Bicycle Mechanics - cracked carbon frame near the seapost suggestions ?

hi guys ,
i have a problem with my carbon frame , a small crack has apeared near the seatpost clamp ,
it seems that the seapost has cracked probably because of overtight , and at the same time the frame has cracked about 1 cm
the seatpost clamp was switched on the other side , i was thinking maby is better this way
what do you think is that dead frame walking ? :) will the crack extend ?
or is there something that can be done ?
suggestions ?
thanks

picture : http://img830.imageshack.us/img830/3663/p1010601.jpg
http://img255.imageshack.us/img255/355/p1010608w.jpg

If it were Metal you can stop a crack from continuing by drilling a hole in the end of the crack..
you could try that with CF and That may help..

I think you may be needing to replace the frame..

Another data Point to keep me on metal frames , preferably steel.

If it were Metal you can stop a crack from continuing by drilling a hole in the end of the crack..
you could try that with CF and That may help..

I think you may be needing to replace the frame..

Another data Point to keep me on metal frames , preferably steel.


That does scare me about carbon. But I would still like one. :D Do they still make titanium bikes? Haven't heard about them in, oh about 20 years.

I don't think the crack will spread. However, I would reinforce the spot with Epoxy, and wrap with a few strands of carbon fiber, Kevlar, or fiberglass.

I don't know if you ever worked with composites before, probably not, since you wouldn't be asking.

What I'm saying is, you are lucky, because carbon fiber can be repaired with Epoxy and fiberglass, at room temperature 75 or 80 degrees F.- you don't want or need a welding apparatus.

I would use Kevlar and epoxy to wrap the cracked tube. You'll have to search online to find Kevlar.

Epoxy is available at the local hardware store. Look for 2-Ton Epoxy, in the 25 ml. double syringe, made by a company called Devcon.

You could get a good piece of fiberglass at a Hobby store, that sells model airplanes. This repair should cost less than twelve dollars, including the cost of disposable latex gloves to wear.

I think it can be fixed. It is hard to make out from the pics but I would assume that the carbon fabric did not tear, but only the epoxy has cracked. It could probably be infused with more epoxy then wrapped with a few layers of prepreg carbon ribbon to shore up the crack. I might not look as pretty with the extra layers, but it should hold. This procedure is best left to a person with experience with making repairs to CF bike frames. Craig Calfee comes to mind if you don't know of anyone local. If the frame is expensive enough to warrant the repair, you might want to send a few pics to Calfee and get his opinion and possibly an estimate to make the repair. I know that he does make repairs on frames other than his own.

Edit: Looks like hotbike was thinking (pretty much)the same thing but beat me to the punch with an answer. I don't know if I would trust fiberglass, but you might get away with it if you use more thickness than I was picturing. If you can get any kind of carbon cloth or prefereably unidirectional ribbon, I would have more confidence in the long term.

Do they still make titanium bikes? Haven't heard about them in, oh about 20 years.
The sure do. Litespeed, Lynskey, Moots, Airborne, Merlin, Seven, Independent Fabrications and many others are still very much in the Ti frame business.

thank you guys for you answers

i`m not from uk or us or a big country , i`m from eastern europe so most probably i will have to get the materials for repair online

this is what i found until now :
kevlar :
http://cgi.ebay.co.uk/KEVLAR-FABRIC-SAMPLE-8-11-6-5-OZ-/260627340159?pt=US_Fabric&hash=item3cae999b7f#ht_562wt_1137

epoxy
http://cgi.ebay.co.uk/Devcon-2-Ton-Clear-Epoxy-Resin-28g-Bails-Findings-/370350724745?pt=UK_Crafts_Cardmaking_Scrapbooking_Glue_Tape_EH&hash=item563a9f9689#ht_2793wt_1137

in my area there arent serious repair shops not to mention carbon specialists , so i will have to do the thing alone so what do you think about the materials ?
maby some suggestions on other materials to use ?

fiber glass is this any good ? : http://cgi.ebay.co.uk/Body-Filler-Spreaders-pack-10-Fibre-Glass-P38-P40-/190394699473?pt=UK_Body_Shop_Supplies_Paint&hash=item2c54688ed1#ht_927wt_911


wouldn`t some carbon fibre be advised ? don`t know for what to search on ebay could someone help ?

i found this carbon repair kit opinions ? : http://www.carbonmods.co.uk/Products/carbon-fibre-repair-kit.aspx

