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1/4 Scale ASK21

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roo Hawkins
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Re: 1/4 Scale ASK21

Post by roo Hawkins »

Nice mate

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Peter Balcombe
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Location: Clevedon, North Somerset, U.K.

Re: 1/4 Scale ASK21

Post by Peter Balcombe »

With both wings now fully sheeted & fuselage joiner installation complete, attention moves to completing the wings.
After profiling the lower edge of the stock TE section to match the distinct undercamber in this TE area, the aileron has now been separated on the 1st wing.
(This involved remembering to mark the hinge line on the top surface - defined by rear edge of vertical hinge spar) prior to adding the lower skin). The aileron could then be cut off by inserting a scalpel blade through the top skin, down the rear of the hinge spar & out through the bottom skin at the ends & centre of the aileron. Join up the lower surface points & cut through skin & ribs using a razor saw. There is room for error at the bottom due to the gap formed by the angled aileron LE web.
Once removed the aileron LE bevel can be tidied up.
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Peter Balcombe
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Location: Clevedon, North Somerset, U.K.

Re: 1/4 Scale ASK21

Post by Peter Balcombe »

With the wings now having had their glass cloth applied & awaiting a final coat of epoxy to seal the cloth weave, attention has passed to preparing plugs from which I can hopefully ask Barry at Sarik to pull the 2 canopies.

When making the fuselage plug a while ago, I made sure that I saved the canopy cutouts, which were glassed to avoid hanger rash etc. The plan was to use these as the basis for the canopy pulling plugs - although at the time, I wasn’t sure how I would go about this!

In order to produce the canopy plugs, I need to extend the canopy shapes by 1.5” or more at front, rear and bottom, and also make the plug capable of withstanding the vacuum pull without distortion.
The final plug will be cast in Herculite plaster in a simple negative mould bath formed around the extended canopy cutouts.
So ... the first job was to cut some foam blocks having the extended canopy dimensions & cut a recess in these into which the canopy cutouts could be fixed. The remaining foam will then be shaped to profile to also include a moulding release draught angle. The pics below show the canopy cutouts in place in the foam blocks.
Hopefully, all this will work out ;)
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B Sharp
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Location: Perthshire

Re: 1/4 Scale ASK21

Post by B Sharp »

I have been patiently for this build to continue Peter. That is an interesting method for making the plugs .
Brian. :)

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Peter Balcombe
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Re: 1/4 Scale ASK21

Post by Peter Balcombe »

Hi Brian,
It’s probably not necessarily the normal way to do it, but it’s my first time & I already have the canopy opening blanks saved from the fuselage mould making process ;)

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Peter Balcombe
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Re: 1/4 Scale ASK21

Post by Peter Balcombe »

I know that canopy plugs are normally made from a hardwood core, but I am going to have a go at something different - given my starting point with two perfectly profiled canopy opening blanks.

I plan to end up with solid herculite (or similar) plaster moulding plugs, but will be trying a different route to get there. It may not work, but if it does, then it should make life a lot easier than carving two large wooden plugs from scratch.
The extended canopy opening blanks have now been initially filled & shaped to conform to the canopy opening profiles. The pic below shows one of them before the front & rear release angles were increased. The resultant block will also be given more generous rounded corners to improve release tapers prior to sealing with glass & epoxy resin.
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Peter Balcombe
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Re: 1/4 Scale ASK21

Post by Peter Balcombe »

Back to the wings, which have now been glassed and also received a thin sealing coat of epoxy resin to leave a gloss finish.
Once rubbed back a bit with fine wet&dry used wet, the ailerons will be hinged & servo installation sorted prior to painting - which might now have to wait a bit!
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Jolly Roger
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Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: 1/4 Scale ASK21

Post by Jolly Roger »

Wings look lovely Peter. The camber on the undersurface looks very realistic.

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Peter Balcombe
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Re: 1/4 Scale ASK21

Post by Peter Balcombe »

Jolly Roger wrote:
15 Oct 2020, 22:53
Wings look lovely Peter. The camber on the undersurface looks very realistic.
After talking to Noël Rumers before the wings were designed several years ago, I decided to use the full size FX section as Noël reckoned that with a tip chord of >130mm, that would work & allow the model to fly at a scale speed.
We will see if that is so in due course ;)

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B Sharp
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Re: 1/4 Scale ASK21

Post by B Sharp »

All looking very good Peter, but where do the golf clubs fit into this equation?
Brian. :D

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