1/4 Scale ASK21

Let us all watch your new project progress.
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Peter Balcombe
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Re: 1/4 Scale ASK21

Post by Peter Balcombe » 14 Aug 2018, 20:08

Epoxy glass fuselage laid up last Saturday in a marathon 6hr stint.
After discussion with John Hall it had been decided to lay up each half with matching join line overlaps using slow cure epoxy resin. The 2 halves were put together whilst the resin was still wet & the overlaps smoothed down onto the other side to form the complete part in one sitting.
After the normal cure period, the part was post-cured for 8hrs or so at 30+. I finally managed to release it from the mould this afternoon after a bit of a struggle (as anticipated due to the less than perfect nature of the mould surfaces)
However, it is now out and should be useable after tidying up some surface blemishes.

I still have ply wing root & tail fin top to epoxy into place as these were left out at the lay up stage to reduce work.
An idea of the result is shown below.
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Cliff Evans
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Re: 1/4 Scale ASK21

Post by Cliff Evans » 14 Aug 2018, 23:59

Very nice Peter. For a first attempt you have done B****y marvellously!

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VinceC
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Re: 1/4 Scale ASK21

Post by VinceC » 15 Aug 2018, 08:36

Excellent work Peter. When does production start?

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Peter Balcombe
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Re: 1/4 Scale ASK21

Post by Peter Balcombe » 15 Aug 2018, 08:54

Thanks guys.
Still a long way to go to get a flying model, but at least I now have something to attach things to!

The mould needs some repairs & surface polishing before I can even think about re-use, and probably isn’t good enough for serious ‘production’ use - at least with my fibreglassing skill level. We will see where we go once the design is proven.

Once I have added the internal ply wing roots/tailplane mount and checked that my planned wheels will fit, I can progress the built-up wing and tailplane designs ready for part cutting.

roo Hawkins
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Re: 1/4 Scale ASK21

Post by roo Hawkins » 15 Aug 2018, 21:24

Well done Peter. A lot of hard work I think I will keep with my lost foam method. But it is some great work you have done look forward to seeing how the rest of the model comes together. .Roo :D

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Mike Forsyth
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Re: 1/4 Scale ASK21

Post by Mike Forsyth » 25 Aug 2018, 21:13

Hi Peter, I have been watching this build and was wondering what weight of cloth you used in your epoxy glass fuselage, and how many layers? and did you use a gel coat or was this just layed up just using epoxy as the first layer?

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Peter Balcombe
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Re: 1/4 Scale ASK21

Post by Peter Balcombe » 25 Aug 2018, 21:50

Hi Mike,
I used an epoxy compatible polyester gel coat (Easy Composites GC50), then a 100gsm layer from nose to wing root, plus 2 layers of 300gsm (one twill? & one plain weave) using 5 main pattern shapes per side.
In addition, I used 300gsm blisters in the wing root, main wheel & tailwheel fairings, plus strips/rovings around all of the canopy flanges.
The layup was as recommended by John Hall who has made all the fuselages for the Pat Teakle range over the years.
1/4” ply wing roots have now been epoxied into the insides of the wing roots & glassed over.

My only issues were where the mould surface wasn’t perfect (primarily around the wing root/canopy flanges) & my layup also had a couple of voids behind the gel coat in similar areas.
However, as I didn’t have a pigment in the gel coat (GC50 is clear only) then it isn’t really a problem as I have to paint the part in any case, so this will also cover the small amount of filling needed.
Peter

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Mike Forsyth
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Re: 1/4 Scale ASK21

Post by Mike Forsyth » 27 Aug 2018, 10:15

Thanks for the information, it will come in very handy. One last question what was the weight of the fuselage? I always wanted to try making a glass fibre fuselage, but I think I will try on a smaller model first, just to test the water so too speak, I don't think I'm brave enough to do a 1/4 scale model, Even though you have a few imperfections you have done a remarkable job on your very first glass fibre fuselage I can only hope I'm that lucky.

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Peter Balcombe
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Re: 1/4 Scale ASK21

Post by Peter Balcombe » 27 Aug 2018, 11:05

Mike,
Bare fuselage weight with ply root blanks fitted is 1.7Kg for a fairly bulbous 2m long fuselage. (Wing is 70mm thick at root).
Not sure if this is heavy or not, although I gather that epoxy resin fuselages are usually lighter than polyester resin ones, but this obviously depends on the quantity of cloth & resin used in each case.

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Simon WS
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Re: 1/4 Scale ASK21

Post by Simon WS » 27 Aug 2018, 11:43

Fantastic achievement Peter.

Simon

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