Devcon epoxy should be perfect. The kevlar should work too but is not as stiff as carbon plus there is the matter that kevlar is yellow and will need to be painted if you don't want the repair to stand out. Carbon tape or fabric (cloth) would be better if you can find someone who ships to your country. One foot of this stuff would work. http://cgi.ebay.com/Carbon-Fiber-Tape-5-7oz-x-1-wide-/250578506297?pt=LH_DefaultDomain_0&hash=item3a57a49239

i could search for some carbon fabric tape , how many layers should i apply ?

if i buy from different sources the epoxy the carbon + transport it`s gona get epxensive anyway

wouldn`t it be better to just buy this repair kit wich seems proffesional ?

http://www.carbonmods.co.uk/Products/carbon-fibre-repair-kit.aspx

and is about 60 dollars with transport included

what do you think about the kit ?

hi guys ,
i have a problem with my carbon frame , a small crack has apeared near the seatpost clamp ,

picture : http://img830.imageshack.us/img830/3663/p1010601.jpg
http://img255.imageshack.us/img255/355/p1010608w.jpg

STOP- WAIT- A QUESTION FOR YOU

Did you check with your LBS if it's under Warranty?

My friend had a similar issue and wanted to trash the frame. I went to the Orbea web site and saw that his frame was covered.
The LBS handled the swap and actual he received a new seat post, stem and handlebar and a better model.

If you try to fix it you will forever void any chance of it being a warranty issue.
of course it looks like you over torqued the seat post clamp, but that happens.

i`m pretty sure that the frame is not under warranty anymore

the best i could find was this :

http://cgi.ebay.co.uk/SAMPLE-CARBON-FIBRE-TWILL-WEAVE-CLOTH-/330464812974?pt=UK_ToysGames_RadioControlled_JN&hash=item4cf13cdfae#ht_550wt_1137

It LOOKS like the area that broke is being pulled inwards to be in contact with the seat post. What is the fit like between the post and the frame? I'm thinking that the seat post was a little too loose a fit and the seat clamp pulled the top of the frame in hard enough and the relief cut in the seat tube was short enough that it snapped this area to allow the clamp to pull the frame into tight contact. If I'm right then it's not the seat clamp being too tight but a poor fit of the seat post to frame. A proper fit should be a light push fit that will hold the post and maybe even post and saddle in place by itself without any clamp even being on the bike.

If it were me I'd fill the crack with a good grade of clear epoxy WHILE the seat post clamp in in place and tight. Just be sure there's some thing on the post to prevent the epoxy taking hold of that.

There's really no point in taking the post out and binding the frame since the clamp will just want to snap the repair all over to make it fit the post. And in fact looking at the picture of the crack it sure seems like I can see that it's flexed inwards which supports my suggestion that the seat post is too small. It may be the correct size but the frame is out or the post is a smidge under the correct size but not enough to be the next size down. Either way I'd bet that with no clamp and if that area springs out that the post will literally fall into the frame. And that sort of easy sliding fit is too loose.

it`s actually the other way arround ... the seatpost fits the frame very well
it`s actually very hard to move the seatpost inside the frame when i want to lower it or get it out ... the length of the seapost is good aswell so that is not a problem
as i wrote at the begining of the thread the seapost cracked probably because of overthight and this way it probably made itself a little smaller because of the crack (vertical crack near the seatpost clamp about 2 cm)
i already made an order for another seapost that should arrive soon but the frame crack i have to take care of it anyway or at least try :)
i ordered a 400 mm alloy seatpost 31.6 - hopefully the length will help a bit

it`s clearly that the frame cracked because the seatpost cracked , i didn`t found out about it until i saw the cracked frame

i could search for some carbon fabric tape , how many layers should i apply ?

if i buy from different sources the epoxy the carbon + transport it`s gona get epxensive anyway

wouldn`t it be better to just buy this repair kit wich seems proffesional ?

http://www.carbonmods.co.uk/Products/carbon-fibre-repair-kit.aspx

and is about 60 dollars with transport included

what do you think about the kit ?

I have bought products from Carbonmods before you might want to contact them with what it is you want to do and they can give advice on product you should use.

thks for all your support
i have sent an e-mail to carbonmods and hopefully i can rezolve this problem soon

.....as i wrote at the begining of the thread the seapost cracked probably because of overthight and this way it probably made itself a little smaller because of the crack....


My bad. When you wrote that the first time I took it to mean the seat tube of the frame. Let's face it, folks saying that they collapsed a seat POST are few and far between so perhaps you can excuse my "translating" it to mean seat TUBE.... :D If you tightened things enough to collapse and crack the seatpost then it's no wonder the seat tube cracked as well.


