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[nhp651]

Oh yes, forgot to talk about the other important part of any mould.......the glass fibre matting.

Although woven matting is a lovely and neat way of making a mould with superb finish quality I myself have found it hard to work on smaller moulds...difficulties in getting round almost right angle edges and into sharp areas such as the bow and stern of a boat have caused me to dispense with this type of material and I tend to go for chopped strand matting, and use a 1 1/2 oz weight for my moulding purposes.

Even this I find a little thick for moulding round edges already mentioned, and what I do is (rather than buy the 1oz weight for the same cost)is to cut my matting into smaller manageable pieces that fit into the mould in places with odd shapes, and then split the matting to actually get two layers out of one. It gives me better impregnation of resin into the matting and less chance of air bubbles and "dry spots" in the mould.
This can make for a heavier mould as a little more resin is used, but personally I don't feel that to be a bad move at all.

and splitting the matting is an easy task!

[furball]

How do you clean out your stippling brushes Neil? Or do you not bother and just get the DIY cheapies each time?


Cheers

Lance

[nhp651]

they are cheapies, Lance, but being a tight squeekie sob, I wash them out in acetone after I have finished a section of a mould............( probably costs me more in acetone if I really sat down and thought about it...but not too cheap as the bristles come out .usually as I'm laying a gelcoat, lol...and that really is a bummer seeing a black hair in a lovely white gelcoat,  )they'll keep soft till you finish working, and then a thorough wash in the stuff, and let the brush dry thoroughly for a couple of days, AND use another brush for the next section or the acetone in the brush might react with the resin/gelcoat.......I keep two of each type on the go and use them alternately.
neil.

[nhp651]

MOULD BUILDING

The most important and most critical part of any mould making is to be able to remove the moulding from the mould as easy as possible. No matter how well prepared the moulds are with release wax and agent and no matter how smooth the mould is, the nature of the material that you are working with, poyester resin has a propensity and urge to stick to the "item" that it is laid up against, and if you are laying polyester resin against polyester resin then it will try to stick to it with gusto. And so you have to try to eliviate that problem as much as possible.

Professional mouldwers of high volume and large mouldings have the added luxuty of being able to separate mouldings from moulds by building into their moulds, pressure outlets that they can connect either warm water jets or compressed air in order to separate mould from mouldings.sadly the modeller doesn't have these luxuries and also tends to put onto his plug as much detailing as possible, which also hinders mould separation. As such the modeller has to use guile and some brute force, and unless a little physics is employed, he/she can ruin a mould first time he pulls a moulding out of the mould.

To this, we tend to use "split moulds", i.e. the mould is made in more than one part and then held together using bolts before laying up the moulding.

When I designed my first lifeboat  for moulding I had built into the plug the keel skegs ( later left off wioth subsequent models and added later in the build) and this posed a problem in that if I made the mould as just a two part split like most other model moulds, I wouldn't be able to extract the moulding because the tunnels, the bilge skegs AND  the protective belting would all act against each other and prohibit removal without either breaking the mould or breaking the bilge skegs off whilst removing the moulding from the mould.

carefull thought decided that the moulds would have to be, ( instead of a singler split down the centre) a three part split, giving a four part mould, and the second and third split would have to be along the centre line of the belting for to aft.
The diagram below shows the splits in the mould flanges and the black arrows show the direction of pull of the parts of the mould.

All my subsequent lifeboat hulls have since been built this way, and they "pop" out perfectly.

[nhp651]

Now, those "flanges" that form the splits to the moulds have to be moulded in to the moulds at the time of moulding and therefore something removeable has to be placed onto the plug in order to mould upto to form the flange.
The process is to make ( with such a four part mould) one quarter of the mould, usually the largest part ( and in this place the bottom half) and once it is set  then take the removeable flange away and then mould up to the (by now) set and cured grp flange.

The temporary flange is held onto the plug by foul means and fair. on such a long one as the Mary Stanford, I usually set up wooden battens at deck level to screw the ply or hardboard flange too and hold steady with a central support as in the photo. I back fill any gaps between the flange and the plug with moulders plastecine, and secure the flange to the plug with blue tack. see all photos for this set up.

the photos also show the flanges for the cabins, but because of their simplicity these are made just in a single split mould giving two halves.

[nhp651]

This is the finish between flange and plug that you are aiming for, to give a smooth edge to the mould to plug fitting.

[nhp651]

Now comes the actual messy work of Laying up a mould.

