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Fibreglass over synthetic stock

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5525f1

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Anyone have experience modding a synthetic stock with fibreglass? Am going to attempt this on a crossman ratcatcher type stock. Those familiar will know the Combe is way too low so my plan is to box it, fill with high density foam, reshape and then layer with fibreglass. Any thoughts?
Cheers.
 
The resin won't stick well to the plastic unless you give it a mechanical "key" to grip. This could be as simple as some deep scratches in the plastic. Easy Composites did an interesting tutorial on covering a biathlon rifle with carbon, I'll have a look for it.


EDIT....
 
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Catweazle said:
The resin won't stick well to the plastic unless you give it a mechanical "key" to grip. This could be as simple as some deep scratches in the plastic. Easy Composites did an interesting tutorial on covering a biathlon rifle with carbon, I'll have a look for it.
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As the plan stands, the fibreglass layers will be placed over the high density foam but either way I will key the plastic surfaces first.
 
Sully said:
There are 3D printed options for a cheek riser, I think @BobP might do one.
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I did consider that option but I’m keen to fill the void in the skeleton stock and completely re profile the whole thing. It’s a spare stock so don’t mind taking a few chances on this.
 
Catweazle said:
The resin won't stick well to the plastic unless you give it a mechanical "key" to grip. This could be as simple as some deep scratches in the plastic. Easy Composites did an interesting tutorial on covering a biathlon rifle with carbon, I'll have a look for it.


EDIT....
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Using CF looks like a great option too.. thanks for sharing.
 
5525f1 said:
Anyone have experience modding a synthetic stock with fibreglass?
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No, but I do have experience with using resins with glassfibre stands, Tape, Sheet, Cross weave, Carbon fibre etc.

So in short, its not so much about fibre glassing or using carbon fibre but more about which resin you use.

What you are after is a strong mechanical bond. The resins you find in your local car shops are usually polyester resins. These have a reasonable chemical bond but not a very good mechanical bond e.g. if you are repairing a car wing you would have to use a wire/plastic mesh to make a sort of sandwhich as the resin wont provide a good mechanical bond to just metal, it'll stick, but it's not very strong. It sticks to itself very well when it hasn't fully cured (chemical bond) but not so good if it has cured.
Then there is vinylester, much better, but still with drawbacks and doesn't have the full mechanical ability as epoxy resin.
There are very few epoxy producers in the World, but lots of suppliers and it can be very expensive, but then so are the best guns. So if you want to stick something to a plastic, epoxy is your choice. Bare in mind a lot depends on what your stock is made out of, Polypropylene for example wont take glues, resins or sealants. The choice of support for the resin is your next encounter.

I wouldn't use fibreglass mat/strands, its not easy to work small areas, your best bet is tape or a weave, more easily bent round tight curves and will wet out much easier than mat.

Hopefully your stock is made from something like ABS plastic, which if roughed up enough should give you a really good bond. Also bare in mind epoxy is very fussy with proportions and temperatures. However if you get them right you are on a winner.
 
On Target said:
No, but I do have experience with using resins with glassfibre stands, Tape, Sheet, Cross weave, Carbon fibre etc.

So in short, its not so much about fibre glassing or using carbon fibre but more about which resin you use.

What you are after is a strong mechanical bond. The resins you find in your local car shops are usually polyester resins. These have a reasonable chemical bond but not a very good mechanical bond e.g. if you are repairing a car wing you would have to use a wire/plastic mesh to make a sort of sandwhich as the resin wont provide a good mechanical bond to just metal, it'll stick, but it's not very strong. It sticks to itself very well when it hasn't fully cured (chemical bond) but not so good if it has cured.
Then there is vinylester, much better, but still with drawbacks and doesn't have the full mechanical ability as epoxy resin.
There are very few epoxy producers in the World, but lots of suppliers and it can be very expensive, but then so are the best guns. So if you want to stick something to a plastic, epoxy is your choice. Bare in mind a lot depends on what your stock is made out of, Polypropylene for example wont take glues, resins or sealants. The choice of support for the resin is your next encounter.

