Howa Mini action - Carbon Stock Project

The alternative title "A rough bastard learns about composite materials"

Background:
I've been thinking about making a CF stock for a couple of years. Reading books on fiberglass boat building and reading technical manuals on carbon fibre filled in many hours in the evening.

12 months ago I made a fibreglass stock from a plug of my own design, inspired by the good work of @Robojaz

For want of a better option I went about trying to fit it onto a JW15. That was a disaster, ended up heavier than the factory wooden stock with loads of pock marks and voids. They say you learn from mistakes so I must have learnt lots.

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The Howa Mini.
The factory stock has been described as a "fat heifer of a thing"
Like a few others have done I took to it with power tools and edited the shape.

Factory shape
Attachment 177174

Chop chop
Attachment 177175


Not being a savage from Southland, I glued the factory foreend back on.

Then went about making a mould. Cut the shape out of your parting board (melamine in this case, it was free)
Plug up all the edges with modelling clay. Doing this takes about 2 hours more then you would expect.

After reshaping
Attachment 177178


Attachment 177176

Attachment 177177

Attachment 177179
The wee pyramids are so the second half of the mould has something to locate onto.



Then the plug and parting board get waxed up to help prevent being glued together.
Cover the thing with a tooling gelcoat. The gelcoat I got came in a lovely shade of red.

Attachment 177180


Any abrupt edges I filled with a thickened resin. This is because fibreglass really hates going around sharp corners. I wanted the edges to be as neat and defined as possible.

Attachment 177182


When that's got to a nice tacky stage the layup of chopped strand mat could commence!
I only used about 4 layers of chopped mat in total. Lots of poking with the brush to get things together nice and firm. At this point I'm not worried at all about weight so used plenty of resin. From experience having a resin rich coat on top makes it much nicer to handle the mould without getting jabbed by any tiny bits of glass poking out.

Attachment 177184

Do one side, leave for 24hrs, pull the parting board off, apply another 6 coats of mould wax, tooling gelcoat, thickened resin, more chopped strand mat.
By this point you realise making mould's sucks. You also know it's the most important step really. Any fcuk ups here are really hard to fix later on...
Eventually you end up with a stock encased in fibreglass.

Attachment 177185

I managed to get the 2 halves apart with the use of some ice block sticks. Basically just slide/knock them in like wee wedges.
It's quite a relief when the mould finally cracks open without breaking anything!

Attachment 177186

With the nice new mould I then took to it with the cutting disk on the grinder. This was to square up the edges and expose the action area. The exposed action area idea of mould making I got from @stug

Attachment 177187

Attachment 177188

Mould got cleaned up with hot soapy water then another 6 coats of release wax to each side before letting it sit overnight.

Attachment 177189

It's now carbon time!

Attachment 177191

I was given a can of spray adhesive from the local carbon fibre chap when I was having a beer with him and asking silly questions.
This made life bit easier with getting the carbon cloth in all the wee corners.
I was a bit rough at some point with the cloth and loosened the weave up on some areas. Oops.

Attachment 177193

I put in 2 layers of carbon cloth for the body and 4 layers around the grip/wrist area.
As I don't have a proper vacuum pump I used a big clothes storage bag. Layer of peel ply over the carbon, bleeder fabric then bagged up the whole mould.

Attachment 177194



This is the point I'll leave you waiting for the next instalment.

Looks like a great project, waiting in anticipation for the rest of the build.

Looks bloody good. When I was making mine I did 4 layers of 200gsm carbon fibre and another 3 layers through the pistol grip area.

Awesome work, what is your plan for joining the two halves together? Are you going to do any fill in the buttstock/forend areas to reduce to hollow sound?

Quote:

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Originally Posted by SixtyTen

Awesome work, what is your plan for joining the two halves together? Are you going to do any fill in the buttstock/forend areas to reduce to hollow sound?

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best thing would be to glue a hip flask in the butt stock, fill to the brim of the spirit of your choosing and enjoy. just need to make sure you finish it all so it doesn't slosh!