1) the plug, which has been pre waxed as mentioned before, has now to take a layer of PVA release agent......similar to a pva glue but much thinner, I tend to put some into a margarine dish and apply with a soft sponge giving an even layer. You will find that it bubbles and runs because of the wax, but with continued light rubbing with the sponge as the agent dries you will find that it will "wipe out" eventually and go on in an even coat. This is water soluable and the residue can be removed from the mould later with warm water. Allow this to dry thoroughly or it will react with the first coat of the moulding process giving a rippled orange peel effect.

2) A gelcoat has to be laid as the first layer and I personally like to colour it with a white pigment.really should colour it with a different colour to the actual white mouldings, but just my preference. This is the hard and protective outer/inner coating to the moulding/mould respectively, and must be covered by the layers of polyester resin/chopped strand mattings (as usually recomended by the manufacturers of the resins used) within 24 hours AT THE LATEST or de lamination might take place, as the resins bond to the gelcoat and make a good attachment.

3) I usually lay up my first layers of chopped strand matting to the gell coat within a couple of hours of the gel coat layer "gowing off"

I have my chopped strand matting cut to small usable pieces, split in to two layers, and mix about a pound - 2 pounds of resin at a time, and even in a warm workshop of about 18 - 20c I have time to use all that resin without it going off, giving a good working time.
Subsequent layers of matting/resin can be coloured with resin colouring pigment should the desire be there to do it...sometimes I do, sometimes I don't.




Stippling hard and none stop , working the matting into corners you aim for a good airtight and bubble free finish.

Picture below shows woring on the first half of the cabin up to the flange.

[nhp651]

These shots show the shape of the  longitudinal flange running along the length of the keel and the flange running around the centre line of the protective belting, with the gelcoat added for the first quarter mould.

Once the gelcoat had "gone off" and the matting and resin has been added, which I normally build up to around 4 -5 layers all over for a production mould(not for a moulding though which would be considerably lighter and thinner) it is left to cure for around 48 hours, and then the flange running around the belting ONLY is removed and the second quarter of the mould...the small part above the belting to the deck level, on the same side is moulded in exactly the same way as before.
This is why the deck has been extended upwards to give a little higher edge to the mould, and hopefully because it has been extended in the laying up process, will be well knitted together without any air bubbles on the edging, when trimmed back to the correct hight for trimming off the mouldings inside. You will now also see that to put a flat flange over all the deck to mould up to would be impractical with such a mould as this.
 
In these shots you can see the battening that holds the main flange to the plug running down the keel. it is screwed on so that it can be easily removed when the laying up process is done to one side of the boat plug.

However before this, the now new and exposed grp flange from the first quarter moulding is treated to the same preparation as the plug...5 - 6 layers of wax, rubbed down and then PVA release agent applied. This release agent can be seen in the next shot of the cabin both to be moulded and after the first half of the mould has been laid up.

[Norseman]

Hi Neil

I am certainly taking notes - thanks for doing this thread.

Dave

[andyn]

Of course the most important part of kit manufacturing is the white labcoat, it makes you feel far more intellectual when wearing it, especially when combined with goggles. Plus, being long it's a fantastic place to wipe dirty hands....

Andy (will show you what I'm on about tomorow )

[nhp651]

you obviously weren't taking notice of the lesson, then andy....

100 lines "I must look at the pictures more closely"......

i was wearing my special latex gloves......no dirty hands on me that day!!

[andyn]

Oh yes, I do too, however I still manage to get my hands and infact everything covered in pigment.....

[nhp651]

in the immortal words of Captain Mainwaring......."you stupid boy"
I'm like that with RTV moulding rubber, lol
neil.

[andyn]

Like I said, makes you feel far more intellectual....

[john44]

What no hair-net when using a pedestal drill tut, tut.
as for the fine adjustment tool well 

[andyn]

That would be doing something according to health and safety rules, which I don't do

Plus, common sense would dictate that I'm not going to stick my hair into a milling machine.....

The 'fine adjustment tool' is for getting the little man to talk, I suspect he's a spy.....

Andy

[Bill D203]

What no hair-net when using a pedestal drill tut, tut.
as for the fine adjustment tool well 

Blimey he don't need a hair net that is as short as i have ever seen his hair. There must have been some spare Gas & Air in Newport if Andy has had it cut.

