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Member postings for neil howard-pritchard

Here is a list of all the postings neil howard-pritchard has made in our forums. Click on a thread name to jump to the thread.

Thread: TYNE Class Lifeboat build
04/08/2020 10:31:36

you can use for cutting these channels, either a "lino" cutter or a sharp point tipped scalpel.

I use the former for hard rubber moulds, and the latter for soft and medium cast rubber moulds.

04/08/2020 10:26:28

the next phase of the process will have to wait for up to 48 hours.....

sadly I miscalculated the amount of catalyst that I put into the last mix last night and it is very slow to actually "go off" never mind cure, and they are three of the four split moulds that I need to go forward.....

but just for you Bob, and anyone else that wants to know what happens next......I have photographed an old split mould made in exactly the same way as these, but in a used state, that I made years ago and have used for all my old lifeboats

to finish the mould ready for moulding replicas of the originals[in this case stanchions] …. you simply cut a channel to the top of the mould from the model, and then widen the neck into a V shape, both sides of the mould.

not forgetting to cut at the bottom of the model a small release track for air to escape as the moulding material is let into the mould.

hope this solves the process to completion.

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03/08/2020 15:57:19

you are impatient Bob, and jumping the gun...……..there is a process to follow with anything.

just sit back, relax and wait till the process is finished, then you will understand the whole process.

03/08/2020 15:01:35

all open cast moulds have now been laid in their boxes, one split mould the trial one from last night has been laid with the second half.

I used Vaseline as the release agent, applied with a semi stiff artist brush.

and the other split moulds have had the first layer poured into the moulds.

Hopefully, the second layer of the split moulds will be ready for pouring this evening.

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03/08/2020 12:44:00

finally a couple of pictures of the mould ready for the second half, and a picture of my little lifeboat crew, cast in exactly the same way, with the exact same materials.

top left is mould ready for second half of rubber.

img_5953.jpg these are my lifeboat crew, made from 1;12 scale reformed dolls house figures to modern lifeboat attire.

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Edited By neil howard-pritchard on 03/08/2020 12:44:55

03/08/2020 12:28:33

MATERIALS AND WHERE TO BUY THEM AND COSTS.

These are my own preferences and why.

PLASTICINE.....soft enough to mould, press the model into and highly reusable on many moulds. AND relatively cheap compared to none sulphur modelmakers clay, which is also hard and needs heat to soften it.

https://www.ebay.co.uk/itm/Newplast-Plasticine-Alternative-Modelling-Clay-500g-Packs-Brown/273201014931?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

SILICON RUBBER.....the cheapest on the market that I have found, been using it for about 10 years and never had a problem with it ripping and tearing, and gives good cured strength. British company and service is super fast.the rubber also has a long shelf life once opened. I have used it even a year after opening with no degradation of materials or moulds.

https://www.ebay.co.uk/itm/RTV-Silicone-Rubber-Moulding-Kit-Fast-curing/303343218572?ssPageName=STRK%3AMEBIDX%3AIT&var=602447742329&_trksid=p2057872.m2749.l2649

Resin.....this is a fast setting none shatter polyurethane resin, that you can carve bits out of even once cured. strong, tuff and paintable. It has one down side......from POURING BOTH PARTS TOGETHER to going globular and none pourable, you have literally about 2.5 minutes of working time to get into your rubber moulds.. this is unlike polyester grp resin which takes 20 minutes or so, but is brittle and easy to break once cured. I don't use polyester resin for moulding,because of that, nor do I use epoxy moulding resin because of its high unit cost.

the best place I have found is this manufacturer/supplier, with very quick service and comparable prices to other suppliers...…..but once I have found a product I like, tend to stick with that product and supplier.

this link leads you straight to the resin I use, but there are others on their site.

https://www.cfsnet.co.uk/acatalog/Standard_Fastcast.html

hope this helps you Bob, and anyone else wanting to get into hobby moulding.

03/08/2020 12:08:34
Posted by Bob Abell on 03/08/2020 09:19:18:

Very interesting, Neil

To save me having to keep reading your post, just tell me..........

Is Plasticine used for the mould?

What is the moulding material?

How long does it take to set?

Where from?

How much?

Thanks a lot, my mate

Bob

I couldn't answer yesterday as I had been told that the plasticine would react to the rubber and leave a sticky film on the rubber....….

never had it before, but thought I would use one simple mould to try out and if it did then the items to be moulded would be easily cleaned up and I could use the old none sulphur plasticine I have. HOWEVER there was absolutely no reaction to the rubber used for the mould impressions.

so all systems go.

I'll answer your questions in order.

