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Warren (Staff) - 7/19/2018 2:59:31 PM

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Dinoman - 7/19/2018 12:43:22 PM

Hi Matt, Thanks again,as you can imagine I have quite a bit of Chopped mat Strand which I have used for my Fibreglassin so can I still use this with your HT Gel and Resin, also my MEKcat is that compatible, as I do not want to mix the wrong one and ruin my Mould etc, what is the polypropylene sheet for ( or is that the corrugated sign board ?) so again Thanks for all the help, Regards DM

  Hi Matt, another observation ??? looking at your Video Making the Bonnet Mould for the 27th time I suddenly realised you did not Vacuum Bag it and especially on the first layer over the Gel Coat which is the most important coat to make sure there was no air bubbles or voids under the gel, as I could understand no reason to VB any further layers, as the Mould is the most important piece to get spot on as hopefully you will be using for lots and lots of Mouldings ?? Regards DM

Which kind of chopped strand matting do you have? Typically there is emulsion bound and powder bound.  Epoxy lacks the solvents required to break down the emulsion binder, so we recommend the use of powder bound CSM as any resin will break the binder much easier.   You will NOT need MEKP for our EL160 and EG160 as both are epoxy based and have their own specialist hardeners that need to be used.

The polypropylene  sheet is for use as a baseboard and to create flanges.  Fluted signboard can be used to do the same thing  albeit the surface finish is slightly ribbed compared to the perfectly smooth finish of pure polypropylene sheet..

Generally speaking, vacuum bagging is not needed for mould making.  Wet lay mould making like  suggested for your project is done without any vacuum bagging.   As long as you pay careful attention to applying the gelcoat properly and the first layer of putty and glass, then you should not have any voids to worry about. 

You may be thinking of  tooling pre-pregs, where depending  on the system used and mould  size, thickness etc, vacuum debulking may be necessary.

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Warren (Staff) - 7/19/2018 4:31:15 PM

When you rub or break by hand a powder pound CSM, then usually you will get a white powder falling off as you rub or break it.

Vacuum bagging is generally not necessary.  For example, the putty if correctly applied, will fill the sharp corners and recesseses - thus no voids.  The laying up of the cloth is then much easier and just requires  good  quality laminating by hand to achieve a void free finish.  So there is little to gain from vacuum bagging that hasn't already been achieved through proper and good quality laminating.

In theory it may well help for very high temperature applications but this is rare and i have not heard of anyone vacuum bagging the moulds even in this situation.

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Steve Broad - 7/19/2018 7:38:24 PM

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Warren (Staff) - 7/19/2018 4:31:15 PM

When you rub or break by hand a powder pound CSM, then usually you will get a white powder falling off as you rub or break it.

Vacuum bagging is generally not necessary.  For example, the putty if correctly applied, will fill the sharp corners and recesseses - thus no voids.  The laying up of the cloth is then much easier and just requires  good  quality laminating by hand to achieve a void free finish.  So there is little to gain from vacuum bagging that hasn't already been achieved through proper and good quality laminating.

In theory it may well help for very high temperature applications but this is rare and i have not heard of anyone vacuum bagging the moulds even in this situation.

I would expand on what Warren said - The important part is getting the gel coat into all the corners and crevices. As this is like a very thick paint when warm, you can't vacuum bag it as it will simply squish all over the place!. You then add the paste whilst the gel coat is still tacky (but firm enough that pushing on the paste doesn't disturb it- correct me if I am wrong Warren or Paul, but I use the fingerprint test, if my finger leaves a print but the gel doesn't come off on my finger it is ready for the next stage) and then add the fibreglass over the whole lot.

For smallish parts I use an old domestic oven bought from eBay. There are plenty on there, here is an example. Simply drill a hole through the side for the vacuum tube :-)

https://www.ebay.co.uk/itm/neff-Electric-oven-You-Arrange-Courier-Or-Collect/323346305953?hash=item4b48f113a1%3Ag%3AKUAAAOSwpz5bR6-N&_sacat=0&_nkw=domestic+oven+electric&_from=R40&LH_ItemCondition=4&rt=nc&_trksid=m570.l1313

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Dinoman - 7/19/2018 8:07:54 PM

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Steve Broad - 7/19/2018 7:38:24 PM

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Warren (Staff) - 7/19/2018 4:31:15 PM

When you rub or break by hand a powder pound CSM, then usually you will get a white powder falling off as you rub or break it.

Vacuum bagging is generally not necessary.  For example, the putty if correctly applied, will fill the sharp corners and recesseses - thus no voids.  The laying up of the cloth is then much easier and just requires  good  quality laminating by hand to achieve a void free finish.  So there is little to gain from vacuum bagging that hasn't already been achieved through proper and good quality laminating.

In theory it may well help for very high temperature applications but this is rare and i have not heard of anyone vacuum bagging the moulds even in this situation.

I would expand on what Warren said - The important part is getting the gel coat into all the corners and crevices. As this is like a very thick paint when warm, you can't vacuum bag it as it will simply squish all over the place!. You then add the paste whilst the gel coat is still tacky (but firm enough that pushing on the paste doesn't disturb it- correct me if I am wrong Warren or Paul, but I use the fingerprint test, if my finger leaves a print but the gel doesn't come off on my finger it is ready for the next stage) and then add the fibreglass over the whole lot.