The good news is that the crack is back on the rear where it's not highly stressed. Likely you could get away with just drilling a stress relief hole and call it a day. But if you want to repair it I'd say that the important part is to strongly link the lower fixed portion with the cracked loose "wing". To so that you need to run vertical fibers across the crack to tie things together and form a stress carrying column of carbon that runs across the crack and supports the compressive stresses that this area will see from the slanted seat tube. To do this if it were my frame I'd router out a small channel to allow the fibers to contact more of the deeper fibers to aid in tieing the crack together better. Something like this diagram below.

But really? I'd probably just glue the crack and see if it cracks loose again. If it does then the stress is working at the crack and it's loading up the fibers at the end of the crack and it will likely extend with time. Or worse, you may load the other intact side enough to begin a crack there as well. At the first sign of this happening THEN I would channel out the frame as I showed and support the crack with unidirectional carbon fibers. Wrapping around the tube won't do anything since the crack is nearly horizontal now and all the fibers from wrapping would not be crossing the crack enough to matter. All you'd do is cover up the damage and let it continue where you can't see it. If you run vertical fibers across the crack either with the "excavation" I showed below or as a purely surface patch then at least you're crossing the crack and supporting the fibers on each side much like the frame was before the crack. If you do use my method the patch is going to be quite strong due to the thickness and depth. But then the bond will be key. It would be important that the epoxy you use is very compatible with the original epoxy so the joint is very strong.

Yeah, that scares me about carbon frames too. I've seen this before. I think something like this usually happens in cases where the mechanic tightened the seat binder bolt with way too much torque. It would be fine for a little while, but after sitting on the bike and riding, the constant stress put on the seat tube near the binder bolt will eventually show it's wear, possible resulting in the crack that you see here. On metal frames, you usually only get deformation near the seat tube top where the binder bolt attaches. On carbon frames, crack!

Yeah, a torque wrench is very much needed for working on a carbon fiber frame unless you've wrenched enough to ballpark the torque by feel (but then, you wouldn't be here). Ritchey makes a torque key which is very useful, here (http://www.competitivecyclist.com/road-bikes/product-accessories/2010-ritchey-torque-key--m4-5nm-5511.51.1.html).

thank you all for your replyes ... i got this mail from carbonmods :

Thanks for your email.

That crack is only small and it should be possible to repair it quite easily.

I would suggest removing the clamp to allow the cracked area of carbon frame to relax and then sand-papering the tube all around where you will do the repair (in fact all the way around the tube in a ring shape) so that you have a good rough surface for the repair to bond to.

This is the kit you should buy:

http://www.carbonmods.co.uk/Products/fishing-rod-pole-repair-kit.aspx

Apply some resin to the tube (making sure it gets into the damaged crack) and allow it to cure partially so that it is just tacky. Then cut a thin strip of carbon for the repair and wrap it around the tube several times. It will stick well to the partially cured resin so it will be easy to get started. Pull tight and wind it wound about 3 times, wetting it out with more resin as you go. Once finished, wrap the repair tightly with the shrink tape (included in the kit) and heat the tape to make it tighten. Allow to cure for 8hrs. Once cured remove the tape. If you want you can smooth and polish the repair to make it look neater (sandpaper and polish are included in the kit for this purpose). It should be very strong.

Best regards,

Matt



do you know what he meant by " wind it wound about 3 times " - english is not my first language and i don`t realy understand the expression ?

@BCRider thank you for you suggestion ... but in my opinion i think a wrap around would be better if you look carefully at the picture the crack has a down path its`s not orizontally ... i think a wrap arround would be best as suggested by carbonmods
but i`m thinking if i wrap arround how much should i avoid covering the hole (the cut in the frame for the seatpost clamp to bend the frame) / should i wrap it and apply the exposy and then cut the chanel ? or should i just try and wrap it just under the chanel

thank you all for your replyes ... i got this mail from carbonmods :

Thanks for your email.

That crack is only small and it should be possible to repair it quite easily.

I would suggest removing the clamp to allow the cracked area of carbon frame to relax and then sand-papering the tube all around where you will do the repair (in fact all the way around the tube in a ring shape) so that you have a good rough surface for the repair to bond to.

