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Old 10-30-2014, 02:05 AM   #21
Jonty

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Hi Mike, did you see the links I put in post #19? Breadwrap is the generic name given to cheap perforated release film, named as such as it looks like the packaging from bakeries. It has about twice the perforation of P3, is thin so conforms easily, but is not hugely flexible.

Since I'm not especially flush at the moment I don't want to buy any new materials, so I'll going to give it a try with exactly the same setup as before, but winding the vacuum right back as advised by the EC guy, and see how that goes.
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Old 10-30-2014, 04:46 AM   #22
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Ok thanks,had visions of an old bread bag with holes in it.
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Old 10-30-2014, 05:04 AM   #23
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nah, though that probably wouldn't yield a result any worse than I've had so far...!
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Old 10-30-2014, 08:30 AM   #24
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I was just reading over the thread and though I primarily infuse parts these days, I do still use wet layup and vac bagging for some parts, primarily high heat parts where I use a thicker epoxy.
Here's just a couple thoughts that may or may not help.
For one thing, I found that the cured surface coat really doesn't do you any good until you're able to make good parts without it. Basically if you have voids without the surface coat, you're going to have them with it albeit under the surface coat where it's much more difficult to repair.
I think another mistake many, including myself, have made is imagining that if you really load up the resin, it will fill in void areas and at least give a better part. In fact I've experienced the opposite as I think you have. Just piling on more resin actually makes it more difficult to get a good part so I would recommend keeping your resin content closer to the desired end result.
I know this sounds cheap, but often times when I'm trying out a new part with wet layup, I'll just use .7 mill plastic drop cloth (without holes) as a release film. After laminating the wet fabric I'll just lay some of the plastic on top and squeeze out much of the air by hand and then if there are some areas trapping air just use a small blade to add tiny holes for it to escape. Then add your breather and bag like normal.
Once you get a reasonable part you can then start trying things like perf release film and in mold surface coating.
I don't know if this will help but I know that if you stay with it and learn from others and your own mistakes, you'll get some good parts soon.
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Old 10-30-2014, 11:35 AM   #25
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I am guessing that you have tried the part again....There are a couple of other things you can do if not.

Firstly, don't use the gel coat, as it's not helping.

I nearly always do wet layup using plastic as a backer.

I will explain-

Get some cheap thin plastic 50-75um (micron) which in real terms is about as thick as the vac bag you are using, but much cheaper.

You can use 3M masking film, or even shopping bags but it's a little harder!

The plastic is stretched lightly over a flat table and taped out so there are no creases. Ensure there is enough area for all the layers.
Lay the fabric out on the plastic.
At this point I become very fussy about ensuring the weave of the RC200 is not wavy or distorted, and tease out any imperfections.
Wet out the fibre with your chosen resin.. I use plastic squeegees to do this as once the fibre is wet out you can apply additional pressure to remove the excess and even out the resin content. Rollers work, but can airate and mar a cosmetic carbon layer.
Pool some resin in the centre of your fibre. Using the squeegee divide the pool of resin and sweep it out with one direction of the fibres.. Ie @0 or 90 degrees.
Go back to the remainder of the pool and sweep it out the opposite way to the first sweep.
Apply some more resin and this time do the same but at right angles to the first.
You have made a cross of resin that has secured the warp and weft of the fabric.
Carefully wet out the rest of the cloth with the residual on the plastic and by adding as necessary.
When you are content with your wet out, it is even and not excessive, untape a corner or two.
Carefully lift up the plastic to view the underside.. You should clearly see the fabric is wet and contains no dry patches etc.. If it does remedy them now.
Cut the plastic around the fabric.
The plastic is then a transport film like prepreg backer.

(Note: If I am making parts with complex shapes or a large number of plies, I will template the plies and nest the shapes onto a second plastic layer. Lay this ontop of my wet out fabric.. Then cut out through both layers and the carbon at the same time.)

Back to it...Apply a thin layer of resin into the mould
Then bring the wet out fibre to the mould and lay it down plastic side up.
Being as your first ply is at 0/90 I would start working the fibre into the mould up and down the centreline then moving out wards.
Once the rigidity of the plastic is working against you, begin to remove it. It will peel up away from the laminate quite easily.
Use A small dry brush to help tease the fibre off if you need too. Avoid lifting the fibre out from the mould or distorting the fibres as you peel.
Using a dry brush, gently stipple and work the first layer into your mould. No need to add resin as you should have plenty already.
When you happy the first layer is down and not bridging in the corners, bring over the second layer and repeat. Then the third and so on.
No need to be as anal about distortions with the subsequent layers, just be mindful that you may be moving the first ply underneath with the upper layers and that will be visible in the end result.