[nhp651]

he looks almost human   

[Bill D203]

he looks almost human   

Hi Neil
I think it's LOVE
Ah

[nhp651]

 

 

[MikeA]

dodgy having long hair. i know, ive got my rapped round my propshafts 3 times now tryin to listen to wear vibrations are coming from. you would think youd learn 

[andyn]

  I would thought you would have too

[RaaArtyGunner]

WARNING WARNING


Remember David beat Goliath
 

[Welsh Wizard]

Think We need to drag Andy to a hairdressers hold him down and give him a No3


GET A HAIRCUT LAD


Dave

[MikeA]

dont andy you must rebel!!

[andyn]

Had one 3 weeks ago

[RaaArtyGunner]

Had one 3 weeks ago

That is toooooooo frequent and can lead to Baldness.

Here in OZ we keep good heads of hair so the harsh sun does not fry our brains  

[andyn]

The one I had before that was about 6 months ago so I think I'll be ok

Sorry for hijacking your thread Neil mate

[RaaArtyGunner]

 Yes please Neil, back to Lifeboats far more interesting and informative.

[nhp651]

narh.this is far more enjoyable..... 

[Marks Model Bits]

narh.this is far more enjoyable..... 

I would rather take the mick out of Andy as well.......... Much more fun.

[RaaArtyGunner]

narh.this is far more enjoyable..... 

Ah well, as Martin has named the forum "Mayhem",  who are we to contradict him.

[nhp651]

Oh al right then, if only for Andy's sanity and well being, here goes for another bit of brain bashing.

the first quarter has now cured and the flange around the protective belting has been removed (but not the flange running the length of the keel).

Now the grp matting and resin is laid up to the upper part of the belting and alloud to cure.With this small area I tend to use shortish strips of matting around 6 - 12 inches in length and around 3" width to build up the layers, one length of the boat at a time so that a good even level of layers is achieved.

this is then allowed to cure again for 24 - 48 hours.


Once the second quarter has cured, the whole process begind again with the other side of the boat, by firstly removing the flange from the full length of the keel. The exposed grp flange must again be fully polished up and release agent added before any gell coat and resin/matting is applied, and the flange for the belting is again added to make the third split in the mould.

It is a long and methodical process to produce the mould, but if time is taken to lay the matting up slowly, carefully and with passion, you can avoid air bubbles in the mould and should end up with a "tool" that will give you a good number of mouldings from the same mould before it has to be replaced.

below is a number of shots of the finished mould in four parts and trimmed up.



However at this point the mould will still be "green" and needs to be stored correctly with the plug still in place for 48 -72 hours to allow it to cure well, or any subsequent moulding taken from the mould may come out twisted, warped or even hollow bilged...............i.e, you lay the boat on it's keel and a hollow can be seen where the keel doesn't run flat.........although this can also be caused by taking the moulding from the mould in a "green" and uncured state......so!!!, take your time and have patience.

[nhp651]

One of the worst things about GRP are the very nasty splinters that you can pick up in your hands if the mould isn't cleaned up properly...they hurt, they get infectec quickly and they are a real nuisance, so before anything else is done, the whole mould must be trimmed up......I tend to use a power file to trim down toa smooth edge once I have trimmed the edges of the flanges with a jig saw using a diamond tipped blade.

The Flanges then need to be marked for drilling, and drilled with a 6mm hole to take 6mm roofing bolts 30mm in length. Spaced at intervals of around 4" apart, and about half way between the edge of the mould flange and the inner plug the holes are drilled and cleaned up.

Finally the mould is ready for splitting. I start with the Protective belting flanges first, and, using either wooden or nylon V shaped wedges ( NEVER EVER USE CHISELS, SCREWDRIVERS OR ANY STEEL WEDGES)you can generally, with a few taps from a wooden mallet, find a starting point to drive in your first wedge.Just use a little brute force and some physics to drive in wedges along the length of the flange, and as you get towards the middle of the flange, you should hear a lovely satisfying "crack" as the release agent does it's job and the mould parts company from the plug, and you let out a sigh of relief that all the preparation that you have done to the plug has worked it's charm. It really is a great feeling, as the unknown becomes the reality and you find that you have a great mould. Just repeating the process with the second belting flange, progress is now made to split the main parts of the hull. All goes well, and an inspection of the new mould shows that a good moulding can now be taken from the mould.....approximate time to lay up a four piece mould including preparation of the flanges and lay up time .........about 40 hours.

[irishcarguy]

Andy, which hair did you cut & could we have a picture please. Mick B.