This is the kit you should buy:

http://www.carbonmods.co.uk/Products/fishing-rod-pole-repair-kit.aspx

Apply some resin to the tube (making sure it gets into the damaged crack) and allow it to cure partially so that it is just tacky. Then cut a thin strip of carbon for the repair and wrap it around the tube several times. It will stick well to the partially cured resin so it will be easy to get started. Pull tight and wind it wound about 3 times, wetting it out with more resin as you go. Once finished, wrap the repair tightly with the shrink tape (included in the kit) and heat the tape to make it tighten. Allow to cure for 8hrs. Once cured remove the tape. If you want you can smooth and polish the repair to make it look neater (sandpaper and polish are included in the kit for this purpose). It should be very strong.

Best regards,

Matt



do you know what he meant by " wind it wound about 3 times " - english is not my first language and i don`t realy understand the expression ?

@BCRider thank you for you suggestion ... but in my opinion i think a wrap around would be better if you look carefully at the picture the crack has a down path its`s not orizontally ... i think a wrap arround would be best as suggested by carbonmods
but i`m thinking if i wrap arround how much should i avoid covering the hole (the cut in the frame for the seatpost clamp to bend the frame) / should i wrap it and apply the exposy and then cut the chanel ? or should i just try and wrap it just under the chanel



Hey. Fantastic! You got a decent solution there to try the repair yourself. Come back to this thread and let us know if you were successful with the repair. I'd be interested to know if it worked. Good luck!

"Pull tight and wind it wound about 3 times, wetting it out with more resin as you go." --neomoco

Matt, meant to cut a length of CF long enough to make three layers of cloth over the crack. Start the first layer with the partially cured epoxy, once you've made the first revolution apply the resin to the cloth and make two more revolutions.

"...english is not my first language and i don`t realy understand the expression ?" --neomoco

I think that was a mistype... English can be quite fractured depending on where it's spoken, however.

Brad

"Pull tight and wind it wound about 3 times, wetting it out with more resin as you go." --neomoco

Matt, meant to cut a length of CF long enough to make three layers of cloth over the crack. Start the first layer with the partially cured epoxy, once you've made the first revolution apply the resin to the cloth and make two more revolutions.

"...english is not my first language and i don`t realy understand the expression ?" --neomoco

I think that was a mistype... English can be quite fractured depending on where it's spoken, however.

Brad

I think he meant "wind it AROUND three times".

Pardon me, but when I gave my earlier reply, I had not looked at the photographs. Now, looking at the photographs I see the problem.

neomoco wrote:
"....but i`m thinking if i wrap arround how much should i avoid covering the hole (the cut in the frame for the seatpost clamp to bend the frame) / should i wrap it and apply the exposy and then cut the chanel ? or should i just try and wrap it just under the chanel"

You should wrap the carbon around, covering the channel. After the epoxy hardens, cut the channel. A file or a hacksaw will be fine.

Three times, or three layers, might be too much. You might make it impossible to hold the seat-post tight, if the binder bolt can not squeeze the tube.

Kevlar would be a good material, however, Kevlar is very difficult to cut, being as it is nearly indestructible.

The carbon mod repair kit has more carbon and resin than you need.

I think he meant "wind it AROUND three times".

Pardon me, but when I gave my earlier reply, I had not looked at the photographs. Now, looking at the photographs I see the problem.

neomoco wrote:
"....but i`m thinking if i wrap arround how much should i avoid covering the hole (the cut in the frame for the seatpost clamp to bend the frame) / should i wrap it and apply the exposy and then cut the chanel ? or should i just try and wrap it just under the chanel"

You should wrap the carbon around, covering the channel. After the epoxy hardens, cut the channel. A file or a hacksaw will be fine.

Three times, or three layers, might be too much. You might make it impossible to hold the seat-post tight, if the binder bolt can not squeeze the tube.

Kevlar would be a good material, however, Kevlar is very difficult to cut, being as it is nearly indestructible.

The carbon mod repair kit has more carbon and resin than you need.


well i was thinking i`m not gona wrap the whole tube all the way up so basically in not gonna put any carbon were the seat clamp squezeez the tube ... so what do you think is that a good ideea ?
i might put only 2 layers i`ll see how thick the carbon is .... thks for the advice

of course as soon as i will fix it i`ll post the pictures ... for now i wait for the carbonmods kit that i ordered

hotbike, I didn't take the directions to also cover the seatpost's slot, at the most just a small percentage at the lower end.

Looking again at the pictures I think that drilling a stress relief hole at the end of the crack(s) and a couple of single layer patches, one on each side of the seatpost would possibly work just fine. Lay the patch on the partially cured resin, use a small roller to remove any voids, apply a top coat of resin and again use a roller.