I wouldn't use fibreglass mat/strands, its not easy to work small areas, your best bet is tape or a weave, more easily bent round tight curves and will wet out much easier than mat.

Hopefully your stock is made from something like ABS plastic, which if roughed up enough should give you a really good bond. Also bear in mind epoxy is very fussy with proportions and temperatures. However if you get them right you are on a winner.
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Huge thanks for your InDepth reply On Target, there’s a bag load of info for me to get to grips with and exactly what I was looking for. Points about types of resins and use tape instead of mat may have saved me some headaches.cheers bud👍
 
Just for your info, there is a primer you can apply to the plastic to help bond the polyester resin.
I think it is by prymax.
It is prymax GRP primer.
I would still rough up the surface with 40 grit to get a good key on it.
And after keying up with the 40 grit you need to clean with acetone( to clean off any grease or other contaminant) then apply grp primer then after it is tacky start resin lamination.
The instructions on the grp primer say to wait till tacky.
Cheers Maz.
 
maz1 said:
Just for your info, there is a primer you can apply to the plastic to help bond the polyester resin.
I think it is by prymax.
It is prymax GRP primer.
I would still rough up the surface with 40 grit to get a good key on it.
And after keying up with the 40 grit you need to clean with acetone( to clean off any grease or other contaminant) then apply grp primer then after it is tacky start resin lamination.
The instructions on the grp primer say to wait till tacky.
Cheers Maz.
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Spot on Maz, I’ll check it out 👍
 
Have a look at epoxy glass clothing model aeroplane wings.
Some suppliers do small quantities of resin and woven cloth as a kit.
 
maz1 said:
The instructions on the grp primer say to wait till tacky.
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There are lots of primers on the market to help Polyester resins stick and Polyester is certainly a lot cheaper than Epoxy and not as fussy with the mix either. As I said these Polyester resins don't have a good mechanical bond but do have a good chemical bond which is why a primer is used but has to be still wet to get a good chemical bond. The bond is then only as good as the bond formed by the primer.

Luckily in your case, strength in the bond is not a massive issue.

I quite like Jimmypie 's idea and as he says a lot quicker and easier and absolutely less messy and cheaper. Mind you, take a look at some of @Tillygti6 videos, he makes stonking socks.
 
A std car body filler (polyester) will stick to most plastics once the surface is sufficiently roughed up, however, it will be trial and error as some plastics just don't stick, otherwise, it will be ideal for building up a cheek riser.
 
Just for some context, current plan is to wrap the whole thing in fibreglass thereby forming a rigid shell all around it. If for whatever reason the bond wouldn’t be perfect would it really break away?
I’m new to using these materials but don’t see how it can’t work.
Just a quick thanks to all contributing with ideas.
 
If you do wrap it completely then it will be a complete monolithic piece and it should stay completely together.
To get a smoother surface you can use tissue ( still made of glass) it is very fine and light ,it helps hide the chopped strand matting.
Or you can build up layers and then sand back to a smooth finish.
 
Fiberglass again is compatible with some plastics and others has bonding problems just like polyester it will be a case of suck it and see.
Just how much of a rise do you need, if it's not a lot then try polyester filler first if it bonds OK then it's just a case of adding the required height and sanding to shape and then spry a suitable colour.
 
The plan from the start was to use high density expanding foam which I believe will bond with the plastic part. Ive made a box/ mould for the stock to sit in for this part. Then profile accordingly slightly under size in all the dimensions. Following this I’ll then apply the fibreglass. Basically this gives me as many goes as I need to end up with the finish and shape I’m after.
Not really keen on adding kydex or anything to the existing shape. This is my own next level project. Waiting for resins and other materials to arrive atm plus I’m painting the house windows while I think about other things…😂
 
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