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From: (Mark Drela)
Subject: Re: Aluminum/composite epoxy suggestions?
Date: 10 Nov 1994 01:06:22 GMT

In article <39reo9$>,
(Timothy Gotsick) writes:

|> I have a composite wheel in which the aluminum hub flange has
|> broken loose from the composite material.  Can anyone suggest
|> a suitable epoxy or other adhesive with which to reunite these
|> parts?

My favorite for jobs like this is Hysol Epoxy-Patch (Clear variety, 
don't use the White or Gray which have fillers of some sort).
It's incredibly tough and resists peel quite well.  I'm sure 
many slow-cure epoxies would also work well.  Don't even THINK 
about 5-minute epoxy, cyanoacrylate (Super Glue), or epoxy 
laminating resins.  All these are relatively brittle.

To get the adhesive into the bond line, you'll have to pull it
completely apart.  If you can't, there isn't much you can do,
other than force it in under pressure with some sort of cuff.

                   Mark Drela
    o/LO  .' 
     O  .'  Gravity-Powered Technologies Lab 
      .'  MIT Aero-Astro Department  37-475

From: (Mark Drela)
Newsgroups: bc.cycling,,
Subject: Re: Carbon Fibre Frame Repair
Date: 10 Jun 1996 23:06:35 GMT

In article <>, Chris Baisley
<> writes:

|> Had a little spill on Saturday, and cracked a rib.  More importantly,
|> I cracked a seat stay on my '94 Mongoose Team SX carbon fibre frame.
|> Mongoose says it can't be repaired.  Has anyone tried a homebrew
|> remedy?  I am thinking along the lines of a fibreglass repair kit,
|> hopefully of slightly higher tech nature.  The stay is fractured around 
|> approximately 3/4 of its circumference, and the bike was essentially
|> rideable after the crash.

A good fiberglass wrap should patch the break OK.  Don't try to use an 
auto-body repair kit with fiberglass mat and/or polyester resin, though.  
I would use a good, slow-curing laminating resin and cloth, and maybe 
some uni-directional fibers under the cloth.  You should be able to get
this stuff at a good RC-model hobby shop.  Hobby-Poxy Formula-2 is a decent 
resin, although there are others.

Prep the area by sanding down to the carbon for about 1.5" on each side
of the break.  Apply the fiberglass/resin with the aid of a heat gun or 
hair dryer to get good wetting, and blot off the excess.  Ten wraps of
4-oz cloth tapering to nothing away from the break seems adequate.  One
triangular piece of cloth, 3" wide at the base and 18" long should do it.
Then bind tightly by spirally wrapping with a 0.5"-wide strip of polyethylene,
wiping the excess resin as it gets squeezed out.  The poly won't stick 
(if removed soon after the resing sets up), and will give a shiny finish.  
Use masking tape 1.5" from the break to make a clean-looking patch.

                   Mark Drela
    o/LO  .' 
     O  .'  Gravity-Powered Technologies Lab 
      .'  MIT Aero-Astro Department  37-475

From: (Mark Drela)
Subject: Re: Carbon Frame Repair (Lug Separation)
Date: 11 Aug 1996 23:59:28 GMT

In article <>, Dennis Manke <> writes:

|> I have a Specialized Allez Epic in which the non-drive side
|> chain stain pulled off of the BB shell and the chainstay bridge
|> broke free from the drive side chain stay. I can pull the stay
|> completely off the internal lug, so it can easily be cleaned.
|> Can anyone comment on the epoxy I should use (and any special
|> instructions on preping/bonding). The Stay/Lug is Carbon/Aluminum
|> and the bridge appears to be plastic.

You want some sort of slow-curing epoxy.  My favorite brand is
Clear Epoxy-Patch epoxy made by Dexter Hysol, which is stocked
by our lab supply stockroom, but may be hard to find in retail.
Try a good hardware store or model airplane shop.

A structural-bond epoxy should retain some flexibility after complete
curing with no sign of brittleness.  Carving with a knife is a good 
test --- the shavings should not crack as they come off.

You do NOT want any of the laminating epoxy resins used for wet layup
of composites, since they set up very hard and are prone to peel.
Likewise for polyester resin.  If you go to the model shop, do NOT
get the commonly used Hobby-Poxy Formula 2, which is much too hard.
The Formula 3 is quite good, but it is a gel and can only be put 
into joints which you can dissasemble completely.  Forget about 
the 5 or 15-minute epoxies --- complete crap.

Prep the joint by sanding thoroughly with coarse sandpaper (100 grit, say), 
and degreasing with acetone or brake-cleaning fluid.  Apply the epoxy 
immediately, before new oxidation builds up too much.

It's usually a good idea to do the cure with heat from a hair dryer.

                   Mark Drela
    o/LO  .' 
     O  .'  Gravity-Powered Technologies Lab 
      .'  MIT Aero-Astro Department  37-475

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