Rebonding carbon saddle rails

[brearley]

I have a full carbon saddle which had been replaced under warranty but I'd like to repair this also.
Front edge became unbonded and eventually one of the rear corners came unglued also so I pulled the 3rd corner off to fully remove.

I have access to vacuum pumps, bags, epoxy etc what prep should I be doing before applying epoxy then pressure so that it doesn't unbond again?
I've previously tried Araldite on the front edge which worked for a while

Has anybody done this with a guide to doing so that'd be ideal

[justkeepedaling]

Haven't done it before, but you're gonna want to do surface prep and I would just use a structural epoxy. Put it in a clamp to let it set for the specified time

[Kumppa]

If we are talking about a Berk saddle then it might not be easy. Local small carbonfiber shop rebonded Berk saddle for me (only front edge) and they told me the problem is to know the right type of epoxy to make the repair as durable as possible. Also wondered why such products are made using this type of bonding method...

They tested a few different good quality epoxies under the saddle. Old epoxies were removed with a dremel. The repair looked good and no epoxy was saved but the saddle only lasted less than a month of use. Repair did not cost much because they were also interested in finding the right way to fix it but this time it didn't work for an 80 kg person.

Maybe someone else would have done a better job or the repair would have required something else.

[diecast]

OP, I think you're right to research this. The consequences of saddle failure may not be benign.

I had a similar issue and just stuck it back with some general purpose Henkel epoxy. It lasted little more than 100km. When I got back I discovered that the unsupported shell had been punctured - full thickness - by the saddle rail clamp bolt... Lucky I didn't puncture myself...!

For the little it's worth (in my non expert opinion), the flexibility of the saddle shell needs to be balanced with the flexibility of the rails. Seems to me that if either part of the equation is unbalanced it'll put stress on the join.

Likewise, surely the join should be more than just a blob of adhesive, but also some wraps of carbon? But then again, as I say, I have no technical knowledge in this area, only practical experience.

If you ever find out a satisfactory answer to your question please post back here. I've got a saddle in pieces that I may not be foolish enough to try and repair again, but it's of interest.

I suspect that in general a repair is inadvisable other than for a professional or those with high risk tolerance.

[EtoDemerzel]

3M 420 structural epoxy but it's expensive. You can also contact 3M, they are good about referencing their extensive catalog.