Because it may be difficult to determine if the seatpost clamp was overtightened or if constant flexing through normal riding is the root of the problem, I wonder if a tight fitting mountain bike seatpost, which is typically longer than a road bike's seatpost might offer a bit less flexability by reducing leverage thus helping to prevent these semi common CF failures. Thoughts?

Brad

i thought about buying a longer seatpost clamp myself but i think is going to put even more stress near the crack

What they suggested for the repair seems very generic and misses two key points. First is that the crack is right at the seat post clamp relief slot and end hole. Second is that you can only go so far up the tube because you want to leave the area for the clamp at the original size and only so far down because the big branch area of the seat and top tube and seat stays is just right at the crack. So you're going to cut a narrow strip of cloth about 20 to 30 mm wide and long enough to wrap around two or three times. And even then I'm not sure from the pictures that this will work well. Maybe try it with some paper first to see how wide it can be. But for the repair to work you need to wrap the cloth so that it goes evenly above and below the crack to give a good length of bond above adn below the crack. So there's no way to wrap it without covering slot. You will just have to re-cut the slot in the end after it has cured. That would remove a lot of the strength of the repair. So wrapping it seems rather like more than you need and much of the wrap will just make the seat post clamping harder to do.

So if you don't want to cut out some of the carbon to make for the sort of patch I suggested then I'd look at making up three patches that are each slightly bigger than the other. One that is a D shape which is as wide as the crack and a about the 1.5 times the height. This first patch will fit rigth over the crack evenly with the flat edge of the "D" along the slot and hole. The next would be about 4 mm larger all around the curved part of the D and the third another 4 mm wider than the middle layer. The flat part of these bigger "D"s again sits just at or slightly over the edge of the slot. If any of them go up onto the seat post clamp area then cut them down a little so they don't get in the way of the clamp. Sand the area as they said but only where the carbon patches will go and about 4 to 6 mm's further , fill the crack with epoxy, wet out the patches with epoxy and lay the three patches over the area of the crack so they blend out nicely with the smallest patch first and the biggest last.

Again I think they gave you a fairly generic solution since the crack is right by the branching of the seat and top tube and the seat stays. So it would be really hard to get a length of shrink tubing on there that spreads out well. So what you may need to do is use something like stretchy food plastic wrap over the layup and then bind it down tight with electrical tape or some other option over the plastic wrap. Or maybe the plastic food wrap, some sponge rubber and a stretchy tensor bandage wrapped quite tight over the area so it goes around and through all the tubes to give as even a pressure from all angles to the patch as you can get to force it down against the tubes. The idea being to press the carbon layers into close contact and feather the edges to the surrounding area so you don't need to do any sanding to get the shape right after it cures. Just some light sanding with fine wet sanding paper to blend the outer surface in prep for the polishing.

I would wrap just above the small hole wrap 3 times and suggested by the professionals recommendation.Just as described let cure cut slot as it was and re-drill hole done.
By the way I have used their products for other stuff and have always had great results with it.

thank you all for your suggestions i will see what type of fix i will choose ... i`l have to try with some paper as suggested by BCRider to see if there is room for a wrap and i`ll go from there
hopefully soon i will get the carbon mods kit
today i made a fairly long ride on the bike and it i haven`t noticed any expansion in the crack

today tuesday 7 sept. i got the carbon mods kit ... that was super fast delivery ... i made the order friday and got it today ... wich is super for international delivery

stage 1 : drilling the hole you have here some more pictures to understand better how the crack is positioned

http://img837.imageshack.us/gal.php?g=p1010612l.jpg

so what will it be ? wrap arround or the 3 shaped as a D patches as BCRider suggested ? :)

i was thinking of maby making something live this :

http://img295.imageshack.us/img295/3773/p1010618a.jpg

this will cover the crack about 5 mm above and 5 mm under it

It kind of depends on the type of carbon cloth supplied in the kit. A simple 1-over 1-under (plain) type weave or a unidirectional tape does not conform to uneven surface curvatures as much as a (crows foot) satin cloth which is usually like 1-over 3(or more)-under weave. This ability to conform to complex forms is called draping. Assuming that you have a plain weave or uni-tape, then experiment with paper forms, as someone else suggested, and see what works best. If you can't wrap all the way around and still come out flat, then a series of patches each overlaid over each other would work. Play with different shapes to see how you can maximize the surface contact area. The important part is that you don't want any air gaps between plies or areas with thick fills of epoxy. No wrinkes either. That is why you need to squeeze the repaired area with the shrink tape if possible or use some other means to apply pressure while the epoxy is setting. Don't worry about the air being needed to cure the epoxy - it will cure just fine in an absence of air.