1] plasticine is used as the base for the models to be pressed into [for a split mould] and onto for a surface poured mould.

The mould I tried the problem on is a split mould….once the rubber has been poured onto the models which have been pressed half way into the plasticine, it is left to set [around 30 - 60 minutes depending on how much catylist you add. for complicated models I use less catylist so that the rubber has to seep into every nook and cranny.

It takes about 6 hours to cure to working consistancy

Once the rubber has cured the base of the Lego box is removed and the plasticine carefully peeled off, leaving the models half embedded into the rubber.

The surface of the rubber is then rubbed gently with Vaseline to act as a barrier and release agent, or if complicated shaped the Vaseline can be applied with a 6mm wide artists brush............this prevents the second half of the rubber gluing to the first, as it will without that barrier.......forgot one in the past and it was a matter of cutting and slicing very carefully to extract the model..........and then it was a case of starting over again........never forgotten since.

The second half of the rubber mould can then be poured into the moulding box to cover the other half of the model.and left to set and cure, which I will pour this afternoon.

so that is the process of mould making. On to the materials in the next post.

02/08/2020 19:14:15

I was told today by someone that the rubber reacts to something in the plasticine, unless you use none sulphur pl...….

I used to use children's play plasticine before I used none sulphur plasticine bought from Tiranti's in Reading when I bought my casting equipment which has now gone rock hard and the only way to get it soft enough is put in the microwave. but using children's modelling clay, I never had a problem with the reaction which was described as a sticky layer on the surface of the rubber, as though the final millimetre has not hardened.

so this afternoon I did a trial run on one of the simple moulds I made.

the rubber has gone off and no longer tacky. in the heat of my insulated workshop it should be cured by 21.00 hours and will take it apart to see if there has been any reaction. if not, I'll crack on with moulding the rest of them tomorrow.

in the waiting time I put together 4 delta anchors from castings I did some time ago from the rubber moulds I made earlier.

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02/08/2020 14:29:28

hi bob, yes i'll list the materials I use, and the best I have used later...been out all morning and just sat down to watch the brit grand prix, but will have a test run after the prog.

I was warned by a chap on another forum that using silicon rubber on modellers plasticine left a soft film on the surface of the rubber, and so I don't want to waste 9 moulds of rubber if it does on this plasticine I have used.

so will do a small mould test later to see...……...if the plasticine/rubber mix works fine i'll divulge the source of it, as no point telling people something that doesn't work.

01/08/2020 21:52:48

Spent the last four hours putting the new plasticine that arrived this morning to good use.

layering the bottom of each box with a layer of approximately 10mm of plasticine to the box, I pressed lightly on the models into the pl, just to hold them. This was on the items that only needed the one side reproducing.

and rubber will be poured onto these, and that is it. mould done...…….as simple as that, and when used the resin will just be poured into the indentations in the rubber moulds.

the ones that have to be in two halves, are made slightly different.

A thicker layer of plasticine is laid into the base of the box so that the model to be replicated can be pressed home halfway down the model.

the finish of these pressings is important as no seepage of rubber must be allowed between the plasticine and the model, ir the seem line between the two rubber halves becomes raggedy, messy and needs much more sanding to produce a nice line and finish.

therefor the plasticine is pressed home against the model to stop gaps.

Finally the two halves, once moulded must fit exactly against each other to help join the two halves perfectly with no disjointing of the model [ when this happens occasionally, you can pick up a casting and it looks as thogh one half has slid down on the other half....it often happens when someone is casting a lot of one item, and doesn't reseat both halves perfectly.

to avoid this, locating tab holes are pressed into the plasticine …. [ I use the end of a pencil], and once the first layer of rubber is laid, and the plasticine is taken away, they stick proud of the rubber.

at this point, I ran out of my recently bought 1.5 kilos of plasticine, and so could do no more.

I was going to cast the rubber tonight, but believe it or not, it takes quite some mental concentration to make the boxes and place the models in to maximise the amount placed for the minimum amount of rubber used...…..its expensive stuff, and even using the cheapest, but in my opinion one of the best available, even a 5.25 kilo tub of the medium grade rubber costs nearly £80.00, and so I don't like to muck a mould up and loose all that rubber....

anyway, I am now tired and so will mould them tomorrow.

more tomorrow night.

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Thread: water jet boat
30/07/2020 23:34:24
Posted by Chris Fellows on 30/07/2020 22:29:00:

Neil

They are under the water when stationary and at low and medium speeds but at full chat when max. thrust and efficiency is required they are pretty much out of the water.