Quote:

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Originally Posted by SixtyTen

Awesome work, what is your plan for joining the two halves together? Are you going to do any fill in the buttstock/forend areas to reduce to hollow sound?

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The 2 halves of the mould are bolted together and then 2 layers of cloth laid over the join. I think I've cocked up here but will see what happens.

I'll fill the hollow shell with spray can expanding foam. I know there are better products to use that will make a nice chemical bond with the epoxy.
In this case I'm relying on it being encased and having a mechanical bond inside the stock. From my first attempt I found filling the hollow areas with foam makes a world of difference.

I used Sika boom expanding foam to fill the butt and fore-end. It has no structural value just sound deadening. Run a bit of water around inside the butt or fore-end first then tip/shake it all out. The water prevents secondary expansion of the foam.

A good method for laminating complicated shapes and to keep the carbon weave from getting all messed up is to get some 3m painters plastic, lay that down on a flat table and tape it out so there are no wrinkles. You then lay your cloth on that, mix up your resin and use a squeegee to spread the resin over the cloth and allow it to soak in. You can then squeegee the excess off so the cloth is not saturated. You then put another layer of 3m plastic over this and now you can use your patterns to mark out (on the plastic) the bits of fiber you need and cut them out with scissors. You then peel one side of the plastic off, lay your fiber in the mold in mostly the right place, remove the second layer of plastic and use a paintbrush (the cheap chip brushes are perfect for this) to tamp the fiber into place. Rinse and repeat until all your layers are in, then peelply, release film and breather and your into your bag.

Its a very good way of doing complex wet laminates. Kind of similar to prepreg lamination in that you can control all your overlap distances and patch sizes quite carefully.

If you want to get really fancy, you can weigh the fiber that you plan to use, divide that by the fiber to resin ratio you are shooting for and add 10% for peelply. You then only mix and use exactly that much resin for the job. You can get as low as 26-28% resin this way, which is comparable to pre-preg. Gives for a lighter and stronger product so long as you get complete wet-out, which can be challenging depending on the resin type and ratio you are trying to achieve.

Quote:

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Originally Posted by SixtyTen

A good method for laminating complicated shapes and to keep the carbon weave from getting all messed up is to get some 3m painters plastic, lay that down on a flat table and tape it out so there are no wrinkles. You then lay your cloth on that, mix up your resin and use a squeegee to spread the resin over the cloth and allow it to soak in. You can then squeegee the excess off so the cloth is not saturated. You then put another layer of 3m plastic over this and now you can use your patterns to mark out (on the plastic) the bits of fiber you need and cut them out with scissors. You then peel one side of the plastic off, lay your fiber in the mold in mostly the right place, remove the second layer of plastic and use a paintbrush (the cheap chip brushes are perfect for this) to tamp the fiber into place. Rinse and repeat until all your layers are in, then peelply, release film and breather and your into your bag.

Its a very good way of doing complex wet laminates. Kind of similar to prepreg lamination in that you can control all your overlap distances and patch sizes quite carefully.

If you want to get really fancy, you can weigh the fiber that you plan to use, divide that by the fiber to resin ratio you are shooting for and add 10% for peelply. You then only mix and use exactly that much resin for the job. You can get as low as 26-28% resin this way, which is comparable to pre-preg. Gives for a lighter and stronger product so long as you get complete wet-out, which can be challenging depending on the resin type and ratio you are trying to achieve.

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Thats really good to know thank you! For the first layer in I used the spray adhesive, the theory being it would be easier to get the cloth into shape.
The subsequent layers I laid in sections with pre wetting the cloth similar to how you described. I cut the rough shape before putting resin on to soak in,

Ahhh, finally I get to see the stock coming to life, that's a fairly involved project @Joe.......... Might be finished next time we catch up....don't eat all the bloody chocolate biscuits either next time.:XD:

farken primo!

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Originally Posted by ANTSMAN

farken primo!

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You could do that.

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Originally Posted by Tahr

You could do that.

