when it really begins to look like a bike frame. Using a protractor, I set the frame in the jig so that the headtube angle was vertical, and marked where I had to cut using a double-ended plumb bob:

Getting the HT angle right by comatus1649, on Flickr

Using this I knew where the deepest point of the mitre had to be on both tubes, and could carefully cut from the end of the tube to this point. Then it was a simple but laborious matter of cutting away the excess until the mitre was tight and even. For this I used a rotary tool with a sanding drum - I didn't use it much on the other joints because it's noisy and creates a lot of mess, but here it was worthwhile to avoid the risk of jamming the rasp and breaking one of the joints. It's also a lot easier to use a power tool than carefully rasp two mitres at once, especially when it's nearly impossible to clamp it in a vice. To finetune the mitres, I wrapped a bit of emery cloth around the HT, and used it to perfect the mitres.

When it was about right, I set up the jig in configuration 4, which uses the part previously used to hold the rear axle to hold a channel vertical, to which the HT is attached. With the jig set up so that the HT has to be vertical, its alignment on both planes can be checked with a spirit level rather than faffing around with a protractor. This join also required a fair bit of holding in place because I hadn't glued my jig together very well and it was all starting to come apart, so there was a lot of play.

Setting the HT from another angle by comatus1649, on Flickr

Final filleting
With all the poles in place, I could now finish the filleting and at last have a fairly robust frame shaped object which I didn't have to worry about breaking. The ends of the CS and SS were much bigger than the dropout tabs, so I wanted to cut them down a bit to make it more streamlined. This was done with some very careful saw-work.

Trimming the CS and SS by comatus1649, on Flickr
After this picture was taken, I also removed the visible expanding foam so that I could plug the gap entirely with epoxy. This should give me a really strong join between bamboo and metal, even before the reinforcement.

Filleting the HT and the dropout intersections was much easier than the previous few joints, partly because I was getting better at it and the joints were simpler, and partly because the mix was slightly thicker and much easier to work with. In general I think you should err towards a thicker filleting mixture - it's easier to work with and lighter (filleting can add a lot of weight to the frame).

At the moment, the frame is out in the garden curing. The thickened epoxy takes a really long time to cure, so don't rush on to the next stage if you've got all the parts to hand. The one possible exception to this is that there's a technique where you lay fibreglass on top of still-wet fillets, but I think that would be difficult to do on the complex joints on a bike. As it happens, I need to get some fibreglass from a friend so I can isolate the aluminium BB shell from the carbon fibre to avoid galvanic corrosion, so can't go much further at the moment. I start a residential job for six weeks next week, and I expect I probably won't be able to work any more on the bike until that's over. In the mean time I'll still be able to check the forums and answer any questions people might have...

Ben

MAKING THE FIRST JOINTS

Bottom bracket and seat tube

The first joint in my process was the ST/SP to BB junction, a simple right-angle T. I have taken several photos which can be found in my Flickr photostream, but I'll only briefly describe the process here for clarity. Because bamboo poles are not entirely straight in all planes, you need to decide which way they will point. My ST pole was only very slightly bent, but I wanted it to bend away from the rear tyre and be straight when viewed from above - by comparing it with a straight edge and just rolling it in my hands I found and marked its forward face, and made sure to mitre it correctly.

Also be very sure to double check the BB orientation as well - most shells have a groove cut on the inside (past the threads) on the right hand (drive) side, but double check with a BB as well. I have read a build report where the guy had it all completed before he realised he'd put the BB in backwards, and had to run it as a self-undoing left hand drive.

Cut the mitre roughly with a saw first, as coarse rasps are prone to leaping off and taking bites out of the user if they don't have something to guide them. This whole process is of course much easier if you have the piece in a vice (either with rubber jaws or, better, a pipe clamp (which can be improvised from bits of wood)). Check regularly as you go - you want to end up with nice tight mitre that doesn't wobble, holds the other piece at the right angle, and doesn't have any visible spaces. It's not the end of the world if you're no good at it (I'm not, but I'm getting better...), as it will have very little effect on the joint's eventual strength, but it makes the initially glued joint stronger and easier to work with.

A pretty good mitre by comatus1649, on Flickr

I was pretty happy with that one.

Next stage is to have a dry run before gluing it. With my jig, it's easy - the short perpendicular section at the end of jig part 2 holds the BB exactly parallel to the longer aluminium section made up of part 2 and 3, joined with part 5 and some nuts - the BB is held in place with bands, as is the ST, in such a way that the joint is pulled together at precisely the right angle.

ST and BB shell in the jig by comatus1649, on Flickr

Having measured and remeasured and satisfied myself that it all worked fine, I applied a thin even layer of Gorilla Glue to the bamboo, having first misted it and the BB shell with water. Held in place, it had 80% of final strength in two hours, and was ready for the next stage of gluing.