Chris

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that's an incredible shot of our flank boat Chris...…….never seen that one....just shows what I didn't know..amazing. cheers.

30/07/2020 20:33:32

I think they are just "off the shelf" units Ashley...……..they make all sizes of them apparently.

30/07/2020 16:39:55
Posted by Malcolm Frary on 29/07/2020 09:26:19:

A read of the wiki about jet boats indicates that, however counter to intuition, having the outlet above water works better

One of the most significant breakthroughs, in the development of the waterjet, was to change the design so it expelled the jetstream above the water line, contrary to many people's intuition. Hamilton discovered early on that this greatly improved performance, compared to expelling below the waterline, while also providing a "clean" hull bottom (i.e. nothing protruding below the hull line) to allow the boat to skim through very shallow water. It makes no difference to the amount of thrust generated whether the outlet is above or below the waterline, but having it above the waterline reduces hull resistance and draught.

that is a very strange comment from Hamilton of New Zealand as they are committed to supply the RNLI with enough jet propulsion units to equip at least 40 proposed Shannon class lifeboats for the next 25 years plus spares and repairs , and all of those jets have their outlets below water.

however the theory is not a new one as the first lifeboat, using water jet propulsion was built in 1886 [yes 1886] was called Duke of Northumberland, served at New Brighton for some years and had both pairs of forward and reverse jet thrusts ABOVE the waterline...……..there really is nothing new to modern technology...…...all been worked out and done before, lol.

Thread: TYNE Class Lifeboat build
30/07/2020 13:51:50

Some 2.0 mm plastic [double thickness], glue, abrasive paper and my trusty try square and irreplaceable band saw.... and……………

Some more small fittings ready to mould and cast.

These are the safety line guides that sit on the sides of the superstructure of the main cabin.

Cant remember after looking at photos whether I needed 4 or six...……..so made the six ready.

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29/07/2020 23:30:40

more bits for the pot..

the 3 windscreen wiper motors and tracks that go above the 3 front windscreens.

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29/07/2020 21:03:50
Posted by Bob Abell on 29/07/2020 14:48:04:

Well said there, Neil

I knew there was a connection between yourself and the Caldercraft and Mountfleet companies

Didn`t you design the Sunbeam Yacht and the early Lifeboat he had for sail?

Bob

that was Metcalf Mouldings, Bob...….yes I designed and manufactured the early 41' Watson and sold all rights to Dave Metcalf...made a few plugs and moulds for him over the years, and Dave has 3 other lifeboat models I have designed as kits that he has, and is working on one as a kit at the moment, which will once released, I reckon will sell like wildfire.

29/07/2020 20:56:36

should have read never sailed [ not sold]….it did sell to a collector some many years ago...…...probably 15 years ago.

.

29/07/2020 17:34:24

thanks Bob, much appreciate your comments.

she was built as a sailing version but never sold, she had a glass mahogany case to go with her, and went via Christies auctions in London to a collector…...

could be anywhere in the world now. and sadly the destination was not given to me.

29/07/2020 15:28:03

no bob, I loaned Frank my scratch model of a Cook Welton and Gemmel built trawler and all the fittings I made in plastic card called Pentland Firth, as he wanted to do a big trawler.

so, with my permission he copied all my plastic fittings which wouldn't survive the heat of his vulcanised rubber moulds, and made all the fittings for his kit called St Nectan. the hull and cabin arrangement was similar but larger than my model, but he also used my plated hull and superstructures to plate his model.

and then he used the same fittings made from his brass masters for the Boston Typhoon model that he released later.

I actually bought a St Nectan off him at huge discount given to me for the loan some time later and converted it to an ill-fated Fleetwood trawler lost with all hands in December 1959..... she was called Red Falcon reg no. LO4. pictured below.  

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Edited By neil howard-pritchard on 29/07/2020 15:30:03

29/07/2020 14:12:56

Cheers Bob...…. I owe much of my fittings tallents to.the great master of moulding fittings who taught me what I know now, many years ago over in his workshops in Holmfirth, Hudersfield.

He was a man of supreme talents and had his name on the credits of at least 2 movie films.

His name was Frank Hinchliffe, owner of Caldercraft model boats and later of Mountfleet models.

And had he not took me under his wing and explained to me on a full day of tutorials and practical work, I wouldn't now be able to make the models from scratch that I do.

I guess you and many others knew him, as he was a revelation in modern model boat kits with his white metal fittingswhere in those days revolutionary and way above what was available on the market in the 1970's

God bless you Frank, and may you rest in peace and be teaching the old man with the white beard how to put a model together.

I will for ever be grateful for your help and guidance.

Neil h-p

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