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Semi-scale ASH25
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- Posts: 577
- Joined: 30 May 2015, 20:35
- Location: Sutton Bank, North Yorkshire
Re: Semi-scale ASH25
The World's Slowest Builder? Could be.
Anyway I've started on the replacement forward fuselage (the tail section is detachable behind the wing TE and survived the crash ).
First I sketched a side view and plan view of the fus and lofted some cross-sections.
There are many ways to transfer these 2D drawings into foam.
You could just get a big lump of foam, transfer the top and side profiles onto it, bandsaw around these, then get creative with a sanding block to create the contours. But I didn't think I'd be able to get enough cross-sectional symmetry to be happy enough with the end product.
At the other end of the spectrum you could cut many (say, 20mm thick) formers and sandwich these together. This would massively reduce the amount of sanding and ensure good profile accuracy. It would also take blummin' ages.
In the end I decided to cut a 50mm thick central keel to capture the side profile, then fill out with 50mm thick half-formers either side. Yeah this means there are some big steps between adjacent formers, but I reckon there are enough reference points to help me keep the profile accurate when sanding.
So.. over to the scroll saw, and about 2 hours later I have a little kit of foam parts. Must say, this pink foam is fab to work with - so easy to cut/sand but stiff enough to stay straight and rigid.
A couple of hours later the whole lot is glued with PVA, taking obsessive care to check alignment/symmetry.
The next step is to get jiggy with a sanding block and blend all those formers to a smooth flowing shape.... BUT maybe not for 6 weeks as I'm back to work Monday.
Anyway I've started on the replacement forward fuselage (the tail section is detachable behind the wing TE and survived the crash ).
First I sketched a side view and plan view of the fus and lofted some cross-sections.
There are many ways to transfer these 2D drawings into foam.
You could just get a big lump of foam, transfer the top and side profiles onto it, bandsaw around these, then get creative with a sanding block to create the contours. But I didn't think I'd be able to get enough cross-sectional symmetry to be happy enough with the end product.
At the other end of the spectrum you could cut many (say, 20mm thick) formers and sandwich these together. This would massively reduce the amount of sanding and ensure good profile accuracy. It would also take blummin' ages.
In the end I decided to cut a 50mm thick central keel to capture the side profile, then fill out with 50mm thick half-formers either side. Yeah this means there are some big steps between adjacent formers, but I reckon there are enough reference points to help me keep the profile accurate when sanding.
So.. over to the scroll saw, and about 2 hours later I have a little kit of foam parts. Must say, this pink foam is fab to work with - so easy to cut/sand but stiff enough to stay straight and rigid.
A couple of hours later the whole lot is glued with PVA, taking obsessive care to check alignment/symmetry.
The next step is to get jiggy with a sanding block and blend all those formers to a smooth flowing shape.... BUT maybe not for 6 weeks as I'm back to work Monday.
Re: Semi-scale ASH25
Rog, I'm glad to see that someone else resorts to a big roll of paper and a good old lead pencil.
Brian.
Brian.
Re: Semi-scale ASH25
I can't drive CAD either Brian, so roll of wallpaper backing plain paper, rulers, squares and a pencil for me too.
John M
John M
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- Posts: 577
- Joined: 30 May 2015, 20:35
- Location: Sutton Bank, North Yorkshire
Re: Semi-scale ASH25
CAD is great for some things but for simple-one-offs like a model glider I actually prefer the creative freedom of a pencil running over paper. It gets my hands more in touch with the 2D shapes before they become 3D forms. It's a tactile thing and also a nostalgic thing - takes me back to a happy childhood of endlessly doodling planes.
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- Posts: 557
- Joined: 18 Mar 2015, 20:12
- Location: Northamptonshire
Re: Semi-scale ASH25
Great to see that you have made a start and it's looking good. I myself always shape from a side and top profile the same way we made surfboards. There is a method we shape what we call the rails what you call the side profile of a glider. But there is meny ways to skin and cat. I myself use pen and paper still works.
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- Posts: 577
- Joined: 30 May 2015, 20:35
- Location: Sutton Bank, North Yorkshire
Re: Semi-scale ASH25
Crikey I've had fun!
Shaping the pink foam of the new front fuselage section went really well, working methodically with a serious of chamfers on each side to keep it symmetrical. It was so pleasurable to see the stepped sections blend into a smooth 3D form.
I then worked on either end. I'm fitting a FES so screwed the motor bulkhead to the front. After laminating up a block of balsa I turned a spinner using my electric drill as a kind of lathe. Not sure what I'll do next - either glass the balsa, fill, paint and use it as the spinner or use it as a plug and vac-form a plastic spinner off it.
Shaping the pink foam of the new front fuselage section went really well, working methodically with a serious of chamfers on each side to keep it symmetrical. It was so pleasurable to see the stepped sections blend into a smooth 3D form.
I then worked on either end. I'm fitting a FES so screwed the motor bulkhead to the front. After laminating up a block of balsa I turned a spinner using my electric drill as a kind of lathe. Not sure what I'll do next - either glass the balsa, fill, paint and use it as the spinner or use it as a plug and vac-form a plastic spinner off it.
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- Posts: 577
- Joined: 30 May 2015, 20:35
- Location: Sutton Bank, North Yorkshire
Re: Semi-scale ASH25
At the back of the new front fuselage section I'll fix in a former so that it can bolt to the original rear fuselage section (which survived the crash). This former is cut from 9mm ply and profiled around the rear fuselage section, before fixing to the end of the front section foam plug. The profiling took a while due to the angle of the join, but after an hour of trimming I think it should give a smooth blend. Anyway, why rush? I just love being in my workshop.
Next time I'll tackle the wing roots.
Next time I'll tackle the wing roots.
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- Posts: 335
- Joined: 18 Mar 2015, 08:18
- Location: West Wales
- Contact:
Re: Semi-scale ASH25
Looking great Rog!
Out of interest, what did you use to shape your foam? I find permablocks a little too coarse.
Ell.
Out of interest, what did you use to shape your foam? I find permablocks a little too coarse.
Ell.
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- Posts: 577
- Joined: 30 May 2015, 20:35
- Location: Sutton Bank, North Yorkshire
Re: Semi-scale ASH25
Cheers folks.Elliot Howells wrote: ↑18 Mar 2020, 08:17 Looking great Rog!
Out of interest, what did you use to shape your foam? I find permablocks a little too coarse.
Ell.
I used a long Permagrit to get the bulk off then stroked it with a 6"x6" pad of 240 grit, curved in my hand. I wait until the hour before sunset because the low, warm light casts really useful shadows revealing highspots. The strip-lighting in my workshop is no good for this.
Just heard schools closed so hoping to get more time in the workshop between remotely-taught lessons.