Chainstays to BB and dropouts

For attaching the chainstays, the jig needs to be changed to configuration 2. Parts 3 and 5 (the long piece of aluminium and the short piece of rod) are removed from part 2 and replaced with part 1. Part 5 is used to hold the dropouts in place in part 1. The chainstay length is changed using the threaded rod part of part 1, screwed into part 2. The BB shell and attached ST can be rotated, and is held upright by the tension on the bands, as seen below:

Quick pre-glue layout by comatus1649, on Flickr

The BB/CS joint is very hard to get just right at this early stage because of the small mating area, the numerous angles to get right with the mitre, and the tight clearances. Bamboo's greatest weakness as a bike material is that it's quite straight and fairly uniform in cross-sectional shape, whereas for chainstays you want a bent, ovalised or crimped stay to create space for the tyre and chainring. Smaller bamboo poles have alternating flat sides which can be used to some extent. You also need to leave enough space outboard of the chainstay to build up the joint without interfering with the BB cup.

A great deal of measuring and head-scratching took place at this point, along with some test fitting of the chainring. I eventually satisfied myself that it would probably fit, though I would most likely have to file away some of the bamboo on one or both sides. I should be able to strengthen this just fine using CF, but if you're using other materials for the joints you may wish to consider using a wider BB shell to increase clearances (up to 100mm is available, but this limits BB choices and confuses chainline; I decided to make a standard 68mm shell work somehow).

The seat tube needs to be set to the right angle - this means that the rear axle needs to be elevated. I planned a BB drop of 55mm, so put DVDs and CDs underneath the right-angle section of part 1 until the centre of the axle was at 95mm from the table, compared to the BB's 40mm (in the centre, of course). I could then use a large protractor to set the angle of the ST. The inner tube bands hold the BB firmly enough when you pull the slack to the correct side - in other words, as it was leaning to the left, I needed to make the band tight on the right hand side. In jig configuration 2.5, parts 3 and 4 are used to provide a somewhat haphazard support as well, just in case:

Jig configuration 2.5 by comatus1649, on Flickr

Eagle eyes will note even more inner tube bands around either ends of the chainstays - on the BB side, I arranged them to overlap the edge of the bamboo by a fraction of a millimetre in the hope that it would stop them slipping down the BB shell. It didn't work very well, and I should have just scratched up the shell more. I didn't because it was a machined aluminium shell with a light textured finish rather than a smooth cast steel one, but I had several problems with poor adhesion. On the dropout end of the chainstays the bands were used to pull the chainstays tightly against the metal to improve the joint. Because the tubes were filled with foam the joint was much easier to get right this time around - the tabs on the ends of the dropouts are much smaller than the insides of the tubes. Some manufacturers make dropouts with plug ends rather than tabs, which I would imagine would work very well.

By the way, the angle of the dropouts was something I wasn't sure about. Eventually I went for an angle similar to horizontal dropouts which made the bottom of the aluminium inserts parallel to the floor. I think this looks fine, though you loose a little horizontal travel because it's diagonal. It does (in principle) mean that with a rear rim brake, the rim would stay aligned with the pad regardless of chain tension, which is the reason why horizontal dropouts are really a bit diagonal and track ends are actually horizontal.

Seat stays to dropouts and ST

Now for the final stage to complete the rear triangle - attaching the seat stays to the dropouts and the seat tube.

[By the way (as we shall see...), when I say 'complete', you shouldn't have any great expectations of strength for a frame only tacked together in this way with glue. It is reasonably rigid, but requires very gentle handling. The purpose of this stage is to get it all held together; epoxy filleting strengthens the joints enough for further modifications, a brief fiberglass wrap prepares the way for a durable CF wrap, and the CF wrap is what actually gives the joint all of its strength. Because the CF wraps entirely around the whole joint, what is inside it is almost of no importance.]

I wanted to do a wishbone seat stay design for this bike to make the rear triangle a little stiffer, to allow good tyre / mudguard clearance even with compact geometry, and to make it look cool! Making 6 joints all line up at once would have been a real headache, so I did it in two stages - first I connected the seat stays to the horizontal part of the wishbone, and secondly I connected the vertical part of the wishbone to the ST and to the horizontal part, and connected both dropouts. The first stage was done in situ to make sure it was all aligned correctly, with the horizontal part of the wishbone resting against the ST. After that had set, I trimmed the horizontal part to size and rounded the edges so that it would eventually have a more natural shape:

Roughed out wishbone by comatus1649, on Flickr

After that, it was trivially simple to rasp the tiny vertical part of the wishbone to shape and glue it in place. Glue can be a bit frantic to work with because it needs to be held in place just right and you're constantly fretting about it going off or dripping onto things, but by doing it in two stages this was made very straightforward. Again, inner tube bands came to the rescue holding it in place at the top, while I used hair bands for the bottom (see Flickr).