Now: Vac stack...
If any part I am laminating has complex or compound curves, I will cut the peel ply on the 45 degree bias.

Really seems to help with both bridging and wrinkles.

Rule of thumb- All internal radius' should have a slip joint. I.e: The peel ply is cut and then a second piece with an overlap is added.
This apples to the perf film too, so I like to pre apply the peel ply and the perf together with spray glue (3m 77) and then you cut down on the time it takes to lay your vac stack by laying both at the same time..
The breather should be able to stretch and allow for small contour variations... But if in any doubt, cut it and add a slip join..

Pop your part in the bag and pull the bag down with the pump moving the bag into the internal radius' until it is just about to start 'pulling'. You want most of the air evacuated, but still be able to move the bag easily.
Rule of thumb- you need a fold or pleat in all the internal radius' and try to eliminate any folds on external corners. This will help the bag pull into the corners and stop unsightly wrinkles on external.
Then apply more vac, turn off and check the bag.. Repeat until you are at your desired vacuum.

For a better assessment, it would be useful to show a few pics of the part in its bag.

The Perf you are using - P3, is okay for wet layup... But only just.

Perforated films are graded in two ways - 'Open area' and 'hole density'

Hole density is the spacing of the perforations
Open area is driven partially by the density, and by the perforation size and is the total area of all the holes added up in 1m2 giving you a better idea of how easily resin will flow through.

My preferred is by Airtech and is P31 which has a hole spacing of 25mm which is less density and open area than P3

As P3 is less than ideal, you need to be careful applying too much vacuum, or in this case I feel your applying it much too soon.

Lookup the gel time for the resin you are using. For cosmetic parts, you want to be applying vacuum very near the time the resin begins to gel.

This will give the resin less flow time - and will keep the resin where you want it.

Forgive the marathon post, and I hope it makes sense. If I had some pictures, I would have posted them as it would have saved me writing it all..

You can try this method on scraps to see how you go.

Good luck!

Last edited by Astute; 10-30-2014 at 11:54 AM.
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Old 10-30-2014, 11:51 AM   #26
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Also if cash is tight - use glass in the intermediate plies. It's a trick used by mass manufacturers - first two plies ideally would be carbon, but the rest can be glass just to make up the thickness.

Just depends where the part will be used.
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Old 10-30-2014, 02:35 PM   #27
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Quote:
Originally Posted by RogueSe7ens View Post
some good advice to drop the gelcoat and not load the resin so heavily
Thanks for these pointers, I'll forget the gelcoat for subsequent attempts. Since being advised to turn down the vacuum I've realised that most, if not all, of the bridging is from having resin pooling and preventing me getting the carbon in contact with the mould, but then this resin is pulled out by my high vacuum, leaving the void. I'll go much more sparingly tomorrow when I laminate again at only 5in vac.

Quote:
Originally Posted by RogueSe7ens View Post
I know this sounds cheap, but often times when I'm trying out a new part with wet layup, I'll just use .7 mill plastic drop cloth (without holes) as a release film. After laminating the wet fabric I'll just lay some of the plastic on top and squeeze out much of the air by hand and then if there are some areas trapping air just use a small blade to add tiny holes for it to escape.
This sounds similar to asute's suggestions, I'll be giving this a go!

Quote:
Originally Posted by RogueSe7ens View Post
I don't know if this will help but I know that if you stay with it and learn from others and your own mistakes, you'll get some good parts soon.
Thanks for the encouragement, my brother and I have been renting our workshop for just over a year now, and finally we have the car ready to go on track on 22nd Nov, and are getting closer to having some parts made... I have a feeling that we will be switching to infusion and/or prepreg in the future, but I think we need to have a solid grounding in all techniques to stand a chance of eventually mastering composites.
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Old 10-30-2014, 03:32 PM   #28
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Quote:
Originally Posted by Astute View Post
lots of good advice .
Thanks very much for taking the time to write such a detailed post!

