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1/4 Scale ASK21**
- Peter Balcombe
- Posts: 1399
- Joined: 18 Mar 2015, 10:13
- Location: Clevedon, North Somerset, U.K.
Re: 1/4 Scale ASK21
Many thanks for your tips James.
The LR system you mention appears to be very similar to the Easy Composites pattern coat primer/high gloss system.
I already have some of the primer, so will press ahead with that on this model.
Tom,
The wing section will be as per the full size, so FX S02-196 / FX 60-126 sections at the root /tip. The intention is to achieve the slower scale-like flying speeds.
Yes, the wing root depth is approx. 3", so plenty of room for the joiner system
The wing will be of built-up construction with a commercial top surface spoiler assembly. I haven't designed the wings/tail surfaces yet, but will do this using the DevWing CAD tool in due course, getting Cliff Evans to laser cut the parts for me.
I will probably finish the model as an ATC Air Cadets Vanguard TX.1 example.
The LR system you mention appears to be very similar to the Easy Composites pattern coat primer/high gloss system.
I already have some of the primer, so will press ahead with that on this model.
Tom,
The wing section will be as per the full size, so FX S02-196 / FX 60-126 sections at the root /tip. The intention is to achieve the slower scale-like flying speeds.
Yes, the wing root depth is approx. 3", so plenty of room for the joiner system
The wing will be of built-up construction with a commercial top surface spoiler assembly. I haven't designed the wings/tail surfaces yet, but will do this using the DevWing CAD tool in due course, getting Cliff Evans to laser cut the parts for me.
I will probably finish the model as an ATC Air Cadets Vanguard TX.1 example.
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- Posts: 557
- Joined: 18 Mar 2015, 20:12
- Location: Northamptonshire
Re: 1/4 Scale ASK21
hi peter i am glad you are getting on with it well . your work so far looks realy good .I am glad to have helped. ROO
- Peter Balcombe
- Posts: 1399
- Joined: 18 Mar 2015, 10:13
- Location: Clevedon, North Somerset, U.K.
Re: 1/4 Scale ASK21
I am still slowly getting the fuselage plug profile smooth after having added yet more filler all over the plug and then sanded back with 120 grit.
It now looks a lot better, so I am currently looking at getting a better wing root profile edge, particularly where the thin TE curves back to the fuselage.
After trying unsuccessfully to get a good edge profile with filler, I decided to bite the bullet and cut off the TE section and insert a pre-cut 1/16" epoxy board shape which I could fill to, and then sand back to the epoxy glass edge as shown in the photos below.
A further improvement will be to add an epoxy glass sheet root rib which has been matched up to the correct length FX S02-196 section.
I can then finally fair the fuselage into this rib to get what should be a very good match to the built-up wing at the wing joint.
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- Posts: 577
- Joined: 30 May 2015, 20:35
- Location: Sutton Bank, North Yorkshire
Re: 1/4 Scale ASK21
I've been following your build with interest.
Here's some photos of our local K21 this weekend, hopefully inspiring. Keep up the good work!
Rog
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- Posts: 557
- Joined: 18 Mar 2015, 20:12
- Location: Northamptonshire
Re: 1/4 Scale ASK21
hi peter good to see you have started again .I use a thin ply at the root ends . keep the posts coming
- Peter Balcombe
- Posts: 1399
- Joined: 18 Mar 2015, 10:13
- Location: Clevedon, North Somerset, U.K.
Re: 1/4 Scale ASK21
Roger, I remember my flights in a K21 at Sutton Bank so 17 or more years ago
Two fuselage root plates now added and faired in. Just needs some stopper to finish off that area.
I have another pic of the root rib, but it just will not load!!
- Peter Balcombe
- Posts: 1399
- Joined: 18 Mar 2015, 10:13
- Location: Clevedon, North Somerset, U.K.
Re: 1/4 Scale ASK21
Just checking the wing/tailplane mounting relationship in order to correctly form the plug tailplane seat at the top of the fin.
Measurements taken from the Martin Simons 3-view drawing indicate that the wing incidence should be set at +2 to +2.25 degrees with respect to the tailplane.
Does this sound right?
(Both wing and tailplane sections are as per full size)
Measurements taken from the Martin Simons 3-view drawing indicate that the wing incidence should be set at +2 to +2.25 degrees with respect to the tailplane.
Does this sound right?
(Both wing and tailplane sections are as per full size)
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- Posts: 577
- Joined: 30 May 2015, 20:35
- Location: Sutton Bank, North Yorkshire
Re: 1/4 Scale ASK21
To some extent it's personal preference.
In practice, a larger angle requires a more forward CofG and results in a stronger stabilising moment in the longitudinal plane. The sweet spot for most glass sailplanes is around 1.5 to 2 degrees, but I have read of 0 degrees for more aerobatic types.
Hope this helps.
Rog
In practice, a larger angle requires a more forward CofG and results in a stronger stabilising moment in the longitudinal plane. The sweet spot for most glass sailplanes is around 1.5 to 2 degrees, but I have read of 0 degrees for more aerobatic types.
Hope this helps.
Rog
- jimbo
- Posts: 293
- Joined: 18 Mar 2015, 21:32
- Location: Cornwall
Re: 1/4 Scale ASK21
Good work Peter. Watching with interest, hope the mould comes out well.
- Peter Balcombe
- Posts: 1399
- Joined: 18 Mar 2015, 10:13
- Location: Clevedon, North Somerset, U.K.
Re: 1/4 Scale ASK21
Many thanks all.
A tiny bit more progress - the top of the fin has been cut to shape.
The front step is as per full size as it allows the LE to curve up to the LE of the tailplane which projects forward of the top of the fin.
The rear part Is cut to the tailplane underside profile.
Thus the tailplane will have a small block fitted to its front underside & it then bolts directly onto the top of the fin.
A tiny bit more progress - the top of the fin has been cut to shape.
The front step is as per full size as it allows the LE to curve up to the LE of the tailplane which projects forward of the top of the fin.
The rear part Is cut to the tailplane underside profile.
Thus the tailplane will have a small block fitted to its front underside & it then bolts directly onto the top of the fin.