A couple of hours later I was feeling pretty happy with the whole thing, and wanted to take it out of the jig to set up the next configuration to attach the top tube. And then this happened:

Oh snap. by comatus1649, on Flickr

The right hand side had broken at the wishbone bridge and the bottom bracket - I forgot to remove the hairbands that were tensioning the joint before I took it out of the jig, and it snapped the two tiny joints just like that. With better preparation (roughing of the BB shell in particular) this might not have happened, but it was mainly a human error. However, it was very frustrating to have to awkwardly reglue two joints which had just been made so easily, and broken even more easily. I had been overkeen in trimming off the excess glue as well - this weakens the joint, but allows the next stage (filleting) to take place properly (it is stronger to have a joint with excess glue trimmed off and an epoxy fillet made around it than a fillet over the top of excess glue). Though I'd still advise trimming excess glue, leave it until you're just about to do the fillets, and be very gentle with the frame.

On the other hand, this was nowhere near as frustrating as what happened next. As you, oh patient reader, have read above, I precisely measured the ST angle with the correct rear axle elevation. However, because it didn't seem to be broken and I thought it had already set firm, I didn't remeasure it after a visiting friend knocked the damn jig off the table. Remeasuring didn't even occur to me until I had carried on, glued the wishbone seat stay and fixed the rear triangle semi-permanently in place. When I did remeasure it, I found that I had created a bike with a 69.5deg seat tube, an accidental bamboo version of Bauer's stealth bike in the 1993 Paris-Roubaix. It was such a massive error (3.5deg) that I can't believe it was anything other than it getting knocked over and me not thinking to check it.

This required a major redesign; I could rip it all to bits but I'd put in a lot of work and would have to remake some parts. I decided to work around it.

My original design had a very high BB, with a drop of 55mm (which would be high for a track bike, let alone a road bike). I decided to raise this by 10mm - this still makes it a little higher than a Surly Steamroller and will be just fine - it may even have some handling advantages but I'm not so sure about that. More importantly, it will make the ST angle about 71.5deg - still slack by modern standards, but I will be using a Brooks saddle. Because of their rails, they often need a layback saddle on modern frames, but should suit this frame fine. It seems perverse to design a frame to suit a saddle, but that's part of the fun of custom framebuilding!

I had also made a couple of other minor changes, such as making the rear triangle more compact. I couldn't get a headtube cut to a sensible length from Ceeway, so with the freedom / hassle of cutting it myself, I went for a 147.5mm HT, the strange result of aiming for 150mm and having more trouble with squaring it off than I had expected. Maintaining the same TT length for the sake of argument in BikeCAD gave me a slightly shorter reach or front centre which actually on reflection is no bad thing, so I kept it. It should tame the otherwise fairly long wheelbase a bit. There may be a touch of toe overlap but I can deal with that. Here is the revised design:

Revised geometry by comatus1649, on Flickr

That's all for now. In the next few days I will be working on the front triangle, using still more jig configurations. I'm going to order the composite bits today, so may wait to fillet the rear triangle before I start on the front, to avoid repetitions of previous 'Oh snap!' moments...

Thanks for waiting ;)

Ben

FIRST JOINTS - BUILDING THE JIG AND TACKING THE REAR TRIANGLE

In the long time since my last update, I've made a reasonable amount of progress. It's been a bit slower than I would have liked, and moving house has prevented me updating until now. Also, I start a residential job for 6 weeks in July, and probably won't be able to work at all on the bike until I'm done. So this project is going to take a lot longer than I had planned.

***Building a jig
***As more illustrious builders like Ron Cooper have shown, it's perfectly possible to build a great bike without the precision engineered and extremely expensive jigs that most builders use. My first bike was also built jigless and came out reasonably well - with lots of measuring and some creative thought, I believe that you can build a near-perfect bike this way. But this time, I fancied having a go at building a jig, albeit a very different one from those commercially available.

Commercial jigs are very, very expensive. For example, a lovely Henry James jig costs $4000, plus $750 for the stand to put it on. If you read the Paterek Manual you'll also find him recommending precision-lapped plates made from stone or metal to take exact table measurements, costing thousands more. Even homemade jigs using aluminium extrusions come to several hundred pounds. I believe that the fundamental assumption of jig designers and framebuilders, namely that all the variable parts need to be held precisely in place* at the same time*, is the reason why it's so difficult to build an affordable jig. I also believe that it's a wrong assumption - the builder can only ever work on one joint at a time, even if all the others are held tightly in place for him or her. So my jig design was built from the ground up not to hold the rear axle, BB shell, head tube and at least seven other tubes all in place at once, but to deal with one joint at a time.