With using the squeegee and plastic film, this is something we have done before, but doubling the plastic over and squeegeeing through the film. Is this an ok technique, or do you get better results using the squeegee directly onto the carbon and resin? Whilst the vacuum has been too high this masked any positive effect and so it's not something I've been able to gauge yet.

I'll keep my brush dry for laminating to not flood it with resin, and I think a key point from both you and rogue seven is to do more/most of the consolidation by hand.

With the peel ply I will use the 45 deg trick for compound shapes, though in this part it is almost all straight edges and corners, so I'll be concentrating on slip joints. My part is essentially a pair of 20mm wide u shaped channels with a 50mm bulge between, so if I use a piece of peel ply in the bottom of each u section and then a piece on top of the bulge that creates a slip to both channels, will this be adequate? Or should I use a piece of peel ply for each internal radius, I.e. 2 per channel?

The breadwrap I am using is actually about twice the hole density as P3, so from your description this is not ideal for wetlay. What vacuum level would you use with the P31? We've been wellying full vacuum with a very high hole density and open area, so definitely not correct, and it shows, but the 20% vacuum we've been advised to use feels very low, so although I'll go with it for now, in future this could be something to adjust if a different perforation allows us to wind in more vacuum.

I'll try and work all this into my process tomorrow, however I'll struggle to take pics as I go since my brother is away this week, but I'll try and get some more photos of the various stages, especially bagging etc. Thanks for the support!
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Old 10-30-2014, 10:44 PM   #29
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Quote:
Originally Posted by Jonty View Post
Thanks very much for taking the time to write such a detailed post!

With using the squeegee and plastic film, this is something we have done before, but doubling the plastic over and squeegeeing through the film. Is this an ok technique, or do you get better results using the squeegee directly onto the carbon and resin?

yes this is okay, but what I like is to control the resin from the moment it is in contact with the carbon... It's always easier to add more as you need it.

Whilst the vacuum has been too high this masked any positive effect and so it's not something I've been able to gauge yet.

It is not just mow much Vac but when, and if you apply it too early

I'll keep my brush dry for laminating to not flood it with resin, and I think a key point from both you and rogue seven is to do more/most of the consolidation by hand.

Spot on.

With the peel ply I will use the 45 deg trick for compound shapes, though in this part it is almost all straight edges and corners, so I'll be concentrating on slip joints. My part is essentially a pair of 20mm wide u shaped channels with a 50mm bulge between, so if I use a piece of peel ply in the bottom of each u section and then a piece on top of the bulge that creates a slip to both channels, will this be adequate? Or should I use a piece of peel ply for each internal radius, I.e. 2 per channel?

Here laying a 20-25mm strip into the bottom of the channel first and letting the other pieces lap onto it.

It might pay off to divide up the carbon layers a bit too. Have a single cosmetic first layer and then the second and third lay into the mould in smaller pieces with overlaps to help eliminate bridging


The breadwrap I am using is actually about twice the hole density as P3, so from your description this is not ideal for wetlay. What vacuum level would you use with the P31?

80-100% but only after waiting for 2-4hrs for the resin to tack up

We've been wellying full vacuum with a very high hole density and open area, so definitely not correct, and it shows, but the 20% vacuum we've been advised to use feels very low, so although I'll go with it for now, in future this could be something to adjust if a different perforation allows us to wind in more vacuum.

Try a double layer of perf, and keep up the vac. 50% is about a s low as I like to go...;-)

I'll try and work all this into my process tomorrow, however I'll struggle to take pics as I go since my brother is away this week, but I'll try and get some more photos of the various stages, especially bagging etc. Thanks for the support!
Good luck!

Last edited by Astute; 10-30-2014 at 10:49 PM.
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Old 10-31-2014, 02:42 AM   #30
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Thanks for those pointers.

I think I'll play the vacuum level by ear to a certain extent - I'll double the perf film and see whether 20% does anything for me, or if I need to wind it on a bit. I certainly won't be using 100% initially. I'll have to laminate then scarper, so unfortunately I won't be able to increase vacuum later - but I'll add this to the to-do-list for next time.

With the peel ply I think I'll add an extra slip joint - each piece will go over an external then internal radius, so these two corners won't pull against each other.

...photos to follow for you guys to critique once I can get out of work and have another try at this!
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