BTW, I would still go with three layers over two, but that is just my opinion.

Steve has described the weave issue very well. You can make your own "bias" tape by cutting regular cloth on a 45 degree angle. But if you do this youll find that the fibers on such small strips want to fall apart. The only way to handle it is come up with someway of attaching it to a carrier until it's wrapped around and then peel the carrier away. I have not had to resort to such a thing myself but if you have any cheap glass cloth around try cutting a 40mm strip of bias cut cloth dry and then lay up the same cloth on some newsprint and resin it. While wet cut the bias strip. The resin and newsprint SHOULD hold it all together well enough to let you lay the bias strip in place and then peel away the paper. But with this you sure won't be able to wrap it with any tension. It would be strictly a lay in and leave other than pressure wrapping to compact the layup and get a nice finish.


There is another option if you are looking to wrap it instead of patch the area. You can order up some loose bundle fiber in carbon. This is stuff called "tow". It's the loose unidirectional fiber that is used on machines that weave sheets, pulltruded tubes, weave tubes, etc, etc. But the advantage of using tow instead of ribbon or bands of cloth in this case is that you would be better able to wrap around the joint given the complex shape shown in your third picture in the gallery. To wrap this crack with loose tow you're going to need to do a < like wrap that passes both over and under the top tube end on the right side of the < like wrapping and overwraps over the crack on the left side of the < wrap to get the coverage. If you just try to go over the top of the top tube joint the wrapping will have a strong angle on it and it'll just slide up off the crack and you'll have a big mess on your hands. With the shape of the area there just isn't any way to do a tape wrap and shrink tube as the kit guy suggested.

BTW, if you like the loose bundles of tow option to wrap the joint up and if you have trouble finding a supply that does't come only in 1000m spools you can mine your own tow bundles by buying a sq meter of coarse weave carbon cloth and just unravel a few of the strand bundles. Not a cheap way to go but it is an option.

Looking at your latest pictures I just can't see how you'll do a neat and workmanlike patch by winding the cloth around the whole tube. The crack is right at the joint which from the pictures will make it impossible to get a straight crossing angle wrap. At best I think you're commited to doing a patch style repair but maybe with longer bias angle patches than my D option. Or just extend the D shapes so they wrap a little further around the joint. After all, there's nothing at all wrong with the front or other side of the frame. But you want the patch to extend out far enough onto the good parts and be thick enough to replace the support lost in the crack and spread the loads out over enough other carbon and resin bonding that you don't just end up with a new stress point and have your patch delaminate itself from the frame.

i want to do something like this http://img295.imageshack.us/img295/3773/p1010618a.jpg
i won`t wrap it because i don`t thin either that it will work

step 2 : sanding : http://img638.imageshack.us/img638/9506/p1010619z.jpg

step 3 : alcohol wipe : http://img833.imageshack.us/img833/4781/p1010621sb.jpg

step 4 : applied some resin to the tube and let it cure for about 3 hours until it`s "tacky" : http://img823.imageshack.us/img823/2764/p1010625.jpg

step 5 : apply about 3 patches and wet each one after i apply them (this was suggested by the carbonmods as it would be easier to handle the carbon) : coming soon

i want to do something like this http://img295.imageshack.us/img295/3773/p1010618a.jpg
step 5 : apply about 3 patches and wet each one after i apply them (this was suggested by the carbonmods as it would be easier to handle the carbon) : coming soon

Looks like you are proceeding correctly so far.

In keeping with what BCRider said, make each successive patch a bit bigger (on the order of 4-5 mm on each edge) than the one before it, so that the edges can adhere to the existing frame material rather than just the patch below it. That will provide the added benefit of a tapered ply drop-off rather than a sharp edge where the patches end.

I think that what BC said above is to cut the patches such that one or two are not square with the weave but on an angle like maybe 45 degrees. While techically this is what is done on large aircraft structures, by his own admission this will make the fabric want to fall apart while you are trying to work with it, especially with the small size of the patches. In my humble opinion this is probably overkill for a repair such as yours.

