G/Flex epoxy

Can someone explain to me the difference between West Systems G/Flex epoxy and the older type two part epoxy ?

It looks like the mixing ratio 1 to 1 makes it easier, and it also can be used on plastic boats, but would I stay with the older stuff for kevlar boats ?

Jack L

Jack, I think the Gflex is intended to
be used as more of a repair epoxy that has good adhesive qualities. I would use it for special repairs that require good adhesion (hatch seals,broken paddle,coaming repair, etc). I recently covered my skin boat in the 105 resin with 207 special clear hardener and did this as an alternative to the Skin Boat Store Goop or a varnish. If you are repairing your kevlar hull on the outside, you will need a gelcoat covering or something else to provide UV protection. I think Gugeon (sp?) has a UV additive. What is the repair you are planing? Bill

Not repairing anything right now.
I don’t use any gelcoat on my ultralight kevlar boats, and when I use epoxy on my QCC, I just spray it with white auto paint. - lately I don’t even bother painting the fix.

I figure a ugly boat makes it mine !

I have redone the whole bottom of my Jensen 17 and made many patches and repairs in the past.

I was just curious about the G/flex, and trying to figure out what the difference is.



I have the two four ounce bottle kit and
plan to bring it on longer trips as a “fix all”. It would work as an adhesive or hull repair compound. It is easy to use and pack in the boat. Since cosmetics are not the top priority…never mind the UV protection. It is going to be interesting to see how the west system holds up on the skin boat. In terms of ease of use, there is nothing that even comes close. Bill

The Gougeon Brothers say they brought out G-flex to have a wider range of applicability in bonding damp wood, metals, ceramics, and plastics than their traditional 105 epoxy resin and 205/206/207/209 hardener combo.

It also has a higher modulus of elasticity which might be of benefit for boat materials with more flex, like Royalex. I think its main value in boat repair has been for use on polyethylene, which has traditionally been difficult to bond to. I have heard good reports for bonding to ABS and vinyl, as well.

I recently used it to repair a cracked cockpit coaming on a polyethylene C-1. I bonded the crack with G-flex and reinforced the repair with 2 layers of fiberglass, using G-flex to wet out and bond the glass.

G-flex is sold in kits with both un-thickened resin and hardener in plastic squeeze bottles, and thickened epoxy resin and hardener in toothpaste-like tubes. I used the unthickened stuff, but the kit included silica gel which I used to thicken the epoxy to bond the cracked edges itself.

The G-flex can be mixed visually 1:1 by volume without weighing it or using mini-pumps. It has a decent working time before it kicks, at least at temperatures of 75-80 degrees. It is rather thicker than the West System 105/205 epoxy. It is roughly the color and viscosity of honey. It is just a little harder to wet out glass with, in my opinion, but not much.

So far my repair looks good and seems to be holding up well. From my experience and what I have read and heard about G-flex, I don’t see that it would have any advantage over 105/205 for repair of a fiberglass or fiberglass/kevlar boat.

There are possible advantages
when doing repairs to composite boats with cloth. One, as mentioned above, is that G-flex has superior adhesion. Given that resins are known to stick to Kevlar just a bit less well than they do to fresh glass or other cloths, G-flex may bond Kevlar cloth layers together better and resist delamination. The flexibility of G-flex may also help resist breakage.

Note that West says you can mix a batch of 105/205 with a batch of G-flex and get something that is intermediate in viscosity, intermediate in setting time, and intermediate in flexibility after hardening.

Users should not judge the hardness and flexibility of G-flex from what obtains after only a day of hardening. I have observed additional hardening for at least a week. Possibly G-flex is not the resin to use when you need a full set in a day or two.