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1/4 Scale ASK21

Let us all watch your new project progress.
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Peter Balcombe
Posts: 1255
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/4 Scale ASK21

Post by Peter Balcombe »

First side of mould now laid up.
A bit of a learning curve, but hopefully it will come out ok in due course.
Need to get more resin for 2nd side as it used a lot more than I expected ;)
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Simon WS
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Joined: 18 Mar 2015, 11:39
Location: Kent, UK

Re: 1/4 Scale ASK21

Post by Simon WS »

Looking good Peter. Was making a mould something you fancied trying or are planning on making more than one for your mates?!

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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/4 Scale ASK21

Post by Peter Balcombe »

Thanks Simon,
Although initially thinking of going down Roo’s one-off route, I somehow decided that I would have a go at making a mould as a project!
This was partly because at the time, I wanted to try the process to make another fuselage off of an unused DG100 fuselage I have & partly because I thought it might be useful to be able to make a spare if needed.
I haven’t seen 1/4 scale ASK21 models about, so thought it a good subject.

There is a looong way to go yet though ;)

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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/4 Scale ASK21

Post by Peter Balcombe »

Mark,
What is a ‘heavy’ moulding?
As far as I know, I am making the mould as a kit manufacturer would - layers as recommended by John Hall.
There is a gel coat plus the equivalent of 1 layer of 300gsm + 2 layers of 450gsm on the fuselage part of the mould, with twice that on the flanges.

Mark Erwood
Posts: 26
Joined: 22 Mar 2018, 19:02
Location: Saltash, Cornwall

Re: 1/4 Scale ASK21

Post by Mark Erwood »

Normal industry practice is to make moulds at least twice the lay-up weight of the mouldings that you expect to produce. Seems to give a good life to moulds.

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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/4 Scale ASK21

Post by Peter Balcombe »

Mould layup is probably triple the expected fuselage content, so seems to fit the bill in that respect.
However, lessons learnt for next time:
1. Take more care to ensure parting board gap fill is perfectly level with parting board at all points.
2. Fit fence to rear of fin (for open rear of fin).
3. Limit mould to within about 3” of plug to reduce layup materials needed and weight.
4. Add lots of registration features along intended mould half bolt line.

1st side now carefully removed from parting board (together with plug) and turned over once the overall mould outline had been slimmed down to within 3” of the plug. Mould half bolting hole line marked approx 30mm from plug outline & new registration countersinks added every 12”or so, as the original features were nearly all removed when the mould flange was slimmed down. Bolts will be fitted every 6” or so.
Vertical fence fitted at rear of fin for 2nd side (1st side mould rear will be cut off later).
Nearly ready for making a start on the 2nd side of the mould when I have restocked with resin ;)
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D036E060-0864-4B14-A7C1-872544E13772.jpeg

Mark Erwood
Posts: 26
Joined: 22 Mar 2018, 19:02
Location: Saltash, Cornwall

Re: 1/4 Scale ASK21

Post by Mark Erwood »

Hi Peter,

Sounds as though your mould will be more than adequate. The last mould that I made I trimmed the flanges to about 1". For registration I drilled a 1/8" hole every few inches in the first flange and superglued a 1/8" snap head rivet in each hole. it worked a treat. Good luck with the rest of the build.

Mark

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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/4 Scale ASK21

Post by Peter Balcombe »

Completed the mould layup yesterday & have just split the mould.
After a bit of a struggle getting the 2nd side off, the plug came out reasonably intact.
A bit of remedial work is needed where the plug stuck/ or where there are small voids, but I hopefully now have the basis of a useable mould.
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/4 Scale ASK21

Post by Peter Balcombe »

Mark,
Good tip with ‘just in case’ scenario.
I have a number of registration points included in the mould halves (added when original ones were going to be cut off!).
Will clean various stuck plug areas off tomorrow & then attack the other damaged areas.

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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/4 Scale ASK21

Post by Peter Balcombe »

Mark,
I now understand what you mean by a ‘heavy’ mould :)

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