Good luck!

step 5 : apply about 3 patches and wet each one after i apply them (this was suggested by the carbonmods as it would be easier to handle the carbon)
i did step 5 it didnt went perfectly because some strands of carbon were flying everywere but in the end it was ok
i applyed 3 patches one bigger than the other , with the smallest one first , then i applyed the shrinking tape and used the hair dryer (i used an old one and after about 5 min it went all in smokes and broke :)) good thing i had a spare) - because of the position of the repair it was hard to make the tape shrink perfectly but i would say it was acceptable
i will let it cure for 12 hours and i will post tomorrow a picture with the results

Drill small hole just beyond the end of the crack. Bind seat tube just below slot with 3 layers of kevlar tape and epoxy. Replace carbon seat post with properly sized al one. Put seat post binder bolt at back. IT will then be good for however long you want to ride this bike.

Want to see how this finishes :)

Hey neomoco, what clear coat paint are u going to use? Polyurethane is the way to go just in case, do not put laquer from a rattle can, that paint it is too hot and who knows what it will do to the carbon and for sure it will eat the other clear u have in there.

u-pol #1 clear coat will work (aerosol) this one will work also.

http://www.repaintsupply.com/pd_2_part_2k_aerosol.cfm

Post pictures please.

I sort of thought that after looking at all the options that you would decide to go with the patches. That's a pretty darn "busy" part of the frame to patch with a full wrap around.

And as you've found out when you cut a plain weave cloth into small patches it sure unravels fast, doesn't it..... :D

well this is it - i didn`t come out very nicely : http://img835.imageshack.us/gal.php?g=p1010629.jpg - some carbon strands got loose unfortunatly - it got a little messy
i have a lot of sanding to do to
i was thining of doing what i saw in a carbonmods video : sand it with 120 paper , then put about 2 coats of epoxy , and then sand it again with smaller paper 240 with wather and some soap and then even smaller paper , in the end use a cloth with the polishing compound i got from carbonmods

althow the rezult is not very pretty i`m pretty sure the sanding polishing etc. will give me a pretty good rezult .. i hope
as soon as i finish it i will post pictures with the end result

i`m not really satisfied with how i placed the patches ... i think i will sand it well and then apply one more patch a bit upper than the last time
the most important thing is to be a good repair ... the looks is not that important but i`ll see how it comes up in the end

and one small problem : the shrinking tape sticked to the carbon and i can`t get it out it seems i will have to sand it aswell

later edit : after some sanding and applying some resin i`m startind to think that after the final smooth wet sanding and polishing it will looks as good as new will post results soon

I can assure you that if you get the last carbon layer and coat on nicely after you final sand and polish it will look great make sure you cut the sheet so the edges are nice and clean and but up to each other it will look great!
Good job by the way for first go at it!
As I mentioned earlier I have used CarbonMods products and always has worked great.

Actually that's not bad at all. Sure you need to sand it some but the patches themselves look to be laying down nicely.

When you sand it try to only sand the edges and work the shape to generate a smooth feathering and blend into the main frame. Avoid the woven faces of the patches at all costs. This means that you want to work with stuff more like a coarse cut small flat file or a coars cut small half round file more than a big fold of sandpaper. Or use something like nail filing emory boards. These narrow sanding or filing tools will give you far more control over the shaping and blending and by using them carefuly you'll do less damage to the frame around the repair and the woven faces of the last patch. If you cut into the woven surface of either the frame or the patch you'll end up with noticable damage after your epoxy top layer clear coat. If there's some epoxy seams where they should not be again work these down with the file or emory boards so that you ONLY remove the glue and don't get into the carbon weave below. All of this is detail work so go slow, be patient and make the patch come out feeling as smooth and well shaped as a new crop apple. For working on fussy surfaces like this when I'm building my model airplanes I like to use a very bright table light close by so I can turn the workpiece and see the shadows of the surface as I hold it so the work area is on an angle to the light. By working with the lamp at a low angle "twilight" position the shadows will show you where there's still work to be done very quickly. The light in conjuction with feeling the surface with your fingers will aid you in working the glue seams off and feathering the edges down and into the frame surface very nicely. Where the patch meets the frame it's OK to leave a very slight edge about the thickness of a cigarette paper where you can just barely feel it. Better to leave it like that than to work it down and cut into the frame's carbon. The clear coat epoxy you add over the patch area will fill in a very slight step like that.

