C-Forum

I haven't messed around with this stuff much yet, so i don't quite know its capabilities, but in theory I was thinking could you glass in thigh strap anchors into a plastic boat.
previously I have layed down a layer of foam on the boat then glassed over that with epoxy which adds a bit of height all around with the foam and glass
Could you lay glass cloth straight to the plastic?

I saw a procedure for that, including flaming and all, but for thigh straps I'm sceptical that G-flex can hold to poly. On poly boats I have routed the thigh strap anchors through a hole low in the center wall. This works best if the pedestal seat is continuous with the front and rear walls.

Yes, you can gflex anchors in, use additional fiberglass or other composite cloth though to distribute the load of the anchors. That stuff is amazing and is a mainstay in my boat outfitting and repair arsenal.

A few people around here tested it out and it has not been working very well. Crack repairs failed instantly. Thigh strap anchors failed after a few days. All done by the book.
It just don't stick.

I've had a different experience than what Larry describes... so it might depend on how it is used, applied, and if you do or do not use glass to re-inforce. The epoxy alone without glass is almost useless, but now that the industry has developed an epoxy that will bond to plastic, there's no reason not to add glass to your crack repairs. I have used the gflex to very successfully repair cracks in cross-linked boats.

For anchors, you still need to distribute the load with glass and if you can, you should try to put weight on top of the anchors, like your pedestal or a rail or something to take some weight off of the gflex anchors.

While everyone may not have the same success with the product, I've been very happy and use it all the time. I think part of my success with gflex has been making sure it spreads over a very, very large surface area of the plastic it comes in contact with.

do you do anything to prep the plastic before laying the glass and gflex down?
do roughen up the plastic if so how do you do this with best success?

Yes, I regularly refer directly to the West System website when I use gflex for different applications... but yes, absolutely rough it up and I also regularly use the flame treatment they recommend.

See here: http://www.westsystem.com/ss/gluing-pla ... lex-epoxy/

Everything Markzak says makes perfect sense, but I wonder whether Kevlar or polyester might be substituted for some of the glass.

The reason is that, occasionally, you will run that boat over something that distorts the extended cloth/epoxy patches. Using all glass may make cracking, or popping loose, more likely.

Just a paranoid thought.....

Hi,

a) what Plastic??? PP is unlikely to be glue-able with GFlex, HDPE or LDPE will get good adhesion with proper (flame, roughen up & alcohol-wipe, in reverse order) surface treatment

b) the fibre properties vary so be careful about what stresses will be seen in an area to decide what and how much fibre reinforcement is necessary. avoid too much, a stiff repair will likely break! fibres need to be pre-soaked very well, pre-apply some gflex to the plastic as well. use a heat gun to get gflex more fluid and to hades dont use the pasty one but the more fluid consitency when glassing (or kevlaring) stuff in. Dont forget that some fibres flex better than others, those would be recommended. Bevel all edges.

c) surface prepping! surface prepping! surface prepping!
- Alcohol wipe before anything else, and I mean clean it!
- use paper not textiles to wipe, always, fresh and clean paper towels. textiles (that have been washed) likely contain sillicones from washing detergents (ask yourself if YOU need those on your skin, too) especially if softener is used in the same washing machine - not necessarily the same washing process!! very small amounts of silicones will kick nearly every glueing process' butt big time.
- abrade after wiping to prevent dirt to be introduced in the abraded surface
- always use fresh good quality sandpaper (that doesnt loose too much particles in the process) and wipe/suck the dust off
- wear vinyl gloves if you have sweaty hands (I have - they made my day several times before I started doing this!)
- flame treat! there is a comparison chart in a PDF by west system about G-Flex as to what a difference it makes.. for HDPE, it makes ALL the difference.
- flame treat quick and so that it does not leave any visible burn marks. thats enough. lasts 30 minutes so do just before glueing.. if the surface is warm, that helps too (makes the epoxy flow into the structures better)
- think about the abilities of glue.. and design your anchors accordingly. NO glue is good for peeling loads, but G/Flex is better for that than others.

d) you could experiment with anchor plates. The plate has to be thick enough to be able to transfer loads, have a chamfered edge to make sure it distribute the load on the corners widely, and should have no holes. Like, epoxy a plate (regular epoxy with glass, kevlar, whatever, and some small stainless steel pipes glassed in as the anchors) in the shape of the boat surface you would like to glue it down to. (saran wrap would make a good peel layer between that - it can be custom shaped easily that way, in the chines, or whatnot!)
- Then glue that whole thing down with GFlex and make a nice transition with the excess spread out.
- Use filler in the Gflex! Microfibres for example.

Ever after, happy paddling!

Btw, heres what I've been doing with the stuff

http://www.ipernity.com/doc/mahyongg

I used GFlex to glue in vinyl D-rings for a strap system on 2 different conversions. I followed the instructions exactly and very carefully - surface prep, flame treat, proper mixture, blah, blah...

The short story is that it can work. the longer story is that its not perfect: GFlex does not bond to plastic, it just lets the drings stick to it.

In my first conversion I only used GFlex to attach the d-rings for the anchors on the sie of the boat (the bottom anchor was on a PVC pipe which I used for my rail) I used this setup for a complete season with no issues - the Drings are solidly on there, no issues.

In my second conversion I decided to try GFlexing Drings to the bottom of the boat. This did not work. The bottom just flexes way too much to allow the adhesive to stay stuck to the boat, with the upward pressure of the strap trying to pull it off at the same time. A patch starting lifting after a couple runs; I repaired it but again it lasted only a couple runs.
When I pulled the failed patch off there was no gflex residue on the hull - it was all on the vinyl. The same was true when I removed the patch that didnt fail.


Another observation is that a dring that has been glued in with gflex can be easily (and effortlessly) removed with a paint scraper - it just slides between the vinyl and the boat. Which is what led me to my conclusion that there is not bond created with the plastic boat, its just stuck to it...until something will cause it to seperate. So given my experience it can be used - but only in certain situations.

You're right - that example with the scraper illustrates how you have to design the anchors according to what forces the glue can take and which not. Its the best example for a peeling force - once you get the blade under the epoxy, it will lift the sticking part without much effort on your side due to the high upward lever force at work. comparable to pulling a taut rope sideways - anyone here who ever landed on their knees when a helping "comrade" pulled at a tightened throwrope while the swimmer burned their fingers when it started slipping? Same thing. Good thing: that kind of force will be distributed over a waaay larger area usually.

GFlex should stay better in a flexing environment than other Epoxies, but it definitely has its limits. The only thing is, those are probably reached later than most else glues' so its still a viable option.

Another point to consider: Most DRings fail at the stitches first. I now have side anchors in my boat that are two-ply: one layer of PVC tarpaulin with stitched anchor straps hot-melt glued to a layer of tarp thats glued into my spark using flexible contact cement, quite similar to vynabond. So far, there is no release, unlike another anchor thats glued directly to the boat with the stitched part. I am just wondering how long the hot-melt will hold up (its BEMIS Sewfree if anyone wants to try that) but that usually gives a material failure in PVC bonding before the glue fails. Just wondering how much it will resist the water..

Btw. its still all in the anchor design.. some anchors I have seen (including Esquifs - these guys should know a thing or two about boating eh?) are designed to fail. I do not say thats been deliberately done so, but c'mon guys, its simple mechanics!

Pull tight,

Jan