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I could eat all the chocolate biscuits :yaeh am not durnk:

Quote:

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Originally Posted by viper

Ahhh, finally I get to see the stock coming to life, that's a fairly involved project @Joe.......... Might be finished next time we catch up....don't eat all the bloody chocolate biscuits either next time.:XD:

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Who shows up 3 weeks later expecting chocolate biscuits to still be there. Honestly.

Right, I left you with the carbon mould being closed up to stick the 2 halves together.

Attachment 177407


I pulled the mould apart after work this afternoon and convinced the stock to pop out.

Attachment 177408

Yeah. That's pretty ugly. Gave it a quick trim and it looks like this now:

Attachment 177409



Where I've cocked up.
There are patches where I was too light on the resin with the first layer and didn't get a full wet out.
I don't think that's the end of the world, I can effectivly give it a clear coat of resin on the outside. Not ideal but I can't think of a better option at the moment.
Demoulding was a bastard. Think waxing the mould over a couple of days next time then a couple of layers of hairspray as a release agent might be the go.

Whats worked well.
I got the carbon in all the fiddly places really well!
I neglected to take a photo of the nice bits around the grip and bolt cut out, sorry. I reckon it looks the part.



My next step is to make the barrel channel.
This will involve some PVC conduit and possibly swearing quietly to myself.
I'll mould the outside of the PVC so the barrel is free floating by a mile. The first 50mm or so I'll just bed with epoxy when I put it all together.

Attachment 177410

Attachment 177411

Just bed the first parrallel section of the barrel, you don’t need to go any further.

Quote:

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Originally Posted by stug

I used Sika boom expanding foam to fill the butt and fore-end. It has no structural value just sound deadening. Run a bit of water around inside the butt or fore-end first then tip/shake it all out. The water prevents secondary expansion of the foam.

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Hey @stug would this foam work to fill a mould and still pop out? Or any idea what foam type Sako would use?

C uv just about finished my new stock m8 haha

C uv just about finished my new stock m8 haha

@Freezer no idea sorry. It would probably stick would be my guess

Quote:

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Originally Posted by Padox

C uv just about finished my new stock m8 haha

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Yeah yeah. Let me finish it before you get to field test and see where it breaks.

Quote:

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Originally Posted by Padox

C uv just about finished my new stock m8 haha

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@Padox , I wouldn't get your hopes up mate, he promised me biscuits and they never turned up. Then just to rub it in he informs me they were double choc TimTams..... ate the whole packet himself.

Sounds like Joe all over haha

Looking good. Be interesting to see what weight is at the end.
@stug is that how you used to join your 2 halves together or did you trim the flanges back so that butted end on?

I had mine in the vacuum bag for about six hours, then trimmed the sides flush with the mold. Then joined the two halves together.

Quote:

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Originally Posted by stug

I had mine in the vacuum bag for about six hours, then trimmed the sides flush with the mold. Then joined the two halves together.

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Cheers. That's what I plan to do with my next one. I don't think my mold would work with the flanges left on

Quote:

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Originally Posted by stug

I had mine in the vacuum bag for about six hours, then trimmed the sides flush with the mold. Then joined the two halves together.

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Yeah that's the way to do it Remmodel7, will leave a tidier job and be easier to break out of the mould.

Is anyone selling a vacuum pump by chance?

Quote:

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Originally Posted by Joe_90

Yeah that's the way to do it Remmodel7, will leave a tidier job and be easier to break out of the mould.

Is anyone selling a vacuum pump by chance?

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Fridge or freezer compressor. One line blows and the other sucks. You can make super quiet low volume air compressors or vacuum pumps from them. Super handy.

A vac pump from one of these pulls a really good vacuum but has very low volume, so you need a well sealed bag and may need to evacuate most of the air with a vacuum cleaner or similar.

Yes this project is still on going.

Not finished yet though.... Still need to make it heavier.

Attachment 181053

Quote:

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Originally Posted by Joe_90

Yes this project is still on going.

Not finished yet though.... Still need to make it heavier.

Attachment 181053

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thats plenty heavy enough :thumbsup:

Haha it still has to handle field usage Danny. Another 120g or so will be worth it.