Epoxy for bedding or repair

ejg

Well-Known Member
Heym SR20,
I mostly use a more or less aero-space approved laminating resin
from a company R&G in germany. They have one of the greatest selections of resins and reinforcement materials. Their website is also in english and has a shop.
What's important is to have a nice long pot life with the epoxy mix, otherwise it just becomes a rush job. I use between 40 and 90 min type.

Filling the webs in a fore end of a plastic stock can be done by mixing ultra light micro balloons with resin and the covering with woven glas or
carbon.

For bedding one can use ground carbon fibre, short glass fibre or aluminium powder. Nice thing is one can mix all or whatever one wants.
The viscosity can be adjusted to the job.


rgds
edi
 
sorry edi
is there any chance you could put a step by step idiots guide on bedding from start to finish so i can take notes for further reference please
many thanks stone
 
Stone, I don't have any decent photos at the moment, but
fairly soon I'll do a friends ruger in 6.5, I'll take the camera along.
Bedding rifles is described quite well on some websites, what one doesn't see too often is the reinforcing of the fore end while bedding.
Any-way I do it one way, doesn't mean its the best method.

edi
 
thanks edi
does not hav to be the best method just a reliable one , as you can see there are more than just one person interested and many more who will be looking from the side lines , what works for you may not be right for others but atleast i and others will of gained more knowledge than we had before
many thanks
stone
 
Do you stiffen up the forend at the same time as bedding the action. Or do you bed the action, then hollow out the forened and then stiffen it.

Do you fully bed the barrel, or leave it floating by use some tape etc on the barrel whilst bedding it.

Looking forward to your posting with the Ruger.

Many thanks

Heym
 
One of the biggest problems is that most jobs turn out bad because the wrong materials are used. We can’t really expect to get a good job done with rough boat repair or a car repair kit.
From the aerospace industry we could take over some very suitable materials.
One could split the materials into, reinforcing materials, fillers, resins and
release agents. I’ll go through one by one. For some of you it might be nothing new.

I’ll just start with the reinforcing materials for now. Glass/ Carbon/ Aramid fibres.

When it comes to woven materials one big difference is the type of weave. We mostly are able to pick up plain weave glass fibre somewhere, problem is this stuff is not nice to work with, it will not drape around corners and fold up badly. Secondly some nasty glass sold in boat shops are very stiff because of a finish applied to hold the fibres in place, this finish breaks down with the styrene of polyester but not with epoxy resins.

Since we need very little reinforcement fibres, we might as well use the right ones.
They don’t have a shelf-life and left-overs can be used years later.

Twill or Koeper woven reinforcement materials are very nice to work with, they drape around corners really well. Atlas woven material is going a bit over the top but is also nice to work with.
Twill compared to plain is: stiffer, stronger, nicer to work with.

From the pictures:
Roving: is like a bundle of hair, can be laminated with resin exactly where strength is needed. Like wood fibres, except one can control the direction. Strength and stiffness is of course only in one direction. Great for laying in corners or repairing for example a cracked wooden stock inlet. (comes on a roll)

Unidirectional tape: is like a couple rovings held together in one direction. Very good to get up down strength and stiffness into an forend. Very little torsion strength. (comes on a roll in different widths)

Strand: really nice to work with, mostly very little cutting needed. The width can be adjusted a bit by pulling or compressing . The angle of weave perfect to give a very torsion stiff laminate. Very good in conjunction with unidirectional.
If one only wants to buy one fibre too stiffen a forend, a roll of this kind of strand would do. (comes on a roll in different widths)

Hose 45 deg: a bit special: I’ve used it before to stiffen the outside of a forend. It’s a tube of fibre which tightens up or tightens around something when pulled at the ends. Good torsion stiffness.

Fabrics: are sold by the square meter, either folded or on a around meter wide roll. Sometimes awkward to cut small pieces, and even more awkward if one wants the fibres to run under 45deg because of the wastage.

160g/m2 Atlas hollow fibre. Something very new, the hollow fibre can only be done with glass. Expensive but good vibration dampening, good strength, insulates a bit.