For smallish parts I use an old domestic oven bought from eBay. There are plenty on there, here is an example. Simply drill a hole through the side for the vacuum tube :-)

https://www.ebay.co.uk/itm/neff-Electric-oven-You-Arrange-Courier-Or-Collect/323346305953?hash=item4b48f113a1%3Ag%3AKUAAAOSwpz5bR6-N&_sacat=0&_nkw=domestic+oven+electric&_from=R40&LH_ItemCondition=4&rt=nc&_trksid=m570.l1313

Hi Steve, Don't get me wrong, but I know the basics as I have been doing Fiberglas for over 30 years, so I have lots of Moulds and am forever repairing then, mainly because they were not made well to start with, none have been Vacuum Bagged, so now I want to start learning the correct way and Materials to do CF, so want to start with Hand Layup and Air dry, and if I get on with then I will buy a large oven to accommodate large panels such as Bonnets, doors, Undertrays, the Ferrari Undertrays are very large approx 6ft X 4.5 ft, so I do not want to run before I can walk, Like I said to Warren the Mould is the most important tool as it is going to be used lots of times, and especially if you have a perfect item to Mould the last thing you want to be doing is repairs to a new Mould, so when I found this Forum I was hoping for some great advice, but when someone says no need to VB your Mould I find it very hard to believe that that is best practice, so anyway I will persevere and try VBing my Moulds, so thanks for all you advice and help, I will let you know how I get on, Regards DM

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Steve Broad - 7/19/2018 8:33:01 PM

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Dinoman - 7/19/2018 8:07:54 PM

+x

 

Steve Broad - 7/19/2018 7:38:24 PM

+x

 

Warren (Staff) - 7/19/2018 4:31:15 PM

When you rub or break by hand a powder pound CSM, then usually you will get a white powder falling off as you rub or break it.

Vacuum bagging is generally not necessary.  For example, the putty if correctly applied, will fill the sharp corners and recesseses - thus no voids.  The laying up of the cloth is then much easier and just requires  good  quality laminating by hand to achieve a void free finish.  So there is little to gain from vacuum bagging that hasn't already been achieved through proper and good quality laminating.

In theory it may well help for very high temperature applications but this is rare and i have not heard of anyone vacuum bagging the moulds even in this situation.

I would expand on what Warren said - The important part is getting the gel coat into all the corners and crevices. As this is like a very thick paint when warm, you can't vacuum bag it as it will simply squish all over the place!. You then add the paste whilst the gel coat is still tacky (but firm enough that pushing on the paste doesn't disturb it- correct me if I am wrong Warren or Paul, but I use the fingerprint test, if my finger leaves a print but the gel doesn't come off on my finger it is ready for the next stage) and then add the fibreglass over the whole lot.

For smallish parts I use an old domestic oven bought from eBay. There are plenty on there, here is an example. Simply drill a hole through the side for the vacuum tube :-)

https://www.ebay.co.uk/itm/neff-Electric-oven-You-Arrange-Courier-Or-Collect/323346305953?hash=item4b48f113a1%3Ag%3AKUAAAOSwpz5bR6-N&_sacat=0&_nkw=domestic+oven+electric&_from=R40&LH_ItemCondition=4&rt=nc&_trksid=m570.l1313

Hi Steve, Don't get me wrong, but I know the basics as I have been doing Fiberglas for over 30 years, so I have lots of Moulds and am forever repairing then, mainly because they were not made well to start with, none have been Vacuum Bagged, so now I want to start learning the correct way and Materials to do CF, so want to start with Hand Layup and Air dry, and if I get on with then I will buy a large oven to accommodate large panels such as Bonnets, doors, Undertrays, the Ferrari Undertrays are very large approx 6ft X 4.5 ft, so I do not want to run before I can walk, Like I said to Warren the Mould is the most important tool as it is going to be used lots of times, and especially if you have a perfect item to Mould the last thing you want to be doing is repairs to a new Mould, so when I found this Forum I was hoping for some great advice, but when someone says no need to VB your Mould I find it very hard to believe that that is best practice, so anyway I will persevere and try VBing my Moulds, so thanks for all you advice and help, I will let you know how I get on, Regards DM

I don't get you wrong :-) This is a great place to throw around ideas. 

Once the gel coat has cured sufficiently so that you can add the paste, no amount of vacuum bagging will improve matters. However, there is no harm in vacuum bagging the fibreglass but you are wasting a lot of time and materials for no advantage, IMO.

The guys stating there is no need to vacuum the mould work at EC so they do know what they are talking about. Matt is the guy in the videos :-)

I made my own large oven (6' x 6' x 3') to accommodate my flip front. Easy to make and it is powered by 150w light bulbs :-) These are spread around the perimeter helping to even out the temp (this is also a large fan).

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Hanaldo - 7/19/2018 11:30:14 PM

You are over thinking this. You do not need vacuum for making your mould, vacuum is only going to cause you trouble. If you had a solid pattern then I'd say go for it (albeit still totally unnecessary), but you don't. You will be using temporary flanges, which will not be able to handle the vacuum. If you use fluted signboard, this will crush under vacuum. If you use solid polypropylene sheet or even metal flanges - they are still temporary and will be distorted and pulled away from the position you want them in.

In all scenarios, you have a piece that isn't suited for vacuum at all. It is perfectly possible to make a mould like this without vacuum without any voids what-so-ever. Use the right processes and materials, dont try to shoehorn in a process that doesn't suit what you are working with.