For the clear top coat try this. Smear on a THIN coat of the epoxy and then warm it with a hair dryer. The heat will make the epoxy flow like water and thin it out a lot. Work the epoxy around but don't use much at all otherwise the heat will make it run and drip. You want it to go on about as thick as a light coat of varnish. Let cool and cure. Now wet sand the patch and surrounding glossy area LIGHTLY with 400 grit wetordry sandpaper to remove the gloss. If there's any little dips or valleys they will show as shiney spots. When you wet sand this first clear coat you mostly want to make the surface just dull and to blend only the slightest of imperfections. Try not to sand all the way through to the carbon.

To get control over the paper you want to tear it over the edge of a sharp desk into quarters and then one of these into half again. The little rectangle that is left you will fold and tear like this;

http://www.finehomebuilding.com/item/12862/folding-trick-makes-sandpaper-last-longer

They say in the vid that this is mostly to make the paper last longer. But the more important thing for us here is that it makes the pad of sandpaper more rigid so you have better control over it. And the reason I suggest working the paper down to that 1/8 sheet bit and then do the four way fold trick is so you end up with a little pad that isn't much bigger than a large postal stamp. Again this will give you more control over the paper while sanding the small and highly curved patched area. One last thing. Instead of cutting the paper with a knife after the first fold try this. Fold the paper as he showed, then open it and fold it over the other way again so it comes out back to back. Open it and just tear 1/2 of the short bend crease using a ruler or a sharp table edge. Then fold the paper as he showed. It's faster, neater and doesn't ruin the tip of a knife blade which could be better used for other things.

Now you'll want to add a second heat thinned smear coating as well. Thanks to the heat gun you've found that the epoxy comes out very smooth and shiney. Your frame appears to be one of the matt finish frames so shiney is out of place. To get this last patch to come out matt I'd suggest a light wet sanding with 800 grit paper. The finish it leaves will match what your frame appears to have. If it is slightly duller than the rest of the frame a bit of automotive wax and a buff will bring up a nice clear looking dull sheen.

thank you guys for you answers

i`m not from uk or us or a big country , i`m from eastern europe so most probably i will have to get the materials for repair online

this is what i found until now :
kevlar :
http://cgi.ebay.co.uk/KEVLAR-FABRIC-SAMPLE-8-11-6-5-OZ-/260627340159?pt=US_Fabric&hash=item3cae999b7f#ht_562wt_1137

epoxy
http://cgi.ebay.co.uk/Devcon-2-Ton-Clear-Epoxy-Resin-28g-Bails-Findings-/370350724745?pt=UK_Crafts_Cardmaking_Scrapbooking_Glue_Tape_EH&hash=item563a9f9689#ht_2793wt_1137

in my area there arent serious repair shops not to mention carbon specialists , so i will have to do the thing alone so what do you think about the materials ?
maby some suggestions on other materials to use ?

fiber glass is this any good ? : http://cgi.ebay.co.uk/Body-Filler-Spreaders-pack-10-Fibre-Glass-P38-P40-/190394699473?pt=UK_Body_Shop_Supplies_Paint&hash=item2c54688ed1#ht_927wt_911


wouldn`t some carbon fibre be advised ? don`t know for what to search on ebay could someone help ?

i found this carbon repair kit opinions ? : http://www.carbonmods.co.uk/Products/carbon-fibre-repair-kit.aspx

From google:

http://www.ehow.com/how_5960258_repair-carbon-fiber-bicycle.html

www.sheldonbrown.com/rinard/carbonqa.htm

www.sheldonbrown.com/rinard/carbon_fiber.htm

And these people should be willing to ship repair materials to you:

www.carbonology.com/kit-no-2-the-tube-repair-kit-size-b-p-240.html

http://www.carbonology.com/repair-moulding-kits-c-130.html?sesid=8niu2pr00t69dg0sddr705q8b4

I think u did a good job, u still need to polish/sand and put some clear coat. But so fa looks pretty good to me :)

contact cyclart.com these guys just fixed a problem with my carbon fiber frame. They are the experts they will tell you more or less if its worth fixing.

Haven't read the whole thread, so I dunno if the point's already been made, but given that crack happened in response to the seatpost being crushed, it occurs to me that you may be lucky in that the carbon is prolly still pretty strong in most of the directions it usually needs to be - it's given in a weird way that doesn't really apply when you have an uncrushed seatpost in there.

So I'd just soak the crack in epoxy and see how it holds up.

...Ah, you had a go already. Nice job.


after some sanding and applying some resin i`m startind to think that after the final smooth wet sanding and polishing it will looks as good as new will post results soon
It won't look as good as new cause the weave won't match... You could just paint the seat cluster black and fade it to clear...