My philosophy is that it is easier for a small-scale builder to take the time to precisely lay out each join on its own, rather than make a large jig which has the entire bike laid out. Working from simpler geometrical principles, much less precise machining and setup is required. Consequently, it is modular, compact, and very cheap. It cost me under £20, and while I've already found some flaws, I'm happy with the principle.

Once I've finished the bike and adequately tested my design, I'll write it up more fully, but you should be able to see how it works from my pictures throughout. The raw materials are easily obtained - 1m of 17mm inside diameter aluminium U-channel, 2 x 500mm M10 threaded rod, about 14 M10 nuts and a few washers. The nuts fit snugly into the extruded aluminium and can be glued into place, allowing rods to be attached to the extrusions to adjust lengths or join parts together. The completed jig can be disassembled into a few simple parts:

0: An assortments of nuts and washers used to attach parts and lock threaded rods into place
1: 1 section of aluminium 120mm long, into which two nuts are glued about 5mm from either end; a length of threaded rod (about 350mm) is attached at right angles to the centre of the aluminium, on one side (ie. so that it can be laid flat in a T-shape with the open part of the U-channel upwards). This is primarily to hold the dropouts.
2: A 350mm section of aluminium with two nuts near one end, and a 68mm section attached at a precise right angle at the other end, with the open part of both channels facing up. This is primarily to hold the BB and the poles attached to it.

1. Another long section of aluminium identical to 2, but without the short section at right angles.
   
2. A separate length of threaded rod 500mm long.
   
3. A short length of threaded rod about 150mm long.
   
   

As will be seen below, this can be set up in numerous different ways...

Hi everyone. Sorry for the big lapse in communication - I've just moved house which has meant I've only had mobile internet for the last few weeks. I'll answer questions and get some lunch, then I'll type up the next big update...

Djangoberry/Phil: Sure, feel free to PM me if you have any questions. I can't claim to be an expert by any means but, as you'll find, there are a lot of things you pick up even building only one frame that you just wouldn't have thought about before.

Thanks for the link to RattleCAD - I've never used it before for some reason as I find even the free version of BikeCAD easy and powerful enough. It does lack some things though (and I'm not going to pay hundreds of pounds for the full version just yet...), so I might find some use in RattleCAD in future.

As you say, Ceeway's site is notoriously difficult to use, but their customer service is great. I decided to splash out on the TSS7 stainless dropouts with TSS2 and TSS8 inserts - they came to a pretty serious £56 before VAT and are so far the single most expensive part on the whole thing. I liked the functionality of the sliders though, and the increased space to strengthen the joint compared to horizontal dropouts. I went for the CYRK18 headtube from the Thron tubeset.

I had planned to use this UD tape, with a thin overlayer of this fabric. I wouldn't advise using a CF/kevlar blend for the whole thing because kevlar has a lower tensile strength. A top layer of it would protect against abrasion and impact damage (how much I really can't say; possibly barely at all, but more than CF alone). 99m of a 25m tape would be plenty, but I'd use unidirectional rather than woven tape for most of the joint, or half of your material (/weight/money...) is going in a direction that achieves next to no extra strength, - you're better off using UD tape or tow with the fibres aligned according to the load on the joints. In other words you'd need about twice the length of woven tape compared to UD tape, assuming they have the same weight per metre.

From my research (which you may wish to check) a bare minimum of 100g of unidirectional fibres should be enough to make all the joints (plus of course a roughly equal weight of resin). This corresponds to about 20m of UD tape or about 130m of 12k tow, 260m of 6k tow, etc... I will probably buy 40-50m of UD tape to be on the safe side as I'm using such skinny tubes and may wish to really build up the joints. If you're only using woven materials, you'll need something nearer to 200g as a minimum (Brano Meres used ~360g of woven cloth on his beautiful bamboo MTB).

Hope that helps - sorry it sounds so complicated!

Right, update on the way...

Anyone recommend any of the local shops for facing and reaming a headtube? I like BikeZone normally but apparently they don't have a facing tool because it's not that necessary and the cutting bits are too expensive (!).

Cheers,
Ben

http://www.ebay.com/itm/Dropout-Adapters-Fixed-Gear-Fixie-Road-Track-Bike-Adapter-Vertical-to-Horizontal-/151000580960?pt=Cycling_Parts_Accessories&hash=item2328560360#ht_2227wt_923http://rover.ebay.com/roverimp/1/710-53481-19255-0/1?ff3=2&pub=5574889051&toolid=10001&campid=5336525415&item=151000580960&mpt=764045

http://www.sellutionmtb.com/images/large/ssadapter1.jpg

I dunno, I think that's actually a pretty good idea, as long as there's some sort of way of stopping it rotating that's not doing it up really really tight.