Except for the hollow fibre all these can be had either in carbon, glass or aramid (Kevlar)

Carbon: is the stiffest by far, strongest in tensile and compression, light weight. Nice to work with, easy to cut as a fibre and easy to sand as a laminate. (expensive)

Aramid: only advantage would be in a crash situation, holds together after broken. Not nice to work with. Not good on compression. Not nice to sand once laminated. (Stay away) (expensive)

Glass: very good all-round. Performance can be very good with high quality glass and good laminating resin. (Relatively cheap)

Weight or thickness. For small repairs and forend stiffening glass at 100 – 300 g/m2 . Carbon max 160g/m2. The thicker or heavier the more difficult to work with.
Rather 2-3 thinner layers than one thick one.

edi

glasfabric.jpg

glassroving.jpg

carbonfibres.jpg
 
Fillers:
Used with epoxy laminating resins.
All these fillers can be blended to adjust to what is needed.

Either to increase viscosity of the resin or to fill a void and achieve compression strength or make a putty to smoothen a surface.

Talcum: Makes the best putty, quite easy to sand, doesn’t clog the sandpaper, very smooth surfaces can be achieved. With epoxy doesn’t shrink when curing. Can be substituted at a push with baby powder. (gives a nice smell when sanding)
Low strength. Quite heavy

Glass bubbles: lightest of the fillers. Would be ideal to fill the webbing on these plastic stocks, before a layer of glass. Very easy to sand, surface quality not very good. Low strength.

Milled Glass 0.2mm: good for filling tight corners where good strength is needed. Quite heavy. (Milled carbon also available)


Chopped glass 4.5mm: Filler with good strength but not nice to use on small dainty jobs, can get messy. (chopped carbon also available)

Not on the photo, aluminium powder. Good compression strength and good heat transfer, not as strong as with milled glass.
For a bedding job I mostly blend something like : 1 part talcum, 2 parts aluminium and 2 parts milled glass.
Milled glass on its own would be very good too.

fillers.jpg
 
thank you for you time and effort to post this edi
i hav now written it all down for future reference to look back at and now await the ruger instalment,as i am sure there are many others too who are thinking the same as i
many thanks once again
stone
 
I hope I'm not boring the titts off you,

At this point I’d like to add that if a rifle just needs a small bedding job without forend reinforcement in a good stock, one can also use premixed steel epoxy or similar. These epoxies already filled with metal powders and ready to use. I think Devcon or Araldite make them. Should be available in engineering supplies stores. Important is not to get the quick setting types. Rather 24hr cure time. The disadvantage is that one can’t influence the viscosity of the mix.
(But one still needs to sort the release agents)



About Resins & hardeners:

Laminating resins should be quite thin flowing which makes it much easier to wet the fibres, the thinner flowing it is the more fibres can be loaded and is therefore stronger.

Often one type of resin can be used with different hardeners and these hardeners dictate pot life, viscosity and performance of laminate. (temperature resistance)

For bedding jobs we need epoxy that has a pot life of at least 30 min, nice and thin flowing at normal room temperature, and cures at normal room temperature.

Mixing. Some resin manufacturers state mixing ratios in weight some in volume, since the density of hardener and resin differs, volume and weight ratios are not the same.
R&G Resin L and Hardener L would be 100 to 40 weight ratio or 100 to 45 by volume.
For small jobs syringes work a treat for volume measuring. Epoxy wants to be mixed very precisely.
Also stirring epoxy must be done much more intense than for example polyester resins.
Only add fillers after mixing resin and hardener.

H&S:
-use latex gloves,
-do not smoke
-fumes are heavier than air. If you have an extractor, best from below.
-if the fingers turn red .. pack up, your allergic

Normally, working with small quantities every now and then is not problematic.

Cleaning up.
If the resin has not started to cure, one can clean brushes and hands quite well with hot soapy water. Acetone also works very well.

Release agents:
Some people use shoe polish. I’ve not tried it. But if it’s wax based it should work.
If the release agent fails, then you have a real problem.
One system that works very well and is reliable: Priming wax and PVA film release agent. (They are tailored to work together)
In the case of a bedding job, one would apply a thin layer of wax onto all the metal of the rifle, screws and possibly on the outside of the stock. I rub wax over all of the barrel and action, just in case a drop of epoxy gets onto it. After the wax has dried (1-2 min) one can paint a layer of PVA onto the complete action, barrel, screws and outside of stock. Dries in about 15 min. The trick is that the epoxy glues to the PVA but the PVA comes off the wax very easy. The PVA will dissolve in water can be washed off very easily.

edi
 
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